U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2009–1123

Total Selenium and Selenium Species in Irrigation Drain 

Inflows to the Salton Sea, California, October 2008 and 

January 2009

Total Selenium and Selenium Species in 

Irrigation Drain Inflows to the Salton Sea, 

California, October 2008 and January 2009

By Thomas W. May, Michael J. Walther, Michael K. Saiki, and William G. 

Brumbaugh

Open-File Report 2009–1123

U.S. Department of the Interior

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

KEN SALAZAR, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2009

For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, 

natural hazards, and the environment, visit http://www.usgs.gov or call 1-888-ASK-USGS

For an overview of USGS information products, including maps, imagery, and publications, 

visit http://www.usgs.gov/pubprod

To order this and other USGS information products, visit http://store.usgs.gov

Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the 

U.S. Government.

Although this report is in the public domain, permission must be secured from the individual copyright owners to 

reproduce any copyrighted materials contained within this report.

Suggested citation:

May, T.W., Walther, M.J., Saiki, M.K., and Brumbaugh, W.G., 2009, Total selenium and selenium species in irrigation 

drain inflows to the Salton Sea, California, October 2008 and January 2009: U.S. Geological Survey Open-File 

Report 2009–1123, 14 p. 
iii

Contents

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

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

Methods...........................................................................................................................................................1

Field Collection and Preservation ......................................................................................................1

Sampling History...................................................................................................................................2

Homogenization and Lyophilization ...................................................................................................2

Chemical Procedures...........................................................................................................................2

Instrumental Analysis...........................................................................................................................3

Quality Assurance..........................................................................................................................................2

Results .............................................................................................................................................................2

Quality Control Results................................................................................................................................13

References Cited..........................................................................................................................................14

Tables

1. Total selenium concentrations in duplicates of unfiltered irrigation drain water 

samples, Salton Sea, California, October 2008 ........................................................................5

2. Total selenium concentrations in duplicates of unfiltered irrigation drain water 

samples, Salton Sea, California, January 2009........................................................................6

3. Total dissolved selenium, dissolved selenium species, and particulate selenium 

concentrations in filtered irrigation drain water samples, Salton Sea, California, 

October 2008..................................................................................................................................7

4. Total suspended solids concentrations in unfiltered Salton Sea, California, irrigation 

drain water samples, October 2008 and January 2009...........................................................8

5. Selenium concentrations in biota samples collected from Salton Sea, California, 

irrigation drains, October 2008 ...................................................................................................9

6. Selenium concentrations in detritus and sediment samples collected from Salton Sea, 

California, irrigation drains, October 2008 .............................................................................12

7. Particle size distributions in sediment samples collected from Salton Sea, California, 

irrigation drains, October 2008 .................................................................................................13

8. Percent total organic carbon in sediment samples collected from Salton Sea, 

California, irrigation drains, October 2008 ..............................................................................13
iv

Conversion Factors

Multiply By To obtain

Length

millimeter (mm) 0.03937 inch (in.)

micrometer 0.0000393 inch (in.)

Volume

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

milliliter (mL) .034 ounce, fluid (fl. oz)

Mass

gram (g) 0.03527 ounce, avoirdupois (oz)

milligram (mg) .000035 ounce (oz)

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

°F=(1.8×°C)+32

Concentrations of chemical constituents in water are given either in milligrams per liter (mg/L) 

or micrograms per liter (μg/L). 

Concentrations of chemical constituents in solid materials are given in micrograms per gram 

(μg/g) dry weights.
Abstract

This report presents the results for two sampling periods 

(October 2008 and January 2009) during a 4-year monitoring 

program to characterize selenium concentrations in selected 

irrigation drains flowing into the Salton Sea, California. Total 

selenium, selenium species (dissolved selenite, selenate, 

organoselenium), and total suspended solids were determined 

in water samples. Total selenium also was determined in water 

column particulates and in sediment, detritus, and biota that 

included algae, plankton, midge larvae (family, Chironomidae), and two fish species (western mosquitofish, Gambusia

affinis, and sailfin molly, Poecilia latipinna). In addition, 

sediments were analyzed for percent total organic carbon and 

particle size. Mean total selenium concentrations in water for 

both sampling periods ranged from 1.00 to 33.6 micrograms 

per liter, predominately as selenate, which is typical of waters 

where selenium is leached out of selenium-containing marine 

shales and associated soils under alkaline and oxidizing conditions. Total selenium concentrations (micrograms per gram 

dry weight) ranged as follows: algae, 1.52 to 8.26; plankton, 

0.79 to 3.66; midges, 2.68 to 50.6; fish, 3.09 to 30.4; detritus, 

1.78 to 58.0; and sediment, 0.42 to 10.0.

Introduction

Monitoring surveys are being conducted by the U.S. 

Geological Survey (USGS) for 4 years to provide a profile of 

selenium concentrations in selected irrigation drain inflows to 

the Salton Sea, California. To accomplish this goal, total selenium, selenium species (dissolved selenite, selenate, organoselenium), and total suspended solids were determined in water 

samples. Total selenium was measured in water column 

particulates and in sediment, detritus, and biota that included 

algae, plankton, midge larvae (family, Chironomidae), and 

two fish species (western mosquitofish, Gambusia affinis, and 

sailfin molly, Poecilia latipinna). In addition, sediments were 

analyzed for percent total organic carbon and particle size. 

The results in this report were derived from samples collected 

during October 2008 and January 2009.

Methods

Field Collection and Preservation

The USGS sampling team used the laboratory at the U.S. 

Fish and Wildlife Service Sonny Bono Salton Sea National 

Wildlife Refuge (henceforth referred to as “the Refuge”) for 

certain aspects of sample processing and for preparing samples 

for shipment during field trips to irrigation drains. 

Unfiltered Water: Each water sample to be analyzed 

for total selenium was poured through a 1-millimeter (mm) 

polypropylene sieve attached to a 1-liter (L) precleaned borosilicate glass bottle. Upon collection, the water sample was 

acidified to less than pH 2 with 6 normal (N) hydrochloric acid 

(HCl), chilled to approximately four degrees Celsius (~4 oC), 

and kept in the dark during transport to the USGS. Each water 

sample intended for analysis of total suspended solids (TSS) 

was poured through a 1-mm polypropylene sieve attached to 

a precleaned widemouth 1-L polypropylene bottle. The TSS 

samples were chilled (~4 0C) during transport to the USGS.

Filtered Water: Water for selenium speciation was filtered 

using a Geotech® peristaltic pump equipped with a standard 

pumphead and high-capacity 0.45 micrometer (μm) filter 

capsule certified for trace-element background. All tubing 

was acid-cleaned silicone and a new length was used at each 

site and for the blank. At each site, 1 L of deionized (DI) 

water was filtered through the filter capsule followed by site 

water. The first 200 milliliters (mL) of site water eluant were 

discarded, then 1 L of eluant was collected in an acid-cleaned 

1-L borosilicate glass bottle, acidified, and stored as described 

earlier for unfiltered water.

Particulates: A polycarbonate Geotech® 142-mm plate filter apparatus was used with a 142-mm 0.4-μm polycarbonate 

filter. At each site, 0.5 L of DI water was filtered through the 

plate filter, followed by up to 1 L of site water; after volume 

notation, the filtrate was discarded. Each filter was placed in 

Total Selenium and Selenium Species in Irrigation Drain 

Inflows to the Salton Sea, California, October 2008 and 

January 2009

By Thomas W. May, Michael J. Walther, Michael K. Saiki, and William G. Brumbaugh
2 Total Selenium and Selenium Species in Irrigation Drain Inflows to the Salton Sea, October 2008 and January 2009

a precleaned plastic petri dish (150 mm x 15 mm) with the 

particulate side up and sealed with its corresponding cover for 

freezer storage and transport to the USGS. The plate filtration 

unit was rinsed with 0.1 percent nitric acid (HNO3), followed 

by a DI water rinse after sampling was completed at each site. 

Sediment: Five sampling points for sediment collection were identified along the length of each drain. At each 

sampling point, the uppermost 2 to 6 cm of sediment were 

collected with a stainless steel dredge. The dredge was cleared 

of mud and rinsed with site water while used within a drain. 

At a new site, the dredge was rinsed with DI water followed 

by site water before the first sample was collected. From each 

of the five sampling points, enough sediment to fill a 250-mL 

container was collected and mixed to form a composite sample 

(1,250-mL total). An aliquot of this composite was then placed 

into a 120- and a 500-mL polypropylene container for each 

drain sampled. All containers were placed on ice in the field. 

Samples were chilled (~4 0C) during transport to the USGS. 

Midge Larvae and Detritus: An insect sweep net was 

used to collect samples of midge larvae and detritus, which 

were then sorted and hand picked with plastic tweezers in a 

polypropylene sieve, and stored temporarily in a plastic foodstorage container on ice. After rinsing with DI water, samples 

were wrapped in plastic wrap, stored in separate plastic bags, 

and frozen.

Fish: Composite samples of western mosquitofish and 

sailfin molly were collected with seine nets and minnow traps; 

sampled fish from each site were stored temporarily in a plastic food-storage container on ice. Upon return to the Refuge 

laboratory, the whole-body fish were measured for standard 

length, weighed, and rinsed with DI water. Each fish composite sample (n=36) was wrapped in plastic wrap and placed into 

a plastic bag and frozen. 

Algae and Plankton: Algae were collected from floating 

masses or scraped from sticks and rocks at each drain site and 

stored temporarily in a sealable plastic food-storage container 

on ice. Following collection, the material was rinsed with 

DI water, wrapped with plastic wrap, stored in a plastic bag, 

and frozen. Plankton was collected with a tow net and after 

draining site water, each sample was rinsed three times with 

DI water. The plankton and the DI rinsing water were placed 

in a 120-mL polypropylene container. Collected samples were 

stored on ice in the field and frozen immediately upon return 

to the Refuge.

Sampling History

The irrigation drain monitoring samples collected by 

USGS personnel were received in six shipments by the Environmental Chemistry Branch Inorganic Section (henceforth 

referred to as “the laboratory”) of the USGS shortly after 

collection to meet the 7 day holding time specified for TSS 

in water and the 14-day holding time for total organic carbon 

(TOC) in sediments. 

The first set of samples was collected from October 15 to 

17, 2008, received by the laboratory on October 21, 2008, and 

contained 17 TSS water samples, 26 water samples for total 

selenium, and 6 water samples for total dissolved selenium. 

The samples were assigned USGS batch number 1525 and 

USGS sample identification numbers 44164 to 44212.

The second set of samples was collected from October 15 

to 21, 2008, received by the laboratory on October 23, 2008, 

and contained 14 TSS water samples, 22 total selenium water 

samples, 11 total dissolved selenium water samples, 8 sediment samples for total selenium, 8 sediment samples for TOC 

and particle size analysis (PSA), and 15 particulate selenium 

filter samples. The samples were assigned USGS batch number 1530 and USGS sample identification numbers 44395 to 

44472. 

The third set of samples was received by the laboratory 

on October 24, 2008, and contained two filters to serve as 

blanks. The samples were assigned USGS batch number 1533 

and USGS sample identification numbers 44485 to 44486.

The fourth set of samples was collected from October 15 

to 21, 2008, received by the laboratory on November 5, 2008, 

and contained 42 fish samples, 21 algae samples, 21 midge 

samples, 21 detritus samples, and 21 plankton samples. The 

samples were assigned USGS batch number 1538 and USGS 

sample identification numbers 44570 to 44695.

The fifth set of samples was collected from January 8 to 

11, 2009, received by the laboratory on January 13, 2009, and 

contained 31 TSS water samples and 62 total selenium water 

samples. The samples were assigned USGS batch number 

1553 and USGS sample identification numbers 45067 to 

45159.

Homogenization and Lyophilization

Frozen fish samples were minced with a small ceramic 

knife before freeze drying. Particulates, biota, detritus, and 

sediment samples were lyophilized in a Virtis Genesis® 35EL 

freeze dryer and percent moisture was determined as part of 

the lyophilization process; however, percent moisture was not 

determined for plankton samples because the sample matrix 

included DI water. After lyophilization, all midge larvae, 

detritus, plankton, algae, and fish samples were homogenized 

by grinding with a glass rod against the container surface. 

Dried sediment was placed into a plastic bag, sealed, and then 

pulverized by using a rolling pin on the plastic bag to produce 

a coarse powder product. Dried filters containing particulates 

did not require any additional homogenization after freeze 

drying. 

Chemical Procedures

Total Selenium in Water: Before analysis, all water samples were stored in the dark at ~4 o

C. For the subsequent determination of total selenium in filtered and unfiltered samples, 

a 20-mL aliquot of each acidified water sample was subjected 
Methods 3

to an HNO3–magnesium nitrate [Mg(NO3)2] ashing procedure, 

followed by treatment with HCl. The ashing procedure consisted of three steps: boiling with HNO3

 for solubilization and 

partial oxidation; ashing at 500 oC with Mg(NO3)2 to complete 

the oxidation and decompose remaining organic matter; and 

heating with 20 mL of 50 percent (v/v) HCl to dissolve the ash 

and chemically reduce selenium to the selenite (Se+4 ) oxidation state required for detection by hydride generation atomic 

absorption spectrophotometry. Following reduction, digestates 

were diluted to ~100 mL with DI water, yielding a final acid 

matrix of 10 percent HCl.

Selenite + Selenate in Water: Ten mL of filtered water and 

5 mL of concentrated HCl were placed in a 25-mL borosilicate 

test tube and heated to about 130 oC in a well incubator block 

for 3 to 4 hours. After cooling, the liquid was transferred into a 

125-mL polyethylene bottle, and the final volume was adjusted 

to 50 mL with DI water. The final matrix was 10 percent HCl.

Filtered Particulates: A dried filter containing particulates was rolled up, cut into pieces, and the entire filter was 

put into a 100-mL glass beaker. The filter was then subjected 

to the ashing procedure as described earlier for total selenium 

in water. The same procedure was conducted on clean filters, 

which served as blanks.

Biota, Detritus, and Sediment: An approximately 0.25-

gram (g) aliquant of each dried sample was subjected to a 

HNO3–Mg(NO3)2 ashing procedure, followed by HCl chemical reduction of selenate to selenite for the determination of 

selenium. The steps in the procedure were the same as those 

described above for total selenium in water. Digestates were 

diluted to about 100 mL with DI water, yielding a final acid 

matrix of 10 percent HCl.

Instrumental Analysis

Total Selenium: Total selenium was determined in all 

ashed samples by flow injection hydride generation atomic 

absorption spectrophotometry (FIHGAAS). In this procedure, 

the digestate is mixed with an HCl-carrier solution and then 

reduced by sodium tetrahydridoborate that has been stabilized 

with sodium hydroxide. Selenium in the sample is converted 

to volatile hydrogen selenide and transferred with argon carrier gas into a heated quartz cell mounted on an atomic absorption spectrophotometer for decomposition into atomic vapor 

and measurement. 

Selenite in Water: An aliquot of each filtered water 

sample was analyzed directly by FIHGAAS after acidification 

to 10 percent HCl.

Selenate and Selenite in Water: Samples prepared in 

this manner were analyzed directly by FIHGAAS to provide 

selenate + selenite concentrations. The selenate concentration 

was calculated by difference using the formula: 

selenate = (selenate + selenite) – selenite. (1)

Particulate Selenium in Water: Selenium associated with 

filtered particulates was determined by analyzing ashed filters 

by FIHGAAS. The mass of selenium in micrograms for the 

particulates was divided by the volume of water filtered for 

each drain site (0.5 or 1 L) to produce a microgram per liter 

concentration.

Dissolved Organic Selenium in Water: Dissolved organic 

selenium was estimated using the following formula: 

dissolved organic selenium = total dissolved selenium – 

(selenate + selenite). (2)

Total dissolved selenium is defined as the analysis of filtered 

water for total selenium.

Total Suspended Solids: Upon arrival at the laboratory, 

all TSS samples were transferred to the Ecology Branch 

for TSS analysis. TSS were analyzed with methods recommended by the American Public Health Association (1998). 

Samples were brought to room temperature and mixed with 

a magnetic stirrer and subsequent manual inversions of the 

sample container. The sample was measured into a graduated 

cylinder, poured into a filtration apparatus, and filtered through 

a ProWeigh® glass fiber filter. The samples were prewashed 

three times in DI water, dried at 105 °C, and weighed to the 

nearest 0.1 milligram (mg). Sample volume varied to yield a 

dried residue between 2.5 and 200 mg. For each volume of 

sample used, an equal volume of DI water also was filtered 

for a blank determination. After filtering, large or nonhomogeneous materials were removed from the filter and the filter was 

rinsed with three 10-mL aliquots of DI water. Filters were then 

dried for at least 1 hour in a 103 to 105 °C oven and cooled to 

room temperature in a desiccator, then filter and residue were 

weighed to the nearest 0.1 mg. Drying, cooling, and weighing 

of the filter were repeated until the weight difference was less 

than (<) 4 percent or 0.5 mg, whichever was less. The average 

of these weights was used to determine the constant weight of 

the filter and residue, which was then corrected for any weight 

gain or loss of the blank. After subtracting the filter weight, 

this blank-corrected dried residue in milligrams was divided 

by the sample volume in liters to yield TSS in milligrams per 

liter (mg/L). 

Particle-Size Analysis: Sediment samples designated 

for PSA were transferred to the USGS Ecology Branch upon 

arrival. The method requires use of a Bouyoucos hydrometer, 

adapted from American Society for Testing and Materials 

(2003). Wet sediment was sieved through a 2-mm sieve to 

remove any particles larger than coarse sand and then dried at 

60 oC using a convectional drying oven. Approximately 100 

g of dried sediment was mixed with 250 mL of DI water and 

100 mL of a 50 mg/L sodium hexametaphosphate solution. 

A stir bar was then added and the mixture was stirred with a 

magnetic stirring plate. After calibrating the hydrometer, the 

suspended sediment mixture was transferred to a sedimentation cylinder and the volume adjusted to 1 L with DI water. 

After allowing for thermal equilibration, the temperature was 

recorded. Cylinder contents were then thoroughly mixed, and 
4 Total Selenium and Selenium Species in Irrigation Drain Inflows to the Salton Sea, October 2008 and January 2009

the hydrometer was inserted into the suspension. The meniscus reading was taken after 30 seconds and the hydrometer 

was removed and dried. After 120 minutes, the hydrometer 

was reinserted and the meniscus read again. All hydrometer 

meniscus readings were corrected by adjusting +0.25 for each 

degree above 18 oC and -0.25 for each degree below 18 oC. 

Percent fractions were determined as follows:

grams sand = sediment dry weight – (corrected 30 second 

reading – corrected calibration); percent sand = grams sand/

sediment dry weight x 100;

grams clay = sediment dry weight – (corrected 120 minute 

reading – corrected calibration); percent clay = grams clay/

sediment dry weight x 100; andpercent silt = 100 – (percent 

sand + percent clay). 

Total Organic Carbon: TOC was determined with a 

Universal Instruments Corporation (UIC) Model 5014 Coulometer that determines carbon in any carbon dioxide (CO2

) 

containing gas stream (Universal Instruments Corporation, 

1999). The coulometer is used as a detector with different 

carbon front-end units and can detect carbon in the range of 

0.01 micrograms (μg) to 100 mg. The coulometer cell is filled 

with a proprietary solution containing monoethanolamine and 

a colorimetric pH indicator. Platinum (cathode) and silver 

(anode) electrodes are positioned in the cell. The cell assembly 

is then placed in the coulometer cell compartment between 

a light source and a photodetector in the coulometer. As a 

CO2 gas stream passes into the cell, the CO2 is quantitatively 

absorbed and reacts with the monoethanolamine to form a 

titratable acid. This acid causes the color indicator to fade. A 

photodetector monitors the change in the color of the solution as a percent transmittance (percent T). As the percent T 

increases, the titration current automatically is activated to 

electrochemically generate base at a rate proportional to the 

percent T (approximately 1,500 μg carbon/minute). When the 

solution returns to its original color (original percent T), the 

current stops. 

For TOC analysis, total carbon (TC, μg/mg) and total 

inorganic carbon (TIC, μg/mg) are determined. Total carbon 

is determined by combustion of weighed sediments at 925 oC. 

In TIC analysis, weighed sediments are exposed to heated 2 N 

sulfuric acid.Any inorganic carbonates are chemically reduced 

to mineral components and CO2 gas. The gas is carried in high 

purity oxygen to the coulometer cell, where it is measured 

by the procedure described above. Percent TOC is calculated 

as follows:

Percent TOC = [(TC – TIC)/TC] x 100 (3)

Quality Assurance

Samples were processed through the preparative and 

analytical flow scheme in 11 analytical blocks for selenium, 

2 blocks for TSS, and 1 block each for PSA and TOC. Each 

block was assigned a block initiation date (BID) used to identify samples and quality-control samples/materials prepared 

and analyzed collectively as a unit. For samples analyzed 

by atomic absorption for total selenium, predigestion quality control included digestion blanks, replicates, spikes, and 

reference solutions. Analytical quality-control for selenium 

included calibration verification solutions, replicate analyses, 

and analysis spikes. Quality control for the TSS, PSA, and 

TOC determinations included reference materials, duplicates, 

and replicates. 

Results

Total Selenium: Total selenium concentrations [micrograms per liter, (μg/L)] in unfiltered water samples for the 

October 2008 samples are listed in table 1. Mean selenium 

concentrations were most elevated in water from Trifolium 22 

drain (8.04), followed by P drain (7.07). The lowest mean selenium concentration was from San Felipe Wash drain (1.00). 

Data for the January 2009 samples are listed in table 2. Mean 

selenium concentrations were highest in Trifolium Storm drain 

(33.6), followed by Trifolium 18 drain (19.7), and Q drain 

(11.4). The lowest mean selenium concentration was from U 

drain (1.26).

Total Dissolved Selenium and Selenium Species: Dissolved selenite, dissolved selenate, dissolved organic selenium, total dissolved selenium, and particulate selenium 

concentrations (μg/L) from filtered water samples collected 

during the October 2008 sampling are presented in table 3. 

The dissolved organic selenium fraction is assumed to include 

seleno-amino acids and dissolved seleno-peptides, Se(0) as a 

pseudo-dissolved microcolloid, and inorganic Se(-II) species 

(Cutter and Bruland, 1984). Speciation measurements revealed 

that selenium in the sampled drains exists predominately as 

selenate (61 to 93 percent) followed by selenite (4 to 27 percent), typical of waters where selenium is leached out of 

selenium containing marine shales and associated soils under 

alkaline and oxidizing conditions. 

Total Suspended Solids: TSS concentrations (mg/L) in 

unfiltered water collected during the October 2008 and January 2009 samplings are presented in table 4. TSS concentrations ranged from a high of 192 (T drain) to a low of 6.1 (Former Trifolium 20 drain) for the October 2008 collection, and a 

high of 216 (Vail 5 drain) to a low of 9.00 (Niland 4 drain) for 

the January 2009 collection. 

Biota: Percent moisture and concentrations of selenium 

[micrograms per gram (μg/g) dry weight] in biota (algae, 

plankton, midge larvae, western mosquitofish, and sailfin 

molly) are presented in table 5. Selenium concentration ranges 

for each matrix were as follows: algae, 1.68 to 8.26; plankton, 

0.79 to 3.66; midges, 2.68 to 50.6; and fish, 3.09 to 30.4.

Detritus and Sediment: Percent moisture and selenium 

concentrations (μg/g dry weight) in detritus and sediment are 

presented in table 6. Selenium in detritus ranged from 1.78 to 
Results 5

Table 1. Total selenium concentrations in duplicates of unfiltered irrigation drain water samples, Salton Sea, California, 

October 2008.

[USGS, United States Geological Survey; ID, identification; Rep, field replicate; μg/L, microgram per liter; SD, standard deviation; ---, no data; <, less than; 

nc, not collected]

USGS ID Field ID Drain

name/ID

Collection 

date

Total selenium concentration

SD Rep 1

 (μg/L)

Rep 2

 (μg/L)

Mean

 (μg/L)

44440 BLANK-1 --- 10/23/08 < 0.15 --- --- ---

44441 BLANK-2 --- 10/23/08 < 0.15 --- --- ---

44442 BLNDWATSE14 --- 10/16/08 4.31 --- --- ---

44443 BLNDWATSE14B --- 10/21/08 2.98 --- --- ---

44205,44206 LKLNWATSE14 Lack & Linsey Pond 10/17/08 3.64 3.53 3.58 0.08

44181,44182 NLD1WATSE14 Niland 1 10/16/08 1.53 1.53 1.53 0.00

44183,44184 NLD2WATSE14 Niland 2 10/16/08 2.17 2.19 2.18 0.02

44185,44186 NLD3WATSE14 Niland 3 10/16/08 1.87 1.92 1.89 0.03

44187,44188 NLD4WATSE14 Niland 4 10/16/08 2.26 2.39 2.33 0.09

nc1 OOOOWATSE14 O --- --- --- --- ---

44199,44200 PPPPWATSE14 P 10/17/08 7.14 7.00 7.07 0.10

nc1 POEDWATSE14 Poe Rd --- --- --- --- ---

44203,44204 PUMCWATSE14 Pumice 10/17/08 4.90 4.86 4.88 0.03

44197,44198 QQQQWATSE14 Q 10/17/08 3.67 3.79 3.73 0.09

44195,44196 RRRRWATSE14 R 10/17/08 2.13 2.01 2.07 0.08

44193,44194 SSSSWATSE14 S 10/17/08 2.72 2.65 2.68 0.05

44448,44449 SFWHWATSE14 San Felipe Wash 10/18/08 0.98 1.03 1.00 0.03

nc1 TTTTWATSE14 T --- --- --- --- ---

44452,44453 TR01WATSE14 Trifolium 1 10/21/08 4.96 4.97 4.97 0.01

44456,44457 TR12WATSE14 Trifolium 12 10/21/08 4.75 4.75 4.75 0.00

44454,44455 TR13WATSE14 Trifolium 13 10/19/08 3.50 3.59 3.54 0.06

nc1 TR14WATSE14 Trifolium 14 --- --- --- --- ---

nc1 TR18WATSE14 Trifolium 18 --- --- --- --- ---

44460,44461 TR19WATSE14 Trifolium 19 10/18/08 1.90 1.82 1.86 0.06

44444,44445 FT20WATSE14 Former Trifolium 20 10/18/08 4.30 4.34 4.32 0.03

nc1 TR20WATSE14 Trifolium 20 --- --- --- --- ---

44446,44447 TR22WATSE14 Trifolium 22 10/18/08 8.03 8.05 8.04 0.01

44450,44451 TR23WATSE14 Trifolium 23 10/18/08 3.77 3.83 3.80 0.04

44458,44459 TRSTWATSE14 Trifolium Storm 10/21/08 3.15 3.06 3.10 0.06

44191,44192 UUUUWATSE14 U 10/16/08 1.70 1.66 1.68 0.03

44201,44202 VL05WATSE14 Vail 5 10/17/08 4.73 5.02 4.88 0.20

44189,44190 WWWWWATSE14 W 10/16/08 4.39 4.40 4.40 0.002

nc1 ZSPLWATSE14 Z Spill --- --- --- --- ---

1

Drain was one of seven selected for intensive sampling (see table 3).
6 Total Selenium and Selenium Species in Irrigation Drain Inflows to the Salton Sea, October 2008 and January 2009

Table 2. Total selenium concentrations in duplicates of unfiltered irrigation drain water samples, Salton Sea, California, 

January 2009.

[USGS, United States Geological Survey; ID, identification; Rep, field replicate; μg/L, micrograms per liter; SD, standard deviation; <, less than]

 USGS ID Field ID Drain

name/ID

Collection 

date

Total selenium concentration

SD Rep 1

(μg/L)

Rep 2

(μg/L)

Mean

(μg/L)

45098 Blank 1 --- 01/13/09 < 0.080 --- --- ---

45099 Blank 2 --- 01/13/09 < 0.080 --- --- ---

45100 BLNDWATSE15 --- 01/08/09 3.02 --- --- ---

45101 BLNDWATSE15B --- 01/10/09 4.72 --- --- ---

45104,45105 LKLNWATSE15 Lack & Linsey Pond 01/10/09 5.05 5.03 5.04 0.01

45106,45107 NLD1WATSE15 Niland 1 01/08/09 1.41 1.48 1.44 0.05

45108,45109 NLD2WATSE15 Niland 2 01/08/09 1.76 1.74 1.75 0.02

45110,45111 NLD3WATSE15 Niland 3 01/08/09 1.58 1.64 1.61 0.05

45112,45113 NLD4WATSE15 Niland 4 01/08/09 2.91 2.72 2.82 0.13

45114,45115 OOOOWATSE15 O 01/10/09 3.59 3.74 3.66 0.11

45118,45119 PPPPWATSE15 P 01/08/09 2.14 2.17 2.16 0.02

45116,45117 POEDWATSE15 Poe Rd 01/09/09 4.57 4.39 4.48 0.13

45120,45121 PUMCWATSE15 Pumice 01/11/09 2.11 2.68 2.39 0.40

45122,45123 QQQQWATSE15 Q 01/08/09 11.5 11.3 11.4 0.14

45124,45125 RRRRWATSE15 R 01/08/09 1.60 1.45 1.53 0.11

45128,45129 SSSSWATSE15 S 01/08/09 2.56 2.48 2.52 0.05

45126,45127 SFWHWATSE15 San Felipe Wash 01/10/09 2.45 2.07 2.26 0.27

45150,45151 TTTTWATSE15 T 01/08/09 1.40 1.25 1.33 0.11

45130,45131 TR01WATSE15 Trifolium 1 01/09/09 5.80 5.72 5.76 0.05

45132,45133 TR12WATSE15 Trifolium 12 01/09/09 4.18 4.33 4.26 0.10

45134,45135 TR13WATSE15 Trifolium 13 01/09/09 5.04 4.78 4.91 0.19

45136,45137 TR14WATSE15 Trifolium 14 01/09/09 3.34 3.10 3.22 0.17

45138,45139 TR18WATSE15 Trifolium 18 01/09/09 19.6 19.8 19.7 0.08

45140,45141 TR19WATSE15 Trifolium 19 01/10/09 3.51 3.47 3.49 0.02

45102,45103 FT20WATSE15 Former Trifolium 20 01/10/09 4.54 4.28 4.41 0.18

45142,45143 TR20WATSE15 Trifolium 20 01/10/09 5.07 4.95 5.01 0.09

45144,45145 TR22WATSE15 Trifolium 22 01/10/09 4.85 4.68 4.76 0.12

45146,45147 TR23WATSE15 Trifolium 23 01/10/09 3.32 3.31 3.31 0.005

45148,45149 TRSTWATSE15 Trifolium Storm 01/09/09 33.6 33.6 33.6 0.04

45152,45153 UUUUWATSE15 U 01/08/09 1.33 1.19 1.26 0.11

45154,45155 VL05WATSE15 Vail 5 01/11/09 5.21 4.81 5.01 0.28

45156,45157 WWWWWATSE15 W 01/08/09 3.05 2.93 2.99 0.09

45158,45159 ZSPLWATSE15 Z Spill 01/08/09 4.21 4.12 4.16 0.06
Table 3. Total dissolved selenium, dissolved selenium species, and particulate selenium concentrations in filtered irrigation drain water samples, SOctober 2008.[USGS, United States Geological Survey; ID, identification; Rep, replicate; [Se03]-2, selenite; [Se04]-2, selenate; Se, selenium; μg/L, micrograms per liter; ---, no data; <, less 

USGS ID Field ID Drain name/ID Rep Collection fate Dissolved [Se03]-2 (μg/L)

1Calculated 

dissolved 

[Se04]-2

(μg/L)

2Calculated 

dissolved 

organic Se

(μg/L)

Measured 

total dissolved Se 

(μg/L)

3

pa

44463 BLNKWADSE14 --- 1 10/19/08 < 0.072 < 0.11 --- < 0.38 44464 BLNKWADSE14B --- 2 10/19/08 < 0.072 < 0.11 --- < 0.38 44462 BLNDWADSE14 --- --- 10/16/08 0.63 3.65 0.11 4.39 44207 OOOOWADSE14 O 1 10/15/08 0.71 3.39 0.10 4.20 44208 OOOOWADSE14B O 2 10/15/08 0.72 3.53 0.00 4.22 44465 POEDWADSE14 Poe Rd 1 10/20/08 1.81 7.40 0.94 10.1 44466 POEDWADSE14B Poe Rd 2 10/20/08 1.96 7.83 0.36 10.2 44209 TTTTWADSE14 T 1 10/17/08 0.35 1.06 0.22 1.63 44210 TTTTWADSE14B T 2 10/17/08 0.34 1.06 0.11 1.50 44467 TR14WADSE14 Trifolium 14 1 10/19/08 0.30 7.7 0.21 8.21 44468 TR14WADSE14B Trifolium 14 2 10/19/08 0.35 7.1 0.22 7.67 44469 TR18WADSE14 Trifolium 18 1 10/21/08 1.52 12.8 0.49 14.8 44470 TR18WADSE14B Trifolium 18 2 10/21/08 1.55 12.9 0.31 14.8 44471 TR20WADSE14 Trifolium 20 1 10/18/08 0.56 1.45 0.01 2.01 44472 TR20WADSE14B Trifolium 20 2 10/18/08 0.55 1.44 0.22 2.22 44211 ZSPLWADSE14 Z Spill 1 10/16/08 0.57 3.66 0.18 4.41 44212 ZSPLWADSE14B Z Spill 2 10/16/08 0.58 3.74 0.04 4.37 

1Calculated dissolved [Se04]-2 = measured ([Se04]-2 + [Se03]-2) - measured [Se03]-2.2Calculated dissolved Organic Se = measured total dissolved Se - measured ([Se04]-2 + [Se03]-2).3Measured particulate Se = μg of Se in filtered particulates divided by volume of site water filtered.4Calculated total Se = measured particulate Se + measured total dissolved Se.
8 Total Selenium and Selenium Species in Irrigation Drain Inflows to the Salton Sea, October 2008 and January 2009

 Table 4. Total suspended solids concentrations in unfiltered Salton Sea, California, irrigation drain water samples, October 2008 

and January 2009.

[USGS, United States Geological Survey; ID, identification; TSS, total suspended solids; mg/L, milligram per liter; bold and italicized values are less than 

the method quantitation limit and have high uncertainty]

Field ID Drain

name/ID

October, 2008 January, 2009

USGS ID TSS

(mg/L) USGS ID TSS(mg/L)

BLNDWATSSA Blind A 44178 99. 45067 32.

BLNDWATSSB Blind B 44407 29. 45068 40.

LKLNWATSS Lack & Linsey Pond 44180 93. 45070 46.

NLD1WATSS Niland 1 44164 83. 45071 36.

NLD2WATSS Niland 2 44165 20. 45072 41.

NLD3WATSS Niland 3 44166 64. 45073 43.

NLD4WATSS Niland 4 44167 47. 45074 9.0

OOOOWATSS O 44176 118. 45075 35.

PPPPWATSS P 44175 86. 45077 115.

POEDWATSS Poe Rd 44400 77. 45076 179.

PUMCWATSS Pumice 44177 151. 45078 99.

QQQQWATSS Q 44174 28. 45079 33.

RRRRWATSS R 44173 87. 45080 59.

SSSSWATSS S 44172 92. 45082 48.

SFWHWATSS San Felipe Wash 44397 44. 45081 13.

TTTTWATSS T 44171 192. 45093 54.

TR01WATSS Trifolium 1 44408 19. 45083 66.

TR12WATSS Trifolium 12 44404 33. 45084 213.

TR13WATSS Trifolium 13 44403 40. 45085 84.

TR14WATSS Trifolium 14 44406 94. 45086 55.

TR18WATSS Trifolium 18 44399 7.2 45087 23.

TR19WATSS Trifolium 19 44401 16. 45088 40.

FT20WATSS Former Trifolium 20 44395 6.1 45069 43.

TR20WATSS Trifolium 20 44402 78. 45089 66.

TR22WATSS Trifolium 22 44396 21. 45090 62.

TR23WATSS Trifolium 23 44398 28. 45091 114.

TRSTWATSS Trifolium Storm 44405 17. 45092 186.

UUUUWATSS U 44170 40. 45094 28.

VLO5WATSS Vail 5 44179 31. 45095 216.

WWWWWATSS W 44169 112. 45096 153.

ZSPLWATSS Z Spill 44168 89. 45097 45.

1

Trifolium 1 drain was dry at time of collection.
Results 9

Table 5. Selenium concentrations in biota samples collected from Salton Sea, California, irrigation drains, October 2008. 

[USGS, United States Geological Survey; ID, identification; μg/g, microgram per gram; ---, no data]

 USGS ID Field ID Matrix Drain

name/ID

Moisture

(percent)

Selenium

(μg/g dry weight)

44621 OOOOALGTSE14A algae O 70.5 3.28

44622 OOOOALGTSE14B algae O 70.2 3.38

44623 OOOOALGTSE14C algae O 70.5 3.46

44618 POEDALGTSE14A algae Poe 56.8 2.26

44619 POEDALGTSE14B algae Poe 56.0 2.31

44620 POEDALGTSE14C algae Poe 55.2 2.29

44612 TTTTALGTSE14A algae T 75.4 4.99

44613 TTTTALGTSE14B algae T 76.6 5.76

44614 TTTTALGTSE14C algae T 75.4 5.58

44624 TR14ALGTSE14A algae Trifolium 14 63.3 1.88

44625 TR14ALGTSE14B algae Trifolium 14 63.1 1.89

44626 TR14ALGTSE14C algae Trifolium 14 62.8 1.82

44630 TR18ALGTSE14A algae Trifolium 18 66.4 7.84

44631 TR18ALGTSE14B algae Trifolium 18 66.5 8.05

44632 TR18ALGTSE14C algae Trifolium 18 65.7 8.26

44615 TR20ALGTSE14A algae Trifolium 20 67.3 2.65

44616 TR20ALGTSE14B algae Trifolium 20 64.9 2.68

44617 TR20ALGTSE14C algae Trifolium 20 66.0 2.91

44627 ZSPLALGTSE14A algae Z Spill 67.8 1.68

44628 ZSPLALGTSE14B algae Z Spill 65.5 1.52

44629 ZSPLALGTSE14C algae Z Spill 68.9 1.76

44684 OOOONPTSE14A plankton O --- 2.72

44685 OOOONPTSE14B plankton O --- 3.12

44686 OOOONPTSE14C plankton O --- 2.44

44681 POEDNPTSE14A plankton Poe --- 1.45

44682 POEDNPTSE14B plankton Poe --- 1.10

44683 POEDNPTSE14C plankton Poe --- 0.79

44675 TTTTNPTSE14A plankton T --- 2.99

44676 TTTTNPTSE14B plankton T --- 2.82

44677 TTTTNPTSE14C plankton T --- 3.45

44687 TR14NPTSE14A plankton Trifolium 14 --- 2.56

44688 TR14NPTSE14B plankton Trifolium 14 --- 2.15

44689 TR14NPTSE14C plankton Trifolium 14 --- 1.81

44693 TR18NPTSE14A plankton Trifolium 18 --- 1.88

44694 TR18NPTSE14B plankton Trifolium 18 --- 2.53

44695 TR18NPTSE14C plankton Trifolium 18 --- 2.59

44678 TR20NPTSE14A plankton Trifolium 20 --- 1.16

44679 TR20NPTSE14B plankton Trifolium 20 --- 3.66

44689 TR20NPTSE14C plankton Trifolium 20 --- 1.95

44690 ZSPLNPTSE14A plankton Z Spill --- 3.01

44691 ZSPLNPTSE14B plankton Z Spill --- 2.62
10 Total Selenium and Selenium Species in Irrigation Drain Inflows to the Salton Sea, October 2008 and January 2009

Table 5. Selenium concentrations in biota samples collected from Salton Sea, California, irrigation drains, October 2008.—

Continued

[USGS, United States Geological Survey; ID, identification; μg/g, microgram per gram; ---, no data]

 USGS ID Field ID Matrix Drain

name/ID

Moisture

(percent)

Selenium

(μg/g dry weight)

44692 ZSPLNPTSE14C plankton Z Spill --- 2.45

44642 OOOOCHITSE14A midge O 81.8 3.06

44643 OOOOCHITSE14B midge O 82.0 2.68

44644 OOOOCHITSE14C midge O 81.5 2.97

44639 POEDCHITSE14A midge Poe 83.0 17.2

44640 POEDCHITSE14B midge Poe 81.1 15.2

44641 POEDCHITSE14C midge Poe 84.0 18.2

44633 TTTTCHITSE14A midge T 81.3 6.37

44634 TTTTCHITSE14B midge T 80.8 6.66

44635 TTTTCHITSE14C midge T 81.6 6.43

44645 TR14CHITSE14A midge Trifolium 14 80.2 7.09

44646 TR14CHITSE14B midge Trifolium 14 79.8 7.72

44647 TR14CHITSE14C midge Trifolium 14 80.3 6.55

44651 TR18CHITSE14A midge Trifolium 18 84.6 44.2

44652 TR18CHITSE14B midge Trifolium 18 84.3 44.0

44653 TR18CHITSE14C midge Trifolium 18 85.0 50.6

44636 TR20CHITSE14A midge Trifolium 20 82.0 6.59

44637 TR20CHITSE14B midge Trifolium 20 80.4 6.09

44638 TR20CHITSE14C midge Trifolium 20 82.7 6.47

44648 ZSPLCHITSE14A midge Z Spill 79.4 4.15

44649 ZSPLCHITSE14B midge Z Spill 79.2 3.63

44650 ZSPLCHITSE14C midge Z Spill 77.0 3.78

44588 OOOOGMBTSE14A gambusia O 78.5 4.41

44589 OOOOGMBTSE14B gambusia O 77.8 4.24

44590 OOOOGMBTSE14C gambusia O 78.8 4.56

44591 OOOOSLMTSE14A sailfin molly O 78.5 3.09

44592 OOOOSLMTSE14B sailfin molly O 78.7 4.11

44593 OOOOSLMTSE14C sailfin molly O 78.8 3.71

44582 POEDGMBTSE14A gambusia Poe 77.2 16.6

44583 POEDGMBTSE14B gambusia Poe 76.6 15.2

44584 POEDGMBTSE14C gambusia Poe 77.3 13.2

44585 POEDSLMTSE14A sailfin molly Poe 78.8 16.0

44586 POEDSLMTSE14B sailfin molly Poe 78.9 17.2

44587 POEDSLMTSE14C sailfin molly Poe 77.8 15.2

44570 TTTTGMBTSE14A gambusia T 74.8 6.23

44571 TTTTGMBTSE14B gambusia T 75.1 6.07

44572 TTTTGMBTSE14C gambusia T 75.3 6.08

44573 TTTTSLMTSE14A sailfin molly T 75.8 5.14

44574 TTTTSLMTSE14B sailfin molly T 76.4 6.44

44575 TTTTSLMTSE14C sailfin molly T 75.7 5.31

44594 TR14GMBTSE14A gambusia Trifolium 14 77.7 4.07
Results 11

Table 5. Selenium concentrations in biota samples collected from Salton Sea, California, irrigation drains, October 2008.—

Continued

[USGS, United States Geological Survey; ID, identification; μg/g, microgram per gram; ---, no data]

 USGS ID Field ID Matrix Drain

name/ID

Moisture

(percent)

Selenium

(μg/g dry weight)

44595 TR14GMBTSE14B gambusia Trifolium 14 78.2 4.54

44596 TR14GMBTSE14C gambusia Trifolium 14 77.3 4.29

44597 TR14SLMTSE14A sailfin molly Trifolium 14 75.9 4.59

44598 TR14SLMTSE14B sailfin molly Trifolium 14 76.1 4.65

44599 TR14SLMTSE14C sailfin molly Trifolium 14 76.3 4.79

44606 TR18GMBTSE14A gambusia Trifolium 18 76.7 17.4

44607 TR18GMBTSE14B gambusia Trifolium 18 75.4 17.8

44608 TR18GMBTSE14C gambusia Trifolium 18 75.7 19.2

44609 TR18SLMTSE14A sailfin molly Trifolium 18 78.8 30.4

44610 TR18SLMTSE14B sailfin molly Trifolium 18 77.9 25.3

44611 TR18SLMTSE14C sailfin molly Trifolium 18 77.0 25.0

44576 TR20GMBTSE14A gambusia Trifolium 20 75.4 5.33

44577 TR20GMBTSE14B gambusia Trifolium 20 78.0 5.96

44578 TR20GMBTSE14C gambusia Trifolium 20 76.5 6.13

44579 TR20SLMTSE14A sailfin molly Trifolium 20 76.3 7.57

44580 TR20SLMTSE14B sailfin molly Trifolium 20 76.7 7.70

44581 TR20SLMTSE14C sailfin molly Trifolium 20 75.4 7.14

44600 ZSPLGMBTSE14A gambusia Z Spill 77.6 6.77

44601 ZSPLGMBTSE14B gambusia Z Spill 79.1 6.61

44602 ZSPLGMBTSE14C gambusia Z Spill 79.4 6.18

44603 ZSPLSLMTSE14A sailfin molly Z Spill 75.9 3.93

44604 ZSPLSLMTSE14B sailfin molly Z Spill 76.4 4.84

44605 ZSPLSLMTSE14C sailfin molly Z Spill 77.1 5.31
12 Total Selenium and Selenium Species in Irrigation Drain Inflows to the Salton Sea, October 2008 and January 2009

Table 6. Selenium concentrations in detritus and sediment samples collected from Salton Sea, California, irrigation drains, 

October 2008. 

[USGS, United States Geological Survey; ID, identification; μg/g, micrograms per gram]

 USGS ID Field ID Matrix Drain

name/ID

Moisture

(percent)

Selenium

(μg/g dry weight)

44663 OOOODETTSE14A detritus O 86.3 3.82

44664 OOOODETTSE14B detritus O 85.7 4.85

44665 OOOODETTSE14C detritus O 85.9 6.42

44660 POEDDETTSE14A detritus Poe 74.4 7.10

44661 POEDDETTSE14B detritus Poe 75.3 7.09

44662 POEDDETTSE14C detritus Poe 71.8 6.59

44654 TTTTDETTSE14A detritus T 77.6 2.52

44655 TTTTDETTSE14B detritus T 77.2 1.78

44656 TTTTDETTSE14C detritus T 79.6 2.22

44666 TR14DETTSE14A detritus Trifolium 14 80.7 9.86

44667 TR14DETTSE14B detritus Trifolium 14 82.1 5.14

44668 TR14DETTSE14C detritus Trifolium 14 80.6 6.42

44672 TR18DETTSE14A detritus Trifolium 18 82.4 39.7

44673 TR18DETTSE14B detritus Trifolium 18 83.8 27.4

44674 TR18DETTSE14C detritus Trifolium 18 80.5 58.0

44657 TR20DETTSE14A detritus Trifolium 20 79.0 3.94

44658 TR20DETTSE14B detritus Trifolium 20 77.6 12.4

44659 TR20DETTSE14C detritus Trifolium 20 79.2 4.07

44669 ZSPLDETTSE14A detritus Z Spill 83.2 4.00

44670 ZSPLDETTSE14B detritus Z Spill 82.2 3.14

44671 ZSPLDETTSE14C detritus Z Spill 79.6 3.57

44424 BLNDSDTSE14 sediment Blind 65.4 9.95

44421 OOOOSDTSE14 sediment O 48.7 0.84

44418 POEDSDTSE14 sediment Poe 23.1 0.42

44422 TTTTSDTSE14 sediment T 50.6 0.72

44420 TR14SDTSE14 sediment Trifolium 14 50.7 1.90

44419 TR18SDTSE14 sediment Trifolium 18 65.8 10.0

44417 TR20SDTSE14 sediment Trifolium 20 30.9 1.10

44423 ZSPLSDTSE14 sediment Z Spill 42.3 0.65
Quality Control Results 13

58.0 and from 0.42 to 10.0 in sediment. The particle size 

analyses of sediments, expressed as percent sand, silt, and 

clay, are presented in table 7. Percent sand ranged from 14 to 

76; percent silt from 15 to 57; and percent clay from 7.5 to 50. 

Percent TOC in sediments is given in table 8 and ranged from 

0.2 to 1.5. 

Quality Control Results

Calibration Verification: During the selenium determinations, a calibration verification solution (Spex Claritas PPT®; 

Cat No. CLSe2-2Y) was analyzed at the beginning and end of 

each analytical run. Calibration was considered acceptable if 

the check solution was within plus or minus 10 percent of the 

actual concentration (3 μg/L), which was achieved during all 

analyses.

Reference Materials: Recoveries of selenium from 

QC Plus + Trace Metals Quality Control Standard [n=7 

(7 samples)] and National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) 1643e 

Trace Elements in Water (n=3) averaged 103 percent. The 

recoveries of selenium from National Research Council of 

Canada (NRCC) SRM PACS-1 marine sediment (n=1) was 

100 percent. The International Atomic Energy Agency (IAEA) 

copepod reference material MA-A-1 (n= 2) and the Institute 

for Reference Materials and Measurements Certified Reference Material (CRM) 414 Trace Elements in Plankton (n=2) 

all exhibited selenium recoveries of 100 percent. Recoveries 

of selenium in NRCC CRM DORM-2 dogfish muscle (n=1) 

and IAEA CRM 407 whole-body fish (n=1) were 100 and 

91 percent, respectively. Recoveries of TSS from a TSS reference solution (Environmental Resource Associates Hardness 

Wastewater Standard 507; n=5) averaged 101 percent. The 

recovery of total carbon from a carbon reference material 

(Environmental Resource Associates Nutrients in Soil 542; 

n=1) was 100 percent. Recoveries of percent sand, silt, and 

clay from a CERC research sediment material ranged from 

79 to 99 percent.

Table 7. Particle size distributions in sediment samples collected from Salton Sea, California, irrigation drains, October 2008.

[USGS, United States Geological Survey; ID, identification; >, greater than; mm, millimeter]

USGS ID Field ID Drain

name/ID

Particle size category

> 2 mm

(percent)

Sand

(percent)

Silt

(percent)

Clay

(percent)

44416 BLNDSDTOC14 Blind 0. 55. 37. 7.

44413 OOOOSDTOC14 O 0. 24. 37. 39.

44410 POEDSDTOC14 Poe Rd 0. 76. 15. 10.

44414 TTTTSDTOC14 T 0. 15. 36. 50.

44412 TR14SDTOC14 Trifolium 14 0. 14. 57. 29.

44411 TR18SDTOC14 Trifolium 18 0. 55. 37. 8.

44409 TR20SDTOC14 Trifolium 20 1. 47. 27. 25.

44415 ZSPLSDTOC14 Z Spill 7. 15. 33. 45.

Table 8. Percent total organic carbon in sediment samples collected from Salton Sea, California, irrigation drains, October 2008.

[USGS, United States Geological Survey; ID, identification]

USGS ID Field ID Drain

name/ID

Total organic carbon 

(percent)

42216 BLNDSDTOC14 Blind 1.5

42209 TR20SDTOC14 Trifolium 20 0.7

42210 POEDSDTOC14 Poe Rd. 0.2

42211 TR18SDTOC14 Trifolium 18 1.3

42212 TR14SDTOC14 Trifolium 14 1.1

42213 OOOOSDTOC14 O 0.6

42214 TTTTSDTOC14 T 0.5

42215 ZSPLSDTOC14 Z Spill 1.2
14 Total Selenium and Selenium Species in Irrigation Drain Inflows to the Salton Sea, October 2008 and January 2009

Analytical and Method Precision: Instrumental precision 

for selenium as determined by repeated analysis of a standard throughout the run for each block (n=11) was less than 

5 percent relative standard deviation (RSD). Relative percent 

differences (RPDs) between field duplicates (n=73) of either 

unfiltered or filtered water samples analyzed for selenium or 

selenium species mostly were ≤ (less than or equal) 12 (n=70), 

but two of these duplicates exhibited greater RPDs of 15 

and 24. Both of these RPDs were associated with relatively 

low selenium concentrations (< 5 μg/L). RSDs for triplicate 

field samples of detritus (n=7), algae (n=7), plankton (n=7), 

midge larvae (n=7), and whole-body fish (n=14) analyzed for 

selenium were as follows: algae, 1.0 to 7.5 percent; plankton, 

11 to 56 percent; detritus, 4.2 to 71 percent; midge larvae, 2.4 

to 9.1 percent; and whole-body fish, 1.5 to 15 percent. Once 

again, many of the greatest RSDs were associated with low 

selenium concentrations, but in some instances greater variation apparently reflected greater natural variation of selenium 

in certain sample matrices, for example detritus and plankton. 

Laboratory method precision for triplicate (n=18) preparation and analysis of samples for selenium was <10 percent 

RSD. Instrumental precision was based on duplicate analysis 

of sample digestates from each sample matrix, which resulted 

in RPDs <2 percent. Duplicate analysis of water samples for 

TSS (n=4) resulted in RPDs ranging from 1.0 to 21 percent, 

whereas triplicate analysis for TSS (n=3) resulted in RSDs 

<5 percent. The duplicate analysis of a drain sediment for 

PSA resulted in RPDs <7 percent for the fractions.. Triplicate 

analyses of a drain sediment for PSA resulted in RSDs ≤14 

percent for the fractions. The duplicate analysis of six drain 

sediments for TOC resulted in RPDs 6.9 to 22 percent for five 

drains, but one higher RPD of 82 percent, presumably because 

of a low TOC level (≤1 percent) and the natural heterogeneity 

of the drain sediment. A replicate analysis of one drain sediment resulted in a RSD of 27 percent.

Spikes: Recoveries of selenium [selenite (Se+4), selenate 

(Se+6), or selenomethionine] spiked into a filter blanks (n=1) 

and water samples (n=21) ranged from 89 to 106 percent, 

averaging 98 percent. Recoveries of selenium spiked into sediment (n=2), detritus (n=4), and biota (n=10) ranged from 92 

to 103 percent, averaging 99 percent. Recoveries of selenium 

spikes added to water during analysis (n=17) ranged from 

97 to 110 percent, averaging 102 percent. Analysis spikes 

of sediment (n=1), filtered particulates (n=2), detritus (n=2), 

and biota (n=10) ranged from 98 to 106 percent, averaging 

101 percent. 

Blank Equivalent Concentrations: Blank equivalent 

concentrations (BECs) were computed for selenium for each 

matrix and for TSS blanks analyzed with each set of drain 

water samples. BECs for water and filter particulates were less 

than their respective method detection limits (MDLs). BECs 

(μg/g) for detritus, sediment, and all biota were greater than 

their respective MDLs (μg/g); however, BECs were inconsequential when compared to the lowest selenium concentrations 

in the samples of each matrix. The BECs and corresponding 

MDLs were as follows: detritus, 0.17 compared to 0.019; sediment, 0.17 compared to 0.009; fish, 0.16 compared to 0.022; 

algae, 0.17 compared to 0.012; midge, 0.17 compared to 

0.012; plankton, 0.47 compared to 0.046. Except for plankton 

and sediment, these BECs are considered inconsequential 

relative to the lowest selenium concentrations in the samples 

of each matrix. BECs for TSS were less than their respective 

MDLs. TSS sample data were corrected for procedural blanks, 

whereas total selenium sample data were not blank corrected.

Instrument Detection, Method Detection, and Method 

Quantitation Limits: The FIHGAAS instrument detection limit 

for selenium was 0.02 and 0.033 μg/L, and 0.04 mg for TSS. 

MDLs for each matrix for selenium were computed for each 

analytical block (n=15) using the formula:

3(SDb

2

 + SDs

2

)1/2 (4)

where

SDb = standard deviation of a blank (n=3); and 

SDs = standard deviation of a low level sample or 

spiked sample (n=3).

Calculated MDLs were: water, 0.071 to 0.38 μg/L; filtered 

particulates, 0.004 μg/L; sediment, 0.009 μg/g dry weight; 

algae, 0.012 μg/g dry weight; midge larvae, 0.012 μg/g dry 

weight; plankton, 0.046 μg/g dry weight; detritus, 0.019 μg/g 

dry weight; and whole-body fish, 0.022 μg/g dry weight. 

Method quantitation limits (MQLs) for each matrix were 

calculated as 3.3 x MDLs. MDLs for TSS were 3.09 and 

5.24 mg/L and MQLs were 10.2 and 17.3 mg/L. Overall, 

quality-control results for the study were within acceptable 

limits as specified by USGS.

References Cited

American Public Health Association, 1998, Standard methods 

for the examination of water and wastewater (20th ed.), 

Method 2540: Washington, D.C., American Public Health 

Association, p. 257–258.

American Society for Testing and Materials, 2003, Standard 

test method for particle-size analysis of soils, D422–63 

(2002), in Annual Book of ASTM Standards, v. 04.08: 

West Conshohocken, Pa., American Society for Testing and 

Materials, p. 10–17. 

Cutter, G.A., and Bruland, K.W., 1984, The marine biogeochemistry of selenium—a re-evaluation: Limnology and 

Oceanography, v. 29, no. 6, p. 1,179–1,192.

Universal Instruments Corporation, 1999, Operating manual 

for Model CM 5014 Coulometer.
Publishing support provided by:

Rolla Publishing Service Center

For more information concerning this publication, contact:

Director, USGS Columbia Environmental Research Center

4200 New Haven Road

Columbia, MO 65201

(573) 875–5399

Or visit the Columbia Environmental Research Center Web site at:

http://www.cerc.usgs.gov
May and others—Total Selenium and Selenium Species in Irrigation Drain Inflows to the Salton Sea, October 2008-January 2009—Open-File Report 2009—1123