Use of Stable Isotopes of Carbon and Nitrogen to Identify 

Sources of Organic Matter to Bed Sediments of the 

Tualatin River, Oregon 

Scientific Investigations Report 2010–5154

Prepared in cooperation with Clean Water Services

U.S. Department of the Interior

U.S. Geological Survey
Cover: Photograph of Tualatin River looking downstream from Farmington bridge, 

July 19, 2008, by Stewart Rounds, U.S. Geological Survey.

Back Cover:

Top

 Photograph of Tualatin River at Lee Falls, September 24, 2001, by Stewart Rounds, 

 U.S. Geological Survey

Middle

 Photograph of the Tualatin River near Stafford Road, September 23, 2005, 

 by Stewart Rounds, U.S. Geological Survey

Bottom

 Photograph of Rock Creek Treatment Facility, June 22, 2000, by Dennis Wentz,

 U.S. Geological Survey
Use of Stable Isotopes of Carbon and 

Nitrogen to Identify Sources of Organic 

Matter to Bed Sediments of the Tualatin 

River, Oregon

By Bernadine A. Bonn and Stewart A. Rounds

Prepared in cooperation with Clean Water Services

Scientific Investigations Report 2010–5154

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2010

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Suggested citation:

Bonn, B.A., and Rounds, S.A., 2010, Use of stable isotopes of carbon and nitrogen to identify sources of organic 

matter to bed sediments of the Tualatin River, Oregon: U.S. Geological Survey Scientific Investigations Report 2010–

5154, 58 p.
iii

Contents

Abstract...........................................................................................................................................................1

Introduction ....................................................................................................................................................1

Stable Isotopes......................................................................................................................................3

Description of Study Area ...................................................................................................................3

Purpose and Scope ..............................................................................................................................4

Methods and Procedures.............................................................................................................................4

Sample Collection.................................................................................................................................4

Sample Processing...............................................................................................................................6

Analytical Methods...............................................................................................................................7

Stable Isotope and Elemental Analysis....................................................................................7

Other Analyses.............................................................................................................................8

Statistical Methods .....................................................................................................................8

Data Aggregation and Manipulation .................................................................................................8

Acidification Correction..............................................................................................................8

Standard Deviation Adjustment ..............................................................................................10

Characterization of Bed Sediment and Source Materials....................................................................11

Bed Sediment ......................................................................................................................................11

Leaf Litter and Soil..............................................................................................................................13

Macrophytes........................................................................................................................................15

Phytoplankton and Periphyton .........................................................................................................15

Suspended Sediment .........................................................................................................................17

Potential Sources of Organic Matter to Tualatin River Sediments......................................................19

Principal Components Analysis........................................................................................................21

Summary and Conclusions.........................................................................................................................23

Acknowledgments.......................................................................................................................................23

References Cited..........................................................................................................................................23

Appendix A. Values of stable isotope compositions (δ13C, δ15N) and C/N ratios for 

samples collected from the Tualatin River basin, Oregon, including all analyzed 

split samples....................................................................................................................................35
iv

Figures

Figure 1. Map showing the Tualatin River basin in northwestern Oregon ..................... 2

Figure 2. Map showing location of sampling sites in the Tualatin River basin, Oregon ...... 5

Figure 3. Graphs showing regression results for acidified versus unacidified samples 

from the Tualatin River basin, Oregon ................................................... 9

Figure 4. Graphs showing stable isotope results and C/N ratios for bed sediment 

samples from the Tualatin River basin, showing observed ranges and outliers ... 12

Figure 5. Graph showing pairwise δ13C differences for several sampling periods 

compared to results from late-summer-1999............................................. 13

Figure 6. Graphs showing stable isotope results for potential source materials of 

sedimentary organic matter with shading showing observed ranges for 

each type of material in the Tualatin River basin, Oregon .............................. 14

Figure 7. Graphs showing comparison of δ13C, δ15N and C/N results for two size fractions of 

seston for samples from the Tualatin River basin, Oregon ........................... 15

Figure 8. Graphs showing stable isotope results for seston and periphyton samples 

from the Tualatin River basin, Oregon, with shading showing groups of 

Tualatin River samples ..................................................................... 16

Figure 9. Graphs showing relations between δ13C, δ15N, and C/N in seston samples 

from the Tualatin River, Oregon, show that high chlorophyll-a concentrations 

are associated with low δ13C, high δ15N, and low C/N ................................. 17

Figure 10. Graphs showing stable isotope results for suspended sediment samples 

from the Tualatin River basin, Oregon, with shading showing groups of 

Tualatin River samples ..................................................................... 18

Figure 11. Graphs showing δ13C, δ15N and C/N values for bed sediment and several 

types of potential source materials from the Tualatin River basin, Oregon ......... 19

Figure 12. Plots showing a comparison of δ13C, δ15N and C/N for samples of bed sediment, 

suspended sediment, and seston from the Tualatin River basin, Oregon ............ 20

Figure 13. Graphs showing δ13C, δ15N and C/N values of terrestrial materials and bed 

sediment samples from the Tualatin River basin, Oregon .............................. 20

Figure 14. Graph showing results of a principal components analysis of δ13C, δ15N, and 

C/N data for samples taken from the Tualatin River basin, Oregon .................. 22

Tables

Table 1. Summary of sample collection at each sampling site, Tualatin River basin, 

Oregon ....................................................................................... 6

Table 2. Relation between acidified and unacidified δ13C, δ15N, and C/N results for 

samples from the Tualatin River basin, Oregon .......................................... 10

Table 3. Confidence intervals of sample means for samples from the Tualatin River 

basin, Oregon .............................................................................. 10

Table 4. Ranges of δ13C and δ15N values and C/N ratios for terrestrial plant material ...... 13

Table 5. Results of principal components analysis ................................................ 21

Table 6. Mean values and confidence intervals of stable isotope compositions 

(δ13C, δ15N) and C/N ratios for samples collected in the Tualatin River basin, 

Oregon ....................................................................................... 25
v

Conversion Factors, Datum, and Abbreviations and 

Acronyms

Conversion Factors

Inch/Pound to SI

Multiply By To obtain

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

square mile (mi2) 2.590 square kilometer (km2)

ounce, fluid (fl.oz) 0.02957 liter (L)

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s)

foot per mile (ft/mi) 0.1894 meter per kilometer (m/km)

SI to Inch/Pound

Multiply By To obtain

centimeter (cm) 0.3037 inch (in.)

micrometer (μm) 0.00003937 inch (in.)

meter (m) 3.281 foot (ft)

square meter (m2) 0.0002471 acre

liter (L) 33.82 ounce, fluid (fl. oz)

gram (g) 0.03537 ounce, avoirdupois (oz)

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

°F=(1.8×°C)+32

Datum

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Abbreviations and Acronyms

DO dissolved oxygen

PC1 principal component 1

PC2 principal component 2 

PCA principal components analysis

RM river mile

SOD sediment oxygen demand

TMDL Total Maximum Daily Load

USGS U.S. Geological Survey

WWTF wastewater treatment facility
vi

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Abstract

The potential sources of organic matter to bed 

sediment of the Tualatin River in northwestern Oregon 

were investigated by comparing the isotopic fractionation 

of carbon and nitrogen and the carbon/nitrogen ratios of 

potential sources and bed sediments. Samples of bed sediment, 

suspended sediment, and seston, as well as potential source 

materials, such as soil, plant litter, duckweed, and wastewater 

treatment facility effluent particulate were collected in 

1998–2000.

Based on the isotopic data, terrestrial plants and 

soils were determined to be the most likely sources of 

organic material to Tualatin River bed sediments. The δ13C 

fractionation matched well, and although the δ15N and carbon/

nitrogen ratio of fresh plant litter did not match those of bed 

sediments, the changes expected with decomposition would 

result in a good match. The fact that the isotopic composition 

of decomposed terrestrial plant material closely resembled that 

of soils and bed sediments supports this conclusion.

Phytoplankton probably was not a major source of 

organic matter to bed sediments. Compared to the values for 

bed sediments, the δ13C values and carbon/nitrogen ratios of 

phytoplankton were too low and the δ15N values were too 

high. Decomposition would only exacerbate these differences. 

Although phytoplankton cannot be considered a major source 

of organic material to bed sediment, a few bed sediment 

samples in the lower reach of the river showed a small 

influence from phytoplankton as evidenced by lower δ13C 

values than in other bed sediment samples.

Isotopic data and carbon/nitrogen ratios for bed sediments 

generally were similar throughout the basin, supporting the 

idea of a widespread source such as terrestrial material. The 

δ15N was slightly lower in tributaries and in the upper reaches 

of the river. Higher rates of sediment oxygen demand have 

been measured in the tributaries in previous studies and 

coupled with the isotopic data may indicate the presence of 

more labile organic matter in these areas. Results from this 

study indicate that strategies to improve oxygen conditions 

in the Tualatin River are likely to be more successful if they 

target sources of soil, leaf litter, and other terrestrially derived 

organic materials to the river rather than the instream growth 

of algae.

Introduction 

Dissolved oxygen is essential to the aquatic health of 

many rivers and lakes, and the concentration of dissolved 

oxygen often is used as a water-quality standard to protect fish 

and aquatic life. The dissolved oxygen (DO) concentration in 

a waterbody is affected by many processes, such as exchange 

with the atmosphere (reaeration), photosynthesis by algae 

or aquatic plants, ammonia nitrification, respiration by algae 

and bacteria, and the bacterially mediated decomposition of 

organic matter suspended in the water column or in surficial 

sediments. The oxygen consumed through the decomposition 

of organic matter in surficial sediments is called sediment 

oxygen demand (SOD) and can be one of the most important 

loss processes for DO, particularly in shallow streams.

Low DO conditions periodically occur in the 

lower reaches of the Tualatin River and its tributaries in 

northwestern Oregon (fig. 1), especially during low-flow 

periods when the water is warm but algal photosynthesis is 

minimal. During such periods, SOD can account for a large 

fraction of the total DO consumed. The U.S. Geological 

Survey (USGS) investigated the effects of SOD in the Tualatin 

River, measured a median SOD rate of 2.3 grams of oxygen 

per square meter of sediment per day (g/m2/d) (Rounds and 

Doyle, 1997), and determined that SOD and water-column 

oxygen demand are the largest overall sinks for DO in the 

Tualatin River (Rounds and others, 1999).

In response to water-quality problems in the Tualatin 

River, Oregon’s Department of Environmental Quality in 

1988 adopted a set of Total Maximum Daily Load (TMDL) 

regulations in an effort to restore the aesthetic qualities of the 

river and protect the river against low DO concentrations and 

high pH levels. The TMDLs required substantial ammonia 

and phosphorus reductions, which were designed to increase 

DO concentrations and limit the size of algal blooms during 

the summer months. At that time, it was assumed that 

algal-derived biomass settling to the river bottom was an 

important source of decomposable organic matter, and that 

limiting the size of algal blooms would not only eliminate 

high pH levels but also decrease the SOD and increase DO 

concentrations. That assumption was challenged by later 

measurements that determined that SOD rates generally were 

Use of Stable Isotopes of Carbon and Nitrogen to Identify 

Sources of Organic Matter to Bed Sediments of the 

Tualatin River, Oregon

By Bernadine A. Bonn and Stewart A. Rounds
2 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon

not elevated in those reaches of the river that had the largest 

algae populations, except at one site in the lower river where a 

slightly higher rate might be ascribed to enhanced deposition 

of algal biomass (Rounds and Doyle, 1997). Furthermore, 

water-quality modeling by USGS showed that even if 

ammonia sources were fully controlled, the Tualatin River still 

could be subject to periodic low-DO conditions because of DO 

consumption by SOD (Rounds and others, 1999). Revision of 

the Tualatin River TMDLs in 2001 recognized the importance 

of SOD and called for significant decreases (20 percent or 

more) in the SOD rate of the river and its tributaries through 

the control of settleable organic materials (Oregon Department 

of Environmental Quality, 2001).

In order to manage and potentially reduce the effects of 

SOD, it is important to determine the sources of the organic 

matter delivered to stream sediments. Potential sources of 

such organic matter include not only algae, but aquatic plants, 

soils, terrestrial plant material, and possibly the particulate 

in effluent from wastewater treatment facilities (WWTFs). 

Many of these materials, however, may be distinguished 

from one another through measurements of the content and 

characteristics of the carbon and nitrogen present in that 

organic matter. Measurements of stable isotopes of carbon 

and nitrogen have been used for many years to investigate the 

nature and sources of organic matter in freshwater systems 

(Middelburg and Nieuwenhuize, 1998; Finlay and Kendall, 

2007).

Figure 1. Tualatin River basin in northwestern Oregon.

tac10-0486_fig01

RM

60 RM

70

RM

30

RM

40

RM

50

RM

10

RM

20

RM

0

WILLAMETTE

RIVER

RIVER

COLUMBIA

Henry

Hagg

Lake

Gales

Creek

Creek

McKay

Creek

Fanno

Creek

TUALATIN RIVER

Dairy C

S

r

coggins

Lake

Oswego

Tualatin

Sherwood

Portland

Tigard

Beaverton

Farmington

Cornelius Hillsboro Forest

Grove

TUALATIN MOUNTAINS

CHEHALEM MOUNTAINS

COAST RANGE

COLUMBIA

OREGON WASHINGTON

TILLAMOOK

YAMHILL

CLACKAMAS

MULTNOMAH

DURHAM

ROCK

CREEK

Beaverton Cr

Rock

WASHINGTON

OREGON

Study

Area

5

5

205

205

84

26

217

0 10

10

20 MILES

0 20 KILOMETERS

EXPLANATION

Base modified from U.S. Geological Survey and Metro digital data sets (1:24,000)

Projection: Oregon Lambert, North American Datum 1983

Designated Urban Growth Boundary (2001)

Basin boundary

Wastewater Treatment Facility

123°30' 123°15' 123° 122°45' 122°30'

45°

45'

45°

37'

30"

45°

30'

45°

22'

30"
Introduction 3

Stable Isotopes

An element is defined by the number of protons that it 

contains; for example, all carbon atoms contain six protons 

and all nitrogen atoms contain seven protons. Atoms of the 

same element, however, may contain different numbers of 

neutrons, which cause them to have different masses. Forms 

of the same element that have different masses are called 

isotopes; stable isotopes are forms that are not radioactive. 

Although isotopes vary in the number of neutrons that they 

contain, their chemical properties essentially are identical. 

Many elements of biological interest [carbon (C), nitrogen 

(N), oxygen (O), sulfur (S)] have different isotopic forms. The 

relative abundances of isotopes can be measured with great 

precision using a mass spectrometer, and such abundances 

have been used to study biogeochemical cycles and ecosystem 

dynamics.

The use of stable isotope abundances is based on the 

fact that different isotopes of an element participate in the 

same chemical reactions, but at slightly different rates due 

to their different masses. Lighter isotopes typically react 

at a slightly faster rate, which causes the relative isotopic 

abundance in the reactants and products to differ. This process 

is called isotopic fractionation. For example, the growth of 

algae tends to create algal biomass that contains less of the 

heavier carbon-13 isotope and more of the lighter carbon-12 

isotope. By examining the isotopic composition of potential 

source materials, it might be possible to identify the sources of 

organic matter to river bed sediments.

Description of Study Area

The Tualatin River basin is a 712 mi2 watershed in 

northwestern Oregon. Encompassing most of Washington 

County and parts of Multnomah, Clackamas, and several 

other counties, the basin includes the western part of the 

Portland metropolitan area and was home to approximately 

450,000 people at the time of this study (U.S. Census Bureau, 

2000). The river begins in the forested Coast Range mountains 

to the west, meanders through a valley bottom farmed for a 

wide variety of agricultural products, and skirts the southern 

boundary of the urban area before joining the Willamette 

River upstream (south) of Portland (fig. 1).

Five major tributaries enter the Tualatin River, each of 

which has distinct characteristics. Scoggins Creek has most of 

its drainage in the Coast Range and contains the basin’s only 

reservoir, Henry Hagg Lake, which stores water for irrigation, 

municipal use, and flow augmentation during summer. Gales 

Creek also has a significant headwater area in the Coast Range 

and primarily is forested (70 percent). Dairy Creek is located 

in the northern center of the basin and has a large area of 

agricultural land (50 percent) in its drainage. Rock and Fanno 

Creeks drain the northeastern part of the basin, and contain 

a substantial amount of urban land use (66 and 100 percent, 

respectively; data from 2001 National Land Cover Database, 

see Homer and others, 2007).

Streamflow in the Tualatin River reflects the regional 

climate, with higher flow during the winter rainy season 

(approximately November–April) and the lowest flow during 

the dry summer season (May–October). Typical peak annual 

flows are greater than 5,000 ft3/s, whereas typical summertime 

low flows are less than 200 ft3/s. Summer flows are augmented 

to improve water quality through releases from Henry Hagg 

Lake and from Barney Reservoir, a smaller storage reservoir in 

the adjacent Trask River basin to the west. Treated wastewater 

from the Rock Creek and Durham advanced WWTFs also add 

a substantial amount of flow to the river. During late summer, 

treated wastewater and reservoir releases can account for as 

much as 50 to 75 percent of the flow in the river (Tualatin 

River Flow Management Technical Committee, 2000).

The slope, width, adjacent vegetation, and substrate of 

the Tualatin River have an effect on the water quality of the 

river. In the Coast Range, the river is steep and runs over a 

bedrock substrate that includes several waterfalls. It is clear, 

cool, and well shaded, and as a result, it is well oxygenated. 

Where the river meets the valley bottom upstream of Gaston, 

its slope decreases to just more than 1 ft/mi and it begins to 

suspend fine particulate material as it meanders on valley 

sediments. The river from Gaston to river mile (RM) 30 is 

about 50 ft wide and still relatively well shaded. The lack of 

light means that few algae grow in this reach. Near RM 30, 

the river transitions to a pooled reach with a slope less than 

0.1 ft/mi and a width of about 150 ft, allowing solar radiation 

to stimulate the growth of algae. The pooled reach, with 

depths that often exceed 15 ft, is a depositional area that 

accumulates a large amount of organic-rich sediment. This 

reach extends downstream to RM 3.4 at the Oswego Dam, 

a 4-ft high concrete structure built on a shallow bedrock 

sill. During summer, the residence time in the pooled reach 

can be 10–14 days, which is sufficient time to grow a large 

population of phytoplankton (free-floating algae) and/or 

deplete a substantial amount of DO through SOD.
4 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon

Purpose and Scope

This report describes the use of carbon and nitrogen 

stable isotope measurements and carbon/nitrogen (C/N) 

ratios to identify the likely sources of organic material to 

bed sediments of the Tualatin River. In particular, the study 

addresses the following questions:

• Does bed sediment have a similar isotopic composition 

throughout the Tualatin River?

• Is the isotopic composition of bed sediment in the Tualatin 

River similar to that in the tributaries?

• What are the isotopic compositions of potential source 

materials of bed sediment?

• Based on isotopic composition, what source materials 

appear to contribute most to bed sediment, and is it likely 

that the contribution of algae is significant?

These questions are critical to the management of water 

quality in the Tualatin River basin and will help to determine 

the priority of various source-control efforts related to the 

TMDLs.

The focus of this study was on bed sediment in the lower 

Tualatin River where decomposing organic materials on the 

river bed can consume large amounts of dissolved oxygen. 

Sediment oxygen demand tends to be most important in the 

pooled reach of the river between RM 30 downstream of 

Farmington and RM 3.4 at the Oswego Dam because the slow 

travel time in this reach favors the exertion of SOD. The scope 

of the study, however, includes bed sediment samples from 

farther upstream and from Tualatin River tributaries as well 

as a wide range of potential source materials throughout the 

drainage basin. Sampled source materials included soils, leaf 

litter and detritus, plankton, aquatic plants, WWTF effluent 

particulate, and suspended sediment. To examine seasonal 

variations and assess interannual variability, samples were 

collected at different times of year between late summer of 

1998 and the summer of 2000.

Methods and Procedures

Sample Collection

A preliminary study was done in the summer of 1998 

to ascertain if stable isotope analysis might be useful in 

identifying what materials were the primary contributors 

to decomposable organic material in Tualatin River bed 

sediment. Bed sediment, suspended sediment, and seston 

(suspended particulate material, including plankton and 

organic detritus) samples were collected at two sites in the 

Tualatin River. Terrestrial materials, such as leaf litter and soil, 

also were collected from several sites.

After the preliminary study indicated that the method 

might be successful in identifying the primary sources of 

organic matter to bed sediment, a more extensive study 

was designed and completed. Bed sediment, suspended 

sediment, and seston samples were obtained at eight sites 

along the Tualatin River, near the mouths of four tributaries, 

and from Hagg Lake during four separate sampling periods 

(mid‐summer-1999, late-summer-1999, winter-2000, and

early-summer-2000). Not every site-material combination was 

collected during each sampling period. Sites were selected 

based on several factors, such as (a) location upstream or 

downstream of WWTF discharges, (b) the amount of algal 

growth that typically occurs in different river reaches, (c) the 

relative size of tributary inputs, and (d) safety considerations. 

Sites from RM 5.5 to 9.9 typically are influenced by large 

populations of algae during summer, and sites downstream of 

RM 38.1 are affected by discharges from major WWTFs (at 

RMs 38.1 and 9.3), whereas sites upstream are less affected 

by algal growth and WWTF discharges. Tributary sites with 

major contributions to the river were selected rather than 

sites in smaller tributaries. Finally, sites had to be safely 

accessible—sites that were wadeable or accessible by canoe 

were preferred for collecting bed sediment. In all, 92 samples 

were collected from July 1999 to June 2000 (fig. 2, table 1).

Potential sources to the decomposable material in bed 

sediment also were sampled. These included various types 

of organic material such as leaf litter, woody material, and 

organic detritus. Soil samples and effluent from the two major 

WWTFs were collected. A sample of bryozoans (filter-feeding 

aquatic invertebrates) also was collected. Materials were 

selected that were readily found in the basin and were either 

known to enter the stream network or could be expected to 

do so. In all, 50 samples of potential source materials were 

collected. 

Bed Sediment.—The method used to collect bed sediment 

varied depending on the site and sampling period. For the 

preliminary study (late-summer-1998), a 4.2-cm diameter 

rigid plastic tube was used by scuba divers to obtain nine 

bed sediment cores from each of two sites. Core sampling 

was not feasible for the expanded study because some sites 

were accessible only by bridge. In addition, the stratigraphic 

information provided by cores was not needed, so a simpler 

method was used beginning with the mid-summer-1999 

sampling period. At wadeable sites, bed sediment was 

collected using a stainless steel ladle to skim the top 1–2 cm 

of sediment from depositional areas. Areas close to the bank 

were avoided to reduce the contribution from nearby soil. 

Samples from at least three different depositional areas were 

obtained from each site and composited into an 8-oz glass jar. 
Methods and Procedures 5

tac10-0486_fig02

Forest

Grove

5

5

205

26

217

Tualatin

King

City

Tigard

Beaverton

PORTLAND

Farmington

Hillsboro Cornelius

Gaston

Dilley Henry

Hagg

Lake

Dairy

Creek

Creek

Rock

Creek

Beaverton

Creek

Creek Fanno

Gales

Lake

Oswego

Scoggins Creek

McKay

Creek

Bronson Creek

TUALATIN RIVERTUALATIN RIVER

123°15' 123°07'30" 123° 122°52'30" 122°45'

45°

30'

45°

22'

30"

WILLAMETTE RIVERWILLAMETTE RIVER

9

8

7

6

5 4

3 2 1

25

24 23

22

21

20

19

18

17

16

15

14

13

12

11

10

Durham

0 5

5

10 Miles

0 10 Kilometers EXPLANATION

Sampling site and map No. 1

Designated Urban Growth Boundary (2001)

Base modified from U.S. Geological Survey and Metro digital data sets (1:24,000) 

Projection: Oregon Lambert, North American Datum 1983

OREGON

Study

Area

OREGON

Study

Area

Figure 2. Location of sampling sites in the Tualatin River basin, Oregon.

At sites accessed by canoe or bridge, the same general method 

was applied to a grab sample of streambed sediment collected 

with an Ekman dredge. Obtaining an intact streambed sample 

of a depositional area was difficult at some sites. Chunks of 

wood, concrete, asphalt, and other debris frequently caught in 

the jaws of the Ekman dredge and caused any fine depositional 

material to be washed away as the apparatus was retrieved. 

Some samples consisted of only compacted clay with no 

depositional material. For these reasons, material from only 

two depositional areas was composited at the most difficult 

sites. Bed sediment sampling in the winter proved especially 

difficult because high flows caused the Ekman dredge to drift 

and become snagged on submerged debris, jeopardizing its 

retrieval. Consequently, bed sediment sampling for the winter 

period was discontinued after only two sites were sampled. 

Suspended Sediment.—Suspended sediment was 

collected using a USGS suspended sediment sampler and the 

equal‐width-increment method (Edwards and Glysson, 1999).

A DH-59 sampler attached to a cable was used for deep sites; a 

DH-81 hand sampler was used for shallow sites. A total of 4 L 

of water were collected at each site and stored in polyethylene 

bottles.

Seston.—A nylon plankton tow net with an 80-μm filter 

mesh was used to collect seston samples. The net was slowly 

towed (by canoe or by hand) in the upper 1 m of the water 

column but below the water surface. The concentrates from 

each tow were composited into glass jars until approximately 

1 L of concentrate was collected. Total towing time ranged 

from as little as 5 minutes to more than 90 minutes, depending 

on the amount of seston in the river or lake.

Other Samples.—The method used to collect other 

samples depended on the sample type. In general, aggregated 

samples (soil, duckweed mat, leaf litter) were scooped with a 

stainless steel ladle, whereas discrete samples (twigs, leaves 

or needles, periphyton) were hand picked. All samples were 

placed in glass containers. Samples of wastewater effluent 

(50 L in stainless steel milk cans) were collected by the 

operators of the WWTFs.
6 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon

Sample Processing

After collection, samples were stored at 4 oC until 

processing, which generally occurred within 48 hours. Sample 

processing differed somewhat for bulk materials (including 

bed sediment, leaf litter, and soil) versus filterable material 

(seston, suspended sediment, and WWTF effluent). 

Bulk Material.—Bulk material first was examined 

visually for extraneous material, which was removed with 

forceps; for example, wood pieces were removed from bed 

sediment samples. Some bulk material was hand sorted into 

fractions, such as cones and twigs, which were separated 

from duckweed mat. Next, the sample was frozen and then 

freeze‐dried. The resulting dehydrated material was ground

in a mill and portioned into three glass vials (called “sample 

splits”) that were sent for isotopic analysis.

Filtered Material.—Suspended sediment and solids from 

WWTF effluent were captured on 0.45-μm glass fiber filters 

that had been baked at 500 oC for 4 hours. The WWTF effluent 

was centrifuged before filtering to concentrate the solids. 

One‐half of the seston sample was filtered though a 202-μm

nylon filter to remove zooplankton and any macroscopic 

debris. The resulting seston filtrate contained phytoplankton 

as well as suspended material in the 80–202 μm size range. 

Ten mL of this fraction was removed, preserved with formalin, 

and sent for algal speciation analysis. Solids from the seston 

filtrate and the remaining unfiltered fraction were captured 

separately on 0.45-μm glass fiber filters. All sample filters 

were frozen and then freeze-dried. Each dried filter was cut 

into three approximately equal wedges that were divided 

among three glass vials (sample splits) and sent for isotopic 

analysis.

Summer 1998.—Sample processing differed for the 

preliminary study. Bed-sediment cores were frozen and 

then sectioned according to depth. The top 1, 2, or 3 cm of 

a core was used depending on the core. Bed sediment was 

not composited; rather, each core-section sample was treated 

separately. Core sections and other bulk materials were dried 

Map 

No.

Site name Access

Late-summer

1998

Mid-summer

1999

Late-summer

1999

Winter

2000

Early-summer

2000 Other

BS SS Ses BS SS Ses BS SS Ses BS SS Ses BS SS Ses

Mainstem sites

1 Tualatin River at RM 5.5 (Stafford Road) C, B

2 Tualatin River at RM 8.7 (Boones Ferry Bridge) C

3 Tualatin River at RM 9.4 (Basalt sill) C

4 Tualatin River at RM 9.9 (Cook Park) C

5 Tualatin River at RM 16.2 (Elsner Bridge) B

6 Tualatin River at RM 20.3 C

7 Tualatin River at RM 24.5 T

8 Tualatin River at RM 26.9 (Scholls) C, B

9 Tualatin River at RM 38.4 (Rood Bridge) C, B

10 Tualatin River at RM 58.8 (Dilley) W, B

11 Tualatin River at RM 67.8 (Cherry Grove) T

Tributary sites

12 Fanno Creek at Durham Road B

13 Fanno Creek at Durham City Park W

14 Rock Creek at Highway 8 W, B

15 Dairy Creek at Highway 8 W, B

16 Gales Creek at old Highway 47 W, B

17 Henry Hagg Lake C

Other sites

18 Durham Wastewater Treatment Facility O

19 Onion Flat (Cipole Road and Highway 99W) T

20 Tualatin Nature Park T

21 Oregon Graduate Institute (near Bronson Creek) T

22 Rock Creek Wastewater Treatment Facility O

23 Jackson Bottom (between Miller Swale and holding pond) T

24 Zurcher Farm (Fernhill Road near Tualatin River) T

25 Patton Valley Road (north side, 1 mi east of Cherry Grove) T

Table 1. Summary of sample collection at each sampling site, Tualatin River basin, Oregon.

[Location of map No. is shown in figure 2. Gray shading indicates collection of sample. BS, bed sediment; SS, suspended sediment; Ses, seston. Access: C, 

canoe; B, Bridge; W, wading; T, terrestrial; O, other. RM, river mile]
Methods and Procedures 7

at 45 or 57 oC, then ground in a mill and divided into vials. 

Bulk materials (other than core sections) were split into three 

glass vials (sample splits). Samples requiring filtration were 

treated the same as just described for samples collected after 

1998, except that the filters were dried at 45 or 57 oC. Filters 

were cut into three sections which were divided among vials 

(sample splits).

Analytical Methods

Stable Isotope and Elemental Analysis

Sample splits were analyzed for carbon and nitrogen 

isotopic and elemental composition by Dr. Carol Kendall’s 

laboratory at the USGS facility in Menlo Park, California. 

Their method will be summarized here; for a detailed 

description, see Kendall and others (2001). Bulk sample splits 

were subsampled as received. Sample splits on filters were 

scraped into a dish and then ground before subsampling. 

Approximately 2 mg subsamples were used for highly organic 

samples (seston and plant material) and 18–25 mg subsamples 

were used for samples that contained less organic matter (bed 

and suspended sediment and WWTF effluent). Following 

their standard protocols, the subsamples were vapor acidified 

to remove carbonate and then analyzed using a Carlo Erba®

elemental analyzer attached to a Micromass Optima mass 

spectrometer.

Carbon and nitrogen isotopic compositions generally are 

expressed as a δ value in units of per mil (parts per thousand). 

A δ value is calculated relative to standards, carbon in PeeDee 

belemnite (PDB) and nitrogen in air (see equation 1). A 

substance with a higher δ value contains relatively more of the 

heavier isotope (13C or 15N) and relatively less of the lighter 

isotope (12C or 14N) than a substance with a lower δ value. The 

changes in percent composition are very small—a 1 per mil 

change corresponds to a 0.0011 and 0.0004 percent change in 

isotope composition for δ13C and δ15N, respectively.

Carbon and nitrogen content was measured for all 

samples. For samples collected on filters, however, an 

unknown amount of glass fiber was included when the filter 

was scraped, thus making the percent carbon and percent 

nitrogen values individually meaningless. The C/N ratio, 

however, is valid and that is the value reported here as an 

atomic ratio.

Quality Assurance.—Dr. Kendall’s laboratory routinely 

analyzes approximately 10 percent of samples in duplicate 

and analyzes additional splits if results are not within their 

expected reproducibility. About 15 percent of the analyses 

for this study were laboratory splits (“lab splits”). As 

described, all Tualatin River basin samples (except the 1998 

core sections) were submitted to the laboratory as triplicate 

sample splits. The variance of lab splits was not significantly 

different from the variance of sample splits (α=0.05, F-test). If 

the sample material had not been homogeneous before being 

divided into triplicate splits, the pooled variance of the sample 

splits would have exceeded that of the lab splits. The fact that 

the variances are not different is an indication that all splits 

(sample and lab) were equivalent. Therefore, lab split and 

sample split results were treated identically.

Some of the Tualatin River basin sample results, 

especially for bed sediment and suspended sediment samples, 

had poorer than expected reproducibility for δ15N. Laboratory 

results indicated that these samples typically contained little 

nitrogen, less than 1 micromole (14 μg). Nitrogen content was 

low enough in some cases that it was near the detection limit 

of the analytical instrument, causing the measurement to have 

only one significant digit. This resulted in higher variability 

among C/N ratios for the sample.

After the first sets of samples from the Tualatin River 

basin had been analyzed, it was evident that acidification was 

affecting δ15N, but not δ13C, which was exactly the opposite 

of the desired effect. Samples typically are acidified to prevent 

carbonate from affecting the δ13C of the organic carbon in 

the sample, and the acidification should not alter the δ15N. 

Evidently, samples from the Tualatin River basin contained 

little carbonate and particularly labile nitrogen (C. Kendall, 

written commun., February 25, 1999). For a number of 

subsequent samples, both acidified and unacidified subsamples 

were analyzed. These results confirmed the previous 

observations. Only unacidified subsamples were analyzed 

for the last sampling period (early-summer-2000). The 

inconsistency in acidification procedures resulted in data that 

were not necessarily comparable. For about 50 percent of the 

samples, all subsamples were acidified before analyses. For 

about 30 percent of the samples, no subsamples were acidified. 

The remaining samples had some, but not all subsamples, 

acidified before analysis. Making these data compatible with 

each other required devising a method to remove the artifact 

associated with acidification; this method is described later in 

this report (see section, “Acidification Correction”).

13 15

12 14

13 15

13 15

12 14

C N

C N

C 1 1000 N 1 1000

C N

C N

sample sample

PDB Air

                    δ =  − × δ =   − ×                          

(1)
8 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon

Other Analyses

Algal speciation and enumeration was performed 

by Aquatic Analysts (Friday Harbor, Washington) on 

formalin‐preserved samples by microscopic examination and

counting at least 500 colonies. Chlorophyll-a concentrations 

in river water were measured by the Clean Water Services 

Water-Quality Laboratory (Hillsboro, Oregon) as part of a 

routine monitoring program. Samples were collected weekly; 

interpolation was used for dates that did not coincide with a 

routine sampling date. Clean Water Services participates in a 

quality assurance program for chlorophyll-a analysis with the 

USGS Oregon Water Science Center.

Statistical Methods

Several statistical methods were used in this study. 

Parametric methods (ordinary least squares, linear regression, 

mean, standard deviation, and Student’s t-test) were used to 

evaluate results of sample splits, which can be expected to be 

normally distributed. For comparisons among sample results, 

non-parametric methods were used, including analysis of 

variance on ranked data, Mann-Whitney U test, and Spearman 

rank-order regression (Miller and Miller, 1988; SAS Institute 

Inc., 1989; Helsel and Hirsch, 1992). A criterion of α=0.05 

was used for statistical significance unless otherwise noted. 

Principal components analysis was performed on normalized 

data (SAS Institute Inc., 1989). 

Data Aggregation and Manipulation

Triplicate sample splits were submitted for almost 

all samples, with the intent to calculate a mean value and 

confidence limits for each sample. Two inconsistencies 

related to changes in methods of sample collection and 

analytical procedures resulted in data that were not necessarily 

compatible among splits and could complicate comparisons 

among samples. Specifically,

• In the 1998 preliminary study, core sections of bed 

sediment were submitted separately; after 1998, bed 

sediment samples were submitted as triplicate sample 

splits of homogenized composites of surficial sediment.

• Acidification of samples prior to analysis was not 

consistent and appeared to affect results for nitrogen.

The following protocol was devised to produce a final dataset 

that was as internally consistent as possible.

1. If a split (sample or lab) was acidified, the δ15N and C/N 

results were “corrected” using a linear relation described in 

section, “Acidification Correction.” This correction should 

make all δ15N and C/N results comparable and equivalent 

to “unacidified.” No correction was needed for δ13C.

2. With the exception of the 1998 bed sediment samples, 

the mean and standard deviation were calculated from 

the combined results of sample splits and lab splits for 

each sample. This approach is valid because the sample 

split variance and lab split variance were not significantly 

different. 

3. For 1998 bed sediment samples, lab splits were done for 

some core-section samples but not for others. Sample splits 

were not done for these samples, and it cannot be assumed 

that one core section was the same as another core section. 

Consequently, a weighted technique was used to calculate 

the mean and standard deviation, giving the same total 

weight to each core-section sample.

4. The standard deviation was adjusted for δ15N and C/N 

averages that were calculated from only acidified results. 

In this case, the variability associated with the acidifiedunacidified correction equation was incorporated. Details 

of this adjustment are discussed in section, “Standard 

Deviation Adjustment.”

Acidification Correction

Laboratory personnel judged that acidified splits 

produced the most reliable results for δ13C and percent 

carbon, and that unacidified splits were better for δ15N and 

percent nitrogen. Because acidified and unacidified splits 

were not analyzed for every sample, it was necessary to 

devise a correction factor for acidification. Data from the 

32 samples having both acidified and unacidified results 

were examined. The mean value was used when multiple 

lab or sample splits had been analyzed, otherwise discrete 

values were used. Analysis of acidified versus unacidified 

data regressions (fig. 3) showed that the δ13C regression line 

was not significantly different from the y=x line, but the 

δ15N and C/N regressions were significantly different from 

the y=x line (α=0.05). These results confirmed previous 

observations: acidification did not significantly affect δ13C, but 

systematically decreased δ15N. Acidification increased C/N 

slightly, which is consistent with the hypothesis that some of 

the nitrogen was labile. 

Data shown in figure 3 represent samples of bed 

sediment, suspended sediment, seston, plant material, and 

WWTF effluent solids. When the effect of acidification on 

δ15N was first observed, it was thought to be limited to the 

sediment samples. Treating sediment samples separately 

from the others, however, showed similar regression statistics 

between acidified and unacidified results; therefore, all types 

of samples were included.

Regression equations were applied to all acidified 

results for δ15N and C/N, correcting them to the equivalent 

of unacidified results (table 2). No correction was applied to 

δ13C results because the regression line was not significantly 

different from y=x.
Methods and Procedures 9

tac10-0486_fig03

12

10

8

6

4

2

0

0 2 4 6 8 10 12

-20

-24

-28

-32

-36

-40

-40 -36 -32 -28 -24 -20

50

40

30

20

10

0

0 10 20 30 40 50

C/N atomic ratio (unacidified sample)

C/N atomic ratio (acidified sample)

EXPLANATION

Regression line

95% confidence limit of regression line

95% prediction limit of regression

y=x line (1-to-1 line)

δ15N (Unacidified sample), in per mil

δ15N (Acidified sample), in per mil δ13C (Acidified sample), in per mil

δ13C (Unacidified sample), in per mil

Figure 3. Regression results for acidified versus unacidified samples from the Tualatin River basin, Oregon. Regression for 

δ13C is not significantly different from the y=x line. Regressions for δ15N and the C/N atomic ratio are significantly different 

from the y =x line (α= 0.05).
10 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon

( )

( )

( )

( ) ( ) ( )( )

2 2

2 2

2

2

2 2

1 1 1

1 var( ) ,

where

2

and and

is the number of points in the regression line, and

, points are unacidifi

e o

o

xx

xx yy xy

e

xx

n n n

xx i yy i xy i i

i i i

s n y y

x

slope slope S n

S S S

s

n n S

S n x x S n y y S n x x y y

n

x y

= = =

 − 

= +      

− = −

= − ∑ = − ∑ = − − ∑

ed values and acidified values, respectively.

(2)

Confidence intervals of the sample means provide guidance for interpreting differences; these intervals were calculated 

using a two-tailed Student’s t-test at the 95-percent level. The mean 95-percent confidence limits are shown in table 3.

Table 2. Relation between acidified and unacidified δ13C, δ15N, and C/N results for samples from the Tualatin River basin, Oregon.

[Abbreviations: r2, square of the Pearson correlation coefficient; N, number of points in regression]

Parameter

Regression statistics Significantly 

different from y=x? 

(α=0.05)

Correction equation

r

2 Standard 

error

N

δ13C 0.95 0.588 32 No None

δ15N 0.95 0.487 32 Yes Unacidified = (Acidified + 0.3675) / 0.9385

C/N 0.96 1.360 32 Yes Unacidified = (Acidified – 0.8405) / 1.0131

Table 3. Confidence intervals of sample means for samples from the Tualatin River basin, 

Oregon.

Mean 95-percent confidence interval (number of samples)

δ13C δ15N C/N atomic ratio

All splits acidified ± 0.32 (55) ± 0.44 (55) ± 1.7 (55)

All splits unacidified ± 0.33 (90) ± 0.79 (89) ± 2.3 (90)

Mixed acidification ± 0.53 (32) ± 0.74 (32) ± 1.2 (32)

Standard Deviation Adjustment

As previously described, the mean and standard deviation 

of all splits was calculated for each sample (a weighted 

method was used for bed-sediment core sections) after δ15N 

and C/N values were corrected for the effects of acidification. 

For δ15N and C/N results in the case where all splits were 

acidified, the calculated standard deviation underestimates the 

potential variability because it does not include the variability 

associated with the acidification correction regression. To 

remedy this situation, additional variance was added to the 

variance for the acidified samples:
Characterization of Bed Sediment and Source Materials 11

Characterization of Bed Sediment and 

Source Materials

Isotopic results for δ13C and δ15N as well as the C/N 

ratios for each sample are shown in table 6 (at back of report). 

The full datasets are shown in appendix A.

Bed Sediment

δ13C.—The δ13C of bed sediment for Tualatin River basin 

samples generally is between -29.4 and -26.9 per mil (fig. 4). 

No general trend with river mile was evident, although the 

lowest values of δ13C in the river tended to occur at RM 9.9. 

Among the tributaries, δ13C values for the Rock and Fanno 

Creek sites were lower than those for either the Gales or Dairy 

Creek sites. There were no statistically significant differences 

between tributary and river sites; however, the Rock and 

Fanno Creek results more closely resembled Tualatin River 

results from RM 8.7–9.9, whereas the Gales and Dairy Creek 

results were more similar to results from most upstream river 

sites. 

The δ13C results for the late-summer-1999 samples were 

lower than those obtained at any other time. The lowest δ13C 

value measured for bed sediment, -30.6 per mil, was obtained 

during this sampling period. Median differences for pairwise 

site-matched comparisons between late-summer-1999 results 

and those from mid-summer-1999 and early-summer-2000 

were -1.9 and -1.4 per mil, respectively, which were 

statistically different from zero (α=0.05, fig. 5). Statistical 

tests for differences with late-summer-1998 and with 

winter-2000 were not possible because the number of samples 

was too small.

Pairwise site-matched comparisons also showed 

that δ13C for mid-summer-1999 was greater than δ13C for 

early‐summer-2000. Because the difference was consistent

among all samples (river and tributaries), it was highly 

significant (p<0.001), but it also was small (0.7 per mil). 

Although this difference may reflect a real seasonal effect 

(such as differences in source material), it is possible that this 

is a spurious correlation or an artifact related to laboratory 

performance that changed over time.

δ15N.—The δ15N of bed sediment for Tualatin River basin 

samples generally is between 1.7 and 6.3 per mil (fig. 4). No 

trends related to season or sampling period were observed. 

Inspection of the δ15N results shows that the data divide 

neatly into two groups: Group A comprising lower river sites 

at and downstream of RM 26.9 plus the Rock Creek site, 

and Group B including river sites upstream of RM 26.9 plus 

the Gales, Dairy and Fanno Creek sites (fig. 4). The δ15N of 

Group A generally is between 4.9 and 6.3 per mil, whereas the 

δ15N of Group B generally is between 1.7 and 4.9 per mil. The 

difference in δ15N values between these groups is statistically 

significant. Two possibilities that could account for this 

difference are decomposition and WWTF effects. Increases 

in δ15N values of several per mil have been observed to occur 

with progressive decomposition (Bernasconi and others, 1997; 

Kendall and others, 2001). If the degree of decomposition 

explains the difference between Groups A and B, it could 

indicate that the sediments in the tributary and upper river 

sites were “fresher” than materials found in the lower river. 

This explanation is consistent with observed differences 

in measured SOD rates, which were statistically higher at 

tributary sites than at Tualatin River sites (Rounds and Doyle, 

1997). Alternatively, if the dissolved nitrogen discharged 

from the WWTFs tends to be heavier (higher δ15N), then it is 

possible that vegetation in the riparian corridor downstream of 

the Rock Creek WWTF (RM 38.1) also might have a heavier 

nitrogen content. Transport of leaf litter with a higher δ15N 

from the near riparian area might help explain the higher δ15N 

of the bed sediment samples collected at and downstream of 

RM 26.9. Neither of these hypotheses, however, can be tested 

with the available data. 

The δ15N results from late-summer-1998 bed sediment 

samples should be regarded with some skepticism. These 

samples were collected and processed using a different method 

than the other samples (cores versus surficial sediment grab 

samples, and drying at about 50 oC versus freeze drying). It 

is not known if these collection and processing differences 

affected the results, but it would not be unreasonable to 

suspect that the higher temperature drying method caused 

additional nitrogen fractionation. Laboratory personnel 

remarked that the nitrogen in Tualatin River bed sediment 

samples was particularly labile. Because of the processing 

difference, these samples were omitted from further analysis.

C/N ratio.—The C/N atomic ratio of bed sediment 

samples from the Tualatin River basin generally falls within a 

narrow range of 12.5–17.7 (fig. 4). No trends related to river 

mile or sampling period were observed with the exception 

of the two winter-2000 samples which had much higher C/N 

ratios. Both samples from winter-2000 contained woody 

debris and although the larger pieces were removed from 

the samples during processing, it is likely that some wood 

remained in the sample at the time of analysis. Because of this 

confounding variable and the general lack of winter samples, 

it is impossible to draw conclusions about C/N ratios in bed 

sediment during the winter season. Two samples obtained in 

early-summer-2000 had particularly low C/N ratios which 

cannot be attributed to any known cause.
12 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon

tac10-0486_fig04

Gales

Dairy

Rock

Fanno

Fanno*

TR-58.8

TR-38.4

TR-26.9

TR-20.3

TR-16.2

TR-9.9

TR-8.7

TR-5.5

TR-38.4

TR-26.9

TR-20.3

TR-16.2

TR-9.9

TR-5.5

TR-20.3*

TR-26.9

TR-16.2

Gales

Dairy

Rock

Fanno

TR-58.8

TR-38.4

TR-26.9

TR-20.3

TR-16.2

TR-9.9

TR-8.7

TR-5.5

Mid-Summer-99 Late-Summer-99 Winter-00 Early-Summer-00

Bed sediment

L-Su-98

TR-26.9

TR-5.5

-32 -31 -30 -29 -28 -27 -26 1 2 3 4 5 6 7 8 9 5 10 15 20 25 30 35

δ13C, in per mil δ15N, in per mil C/N atomic ratio

EXPLANATION

Mean value at dot with line showing 

95% confidence interval of mean— 

Open and filled dots divide δ15N data 

into two groups

Outlier—outside 1.5x 

interquartile range

5th–95th percentile of means 

represented by filled dots 

Minimum–maximum of means 

represented by open dots

Figure 4. Stable isotope results and C/N ratios for bed sediment samples from the Tualatin River basin, showing 

observed ranges (shaded areas) and outliers (circled values). Lower river and Rock Creek δ15N values (filled 

dots) are greater than those for upper river and tributary sites (open dots). [Abbreviations: L-Su=late summer, 

TR= Tualatin River, number following TR=river mile location, * =sample that included deeper anoxic sediment in 

addition to surficial sediment].
Characterization of Bed Sediment and Source Materials 13

Leaf Litter and Soil

Coniferous litter, deciduous litter, and woody litter show 

similar values of δ13C, δ15N, and C/N ratios (fig. 6). The only 

statistically significant difference among these sample data 

is that δ15N is slightly higher for woody material than for 

coniferous litter. Different plants utilize different biochemical 

pathways during photosynthesis, and the pathway affects 

the isotopic composition. The ranges of δ13C, δ15N, and C/N 

values measured in this study are similar to those reported 

elsewhere for plants that use the C3 pathway of CO2 uptake 

(table 4). Vegetation in the riparian areas of the Tualatin 

Basin is almost exclusively trees and shrubs that utilize the 

C3 pathway, rather than plants that use the C4 pathway (corn, 

bamboo and tropical grasses) or the CAM pathway (cacti and 

desert plants). 

The range for C/N is wide, with the highest values 

associated with cones, seed pods and woody material. Wide 

ranges of C/N are not uncommon for terrestrial material in 

various stages of decay (Kendall and others, 2001).

As materials decompose, the carbon and nitrogen content 

both decrease. The rates of decay are such that the C/N ratio 

generally decreases as the material becomes progressively 

more decomposed (Middelburg and Nieuwenhuize, 1998; 

Kendall and others, 2001). In addition, δ15N tends to shift 

toward higher values as the lighter isotopes are removed 

during decomposition (Bernasconi and others, 1997; 

Middelburg and Nieuwenhuize, 1998; Kendall and others, 

2001). Reported changes in δ13C with decomposition, 

however, show less agreement. Middelburg and Nieuwenhuize 

(1998) reported that the δ13C was 2-3 per mil lower for more 

degraded material, but Kendall and others (2001) reported 

that δ13C usually increased with decomposition, although the 

changes were small. 

Two samples of decomposed terrestrial detritus were 

compared to plant litter in this study. Because only two 

samples of decomposed terrestrial detritus were collected and 

the same material was not tracked through the decomposition 

process, caution in interpretation is warranted. The δ13C values 

for detritus are within the range for plant litter, suggesting that 

δ13C changed little during decomposition for these samples. 

The detrital δ15N values, however, are at the high end of the 

range for litter, suggesting that some fractionation of nitrogen 

might have occurred during decomposition. Furthermore, the 

C/N ratios for the detritus samples are at the low end of the 

range for litter, supporting the hypothesis that the C/N ratio 

decreases with increasing decomposition.

Soils collected in the Tualatin River basin resemble plant 

litter for δ13C and δ15N, but have lower C/N values that are 

similar to those of the decomposed terrestrial detritus (fig. 6). 

This change in C/N ratio is what would be expected as soil 

organic matter derived from plant material ages and becomes 

more decomposed.

tac10-0486_fig05

0.5

0.0

-0.5

-1.0

-1.5

-2.5

-2.0

Tualatin River Mile

Bed sediment δ13C difference, in per mil

40 35 30 25 20 15 10 5 0

L-Su-99 - M-Su-99

L-Su-99 - E-Su-00

L-Su-99 - W-00

L-Su-99 - L-Su-98

EXPLANATION

Figure 5. Pairwise δ13C differences for several 

sampling periods compared to results from latesummer-1999. [L-Su =late-summer, E-Su=early-summer, 

M-Su=mid-summer, W=winter].

Table 4. Ranges of δ13C and δ15N values and C/N ratios for terrestrial plant material.

Source δ13C

(per mil)

δ15N

(per mil)

C/N

(atomic ratio) 

This study -30.4 to -21.1 -3.0 to 5.4 20 to 111

Typical reported range1 -32 to -22 -10 to 10 15 to >50

1

Typical reported range for vascular plants (C3 pathway) from Finlay and Kendall (2007).
14 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon

tac10-0486_fig06

A

A

A

B

BC

C C

C

B

B

A

AB

Coniferous Litter Deciduous Litter Detritus Soil

WR Cedar litter (needles) Oct-98

WR Cedar litter (mixed) Aug-99

Douglas Fir litter (mixed) Aug-99

Cones from duckweed mat (TR-20.3) July-99

Cones from duckweed mat (TR-9.9) July-99

Alder leaf litter Oct-98

Oregon Ash leaf litter (JB) Oct-98

Oregon Ash leaf litter (JB) Aug-99

Oregon Ash leaf litter (Fanno) July-99

Oregon Ash leaves in stream (TR-20.3) July-99

Oregon Ash leaves in stream (Fanno) July-99

Oregon Ash seed pod July-99

Oregon Ash seed pod in stream July-99

Redtwig Dogwood leaves in stream July-99

Douglas Fir twigs Oct-98

Twigs from DW mat (TR-16.2) July-99

Twigs from DW mat (TR-9.9) July-99

Twigs from bed sed sample (TR-16.2) July-99

Decomposed non-woody detritus May-00

Chehalis soil (JB) Oct-98

Chehalis soil (JB) Aug-99

Decomposed mixed detritus July-99

Woodburn soil (OGI) Oct-98

Agricultural field soil (Onion Flat) July-99

Eroded stream bank, bottom (TR-9.9) July-99

Sorted duckweed (TR-24.5) Sept-98

Sorted duckweed (TR-20.3) July-99

Sorted duckweed (TR-26.9) July-99

Sorted duckweed (TR-9.9) July-99

Unsorted duckweed mat (TR-9.9) July-99

Decomposed duckweed mat (TR-9.9) July-99

Grass in stream (Dairy) May-00

RC-WWTF Oct-98

RC-WWTF June-00

Dur-WWTF June-00

Bryozoan Aug-98

Douglas Fir litter (needles) Oct-98

Twigs from DW mat (TR-26.9) July-99

Wapato soil (Zurcher Farm) Oct-98

Eroded stream bank, A-horizon (TR-9.9) July-99

Dur-WWTF July-99

RC-WWTF July-99

Woody Litter Macrophytes

Terrestrial Aquatic

WWTF Effluent 

Particulate

δ13C, in per mil δ15N, in per mil C/N atomic ratio

-36 -34 -32 -30 -28 -26 -24 -4 0 4 8 12 16 20 0 20 40 60 80 100 120

AB Tukey grouping

EXPLANATION

Mean value at dot with line showing 95% 

confidence interval of mean

Minimum-maximum of means

Figure 6. Stable isotope results for potential source materials of sedimentary organic matter with shading showing observed ranges 

for each type of material in the Tualatin River basin, Oregon. Groups with statistically significant differences (α=0.05) are denoted with 

different letters (Tukey Grouping). No significant differences were found among the groups for δ13C. [Abbreviations: WR=Western Red, 

TR=Tualatin River, number following TR=river mile location, JB=Jackson Bottom, DW=duckweed, OGI =Oregon Graduate Institute, 

RC=Rock Creek, Dur =Durham, WWTF=Wastewater Treatment Facility].
Characterization of Bed Sediment and Source Materials 15

Macrophytes

Duckweed is a common macrophyte in the Tualatin 

River. Duckweed mats on the order of 1 m2 or larger are not 

unusual during low flow in the summer, particularly where 

they collect on the upstream side of a stationary floating 

object such as a log. In addition to duckweed, these mats 

collect small cones and twigs. Compared to terrestrial plant 

litter, sorted duckweed (only duckweed leaves and roots) had 

slightly lower δ13C (-29.8 to -28.5 per mil), higher δ15N (6.8 to 

10.5 per mil), and lower C/N (11.2 to 14.6) values (fig. 6); the 

differences for δ15N and C/N were statistically significant. The 

δ13C is less than typical values reported in the literature for 

aquatic macrophytes (-27 to -20 per mil; Finlay and Kendall, 

2007). The C/N range is particularly narrow for duckweed 

compared to terrestrial plant litter. Compared to sorted 

duckweed, the unsorted material had δ15N and C/N values 

closer to leaf litter, showing the influence of cones and twigs. 

The decomposed duckweed sample had values similar to the 

unsorted material.

Two large WWTFs discharge treated municipal effluent 

into the Tualatin River at RMs 38.1 and 9.3. The δ13C values 

for effluent particulate (>0.45 μm) are similar to those for 

terrestrial plant litter and soils (fig. 6). The δ15N values are 

significantly greater than those measured for the terrestrial 

plants or soils that were sampled. δ15N results for sorted 

duckweed and WWTF effluent particulate samples are similar 

(7.2 to 11.6 per mil). This similarity may be a coincidence, but 

it is not unreasonable to conclude that duckweed downstream 

of RM 38.1 obtain a substantial amount of nitrogen from 

WWTF effluent. Bioavailable nitrogen is in abundant 

supply due to the WWTF discharges, and uptake in such 

circumstances typically does not alter the isotopic composition 

of the nitrogen source (Finlay and Kendall, 2007). Because 

only WWTF effluent particulate were analyzed in this study, 

it is not known if the δ15N of dissolved nitrogen in effluent is 

similar. Compared to other sources, the C/N values for effluent 

particulate are very low (5.3 to 8.0).

Phytoplankton and Periphyton

The reservoir reach (RM 30–3.4) of the Tualatin River 

is known for algal production. Because of the river depth and 

turbidity in this reach, little light reaches the river bottom 

except at the edges. As a result, most algae in this reach are 

phytoplankton (free-floating algae); however, periphyton 

(attached algae) are common at a few riffle sections. To 

sample phytoplankton, seston samples were collected during 

the summer from RMs 26.9 to 5.5. As previously described 

in the Sample Processing section, two size fractions were 

prepared. Figure 7 shows that the δ13C, δ15N, and C/N values 

for the two size fractions of seston (>80 μm and 80–202 μm) 

are nearly identical, indicating that the presence of 

zooplankton or macroscopic debris in the >80 μm sample did 

not have a significant effect. Only results for the 80–202 μm 

size fraction are included in subsequent data analyses.

tac10-0486_fig07

-24

-26

-28

-30

-32

-34

-36

-38

-40

Regression line

EXPLANATION

y=x line (1-to-1 line)

Seston (80-202 μm) δ13C, in per mil

Seston (>80 μm) δ13C, in per mil

-40 -38 -36 -34 -32 -30 -28 -26 -24

18

16

14

6

4

2

0

10

12

8

0 2 4 6 8 10 12 14 16 18

Seston (80-202 μm) δ15N, in per mil

Seston (>80 μm) δ15N, in per mil

20

16

12

8

18

14

10

6

4

4 6 8 10 12 14 16 18 20

Seston (80-202 μm) C/N atomic ratio

Seston (>80 μm) C/N atomic ratio

Figure 7. Comparison of δ13C, δ15N and C/N results for 

two size fractions of seston (80–202 μm and >80 μm) for 

samples from the Tualatin River basin, Oregon.
16 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon

Seston samples showed distinctive and statistically 

significant (α=0.05) trends with river mile for δ13C, δ15N and 

C/N (fig. 8). The δ13C decreased from an average of -28.8 per 

Mid-Summer-99 Early-Summer-00 M-Su-99 E-Su-00 Late-Summer-99 L-Su-99

Hagg

Fanno

TR-20.3

TR-16.2

TR-9.9

TR-8.7

TR-5.5

Hagg

TR-26.9

TR-20.3

TR-16.2

TR-9.9

TR-5.5

TR-26.9

TR-20.3

TR-16.2

TR-9.9

TR-8.7

TR-5.5

Fanno

TR-9.4

TR-5.5

TR-9.4

Rock

TR-9.4

TR-26.9

Hagg

TR-5.5

TR-20.3

L-Su-98

δ13C, in per mil δ15N, in per mil C/N atomic ratio

-44 -40 -36 -32 -28 -24 -20 -16 0 4 8 12 16 20 0 4 8 12 16 20 0 8 16 24 32 40

Chlorophyll-a,

in micrograms per liter

Seston Periphyton

EXPLANATION

Mean value at dot with line showing 95% Measured or interpolated value

confidence interval of mean

Data and Spearman coefficient (ρ) for 

ρ correlation with river mile (α=0.05) =0.9

ρ=0.8 ρ=-0.7 ρ=0.9

ρ=1.0 ρ=-1.0 ρ=1.0

ρ=1.0 ρ=-0.8 ρ=0.9

unknown species

unknown species

Cladophera

Cladophera

Cladophera

Cladophera

unknown species

Spirogyra

Figure 8. Stable isotope results for seston (80-202 μm) and periphyton samples from the Tualatin River basin, Oregon, with shading 

showing groups of Tualatin River samples. [TR=Tualatin River, number following TR=river mile location, L-Su =late-summer, 

M-Su=mid-summer, E-Su= early-summer].

mil at RM 26.9 to an average of -38.0 per mil at RM 5.5. 

Similarly, C/N values decreased from 16.5 to 6.1. The δ15N 

showed a similarly strong, but opposite trend; the average 
Characterization of Bed Sediment and Source Materials 17

tac10-0486_fig09

TR-26.9

TR-20.3

TR-16.2

TR-9.9

TR-8.7

TR-5.5

24.0

20.2

34.2

20.3

16.3

19.8

2.5

6.7

4.4 12.1

18.7

20.3 Chlorophyll-a (μg/L)

24.0

20.2

34.2

20.3

16.3

19.8

2.5

6.7

4.4

12.1 18.7

20

8

4

12

16

10

6

14

18

EXPLANATION

Seston C/N atomic ratio Seston δ15N, in per mil

Seston δ13C, in per mil

20

4

8

16

12

18

6

14

10

-40 -38 -36 -34 -32 -30 -28

Figure 9. Relations between δ13C, δ15N, and C/N in seston 

samples from the Tualatin River, Oregon, show that high 

chlorophyll-a concentrations are associated with low δ13C, high 

δ15N, and low C/N. [TR=Tualatin River, number following TR=

river mile location].

δ15N increased from 5.8 to 13.4 per mil. These changes reflect 

the increasing presence of phytoplankton in the lower (more 

downstream) reaches of the river as evidenced by increasing 

chlorophyll-a concentrations. Samples that contain moderate 

to large amounts of phytoplankton (>15 μg/L chlorophyll-a), 

therefore, are characterized by low δ13C (< -32 per mil), high 

δ15N (>8 per mil) and low C/N (<12). These effects of location 

and chlorophyll-a level are clearly evident when the δ15N 

and C/N are plotted against δ13C in figure 9 with annotations 

showing the chlorophyll-a concentrations.

Hagg Lake seston showed a pattern that was different 

from seston in the Tualatin River (fig. 8). Visual examination 

of all Hagg Lake seston samples showed appreciable amounts 

of phytoplankton. The C/N ratios of these samples are similar 

to the samples from the lower river that contain the most 

phytoplankton, but the δ13C and δ15N values indicated much 

less fractionation. The low concentrations of nutrients in 

Hagg Lake compared to the lower Tualatin River may account 

for the differences between the seston samples from these 

locations. Algae have been reported to exhibit less isotopic 

fractionation when carbon and nitrogen are in short supply 

relative to the algal growth rate (Finlay and Kendall, 2007). 

Periphyton samples from this study show a wide 

range of δ13C, δ15N, and C/N values (fig. 8). Although δ13C 

values for most periphyton samples are similar to those 

for phytoplankton-rich seston (<-32 per mil), two samples 

(one‐quarter of the total) had anomalously high δ13C values

(near -18 per mil). No other samples collected during 

this study had δ13C values that high. The δ15N values for 

periphyton generally were less than those for seston samples 

with high levels of chlorophyll-a (<8 per mil compared to 

>8 per mil); the C/N values for phytoplankton-rich seston and 

periphyton were similar (<12).

Suspended Sediment

Suspended sediment samples show trends with river mile 

that resemble those of seston samples, but the trends are not as 

robust: δ13C and C/N decrease with increasing river mile and 

δ15N increases (fig. 10). Suspended sediment samples with low 

δ13C (<-32 per mil), high δ15N (>7 per mil) and low C/N (<10) 

were from the same sections of the river where phytoplankton 

were most prevalent. This result is not surprising because 

the suspended sediment sampling did not attempt to exclude 

phytoplankton. As a result, the filterable material from the 

lower river reaches includes a substantial amount of plankton 

during the summertime growing period. The main difference 

between the suspended sediment and seston samples is that 

the former includes particles both smaller than 80 μm and 

larger than 202 μm. The particles smaller than 80 μm are 

composed of plankton as well as colloidal materials from 

soil and streambank materials. Particles larger than 202 μm 

include some zooplankton as well as larger sediment and 

detrital materials. The more robust trend in the seston samples, 

therefore, is consistent with the fact that the seston samples are 

composed predominantly of plankton whereas the suspended 

sediment samples are a mixture of biological and other 

materials.

The decreasing trend in δ13C with river mile persists 

somewhat for the suspended sediment samples collected in 

winter, despite the fact that phytoplankton are not prevalent 

at that time of year due to high flow, limited light, and cold 

temperatures. The general lack of phytoplankton in winter is 

consistent with the absence of any trends with river mile for 

δ15N and C/N during the winter sampling. Consequently, the 

trend in δ13C during the winter is not directly attributable to 

downstream trends associated with plankton populations. 

The δ15N and δ13C results show that the suspended 

sediment samples can be separated into two groups: samples 

collected from the Tualatin River at and downstream of 

RM 26.9 have lower δ13C and higher δ15N than samples 

collected from the upper river and tributaries (α=0.05). The 

primary difference, as discussed above, may be caused by the 

presence of more phytoplankton in the lower river samples.
18 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon

tac10-0486_fig10

NS

ρ=1.0

ρ=0.9 ρ=-0.7 ρ=0.8

ρ*=0.8

NS

NS

ρ*=0.7

NS

ρ=-0.7

ρ=0.9

ρ=1.0-1.0

Mid-Summer-99 Late-Summer-99 Winter-00 Early-Summer-00

EXPLANATION

Filled dots represent river sites downstream of RM 30

L-Su-98 TR-26.9

TR-5.5

Gales

Dairy

Rock

Fannoa

Fannob

TR-58.8

TR-38.4

TR-26.9

TR-20.3

TR-16.2a

TR-16.2b

TR-9.9

TR-8.7

TR-38.4

TR-26.9

TR-20.3

TR-16.2

TR-9.9

TR-5.5

Gales

Dairy

Rock

Fanno

TR-58.8

TR-38.4

TR-26.9

TR-20.3

TR-16.2

TR-9.9

TR-8.7

TR-5.5

TR-5.5

Gales

Dairy

Rock

Fanno

TR-58.8

TR-38.4

TR-26.9

TR-16.2

TR-5.5

δ13C, in per mil δ15N, in per mil C/N atomic ratio

-38 -36 -34 -32 -30 -28 -26 1 3 5 7 9 11 13 15 0 8 16 24 32 40

Mean value at dot with line showing 95% confidence interval of mean

Open dots represent tributary sites plus river 

sites upstream of RM 30

Data and Spearman coefficient (ρ) for 

correlation with river mile

Suspended sediment

Figure 10. Stable isotope results for suspended sediment samples from the Tualatin River basin, Oregon, with shading showing 

groups of Tualatin River samples. Trends with river mile shown with a correlation coefficient (Spearman ρ) were statistically 

significant (α=0.05, α=0.08 for ρ*, NS=not significant). [a =fraction that settled after 24 hours, b=fraction remaining suspended 

after 24 hours, TR=Tualatin River, number following TR=river mile location, L-Su=late-summer].
Potential Sources of Organic Matter to Tualatin River Sediments 19

Potential Sources of Organic Matter to 

Tualatin River Sediments

To assess the degree to which a range of sampled 

materials (soil, leaf litter, detritus, plankton, duckweed, 

WWTF effluent) might be important sources of organic 

material to Tualatin River bed sediment, the carbon and 

nitrogen isotopic data and C/N ratios of these sources were 

compared to those of bed sediment. Because the organic 

material in bed sediment has decomposed over time, the 

isotopic and C/N values have likely changed relative to their 

original sources. Microbial decomposition increases the 

δ15N by a few per mil and can substantially decrease the C/N 

ratio (Middelburg and Nieuwenhuize, 1998; Kendall and 

others, 2001). Finlay and Kendall (2007) report that the δ15N 

increases associated with decomposition are most pronounced 

in streams that contain ample nitrate, a condition that is true 

for the Tualatin River. Decomposition also may alter the δ13C, 

but the effect is less and tends to be small (Kendall and others, 

2001). 

Several substances (bryozoan, duckweed, periphyton, 

and WWTF effluent particulate) can be dismissed as primary 

sources of organic matter to bed sediment because the patterns 

in their isotopic and C/N ratios do not match those of bed 

sediment, even if trends associated with decomposition are 

taken into account (fig. 11). The δ13C values for bryozoan 

and periphyton are substantially different from those of 

bed sediment. The δ15N values of bryozoan, duckweed, 

and WWTF effluent particulate are greater than those for 

bed sediment. The C/N values for bryozoan, periphyton 

and WWTF effluent particulate are less than those for bed 

sediment. As these substances decompose, their δ15N values 

can be expected to increase and their C/N ratios to decrease, 

making the differences compared to bed sediment even 

greater. 

A comparison of seston and suspended sediment to 

bed sediment shows that the seston and suspended sediment 

samples that contain the most phytoplankton (those at and 

downstream of RM 16.2) do not resemble bed sediment for 

δ13C, δ15N or C/N (fig. 12). The expected changes associated 

with decomposition (increased δ15N, decreased C/N) will 

further amplify these differences. Seston and suspended 

sediment obtained from tributaries and in the more upstream 

reaches of the Tualatin River compare more favorably 

with bed sediment. It is difficult to know whether this 

suspended particulate organic material is a source to the bed 

sediment or vice versa. Bed sediment samples collected in 

late‐summer-1999 have lower δ13C and higher δ15N than other

bed sediment samples, which might indicate some contribution 

from phytoplankton. If the contribution of phytoplankton 

tac10-0486_fig11

18

4

2

6

0

8

10

Bed sediment

Bryozoan

Duckweed

Periphyton

WWTF effluent

particulate

16

12

14

36

28

8

4

0

16

12

20

32

24

EXPLANATION

C/N atomic ratio δ15N, in per mil

-44 -40 -36 -32 -28 -24 -20 -16

δ13C, in per mil

Figure 11. δ13C, δ15N and C/N values for bed sediment and 

several types of potential source materials from the Tualatin River 

basin, Oregon. [WWTF=Wastewater Treatment Facility].

to these samples were significant, however, the C/N ratio of 

the late-summer-1999 bed sediment samples should have 

been lower. For all of these reasons, phytoplankton probably 

is not contributing significant amounts of organic matter to 

Tualatin River bed sediment. This conclusion is consistent 

with field measurements of SOD rates in the Tualatin River, 

which indicated that the river reaches with the largest algal 

populations did not have significantly higher SOD rates, 

except at RM 5.5 where a slightly higher rate might be 

attributed to some deposition of algal detritus (Rounds and 

Doyle, 1997). 
20 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon

C/N atomic ratio

120

100

0

40

20

60

80

8

2

0

-2

-4

δ15N, in per mil

4

6

Bed sediment

Coniferous litter

Deciduous litter

Decomposed terrestrial

detritus

Woody material

Soil

-32 -30 -28 -26 -24

δ13C, in per mil

EXPLANATION

Figure 13. δ13C, δ15N and C/N values of terrestrial 

materials and bed sediment samples from the Tualatin 

River basin, Oregon.

20

14

4

2

0

8

Bed sediment

Bed sediment, L-Su-99

Seston, RM > 16.2

6

10

16

12

18

36

24

4

12

8

16

28

20

32

Suspended sediment, 

tributaries + RM > 26.9

Suspended sediment, 

RM ≤ 26.9

Seston, RM ≤ 16.2

EXPLANATION

C/N atomic ratio δ15N, in per mil

δ13C, in per mil

-40 -38 -36 -34 -32 -30 -28 -26

Figure 12. Comparison of δ13C, δ15N and C/N for 

samples of bed sediment, suspended sediment, and 

seston from the Tualatin River basin, Oregon. [RM=river 

mile].

A comparison of terrestrial source materials to bed 

sediment shows considerable overlap for δ13C and δ15N for 

deciduous litter, woody material, and soil (fig. 13). The range 

of δ13C values for plant litter and woody material encompasses 

the δ13C range for bed sediment. Although δ15N values for 

many of the deciduous litter samples are lower than those of 

bed sediment, increasing these values by 2–3 per mil (within 

the expected effect of decomposition) places them directly 

in the range of δ15N values for bed sediment. The C/N ratios 

for all litter and woody material samples are much higher 

than those for bed sediment, but these ratios are expected 

to decrease with decomposition. In fact, the two samples of 

decomposed terrestrial detritus show C/N ratios that are much 

more similar to those of bed sediment. The δ13C, δ15N, and 

C/N data from soil samples also show substantial overlap with 

the bed sediment data. Although this could indicate that eroded 

soil is a source of bed sediment, it is equally consistent with 

plant litter and woody material being the primary source of 

organic matter to soil and Tualatin River bed sediment.
Potential Sources of Organic Matter to Tualatin River Sediments 21

Principal Components Analysis

Principal components analysis (PCA) is a statistical 

technique used to reduced the dimensionality of datasets 

that contain multiple variables. In PCA, new axes (principal 

components) are created that are linear combinations of the 

original variables. The greatest variability within the dataset is 

captured by the first principal component (PC1). The second 

principal component (PC2) is orthogonal to PC1 and captures 

the greatest remaining variability. PCA was applied to this 

dataset as a method to visualize the three variables δ13C, δ15N, 

and C/N in a two dimensional plot. As part of PCA, the data 

were normalized (by subtracting the mean and dividing by the 

standard deviation of the dataset) to account for the different 

scales of the three variables (δ13C, δ15N, and C/N). 

The results of the PCA are summarized in table 5. 

Together, PC1 and PC2 capture 86 percent of the variability 

in the dataset. The principal components plot is shown in 

figure 14. The black vectors (arrows) in that figure originate at 

the mean value for the entire dataset and point in the direction 

associated with each of the individual variables, δ13C, 

δ15N, and C/N. Note that the δ13C vector is pointing toward 

increasing negative values (decreasing δ13C ) because that 

direction is most pertinent to this discussion.

Examination of the principal components graph (fig. 14) 

leads to the following observations, several of which were 

noted earlier:

• Bryozoan, duckweed, and WWTF effluent particulate 

do not plot at locations similar to bed sediments and, 

therefore, probably are not major sources of organic 

matter to bed sediment.

• Several soil samples plot in locations similar to those of 

bed sediment, suggesting that soil may contribute organic 

material to bed sediment or that the organic material in 

soil and bed sediments have a common source.

• Terrestrial litter (coniferous, deciduous, or woody) 

have principal component values characterized by 

higher C/N and lower δ15N compared to bed sediment. 

Decomposition of this material results in decreased C/N 

and increased δ15N. Assuming a 25 percent decrease in 

C/N coupled with a 2 per mil increase in δ15N results 

in a trajectory that leads directly to the region where 

bed sediments plot. Examination of data reported by 

Middelburg and Nieuwenhuize (1998) for suspended 

matter in progressive stages of decomposition showed 

an approximate 10 percent decrease in C/N with each 

1 per mil increase in δ15N, which is consistent with the 

calculated trajectory from this study. 

• Decomposition generally leads to increasing δ15N and 

decreasing C/N. Although the slope is unknown, the 

typical direction is toward the upper left (lower PC1 

and higher PC2). Any shift in this direction will make 

seston, suspended sediment, WWTF effluent particulate, 

periphyton, duckweed, and bryozoan less similar to bed 

sediments.

• Increasing amounts of phytoplankton are associated 

with increasingly negative δ13C and positive δ15N and, 

therefore, cannot be a major source to bed sediment. 

The bed sediment samples from late-summer-1999 from 

downstream of RM 26.9 shift slightly toward increasing 

phytoplankton, indicating that phytoplankton probably 

contributes a small amount of organic material to bed 

sediment during certain times in the lower reaches of the 

river.

• Suspended sediment and seston have similar 

characteristics, with seston showing an increased 

influence from phytoplankton. Some suspended sediment 

samples are similar to bed sediment and soil, but others 

are clearly affected by the presence of phytoplankton.

Table 5. Results of principal components analysis.

Principal 

component

Proportion 

of variance

(percent)

Eigenvectors 

(loadings)

Equation to calculate PC using original units

PCi = Ai * δ13C + Bi * δ15N + Ci * C/N + Di

δ13C δ15N C/N Ai Bi Ci Di

1 (PC1) 64 0.529 -0.619 0.580 0.1545 -0.1876 0.03455 5.01

2 (PC2) 22 0.811 0.169 -0.560 0.2369 0.05119 -0.03332 7.33
22 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon

The principal components plot also enables a qualitative 

examination of the effect of mixing several sources. For 

example, a mixture of WWTF effluent particulate and 

terrestrial plant litter mathematically could lead to the 

observed bed sediment pattern. This mixture, however, is 

not realistic because not all bed sediments were collected 

downstream of WWTFs. In general, the bed sediment samples 

plot in a region that makes it unlikely that extensive mixtures 

of the potential source substances could account for the δ13C, 

δ15N, and C/N values of bed sediment. Bed sediment samples 

plot farther to the upper right than most of the potential source 

materials except soil and two unusual periphyton samples. 

Erosional and transport processes throughout the drainage 

basin make soil a likely potential source of organic matter 

in bed sediment. The possibility that some unusual types of 

periphyton could be present in sufficient quantity to create a 

mixture resembling bed sediment, however, is remote.

Principal component 2

4

3

2

1

0

-1

-2

-3

-4

Principal component 1

Increasing C/N

Increasing

phytoplankton

population

Potential decomposition

trend for terrestrial

vegetation

Decreasing δ13C

Increasing δ15N

-5 -4 -3 -2 -1 0 1 2 3 4 5

Bed sediment without Late-Summer-99

Bed sediment Late-Summer-99

Bryozoan

Coniferous litter

Deciduous litter

Decomposed terrestrial detritus

Decomposed duckweed

Periphyton

Soil

Suspended sediment

Woody material

WWTF effluent particulate

Duckweed

Seston (80–202 μm)

EXPLANATION

Figure 14. Results of a principal components analysis of δ13C, δ15N, and C/N data for samples taken from the Tualatin River 

basin, Oregon. [WWTF =Wastewater Treatment Facility].
Summary and Conclusions 23

Summary and Conclusions

Isotopic composition of carbon and nitrogen and C/N 

ratios were used to assess the potential contribution of various 

sources of organic matter to bed sediment in the Tualatin 

River. Samples of bed sediment, suspended sediment, and 

seston (suspended particulate material, including plankton 

and organic detritus) in the Tualatin River were collected 

during five sampling events in 1998–2000. During the same 

time period, potential source materials such as soil, plant 

litter, duckweed, and wastewater treatment facility effluent 

particulate were collected for comparison of their isotopic 

composition.

Bed sediment δ15N was slightly lower in tributaries and 

in the upper reaches of the river and may indicate that the 

organic matter in these areas is fresher, less decomposed, 

or more labile. Higher SOD rates have been measured in 

the tributaries compared to the main stem Tualatin River, 

supporting the hypothesis that this material may be more 

labile. No general trends in δ13C or C/N for bed sediment 

with river location were observed. Bed sediment in the lower 

river, which is associated with the most phytoplankton growth, 

was not usually different from bed sediment farther upstream 

where less algae is present. Bed sediment collected from the 

lower river in late summer (1999), however, did show a small 

difference, a likely influence of phytoplankton.

Phytoplankton was evident in seston and suspended 

sediment samples and characterized by low δ13C (<-32 

per mil), high δ15N (>8 per mil), and low C/N (<12). The 

increasing amount of phytoplankton in the more downstream 

river samples was reflected in distinct trends in the isotopic 

data and C/N ratios with river mile. The isotopic data for 

samples that contained the most phytoplankton did not 

resemble bed sediment. Decomposition of organic matter 

tends to decrease the C/N ratio and increase the δ15N value, 

further increasing the differences compared to bed sediment. 

Therefore, phytoplankton likely is not a major source of 

organic matter to bed sediment. Reductions in the size of the 

algal community, therefore, may have little effect on the rate 

of sediment oxygen demand.

Compared to bed sediment, the nitrogen content was 

heavier (higher δ15N ) and/or the C/N ratio was lower for 

several types of samples, including duckweed, periphyton 

and wastewater treatment facility effluent particulate. Further 

decomposition of these materials would tend to increase 

the δ15N and decrease the C/N, increasing their differences 

compared to bed sediment. It is, therefore, unlikely that 

duckweed, periphyton, or wastewater treatment facility 

effluent are significant sources of organic matter to bed 

sediment. Periphyton samples exhibited δ13C values that 

spanned the widest range of any of the types of samples 

collected for this study; the inconsistency of the δ13C of 

periphyton limits the use of δ13C as a tracer for this class of 

sample.

The δ13C, δ15N, and C/N for samples of soil and 

decomposed terrestrial organic matter closely resembled 

results for bed sediments. Although soil may be a direct source 

of organic matter to bed sediment, terrestrial plant material 

likely is a source of organic matter to both bed sediments 

and soils. Deciduous litter, woody material, and coniferous 

litter have δ13C values that match soils and bed sediments 

well. Although the δ15N and C/N ratios for fresh leaf litter 

and twigs do not match the δ15N and C/N ratios for soils and 

bed sediments, decomposition of those materials is expected 

to shift the δ15N and C/N toward those of bed sediment, 

resulting in a good match. Furthermore, the basin produces a 

considerable quantity of terrestrial plant litter which easily is 

transported to the stream network. It is consistent to conclude, 

therefore, that soil and leaf litter probably are the primary 

sources of organic matter to Tualatin River bed sediment. 

Monitoring and management plans that aim to improve 

oxygen conditions in the river would be most successful 

by concentrating on sources of soil, leaf litter, and other 

terrestrially derived organic materials to the river rather than 

on the instream growth of algae.

Acknowledgments

The authors thank the following people for their 

contributions to this work: Chauncey Anderson, Amy Brooks, 

Kurt Carpenter, Micelis Doyle, Wes Jarrell, Matt Johnston, 

and Tammy Wood for assistance in sample collection; Renate 

Ryan for assistance in not only sample collection but also 

processing and freeze-drying; Carol Kendall and the graduate 

and post-doctoral students in her stable isotopes laboratory for 

the many hours spent analyzing samples from this study and 

their help in interpreting the laboratory data; and Jan Miller 

of Clean Water Services for helping to organize and fund 

the project. Finally, the authors are grateful to the group of 

reviewers that provided helpful comments on this report.

References Cited

Bernasconi, S.M., Barbieri, A., and Simona, M., 1997, Carbon 

and nitrogen isotope variations in sedimenting organic 

matter in Lake Lugano: Limnology and Oceanography, 

v. 42, no. 8, p. 1955–1765.

Edwards, T.K., and Glysson, G.D., 1999, Field methods for 

measurement of fluvial sediment: U.S. Geological Survey 

Techniques of Water-Resources Investigations, book 3, 

chap. C2, 89 p.
24 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon

Finlay, J.C., and Kendall, C., 2007, Stable isotope tracing of 

temporal and spatial variability in organic matter sources to 

freshwater ecosystems, in Michener, R.H., and Lajtha, K., 

eds., Stable Isotopes in Ecology and Environmental Science 

(2d ed.): Hoboken, N.J., Wiley-Blackwell, p. 283–333.

Helsel, D.R., and Hirsch, R.M., 1992, Statistical methods in 

water resources: Amsterdam, Elsevier Science Publishers, 

522 p.

Homer, C., Dewitz, J., Fry, J., Coan, M., Hossain, N., 

Larson, C., Herold, N., McKerrow, A., VanDriel, J.N., 

and Wickham, J., 2007, Completion of the 2001 National 

Land Cover Database for the conterminous United States: 

Photogrammetric Engineering and Remote Sensing, v. 73, 

no. 4, p. 337–341.

Kendall, C., Silva, S.R., and Kelly, V.J., 2001, Carbon and 

nitrogen isotopic compositions of particulate organic 

matter in four large river systems across the United States: 

Hydrological Processes, v. 15, no. 7, 1301–1346. (Also 

available at http://dx.doi.org/10.1002/hyp.216.)

Middelburg, J.J., and Nieuwenhuize, J., 1998, Carbon and 

nitrogen stable isotopes in suspended matter and sediments 

from the Schelde Estuary: Marine Chemistry, v. 60, 

p. 217–225.

Miller, J.C., and Miller, J.N., 1988, Statistics for analytical 

chemistry (2d ed.): New York, John Wiley and Sons, 227 p.

Oregon Department of Environmental Quality, 2001, Tualatin 

subbasin Total Maximum Daily Load (TMDL): Portland, 

Oregon, Oregon Department of Environmental Quality, 

165 p., accessed October 8, 2009, at http://www.deq.state.

or.us/wq/TMDLs/docs/willamettebasin/tualatin/tmdlwqmp.

pdf.

Rounds, S.A., and Doyle, M.C., 1997, Sediment oxygen 

demand in the Tualatin River Basin, Oregon, 1992-1996: 

U.S. Geological Survey Water-Resources Investigations 

Report 97-4103, 19 p.

Rounds, S.A., Wood, T.M., and Lynch, D.D., 1999, Modeling 

discharge, temperature, and water quality in the Tualatin 

River, Oregon: U.S. Geological Survey Water-Supply Paper 

2465-B, 121 p.

SAS Institute Inc., 1989, SAS/STAT® version 6.07.01, Cary, 

N.C.

Tualatin River Flow Management Technical Committee, 2000, 

Annual data report for 1999: Clean Water Services and 

Oregon Water Resources Department, accessed October 9, 

2009, at http://www.co.washington.or.us/Watermaster/

SurfaceWater/upload/FlowReport-1999.pdf.

U.S. Census Bureau, 2000, State and County QuickFacts: U.S. 

Census Bureau website, accessed October 6, 2009, at http://

quickfacts.census.gov/qfd/states/41/41067.html.
Table 6 25

ID Site name Sample type Sample detail Date

δ13C δ15N C/N atomic ratio

Mean 95%CI n Mean 95%CI n low-N 

n

Mean 95%CI n 1-sf 

n

Late-Summer 1998

401 Tualatin River at RM 5.5 

(Stafford Road)

Seston, >80 μm – 08-13-98 -35.03 0.11 6 9.34 0.33 6 0 5.39 0.38 6 0

402 Tualatin River at RM 5.5 

(Stafford Road)

Periphyton Species not identified 08-13-98 -33.15 0.75 4 12.90 1.04 4 0 4.95 1.34 4 0

403 Tualatin River at RM 20.3 Periphyton Species not identified 08-18-98 -18.42 0.22 3 5.80 0.44 3 0 11.68 1.12 3 0404 Henry Hagg Lake Seston, >80 μm – 08-11-98 -26.34 0.24 4 6.90 0.46 4 0 10.33 1.09 4 0405 Tualatin River at RM 24.5 Duckweed Duckweed sorted from mat 09-29-98 -29.44 0.12 4 6.82 0.34 4 0 11.85 0.94 4 0406 Tualatin River at RM 5.5 

(Stafford Road)

Suspended sediment – 09-17-98 -33.08 0.28 3 7.38 0.44 3 0 7.69 1.53 3 0

407 Tualatin River at RM 26.9 

(Scholls)

Suspended sediment – 09-17-98 -27.95 0.21 4 4.93 0.50 4 0 11.40 1.45 4 0

408 Tualatin River at RM 5.5 

(Stafford Road)

Bed sediment – 08-20-98 -28.03 0.36 9 4.32 0.67 9 2 16.22 2.43 9 4

409 Tualatin River at RM 26.9 

(Scholls)

Bed sediment – 08-18-98 -27.52 0.29 9 3.79 1.02 9 0 17.52 3.29 9 4

410 Jackson Bottom (between Miller 

Swale and holding pond)

Soil Chehalis soil 10-06-98 -26.64 0.18 4 5.44 0.41 4 0 12.38 0.84 4 0

411 Zurcher Farm (Fernhill Road near 

Tualatin River)

Soil Wapato soil 10-06-98 -26.06 0.09 7 5.08 0.83 7 0 12.81 1.03 7 0

412 Oregon Graduate Institute (near 

Bronson Creek)

Soil Woodburn soil 10-06-98 -27.20 0.13 3 -0.87 0.93 3 0 24.60 1.63 3 0

413 Jackson Bottom (between Miller 

Swale and holding pond)

Leaf litter Oregon Ash leaf litter 10-06-98 -30.41 0.14 4 2.19 0.25 4 0 29.08 2.72 3 0

414 Tualatin River at RM 67.8 

(Cherry Grove)

Coniferous litter Western Red Cedar litter 10-06-98 -26.80 0.39 3 -0.20 0.98 3 0 46.53 8.83 3 0

415 Tualatin River at RM 67.8 

(Cherry Grove)

Leaf litter Alder leaf litter 10-06-98 -29.50 0.13 4 -1.64 0.10 4 0 32.93 2.29 4 0

416 Patton Valley Road (north side, 

1 mi east of Cherry Grove)

Coniferous litter Douglas Fir litter 10-06-98 -27.41 0.14 4 -0.55 0.23 4 0 67.04 2.10 4 0

417 Patton Valley Road (north side, 

1 mi east of Cherry Grove)

Woody material Douglas Fir twigs 10-06-98 -26.48 0.42 4 -2.87 0.14 4 1 77.75 27.70 4 0

418 Rock Creek Wastewater 

Treatment Facility

WWTF effluent particulate – 10-06-98 -26.64 0.16 4 11.61 1.03 4 0 5.47 1.77 4 0

419 Tualatin River at RM 5.5 

(Stafford Road)

Bryozoan – 08-13-98 -35.36 0.32 4 16.13 1.34 4 0 4.24 1.34 4 0

Table 6. Mean values and confidence intervals of stable isotope compositions (δ13C, δ15N) and C/N ratios for samples collected in the Tualatin River basin, Oregon.[Abbreviations: RM, river mile; n, number of splits used in calculation of mean and confidence interval; 95% CI, 95-percent confidence limit of mean; low-N n, number of splits that contained less than 1 micromole N; 1-sf n, number of splits in which the percent nitrogen value had only 1 significant digit; WWTF, wastewater treatment facililty; μm, micrometer; na, not applicable]
26 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon ID Site name Sample type Sample detail Date

δ13C δ15N C/N atomic ratio

Mean 95%CI n Mean 95%CI n low-N 

n

Mean 95%CI n 1-sf 

n

Mid-Summer 1999

1 Henry Hagg Lake Seston, >80 μm – 07-09-99 -29.06 0.38 4 7.04 0.48 4 0 5.41 0.86 4 02 Henry Hagg Lake Seston, 80–202 μm – 07-09-99 -28.91 0.34 3 6.33 0.53 3 0 5.83 0.18 3 03 Tualatin River at RM 20.3 Seston, >80 μm – 07-14-99 -30.46 0.16 3 7.77 0.63 3 0 11.35 1.07 3 04 Tualatin River at RM 20.3 Seston, 80–202 μm – 07-14-99 -30.70 0.15 4 7.75 0.93 4 0 10.19 1.02 4 05 Tualatin River at RM 20.3 Duckweed Duckweed sorted from mat 07-14-99 -28.65 0.14 3 10.48 0.81 3 0 14.61 1.00 3 06 Tualatin River at RM 20.3 Woody material Twigs sorted from 

duckweed mat

07-14-99 -29.03 0.78 3 2.65 0.48 3 0 31.62 5.83 3 0

7 Tualatin River at RM 20.3 Suspended sediment – 07-14-99 -32.24 0.31 4 8.99 0.52 4 0 7.61 1.16 4 08 Tualatin River at RM 20.3 Bed sediment – 07-14-99 -27.46 0.12 3 5.63 3.01 2 0 14.67 1.74 3 2

10 Tualatin River at RM 20.3 Coniferous litter Cones sorted from 

duckweed mat

07-14-99 -27.25 0.35 3 0.16 3.34 3 3 110.57 25.40 3 0

12 Tualatin River at RM 20.3 Leaf litter Oregon Ash seed pods from 

river surface

07-14-99 -25.55 0.31 4 1.51 0.75 4 1 64.88 15.43 4 0

13 Tualatin River at RM 20.3 Leaf litter Oregon Ash leaves from 

river surface

07-14-99 -27.06 0.40 3 0.88 0.75 3 0 30.96 3.81 3 0

14 Tualatin River at RM 26.9 

(Scholls)

Seston, >80 μm – 07-14-99 -28.51 0.13 3 6.67 0.60 3 0 16.55 2.43 3 0

15 Tualatin River at RM 26.9 

(Scholls)

Seston, 80–202 μm – 07-14-99 -28.27 0.18 3 6.24 0.57 3 2 17.23 0.99 3 0

16 Tualatin River at RM 26.9 

(Scholls)

Suspended sediment – 07-14-99 -28.55 0.28 4 6.81 0.91 4 2 9.47 1.33 4 0

17 Tualatin River at RM 26.9 

(Scholls)

Bed sediment – 07-14-99 -27.51 0.38 3 5.89 0.70 3 0 14.73 2.24 3 0

18 Tualatin River at RM 26.9 

(Scholls)

Duckweed Duckweed sorted from mat 07-14-99 -28.48 na 1 9.32 na 1 0 12.00 na 1 0

19 Tualatin River at RM 26.9 

(Scholls)

Woody material Twigs sorted from 

duckweed mat

07-14-99 -26.45 0.84 3 5.36 0.81 3 0 28.31 2.00 3 0

20 Tualatin River at RM 38.4 

(Rood Bridge)

Suspended sediment – 07-14-99 -28.14 0.11 4 6.41 0.35 4 0 10.49 0.92 4 0

21 Tualatin River at RM 38.4 

(Rood Bridge)

Bed sediment – 07-14-99 -26.74 0.46 3 4.81 0.61 3 0 13.66 1.20 3 3

22 Gales Creek at Old Highway 47 Suspended sediment – 07-16-99 -26.39 0.14 3 4.60 0.48 3 0 8.60 1.30 3 023 Gales Creek at Old Highway 47 Bed sediment – 07-16-99 -27.15 0.15 4 2.62 0.63 4 4 14.61 4.16 4 4

Table 6. Mean values and confidence intervals of stable isotope compositions (δ13C, δ15N) and C/N ratios for samples collected in the Tualatin River basin, Oregon.—Continued[Abbreviations: RM, river mile; n, number of splits used in calculation of mean and confidence interval; 95% CI, 95-percent confidence limit of mean; low-N n, number of splits that contained less than 1 micromole N; 1-sf n, number of splits in which the percent nitrogen value had only 1 significant digit; WWTF, wastewater treatment facililty; μm, micrometer; na, not applicable]
Table 6 27

ID Site name Sample type Sample detail Date

δ13C δ15N C/N atomic ratio

Mean 95%CI n Mean 95%CI n low-N 

n

Mean 95%CI n 1-sf 

n

Mid-Summer 1999—Continued

24 Dairy Creek at Highway 8 Suspended sediment – 07-16-99 -29.59 0.18 3 6.17 0.36 3 0 8.91 1.32 3 025 Dairy Creek at Highway 8 Bed sediment – 07-16-99 -26.92 0.46 3 4.30 0.51 2 1 16.50 2.52 3 226 Tualatin River at RM 58.8 

(Dilley)

Suspended sediment – 07-16-99 -27.63 0.53 3 4.10 0.74 3 3 11.08 3.22 3 3

27 Tualatin River at RM 58.8 

(Dilley)

Bed sediment – 07-16-99 -27.06 0.33 3 2.71 0.69 3 3 15.35 2.75 3 3

28 Rock Creek at Highway 8 Suspended sediment – 07-16-99 -29.21 0.31 3 5.22 1.69 3 1 10.31 1.66 3 029 Rock Creek at Highway 8 Bed sediment – 07-16-99 -27.98 0.13 3 5.81 0.69 3 0 15.31 1.05 3 030 Tualatin River at RM 5.5 

(Stafford Road)

Suspended sediment – 07-16-99 -35.41 0.18 3 9.11 0.73 3 0 5.78 1.41 3 0

31 Tualatin River at RM 5.5 

(Stafford Road)

Seston, >80 μm – 07-19-99 -37.46 0.23 3 9.01 0.63 3 0 5.87 1.39 3 0

32 Tualatin River at RM 5.5 

(Stafford Road)

Seston, 80–202 μm – 07-19-99 -37.64 0.05 4 9.22 0.57 4 0 5.92 0.44 4 0

33 Tualatin River at RM 5.5 

(Stafford Road)

Bed sediment – 07-19-99 -27.41 0.72 4 5.74 1.17 3 0 12.35 1.96 4 0

34 Tualatin River at RM 5.5 

(Stafford Road)

Periphyton Spirogyra 07-19-99 -17.36 0.22 3 6.87 0.55 3 0 10.64 1.03 3 0

35 Tualatin River at RM 9.9 

(Cook Park)

Seston, >80 μm – 07-19-99 -35.05 0.20 3 8.25 0.54 3 0 7.29 1.33 3 0

36 Tualatin River at RM 9.9

(Cook Park)

Seston, 80–202 μm – 07-19-99 -34.99 0.33 3 9.10 1.01 3 3 6.92 1.41 3 0

37 Tualatin River at RM 9.9 

(Cook Park)

Suspended sediment – 07-19-99 -34.98 0.12 4 7.29 0.82 3 0 6.86 0.78 5 0

38 Tualatin River at RM 9.9 

(Cook Park)

Bed sediment – 07-19-99 -28.16 0.22 6 5.48 0.29 6 6 13.97 1.54 6 6

39 Tualatin River at RM 9.9 

(Cook Park)

Duckweed Unsorted duckweed mat 07-19-99 -28.50 0.33 4 3.20 0.33 4 0 27.21 1.32 4 0

40 Tualatin River at RM 9.9 

(Cook Park)

Duckweed Duckweed sorted from mat 07-19-99 -29.85 0.06 3 6.90 0.39 3 0 11.25 1.00 3 0

41 Tualatin River at RM 9.9 

(Cook Park)

Woody material Twigs sorted from 

duckweed mat

07-19-99 -27.82 1.11 6 2.30 0.15 6 0 29.96 0.41 6 0

42 Tualatin River at RM 9.9 

(Cook Park)

Coniferous litter Cones sorted from 

duckweed mat

07-19-99 -26.55 0.05 3 0.72 1.03 3 3 90.52 16.79 3 0

Table 6. Mean values and confidence intervals of stable isotope compositions (δ13C, δ15N) and C/N ratios for samples collected in the Tualatin River basin, Oregon.—Continued[Abbreviations: RM, river mile; n, number of splits used in calculation of mean and confidence interval; 95% CI, 95-percent confidence limit of mean; low-N n, number of splits that contained less than 1 micromole N; 1-sf n, number of splits in which the percent nitrogen value had only 1 significant digit; WWTF, wastewater treatment facililty; μm, micrometer; na, not applicable]
28 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon ID Site name Sample type Sample detail Date

δ13C δ15N C/N atomic ratio

Mean 95%CI n Mean 95%CI n low-N 

n

Mean 95%CI n 1-sf 

n

Mid-Summer 1999—Continued

43 Tualatin River at RM 9.9 

(Cook Park)

Soil A-horizon from bank with 

slump

07-19-99 -26.10 0.22 3 1.38 1.12 3 0 29.92 3.08 3 0

44 Tualatin River at RM 9.9 

(Cook Park)

Soil Bottom of slump at water 

edge

07-19-99 -27.12 0.28 3 5.29 1.71 4 4 14.29 3.14 4 4

45 Tualatin River at RM 8.7 

(Boones Ferry Bridge)

Seston, >80 μm – 07-19-99 -34.88 0.21 3 10.58 0.99 3 0 7.61 1.24 3 0

46 Tualatin River at RM 8.7 

(Boones Ferry Bridge)

Seston, 80–202 μm – 07-19-99 -34.83 0.26 3 10.88 1.15 3 3 7.65 1.45 3 0

47 Tualatin River at RM 8.7 

(Boones Ferry Bridge)

Suspended sediment – 07-19-99 -35.82 0.13 4 12.19 1.11 4 0 6.96 1.16 4 0

48 Tualatin River at RM 8.7 

(Boones Ferry Bridge)

Bed sediment – 07-19-99 -27.84 1.00 4 5.57 1.59 4 4 13.77 2.12 4 4

49 Tualatin River at RM 16.2 (Elsner 

Bridge)

Suspended sediment Fraction that settled after 

24 hours

07-21-99 -29.79 0.68 4 5.55 1.31 3 0 9.06 0.87 4 0

50 Tualatin River at RM 16.2 (Elsner 

Bridge)

Seston, >80 μm Aphanizomenon floating on 

sample

07-21-99 -34.42 0.32 3 7.58 0.64 3 0 4.37 1.63 3 0

51 Tualatin River at RM 16.2 (Elsner 

Bridge)

Seston, >80 μm – 07-21-99 -29.36 0.39 7 na na 0 0 12.35 0.53 7 0

52 Tualatin River at RM 16.2 (Elsner 

Bridge)

Seston, 80–202 μm – 07-21-99 -30.45 0.49 3 5.98 0.94 3 3 10.07 1.27 3 0

53 Tualatin River at RM 16.2 (Elsner 

Bridge)

Bed sediment – 07-21-99 -27.18 0.87 3 5.20 0.62 3 1 17.02 4.70 3 3

54 Tualatin River at RM 16.2 (Elsner 

Bridge)

Woody material Twigs removed from bed 

sediment

07-21-99 -27.01 0.62 4 4.56 0.47 4 4 91.83 12.02 2 0

55 Fanno Creek at Durham 

City Park

Suspended sediment Fraction that settled after 

24 hours

07-21-99 -29.01 0.54 4 4.82 1.42 4 0 13.52 0.54 4 0

56 Fanno Creek at Durham 

City Park

Seston, >80 μm – 07-21-99 -28.74 0.64 6 6.26 1.00 6 6 13.06 1.29 6 0

57 Fanno Creek at Durham 

City Park

Seston, 80–202 μm – 07-21-99 -28.41 0.47 3 5.37 0.45 3 3 14.43 1.02 3 0

58 Fanno Creek at Durham 

City Park

Bed sediment – 07-21-99 -28.01 0.18 4 3.57 0.78 4 4 14.58 4.04 4 4

59 Fanno Creek at Durham 

City Park

Bed sediment Top 10 cm, both oxic and 

anoxic fractions

07-21-99 -27.99 0.30 3 3.56 0.88 3 0 17.42 4.00 3 0

Table 6. Mean values and confidence intervals of stable isotope compositions (δ13C, δ15N) and C/N ratios for samples collected in the Tualatin River basin, Oregon.—Continued[Abbreviations: RM, river mile; n, number of splits used in calculation of mean and confidence interval; 95% CI, 95-percent confidence limit of mean; low-N n, number of splits that contained less than 1 micromole N; 1-sf n, number of splits in which the percent nitrogen value had only 1 significant digit; WWTF, wastewater treatment facililty; μm, micrometer; na, not applicable]
Table 6 29

ID Site name Sample type Sample detail Date

δ13C δ15N C/N atomic ratio

Mean 95%CI n Mean 95%CI n low-N 

n

Mean 95%CI n 1-sf 

n

Mid-Summer 1999—Continued

60 Fanno Creek at Durham 

City Park

Leaf litter Redtwig dogwood leaves 

in stream

07-21-99 -29.60 0.17 3 4.46 0.53 3 0 33.94 2.90 3 0

61 Fanno Creek at Durham 

City Park

Leaf litter Oregon Ash leaves in 

stream

07-21-99 -26.80 0.10 3 3.17 0.54 3 0 51.42 9.59 3 0

62 Fanno Creek at Durham 

City Park

Decomposed terrestrial 

detritus

Decomposed leaves & 

twigs in stream

07-21-99 -27.85 0.43 3 4.92 0.74 3 0 22.21 4.13 3 0

63 Fanno Creek at Durham 

City Park

Leaf litter Oregon Ash leaves from 

trail

07-21-99 -27.29 0.91 3 0.88 0.37 4 0 19.95 5.21 2 0

64 Fanno Creek at Durham 

City Park

Leaf litter Oregon Ash seed pods from 

trail

07-21-99 -26.80 0.95 5 0.80 0.44 5 0 46.79 4.19 5 0

65 Fanno Creek at Durham 

City Park

Periphyton Cladophera 07-21-99 -39.69 0.11 3 4.56 0.31 3 0 8.00 1.21 3 0

67 Tualatin River at RM 9.4 

(Basalt sill)

Periphyton Cladophera 07-19-99 -34.14 0.15 3 5.50 0.39 3 0 11.02 1.10 3 0

68 Onion Flat (Cipole Road 

and Highway 99W)

Soil Agricultural field, tilled, not 

planted

07-21-99 -27.87 0.13 2 4.81 1.02 3 0 17.40 1.58 3 0

69 Jackson Bottom (between Miller 

Swale and holding pond)

Soil Chehalis soil 08-04-99 -27.21 0.31 3 6.12 0.90 3 0 11.14 1.41 3 0

70 Jackson Bottom (between Miller 

Swale and holding pond)

Leaf litter Oregon Ash leaves 08-04-99 -25.06 0.48 3 2.02 0.98 3 0 66.10 7.82 3 0

71 Tualatin Nature Park Coniferous litter Mixed Western Red Cedar 

litter

08-04-99 -24.91 0.29 3 -2.53 1.09 3 0 37.02 3.89 3 0

72 Tualatin Nature Park Coniferous litter Mixed Douglas Fir litter 08-04-99 -27.83 0.29 3 -2.62 1.12 3 0 31.90 2.20 3 073 Rock Creek Wastewater 

Treatment Facility

WWTF effluent particulate – 07-14-99 -24.77 1.13 6 10.46 0.84 6 0 6.14 0.90 6 0

74 Durham Wastewater Treatment 

Facility

WWTF effluent particulate – 07-14-99 -26.01 0.10 3 9.26 0.71 3 3 5.31 1.47 3 3

76 Tualatin River at RM 16.2 (Elsner 

Bridge)

Suspended sediment Fraction remaining 

suspended after 24 hours

07-21-99 -33.86 0.09 3 6.60 0.38 3 0 5.57 1.42 3 0

77 Fanno Creek at Durham 

City Park

Suspended sediment Fraction remaining 

suspended after 24 hours

07-21-99 -28.41 0.17 3 5.06 0.38 3 1 10.14 1.25 3 3

Table 6. Mean values and confidence intervals of stable isotope compositions (δ13C, δ15N) and C/N ratios for samples collected in the Tualatin River basin, Oregon.—Continued[Abbreviations: RM, river mile; n, number of splits used in calculation of mean and confidence interval; 95% CI, 95-percent confidence limit of mean; low-N n, number of splits that contained less than 1 micromole N; 1-sf n, number of splits in which the percent nitrogen value had only 1 significant digit; WWTF, wastewater treatment facililty; μm, micrometer; na, not applicable]
30 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon ID Site name Sample type Sample detail Date

δ13C δ15N C/N atomic ratio

Mean 95%CI n Mean 95%CI n low-N 

n

Mean 95%CI n 1-sf 

n

Late-Summer 1999

101 Henry Hagg Lake Seston, >80 μm – 09-10-99 -30.18 0.16 3 8.46 0.79 3 0 4.47 1.54 3 0102 Henry Hagg Lake Seston, 80–202 μm – 09-10-99 -31.22 0.16 3 6.58 0.50 3 0 6.16 1.37 3 0103 Tualatin River at RM 38.4 

(Rood Bridge)

Suspended sediment – 09-10-99 -31.08 0.28 3 4.12 0.43 3 0 13.92 0.90 3 2

104 Tualatin River at RM 38.4 

(Rood Bridge)

Bed sediment – 09-10-99 -27.88 0.46 8 3.95 0.10 8 0 16.13 1.03 8 1

105 Tualatin River at RM 9.9 

(Cook Park)

Seston, >80 μm – 09-11-99 -33.19 0.62 3 8.05 0.59 3 0 8.24 1.23 3 0

106 Tualatin River at RM 9.9 

(Cook Park)

Seston, 80–202 μm – 09-11-99 -33.00 0.36 3 7.59 0.60 3 0 8.85 1.23 3 0

107 Tualatin River at RM 9.9 

(Cook Park)

Suspended sediment – 09-11-99 -34.06 0.14 4 7.35 0.41 4 0 8.71 1.04 4 0

108 Tualatin River at RM 9.9 

(Cook Park)

Bed sediment – 09-11-99 -30.58 0.74 4 5.16 1.48 4 4 17.26 1.51 3 4

109 Tualatin River at RM 9.4 

(Basalt sill)

Periphyton Cladophera 09-11-99 -35.50 0.13 3 4.28 0.59 3 0 10.03 1.13 3 0

110 Tualatin River at RM 20.3 Seston, >80 μm – 09-13-99 -29.53 0.39 4 4.17 0.30 4 0 12.63 1.62 4 0

111 Tualatin River at RM 20.3 Seston, 80–202 μm – 09-13-99 -30.86 0.41 3 5.88 0.93 3 0 11.91 2.31 3 0

112 Tualatin River at RM 20.3 Suspended sediment – 09-13-99 -30.80 1.35 3 6.73 0.77 3 0 14.84 2.21 3 0113 Tualatin River at RM 20.3 Bed sediment – 09-13-99 -29.30 0.35 5 5.49 0.44 4 0 15.86 1.38 5 0114 Tualatin River at RM 20.3 Bed sediment Anoxic blue-gray fraction 09-13-99 -28.72 0.27 4 5.37 0.77 4 4 14.75 1.17 4 4115 Tualatin River at RM 16.2 (Elsner 

Bridge)

Suspended sediment – 09-13-99 -32.27 0.98 3 7.08 2.60 2 0 11.86 1.22 3 0

116 Tualatin River at RM 16.2 (Elsner 

Bridge)

Seston, >80 μm – 09-13-99 -31.07 0.51 3 5.96 0.37 3 1 10.05 1.17 3 0

117 Tualatin River at RM 16.2 (Elsner 

Bridge)

Seston, 80–202 μm – 09-13-99 -31.41 0.53 4 6.69 0.40 4 4 10.75 1.24 4 0

118 Tualatin River at RM 16.2 (Elsner 

Bridge)

Bed sediment – 09-13-99 -28.72 0.08 3 6.05 0.36 3 0 16.45 0.99 3 0

119 Tualatin River at RM 26.9 

(Scholls)

Seston, >80 μm – 09-15-99 -28.93 0.17 3 6.38 0.52 3 2 14.03 0.90 3 0

120 Tualatin River at RM 26.9 

(Scholls)

Seston, 80–202 μm – 09-15-99 -29.00 0.13 4 5.75 0.32 4 0 14.47 0.89 4 0

Table 6. Mean values and confidence intervals of stable isotope compositions (δ13C, δ15N) and C/N ratios for samples collected in the Tualatin River basin, Oregon.—Continued[Abbreviations: RM, river mile; n, number of splits used in calculation of mean and confidence interval; 95% CI, 95-percent confidence limit of mean; low-N n, number of splits that contained less than 1 micromole N; 1-sf n, number of splits in which the percent nitrogen value had only 1 significant digit; WWTF, wastewater treatment facililty; μm, micrometer; na, not applicable]
Table 6 31

ID Site name Sample type Sample detail Date

δ13C δ15N C/N atomic ratio

Mean 95%CI n Mean 95%CI n low-N 

n

Mean 95%CI n 1-sf 

n

Late-Summer 1999—Continued

121 Tualatin River at RM 26.9 

(Scholls)

Suspended sediment – 09-15-99 -28.47 1.23 4 7.12 1.07 3 0 14.47 0.84 4 0

122 Tualatin River at RM 26.9 

(Scholls)

Bed sediment – 09-15-99 -29.55 0.14 7 5.66 0.21 5 1 17.45 1.50 7 4

123 Tualatin River at RM 5.5 

(Stafford Road)

Suspended sediment – 09-15-99 -33.68 0.30 3 12.79 1.29 3 0 9.54 1.18 3 0

124 Tualatin River at RM 5.5 

(Stafford Road)

Seston, >80 μm – 09-15-99 -37.66 0.08 4 16.71 1.39 4 0 5.69 1.23 4 0

125 Tualatin River at RM 5.5 

(Stafford Road)

Seston, 80–202 μm – 09-15-99 -38.23 0.50 3 17.36 2.39 2 0 5.31 1.46 3 0

126 Tualatin River at RM 5.5 

(Stafford Road)

Bed sediment – 09-15-99 -29.42 0.08 3 6.29 0.57 3 0 13.05 1.21 3 0

Winter 2000

201 Tualatin River at RM 38.4 

(Rood Bridge)

Suspended sediment – 02-08-00 -30.71 0.85 3 4.89 1.38 3 0 12.12 2.46 3 3

202 Tualatin River at RM 5.5 

(Stafford Road)

Suspended sediment – 02-04-00 -32.01 0.46 5 4.05 1.06 5 5 16.19 1.51 5 5

203 Tualatin River at RM 26.9 

(Scholls)

Suspended sediment – 02-04-00 -31.01 0.35 5 4.29 0.51 3 3 17.83 1.76 5 3

204 Tualatin River at RM 26.9 

(Scholls)

Bed sediment Woody debris removed 02-04-00 -27.64 0.18 6 4.83 0.67 6 3 32.43 2.39 6 0

206 Tualatin River at RM 16.2 (Elsner 

Bridge)

Suspended sediment – 02-04-00 -30.96 0.42 3 3.86 1.70 3 2 15.36 2.55 3 3

207 Tualatin River at RM 16.2 (Elsner 

Bridge)

Bed sediment – 02-04-00 -28.55 0.31 4 4.07 0.42 4 4 27.11 2.24 4 4

208 Gales Creek at Old Highway 47 Suspended sediment – 02-07-00 -28.88 1.91 3 3.60 0.80 2 2 33.00 5.73 3 2209 Dairy Creek at Highway 8 Suspended sediment – 02-07-00 -31.57 0.64 5 3.87 0.40 4 4 15.19 1.27 5 4210 Tualatin River at RM 58.8 

(Dilley)

Suspended sediment – 02-07-00 -29.55 0.72 6 3.61 0.69 6 4 16.51 1.44 6 6

211 Rock Creek at Highway 8 Suspended sediment – 02-07-00 -32.51 0.79 4 4.59 0.44 4 4 17.58 2.33 4 4

212 Fanno Creek at Durham Road Suspended sediment – 02-07-00 -31.66 0.71 6 4.34 0.53 6 6 16.11 1.19 6 6

Table 6. Mean values and confidence intervals of stable isotope compositions (δ13C, δ15N) and C/N ratios for samples collected in the Tualatin River basin, Oregon.—Continued[Abbreviations: RM, river mile; n, number of splits used in calculation of mean and confidence interval; 95% CI, 95-percent confidence limit of mean; low-N n, number of splits that contained less than 1 micromole N; 1-sf n, number of splits in which the percent nitrogen value had only 1 significant digit; WWTF, wastewater treatment facililty; μm, micrometer; na, not applicable]
32 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon ID Site name Sample type Sample detail Date

δ13C δ15N C/N atomic ratio

Mean 95%CI n Mean 95%CI n low-N 

n

Mean 95%CI n 1-sf 

n

Early-Summer 2000

301 Henry Hagg Lake Seston, >80 μm – 06-03-00 -26.37 0.17 4 3.38 0.24 4 0 11.49 0.43 4 0302 Henry Hagg Lake Seston, 80–202 μm – 06-03-00 -26.34 0.80 4 3.03 0.14 4 1 10.07 0.56 4 0303 Tualatin River at RM 38.4 

(Rood Bridge)

Suspended sediment – 06-05-00 -31.14 0.13 4 5.39 0.18 4 0 11.56 0.55 4 0

304 Tualatin River at RM 38.4 

(Rood Bridge)

Bed sediment – 06-05-00 -28.12 0.12 3 4.06 0.49 3 0 15.81 1.23 3 0

305 Tualatin River at RM 9.9 

(Cook Park)

Seston, >80 μm – 06-03-00 -32.55 0.20 3 9.02 0.49 3 0 8.87 0.22 3 0

306 Tualatin River at RM 9.9 

(Cook Park)

Seston, 80–202 μm – 06-03-00 -32.56 0.15 4 8.68 0.48 4 0 8.95 0.22 4 0

307 Tualatin River at RM 9.9 

(Cook Park)

Suspended sediment – 06-03-00 -35.07 0.17 3 9.50 0.08 3 0 7.82 0.35 3 0

308 Tualatin River at RM 9.9 

(Cook Park)

Bed sediment – 06-03-00 -28.67 0.40 3 5.27 0.62 3 3 15.79 0.74 3 3

309 Tualatin River at RM 9.9 

(Cook Park)

Duckweed Decomposed duckweed 06-03-00 -28.73 0.88 4 7.08 1.63 3 0 12.73 0.54 4 0

310 Tualatin River at RM 9.4 

(Basalt sill)

Periphyton Cladophera 06-03-00 -36.21 0.04 4 6.81 0.27 4 0 9.66 0.32 4 0

311 Tualatin River at RM 8.7 

(Boones Ferry Bridge)

Seston, >80 μm – 06-03-00 -32.61 0.18 3 9.99 0.13 3 0 9.56 0.20 3 0

312 Tualatin River at RM 8.7 

(Boones Ferry Bridge)

Seston, 80–202 μm – 06-03-00 -32.64 0.06 3 9.15 0.64 3 0 10.17 0.27 3 0

313 Tualatin River at RM 8.7 

(Boones Ferry Bridge)

Suspended sediment – 06-03-00 -35.22 0.97 3 11.46 1.08 3 3 7.70 0.10 3 0

314 Tualatin River at RM 8.7 

(Boones Ferry Bridge)

Bed sediment – 06-03-00 -28.81 0.16 3 5.92 0.34 3 3 15.49 0.94 3 3

315 Tualatin River at RM 20.3 Seston, >80 μm – 06-05-00 -29.61 0.29 3 8.04 0.93 3 0 15.27 1.37 3 0316 Tualatin River at RM 20.3 Seston, 80–202 μm – 06-05-00 -29.77 0.02 4 7.63 0.69 4 0 15.43 0.40 4 0317 Tualatin River at RM 20.3 Suspended sediment – 06-05-00 -32.55 0.32 3 8.77 0.12 3 0 10.20 0.18 3 0318 Tualatin River at RM 20.3 Bed sediment – 06-05-00 -28.29 0.20 3 5.47 0.29 3 0 15.09 0.49 3 0319 Tualatin River at RM 16.2 (Elsner 

Bridge)

Suspended sediment – 06-02-00 -30.24 0.48 3 10.63 1.35 3 0 12.93 0.56 3 0

320 Tualatin River at RM 16.2 (Elsner 

Bridge)

Seston, >80 μm – 06-02-00 -29.21 0.34 3 10.25 0.25 3 0 12.99 1.08 3 0

Table 6. Mean values and confidence intervals of stable isotope compositions (δ13C, δ15N) and C/N ratios for samples collected in the Tualatin River basin, Oregon.—Continued[Abbreviations: RM, river mile; n, number of splits used in calculation of mean and confidence interval; 95% CI, 95-percent confidence limit of mean; low-N n, number of splits that contained less than 1 micromole N; 1-sf n, number of splits in which the percent nitrogen value had only 1 significant digit; WWTF, wastewater treatment facililty; μm, micrometer; na, not applicable]
Table 6 33

ID Site name Sample type Sample detail Date

δ13C δ15N C/N atomic ratio

Mean 95%CI n Mean 95%CI n low-N 

n

Mean 95%CI n 1-sf 

n

Early-Summer 2000—Continued

321 Tualatin River at RM 16.2 (Elsner 

Bridge)

Seston, 80–202 μm – 06-02-00 -31.62 0.18 3 10.37 0.77 3 2 10.99 0.15 3 0

322 Tualatin River at RM 16.2 (Elsner 

Bridge)

Bed sediment – 06-02-00 -27.93 0.44 3 5.22 0.13 3 0 15.17 1.27 3 0

323 Tualatin River at RM 26.9 

(Scholls)

Seston, >80 μm – 06-02-00 -28.93 0.13 4 6.23 0.57 4 2 17.79 0.30 4 0

324 Tualatin River at RM 26.9 

(Scholls)

Seston, 80–202 μm – 06-02-00 -29.11 0.07 3 5.55 1.47 3 3 17.81 0.25 3 0

325 Tualatin River at RM 26.9 

(Scholls)

Suspended sediment – 06-02-00 -31.13 0.66 3 7.05 0.08 3 0 6.94 0.69 3 0

326 Tualatin River at RM 26.9 

(Scholls)

Bed sediment – 06-02-00 -27.80 0.55 4 5.26 0.27 4 0 9.48 1.32 4 0

327 Tualatin River at RM 5.5 

(Stafford Road)

Suspended sediment – 06-02-00 -33.51 0.44 3 12.10 0.29 3 0 10.63 0.44 3 0

328 Tualatin River at RM 5.5 

(Stafford Road)

Seston, >80 μm – 06-02-00 -37.81 0.23 3 13.58 0.22 3 0 7.51 0.02 3 0

329 Tualatin River at RM 5.5 

(Stafford Road)

Seston, 80–202 μm – 06-02-00 -37.99 0.20 3 13.74 0.10 3 0 7.14 0.13 3 0

330 Tualatin River at RM 5.5 

(Stafford Road)

Bed sediment – 06-02-00 -28.15 0.16 4 5.77 0.23 4 0 9.22 0.57 3 0

331 Gales Creek at Old Highway 47 Suspended sediment – 05-31-00 -29.72 0.10 3 3.02 0.44 3 0 9.68 1.20 3 0332 Gales Creek at Old Highway 47 Bed sediment – 05-31-00 -27.61 0.23 3 1.72 0.29 3 0 12.64 3.63 3 0333 Tualatin River at RM 58.8 

(Dilley)

Suspended sediment – 05-31-00 -30.62 0.59 4 4.64 0.20 4 0 10.50 0.39 4 0

334 Tualatin River at RM 58.8 

(Dilley)

Bed sediment – 05-31-00 -27.77 0.17 3 2.48 0.21 3 0 13.10 3.56 3 0

335 Dairy Creek at Highway 8 Suspended sediment – 05-31-00 -31.34 0.14 3 3.71 0.02 3 0 8.94 3.36 3 0336 Dairy Creek at Highway 8 Bed sediment – 05-31-00 -27.77 0.11 4 3.69 0.26 4 0 18.09 2.05 4 0337 Dairy Creek at Highway 8 Grass Grass growing in stream 05-31-00 -31.09 0.13 3 4.64 0.15 3 0 16.92 1.35 3 0338 Rock Creek at Highway 8 Suspended sediment – 05-31-00 -32.01 0.15 3 5.61 0.14 3 0 7.71 1.27 3 0339 Rock Creek at Highway 8 Bed sediment – 05-31-00 -28.79 0.29 3 5.56 0.03 3 0 17.31 1.47 3 0340 Rock Creek at Highway 8 Periphyton Species not identified 05-31-00 -42.84 0.22 4 3.54 0.03 4 0 8.08 0.08 4 0

Table 6. Mean values and confidence intervals of stable isotope compositions (δ13C, δ15N) and C/N ratios for samples collected in the Tualatin River basin, Oregon.—Continued[Abbreviations: RM, river mile; n, number of splits used in calculation of mean and confidence interval; 95% CI, 95-percent confidence limit of mean; low-N n, number of splits that contained less than 1 micromole N; 1-sf n, number of splits in which the percent nitrogen value had only 1 significant digit; WWTF, wastewater treatment facililty; μm, micrometer; na, not applicable]
34 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon ID Site name Sample type Sample detail Date

δ13C δ15N C/N atomic ratio

Mean 95%CI n Mean 95%CI n low-N 

n

Mean 95%CI n 1-sf 

n

Early-Summer 2000—Continued

341 Rock Creek at Highway 8 Decomposed terrestrial 

detritus

Decomposed non-woody 

plant material in stream

05-31-00 -28.92 1.24 3 5.00 0.07 3 0 23.13 2.41 3 0

342 Fanno Creek at Durham 

City Park

Suspended sediment – 05-31-00 -31.82 0.18 3 4.43 0.46 3 0 8.86 0.68 3 0

343 Fanno Creek at Durham 

City Park

Bed sediment – 05-31-00 -28.58 0.49 4 4.13 0.19 4 0 13.00 1.40 4 0

344 Rock Creek Wastewater 

Treatment Facility

WWTF effluent particulate – 06-01-00 -27.41 0.77 3 10.14 0.21 3 2 8.04 2.83 3 2

345 Durham Wastewater Treatment 

Facility

WWTF effluent particulate – 06-01-00 -27.94 1.18 3 7.15 0.60 3 0 7.44 0.89 3 2

Table 6. Mean values and confidence intervals of stable isotope compositions (δ13C, δ15N) and C/N ratios for samples collected in the Tualatin River basin, Oregon.—Continued[Abbreviations: RM, river mile; n, number of splits used in calculation of mean and confidence interval; 95% CI, 95-percent confidence limit of mean; low-N n, number of splits that contained less than 1 micromole N; 1-sf n, number of splits in which the percent nitrogen value had only 1 significant digit; WWTF, wastewater treatment facililty; μm, micrometer; na, not applicable]
Appendix A 35

Appendix A.
36 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon ID Site name Sample type Sample detail Date Sample split Lab rep Acidified δ13C δ15N δ15N qualifier C/N C/N qualifier

1 Henry Hagg Lake Seston, >80 μm

— 07-09-99

A 0 A -28.87 7.54 3.86

1 Henry Hagg Lake Seston, >80 μm

— 07-09-99

A 0 U -29.37 6.76 4.86

1 Henry Hagg Lake Seston, >80 μm

— 07-09-99

B 0 U -28.79 6.86 5.04

1 Henry Hagg Lake Seston, >80 μm

— 07-09-99

C 0 U -29.20 6.99 4.80

2 Henry Hagg Lake Seston, 80–202 μm

— 07-09-99

A 0 U -28.70 6.58 5.00

Henry Hagg Lake Seston, 80–202 μm

— 07-09-99

B 0 U -28.97 6.02 5.08

2 Henry Hagg Lake Seston, 80–202 μm

— 07-09-99

C 0 U -29.05 6.40 4.91

3 Tualatin River at RM 20.3 Seston, >80 μm

— 07-14-99

A 0 A -30.39 7.50 9.83

3 Tualatin River at RM 20.3 Seston, >80 μm

— 07-14-99

B 0 A -30.56 7.93 9.51

3 Tualatin River at RM 20.3 Seston, >80 μm

— 07-14-99

C 0 A -30.43 7.88 9.85

4 Tualatin River at RM 20.3 Seston, 80–202 μm

— 07-14-99

A 0 A -30.55 8.05 9.36

4 Tualatin River at RM 20.3 Seston, 80–202 μm

— 07-14-99

B 0 A -30.79 8.35 8.01

4 Tualatin River at RM 20.3 Seston, 80–202 μm

— 07-14-99

B 0 U -30.77 6.80 9.17

4 Tualatin River at RM 20.3 Seston, 80–202 μm

— 07-14-99

C 0 A -30.67 7.81 8.42

5 Tualatin River at RM 20.3 Duckweed Duckweed sorted from mat 07-14-99

A 0 A -28.57 10.61 12.44

5 Tualatin River at RM 20.3 Duckweed Duckweed sorted from mat 07-14-99

B 0 A -28.65 10.37 12.36

5 Tualatin River at RM 20.3 Duckweed Duckweed sorted from mat 07-14-99

C 0 A -28.72 10.47 12.76

6 Tualatin River at RM 20.3 Woody material Twigs sorted from 

duckweed mat

07-14-99

A 0 A -28.54 2.75 30.02

6 Tualatin River at RM 20.3 Woody material Twigs sorted from 

duckweed mat

07-14-99

B 0 A -29.29 2.57 25.91

6 Tualatin River at RM 20.3 Woody material Twigs sorted from 

duckweed mat

07-14-99

C 0 A -29.26 2.64 25.38

7 Tualatin River at RM 20.3 Suspended sediment

— 07-14-99

A 0 A -31.92 9.03 6.45

7 Tualatin River at RM 20.3 Suspended sediment

— 07-14-99

B 0 A -32.36 8.93 6.64

7 Tualatin River at RM 20.3 Suspended sediment

— 07-14-99

B 1 A -32.27 8.99 6.20

7 Tualatin River at RM 20.3 Suspended sediment

— 07-14-99

C 0 A -32.41 9.02 6.81

8 Tualatin River at RM 20.3 Bed sediment

— 07-14-99

A 0 A -27.39 6.33 12.37

E

8 Tualatin River at RM 20.3 Bed sediment

— 07-14-99

B 0 A -27.50 4.94 12.00

E

8 Tualatin River at RM 20.3 Bed sediment

— 07-14-99

C 0 A -27.50

— 13.36

E

10 Tualatin River at RM 20.3 Coniferous litter Cones sorted from 

duckweed mat

07-14-99

A 0 A -27.37 2.08

L 104.6

10 Tualatin River at RM 20.3 Coniferous litter Cones sorted from 

duckweed mat

07-14-99

B 0 A -27.35 -0.16

L 83.38

Appendix A. Values of stable isotope compositions (δ13C, δ15N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split samples.[Sample splits are marked with letter codes (A, B, C, etc) simply to label the replicates. Lab Rep is the replicate number (0, 1, 2, etc) for analyses performed on each sample split. The Acidified code is either A for acidified or U for unacidified. The δ values are in per mil. The δ15N qualifier is listed as L if the total nitrogen mass in the sample was less than 1 micromole. The C/N qualifier is listed as E if the percent nitrogen result had only one significant digit. Abbreviations: RM, river mile; —, no result or no sample detail; cm, centimeter]
Appendix A. 37

ID Site name Sample type Sample detail Date Sample split Lab rep Acidified δ13C δ15N δ15N qualifier C/N C/N qualifier

10 Tualatin River at RM 20.3 Coniferous litter Cones sorted from 

duckweed mat

07-14-99 C 0 A -27.03 -1.43 L 96.36

12 Tualatin River at RM 20.3 Leaf litter Oregon Ash seed pods from 

river surface

07-14-99 A 0 A -25.51 1.61 44.30

12 Tualatin River at RM 20.3 Leaf litter Oregon Ash seed pods from 

river surface

07-14-99 B 0 A -25.83 1.02 L 66.21

12 Tualatin River at RM 20.3 Leaf litter Oregon Ash seed pods from 

river surface

07-14-99 C 0 A -25.29 2.00 57.21

12 Tualatin River at RM 20.3 Leaf litter Oregon Ash seed pods from 

river surface

07-14-99 C 1 A -25.56 1.41 54.73

13 Tualatin River at RM 20.3 Leaf litter Oregon Ash leaves from 

river surface

07-14-99 A 0 A -27.08 1.02 24.90

13 Tualatin River at RM 20.3 Leaf litter Oregon Ash leaves from 

river surface

07-14-99 B 0 A -27.27 0.98 26.83

13 Tualatin River at RM 20.3 Leaf litter Oregon Ash leaves from 

river surface

07-14-99 C 0 A -26.84 0.65 27.89

14 Tualatin River at RM 26.9 (Scholls) Seston, >80 μm — 07-14-99 A 0 A -28.50 6.38 15.4014 Tualatin River at RM 26.9 (Scholls) Seston, >80 μm — 07-14-99 B 0 A -28.59 6.89 13.5514 Tualatin River at RM 26.9 (Scholls) Seston, >80 μm — 07-14-99 C 0 A -28.45 6.74 13.5915 Tualatin River at RM 26.9 (Scholls) Seston, 80–202 μm — 07-14-99 A 0 A -28.37 6.01 L 14.9115 Tualatin River at RM 26.9 (Scholls) Seston, 80–202 μm — 07-14-99 B 0 A -28.25 6.20 14.5715 Tualatin River at RM 26.9 (Scholls) Seston, 80–202 μm — 07-14-99 C 0 A -28.18 6.51 L 14.8416 Tualatin River at RM 26.9 (Scholls) Suspended sediment — 07-14-99 A 0 A -28.33 6.27 L 8.5916 Tualatin River at RM 26.9 (Scholls) Suspended sediment — 07-14-99 A 1 A -28.47 6.28 L 8.6416 Tualatin River at RM 26.9 (Scholls) Suspended sediment — 07-14-99 B 0 A -28.80 7.26 7.7216 Tualatin River at RM 26.9 (Scholls) Suspended sediment — 07-14-99 C 0 A -28.60 7.40 7.5417 Tualatin River at RM 26.9 (Scholls) Bed sediment — 07-14-99 A 0 A -27.28 5.95 12.4017 Tualatin River at RM 26.9 (Scholls) Bed sediment — 07-14-99 B 0 A -27.59 6.19 13.6817 Tualatin River at RM 26.9 (Scholls) Bed sediment — 07-14-99 C 0 A -27.67 5.52 11.8018 Tualatin River at RM 26.9 (Scholls) Duckweed Duckweed sorted from mat 07-14-99 A 0 A -28.48 9.32 10.2819 Tualatin River at RM 26.9 (Scholls) Woody material Twigs sorted from 

duckweed mat

07-14-99 A 0 A -25.92 5.76 24.79

19 Tualatin River at RM 26.9 (Scholls) Woody material Twigs sorted from 

duckweed mat

07-14-99 B 0 A -26.67 5.38 24.11

19 Tualatin River at RM 26.9 (Scholls) Woody material Twigs sorted from 

duckweed mat

07-14-99 C 0 A -26.75 4.94 23.90

Appendix A. Values of stable isotope compositions (δ13C, δ15N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split samples.—Continued
38 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon Appendix A. Values of stable isotope compositions (δ13C, δ15N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split samples.—Continued ID Site name Sample type Sample detail Date Sample split Lab rep Acidified δ13C δ15N δ15N qualifier C/N C/N qualifier 20 Tualatin River at RM 38.4 (Rood Bridge) Suspended sediment

— 07-14-99

A 0 A -28.10 6.48 8.92

20 Tualatin River at RM 38.4 (Rood Bridge) Suspended sediment

— 07-14-99

A 1 A -28.06 6.31 9.10

20 Tualatin River at RM 38.4 (Rood Bridge) Suspended sediment

— 07-14-99

B 0 A -28.24 6.31 8.89

20 Tualatin River at RM 38.4 (Rood Bridge) Suspended sediment

— 07-14-99

C 0 A -28.17 6.57 9.04

21 Tualatin River at RM 38.4 (Rood Bridge) Bed sediment

— 07-14-99

A 0 A -26.46 5.01 12.11

E

21 Tualatin River at RM 38.4 (Rood Bridge) Bed sediment

— 07-14-99

B 0 A -26.84 4.94 11.38

E

21 Tualatin River at RM 38.4 (Rood Bridge) Bed sediment

— 07-14-99

C 0 A -26.93 4.47 11.63

E

22 Gales Creek at old Hwy 47 Suspended sediment

— 07-16-99

A 0 A -26.32 4.59 7.68

22 Gales Creek at old Hwy 47 Suspended sediment

— 07-16-99

B 0 A -26.47 4.80 7.17

22 Gales Creek at old Hwy 47 Suspended sediment

— 07-16-99

C 0 A -26.38 4.40 7.27

23 Gales Creek at old Hwy 47 Bed sediment

— 07-16-99

A 0 A -27.08 2.31

L 11.01

E

23 Gales Creek at old Hwy 47 Bed sediment

— 07-16-99

A 0 U -27.28 2.36

L 15.33

E

23 Gales Creek at old Hwy 47 Bed sediment

— 07-16-99

B 0 A -27.19 2.51

L 13.98

E

23 Gales Creek at old Hwy 47 Bed sediment

— 07-16-99

C 0 A -27.04 3.29

L 9.78

E

24 Dairy Creek at Hwy 8 Suspended sediment

— 07-16-99

A 0 A -29.51 6.26 7.97

24 Dairy Creek at Hwy 8 Suspended sediment

— 07-16-99

B 0 A -29.56 6.10 7.56

24 Dairy Creek at Hwy 8 Suspended sediment

— 07-16-99

C 0 A -29.70 6.13 7.37

25 Dairy Creek at Hwy 8 Bed sediment

— 07-16-99

A 0 A -27.04 4.24

L 12.99

E

25 Dairy Creek at Hwy 8 Bed sediment

— 07-16-99

B 0 A -26.63 4.37 15.18

E

25 Dairy Creek at Hwy 8 Bed sediment

— 07-16-99

C 0 A -27.08

— 14.26

E

26 Tualatin River at RM 58.8 (Dilley) Suspended sediment

— 07-16-99

A 0 A -27.31 3.72

L 11.01

E

26 Tualatin River at RM 58.8 (Dilley) Suspended sediment

— 07-16-99

B 0 A -27.87 4.13

L 8.18

E

26 Tualatin River at RM 58.8 (Dilley) Suspended sediment

— 07-16-99

C 0 A -27.72 4.44

L 9.29

E

27 Tualatin River at RM 58.8 (Dilley) Bed sediment

— 07-16-99

A 0 A -26.86 2.76

L 11.76

E

27 Tualatin River at RM 58.8 (Dilley) Bed sediment

— 07-16-99

B 0 A -27.20 2.97

L 13.73

E

27 Tualatin River at RM 58.8 (Dilley) Bed sediment

— 07-16-99

C 0 A -27.12 2.39

L 13.98

E

28 Rock Creek at Hwy 8 Suspended sediment

— 07-16-99

A 0 A -29.16 4.17

L 9.40

28 Rock Creek at Hwy 8 Suspended sediment

— 07-16-99

B 0 A -29.08 5.75 8.90

28 Rock Creek at Hwy 8 Suspended sediment

— 07-16-99

C 0 A -29.40 5.73 8.21

29 Rock Creek at Hwy 8 Bed sediment

— 07-16-99

A 0 A -27.99 6.01 12.84

29 Rock Creek at Hwy 8 Bed sediment

— 07-16-99

B 0 A -27.90 5.42 13.37
Appendix A. 39

Appendix A. Values of stable isotope compositions (δ13C, δ15N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split samples.—Continued

ID Site name Sample type Sample detail Date Sample split Lab rep Acidified δ13C δ15N δ15N qualifier C/N C/N qualifier

29 Rock Creek at Hwy 8 Bed sediment — 07-16-99 C 0 A -28.04 6.00 13.1530 Tualatin River at RM 5.5 (Stafford Road) Suspended sediment — 07-16-99 A 0 A -35.30 9.19 5.0730 Tualatin River at RM 5.5 (Stafford Road) Suspended sediment — 07-16-99 B 0 A -35.45 9.28 4.8930 Tualatin River at RM 5.5 (Stafford Road) Suspended sediment — 07-16-99 C 0 A -35.49 8.86 4.9231 Tualatin River at RM 5.5 (Stafford Road) Seston, >80 μm — 07-19-99 A 0 A -37.36 9.13 4.9631 Tualatin River at RM 5.5 (Stafford Road) Seston, >80 μm — 07-19-99 B 0 A -37.60 8.95 5.1031 Tualatin River at RM 5.5 (Stafford Road) Seston, >80 μm — 07-19-99 C 0 A -37.43 8.96 5.0532 Tualatin River at RM 5.5 (Stafford Road) Seston, 80–202 μm — 07-19-99 A 0 A -37.64 8.71 5.0132 Tualatin River at RM 5.5 (Stafford Road) Seston, 80–202 μm — 07-19-99 A 0 U -37.61 9.08 5.4732 Tualatin River at RM 5.5 (Stafford Road) Seston, 80–202 μm — 07-19-99 B 0 A -37.63 9.46 4.9732 Tualatin River at RM 5.5 (Stafford Road) Seston, 80–202 μm — 07-19-99 C 0 A -37.69 9.63 4.8433 Tualatin River at RM 5.5 (Stafford Road) Bed sediment — 07-19-99 A 0 A -27.29 — 11.4833 Tualatin River at RM 5.5 (Stafford Road) Bed sediment — 07-19-99 A 0 U -26.81 6.42 9.0233 Tualatin River at RM 5.5 (Stafford Road) Bed sediment — 07-19-99 B 0 A -28.06 5.15 10.2533 Tualatin River at RM 5.5 (Stafford Road) Bed sediment — 07-19-99 C 0 A -27.49 5.63 11.6034 Tualatin River at RM 5.5 (Stafford Road) Periphyton Spirogyra 07-19-99 A 0 A -17.25 7.02 9.1534 Tualatin River at RM 5.5 (Stafford Road) Periphyton Spirogyra 07-19-99 A 1 A -17.49 6.61 9.1534 Tualatin River at RM 5.5 (Stafford Road) Periphyton Spirogyra 07-19-99 B 0 A -17.33 6.97 9.0535 Tualatin River at RM 9.9 (Cook Park) Seston, >80 μm — 07-19-99 A 0 A -34.95 8.15 6.1035 Tualatin River at RM 9.9 (Cook Park) Seston, >80 μm — 07-19-99 B 0 A -35.04 8.32 6.4735 Tualatin River at RM 9.9 (Cook Park) Seston, >80 μm — 07-19-99 C 0 A -35.17 8.28 6.1736 Tualatin River at RM 9.9 (Cook Park) Seston, 80–202 μm — 07-19-99 A 0 A -35.10 8.60 L 5.7836 Tualatin River at RM 9.9 (Cook Park) Seston, 80–202 μm — 07-19-99 B 0 A -34.78 9.38 L 5.7836 Tualatin River at RM 9.9 (Cook Park) Seston, 80–202 μm — 07-19-99 C 0 A -35.09 9.32 L 6.2337 Tualatin River at RM 9.9 (Cook Park) Suspended sediment — 07-19-99 A 0 A -34.95 7.34 5.7237 Tualatin River at RM 9.9 (Cook Park) Suspended sediment — 07-19-99 A 0 U — 6.82 6.9137 Tualatin River at RM 9.9 (Cook Park) Suspended sediment — 07-19-99 B 0 A -35.10 7.71 5.6037 Tualatin River at RM 9.9 (Cook Park) Suspended sediment — 07-19-99 C 0 A -34.97 — 5.5437 Tualatin River at RM 9.9 (Cook Park) Suspended sediment — 07-19-99 C 1 A -34.89 — 5.6238 Tualatin River at RM 9.9 (Cook Park) Bed sediment — 07-19-99 A 0 U -28.15 5.73 L 10.50 E38 Tualatin River at RM 9.9 (Cook Park) Bed sediment — 07-19-99 A 1 U -28.44 5.46 L 13.00 E38 Tualatin River at RM 9.9 (Cook Park) Bed sediment — 07-19-99 B 0 U -28.34 5.86 L 10.67 E38 Tualatin River at RM 9.9 (Cook Park) Bed sediment — 07-19-99 B 1 U -27.87 5.11 L 13.80 E
40 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon Appendix A. Values of stable isotope compositions (δ13C, δ15N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split samples.—Continued ID Site name Sample type Sample detail Date Sample split Lab rep Acidified δ13C δ15N δ15N qualifier C/N C/N qualifier 38 Tualatin River at RM 9.9 (Cook Park) Bed sediment

— 07-19-99

C 0 U -28.22 5.23

L 12.40

E

38 Tualatin River at RM 9.9 (Cook Park) Bed sediment

— 07-19-99

C 1 U -27.95 5.51

L 11.50

E

39 Tualatin River at RM 9.9 (Cook Park) Duckweed Unsorted duckweed mat 07-19-99

A 0 A -28.69 3.49 23.63

39 Tualatin River at RM 9.9 (Cook Park) Duckweed Unsorted duckweed mat 07-19-99

A 0 U -28.68 2.91 24.33

39 Tualatin River at RM 9.9 (Cook Park) Duckweed Unsorted duckweed mat 07-19-99

B 0 A -28.18 3.24 22.68

39 Tualatin River at RM 9.9 (Cook Park) Duckweed Unsorted duckweed mat 07-19-99

C 0 A -28.46 3.15 22.64

40 Tualatin River at RM 9.9 (Cook Park) Duckweed Duckweed sorted from mat 07-19-99

A 0 A -29.89 6.96 9.68

40 Tualatin River at RM 9.9 (Cook Park) Duckweed Duckweed sorted from mat 07-19-99

B 0 A -29.83 6.85 9.64

40 Tualatin River at RM 9.9 (Cook Park) Duckweed Duckweed sorted from mat 07-19-99

C 0 A -29.83 6.88 9.60

41 Tualatin River at RM 9.9 (Cook Park) Woody material Twigs sorted from 

duckweed mat

07-19-99

A 0 A -25.80 2.14 25.75

41 Tualatin River at RM 9.9 (Cook Park) Woody material Twigs sorted from 

duckweed mat

07-19-99

A 1 A -27.60 2.20 26.34

41 Tualatin River at RM 9.9 (Cook Park) Woody material Twigs sorted from 

duckweed mat

07-19-99

A 0 U -29.11 2.32 25.56

41 Tualatin River at RM 9.9 (Cook Park) Woody material Twigs sorted from 

duckweed mat

07-19-99

A 1 U -28.31 2.25 25.32

41 Tualatin River at RM 9.9 (Cook Park) Woody material Twigs sorted from 

duckweed mat

07-19-99

B 0 A -28.24 2.59 25.61

41 Tualatin River at RM 9.9 (Cook Park) Woody material Twigs sorted from 

duckweed mat

07-19-99

C 0 A -27.86 2.30 25.50

42 Tualatin River at RM 9.9 (Cook Park) Coniferous litter Cones sorted from 

duckweed mat

07-19-99

A 0 A -26.57 1.19

L 77.20

42 Tualatin River at RM 9.9 (Cook Park) Coniferous litter Cones sorted from 

duckweed mat

07-19-99

B 0 A -26.57 0.60

L 84.49

42 Tualatin River at RM 9.9 (Cook Park) Coniferous litter Cones sorted from 

duckweed mat

07-19-99

C 0 A -26.52 0.36

L 71.08

43 Tualatin River at RM 9.9 (Cook Park) Soil A-horizon from bank with 

slump

07-19-99

A 0 A -26.03 1.02 26.91

43 Tualatin River at RM 9.9 (Cook Park) Soil A-horizon from bank with 

slump

07-19-99

B 0 A -26.04 1.15 24.73

43 Tualatin River at RM 9.9 (Cook Park) Soil A-horizon from bank with 

slump

07-19-99

C 0 A -26.24 1.98 25.30

44 Tualatin River at RM 9.9 (Cook Park) Soil Bottom of slump at water 

edge

07-19-99

A 0 U -27.29 4.02

L 11.50

E

44 Tualatin River at RM 9.9 (Cook Park) Soil Bottom of slump at water 

edge

07-19-99

B 0 U -27.03 6.95

L 10.00

E
Appendix A. 41

Appendix A. Values of stable isotope compositions (δ13C, δ15N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split samples.—Continued

ID Site name Sample type Sample detail Date Sample split Lab rep Acidified δ13C δ15N δ15N qualifier C/N C/N qualifier

44 Tualatin River at RM 9.9 (Cook Park) Soil Bottom of slump at water 

edge

07-19-99 C 0 U -27.03 4.88 L 13.00 E

44 Tualatin River at RM 9.9 (Cook Park) Soil Bottom of slump at water 

edge

07-19-99 C 1 U — 5.30 L 14.50 E

45 Tualatin River at RM 8.7 (Boones Ferry Bridge) Seston, >80 μm — 07-19-99 A 0 A -34.90 10.23 6.4945 Tualatin River at RM 8.7 (Boones Ferry Bridge) Seston, >80 μm — 07-19-99 B 0 A -34.98 10.64 6.5145 Tualatin River at RM 8.7 (Boones Ferry Bridge) Seston, >80 μm — 07-19-99 C 0 A -34.75 10.87 6.5646 Tualatin River at RM 8.7 (Boones Ferry Bridge) Seston, 80–202 μm — 07-19-99 A 0 A -34.94 10.43 L 6.9546 Tualatin River at RM 8.7 (Boones Ferry Bridge) Seston, 80–202 μm — 07-19-99 B 0 A -34.89 10.92 L 6.4546 Tualatin River at RM 8.7 (Boones Ferry Bridge) Seston, 80–202 μm — 07-19-99 C 0 A -34.67 11.30 L 6.2747 Tualatin River at RM 8.7 (Boones Ferry Bridge) Suspended sediment — 07-19-99 A 0 A -35.68 11.72 6.0847 Tualatin River at RM 8.7 (Boones Ferry Bridge) Suspended sediment — 07-19-99 B 0 A -35.87 11.80 6.0847 Tualatin River at RM 8.7 (Boones Ferry Bridge) Suspended sediment — 07-19-99 C 0 A -35.86 12.66 5.9547 Tualatin River at RM 8.7 (Boones Ferry Bridge) Suspended sediment — 07-19-99 C 1 A -35.88 12.57 5.7548 Tualatin River at RM 8.7 (Boones Ferry Bridge) Bed sediment — 07-19-99 A 0 A -27.08 7.07 L 10.03 E48 Tualatin River at RM 8.7 (Boones Ferry Bridge) Bed sediment — 07-19-99 A 0 U -27.68 5.83 L 12.00 E48 Tualatin River at RM 8.7 (Boones Ferry Bridge) Bed sediment — 07-19-99 B 0 A -27.78 4.76 L 12.00 E48 Tualatin River at RM 8.7 (Boones Ferry Bridge) Bed sediment — 07-19-99 C 0 A -28.81 4.60 L 13.19 E49 Tualatin River at RM 16.2 (Elsner Bridge) Suspended sediment Fraction that settled after 

24 hours

07-21-99 A 0 A -29.86 6.36 7.07

49 Tualatin River at RM 16.2 (Elsner Bridge) Suspended sediment Fraction that settled after 

24 hours

07-21-99 B 0 A -29.52 — 7.67

49 Tualatin River at RM 16.2 (Elsner Bridge) Suspended sediment Fraction that settled after 

24 hours

07-21-99 B 0 U -30.45 5.30 8.31

49 Tualatin River at RM 16.2 (Elsner Bridge) Suspended sediment Fraction that settled after 

24 hours

07-21-99 C 0 A -29.33 5.01 8.02

50 Tualatin River at RM 16.2 (Elsner Bridge) Seston, >80 μm Aphanizomenon floating on 

sample

07-21-99 A 0 A -34.35 7.68 3.91

50 Tualatin River at RM 16.2 (Elsner Bridge) Seston, >80 μm Aphanizomenon floating on 

sample

07-21-99 B 0 A -34.62 7.77 3.44

50 Tualatin River at RM 16.2 (Elsner Bridge) Seston, >80 μm Aphanizomenon floating on 

sample

07-21-99 C 0 A -34.29 7.30 3.89

51 Tualatin River at RM 16.2 (Elsner Bridge) Seston, >80 μm — 07-21-99 A 0 A -29.63 — 9.8651 Tualatin River at RM 16.2 (Elsner Bridge) Seston, >80 μm — 07-21-99 A 1 A -29.80 — 10.5751 Tualatin River at RM 16.2 (Elsner Bridge) Seston, >80 μm — 07-21-99 A 0 U -29.96 — 10.54
42 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon Appendix A. Values of stable isotope compositions (δ13C, δ15N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split samples.—Continued ID Site name Sample type Sample detail Date Sample split Lab rep Acidified δ13C δ15N δ15N qualifier C/N C/N qualifier 51 Tualatin River at RM 16.2 (Elsner Bridge) Seston, >80 μm

— 07-21-99

B 0 A -29.26

— 11.19

51 Tualatin River at RM 16.2 (Elsner Bridge) Seston, >80 μm

— 07-21-99

C 0 A -28.88

— 11.07

51 Tualatin River at RM 16.2 (Elsner Bridge) Seston, >80 μm

— 07-21-99

C 0 U -29.06

— 10.00

51 Tualatin River at RM 16.2 (Elsner Bridge) Seston, >80 μm

— 07-21-99

C 1 U -28.96

—

L 10.88

52 Tualatin River at RM 16.2 (Elsner Bridge) Seston, 80–202 μm

— 07-21-99

A 0 A -30.41 5.43

L 8.36

52 Tualatin River at RM 16.2 (Elsner Bridge) Seston, 80–202 μm

— 07-21-99

B 0 A -30.20 6.34

L 8.53

52 Tualatin River at RM 16.2 (Elsner Bridge) Seston, 80–202 μm

— 07-21-99

C 0 A -30.73 6.17

L 9.00

53 Tualatin River at RM 16.2 (Elsner Bridge) Bed sediment

— 07-21-99

A 0 A -27.28 4.95

L 16.80

E

53 Tualatin River at RM 16.2 (Elsner Bridge) Bed sediment

— 07-21-99

B 0 A -26.66 5.53 14.47

E

53 Tualatin River at RM 16.2 (Elsner Bridge) Bed sediment

— 07-21-99

C 0 A -27.59 5.11 12.50

E

54 Tualatin River at RM 16.2 (Elsner Bridge) Woody material Twigs removed from bed 

sediment

07-21-99

A 0 A -26.61 4.70

L 78.38

54 Tualatin River at RM 16.2 (Elsner Bridge) Woody material Twigs removed from bed 

sediment

07-21-99

B 0 A -27.34 4.23

L

—

54 Tualatin River at RM 16.2 (Elsner Bridge) Woody material Twigs removed from bed 

sediment

07-21-99

B 1 A -27.45 4.86

L

—

54 Tualatin River at RM 16.2 (Elsner Bridge) Woody material Twigs removed from bed 

sediment

07-21-99

C 0 A -26.64 4.45

L 79.05

55 Fanno Creek at Durham City Park Suspended sediment Fraction that settled after 

24 hours

07-21-99

A 0 A -28.89 5.57 11.34

55 Fanno Creek at Durham City Park Suspended sediment Fraction that settled after 

24 hours

07-21-99

A 0 U -29.55 5.79 11.33

55 Fanno Creek at Durham City Park Suspended sediment Fraction that settled after 

24 hours

07-21-99

B 0 A -28.63 4.26 12.05

55 Fanno Creek at Durham City Park Suspended sediment Fraction that settled after 

24 hours

07-21-99

C 0 A -28.95 3.67 11.63

56 Fanno Creek at Durham City Park Seston, >80 μm

— 07-21-99

A 0 A -28.42 7.52

L 10.13

56 Fanno Creek at Durham City Park Seston, >80 μm

— 07-21-99

A 0 U -29.50 7.01

L 10.70

56 Fanno Creek at Durham City Park Seston, >80 μm

— 07-21-99

B 0 A -28.52 5.95

L 11.21

56 Fanno Creek at Durham City Park Seston, >80 μm

— 07-21-99

C 0 A -28.24 5.26

L 12.86

56 Fanno Creek at Durham City Park Seston, >80 μm

— 07-21-99

C 0 U -29.59 6.79

L 10.15

56 Fanno Creek at Durham City Park Seston, >80 μm

— 07-21-99

C 1 U -28.16 5.05

L 12.12

57 Fanno Creek at Durham City Park Seston, 80–202 μm

— 07-21-99

A 0 A -28.19 5.17

L 12.17

57 Fanno Creek at Durham City Park Seston, 80–202 μm

— 07-21-99

B 0 A -28.35 5.50

L 12.63

57 Fanno Creek at Durham City Park Seston, 80–202 μm

— 07-21-99

C 0 A -28.69 5.46

L 12.30
Appendix A. 43

Appendix A. Values of stable isotope compositions (δ13C, δ15N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split samples.—Continued

ID Site name Sample type Sample detail Date Sample split Lab rep Acidified δ13C δ15N δ15N qualifier C/N C/N qualifier

58 Fanno Creek at Durham City Park Bed sediment — 07-21-99 A 0 A -27.81 4.14 L 11.01 E58 Fanno Creek at Durham City Park Bed sediment — 07-21-99 B 0 A -28.05 3.83 L 12.50 E58 Fanno Creek at Durham City Park Bed sediment — 07-21-99 C 0 A -28.11 3.01 L 15.95 E58 Fanno Creek at Durham City Park Bed sediment — 07-21-99 C 1 A -28.05 3.29 L 10.52 E59 Fanno Creek at Durham City Park Bed sediment Top 10 cm, both oxic and 

anoxic fractions

07-21-99 A 0 A -27.81 3.07 17.03

59 Fanno Creek at Durham City Park Bed sediment Top 10 cm, both oxic and 

anoxic fractions

07-21-99 B 0 A -28.03 3.76 13.80

59 Fanno Creek at Durham City Park Bed sediment Top 10 cm, both oxic and 

anoxic fractions

07-21-99 C 0 A -28.13 3.87 13.98

60 Fanno Creek at Durham City Park Leaf litter Redtwig dogwood leaves 

in stream

07-21-99 A 0 A -29.50 4.20 30.01

60 Fanno Creek at Durham City Park Leaf litter Redtwig dogwood leaves 

in stream

07-21-99 B 0 A -29.61 4.56 28.44

60 Fanno Creek at Durham City Park Leaf litter Redtwig dogwood leaves 

in stream

07-21-99 C 0 A -29.68 4.63 28.81

61 Fanno Creek at Durham City Park Leaf litter Oregon Ash leaves in 

stream

07-21-99 A 0 A -26.76 3.32 48.56

61 Fanno Creek at Durham City Park Leaf litter Oregon Ash leaves in 

stream

07-21-99 B 0 A -26.86 3.25 42.84

61 Fanno Creek at Durham City Park Leaf litter Oregon Ash leaves in 

stream

07-21-99 C 0 A -26.78 2.94 40.81

62 Fanno Creek at Durham City Park Decomposed terrestrial 

detritus

Decomposed leaves and 

twigs in stream

07-21-99 A 0 A -27.82 4.52 21.02

62 Fanno Creek at Durham City Park Decomposed terrestrial 

detritus

Decomposed leaves and 

twigs in stream

07-21-99 B 0 A -27.64 5.01 18.71

62 Fanno Creek at Durham City Park Decomposed terrestrial 

detritus

Decomposed leaves and 

twigs in stream

07-21-99 C 0 A -28.10 5.24 17.37

63 Fanno Creek at Durham City Park Leaf litter Oregon Ash leaves from 

trail

07-21-99 A 0 A -27.09 1.18 16.10

63 Fanno Creek at Durham City Park Leaf litter Oregon Ash leaves from 

trail

07-21-99 B 0 A — 1.02 —

63 Fanno Creek at Durham City Park Leaf litter Oregon Ash leaves from 

trail

07-21-99 B 0 U -27.86 0.61 —

63 Fanno Creek at Durham City Park Leaf litter Oregon Ash leaves from 

trail

07-21-99 C 0 A -26.93 0.72 18.10

64 Fanno Creek at Durham City Park Leaf litter Oregon Ash seed pods from 

trail

07-21-99 A 0 A -26.36 0.68 39.13
44 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon Appendix A. Values of stable isotope compositions (δ13C, δ15N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split samples.—Continued ID Site name Sample type Sample detail Date Sample split Lab rep Acidified δ13C δ15N δ15N qualifier C/N C/N qualifier 64 Fanno Creek at Durham City Park Leaf litter Oregon Ash seed pods from trail 07-21-99

A 1 A -26.38 1.48 44.85

64 Fanno Creek at Durham City Park Leaf litter Oregon Ash seed pods from 

trail

07-21-99

A 0 U -28.27 0.57 39.87

64 Fanno Creek at Durham City Park Leaf litter Oregon Ash seed pods from 

trail

07-21-99

B 0 A -26.43 0.65 40.49

64 Fanno Creek at Durham City Park Leaf litter Oregon Ash seed pods from 

trail

07-21-99

C 0 A -26.56 0.63 36.18

65 Fanno Creek at Durham City Park Periphyton Cladophera 07-21-99

A 0 A -39.70 4.59 6.87

65 Fanno Creek at Durham City Park Periphyton Cladophera 07-21-99

B 0 A -39.63 4.54 6.86

65 Fanno Creek at Durham City Park Periphyton Cladophera 07-21-99

C 0 A -39.75 4.55 6.83

66 Fanno Creek at Durham City Park Periphyton Cladophera 07-21-99

A 0 A -26.70 8.47 6.92

67 Tualatin River at RM 9.4 (Basalt sill) Periphyton Cladophera 07-19-99

A 0 A -34.12 5.58 9.60

67 Tualatin River at RM 9.4 (Basalt sill) Periphyton Cladophera 07-19-99

B 0 A -34.07 5.34 9.54

67 Tualatin River at RM 9.4 (Basalt sill) Periphyton Cladophera 07-19-99

C 0 A -34.23 5.58 9.20

68 Onion Flat (Cipole Road and Hwy 99W) Soil agricultural field, tilled, not 

planted

07-21-99

A 0 A -27.90 5.01 14.49

68 Onion Flat (Cipole Road and Hwy 99W) Soil agricultural field, tilled, not 

planted

07-21-99

B 0 A

— 4.21 15.60

68 Onion Flat (Cipole Road and Hwy 99W) Soil agricultural field, tilled, not 

planted

07-21-99

C 0 A -27.84 5.21 14.65

69 Jackson Bottom (between Miller Swale and 

holding pond)

Soil Chehalis soil 08-04-99

A 0 A -27.04 6.55 9.14

69 Jackson Bottom (between Miller Swale and 

holding pond)

Soil Chehalis soil 08-04-99

B 0 A -27.38 5.63 9.46

69 Jackson Bottom (between Miller Swale and 

holding pond)

Soil Chehalis soil 08-04-99

C 0 A -27.22 6.17 10.05

70 Jackson Bottom (between Miller Swale and 

holding pond)

Leaf litter Oregon Ash leaves 08-04-99

A 0 A -25.34 2.53 53.91

70 Jackson Bottom (between Miller Swale and 

holding pond)

Leaf litter Oregon Ash leaves 08-04-99

B 0 A -24.82 1.84 57.66

70 Jackson Bottom (between Miller Swale and 

holding pond)

Leaf litter Oregon Ash leaves 08-04-99

C 0 A -25.02 1.68 58.39

71 Tualatin Nature Park Coniferous litter Mixed Western Red Cedar 

litter

08-04-99

A 0 A -24.75 -2.56 33.25

71 Tualatin Nature Park Coniferous litter Mixed Western Red Cedar 

litter

08-04-99

B 0 A -25.07 -2.59 30.72
Appendix A. 45

Appendix A. Values of stable isotope compositions (δ13C, δ15N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split samples.—Continued

ID Site name Sample type Sample detail Date Sample split Lab rep Acidified δ13C δ15N δ15N qualifier C/N C/N qualifier

71 Tualatin Nature Park Coniferous litter Mixed Western Red Cedar 

litter

08-04-99 C 0 A -24.91 -2.44 31.23

72 Tualatin Nature Park Coniferous litter Mixed Douglas Fir litter 08-04-99 A 0 A -27.85 -2.47 27.4872 Tualatin Nature Park Coniferous litter Mixed Douglas Fir litter 08-04-99 B 0 A -27.97 -2.68 26.9872 Tualatin Nature Park Coniferous litter Mixed Douglas Fir litter 08-04-99 C 0 A -27.66 -2.72 27.5773 Rock Creek Wastewater Treatment Facility WWTF effluent 

particulate

— 07-14-99 A 0 A -24.24 9.24 4.82

73 Rock Creek Wastewater Treatment Facility WWTF effluent 

particulate

— 07-14-99 A 0 U -23.71 10.00 5.17

73 Rock Creek Wastewater Treatment Facility WWTF effluent 

particulate

— 07-14-99 A 1 U -26.58 11.47 4.89

73 Rock Creek Wastewater Treatment Facility WWTF effluent 

particulate

— 07-14-99 B 0 A -25.62 10.80 6.67

73 Rock Creek Wastewater Treatment Facility WWTF effluent 

particulate

— 07-14-99 C 0 A -24.63 11.19 4.50

73 Rock Creek Wastewater Treatment Facility WWTF effluent 

particulate

— 07-14-99 C 0 U -23.81 10.09 5.55

74 Durham Wastewater Treatment Facility WWTF effluent 

particulate

— 07-14-99 A 0 A -26.07 9.08 L 4.67 E

74 Durham Wastewater Treatment Facility WWTF effluent 

particulate

— 07-14-99 B 0 A -25.96 9.26 L 4.39 E

74 Durham Wastewater Treatment Facility WWTF effluent 

particulate

— 07-14-99 C 0 A -25.99 9.45 L 4.60 E

76 Tualatin River at RM 16.2 (Elsner Bridge) Suspended sediment Fraction remaining 

suspended after 24 hours

07-21-99 A 0 A -33.91 6.70 4.75

76 Tualatin River at RM 16.2 (Elsner Bridge) Suspended sediment Fraction remaining 

suspended after 24 hours

07-21-99 B 0 A -33.82 6.54 4.78

76 Tualatin River at RM 16.2 (Elsner Bridge) Suspended sediment Fraction remaining 

suspended after 24 hours

07-21-99 C 0 A -33.84 6.57 4.79

77 Fanno Creek at Durham City Park Suspended sediment Fraction remaining 

suspended after 24 hours

07-21-99 A 0 A -28.32 4.91 8.55 E

77 Fanno Creek at Durham City Park Suspended sediment Fraction remaining 

suspended after 24 hours

07-21-99 B 0 A -28.50 5.12 L 8.48 E

77 Fanno Creek at Durham City Park Suspended sediment Fraction remaining 

suspended after 24 hours

07-21-99 C 0 A -28.40 5.15 9.04 E

101 Henry Hagg Lake Seston, >80 μm — 09-10-99 A 0 A -30.12 8.43 3.84101 Henry Hagg Lake Seston, >80 μm — 09-10-99 B 0 A -30.14 8.80 3.70
46 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon Appendix A. Values of stable isotope compositions (δ13C, δ15N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split samples.—Continued ID Site name Sample type Sample detail Date Sample split Lab rep Acidified δ13C δ15N δ15N qualifier C/N C/N qualifier 101 Henry Hagg Lake Seston, >80 μm

— 09-10-99

C 0 A -30.28 8.17 3.96

102 Henry Hagg Lake Seston, 80–202 μm

— 09-10-99

A 0 A -31.14 6.36 5.36

102 Henry Hagg Lake Seston, 80–202 μm

— 09-10-99

B 0 A -31.20 6.67 5.26

102 Henry Hagg Lake Seston, 80–202 μm

— 09-10-99

C 0 A -31.31 6.72 5.23

103 Tualatin River at RM 38.4 (Rood Bridge) Suspended sediment

— 09-10-99

A 0 A -30.93 4.26 11.90

103 Tualatin River at RM 38.4 (Rood Bridge) Suspended sediment

— 09-10-99

B 0 A -31.23 3.95 12.00

E

103 Tualatin River at RM 38.4 (Rood Bridge) Suspended sediment

— 09-10-99

C 0 A -31.07 4.15 11.89

E

104 Tualatin River at RM 38.4 (Rood Bridge) Bed sediment

— 09-10-99

A 0 A -26.79 4.00 14.14

104 Tualatin River at RM 38.4 (Rood Bridge) Bed sediment

— 09-10-99

A 1 A -28.21 3.85 14.27

104 Tualatin River at RM 38.4 (Rood Bridge) Bed sediment

— 09-10-99

A 0 U -28.07 3.95 13.18

104 Tualatin River at RM 38.4 (Rood Bridge) Bed sediment

— 09-10-99

B 0 A -27.21 4.22 15.06

104 Tualatin River at RM 38.4 (Rood Bridge) Bed sediment

— 09-10-99

B 0 U -28.27 3.87 12.91

104 Tualatin River at RM 38.4 (Rood Bridge) Bed sediment

— 09-10-99

C 0 A -28.11 3.91 15.40

E

104 Tualatin River at RM 38.4 (Rood Bridge) Bed sediment

— 09-10-99

C 0 U -28.17 3.85 13.40

104 Tualatin River at RM 38.4 (Rood Bridge) Bed sediment

— 09-10-99

C 1 U -28.24 3.94 12.27

105 Tualatin River at RM 9.9 (Cook Park) Seston, >80 μm

— 09-11-99

A 0 A -33.49 8.24 6.90

105 Tualatin River at RM 9.9 (Cook Park) Seston, >80 μm

— 09-11-99

B 0 A -32.83 7.90 7.17

105 Tualatin River at RM 9.9 (Cook Park) Seston, >80 μm

— 09-11-99

C 0 A -33.26 8.00 7.12

106 Tualatin River at RM 9.9 (Cook Park) Seston, 80–202 μm

— 09-11-99

A 0 A -32.80 7.43 7.83

106 Tualatin River at RM 9.9 (Cook Park) Seston, 80–202 μm

— 09-11-99

B 0 A -33.19 7.84 7.48

106 Tualatin River at RM 9.9 (Cook Park) Seston, 80–202 μm

— 09-11-99

C 0 A -33.00 7.49 7.47

107 Tualatin River at RM 9.9 (Cook Park) Suspended sediment

— 09-11-99

A 0 A -34.15 7.51 7.26

107 Tualatin River at RM 9.9 (Cook Park) Suspended sediment

— 09-11-99

B 0 A -33.95 7.17 7.62

107 Tualatin River at RM 9.9 (Cook Park) Suspended sediment

— 09-11-99

B 1 A -33.99 7.38 7.44

107 Tualatin River at RM 9.9 (Cook Park) Suspended sediment

— 09-11-99

C 0 A -34.14 7.35 7.54

108 Tualatin River at RM 9.9 (Cook Park) Bed sediment

— 09-11-99

A 0 A -30.03 6.32

L

—

108 Tualatin River at RM 9.9 (Cook Park) Bed sediment

— 09-11-99

A 0 U -30.98 5.78

L 15.60

E

108 Tualatin River at RM 9.9 (Cook Park) Bed sediment

— 09-11-99

B 0 A -31.08 4.07

L 14.47

E

108 Tualatin River at RM 9.9 (Cook Park) Bed sediment

— 09-11-99

C 0 A -30.22 4.46

L 14.30

E

109 Tualatin River at RM 9.4 (Basalt sill) Periphyton Cladophera 09-11-99

A 0 A -35.45 4.33 8.49

109 Tualatin River at RM 9.4 (Basalt sill) Periphyton Cladophera 09-11-99

B 0 A -35.47 4.52 8.50

109 Tualatin River at RM 9.4 (Basalt sill) Periphyton Cladophera 09-11-99

C 0 A -35.58 3.98 8.79

110 Tualatin River at RM 20.3 Seston, >80 μm

— 09-13-99

A 0 A -29.87 4.09 10.42
Appendix A. 47

Appendix A. Values of stable isotope compositions (δ13C, δ15N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split samples.—Continued

ID Site name Sample type Sample detail Date Sample split Lab rep Acidified δ13C δ15N δ15N qualifier C/N C/N qualifier

110 Tualatin River at RM 20.3 Seston, >80 μm — 09-13-99 B 0 A -29.49 4.28 11.07110 Tualatin River at RM 20.3 Seston, >80 μm — 09-13-99 C 0 A -29.18 4.11 11.91110 Tualatin River at RM 20.3 Seston, >80 μm — 09-13-99 C 1 A -29.56 4.20 9.91

111 Tualatin River at RM 20.3 Seston, 80–202 μm — 09-13-99 A 0 A -31.04 5.41 10.05111 Tualatin River at RM 20.3 Seston, 80–202 μm — 09-13-99 B 0 A -30.61 5.85 11.26111 Tualatin River at RM 20.3 Seston, 80–202 μm — 09-13-99 C 0 A -30.94 6.37 9.32

112 Tualatin River at RM 20.3 Suspended sediment — 09-13-99 A 0 A -30.12 7.12 13.78112 Tualatin River at RM 20.3 Suspended sediment — 09-13-99 B 0 A -31.58 6.38 11.94112 Tualatin River at RM 20.3 Suspended sediment — 09-13-99 C 0 A -30.71 6.70 12.45113 Tualatin River at RM 20.3 Bed sediment — 09-13-99 A 0 A -28.80 — 15.26113 Tualatin River at RM 20.3 Bed sediment — 09-13-99 A 0 U -29.54 5.10 12.60113 Tualatin River at RM 20.3 Bed sediment — 09-13-99 A 1 U -29.53 5.56 13.36113 Tualatin River at RM 20.3 Bed sediment — 09-13-99 B 0 A -29.33 5.41 13.78113 Tualatin River at RM 20.3 Bed sediment — 09-13-99 C 0 A -29.28 5.87 12.99114 Tualatin River at RM 20.3 Bed sediment Anoxic blue-gray fraction 09-13-99 A 0 A -28.52 5.36 L 13.19 E114 Tualatin River at RM 20.3 Bed sediment Anoxic blue-gray fraction 09-13-99 A 1 A -28.69 4.99 L 12.40 E114 Tualatin River at RM 20.3 Bed sediment Anoxic blue-gray fraction 09-13-99 B 0 A -28.99 6.11 L 12.00 E114 Tualatin River at RM 20.3 Bed sediment Anoxic blue-gray fraction 09-13-99 C 0 A -28.69 5.01 L 12.99 E115 Tualatin River at RM 16.2 (Elsner Bridge) Suspended sediment — 09-13-99 A 0 A -31.69 7.67 10.52115 Tualatin River at RM 16.2 (Elsner Bridge) Suspended sediment — 09-13-99 B 0 A -32.74 — 9.82115 Tualatin River at RM 16.2 (Elsner Bridge) Suspended sediment — 09-13-99 C 0 A -32.38 6.49 10.15116 Tualatin River at RM 16.2 (Elsner Bridge) Seston, >80 μm — 09-13-99 A 0 A -31.30 5.91 L 8.42116 Tualatin River at RM 16.2 (Elsner Bridge) Seston, >80 μm — 09-13-99 B 0 A -31.15 6.08 8.56116 Tualatin River at RM 16.2 (Elsner Bridge) Seston, >80 μm — 09-13-99 C 0 A -30.76 5.88 8.86117 Tualatin River at RM 16.2 (Elsner Bridge) Seston, 80–202 μm — 09-13-99 A 0 A -31.69 6.94 L 8.51117 Tualatin River at RM 16.2 (Elsner Bridge) Seston, 80–202 μm — 09-13-99 B 0 A -31.48 6.66 L 9.30117 Tualatin River at RM 16.2 (Elsner Bridge) Seston, 80–202 μm — 09-13-99 B 1 A -31.61 6.55 L 9.27117 Tualatin River at RM 16.2 (Elsner Bridge) Seston, 80–202 μm — 09-13-99 C 0 A -30.85 6.59 L 9.80118 Tualatin River at RM 16.2 (Elsner Bridge) Bed sediment — 09-13-99 A 0 A -28.74 6.16 14.14118 Tualatin River at RM 16.2 (Elsner Bridge) Bed sediment — 09-13-99 B 0 A -28.67 5.98 14.28118 Tualatin River at RM 16.2 (Elsner Bridge) Bed sediment — 09-13-99 C 0 A -28.75 6.02 13.88119 Tualatin River at RM 26.9 (Scholls) Seston, >80 μm — 09-15-99 A 0 A -29.02 6.61 L 12.08119 Tualatin River at RM 26.9 (Scholls) Seston, >80 μm — 09-15-99 B 0 A -28.84 6.34 L 11.99
48 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon Appendix A. Values of stable isotope compositions (δ13C, δ15N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split samples.—Continued ID Site name Sample type Sample detail Date Sample split Lab rep Acidified δ13C δ15N δ15N qualifier C/N C/N qualifier 119 Tualatin River at RM 26.9 (Scholls) Seston, >80 μm

— 09-15-99

C 0 A -28.92 6.19 12.01

120 Tualatin River at RM 26.9 (Scholls) Seston, 80–202 μm

— 09-15-99

A 0 A -28.93 5.66 12.24

120 Tualatin River at RM 26.9 (Scholls) Seston, 80–202 μm

— 09-15-99

B 0 A -29.12 5.92 12.39

120 Tualatin River at RM 26.9 (Scholls) Seston, 80–202 μm

— 09-15-99

C 0 A -28.91 5.63 12.79

120 Tualatin River at RM 26.9 (Scholls) Seston, 80–202 μm

— 09-15-99

C 1 A -29.03 5.79 12.19

121 Tualatin River at RM 26.9 (Scholls) Suspended sediment

— 09-15-99

A 0 A -29.69 6.47 11.67

121 Tualatin River at RM 26.9 (Scholls) Suspended sediment

— 09-15-99

B 0 A -27.86 7.59 12.88

121 Tualatin River at RM 26.9 (Scholls) Suspended sediment

— 09-15-99

B 0 U -27.76 7.29 12.48

121 Tualatin River at RM 26.9 (Scholls) Suspended sediment

— 09-15-99

C 0 A -28.56

— 12.59

122 Tualatin River at RM 26.9 (Scholls) Bed sediment

— 09-15-99

A 0 A -29.32

— 17.08

E

122 Tualatin River at RM 26.9 (Scholls) Bed sediment

— 09-15-99

A 0 U -29.78 5.66

L 15.00

E

122 Tualatin River at RM 26.9 (Scholls) Bed sediment

— 09-15-99

A 1 U -29.61 5.51 14.63

E

122 Tualatin River at RM 26.9 (Scholls) Bed sediment

— 09-15-99

B 0 A -29.43

— 16.23

E

122 Tualatin River at RM 26.9 (Scholls) Bed sediment

— 09-15-99

B 0 U -29.63 5.79 12.67

E

122 Tualatin River at RM 26.9 (Scholls) Bed sediment

— 09-15-99

B 1 U -29.43 5.88 14.00

122 Tualatin River at RM 26.9 (Scholls) Bed sediment

— 09-15-99

C 0 A -29.65 5.45 15.09

E

123 Tualatin River at RM 5.5 (Stafford Road) Suspended sediment

— 09-15-99

A 0 A -33.86 13.12 8.00

123 Tualatin River at RM 5.5 (Stafford Road) Suspended sediment

— 09-15-99

B 0 A -33.63 12.36 8.12

123 Tualatin River at RM 5.5 (Stafford Road) Suspended sediment

— 09-15-99

C 0 A -33.54 12.90 8.40

124 Tualatin River at RM 5.5 (Stafford Road) Seston, >80 μm

— 09-15-99

A 0 A -37.69 16.74 4.95

124 Tualatin River at RM 5.5 (Stafford Road) Seston, >80 μm

— 09-15-99

A 1 A -37.72 16.60 4.89

124 Tualatin River at RM 5.5 (Stafford Road) Seston, >80 μm

— 09-15-99

B 0 A -37.59 16.78 4.83

124 Tualatin River at RM 5.5 (Stafford Road) Seston, >80 μm

— 09-15-99

C 0 A -37.64 16.71 4.85

125 Tualatin River at RM 5.5 (Stafford Road) Seston, 80–202 μm

— 09-15-99

A 0 A -37.91 17.17 4.68

125 Tualatin River at RM 5.5 (Stafford Road) Seston, 80–202 μm

— 09-15-99

B 0 A -38.37

— 4.49

125 Tualatin River at RM 5.5 (Stafford Road) Seston, 80–202 μm

— 09-15-99

C 0 A -38.40 17.54 4.47

126 Tualatin River at RM 5.5 (Stafford Road) Bed sediment

— 09-15-99

A 0 A -29.37 6.55 11.51

126 Tualatin River at RM 5.5 (Stafford Road) Bed sediment

— 09-15-99

B 0 A -29.42 6.28 11.27

126 Tualatin River at RM 5.5 (Stafford Road) Bed sediment

— 09-15-99

C 0 A -29.46 6.05 10.78

201 Tualatin River at RM 38.4 (Rood Bridge) Suspended sediment

— 02-08-00

A 0 A -30.48 4.56 9.86

E

201 Tualatin River at RM 38.4 (Rood Bridge) Suspended sediment

— 02-08-00

B 0 A -31.24 4.38 11.61

E

201 Tualatin River at RM 38.4 (Rood Bridge) Suspended sediment

— 02-08-00

C 0 A -30.40 5.73 9.70

E

202 Tualatin River at RM 5.5 (Stafford Road) Suspended sediment

— 02-04-00

A 0 A -32.32 4.72

L 13.98

E
Appendix A. 49

Appendix A. Values of stable isotope compositions (δ13C, δ15N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split samples.—Continued

ID Site name Sample type Sample detail Date Sample split Lab rep Acidified δ13C δ15N δ15N qualifier C/N C/N qualifier

202 Tualatin River at RM 5.5 (Stafford Road) Suspended sediment — 02-04-00 B 0 A -31.57 4.11 L 12.00 E202 Tualatin River at RM 5.5 (Stafford Road) Suspended sediment — 02-04-00 B 1 A -31.97 2.67 L 14.96 E202 Tualatin River at RM 5.5 (Stafford Road) Suspended sediment — 02-04-00 B 0 U -31.68 3.72 L 14.47 E202 Tualatin River at RM 5.5 (Stafford Road) Suspended sediment — 02-04-00 C 0 A -32.49 5.04 L 13.98 E203 Tualatin River at RM 26.9 (Scholls) Suspended sediment — 02-04-00 A 0 A -30.74 4.28 L 15.21 E203 Tualatin River at RM 26.9 (Scholls) Suspended sediment — 02-04-00 B 0 A -30.64 — 15.70 E203 Tualatin River at RM 26.9 (Scholls) Suspended sediment — 02-04-00 C 0 A -31.19 4.58 L 17.27 E203 Tualatin River at RM 26.9 (Scholls) Suspended sediment — 02-04-00 C 1 A -31.29 — 13.98 E203 Tualatin River at RM 26.9 (Scholls) Suspended sediment — 02-04-00 C 0 U -31.21 4.02 L 14.25 E204 Tualatin River at RM 26.9 (Scholls) Bed sediment Woody debris removed 02-04-00 A 0 A -27.87 4.65 L 25.24204 Tualatin River at RM 26.9 (Scholls) Bed sediment Woody debris removed 02-04-00 A 1 A -27.50 5.34 27.62204 Tualatin River at RM 26.9 (Scholls) Bed sediment Woody debris removed 02-04-00 B 0 A -27.44 4.73 29.25204 Tualatin River at RM 26.9 (Scholls) Bed sediment Woody debris removed 02-04-00 B 1 A -27.80 4.91 L 28.01204 Tualatin River at RM 26.9 (Scholls) Bed sediment Woody debris removed 02-04-00 C 0 A -27.53 5.59 29.24204 Tualatin River at RM 26.9 (Scholls) Bed sediment Woody debris removed 02-04-00 C 1 A -27.71 3.79 L 27.43206 Tualatin River at RM 16.2 (Elsner Bridge) Suspended sediment — 02-04-00 A 0 U -30.78 4.20 L 11.80 E206 Tualatin River at RM 16.2 (Elsner Bridge) Suspended sediment — 02-04-00 B 0 A -30.89 2.81 L 13.98 E206 Tualatin River at RM 16.2 (Elsner Bridge) Suspended sediment — 02-04-00 C 0 A -31.22 4.56 13.73 E207 Tualatin River at RM 16.2 (Elsner Bridge) Bed sediment — 02-04-00 A 0 A -28.54 4.12 L 23.19 E207 Tualatin River at RM 16.2 (Elsner Bridge) Bed sediment — 02-04-00 B 0 A -28.25 3.76 L 24.67 E207 Tualatin River at RM 16.2 (Elsner Bridge) Bed sediment — 02-04-00 B 1 A -28.64 4.11 L 23.02 E207 Tualatin River at RM 16.2 (Elsner Bridge) Bed sediment — 02-04-00 C 0 A -28.78 4.30 L 22.07 E208 Gales Creek at old Hwy 47 Suspended sediment — 02-07-00 A 0 A -27.73 3.75 L 30.76 E208 Gales Creek at old Hwy 47 Suspended sediment — 02-07-00 B 0 A -29.76 — 28.29 E208 Gales Creek at old Hwy 47 Suspended sediment — 02-07-00 C 0 A -29.15 3.45 L 25.82 E209 Dairy Creek at Hwy 8 Suspended sediment — 02-07-00 A 0 A -31.28 — 12.13 E209 Dairy Creek at Hwy 8 Suspended sediment — 02-07-00 A 0 U -31.40 4.04 L 13.80 E209 Dairy Creek at Hwy 8 Suspended sediment — 02-07-00 A 1 U -32.55 3.45 L 13.78 E209 Dairy Creek at Hwy 8 Suspended sediment — 02-07-00 B 0 A -31.44 3.94 L 13.55 E209 Dairy Creek at Hwy 8 Suspended sediment — 02-07-00 C 0 A -31.16 4.05 L 11.86 E210 Tualatin River at RM 58.8 (Dilley) Suspended sediment — 02-07-00 A 0 A -30.94 3.16 13.11 E210 Tualatin River at RM 58.8 (Dilley) Suspended sediment — 02-07-00 A 0 U -28.89 3.21 L 13.00 E210 Tualatin River at RM 58.8 (Dilley) Suspended sediment — 02-07-00 A 1 U -29.47 3.93 L 14.46 E
50 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon Appendix A. Values of stable isotope compositions (δ13C, δ15N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split samples.—Continued ID Site name Sample type Sample detail Date Sample split Lab rep Acidified δ13C δ15N δ15N qualifier C/N C/N qualifier 210 Tualatin River at RM 58.8 (Dilley) Suspended sediment

— 02-07-00

B 0 A -29.41 2.68

L 15.95

E

210 Tualatin River at RM 58.8 (Dilley) Suspended sediment

— 02-07-00

C 0 A -29.42 4.41

L 15.16

E

210 Tualatin River at RM 58.8 (Dilley) Suspended sediment

— 02-07-00

C 1 A -29.14 4.25 13.24

E

211 Rock Creek at Hwy 8 Suspended sediment

— 02-07-00

A 0 U -32.37 5.01

L 16.50

E

211 Rock Creek at Hwy 8 Suspended sediment

— 02-07-00

A 1 U -33.34 4.63

L 14.50

E

211 Rock Creek at Hwy 8 Suspended sediment

— 02-07-00

B 0 A -32.27 4.42

L 15.95

E

211 Rock Creek at Hwy 8 Suspended sediment

— 02-07-00

C 0 A -32.06 4.28

L 13.32

E

212 Fanno Creek at Durham Road Suspended sediment

— 02-07-00

A 0 A -31.12 4.48

L 14.57

E

212 Fanno Creek at Durham Road Suspended sediment

— 02-07-00

B 0 A -30.95 4.28

L 13.19

E

212 Fanno Creek at Durham Road Suspended sediment

— 02-07-00

B 1 A -31.18 4.05

L 15.46

E

212 Fanno Creek at Durham Road Suspended sediment

— 02-07-00

C 0 A -32.39 3.58

L 12.66

E

212 Fanno Creek at Durham Road Suspended sediment

— 02-07-00

C 0 U -31.63 4.45

L 13.67

E

212 Fanno Creek at Durham Road Suspended sediment

— 02-07-00

C 1 U -32.66 5.19

L 13.33

E

301 Henry Hagg Lake Seston, >80 μm

— 06-03-00

A 0 U -26.41 3.41 9.97

301 Henry Hagg Lake Seston, >80 μm

— 06-03-00

B 0 U -26.26 3.41 9.45

301 Henry Hagg Lake Seston, >80 μm

— 06-03-00

C 0 U -26.52 3.13 9.98

301 Henry Hagg Lake Seston, >80 μm

— 06-03-00

D 0 U -26.28 3.55 10.00

302 Henry Hagg Lake Seston, 80–202 μm

— 06-03-00

A 0 U -26.07 2.96 8.61

302 Henry Hagg Lake Seston, 80–202 μm

— 06-03-00

B 0 U -26.28 2.98 8.21

302 Henry Hagg Lake Seston, 80–202 μm

— 06-03-00

C 0 U -25.85 2.98 9.06

302 Henry Hagg Lake Seston, 80–202 μm

— 06-03-00

D 0 U -27.17 3.18

L 8.64

303 Tualatin River at RM 38.4 (Rood Bridge) Suspended sediment

— 06-05-00

A 0 U -31.15 5.56 9.46

303 Tualatin River at RM 38.4 (Rood Bridge) Suspended sediment

— 06-05-00

B 0 U -31.27 5.26 9.91

303 Tualatin River at RM 38.4 (Rood Bridge) Suspended sediment

— 06-05-00

B 1 U -31.06 5.40 10.27

303 Tualatin River at RM 38.4 (Rood Bridge) Suspended sediment

— 06-05-00

C 0 U -31.07 5.34 10.00

304 Tualatin River at RM 38.4 (Rood Bridge) Bed sediment

— 06-05-00

A 0 U -28.18 4.27 13.10

304 Tualatin River at RM 38.4 (Rood Bridge) Bed sediment

— 06-05-00

B 0 U -28.05 4.16 13.36

304 Tualatin River at RM 38.4 (Rood Bridge) Bed sediment

— 06-05-00

C 0 U -28.12 3.76 14.20

305 Tualatin River at RM 9.9 (Cook Park) Seston, >80 μm

— 06-03-00

A 0 U -32.67 9.31 7.71

305 Tualatin River at RM 9.9 (Cook Park) Seston, >80 μm

— 06-03-00

B 0 U -32.53 8.79 7.57

305 Tualatin River at RM 9.9 (Cook Park) Seston, >80 μm

— 06-03-00

C 0 U -32.45 8.96 7.52

306 Tualatin River at RM 9.9 (Cook Park) Seston, 80–202 μm

— 06-03-00

A 0 U -32.68 8.63 7.49

306 Tualatin River at RM 9.9 (Cook Park) Seston, 80–202 μm

— 06-03-00

B 0 U -32.43 9.18 7.67
Appendix A. 51

Appendix A. Values of stable isotope compositions (δ13C, δ15N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split samples.—Continued

ID Site name Sample type Sample detail Date Sample split Lab rep Acidified δ13C δ15N δ15N qualifier C/N C/N qualifier

306 Tualatin River at RM 9.9 (Cook Park) Seston, 80–202 μm — 06-03-00 C 0 U -32.59 8.43 7.82306 Tualatin River at RM 9.9 (Cook Park) Seston, 80–202 μm — 06-03-00 C 1 U -32.52 8.46 7.70307 Tualatin River at RM 9.9 (Cook Park) Suspended sediment — 06-03-00 A 0 U -35.06 9.45 6.52307 Tualatin River at RM 9.9 (Cook Park) Suspended sediment — 06-03-00 B 0 U -34.99 9.53 6.80307 Tualatin River at RM 9.9 (Cook Park) Suspended sediment — 06-03-00 C 0 U -35.17 9.51 6.80308 Tualatin River at RM 9.9 (Cook Park) Bed sediment — 06-03-00 A 0 U -28.45 4.97 L 13.17 E308 Tualatin River at RM 9.9 (Cook Park) Bed sediment — 06-03-00 B 0 U -28.88 5.21 L 13.86 E308 Tualatin River at RM 9.9 (Cook Park) Bed sediment — 06-03-00 C 0 U -28.68 5.64 L 13.57 E309 Tualatin River at RM 9.9 (Cook Park) Duckweed Decomposed duckweed 06-03-00 A 0 U -29.19 7.62 10.43309 Tualatin River at RM 9.9 (Cook Park) Duckweed Decomposed duckweed 06-03-00 B 0 U -29.36 7.57 10.98309 Tualatin River at RM 9.9 (Cook Park) Duckweed Decomposed duckweed 06-03-00 C 0 U -28.11 — 11.02309 Tualatin River at RM 9.9 (Cook Park) Duckweed Decomposed duckweed 06-03-00 C 1 U -28.27 6.06 11.21310 Tualatin River at RM 9.4 (Basalt sill) Periphyton Cladophera 06-03-00 A 0 U -36.24 6.60 8.10310 Tualatin River at RM 9.4 (Basalt sill) Periphyton Cladophera 06-03-00 A 1 U -36.19 6.69 8.28310 Tualatin River at RM 9.4 (Basalt sill) Periphyton Cladophera 06-03-00 B 0 U -36.19 7.00 8.19310 Tualatin River at RM 9.4 (Basalt sill) Periphyton Cladophera 06-03-00 C 0 U -36.23 6.95 8.56

311 Tualatin River at RM 8.7 (Boones Ferry Bridge) Seston, >80 μm — 06-03-00 A 0 U -32.71 9.92 8.10311 Tualatin River at RM 8.7 (Boones Ferry Bridge) Seston, >80 μm — 06-03-00 B 0 U -32.51 10.00 8.19311 Tualatin River at RM 8.7 (Boones Ferry Bridge) Seston, >80 μm — 06-03-00 C 0 U -32.62 10.06 8.28

312 Tualatin River at RM 8.7 (Boones Ferry Bridge) Seston, 80–202 μm — 06-03-00 A 0 U -32.60 9.50 8.57312 Tualatin River at RM 8.7 (Boones Ferry Bridge) Seston, 80–202 μm — 06-03-00 B 0 U -32.66 8.80 8.81312 Tualatin River at RM 8.7 (Boones Ferry Bridge) Seston, 80–202 μm — 06-03-00 C 0 U -32.65 9.16 8.76313 Tualatin River at RM 8.7 (Boones Ferry Bridge) Suspended sediment — 06-03-00 A 0 U -35.82 11.95 L 6.55313 Tualatin River at RM 8.7 (Boones Ferry Bridge) Suspended sediment — 06-03-00 B 0 U -34.98 10.81 L 6.62313 Tualatin River at RM 8.7 (Boones Ferry Bridge) Suspended sediment — 06-03-00 B 1 U -34.85 11.62 L 6.63314 Tualatin River at RM 8.7 (Boones Ferry Bridge) Bed sediment — 06-03-00 A 0 U -28.86 5.83 L 13.29 E314 Tualatin River at RM 8.7 (Boones Ferry Bridge) Bed sediment — 06-03-00 B 0 U -28.71 6.13 L 13.71 E314 Tualatin River at RM 8.7 (Boones Ferry Bridge) Bed sediment — 06-03-00 C 0 U -28.86 5.80 L 12.83 E315 Tualatin River at RM 20.3 Seston, >80 μm — 06-05-00 A 0 U -29.43 7.82 13.82315 Tualatin River at RM 20.3 Seston, >80 μm — 06-05-00 B 0 U -29.73 7.68 12.65315 Tualatin River at RM 20.3 Seston, >80 μm — 06-05-00 C 0 U -29.66 8.62 12.79316 Tualatin River at RM 20.3 Seston, 80–202 μm — 06-05-00 A 0 U -29.79 8.08 13.04316 Tualatin River at RM 20.3 Seston, 80–202 μm — 06-05-00 B 0 U -29.77 7.96 13.28
52 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon Appendix A. Values of stable isotope compositions (δ13C, δ15N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split samples.—Continued ID Site name Sample type Sample detail Date Sample split Lab rep Acidified δ13C δ15N δ15N qualifier C/N C/N qualifier 316 Tualatin River at RM 20.3 Seston, 80–202 μm

— 06-05-00

C 0 U -29.76 6.98 13.54

316 Tualatin River at RM 20.3 Seston, 80–202 μm

— 06-05-00

C 1 U -29.77 7.51 13.03

317 Tualatin River at RM 20.3 Suspended sediment

— 06-05-00

A 0 U -32.55 8.80 8.67

317 Tualatin River at RM 20.3 Suspended sediment

— 06-05-00

B 0 U -32.73 8.81 8.83

317 Tualatin River at RM 20.3 Suspended sediment

— 06-05-00

C 0 U -32.38 8.69 8.72

318 Tualatin River at RM 20.3 Bed sediment

— 06-05-00

A 0 U -28.41 5.38 12.71

318 Tualatin River at RM 20.3 Bed sediment

— 06-05-00

B 0 U -28.20 5.38 12.92

318 Tualatin River at RM 20.3 Bed sediment

— 06-05-00

C 0 U -28.25 5.65 13.17

319 Tualatin River at RM 16.2 (Elsner Bridge) Suspended sediment

— 06-02-00

B 0 U -30.51 10.84 10.95

319 Tualatin River at RM 16.2 (Elsner Bridge) Suspended sediment

— 06-02-00

B 1 U -30.22 9.82 10.92

319 Tualatin River at RM 16.2 (Elsner Bridge) Suspended sediment

— 06-02-00

C 0 U -29.99 11.24 11.38

320 Tualatin River at RM 16.2 (Elsner Bridge) Seston, >80 μm

— 06-02-00

A 0 U -29.41 10.09 10.56

320 Tualatin River at RM 16.2 (Elsner Bridge) Seston, >80 μm

— 06-02-00

B 0 U -29.04 10.30 11.40

320 Tualatin River at RM 16.2 (Elsner Bridge) Seston, >80 μm

— 06-02-00

C 0 U -29.18 10.35 11.46

321 Tualatin River at RM 16.2 (Elsner Bridge) Seston, 80–202 μm

— 06-02-00

A 0 U -31.65 10.03 9.38

321 Tualatin River at RM 16.2 (Elsner Bridge) Seston, 80–202 μm

— 06-02-00

B 0 U -31.51 10.84

L 9.50

321 Tualatin River at RM 16.2 (Elsner Bridge) Seston, 80–202 μm

— 06-02-00

C 0 U -31.70 10.24

L 9.39

322 Tualatin River at RM 16.2 (Elsner Bridge) Bed sediment

— 06-02-00

A 0 U -28.08 5.14 12.69

322 Tualatin River at RM 16.2 (Elsner Bridge) Bed sediment

— 06-02-00

B 0 U -28.05 5.27 12.64

322 Tualatin River at RM 16.2 (Elsner Bridge) Bed sediment

— 06-02-00

C 0 U -27.65 5.24 13.69

323 Tualatin River at RM 26.9 (Scholls) Seston, >80 μm

— 06-02-00

A 0 U -28.82 5.94 15.19

323 Tualatin River at RM 26.9 (Scholls) Seston, >80 μm

— 06-02-00

B 0 U -29.04 6.81

L 15.17

323 Tualatin River at RM 26.9 (Scholls) Seston, >80 μm

— 06-02-00

B 1 U -28.94 6.22 15.52

323 Tualatin River at RM 26.9 (Scholls) Seston, >80 μm

— 06-02-00

C 0 U -28.90 5.95

L 15.10

324 Tualatin River at RM 26.9 (Scholls) Seston, 80–202 μm

— 06-02-00

A 0 U -29.07 5.79

L 15.13

324 Tualatin River at RM 26.9 (Scholls) Seston, 80–202 μm

— 06-02-00

B 0 U -29.15 6.21

L 15.30

324 Tualatin River at RM 26.9 (Scholls) Seston, 80–202 μm

— 06-02-00

C 0 U -29.11 4.66

L 15.36

325 Tualatin River at RM 26.9 (Scholls) Suspended sediment

— 06-02-00

A 0 U -31.30 7.10 5.90

325 Tualatin River at RM 26.9 (Scholls) Suspended sediment

— 06-02-00

B 0 U -30.72 7.01 6.29

325 Tualatin River at RM 26.9 (Scholls) Suspended sediment

— 06-02-00

C 0 U -31.38 7.04 5.65

326 Tualatin River at RM 26.9 (Scholls) Bed sediment

— 06-02-00

A 0 U -27.54 5.18 7.89

326 Tualatin River at RM 26.9 (Scholls) Bed sediment

— 06-02-00

B 0 U -28.25 5.54 7.50

326 Tualatin River at RM 26.9 (Scholls) Bed sediment

— 06-02-00

C 0 U -27.40 5.09 9.32
Appendix A. 53

Appendix A. Values of stable isotope compositions (δ13C, δ15N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split samples.—Continued

ID Site name Sample type Sample detail Date Sample split Lab rep Acidified δ13C δ15N δ15N qualifier C/N C/N qualifier

326 Tualatin River at RM 26.9 (Scholls) Bed sediment — 06-02-00 C 1 U -28.02 5.23 7.78327 Tualatin River at RM 5.5 (Stafford Road) Suspended sediment — 06-02-00 A 0 U -33.59 12.22 8.93327 Tualatin River at RM 5.5 (Stafford Road) Suspended sediment — 06-02-00 B 0 U -33.70 12.16 9.08327 Tualatin River at RM 5.5 (Stafford Road) Suspended sediment — 06-02-00 C 0 U -33.24 11.92 9.33328 Tualatin River at RM 5.5 (Stafford Road) Seston, >80 μm — 06-02-00 A 0 U -37.66 13.46 6.45328 Tualatin River at RM 5.5 (Stafford Road) Seston, >80 μm — 06-02-00 B 0 U -37.88 13.70 6.44328 Tualatin River at RM 5.5 (Stafford Road) Seston, >80 μm — 06-02-00 C 0 U -37.88 13.59 6.43329 Tualatin River at RM 5.5 (Stafford Road) Seston, 80–202 μm — 06-02-00 A 0 U -37.87 13.69 6.16329 Tualatin River at RM 5.5 (Stafford Road) Seston, 80–202 μm — 06-02-00 B 0 U -38.01 13.80 6.05329 Tualatin River at RM 5.5 (Stafford Road) Seston, 80–202 μm — 06-02-00 C 0 U -38.09 13.73 6.15330 Tualatin River at RM 5.5 (Stafford Road) Bed sediment — 06-02-00 A 0 U -28.02 5.52 8.18330 Tualatin River at RM 5.5 (Stafford Road) Bed sediment — 06-02-00 A 1 U -28.20 5.86 7.65330 Tualatin River at RM 5.5 (Stafford Road) Bed sediment — 06-02-00 B 0 U -28.10 5.79 7.89330 Tualatin River at RM 5.5 (Stafford Road) Bed sediment — 06-02-00 C 0 U -28.28 5.89 —331 Gales Creek at old Hwy 47 Suspended sediment — 05-31-00 A 0 U -29.66 2.97 7.72331 Gales Creek at old Hwy 47 Suspended sediment — 05-31-00 B 0 U -29.77 3.28 8.84331 Gales Creek at old Hwy 47 Suspended sediment — 05-31-00 C 0 U -29.73 2.81 8.33332 Gales Creek at old Hwy 47 Bed sediment — 05-31-00 A 0 U -27.74 1.76 9.11332 Gales Creek at old Hwy 47 Bed sediment — 05-31-00 B 0 U -27.49 1.86 12.50332 Gales Creek at old Hwy 47 Bed sediment — 05-31-00 C 0 U -27.60 1.55 10.88333 Tualatin River at RM 58.8 (Dilley) Suspended sediment — 05-31-00 A 0 U -30.26 4.83 8.72333 Tualatin River at RM 58.8 (Dilley) Suspended sediment — 05-31-00 B 0 U -30.95 4.66 9.28333 Tualatin River at RM 58.8 (Dilley) Suspended sediment — 05-31-00 B 1 U -31.01 4.51 9.11333 Tualatin River at RM 58.8 (Dilley) Suspended sediment — 05-31-00 C 0 U -30.24 4.54 8.89334 Tualatin River at RM 58.8 (Dilley) Bed sediment — 05-31-00 A 0 U -27.86 2.36 10.00334 Tualatin River at RM 58.8 (Dilley) Bed sediment — 05-31-00 B 0 U -27.78 2.48 13.12334 Tualatin River at RM 58.8 (Dilley) Bed sediment — 05-31-00 C 0 U -27.68 2.59 10.57335 Dairy Creek at Hwy 8 Suspended sediment — 05-31-00 A 0 U -31.41 3.72 8.50335 Dairy Creek at Hwy 8 Suspended sediment — 05-31-00 B 0 U -31.34 3.70 8.64335 Dairy Creek at Hwy 8 Suspended sediment — 05-31-00 C 0 U -31.26 3.71 5.86336 Dairy Creek at Hwy 8 Bed sediment — 05-31-00 A 0 U -27.78 3.80 15.62336 Dairy Creek at Hwy 8 Bed sediment — 05-31-00 B 0 U -27.87 3.88 13.95336 Dairy Creek at Hwy 8 Bed sediment — 05-31-00 C 0 U -27.76 3.60 15.41
54 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon Appendix A. Values of stable isotope compositions (δ13C, δ15N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split samples.—Continued ID Site name Sample type Sample detail Date Sample split Lab rep Acidified δ13C δ15N δ15N qualifier C/N C/N qualifier 336 Dairy Creek at Hwy 8 Bed sediment

— 05-31-00

C 1 U -27.68 3.47 17.05

337 Dairy Creek at Hwy 8 Grass Grass growing in stream 05-31-00

A 0 U -31.09 4.57 14.73

337 Dairy Creek at Hwy 8 Grass Grass growing in stream 05-31-00

B 0 U -31.16 4.62 14.99

337 Dairy Creek at Hwy 8 Grass Grass growing in stream 05-31-00

C 0 U -31.02 4.73 13.79

338 Rock Creek at Hwy 8 Suspended sediment

— 05-31-00

A 0 U -32.07 5.58 7.29

338 Rock Creek at Hwy 8 Suspended sediment

— 05-31-00

B 0 U -32.05 5.69 6.33

338 Rock Creek at Hwy 8 Suspended sediment

— 05-31-00

C 0 U -31.92 5.55 6.20

339 Rock Creek at Hwy 8 Bed sediment

— 05-31-00

A 0 U -28.63 5.58 15.43

339 Rock Creek at Hwy 8 Bed sediment

— 05-31-00

B 0 U -28.95 5.55 15.00

339 Rock Creek at Hwy 8 Bed sediment

— 05-31-00

C 0 U -28.78 5.56 14.09

340 Rock Creek at Hwy 8 Periphyton Species not identified 05-31-00

A 0 U -42.79 3.57 6.92

340 Rock Creek at Hwy 8 Periphyton Species not identified 05-31-00

A 1 U -42.85 3.53 6.94

340 Rock Creek at Hwy 8 Periphyton Species not identified 05-31-00

B 0 U -43.05 3.52 6.86

340 Rock Creek at Hwy 8 Periphyton Species not identified 05-31-00

C 0 U -42.68 3.52 6.98

341 Rock Creek at Hwy 8 Decomposed terrestrial 

detritus

Decomposed non-woody 

plant material in stream

05-31-00

A 0 U -28.48 5.04 19.24

341 Rock Creek at Hwy 8 Decomposed terrestrial 

detritus

Decomposed non-woody 

plant material in stream

05-31-00

B 0 U -28.59 4.98 19.11

341 Rock Creek at Hwy 8 Decomposed terrestrial 

detritus

Decomposed non-woody 

plant material in stream

05-31-00

C 0 U -29.70 4.97 21.13

342 Fanno Creek at Durham City Park Suspended sediment

— 05-31-00

A 0 U -31.72 4.14 7.53

342 Fanno Creek at Durham City Park Suspended sediment

— 05-31-00

B 0 U -31.82 4.59 7.31

342 Fanno Creek at Durham City Park Suspended sediment

— 05-31-00

C 0 U -31.92 4.56 7.93

343 Fanno Creek at Durham City Park Bed sediment

— 05-31-00

A 0 U -29.11 4.30 10.62

343 Fanno Creek at Durham City Park Bed sediment

— 05-31-00

B 0 U -28.45 4.13 12.31

343 Fanno Creek at Durham City Park Bed sediment

— 05-31-00

B 1 U -28.42 3.97 10.38

343 Fanno Creek at Durham City Park Bed sediment

— 05-31-00

C 0 U -28.35 4.11 11.27

344 Rock Creek Wastewater Treatment Facility WWTF effluent 

particulate

— 06-01-00

A 0 U -27.57 10.14

L 8.40

E

344 Rock Creek Wastewater Treatment Facility WWTF effluent 

particulate

— 06-01-00

B 0 U -26.93 10.25 5.94

344 Rock Creek Wastewater Treatment Facility WWTF effluent 

particulate

— 06-01-00

C 0 U -27.72 10.02

L 6.33

E

345 Durham Wastewater Treatment Facility WWTF effluent 

particulate

— 06-01-00

A 0 U -28.56 7.43 6.86

E
Appendix A. 55

Appendix A. Values of stable isotope compositions (δ13C, δ15N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split samples.—Continued

ID Site name Sample type Sample detail Date Sample split Lab rep Acidified δ13C δ15N δ15N qualifier C/N C/N qualifier

345 Durham Wastewater Treatment Facility WWTF effluent 

particulate

— 06-01-00 B 0 U -27.99 7.23 6.11 E

345 Durham Wastewater Treatment Facility WWTF effluent 

particulate

— 06-01-00 C 0 U -27.28 6.79 6.17

401 Tualatin River at RM 5.5 (Stafford Road) Seston, >80 μm — 08-13-98 A 0 A -35.10 9.59 4.38401 Tualatin River at RM 5.5 (Stafford Road) Seston, >80 μm — 08-13-98 A 1 A -35.03 9.57 4.38401 Tualatin River at RM 5.5 (Stafford Road) Seston, >80 μm — 08-13-98 A 0 U -35.10 8.96 4.96401 Tualatin River at RM 5.5 (Stafford Road) Seston, >80 μm — 08-13-98 A 1 U -35.15 8.88 5.05401 Tualatin River at RM 5.5 (Stafford Road) Seston, >80 μm — 08-13-98 B 0 A -34.89 9.47 4.67401 Tualatin River at RM 5.5 (Stafford Road) Seston, >80 μm — 08-13-98 C 0 A -34.92 9.58 4.31402 Tualatin River at RM 5.5 (Stafford Road) Periphyton Species not identified 08-13-98 A 0 A -32.72 12.49 4.49402 Tualatin River at RM 5.5 (Stafford Road) Periphyton Species not identified 08-13-98 B 0 A -33.36 12.86 4.15402 Tualatin River at RM 5.5 (Stafford Road) Periphyton Species not identified 08-13-98 B 1 A -32.69 13.17 4.39402 Tualatin River at RM 5.5 (Stafford Road) Periphyton Species not identified 08-13-98 C 0 A -33.81 13.09 3.97403 Tualatin River at RM 20.3 Periphyton Species not identified 08-18-98 A 0 A -18.50 5.78 9.73403 Tualatin River at RM 20.3 Periphyton Species not identified 08-18-98 B 0 A -18.47 5.98 10.05403 Tualatin River at RM 20.3 Periphyton Species not identified 08-18-98 C 0 A -18.28 5.63 10.25404 Henry Hagg Lake Seston, >80 μm — 08-11-98 A 0 A -26.23 6.75 9.12404 Henry Hagg Lake Seston, >80 μm — 08-11-98 A 1 A -26.36 7.03 8.34404 Henry Hagg Lake Seston, >80 μm — 08-11-98 B 0 A -26.20 6.67 9.12404 Henry Hagg Lake Seston, >80 μm — 08-11-98 C 0 A -26.58 7.17 8.83405 Tualatin River at RM 24.5 Duckweed Duckweed sorted from mat 09-29-98 A 0 A -29.41 6.89 9.82405 Tualatin River at RM 24.5 Duckweed Duckweed sorted from mat 09-29-98 B 0 A -29.51 6.89 10.12405 Tualatin River at RM 24.5 Duckweed Duckweed sorted from mat 09-29-98 B 1 A -29.33 6.74 10.25405 Tualatin River at RM 24.5 Duckweed Duckweed sorted from mat 09-29-98 C 0 A -29.51 6.76 10.45406 Tualatin River at RM 5.5 (Stafford Road) Suspended sediment — 09-17-98 A 0 A -32.97 7.42 7.01406 Tualatin River at RM 5.5 (Stafford Road) Suspended sediment — 09-17-98 B 0 A -33.26 7.31 6.16406 Tualatin River at RM 5.5 (Stafford Road) Suspended sediment — 09-17-98 C 0 A -33.02 7.41 6.60407 Tualatin River at RM 26.9 (Scholls) Suspended sediment — 09-17-98 A 0 A -27.98 5.26 9.22407 Tualatin River at RM 26.9 (Scholls) Suspended sediment — 09-17-98 A 1 A -27.99 4.66 9.80407 Tualatin River at RM 26.9 (Scholls) Suspended sediment — 09-17-98 B 0 A -28.09 5.11 9.29407 Tualatin River at RM 26.9 (Scholls) Suspended sediment — 09-17-98 C 0 A -27.73 4.66 10.79

408.1 Tualatin River at RM 5.5 (Stafford Road) Bed sediment Core 1, top 3 cm 08-20-98 A 0 U -27.40 4.59 18.56 E408.1 Tualatin River at RM 5.5 (Stafford Road) Bed sediment Core 1, top 3 cm 08-20-98 A 1 U -27.41 5.17 16.25 E
56 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon Appendix A. Values of stable isotope compositions (δ13C, δ15N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split samples.—Continued ID Site name Sample type Sample detail Date Sample split Lab rep Acidified δ13C δ15N δ15N qualifier C/N C/N qualifier 408.2 Tualatin River at RM 5.5 (Stafford Road) Bed sediment Core 2, top 2 cm 08-20-98

A 0 U -27.74 4.64

L 13.40

E

408.2 Tualatin River at RM 5.5 (Stafford Road) Bed sediment Core 2, top 2 cm 08-20-98

A 1 U -27.80 4.99

L 17.60

E

408.3 Tualatin River at RM 5.5 (Stafford Road) Bed sediment Core 3, top 1 cm 08-20-98

A 0 A -27.97 5.05

L 10.52

E

408.3 Tualatin River at RM 5.5 (Stafford Road) Bed sediment Core 3, top 1 cm 08-20-98

A 1 A -28.02 5.06

L 10.36

E

408.3 Tualatin River at RM 5.5 (Stafford Road) Bed sediment Core 3, top 1 cm 08-20-98

A 0 U -27.99 6.24

L 12.40

E

408.3 Tualatin River at RM 5.5 (Stafford Road) Bed sediment Core 3, top 1 cm 08-20-98

A 1 U -28.09 5.32

L 15.86

E

408.3 Tualatin River at RM 5.5 (Stafford Road) Bed sediment Core 3, top 1 cm 08-20-98

A 2 U -27.29 5.03

L 12.83

E

408.3 Tualatin River at RM 5.5 (Stafford Road) Bed sediment Core 3, top 1 cm 08-20-98

A 3 U -28.16 4.19

L 11.83

E

408.4 Tualatin River at RM 5.5 (Stafford Road) Bed sediment Core 4, top 3 cm 08-20-98

A 0 A -27.82 3.95 12.99

408.5 Tualatin River at RM 5.5 (Stafford Road) Bed sediment Core 5, top 2 cm 08-20-98

A 0 A -28.19 4.06 15.09

408.6 Tualatin River at RM 5.5 (Stafford Road) Bed sediment Core 6, top 1 cm 08-20-98

A 0 A -28.34 3.93 13.34

408.7 Tualatin River at RM 5.5 (Stafford Road) Bed sediment Core 7, top 3 cm 08-20-98

A 0 A -27.94 3.27 12.99

E

408.7 Tualatin River at RM 5.5 (Stafford Road) Bed sediment Core 7, top 3 cm 08-20-98

A 1 A -28.18 3.25 12.99

E

408.8 Tualatin River at RM 5.5 (Stafford Road) Bed sediment Core 8, top 2 cm 08-20-98

A 0 A -28.41 4.66 13.07

408.9 Tualatin River at RM 5.5 (Stafford Road) Bed sediment Core 9, top 1 cm 08-20-98

A 0 A -28.32 4.18 12.46

409.1 Tualatin River at RM 26.9 (Scholls) Bed sediment Core 1, top 3 cm 08-18-98

A 0 A -27.93 3.79 12.54

409.2 Tualatin River at RM 26.9 (Scholls) Bed sediment Core 2, top 2 cm 08-18-98

A 0 A -27.47 3.66 11.67

409.3 Tualatin River at RM 26.9 (Scholls) Bed sediment Core 3, top 1 cm 08-18-98

A 0 A -27.74

—

—

409.3 Tualatin River at RM 26.9 (Scholls) Bed sediment Core 3, top 1 cm 08-18-98

A 1 A -27.93

—

—

409.3 Tualatin River at RM 26.9 (Scholls) Bed sediment Core 3, top 1 cm 08-18-98

A 2 A -27.83 6.03 11.25

409.3 Tualatin River at RM 26.9 (Scholls) Bed sediment Core 3, top 1 cm 08-18-98

A 3 A -27.86 5.80 11.36

409.3 Tualatin River at RM 26.9 (Scholls) Bed sediment Core 3, top 1 cm 08-18-98

A 0 U -27.79 5.24 11.94

409.4 Tualatin River at RM 26.9 (Scholls) Bed sediment Core 4, top 3 cm 08-18-98

A 0 A -27.15 3.10 15.46

E

409.5 Tualatin River at RM 26.9 (Scholls) Bed sediment Core 5, top 2 cm 08-18-98

A 0 A -27.28 3.29 16.28

E

409.6 Tualatin River at RM 26.9 (Scholls) Bed sediment Core 6, top 1 cm 08-18-98

A 0 A -27.22 2.96 17.59

E

409.7 Tualatin River at RM 26.9 (Scholls) Bed sediment Core 7, top 3 cm 08-18-98

A 0 A -27.24

—

—

409.7 Tualatin River at RM 26.9 (Scholls) Bed sediment Core 7, top 3 cm 08-18-98

A 1 A -27.41

—

—

409.7 Tualatin River at RM 26.9 (Scholls) Bed sediment Core 7, top 3 cm 08-18-98

A 2 A -27.57 5.01 14.22

409.7 Tualatin River at RM 26.9 (Scholls) Bed sediment Core 7, top 3 cm 08-18-98

A 3 A -27.53 5.39 14.33

409.7 Tualatin River at RM 26.9 (Scholls) Bed sediment Core 7, top 3 cm 08-18-98

A 0 U -27.44 4.98 14.33

409.8 Tualatin River at RM 26.9 (Scholls) Bed sediment Core 8, top 2 cm 08-18-98

A 0 A -27.58 3.16 19.24

409.9 Tualatin River at RM 26.9 (Scholls) Bed sediment Core 9, top 1 cm 08-18-98

A 0 A -27.75 3.30

L 16.54

E
Appendix A. 57

Appendix A. Values of stable isotope compositions (δ13C, δ15N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split samples.—Continued

ID Site name Sample type Sample detail Date Sample split Lab rep Acidified δ13C δ15N δ15N qualifier C/N C/N qualifier

410 Jackson Bottom (between Miller Swale and 

holding pond)

Soil Chehalis soil 10-06-98 A 0 A -26.81 5.67 10.61

410 Jackson Bottom (between Miller Swale and 

holding pond)

Soil Chehalis soil 10-06-98 B 0 A -26.50 5.40 10.77

410 Jackson Bottom (between Miller Swale and 

holding pond)

Soil Chehalis soil 10-06-98 B 1 A -26.59 5.56 10.60

410 Jackson Bottom (between Miller Swale and 

holding pond)

Soil Chehalis soil 10-06-98 C 0 A -26.64 5.13 10.48

411 Zurcher Farm (FernhillRoad near Tualatin River) Soil Wapato soil 10-06-98 A 0 A -26.07 3.79 12.23411 Zurcher Farm (FernhillRoad near Tualatin River) Soil Wapato soil 10-06-98 B 0 A -26.09 4.63 11.19411 Zurcher Farm (FernhillRoad near Tualatin River) Soil Wapato soil 10-06-98 C 0 A -25.84 4.50 11.56411 Zurcher Farm (FernhillRoad near Tualatin River) Soil Wapato soil 10-06-98 C 1 A -26.10 5.01 11.89411 Zurcher Farm (FernhillRoad near Tualatin River) Soil Wapato soil 10-06-98 C 2 A -26.16 6.09 10.24411 Zurcher Farm (FernhillRoad near Tualatin River) Soil Wapato soil 10-06-98 C 3 A -26.12 6.47 9.88411 Zurcher Farm (FernhillRoad near Tualatin River) Soil Wapato soil 10-06-98 C 0 U -26.05 5.10 9.85

412 Oregon Graduate Institute (near Bronson Creek) Soil Woodburn soil 10-06-98 A 0 A -27.19 -1.08 20.89412 Oregon Graduate Institute (near Bronson Creek) Soil Woodburn soil 10-06-98 B 0 A -27.13 -0.75 20.82412 Oregon Graduate Institute (near Bronson Creek) Soil Woodburn soil 10-06-98 C 0 A -27.27 -0.77 21.54413 Jackson Bottom (between Miller Swale and 

holding pond)

Leaf litter Oregon Ash leaf litter 10-06-98 A 0 U -30.43 2.34 25.82

413 Jackson Bottom (between Miller Swale and 

holding pond)

Leaf litter Oregon Ash leaf litter 10-06-98 B 0 U -30.54 2.33 23.47

413 Jackson Bottom (between Miller Swale and 

holding pond)

Leaf litter Oregon Ash leaf litter 10-06-98 C 0 U -30.36 2.10 25.48

413 Jackson Bottom (between Miller Swale and 

holding pond)

Leaf litter Oregon Ash leaf litter 10-06-98 C 1 U -30.30 1.97 —

414 Tualatin River at RM 67.8 (Cherry Grove) Coniferous litter Western Red Cedar litter 10-06-98 A 0 U -26.58 -0.33 43.88414 Tualatin River at RM 67.8 (Cherry Grove) Coniferous litter Western Red Cedar litter 10-06-98 B 0 U -26.83 -0.66 40.11414 Tualatin River at RM 67.8 (Cherry Grove) Coniferous litter Western Red Cedar litter 10-06-98 C 0 U -27.00 0.38 35.65415 Tualatin River at RM 67.8 (Cherry Grove) Leaf litter Alder leaf litter 10-06-98 A 0 U -29.56 -1.54 27.21415 Tualatin River at RM 67.8 (Cherry Grove) Leaf litter Alder leaf litter 10-06-98 A 1 U -29.57 -1.71 28.40415 Tualatin River at RM 67.8 (Cherry Grove) Leaf litter Alder leaf litter 10-06-98 B 0 U -29.48 -1.62 27.13415 Tualatin River at RM 67.8 (Cherry Grove) Leaf litter Alder leaf litter 10-06-98 C 0 U -29.37 -1.68 30.15416 Patton Valley Road (N side, 1 mi E Cherry 

Grove)

Coniferous litter Douglas Fir litter 10-06-98 A 0 U -27.32 -0.79 55.74
58 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon Appendix A. Values of stable isotope compositions (δ13C, δ15N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split samples.—Continued ID Site name Sample type Sample detail Date Sample split Lab rep Acidified δ13C δ15N δ15N qualifier C/N C/N qualifier 416 Patton Valley Road (N side, 1 mi E Cherry Grove) Coniferous litter Douglas Fir litter 10-06-98

B 0 U -27.40 -0.50 58.32

416 Patton Valley Road (N side, 1 mi E Cherry 

Grove)

Coniferous litter Douglas Fir litter 10-06-98

B 1 U -27.55 -0.41 57.19

416 Patton Valley Road (N side, 1 mi E Cherry 

Grove)

Coniferous litter Douglas Fir litter 10-06-98

C 0 U -27.36 -0.49 58.59

417 Patton Valley Road (N side, 1 mi E Cherry 

Grove)

Woody material Douglas fir twigs 10-06-98

A 0 U -26.04 -2.94 74.40

417 Patton Valley Road (N side, 1 mi E Cherry 

Grove)

Woody material Douglas fir twigs 10-06-98

B 0 U -26.55 -2.75

L 86.49

417 Patton Valley Road (N side, 1 mi E Cherry 

Grove)

Woody material Douglas fir twigs 10-06-98

C 0 U -26.72 -2.82 48.21

417 Patton Valley Road (N side, 1 mi E Cherry 

Grove)

Woody material Douglas fir twigs 10-06-98

C 1 U -26.62 -2.96 57.48

418 Rock Creek Wastewater Treatment Facility WWTF effluent 

particulate

— 10-06-98

A 0 A -26.75 11.82 3.54

418 Rock Creek Wastewater Treatment Facility WWTF effluent 

particulate

— 10-06-98

B 0 A -26.70 10.91 4.85

418 Rock Creek Wastewater Treatment Facility WWTF effluent 

particulate

— 10-06-98

C 0 A -26.49 11.88 5.27

418 Rock Creek Wastewater Treatment Facility WWTF effluent 

particulate

— 10-06-98

C 1 A -26.62 11.84 5.09

419 Tualatin River at RM 5.5 (Stafford Road) Bryozoan

— 08-13-98

A 0 A -35.63 16.13 3.65

419 Tualatin River at RM 5.5 (Stafford Road) Bryozoan

— 08-13-98

B 0 A -35.40 16.22 3.66

419 Tualatin River at RM 5.5 (Stafford Road) Bryozoan

— 08-13-98

C 0 A -35.07 16.26 3.63

419 Tualatin River at RM 5.5 (Stafford Road) Bryozoan

— 08-13-98

C 1 A -35.32 15.92 3.58
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For more information concerning the research in this report, contact the

 Director, Oregon Water Science Center

U.S. Geological Survey

2130 SW 5th Avenue

Portland, Oregon 97201

http://or.water.usgs.gov
Bonn and Rounds— Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon—Scientific Investigations Report 2010–5154