Water Chemistry in a Nutrient and Sediment Control System Near Owasco,
New York

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U.S. GEOLOGICAL SURVEY\
Open-File Report 99-xxxx

Prepared in cooperation with the Cayuga County Soil and Water
Conservation District

Water Chemistry in a Nutrient and Sediment Control System Near Owasco,
New York

*By* Stephen C. Komor

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

U.S. GEOLOGICAL SURVEY\
Open-File Report 99-xxxx

Prepared in cooperation with the Cayuga County Soil and Water
Conservation District

Ithaca, New York\
1999

U.S. DEPARTMENT OF THE INTERIOR

Bruce Babbitt, Secretary

U.S. GEOLOGICAL SURVEY

Charles Groat, Director

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

For additional information Copies of this report can be\
write to: purchased from:\
\
U.S. Geological Survey, WRD U.S. Geological Survey\
Books and Open-File Reports Section Federal Center Box 25425\
Denver, CO 80225

CONTENTS

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

Introduction...................................................................................
2

Site
Description...........................................................................\...
3

Field
sampling...............................................................................
4

Stable Isotopes and Reactions of Nutrient
Species................................ 6

Water chemistry in the
NSCS............................................................ 8

Nitrogen, phosphorous, total solids, and fecal coliform bacteria...... 8

Major and trace ions, redox conditions, and saturation indices........ 9

Isotopes..............................................................................
10

Drawbacks of Study
Approach........................\................................. 11

Water-quality
treatment....................................\...............................
12

Interpretations of water chemistry and performance of the
NSCS............ 13

System
inlet........................................................................
13

System inlet to shallow
pond................................................... 13

Shallow pond to pond
connection............................................. 14

Pond connection to deep pond
outlet........................................ 14

Deep pond outlet to system
outlet............................................ 14

Conclusions and recommendations for future
monitoring....................... 15

References
Cited...........................................................................
17

Figures

1\. Site location, main components of the NSCS, and sampling
locations............ 3

2\. Concentration variations of nitrogen species at the five sampling
locations in the
NSCS.....................................................................................
8

3\. Concentrations of phosphorous species, total solids, and fecal
coliform bacteria at the five sampling
locations................................................ 9

4\. Piper diagram showing major element proportions in water from the
NSCS... 9

5\. Saturation indices of selected
minerals................................................. 10

6\. Values of δ^18^O and δD from the later two samplings in the
NSCS............... 10

7\. Histogram of δ^15^N~nitrate~ and δ^15^N~ammonium~ values in the
NSCS............................ 11

Tables

1\. Water chemistry in nutrient and sediment control
system....................................\...5

2a. Treatment values in
NSCS............\..............................................................12

2b. Average concentration change in each NSCS component as percentage of
total concentration change in
NSCS............\...................................................12

CONVERSION FACTORS

**Multiply By To Obtain**

*Length*

foot (ft) 0.3048 meter

*Area*

square mile (mi^2^) 2.590 square kilometer

acre 0.4046 hectare

*Temperature*

degrees Fahrenheit (°F) (5/9)(°F -- 32) degrees Celcius (°C)

**Abstract**

A constructed wetland called a Nutrient and Sediment Control System
(NSCS) was installed near the town of Owasco, New York to reduce
nutrients and pathogens in runoff from a cattle pasture. To evaluate the
performance of the NSCS, constituent concentrations in stormflow and
snowmelt runoff were measured three times at five locations in the
wetland. These locations were: 1) at the system inlet; 2) after the
initial sediment basin and grass buffer strip; 3) after the shallow pond
(maximum depth = 0.46 m); 4) after the deep pond (maximum depth = 2.3
m); and 5) at the system outlet. Water at the system inlet had elevated
concentrations of N and P species and fecal coliform bacteria, and at 2
sampling times nitrogen-isotope values of nitrate of 11.4 and 23.8‰.
These chemical characteristics indicate that pasture runoff contained
dissolved and suspended constituents from manure. Constituent
concentrations that decreased from the system inlet to outlet included
suspended ammonia + organic N, nitrate, suspended P, Ca, K, sulfate, and
fecal coliform bacteria. The decreased concentrations were probably due
to physical settling and filtration, adsorption, and biogeochemical
reactions such as denitrification. Constituent concentrations that
increased in the NSCS included ammonium, dissolved organic N, and
dissolved P. The increases may be due to turbulent resuspension of
particulates from the pond bottoms and biogeochemical reactions such as
ammonification.

**Introduction**

Owasco Lake in Cayuga County, New York (fig. 1) is an important water
supply for Auburn, New York and recreational resource for regional
communities. The lake covers approximately 2,745 hectares (6,784 acres)
and drains a watershed of 531 km^2^ (205 mi^2^). Water-quality problems
include high turbidity, which has caused numerous beach closures, and
excessive nutrient concentrations, which promote weed growth in parts of
the lake. Dutch Hollow Brook is a major contributor of suspended and
bed-load sediments on the eastern side of the lake. The sediment plume
that emanates from the mouth of Dutch Hollow Brook may impair
fish-spawning areas (New York State Department of Environmental
Conservation, 1996a).

Runoff from agricultural land is a significant source of non-point
source pollution in many areas. Pollutants from agricultural land
include nitrogen (N) and phosphorous (P) from fertilizers and animal
manure, pathogens from manure, pesticides, and sediments. Reducing
agricultural pollutants is important for improving water quality in many
streams and lakes. Pollutants that compromise water quality are believed
to come in part from agricultural sources (New York State Department of
Environmental Conservation, 1996b). Such pollutants include nutrients
and pathogens from manure stored at animal feedlots and applied to
crops.

Several systems have been developed to treat agricultural runoff. These
include vegetated buffer strips (Chaubey, Edwards, and others, 1994;
Magette, Brinsfield, and others, 1989; Robinson, Ghaffarzadeh, and
Cruse, 1996; Young, Huntrods, and Anderson, 1980), settling basins
(Edwards, Owens, and White, 1983), tiled infiltration beds (Edwards,
Owens, and others, 1986), and constructed wetlands (Higgins, Rock, and
Bouchard, 1993). Collectively these systems are termed best management
practices or BMPs. BMPs are designed to reduce pollutant concentrations
and loads in runoff by infiltration into the soil, physical filtration
by grass or other vegetation, adsorption on to soil and plants,
bacterial decomposition, plant uptake, and sediment deposition (Dillaha,
Sherrard, and others, 1988; Phillips, 1989). An added consideration in
cold regions is the performance of BMPs when the ground is frozen and no
vegetation is present (Ketchum, Cunningham, and Irvine, 1981; Martel,
Jenkins, and Palazzo, 1980). Under these conditions, infiltration and
vegetative filtration and uptake are minimal and rates of bacterial
decomposition are reduced. Therefore, runoff from winter and early
spring snowmelts is treated less effectively than runoff during warmer
periods. Another concern is that BMPs that include infiltration beds may
reduce pollutants in runoff at the expense of ground-water quality
(Schellinger and Clausen, 1992).

A new type of constructed wetland called a Nutrient and Sediment Control
System (NSCS) was developed by the U.S. Department of Agriculture Soil
Conservation Service to treat cropland runoff in cold climates
(Wengrzynek, 1995). The NSCS consists of a series of grass buffer strips
and ponds that treat runoff by biochemical and physical means.
Monitoring of an NSCS in Maine found annual removal rates of phosphorous
and suspended solids exceeded 90 per cent on a mass basis (Higgins and
other, 1993).

This report describes the results of water-quality monitoring to
evaluate the performance of an NSCS installed to treat runoff from a cow
pasture near the Town of Owasco in the Owasco Lake watershed. Although
the NSCS design was originally developed and optimized to treat cropland
runoff, Cayuga County personnel believed that the NSCS might also prove
effective in treating pasture runoff.

**Site Description**

The study site lies within the Dutch Hollow Brook watershed, which
includes about 77 km^2^ (29.8 mi^2^) of agricultural land, rural homes,
and undeveloped swamps, forests and fields. The NSCS was installed in an
area of well-drained silt-loam soils (United States Department of
Agriculture, 1971) adjacent to a cattle pasture. The pasture covers
about 30 hectares (73 acres) and constitutes the contributing watershed
to the NSCS. About 120 cows graze on the pasture year-round.

The NSCS (fig. 1) is graded and contoured to ensure that water flows
sequentially through the various components from the system inlet to the
system outlet. Runoff from the contributing watershed is directed by a
series of ditches and soil berms into the system inlet. The inlet leads
into a sediment basin where large particles settle out. Runoff then
turns 90° and flows across a level-lip spreader of crushed stone that
distributes water laterally across the width of the NSCS. The resulting
sheet flow moves across the first grass buffer strip towards the shallow
pond. The shallow pond ranges in depth from zero (saturated soil) at the
edge of the grass strip to about 0.5 m (1.5 ft) near the connection with
the deep pond. The deep pond has a maximum depth of about 2.3 m (7.5
ft). The bottoms of the shallow and deep ponds consist of compacted
soils excavated from the surrounding area; neither pond is lined. When
the water level in the deep pond rises above the designed maximum level,
it drains into a vertical drop-inlet pipe that leads under an
embankment, across another level-lip spreader, and on to a second grass
buffer strip. Water exits through the system outlet and discharges into
a tributary of Dutch Hollow Brook.

**Field sampling**

Water samples were collected on January 6 and February 18, 1998 during
winter thaws when water from snowmelt and light rain flowed through the
NSCS. At these times, the soil was partially frozen, grass in the buffer
strips was brown and flat lying, and the ponds were partially
ice-covered. The air temperature was about 2-4°C (35-40°F). Samples were
also collected on May 12, 1998 after several days of continuous rain.
Grass on the buffer strips was green and about 30 cm (1 foot) high. The
air temperature was about 10 °C (50 °F). Although flow volumes were not
measured, visual observations of flow depths at the system inlet and
outlet suggested that each of the three samplings was done soon after
runoff volumes had peaked.

Grab samples were collected at five stations in the NSCS: 1) the system
inlet; 2) the upgradient edge of the shallow pond; 3) the connection
between the shallow and deep ponds; 4) the outlet of the deep pond's
drain; and 5) the system outlet (fig. 1). Samples from all five sites
were collected in the space of about 90 minutes. Field measurements were
made of water temperature, pH, and alkalinity. Water samples were
collected for analysis of nutrients (N and P species); major cations and
anions; silica, manganese and iron; and total solids. Also measured were
N isotope values of nitrate (δ^15^N~nitrate~ values); isotopic
compositions of ammonium (δ^15^N~ammonium~ values) were measured in
samples that contained insufficient nitrate for the analytical
technique. Selected samples were analyzed for oxygen isotopes (δ^18^O
values) and hydrogen isotopes (δD values) in water. Water collected on
May 12 was analyzed for fecal coliform bacteria concentrations. A sample
consisting of certified blank water was analyzed with the February 18
samples to ensure that sampling equipment, including pumps, tubing,
filters and sample containers, did not introduce contaminants into
runoff samples submitted for chemical analyses. Constituent
concentrations in this equipment blank were generally less than 0.1
mg/L, which is much less than those in runoff (Table 1). Ionic
concentrations in the January 6 sample from station 3 are anomalously
low, probably due to a sampling problem of unknown origin.

Water was filtered, preserved and chilled according to established
protocols (Wilde and others, 1999) and shipped for analysis to U.S.
Geological Survey laboratories in Arvada, Colorado and Reston, Virginia.
Analyses of nutrients, major ions and solids were done by standard
methods (Fishman and Friedman, 1989). Values of δ^18^O were analyzed by
the method of Epstein and Mayeda (1953) and δD values by the method of
Coplen et al. (1991). Values of δ^15^N were analyzed by Global
Geochemistry in Canoga Park, California by the method of Cline and
Kaplan (1975).

**Stable Isotopes and Reactions of Nutrient Species**

The delta (δ) notation for stable isotope values is defined as follows:

$\text{d = }\left\lbrack \frac{R_{\text{sample}}\text{ - }R_{\text{standard}}}{R_{\text{standard}}} \right\rbrack ´\text{ 1000}$
(1)

where *R~sample~* and *R~standard~* are ^18^O/^16^O, D/H, or ^15^N/^14^N
in the sample or standard. Standards are Vienna Standard Mean Ocean
Water for δ^18^O and δD values and air for δ^15^N values. Isotopic
measurements are quoted in units of parts per thousand and designated by
the symbol ‰. The error associated with isotopic measurements is ± 1‰
for δD values and ± 0.1‰ for δ^18^O and δ^15^N values.

Stable oxygen and hydrogen isotopes are useful tracers of water sources
(Gat and Gonfiantini, 1981). Water sources that contribute to runoff in
the NSCS include rain, snowmelt, and possibly ground water. On a plot of
δ^18^O versus δD, recent rain and snow compositions plot along a line
with a slope of 8 and an intercept of 10. This line is termed the Global
Meteoric Water Line (GMWL; Craig, 1961). Evaporation affects meteoric
water by driving its δ^18^O and δD values to the right of the GMWL along
trends with slopes less than 8 (Craig, 1961; Gat and Gonfiantini, 1981).

Stable N isotopes can help identify sources and chemical transformations
of N (Heaton, 1986). Possible sources of nitrate and ammonium in runoff
in the NSCS include rain and snowmelt, inorganic fertilizer, natural
soil materials, and cattle manure. General ranges of δ^15^N~nitrate~
values for these sources are: wetfall and dryfall deposition, -15 to
15‰; nitrate derived from inorganic fertilizers such as anhydrous
ammonia (NH~3~) or ammonium nitrate (NH~4~NO~3~), -4‰ to 4‰; natural
soil organic material, 4‰ to 9‰; and manure, 10‰ to 22‰ (Heaton, 1986;
Macko and Ostrom, 1994). Values of δ^15^N~nitrate~ and δ^15^N~ammonium~
are affected by N transformations such as the following:

Ammonification

$\begin{array}{r}
\text{CH}_{2}O(\text{NH}_{3})\text{  +   O}\text{   }Û\text{   NH}_{4}^{+}\text{  +  HCO}_{3}^{-} \\
\text{    organic}\text{             }\text{dissolved      ammonium   bicarbonate} \\
\text{    material                oxygen}
\end{array}$ (2)

Nitrification

$\begin{array}{r}
\text{    NH}_{4}^{+}\text{ +   2O}\text{   }Û\text{   NO}_{3}^{-}\text{  +  2H}^{+}\text{ + H}_{2}O \\
\text{ammonium  dissolved          nitrate                           water} \\
\text{                      oxygen}
\end{array}$ (3)

Denitrification

$\begin{array}{r}
4\text{NO}_{3}^{-}\text{ + 5CH}_{2}\text{O }Û\text{ 2N}_{2}(g)\text{ + 5HCO}_{3}^{-}\text{  + H}_{2}O \\
\text{nitrate          organic}\text{          }\text{nitrogen      bicarbonate        water} \\
\text{                    material               gas}
\end{array}$ (4)

Ammonification converts organic N to ammonium in oxygenated water at pε
values (redox potentials) of about 4 to 14. Nitrification converts
ammonium to nitrate under oxygenated conditions. Denitrification reduces
nitrate to N gas in oxygen-deficient environments at pε values of about
-3 to 13 (Stumm and Morgan, 1981). Each reaction enriches ^15^N in
N-bearing reactants and ^14^N in N-bearing products. Consequently,
δ^15^N values of N species on the left hand sides of the equations
increase whereas those on the right hand sides decrease.

A reaction similar to (2) describes the oxidation of organic P to
dissolved P:

$\begin{array}{r}
\text{CH}_{2}O(H_{3}\text{PO}_{4})_{2}\text{  +   O}\text{   }Û\text{  2 H}_{2}\text{PO}_{4}^{-}\text{  +   HCO}_{3}^{-}\text{ + 3H}^{+} \\
\text{       organic}\text{                 }\text{dissolved           dissolved         bicarbonate} \\
\text{       material                     oxygen          phosphorous}
\end{array}$ (5)

**Water chemistry in the NSCS**

[Nitrogen, phosphorous, total solids, and fecal coliform
bacteria]{.underline} - Nitrate concentrations decreased from the system
inlet to the shallow pond (stations 1 to 2), and remained roughly
constant in rest of the system (stations 3 to 5; fig. 2a; bold lines in
fig. 2 show average compositions). Nitrate concentrations in system
inflow ranged from 2.0 to 12.2 mg/L and 0.0 to 0.6 mg/L in system
outflow. System outflow met the New York State surface-water-quality
standard for nitrate of 10 mg/L as N (New York State Department of
Environmental Conservation, 1994).

Ammonium concentrations varied within restricted ranges at the system
inlet (5.7 to 10.5 mg/L) and shallow pond (7.0 to 8.4 mg/L; fig. 2b). In
contrast, ammonium concentrations ranged from 1.0 to 50.2 mg/L at the
pond connection; 3.4 to 47.6 mg/L at the deep pond outlet; and 2.5 to
47.6 mg/L at the system outlet. Ammonium concentrations in system
outflow exceeded the state standard of 2 mg/L as N (New York State
Department of Environmental Conservation, 1994).

Dissolved organic N concentrations ranged from 4.7 to 8.2 mg/L at the
system inlet and 3.8 to 12.4 mg/L at the system outlet (fig. 2c). The
largest concentration was 24.2 mg/L in water collected on May 12 from
the shallow pond. The concentrations of suspended ammonia plus organic N
were measured together (fig. 2d). The sums of these constituents were
14.6 to 31.9 mg/L at the system inlet and 3.1 to 19.6 mg/L at the system
outlet. The largest concentration was measured in system inflow on
January 6.

Contributions of nitrate and ammonium in rain and snowmelt to those in
runoff can be estimated from concentrations in composite wetfall and
dryfall samples collected near Rochester, New York (Hornlein, Szabo, and
others, 1997). In 19 samples collected from October, 1996 to September,
1997, nitrate-plus-nitrite concentrations averaged 1.0 mg/L (standard
deviation = 0.8 mg/L) and ammonium concentrations averaged 0.6 mg/L
(standard deviation = 0.4 mg/L). These data indicate that rain and
snowmelt may have contributed about 7 to 43% of the nitrate and 6 to 11%
of the ammonium in runoff entering the NSCS.

Dissolved P concentrations were 2.9 to 4.0 mg/L in system inflow and 1.0
to 12.3 mg/L in outflow (fig. 3a). Suspended P concentrations were 4.5
to 8.0 mg/L in system inflow and 0.8 to 3.6 mg/L in system outflow (fig.
3b). Most of the decrease in suspended P concentrations occurred between
the system inlet and the shallow pond or pond connection.

Total solids were 548 to 1,100 mg/L in system inflow and 423 to 946 mg/L
in system outflow (fig. 3c). Total solids concentrations generally
decreased from the system inlet to the shallow pond, but increased from
the pond connection to the deep pond outlet. Fecal coliform bacteria
concentrations in runoff on May 12 decreased by three orders of
magnitude, from 2,025,000 colonies/100 ml in system inflow to 4,300
colonies in system outflow (fig. 3d). Most of the decrease was between
the shallow pond and the pond connection. The outflow concentration
exceeded the state standard of 200 colonies/100 ml (New York State
Department of Environmental Conservation, 1994).

[Major and trace ions, redox conditions, and saturation
indices]{.underline} - Major-ion proportions varied within narrow ranges
in runoff (fig. 4) and do not correlate with station location or
sampling date. Cation proportions, on a milliequivalent per liter basis,
averaged 44% Ca, 25% Mg, and 31% Na + K; anion proportions averaged 73%
CO~3~ + HCO~3~, 22% Cl, and 5% SO~4~. The water may be classified as a
calcium-bicarbonate type. Maximum concentrations of silica were 14 mg/L;
of manganese were 1,347 μg/L; and of iron were 1,200 μg/L.

To estimate redox conditions in the NSCS, pε values were calculated with
the PHREEQC (Parkhurst, 1995) computer program from the concentrations
of coexisting nitrate and ammonium. The pε values ranged from 5.0 to 7.2
and averaged 6.1 (Table 1). Saturation indices (SI values) show whether
minerals tend to precipitate, dissolve, or remain stable in water.
Mineral precipitation is indicated by SI values greater than zero,
dissolution by values less than zero, and stability by values equal to
zero. Uncertainties in SI's for common, well-studied minerals average
about ±0.5 SI units. SI values were calculated from water compositions
and PHREEQC (Parkhurst, 1995). Average SI values from the three
samplings at each station (fig. 5) indicate that quartz (SiO~2~),
calcite (CaCO~3~), amorphous iron hydroxide (Fe(OH)~3~ (a)) and
hydroxyapatite (Ca~5~(PO4)~3~OH) should precipitate in the NSCS, whereas
mangerite (MnOOH) and siderite (FeCO~3~) should dissolve.

[Isotopes]{.underline} - Values of δ^18^O and δD are available for
samples from stations 1, 3 and 4 on February 18 and all five stations on
May 12. The isotopic compositions of water from the system inlet plot
very close to the meteoric water line, as expected for rain or snowmelt
(Craig, 1961). The isotopic values decrease from the system inlet
(Station 1 on February 18) or shallow pond (Station 2 on May 12) to
downstream stations (stations 3-5; fig. 6, solid arrows). The trends of
the decreases roughly parallel the meteoric water line, suggesting the
isotopically light water in downstream stations was recent meteoric
water. The increase on 5/12/98 of δ^18^O and δD values from the system
inlet to the shallow pond along a trend with slope \<8 (fig. 6, dashed
arrow) reflects evaporation in the sediment basin and first grass
buffer.

Values of δ^15^N~nitrate~ at the system inlet reflect nitrate sources in
runoff from the cattle pasture. Values of δ^15^N~nitrate~ and
δ^15^N~ammonium~ at downstream stations in the NSCS also reflect nitrate
and ammonium sources, but probably are modified by reactions such as
(2) - (4). The δ^15^N~nitrate~ values at the system inlet are, in
chronological order, 11.4, 3.9, and 23.8‰ (fig. 7). Values of 11.4 and
23.8‰ are in the range of manure values, whereas 3.9‰ is the range of
nitrate from natural soil organic material, with no detectable manure
contribution. Values of δ^15^N~nitrate~ at the upgradient edge of the in
the shallow pond were 17.8‰ on January 6 and 16.6‰ on February 18. These
values represent substantial increases compared to those at the system
inlet on the corresponding dates.

**Drawbacks of Study Approach**

BMP performance is best evaluated in terms of contaminant masses because
they provide the most useful measure of the BMPs' effects on downstream
water bodies (Clausen and Meals, 1989). However, mass determinations
require continuous measurement of runoff volumes, which were not
determined in the present study. Instead, the performance of the NSCS
was evaluated from changes in constituent concentrations. Other studies
have also used constituent concentrations to evaluate changes in runoff
quality in various settings (Bingham and others, 1980; Dickey and others
1981; Gschlöβl and others, 1998; Smith, 1989; Srivastava and others,
1996). Nevertheless, it must be emphasized that treatment values
calculated from concentrations are inferior alternatives to mass-based
values.

A related shortcoming is the lack of information about the inflow and
outflow hydrographs when samples were collected. Stormflow hydrographs,
which show flow volumes as a function of time, typically have a steep
rising limb, a fairly sharp peak, and an extended declining limb (e.g.
.Chow et al, 1988). Samples collected at the 5 stations in the NSCS may
represent different positions on the hydrograph. Constituent
concentrations can vary with flow volumes, so some of the differences in
concentrations at the sampling sites in the NSCS may reflect dilution or
enrichment due to volumetric variations instead of chemical treatment.
This problem directly and fundamentally affects the calculated treatment
values, which must be viewed as preliminary and approximate.

**Water-quality treatment**

Difference between constituent concentrations at the system inlet and
outlet, divided by concentrations at the inlet, provide a measure of the
NSCS's treatment of pasture runoff (Table 2a). Positive treatment values
represent decreases in constituent concentrations at the outlet compared
to the inlet, and *vice versa* for negative treatment values. Values
within five percent of zero are considered to indicate no discernible
treatment. Average treatment values from the three samplings (Table 2a,
last row) may be better indicators of the NSCS's long-term performance
than values from each individual sampling.

Constituents with average positive treatment values include ammonia +
organic N, nitrate, suspended P, Ca, K, and sulfate. Fecal coliform
bacteria had a treatment value of 99.8 percent, which is listed as 100
percent in Table 2a because of rounding. Constituents with average
negative treatment values include ammonium, dissolved organic N, and
dissolved P. Constituents with no discernible treatment include
alkalinity, total solids, Mg, Na, and Cl.

To isolate the effect of each major component of the NSCS on water
chemistry, percentages of the net concentration changes that occurred in
each major component of the NSCS were computed for selected constituents
(Table 2b). Interpretations of the percent changes for nitrate and fecal
coliform are simplest because these constituents' concentrations
continually decrease from the system inlet to outlet (with the exception
of a small increase in fecal coliform concentrations from the deep pond
outlet to the system outlet). The information in Table 2b indicates that
86 percent of the overall decrease in average nitrate concentrations
occurred in the sediment basin and first grass strip, 12 percent in the
shallow pond, and about one percent each in the deep pond and second
grass strip. Similarly, 51 percent of the overall decrease in fecal
coliform concentrations occurred in the sediment basin and first grass
strip and 49 percent in the shallow pond. In contrast, the overall
increase in average ammonium concentrations breaks down into a 2 percent
decrease in the sediment basin and first grass strip, increases of 39
percent in the shallow pond and 69 percent in the deep pond, and a
decrease of 6 percent in the second grass strip. The overall increase in
average dissolved P concentrations comprises a 51 percent increase in
the first grass strip, a 6 percent increase in the shallow pond, a 117
percent increase in the deep pond, and a 74 percent decrease in the
second grass strip.

**Interpretations of water chemistry and performance of the NSCS**

[System inlet]{.underline} - Evidence that runoff at the system inlet
contains manure contaminants includes large concentrations of fecal
coliform bacteria, suspended ammonia plus organic N and suspended P, and
δ^15^N~nitrate~ values in the range of manure nitrate on January 6 and
May 12 (Table 1). The δ^15^N~nitrate~ value of 3.9‰ on February 18 may
reflect a dominance of nitrate from natural soil material and rainfall.

[System inlet to shallow pond]{.underline} - Decreases in concentrations
of ammonia plus organic N, suspended P, total solids and fecal coliform
bacteria from the system inlet to the shallow pond (figs. 2d, 3b, 3c,
3d) may reflect physical filtering and adsorption in the sediment basin
and first grass buffer strip. The decrease of nitrate concentrations on
all three sampling dates (fig. 2a) and increase of δ^15^N~nitrate~
values on January 6 and February 18 (fig. 7) are consistent with
denitrification in the first grass strip. Although denitrification
requires anaerobic conditions, which do not commonly obtain in surface
water, oxygen may have been depleted by biochemical reactions in shallow
saturated soils in the sediment basin and first grass strip. The
increase of average dissolved organic N and dissolved P concentrations
(figs. 2c, 3a) probably result from dissolution of particulate organic N
and P compounds. The increases of δ^18^O and δD values on May 12 (Fig 6)
are evidence for evaporation in the first grass strip, although there
was no corresponding increase in the concentration of dissolved
constituents from evaporative concentration.

[Shallow pond to pond connection]{.underline} - The increase of average
ammonium concentrations and decrease of average dissolved organic N
concentrations (figs. 2b, 2c) may be due to ammonification (Reaction 2).
The dramatic decrease of fecal coliform concentrations (fig. 3d) may be
due to settling of bacterial colonies in the shallow pond.

[Pond connection to deep pond outlet]{.underline} - Increases in average
concentrations of ammonium and dissolved P (Figs 2b, 3a) suggest
conversion of organic N and P to dissolved forms by Reactions 2 and 5,
respectively. Increases in the concentrations of suspended ammonia plus
organic N and total solids (Figs 2d, 3c) may be due to turbulent
resuspension of particulates from the pond bottom during runoff periods.
Although ammonium concentrations increased in the shallow and deep ponds
(fig. 2b), there was no corresponding increase in nitrate concentrations
(fig. 2a). This pattern indicates that nitrification (Reaction 3) did
not occur in the ponds, possibly because of anaerobic conditions or
because nitrification was offset by denitrification (Reaction 4).

Two explanations are possible for the decreases of δ^18^O and δD values
from the system inlet and shallow pond to downstream stations (fig. 6).
One is that the ponds contained larger proportions of snowmelt or rain
that formed under cold temperatures than water that entered the system
inlet on February 18 and May 12. Isotope compositions of meteoric water
decrease with air temperature (Dansgaard, 1964), so pond water dominated
by snowmelt or cold rain may have had more negative δ^18^O and δD values
than contemporaneous water at the system inlet. A second possibility is
that the ponds contained ground water with more negative δ^18^O and δD
values than contemporaneous water at the system inlet. This explanation
is speculative because no information is available about ground-water
flow patterns around the NSCS.

[Deep pond outlet to system outlet]{.underline} - Average concentrations
of most constituents did not change appreciably in the second grass
strip. An exception is the decrease of dissolved P contents (fig. 3a),
which may be due to precipitation of hydroxyapatite.

Overall decreases of silica concentrations in the NSCS may reflect
quartz precipitation whereas increases of manganese concentrations may
reflect mangerite dissolution. Patterns of variation in iron
concentrations may reflect the competing effects of iron hydroxide
precipitation and siderite dissolution.

**Conclusions and recommendations for future monitoring**

Chemical variations in water flowing through the NSCS paint a mixed
picture of this BMP's ability to treat cattle-pasture runoff. Whereas
treatment in the NSCS reduces average concentrations of nitrate, ammonia
plus organic N, suspended P, and fecal coliform bacteria, treatment
actually increases average concentrations of ammonium, dissolved organic
N and dissolved P. The results also call into question the role of the
deep pond because it was the site of significant increases in the
concentrations of ammonium, suspended organic plus ammonia N and
dissolved P.

Many questions remain unanswered about chemical and treatment processes
in the NSCS. These questions must be addressed before a final judgment
is made about the NSCS's treatment capabilities or possible structural
modifications of the system. Among these questions are the following:

-   What are the chemical loads at the system inlet and outlet, and how
    does the NSCS affect loads? This question can be answered by
    continuous, automated monitoring of flow volumes and water chemistry
    at the system inlet and outlet during runoff events. In view of the
    questions raised about the function of the deep pond, it would be
    useful to monitor flow volumes and water chemistry at the pond
    connection and deep pond outlet as well.

-   What is the effect of treated water exiting the NSCS on the
    chemistry of the receiving stream? The answer to this question would
    emerge from discharge and chemical measurements of stream water up-
    and downstream of the confluence of the stream and NSCS outlet.

-   How does water in the NSCS interact with surrounding ground water?
    This issue can be examined by installing four ground-water well
    nests in and next to the NSCS. The nests could be located in the
    first grass buffer strip, next to the shallow and deep ponds, and in
    the second grass buffer strip. Each nest would include a water-table
    well and a well screened about 1.5 meters (4.9 ft.) below the water
    table. Periodicr measurement of water levels and chemistry in the
    wells would show how infiltration from the grass strips affects
    ground-water chemistry and whether pond water flows into ground
    water or *vice versa*. Measurements of δ^18^O and δD values of
    surface and ground water would be very informative in this effort.

-   Are increases of certain nutrient concentrations in the deep pond
    due to resuspension of sediments from the pond bottom? This question
    can be investigated by sampling sediments from the deep-pond bottom
    with a coring device. Sediment thicknesses, compaction and
    compositions would be measured to determine whether the sediments
    represent a source of stored nutrients that become incorporated in
    runoff by turbulence.

-   What are the roles of ammonification, nitrification and
    denitrification in the NSCS? The effects of these reactions, if they
    occur, can be better defined by field measurements of redox species
    such as dissolved oxygen, ferrous iron, and ammonium, and by
    measurements of δ^15^N values of nitrate, ammonium and N~2~ gas. A
    related question is how the performance of the NSCS may be improved
    by diminishing ammonium export from the ponds, particularly the deep
    pond. One possibility would be to promote nitrification (Reaction 3)
    in the ponds by introducing more dissolved oxygen. Aeration might be
    accomplished by mechanical stirring of the ponds, by installing a
    pump to circulate and oxygenate bottom water, or by planting
    cattails or reeds to introduce oxygen to the pond bottoms.

**References**

Bingham, S.C., Westerman, P.W., and Overcash, M.R., 1980, Effects of
grass buffer zone length in reducing the pollution from land application
areas: Transactions of the American Society of Agricultural Engineers,
v. 20, p. 330-342.

Chaubey, I., Edwards, D.R., Daniel, T.C., Moore, P.C., and Nichols,
D.J., 1994, Effectiveness of vegetative filer strips in retaining
surface-applied swine manure constituents: Transactions of the American
Association of Agricultural Engineers, v. 37, no. 3, p. 845-850.

Chow, T.E., Maidment, D.R., and Mays, L.W., 1988, Applied hydrology:
McGraw-Hill, New York, 572 p.

Clausen, J.C., and Meals, D.W., 1989, Water quality achievable with best
management practices: Journal of Soil and Water Conservation, v. 44, p.
593-596.

Cline, J.D., and Kaplan, I.R., 1975, Isotopic fractionation of dissolved
nitrate during denitrification in the eatern tropical North Pacific
Ocean: Marine Chemistry, v. 3, p. 271-299.

Coplen, T.B., Wildman, J.D., and Chen, J., 1991, Improvements in the
gaseous hydrogen-water equilibration technique for hydrogen isotope
ratio analysis: Analytical Chemistry, v. 63, p. 910-912.

Craig, H., 1961, Isotopic variations in meteoric waters: Science, v.
133, p. 1702-1703.

Dansgaard, W., Stable isotopes in precipitation: Tellus, v. 16, p.
436-468.

Dickey, E.C., and Vanderholm, D.H., 1981, Vegetative filter treatment of
livestock feedlot runoff: Journal of Environmental Quality, v. 10, p.
279-284.

Dillaha, T.A., Sherrard, J.H., Lee, D., Mostaghimi, S., and Shaholtz,
V.O., 1988, Evaluation of vegetative filter strips as a best management
practice for feed lots: Journal of the Water Pollution Control
Federation, v. 60, p. 1231-1238.

Edwards, W.M., Owens, L.B., and White, R.K., 1983, Managing runoff from
a small, paved beef feedlot: Journal of Environmental Quality, v. 12,
no. 2, p. 281-286.

Edwards, W.M., Owens, L.B., White, R.K., and Fausey, N.R., 1986,
Managing feedlot runoff from a settling basin plus tiled infiltration
bed: Transactions of the American Society of Agricultural Engineers, v.
29, no. 1, p. 243-247.

Epstein, S., and Mayeda, T.K., 1953, Variation of O18 content of water
from natural sources: Geochimica Cosmochimica Acta, v. 4, p. 213-224.

Fishman, M.J., and Friedman, L.C., 1989, Methods for determination of
inorganic substances in water and fluvial sediments, Techniques of
Water-Resources Investigations of the U.S. Geological Survey, p. 545.

Gat, J.R., and Gonfiantini, R., eds., 1981, Stable isotope hydrology:
Technical Reports Series: Vienna, International Atomic Energy Agency, v.
210, 337 p.

Gschlöβl, T., Steinmann, C., Schleypen, P., and Melzer, A., 1998,
Constructed wetlands for effluent polishing of lagoons: Water Research,
v. 32, p. 2639-2645.

Heaton, T.H.E., 1986, Isotopic studies of nitrogen pollution in the
hydrosphere and atmosphere: a review: Chemical Geology, v. 59, p.
87-102.

Higgins, M.J., Rock, C.A., and Bouchard, R.W., B., 1993, Controlling
agricultural runoff by use of constructed wetlands, *in* Moshiri, G.A.,
ed., Constructed wetlands for water quality improvements: Chelsea,
Lewis, p. 359-367.

Hornlein, J.F., Szabo, C.O., Zajd, H.J.J., and Mulks, R.L., 1997, Water
resources data, New York, water year 1997: U.S. Geological Survey 97-3.

Ketchum, L.H., Cunningham, A.J., and Irvine, R.L., 1981, Overland flow
treatment of poultry processing wastewater in cold climates: U.S.
Environmental Protection Agency EPA-600/2-81-093.

Macko, S.A., and Ostrom, N.E., 1994, Pollution studies using stable
isotopes, *in* Lajtha, K., and Michener, R.H., eds., Stable isotopes in
ecology and environmental science: Oxford, Blackwell Scientific, p.
45-62.

Magette, W.L., Brinsfield, R.B., Palmer, R.E., and Wood, J.D., 1989,
Nutrient and sediment removal by vegetative filter strips: Transactions
of the American Society of Agricultural Engineers, v. 32, p. 663-667.

Martel, C.J., Jenkins, T.F., and Palazzo, A.J., 1980, Wastewater
treatment in cold regions by overland flow.: U.S. Army Cold Regions
Research and Engineering Laboratory CRREL Report 80-7.

New York State Department of Environmental Conservation, 1994, Water
qualty regulations. Surface water and groundwater classifications and
standards.: New York State Department of Environmental Conservation
Title 6, Chapter X, Parts 700-705.

New York State Department of Environmental Conservation, 1996a, The 1996
priority waterbodies list for the Susquehanna River basin: Albany, New
York Sate Department of Environemtal Conservation, Division of Water,
117 p.

New York State Department of Environmental Conservation, 1996b, The 1996
priority waterbodies list for the Oswego-Seneca-Oneida River Basin:
Albany, New York Sate Department of Environemtal Conservation, Division
of Water, 196 p.

Parkhurst, D.L., 1995, User\'s guide to PHREEQC-a computer program for
speciation, reaction-path, advective-transport, and inverse geochemical
calculations.: U.S. Geological Survey 95-4227.

Phillips, J.D., 1989, An evaluation of the factors determining the
effectiveness of water quality buffer zones.: Journal of Hydrology, v.
107, p. 133-145.

Robinson, C.A., Ghaffarzadeh, M., and Cruse, R.M., 1996, Vegetative
filter strip effects on sediment concentration in cropland runoff:
Journal of Soil and Water Conservation, v. 50, p. 227-230.

Schellinger, G.R., and Clausen, J.C., 1992, Vegetative filter treatment
of dairy barnyard runoff in cold regions: Journal of Environmental
Quality, v. 21, p. 40-45.

Smith, C.M., 1989, Riparian pasture retirement effects on sediment,
phosphorous, and nitrogen in channellized surface run-off from pastures:
New Zealand Journal of Marine and Freshwater Research, v. 23, p.
139-146.

Stumm, W., and Morgan, J.J., 1981, Aquatic Chemistry: New York, Wiley,
780 p.

Srivastava, P., Edwards, D.R., Daniel, D.R., Moore, P.A. Jr., and
Costello, T.A., 1996, Performance of vegetative filter strips with
varying pollutant sources and filter strip lengths: Transactions of the
American Society of Agricultural Engineers, v. 36, 2231-2239.

United States Department of Agriculture, 1971, Soil Survey of Cayuga
County, New York, USDA Soil Conservation Service, 205 p.

Wengrzynek, R. J., 1995, Nutrient and sediment control system: Natural
Resources Conservation Service, Chester, Pennsylvania, Environmental
Quality Technical Note N4, 19 pp.

Young, R.A., Huntrods, T., and Anderson, W., 1980, Effectiveness of
vegetated buffer strips in controlling pollution from feedlot runoff:
Journal of Environmental Quality, v. 3, p. 483-487.

**Table 1 - Water chemistry in nutrient and sediment control system
\[Station numbers correspond to those shown in fig. 1.\
dis., dissolved; susp., suspended; tot., total; ortho., orthophosphate;
\--, not analyzed. In the δ^15^N column, ^N^ indicates an isotopic\
analysis of nitrate and ^A^ an analysis of ammonium. Values of pε
calculated from concentrations of coexisting ammonium and nitrate\
with PHREEQC (Parkhurst, 1995).\]**

  ------------------------------ -------- -- -------- -- --------- -- -- --------------- -- --- ---------- -- -- ------------ -- --- ----------- -- --- -------------- -- ---- ----------- -- --- ----------- -- --- ---------- -- -- ---------- ----------
  **Station**                    **pH**      **T\        **SC\           **Alkalinity,          **Total\         **N,\               **N,\              **N,\                  **N,\              **N,\              **P,\            **P,\      **P,\
                                             (°C)**      (μS/cm\         as CaCO~3~             solids\          Ammonium,\          Organic,\          Ammon.+Org,\           Nitrite,\          Nitrate,\          dis.\            ortho.,\   susp.\
                                                         @ 25°C)**       (mg/L)**               (mg/L)**         (mg/L)**            dis.               susp. (mg/L)**         dis.               dis.               (mg/L)**         dis.       (mg/L)**
                                                                                                                                     (mg/L)**                                  (mg/L)**           (mg/L)**                            (mg/L)**   

  **[(1/6/98) -                                                                                                                                                                                                                                  
  snowmelt]{.underline}**                                                                                                                                                                                                                        

  1 - system inlet               7.6         10.5        1046            304                    610              7.8                 6.0                31.9                   0.7                12.2               4.0              1.8        8.0

  2 - shallow pond inlet         7.7         9.3         870             270                    556              7.0                 9.8                11.7                   0.8                3.0                2.7              1.8        3.2

  3 - pond connection            8.6         7.7         205             58                     89               1.0                 1.1                1.4                    0.0                0.3                0.3              0.2        0.3

  4 - deep pond outlet           8.3         1.3         733             238                    436              3.4                 4.5                2.7                    0.1                0.7                1.2              0.9        0.6

  5 - system outlet              7.9         4.4         693             220                    423              2.5                 3.8                3.1                    0.1                0.6                1.0              0.8        0.8

                                                                                                                                                                                                                                                 

  **[2/18/98 -                                                                                                                                                                                                                                   
  rain/snowmelt]{.underline}**                                                                                                                                                                                                                   

  1 - system inlet               7.9         1.9         836             258                    548              10.5                4.7                14.6                   0.2                4.8                3.7              3.4        4.5

  2 - shallow pond inlet         7.8         1.5         557             154                    349              8.3                 4.2                11.1                   0.2                0.3                4.4              4.0        2.8

  3 - pond connection            7.5         1.6         733             194                    511              16.5                7.5                19.3                   0.2                0.8                6.6              5.9        3.9

  4 - deep pond outlet           7.1         1.2         1290            428                    968              50.2                9.8                22.5                   0.0                0.3                13.8             12.0       2.6

  5 - system outlet              7.2         1.4         1230            420                    946              47.6                12.4               19.6                   0.0                0.3                12.3             11.2       2.6

  Trip blank                     7.4         \--         6               4                      \--              0.0                 0.1                0.0                    0.0                0.0                0.0              0.0        0.0

                                                                                                                                                                                                                                                 

  **[5/12/98 -                                                                                                                                                                                                                                   
  rain]{.underline}**                                                                                                                                                                                                                            

  1 - system inlet               8.1         13.0        1606            480                    1100             5.7                 8.2                23.2                   0.3                2.0                2.9              2.1        7.3

  2 - shallow pond inlet         7.5         14.0        1132            372                    760              7.4                 24.2               0.0                    0.0                0.1                7.0              1.8        0.0

  3 - pond connection            7.7         14.3        1214            340                    809              25.0                20.8               0.6                    0.0                0.1                7.6              5.9        3.9

  4 - deep pond outlet           7.8         16.0        1146            384                    809              23.6                9.7                11.8                   0.0                0.1                7.5              6.6        3.6

  5 - system outlet              7.8         18.7        1131            360                    736              24.1                0.5                10.4                   0.0                0.1                4.2              3.0        4.4
  ------------------------------ -------- -- -------- -- --------- -- -- --------------- -- --- ---------- -- -- ------------ -- --- ----------- -- --- -------------- -- ---- ----------- -- --- ----------- -- --- ---------- -- -- ---------- ----------

<table style="width:100%;">
<colgroup>
<col style="width: 15%" />
<col style="width: 5%" />
<col style="width: 5%" />
<col style="width: 1%" />
<col style="width: 4%" />
<col style="width: 0%" />
<col style="width: 4%" />
<col style="width: 0%" />
<col style="width: 4%" />
<col style="width: 0%" />
<col style="width: 4%" />
<col style="width: 0%" />
<col style="width: 4%" />
<col style="width: 0%" />
<col style="width: 4%" />
<col style="width: 0%" />
<col style="width: 4%" />
<col style="width: 0%" />
<col style="width: 3%" />
<col style="width: 2%" />
<col style="width: 2%" />
<col style="width: 3%" />
<col style="width: 0%" />
<col style="width: 3%" />
<col style="width: 4%" />
<col style="width: 4%" />
<col style="width: 0%" />
<col style="width: 3%" />
<col style="width: 3%" />
<col style="width: 0%" />
</colgroup>
<tbody>
<tr class="odd">
<td><strong>Station</strong></td>
<td><strong>Ca<br />
(mg/L)</strong></td>
<td><strong>Mg<br />
(mg/L)</strong></td>
<td colspan="2"><strong>Na<br />
(mg/L)</strong></td>
<td colspan="2"><strong>K<br />
(mg/L)</strong></td>
<td colspan="2"><strong>Cl<br />
(mg/L)</strong></td>
<td colspan="2"><strong>SO<sub>4</sub><br />
(mg/L)</strong></td>
<td colspan="2"><strong>SiO<sub>2</sub><br />
(mg/L)</strong></td>
<td colspan="2"><strong>Fe<br />
(μg/L)</strong></td>
<td colspan="2"><strong>Mn<br />
(μg/L)</strong></td>
<td colspan="2"><strong>δ<sup>18</sup>O<br />
(‰)</strong></td>
<td colspan="2"><strong>δD<br />
(‰)</strong></td>
<td colspan="2"><strong>δ<sup>15</sup>N<br />
(‰)</strong></td>
<td colspan="4"><strong>Fecal coliform<br />
(colonies/100 ml)</strong></td>
<td colspan="2"><p><strong>pε</strong></p>
<p><strong>(Ν<sup>−3</sup>/Ν<sup>+5</sup>)</strong></p></td>
<td></td>
</tr>
<tr class="even">
<td><strong><u>1/6/98 - snowmelt</u></strong></td>
<td></td>
<td></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="4"></td>
<td colspan="2"></td>
<td></td>
</tr>
<tr class="odd">
<td>1 - system inlet</td>
<td>81.8</td>
<td>25.0</td>
<td colspan="2">23.8</td>
<td colspan="2">59.2</td>
<td colspan="2">56.9</td>
<td colspan="2">26.0</td>
<td colspan="2">8.0</td>
<td colspan="2">183</td>
<td colspan="2">137</td>
<td colspan="2">--</td>
<td colspan="2">--</td>
<td colspan="2">11.4<sup>N</sup></td>
<td colspan="4">--</td>
<td colspan="2">6.3</td>
<td></td>
</tr>
<tr class="even">
<td>2 - shallow pond inlet</td>
<td>74.7</td>
<td>21.0</td>
<td colspan="2">28.7</td>
<td colspan="2">54.4</td>
<td colspan="2">70.9</td>
<td colspan="2">24.5</td>
<td colspan="2">7.6</td>
<td colspan="2">424</td>
<td colspan="2">292</td>
<td colspan="2">--</td>
<td colspan="2">--</td>
<td colspan="2">17.8<sup>N</sup></td>
<td colspan="4">--</td>
<td colspan="2">6.2</td>
<td></td>
</tr>
<tr class="odd">
<td>3 - pond connection</td>
<td>16.8</td>
<td>4.5</td>
<td colspan="2">4.3</td>
<td colspan="2">7.9</td>
<td colspan="2">11.3</td>
<td colspan="2">4.2</td>
<td colspan="2">0.6</td>
<td colspan="2">79</td>
<td colspan="2">63</td>
<td colspan="2">--</td>
<td colspan="2">--</td>
<td colspan="2">13.1<sup>N</sup></td>
<td colspan="4">--</td>
<td colspan="2">5.0</td>
<td></td>
</tr>
<tr class="even">
<td>4 - deep pond outlet</td>
<td>51.7</td>
<td>26.5</td>
<td colspan="2">22.2</td>
<td colspan="2">41.4</td>
<td colspan="2">61.2</td>
<td colspan="2">20.0</td>
<td colspan="2">2.2</td>
<td colspan="2">239</td>
<td colspan="2">354</td>
<td colspan="2">--</td>
<td colspan="2">--</td>
<td colspan="2">11.9<sup>N</sup></td>
<td colspan="4">--</td>
<td colspan="2">5.9</td>
<td></td>
</tr>
<tr class="odd">
<td>5 - system outlet</td>
<td>56.4</td>
<td>25.1</td>
<td colspan="2">20.1</td>
<td colspan="2">36.5</td>
<td colspan="2">53.8</td>
<td colspan="2">21.9</td>
<td colspan="2">3.5</td>
<td colspan="2">265</td>
<td colspan="2">101</td>
<td colspan="2">--</td>
<td colspan="2">--</td>
<td colspan="2">11.3<sup>N</sup></td>
<td colspan="4">--</td>
<td colspan="2">6.2</td>
<td></td>
</tr>
<tr class="even">
<td></td>
<td></td>
<td></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="4"></td>
<td colspan="2"></td>
<td></td>
</tr>
<tr class="odd">
<td colspan="4"><strong><u>2/18/98 - rain/snowmelt</u></strong></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td></td>
<td></td>
<td colspan="2"></td>
<td colspan="2"></td>
</tr>
<tr class="even">
<td>1 - system inlet</td>
<td>73.2</td>
<td>22.8</td>
<td colspan="2">22.0</td>
<td colspan="2">62.9</td>
<td colspan="2">43.9</td>
<td colspan="2">19.5</td>
<td colspan="2">7.4</td>
<td colspan="2">162</td>
<td colspan="2">575</td>
<td colspan="2">--</td>
<td colspan="2">--</td>
<td colspan="2">3.9<sup>N</sup></td>
<td colspan="4">--</td>
<td colspan="2">6.4</td>
<td></td>
</tr>
<tr class="odd">
<td>2 - shallow pond inlet</td>
<td>45.6</td>
<td>13.1</td>
<td colspan="2">14.0</td>
<td colspan="2">41.4</td>
<td colspan="2">27.2</td>
<td colspan="2">10.2</td>
<td colspan="2">6.1</td>
<td colspan="2">149</td>
<td colspan="2">198</td>
<td colspan="2">-9.6</td>
<td colspan="2">-64.9</td>
<td colspan="2">16.6<sup>N</sup></td>
<td colspan="4">--</td>
<td colspan="2">6.4</td>
<td></td>
</tr>
<tr class="even">
<td>3 - pond connection</td>
<td>53.5</td>
<td>17.2</td>
<td colspan="2">23.6</td>
<td colspan="2">50.6</td>
<td colspan="2">45.0</td>
<td colspan="2">12.3</td>
<td colspan="2">5.3</td>
<td colspan="2">338</td>
<td colspan="2">475</td>
<td colspan="2">--</td>
<td colspan="2">--</td>
<td colspan="2">13.4<sup>A</sup></td>
<td colspan="4">--</td>
<td colspan="2">6.8</td>
<td></td>
</tr>
<tr class="odd">
<td>4 - deep pond outlet</td>
<td>92.1</td>
<td>30.1</td>
<td colspan="2">35.2</td>
<td colspan="2">73.9</td>
<td colspan="2">75.9</td>
<td colspan="2">20.2</td>
<td colspan="2">6.7</td>
<td colspan="2">1200</td>
<td colspan="2">1225</td>
<td colspan="2">-10.9</td>
<td colspan="2">-73.4</td>
<td colspan="2">16.2<sup>A</sup></td>
<td colspan="4">--</td>
<td colspan="2">7.2</td>
<td></td>
</tr>
<tr class="even">
<td>5 - system outlet</td>
<td>87.6</td>
<td>28.4</td>
<td colspan="2">33.6</td>
<td colspan="2">69.8</td>
<td colspan="2">73.5</td>
<td colspan="2">19.1</td>
<td colspan="2">6.5</td>
<td colspan="2">803</td>
<td colspan="2">1347</td>
<td colspan="2">-10.9</td>
<td colspan="2">-72.7</td>
<td colspan="2">9.5<sup>A</sup></td>
<td colspan="4">--</td>
<td colspan="2">7.1</td>
<td></td>
</tr>
<tr class="odd">
<td>Trip blank</td>
<td>0.1</td>
<td>0.0</td>
<td colspan="2">0.1</td>
<td colspan="2">0.1</td>
<td colspan="2">0.1</td>
<td colspan="2">0.1</td>
<td colspan="2">0.1</td>
<td colspan="2">10</td>
<td colspan="2">4</td>
<td colspan="2">--</td>
<td colspan="2">--</td>
<td colspan="2">--</td>
<td colspan="4">--</td>
<td colspan="2"></td>
<td></td>
</tr>
<tr class="even">
<td></td>
<td></td>
<td></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="4"></td>
<td colspan="2"></td>
<td></td>
</tr>
<tr class="odd">
<td><strong><u>5/12/98 – rain</u></strong></td>
<td></td>
<td></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="4"></td>
<td colspan="2"></td>
<td></td>
</tr>
<tr class="even">
<td>1 - system inlet</td>
<td>135.1</td>
<td>44.9</td>
<td colspan="2">55.6</td>
<td colspan="2">120.0</td>
<td colspan="2">137.5</td>
<td colspan="2">54.9</td>
<td colspan="2">14.0</td>
<td colspan="2">675</td>
<td colspan="2">1007</td>
<td colspan="2">-9.0</td>
<td colspan="2">-63.0</td>
<td colspan="2">23.8<sup>N</sup></td>
<td colspan="4">2025000</td>
<td colspan="2">5.4</td>
<td></td>
</tr>
<tr class="odd">
<td>2 - shallow pond inlet</td>
<td>94.5</td>
<td>34.0</td>
<td colspan="2">38.9</td>
<td colspan="2">60.5</td>
<td colspan="2">90.4</td>
<td colspan="2">17.3</td>
<td colspan="2">10.3</td>
<td colspan="2">1030</td>
<td colspan="2">1287</td>
<td colspan="2">-7.3</td>
<td colspan="2">-55.3</td>
<td colspan="2">15.3<sup>A</sup></td>
<td colspan="4">1000000</td>
<td colspan="2">5.9</td>
<td></td>
</tr>
<tr class="even">
<td>3 - pond connection</td>
<td>97.9</td>
<td>33.3</td>
<td colspan="2">32.9</td>
<td colspan="2">65.0</td>
<td colspan="2">74.7</td>
<td colspan="2">6.9</td>
<td colspan="2">9.0</td>
<td colspan="2">384</td>
<td colspan="2">1305</td>
<td colspan="2">-9.6</td>
<td colspan="2">-71.1</td>
<td colspan="2">18.7<sup>A</sup></td>
<td colspan="4">5700</td>
<td colspan="2">5.6</td>
<td></td>
</tr>
<tr class="odd">
<td>4 - deep pond outlet</td>
<td>97.8</td>
<td>31.7</td>
<td colspan="2">31.2</td>
<td colspan="2">68.8</td>
<td colspan="2">73.5</td>
<td colspan="2">5.8</td>
<td colspan="2">8.6</td>
<td colspan="2">308</td>
<td colspan="2">1214</td>
<td colspan="2">-9.6</td>
<td colspan="2">-70.2</td>
<td colspan="2">20.8<sup>A</sup></td>
<td colspan="4">3150</td>
<td colspan="2">5.4</td>
<td></td>
</tr>
<tr class="even">
<td>5 - system outlet</td>
<td>98.3</td>
<td>31.0</td>
<td colspan="2">30.5</td>
<td colspan="2">64.2</td>
<td colspan="2">67.5</td>
<td colspan="2">4.0</td>
<td colspan="2">8.3</td>
<td colspan="2">508</td>
<td colspan="2">1287</td>
<td colspan="2">-9.3</td>
<td colspan="2">-69.8</td>
<td colspan="2">18.6<sup>A</sup></td>
<td colspan="4">4300</td>
<td colspan="2">5.2</td>
<td></td>
</tr>
</tbody>
</table>

**Table 2a - Treatment values in NSCS. \[Values of 100 represent
complete treatment and of 0 represent no treatment. Negative values
represent\
concentration increases. Percentages formed from (100\*(concentration at
system inlet - concentrations at outlet)/concentration at system
inlet).\]**

  ------------- ---------------- ---------- ------------ ----------- ---------------- ----------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------------
  **Date**      **Alkalinity,\   **Total\   **N,\        **N,\       **N,\            **N,\       **P,\      **P,\      **\        **\        **\        **\        **\        **\        **\
                as CaCO~3~\      solids\    Ammonium,\   Organic,\   Ammonia+Org.,\   Nitrate,\   dis.\      susp.\     Ca\        Mg\        Na\        K\         Cl\        SO~4~\     Fecal coliform\
                (mg/L)**         (mg/L)**   (mg/L)**     dis.        susp. (mg/L)**   dis.        (mg/L)**   (mg/L)**   (mg/L)**   (mg/L)**   (mg/L)**   (mg/L)**   (mg/L)**   (mg/L)**   (colonies/100
                                                         (mg/L)**                     (mg/L)**                                                                                            ml)**

  **1/6/98**    28               31         68           37          90               95          75         91         31         0          16         38         5          16         

  **2/18/98**   -63              -73        -355         -164        -35              94          -232       42         -20        -25        -53        -11        -68        2          

  **5/12/98**   25               33         -323         94          55               95          -43        40         27         31         45         47         51         93         100

  Average       -3               -3         -203         -11         37               95          -67        57         13         2          3          25         -4         37         \--
  ------------- ---------------- ---------- ------------ ----------- ---------------- ----------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------------

**Table 2b - Average concentration change in each NSCS component as
percentage of total\
concentration change in NSCS.** \[Negative values denote concentration
decreases , positive\
values denote concentration increase.\]

+------------------------+-------+----------+-----+-----+-----+-----+
| **\                    | **\   | **N,     | **N | **\ | **\ | **\ |
| \                      | N,    | Ammoni   | ,** | \   | \   | Fe  |
| Component**            | Ammon | a+Org.,\ |     | P,  | P,  | cal |
|                        | ium** | susp.**  | **  | dis | s   | c   |
|                        |       |          | Nit | .** | usp | oli |
|                        |       |          | rat |     | .** | for |
|                        |       |          | e,\ |     |     | m** |
|                        |       |          | dis |     |     |     |
|                        |       |          | .** |     |     |     |
+------------------------+-------+----------+-----+-----+-----+-----+
| **Net increase or      | inc   | decrease | de  | in  | de  | de  |
| decrease in NSCS?**    | rease |          | cre | cre | cre | cre |
|                        |       |          | ase | ase | ase | ase |
+------------------------+-------+----------+-----+-----+-----+-----+
| **First grass strip**  | -2    | -128     | -86 | 51  | -   | -51 |
|                        |       |          |     |     | 115 |     |
+------------------------+-------+----------+-----+-----+-----+-----+
| **Shallow pond**       | 39    | -4       | -12 | 6   | 18  | -49 |
+------------------------+-------+----------+-----+-----+-----+-----+
| **Deep pond**          | 69    | 43       | -1  | 117 | -11 | 0   |
+------------------------+-------+----------+-----+-----+-----+-----+
| **Second grass strip** | -6    | -11      | -1  | -74 | 8   | 0   |
+------------------------+-------+----------+-----+-----+-----+-----+
| **Sum**                | 100%  | -100%    | -1  | 1   | -1  | -1  |
|                        |       |          | 00% | 00% | 00% | 00% |
+------------------------+-------+----------+-----+-----+-----+-----+

**Figure Captions**

1\. Site location, main components of the NSCS, and sampling locations.

2\. Concentration variations of nitrogen species at the five sampling
locations in the NSCS. The bold black lines show average concentrations
computed from the three measured concentrations at each sampling
location.

3\. Concentrations of phosphorous species, total solids, and fecal
coliform bacteria at the five sampling locations. The bold black lines
show average concentrations computed from the three measured
concentrations at each sampling location.

4\. Piper diagram showing major element proportions in water from the
NSCS. Solid symbols (square, circle, triangle) indicate ionic
proportions. Dashed lines indicate average ionic proportions. Circles
centered on solid symbols indicate dissolved solids concentrations; the
diameters of the circles are scaled in milligrams per liter as shown in
the center right of the figure. Water in the NSCS is classified as a
calcium bicarbonate type.

5\. Saturation indices of selected minerals. The SI values shown are
averages from the three samplings at each sampling location.

6\. Values of δ^18^O and δD from the later two samplings in the NSCS.
The change in composition from the system inlet to the shallow pond on
May 12 is attributed to evaporation. The decreases of isotopic values
from the system inlet to the shallow and deep ponds are labeled.

7\. Histogram of δ^15^N~nitrate~ and δ^15^N~ammonium~ values in the
NSCS. Numbers indicate sampling location and letters sampling date.