Selenium Concentrations in Irrigation Drain Inflows 

to the Salton Sea, California, October 2006 and 

January 2007 

Open-File Report 2007–1113 

U.S. Department of the Interior 

U.S. Geological Survey 
Page intentionally blank
Selenium Concentrations in Irrigation Drain Inflows 

to the Salton Sea, California, October 2006 and 

January 2007 

By Thomas W. May, Mike J. Walther, and William G. Brumbaugh 

Open-File Report 2007–1113 

U.S. Department of the Interior 

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

DIRK KEMPTHORNE, Secretary 

U.S. Geological Survey 

Mark D. Myers, Director 

U.S. Geological Survey, Reston, Virginia 2007 

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Suggested citation: 

May, T.W., Walther, M.J., Brumbaugh, W.G., 2007, Selenium concentrations in irrigation drain inflows to 

the Salton Sea, California, October 2006 and January 2007: U.S. Geological Survey Open-File Report 

2007–1113, 18 p. 

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 material contained within this report. 
Contents 

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

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

Sampling History.................................................................................................................................................................1

Methods ...............................................................................................................................................................................2

Field Collection and Preservation................................................................................................................................2

Homogenization and Lyophilization.............................................................................................................................3

Chemical Preparation ....................................................................................................................................................3

Instrumental Analysis ....................................................................................................................................................4

Quality Assurance ..............................................................................................................................................................6

Results ..................................................................................................................................................................................6

Quality Control Results ......................................................................................................................................................7

References Cited ................................................................................................................................................................8

Tables 

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

Sea, California, October 2006.............................................................................................................................9 

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

Sea, California, January 2007...........................................................................................................................10 

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

in filtered irrigation drain water samples, Salton Sea, October 2006.......................................................11 

4. Total suspended solids concentrations in unfiltered Salton Sea irrigation drain water samples, 

October 2006 and January 2007 ......................................................................................................................12 

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

2006.......................................................................................................................................................................13 

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

drains, October 2006..........................................................................................................................................16 

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

October 2006 .......................................................................................................................................................17 

8. Total organic carbon in sediment samples collected from Salton Sea irrigation drains, October 

2006.......................................................................................................................................................................18 

 iii
Conversion Factors 

SI to Inch/Pound 

Multiply By To obtain 

Length 

millimeter (mm) 0.03937 inch (in.) 

micrometer (μm) 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). 

 

iv 
Selenium Concentrations in Irrigation Drain Inflows 

to the Salton Sea, California, October 2006 and 

January 2007 

By Thomas W. May, Mike W. Walther, and William G. Brumbaugh 

Abstract 

This report presents raw data on selenium concentrations in samples of water, sediment, detritus, 

and selected food-chain matrices collected from selected agricultural drains in the southern portion of 

the Salton Sea during October 2006 and January 2007. Total selenium and selenium species were 

determined in water samples, whereas total selenium was determined in sediment, detritus, algae, 

plankton, midge larvae (Family Chironomidae), and two fish species (western mosquitofish, Gambusia 

affinis, and sailfin molly, Poecilia latipinna). 

Introduction 

Selenium concentrations in water, sediment, detritus, and selected food-chain matrices are being 

monitored over a 4-year period in 29 agricultural drains that flow into the southern portion of the Salton 

Sea, California. The monitoring program is funded by the Imperial Irrigation District and conducted by 

two research centers of the U.S. Geological Survey (USGS). The USGS Western Fisheries Research 

Center (WFRC) is responsible for collecting field samples, and the USGS Columbia Environmental 

Research Center (CERC) is responsible for determining selenium concentrations in the samples and 

making other related measurements. This report tabulates raw data generated by CERC from samples 

collected in October 2006 and January 2007. 

Sampling History 

The irrigation drain monitoring samples that are the subject of this report were received in four 

shipments and were collected by personnel of the USGS-WFRC. Shipments were received by the 

Environmental Chemistry Branch Inorganic Section (hereafter referred to as “the lab” in this report) of 

the USGS-CERC shortly after collection to meet the 7-day holding time specified for total suspended 

solids (TSS) in water and the 14-day holding time for total organic carbon (TOC) in sediments. 

The first set of samples was collected October 11–15, 2006, and received by the lab on October 

17, 2006. It contained 15 TSS water samples, 22 total selenium water samples, and 10 filtered selenium 

species water samples. The samples were assigned USGS-CERC batch number 1306 and USGS-CERC 

sample identification numbers 38073–38119. 

 1
The second set of samples was collected October 11–17, 2006, and received by the lab on 

October 19, 2006. It contained 14 TSS water samples, 24 total selenium water samples, 6 filtered 

selenium species water samples, 7 particle-size analysis (PSA) and TOC sediment samples, 7 total 

selenium sediment samples, and 14 total selenium filter media samples. The samples were assigned 

USGS-CERC batch number 1307 and USGS-CERC sample identification numbers 38120–38191. 

The third set of samples was collected October 11–24, 2006, and received by the lab on 

November 14, 2006. It contained 42 whole-body fish samples, 20 algae samples, 20 midge larvae 

samples, 21 detritus samples, and 21 plankton samples. The samples were assigned USGS-CERC batch 

number 1311 and USGS-CERC sample identification numbers 38239–38362. 

The fourth set of samples was collected January 4–7, 2007, and received by the lab on January 9, 

2007. It contained 30 TSS water samples and 62 total selenium water samples. The samples were 

assigned USGS-CERC batch number 1330 and USGS-CERC sample identification numbers 38669–

38760. 

Methods 

Field Collection and Preservation 

The USGS-WFRC sample collectors used the laboratory at the U. S. Fish and Wildlife Service 

Sonny Bono Salton Sea National Wildlife Refuge (hereafter referred to as “the Refuge” in this report) 

for certain aspects of sample processing and for preparing samples for shipment during field trips to 

irrigation drains. Procedures performed in the field or at the Refuge are described for sampling 

unfiltered water, filtered water, particulates, sediment, detritus, and biota, which included midge larvae 

(Family Chironomidae), algae, plankton, and two fish, the western mosquito fish (Gambusia affinis) and 

sailfin molly (Poecilia latipinna).

Unfiltered Water: Each total selenium water sample was poured through a 1-millimeter (mm) 

polypropylene sieve attached to a 1-liter (L) pre-cleaned borosilicate glass bottle. Upon collection, the 

water sample was acidified to a pH less than 2 with 6 Normal hydrochloric acid (HCl), chilled at 

approximately 4 degrees Celsius (~4 oC), and kept in the dark during transport to the USGS-CERC. 

Each TSS water sample was poured through a 1-mm polypropylene sieve attached to a pre-cleaned 

wide-mouth 1-L polypropylene bottle. TSS samples were chilled (~4 oC) during transport to USGSCERC. 

Filtered Water: Water for selenium speciation was filtered using a Geotech® peristaltic pump 

which was 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; 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 eluant was 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, filtered water was discarded. Each filter was 

placed in a pre-cleaned plastic petri dish (150 mm x 15 mm) with particulate side up and sealed with its 

corresponding cover for freezer storage and transport to the USGS-CERC. The plate filtration unit was 

2 
rinsed with 0.1 percent nitric acid (HNO3) followed by a DI water rinse after sampling was completed at 

each site. 

Sediment: Within each drain, five sediment sampling points were identified along the drain 

length. At each sampling point, sediment was 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 for a drain, enough sediment to fill a 250-mL container was collected and mixed to 

form a composite sample. An aliquot of the composite was then placed into a 120- and 500-mL 

polypropylene container. All containers were placed on ice in the field. Samples were chilled (~4 oC) 

during transport to the USGS-CERC. 

Midge Larvae and Detritus: An insect sweep net followed by a polypropylene sieve was used to 

collect midge larvae and detritus, which were then removed from the sieve using plastic tweezers and 

stored temporarily in a plastic food-storage container on ice. After rinsing with DI water, samples were 

wrapped in plastic wrap, stored in separate plastic bags, and kept frozen. 

Fish: Western mosquitofish and sailfin molly were collected with seine nets and minnow traps; 

sampled material from each site was stored temporarily in a plastic food-storage container on ice. Upon 

return to the Refuge lab, the whole-body fish were measured for standard length, weighed, and rinsed 

with DI water. Twenty whole-body fish were wrapped in plastic wrap and placed into a plastic bag. 

Once processed, collected samples were kept frozen. 

Algae and Plankton: If available, 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 

sealable plastic bag, and then frozen. Plankton were collected with a tow net; after draining off 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. 

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 of collected plankton storage in 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 further reduced by using a rolling pin on the plastic bag, moving from the top to bottom 

of the bag to produce a coarse powder product. Dried filters containing particulates did not require any 

additional homogenization after freeze drying. 

Chemical Preparation 

Total Selenium in Water: Before analysis, all water samples were stored in the dark and 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 to a HNO3–magnesium nitrate [Mg(NO3)2] ashing 

3 
procedure followed by treatment with HCl. The ashing procedure consisted of three steps: boiling with 

HNO3 for solubilization and partial oxidation, ashing at 500 o

C with Mg(NO3)2 to complete the 

oxidation and decompose remaining organic matter, and heating with HCl to dissolve the ash and 

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

atomic absorption spectroscopy. 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 120–125 oC in a well incubator block for 2–3 

hours. After cooling, the liquid was transferred into a 60-mL polyethylene bottle and the final volume 

was adjusted to 50 mL with DI water; 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, Detritis, and Sediment: A ~0.25-gram (g) aliquant of each dried sample was subjected to 

a HNO3–Mg(NO3)2 ashing procedure followed by HCl reduction for the determination of selenium. 

The steps in the procedure are the same as those described above for total selenium in water. Digestates 

were diluted to ~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 spectroscopy (FIHGAAS). In this procedure, the digestate is mixed with 

an HCl-carrier solution, and then reduced by sodium tetrahydridoborate, which 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: Filtered water samples were subjected to heating for 1 hour 

with HCl to reduce the selenate species to selenite. 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 + selenite) – selenite = selenate (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 1.0 L) to produce a microgram per 

liter concentration. 

Dissolved Organic Selenium in Water: Dissolved organic selenium was estimated using the 

following formula: 

Total dissolved selenium (Se) – (selenate + selenite) = dissolved organic selenium (2) 

4 
Total Suspended Solids: Upon arrival at the USGS-CERC, all TSS samples were transferred to 

the Ecology Branch for TSS analysis. Total suspended solids were analyzed based on 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 pre-washed three times in DI water, 

dried at 105 °C, and weighed to 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 non-homogeneous 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 103–105 °C oven and cooled to room temperature in a dessicator; filter and 

residue were weighed to at least 0.0001 g on a balance. 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. 

Particle-size Analysis: Sediment samples designated for PSA were transferred to the USGSCERC Ecology Branch upon arrival. The method entails PSA with the Bouyoucos hydrometer, adapted 

from American Society of Testing and Materials (2003a). 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 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 1000 mL with DI water. After 

allowing for thermal equilibration, the temperature was recorded. Cylinder contents were then 

thoroughly mixed followed by insertion of the hydrometer into the suspension. The meniscus reading 

was taken after 30 seconds. 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 o

C 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) (3) 

 

 percent sand = grams sand/sediment dry weight x 100 (4) 

 

grams clay = sediment dry weight – (corrected 120 minute reading – corrected 

calibration) (5) 

 percent clay = grams clay/sediment dry weight x 100 (6) 

 percent silt = 100 – (percent sand + percent clay) (7)

 

5 
Total Organic Carbon: The TOC method was adapted from American Society of Testing and 

Materials (2003b). Sediment samples designated for TOC analysis were transferred to the USGSCERC Ecology Branch upon arrival. Approximately 50 g of wet sediment was heated to a constant 

weight at 105 oC in a convectional drying oven. After recording the dry sediment weight, the sample 

was ashed in a muffle furnace overnight at 440 o

C. The ashed sample was weighed, wet with a small 

amount of DI water, dried overnight again at 105 o

C, and then weighed. This allowed an estimate of 

grams of ashed sediment minus water of hydration. The organic matter (OM) content was calculated as 

the difference between the dried sediment weight and this adjusted ashed weight. The percent OM was 

calculated as: 

 

 grams OM ÷ grams dry sediment x 100 (8) 

The percent TOC was calculated as percent OM x 0.58, following recommendations of Schumacher 

(2002). The percent TOC of organic matter varies between 40 and 58 percent depending on soil 

composition. 

Quality Assurance 

Samples were processed through the preparative and analytical flow scheme in 14 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 the samples and quality-control samples 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 determination included a reference solution, duplicates, and replicates. 

Quality control for sediment PSA included duplicates and replicates, and sediment TOC included replicates 

and spikes. 

Results

Total Selenium: Total selenium concentrations in unfiltered water samples (μg/L) for the 

October 2006 samples are listed in table 1; data for the January 2007 samples are listed in table 2. 

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 2006 sampling are presented in table 3. The 

dissolved organic selenium fraction is assumed to include Se(-II+0), consisting of seleno-amino acids 

and dissolved peptides, Se(0) as a pseudo-dissolved microcolloid, and inorganic Se(-II) species (Cutter, 

1984). 

Total Suspended Solids: Total suspended solids concentrations in unfiltered water (mg/L) 

collected during the October 2006 and January 2007 samplings are presented in table 4. 

Biota: Percent moisture and concentrations of selenium (μg/g dry weight) in biota (algae, 

plankton, midge larvae, western mosquitofish and sailfin molly) are presented in table 5.

6 
Detritus and Sediment: Percent moisture and selenium concentrations (μg/g dry weight) in 

detritus and sediment are presented in table 6. The particle size analyses of sediments, expressed as 

percent sand, silt, and clay, are presented in table 7. The percent total organic carbon in sediments is 

given in table 8. 

Quality Control Results 

Calibration Verification: During the selenium determinations, a calibration verification solution 

(Spex Claritas PPT®; cat #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 (4 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) 1640 Trace Elements in Natural Water (n=6) ranged from 101 to 114 

percent. Recoveries of selenium from NIST SRM 2704 Buffalo River Sediment (n=1) and National 

Research Council Canada (NRCC) SRM PACS-1 Marine Sediment (n=1) were 103 and 100 percent. 

The International Atomic Energy Agency (IAEA) Copepod Reference Material MA-A-1 (n= 4) and the 

Institute for Reference Materials and Measurements Certified Reference Material (CRM) 414 Trace 

Elements in Plankton (n=6) exhibited selenium recoveries ranging from 100 to 101 percent. Recoveries 

of selenium in NRCC CRM DORM-2 Dogfish Muscle (n=2) and IAEA CRM 407 Whole-body Fish 

(n=2) ranged from 100 to 111 percent. Recoveries of TSS from a TSS reference solution 

(Environmental Resource Associates Hardness Wastewater Standard 507) (n=2) were 100 percent. 

Analytical and Method Precision: Instrumental precision for selenium determined by repeated 

analysis of a standard throughout the run for each block (n=14) was less than 4 percent relative standard 

deviation (RSD). Relative percent differences between field duplicates (n=76) of unfiltered and filtered 

water samples analyzed for selenium or selenium species ranged from 0.1 to 26. A single field 

duplicate of a midge larvae sample produced a relative percent difference (RPD) of 0.1 and duplicates 

of filtered particulates ranged from 8.3 to 114 RPD. Relative percent differences for field duplicates of 

sediment for PSA were <9 RPD for the three fractions. Relative standard deviations for triplicate field 

samples of detritus (n=7), algae (n=6), midge larvae (n=6), and whole-body fish (n=6) analyzed for 

selenium were as follows: algae, 0.8 to 6.2 percent; detritus, 2.8 to 33 percent; midge larvae, 6.4 to 18 

percent; whole-body fish, 2.1 to 19 percent; and plankton, 3.5 to 43 percent. Laboratory method 

precision for triplicate (n=16) preparation and analysis of samples for selenium were less than or equal 

(≤) 5 percent RSD. Laboratory method precision for TSS determined by duplicate analysis of water 

samples (n=5) resulted in RPDs <8, whereas triplicate analysis for TSS (n=4) resulted in RSDs <9 

percent. Triplicate analyses of a sediment and sediment control material for PSA resulted in RSDs ≤12 

percent for the fractions. Triplicate analysis of a sediment sample, control sediment, spiked control 

sediment, and a control material for TOC resulted in RSDs <8 percent. 

Spikes: Recoveries of selenium [Se+4, selenate (Se+6), or selenomethionine] spiked into filter 

blanks (n=2) and water samples (n=21) ranged from 99 to 114 percent, and averaged 109 percent. 

Recoveries of selenium spiked into sediment (n=2), detritus (n=2), and biota (n=10) ranged from 91 to 

132 percent, and averaged 109 percent. Spikes (n=3) of sucrose on a control sediment analyzed for 

TOC resulted in recoveries of 107 and 108 percent. Recoveries of selenium spikes added to water 

during analysis (n=18) ranged from 105 to 116 percent, and averaged 110 percent; analysis spikes of 

sediment (n=2), filtered particulates (n=2), detritus (n=2), and biota (n=13) ranged from 102 to 113 

percent, and averaged 108 percent. 

7 
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. All BECs 

were below their respective method detection limits. 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: FIHGAAS 

instrument detection limits for selenium were 0.054 and 0.056 μg/L and 0.08 mg/L for TSS. Method 

detection limits (MDL) for each matrix for selenium were computed as: 

 

 3 x (SDb

2

 + SDs

2

)

1/2 (9) 

where 

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

SDs = standard deviation of a low level sample or spiked sample (n=3). 

The results were water, 0.11 to 0.39 μg/L; filtered particulates, 0.007 μg/L; sediment, 0.024 μg/g dry 

weight; algae and midge larvae, 0.015 to 0.019 μg/g dry weight; plankton, 0.010 μg/g dry weight; 

detritus, 0.011 μg/g dry weight; and whole-body fish, 0.014 μg/g dry weight. Method quantitation 

limits (MQLs) for each matrix were calculated as 3.3 x MDLs. Method detection limits for TSS were 

0.73 and 1.54 mg/L and MQLs were 2.42 and 5.07 mg/L. All quality control results for the study were 

within acceptable limits as specified by USGS-CERC. 

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 of Testing and Materials, 2003a, 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. 

American Society of Testing and Materials, 2003b, Standard test methods for moisture, ash, and organic 

matter of peat and other organic soils, D2974-00, in Annual Book of ASTM Standards, v. 04.08: West 

Conshohocken, Pa.., American Society for Testing and Materials, p. 330–333. 

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

Limnology and Oceanography, v. 29, no. 6, p. 1179–1192. 

Schumacher, B.A., 2002, Methods for the determination of total organic carbon (TOC) in soils and 

sediments: U.S. Environmental Protection Agency, Ecological Risk Assessment Support Center, 

Office of Research and Development, NCEA-C-1282, EMASC, 001, 25 p., available at URL 

http://www.epa.gov/esd/cmb/research/papers/bs116.pdf

8 
Table 1. Total selenium concentrations in duplicates of unfiltered irrigation drain water samples, Salton Sea, California,

October 2006.

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

nc, not collected]

Rep 1 Rep 2 Mean

 (μg/L) (μg/L) (μg/L)

38156 BLANK-1 --- 10/19/06 < 0.22 --- --- ---

38157 BLANK-2 --- 10/19/06 < 0.22 --- --- ---

38102, 38103 LKLNWATSE Lack & Lindsey Pond 10/13/06 2.23 2.12 2.18 0.08

38134, 38135 NLD1WATSE Niland 1 10/16/06 1.71 1.82 1.76 0.07

38136, 38137 NLD2WATSE Niland 2 10/16/06 2.85 2.86 2.86 0.01

38138, 38139 NLD3WATSE Niland 3 10/16/06 2.24 2.32 2.28 0.06

38140, 38141 NLD4WATSE Niland 4 10/16/06 3.13 3.11 3.12 0.01

nc1 OOOOWATSE O --- --- --- --- ---

38142, 38143 PPPPWATSE P 10/17/06 2.49 2.51 2.50 0.02

nc1 POEDWATSE Poe Rd --- --- --- --- ---

38108, 38109 PUMCWATSE Pumice 10/13/06 6.54 6.71 6.62 0.12

38144, 38145 QQQQWATSE Q 10/17/06 7.93 7.91 7.92 0.02

38146, 38147 RRRRWATSE R 10/17/06 2.35 1.94 2.14 0.29

38148, 38149 SSSSWATSE S 10/17/06 1.13 1.11 1.12 0.02

38114, 38115 SFWHWATSE San Felipe Wash 10/12/06 2.94 2.65 2.80 0.21

nc1 TTTTWATSE T --- --- --- --- ---

38096, 38097 TR01WATSE Trifolium 1 10/13/06 9.08 8.92 9.00 0.11

38100, 38101 TR12WATSE Trifolium 12 10/13/06 8.77 9.27 9.02 0.35

38088, 38089 TR13WATSE Trifolium 13 10/13/06 4.05 4.06 4.06 0.00

nc1 TR14WATSE Trifolium 14 --- --- --- --- ---

nc1 TR18WATSE Trifolium 18 --- --- --- --- ---

38104, 38105 TR19WATSE Trifolium 19 10/13/06 1.48 1.49 1.49 0.01

38110, 38111 FT20WATSE Former Trifolium 20 10/12/06 5.00 5.14 5.07 0.10

nc1 TR20WATSE Trifolium 20 --- --- --- --- ---

38112, 38113 TR22WATSE Trifolium 22 10/12/06 11.4 11.6 11.5 0.16

38116, 38117 TR23WATSE Trifolium 23 10/12/06 6.59 6.49 6.54 0.07

38098, 38099 TRSTWATSE Trifolium Storm 10/13/06 3.62 3.81 3.72 0.13

38150, 38151 UUUUWATSE U 10/17/06 2.16 2.16 2.16 0.00

38154, 38155 VLO5WATSE Vail 5 10/17/06 6.31 5.43 5.87 0.62

38152, 38153 WWWWWATSE W 10/17/06 2.79 2.31 2.55 0.34

nc1 ZSPLWATSE Z Spill --- --- --- --- --- 1

Drain was one of seven selected for intensive sampling (see table 3).

SD

Total selenium concentration

USGS ID number Field ID Drain Collection date

9
Table 2. Total selenium concentrations in duplicates of unfiltered irrigation drain water samples, Salton Sea, California, January 2007.

[USGS, U.S. Geological Survey; ID, identification; Rep, field replicate; μg/L, micrograms per gram; SD, standard deviation; <, less than; ---, no data; bold italicized 

values are greater than method detection limit, but less than method quantitation limit; these values have high uncertainty and are presented for information purposes only]

Rep 1 Rep 2 Mean

(μg/L) (μg/L) (μg/L)

38759, 38760 BLNKWATSE07 Blank 01/09/07 < 0.11 < 0.11 --- ---

38757 BLNDWATSE07 Unknown Blind 01/05/07 5.96 --- --- ---

38758 BLNDWATSE07 Unknown Blind 01/05/07 9.18 --- --- ---

38755, 38756 LKLNWATSE Lack & Lindsey Pond 01/07/07 4.04 3.69 3.87 0.24

38699, 38700 NLD1WATSE Niland 1 01/06/07 1.41 1.47 1.44 0.04

38701, 38702 NLD2WATSE Niland 2 01/06/07 2.58 2.53 2.56 0.04

38703, 38704 NLD3WATSE Niland 3 01/06/07 1.66 1.97 1.82 0.22

38705, 38706 NLD4WATSE Niland 4 01/06/07 2.07 1.95 2.01 0.08

38723, 38724 OOOOWATSE O 01/06/07 6.12 6.44 6.28 0.22

38721, 38722 PPPPWATSE P 01/06/07 4.34 5.62 4.98 0.91

38739, 38740 POEDWATSE Poe Rd 01/05/07 9.73 9.20 9.46 0.38

38725, 38726 PUMCWATSE Pumice 01/06/07 6.98 7.31 7.14 0.24

38719, 38720 QQQQWATSE Q 01/07/07 11.3 11.6 11.4 0.22

38717, 38718 RRRRWATSE R 01/07/07 2.31 2.90 2.60 0.42

38715, 38716 SSSSWATSE S 01/07/07 1.35 1.35 1.35 0.00

38733, 38734 SFWHWATSE San Felipe Wash 01/04/07 2.63 2.64 2.64 0.00

38713, 38714 TTTTWATSE T 01/07/07 1.18 0.97 1.07 0.15

38749, 38750 TR01WATSE Trifolium 1 01/05/07 4.33 4.38 4.36 0.03

38753, 38754 TR12WATSE Trifolium 12 01/07/07 7.43 7.29 7.36 0.10

38745, 38746 TR13WATSE Trifolium 13 01/05/07 5.29 5.35 5.32 0.05

38747, 38748 TR14WATSE Trifolium 14 01/05/07 2.91 3.01 2.96 0.06

38737, 38738 TR18WATSE Trifolium 18 01/05/07 42.7 43.3 43.0 0.43

38741, 38742 TR19WATSE Trifolium 19 01/04/07 1.96 1.72 1.84 0.17

38729, 38730 FT20WATSE Former Trifolium 20 01/04/07 5.41 4.68 5.05 0.52

38743, 38744 TR20WATSE Trifolium 20 01/04/07 5.33 5.53 5.43 0.14

38731, 38732 TR22WATSE Trifolium 22 01/04/07 4.32 4.29 4.30 0.02

38735, 38736 TR23WATSE Trifolium 23 01/04/07 3.98 4.29 4.13 0.22

38751, 38752 TRSTWATSE Trifolium Storm 01/05/07 18.0 18.7 18.3 0.51

38711, 38712 UUUUWATSE U 01/07/07 1.12 1.24 1.18 0.09

38727, 38728 VLO5WATSE Vail 5 01/06/07 5.84 5.93 5.89 0.07

38709, 38710 WWWWWATSE W 01/07/07 2.33 2.46 2.40 0.09

38707, 38708 ZSPLWATSE Z Spill 01/06/07 3.50 3.73 3.61 0.17

SD

Total selenium concentration

USGS ID number Field ID Drain Collection date

10
Table 3. Total dissolved selenium, dissolved selenium species, and particulate selenium concentrations in filtered irrigation drain water 

samples, Salton Sea, October 2006. 

[USGS, U.S. Geological Survey; ID, identification; Rep, replicate; [Se0 3]

-2, selenite; [Se04]-2, selenate; Se, selenium; μg/L, micrograms per liter; ---, no data; <, less than; 

bold italicized values are greater than method quantification limit, but less than method detection limit; these values have high uncertainty and are presented for information 

purposes only] 

(μg/L) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L)

38118 BLANK-1 --- 1 10/15/06 < 0.17 < 0.32 --- < 0.39 < 0.007 ---

38119 BLANK-2 --- 2 10/15/06 < 0.17 < 0.32 --- < 0.39 < 0.007 ---

38160 OOOOWATSE O 1 10/17/06 1.01 2.40 0.36 3.76 0.34 4.10

38161 OOOOWATSE O 2 10/17/06 0.78 2.26 0.51 3.55 0.25 3.81

38094 POEDWATSE Poe Rd 1 10/11/06 1.77 17.8 1.98 21.5 0.046 21.6

38095 POEDWATSE Poe Rd 2 10/11/06 2.01 17.7 1.50 21.3 0.043 21.3

38162 TTTTWATSE T 1 10/17/06 < 0.17 0.44 0.42 0.91 0.014 0.93

38163 TTTTWATSE T 2 10/17/06 < 0.17 < 0.32 0.72 0.89 0.019 0.91

38090 TR14WATSE Trifolium 14 1 10/13/06 0.48 5.49 0.10 6.07 0.055 6.12

38091 TR14WATSE Trifolium 14 2 10/13/06 0.50 5.25 0.50 6.25 0.076 6.32

38092 TR18WATSE Trifolium 18 1 10/12/06 1.34 16.3 0.99 18.6 0.12 18.7

38093 TR18WATSE Trifolium 18 2 10/12/06 1.49 16.0 2.17 19.7 0.45 20.1

38106 TR20WATSE Trifolium 20 1 10/13/06 0.67 4.09 0.28 5.03 0.062 5.10

38107 TR20WATSE Trifolium 20 2 10/13/06 0.58 3.92 0.51 5.01 0.088 5.09

38158 ZSPLWATSE Z Spill 1 10/16/06 0.70 3.48 0.68 4.86 0.051 4.91

38159 ZSPLWATSE Z Spill 2 10/16/06 0.74 3.45 0.57 4.76 0.056 4.81 1

Calculated dissolved [Se04]

-2 = measured ([Se04]-2 + [Se03]-2) - measured [Se03]-2 

2

Calculated dissolved Organic Se = measured total dissolved Se - measured ([Se0 4]

-2 + [Se03]-2) 3

Measured particulate Se = μg of Se in filtered particulates divided by volume of site water filtered

4

Calculated total Se = measured particulate Se + measured total dissolved Se

4

Calculated 

total Se

1

Calculated 

dissolved 

[Se04]

-2

Measured 

total 

dissolved Se 

2

Calculated 

dissolved 

organic Se

Dissolved 

[Se03]

-2 Field ID

3

Measured 

particulate 

Se

USGS ID 

number Drain Rep number

Collection 

date

11
Table 4. Total suspended solids concentrations in unfiltered Salton Sea irrigation drain water samples, October 2006 

and January 2007.

[ID, identification; USGS, U.S. Geological Survey; TSS, total suspended solids; mg/L, milligram per liter]

USGS ID TSS USGS ID TSS

number (mg/L) number (mg/L)

LKLNWATSS Lack & Lindsey Pond 38086 47.9 38697 23.6

NLD1WATSS Niland 1 38120 62.9 38669 73.0

NLD2WATSS Niland 2 38121 128. 38670 88.0

NLD3WATSS Niland 3 38122 98.3 38671 51.5

NLD4WATSS Niland 4 38123 30.7 38672 37.2

OOOOWATSS O 38132 933. 38681 40.0

PPPPWATSS P 38131 93.7 38680 41.8

POEDWATSS Poe Rd 38078 10.8 38689 5.89

PUMCWATSS Pumice 38087 156. 38682 167.

QQQQWATSS Q 38130 52.5 38679 52.8

RRRRWATSS R 38129 169. 38678 148.

SSSSWATSS S 38128 96.7 38677 57.5

SFWHWATSS San Felipe Wash 38075 68.6 38686 14.9

TTTTWATSS T 38127 40.4 38676 35.3

TR01WATSS Trifolium 1 38083 107. 38694 27.3

TR12WATSS Trifolium 12 38085 162. 38696 44.6

TR13WATSS Trifolium 13 38081 46.8 38692 101.

TR14WATSS Trifolium 14 38082 57.8 38693 105.

TR18WATSS Trifolium 18 38077 22.2 38688 14.2

TR19WATSS Trifolium 19 38079 6.45 38690 27.3

FT20WATSS Former Trifolium 20 38073 16.0 38684 9.04

TR20WATSS Trifolium 20 38080 48.1 38691 28.0

TR22WATSS Trifolium 22 38074 27.9 38685 21.5

TR23WATSS Trifolium 23 38076 23.8 38687 14.6

TRSTWATSS Trifolium Storm 38084 82.5 38695 12.5

UUUUWATSS U 38126 70.3 38675 64.9

VLO5WATSS Vail 5 38133 161. 38683 338.

WWWWWATSS W 38125 169. 38674 95.8

ZSPLWATSS Z Spill 38124 69.5 38673 61.6

BLNDWATSS07 --- --- --- 38698 162.

October, 2006 January, 2007

Field ID Drain

12
Table 5. Selenium concentrations in biota samples collected from Salton Sea irrigation drains, October 2006. 

[USGS, U.S. Geological Survey; ID, identification; μg/g, microgram per gram; ---, no data]

USGS ID Moisture Selenium

Number (percent) (μg/g dry weight)

38290 OOOOALGTSE06A 10/18, 10/20, 10/23/06 algae O 51.0 2.40

38291 OOOOALGTSE06B 10/18, 10/20, 10/23/06 algae O 50.3 2.30

38292 OOOOALGTSE06C 10/18, 10/20, 10/23/06 algae O 51.9 2.39

38287 POEDALGTSE06A 10/12/06 algae Poe 53.3 2.95

38288 POEDALGTSE06B 10/12/06 algae Poe 54.3 2.99

38289 POEDALGTSE06C 10/12/06 algae Poe 52.8 2.95

38281 TTTTALGTSE06A 10/19/06 algae T 62.5 2.15

38282 TTTTALGTSE06B 10/19/06 algae T 61.8 2.14

38283 TTTTALGTSE06C 10/19/06 algae T 62.9 2.39

38293 TR14ALGTSE06A 10/14/06 algae Trifolium 14 58.7 2.41

38294 TR14ALGTSE06B 10/14/06 algae Trifolium 14 59.0 2.46

38295 TR14ALGTSE06C 10/14/06 algae Trifolium 14 59.4 2.31

38298 TR18ALGTSE06A 10/13, 10/16/06 algae Trifolium 18 62.6 7.06

38299 TR18ALGTSE06B 10/13, 10/16/06 algae Trifolium 18 63.8 7.50

38300 TR18ALGTSE06C 10/13, 10/16/06 algae Trifolium 18 59.8 7.10

38284 TR20ALGTSE06A 10/11, 10/15/06 algae Trifolium 20 45.7 3.00

38285 TR20ALGTSE06B 10/11, 10/15/06 algae Trifolium 20 46.4 3.13

38286 TR20ALGTSE06C 10/11, 10/15/06 algae Trifolium 20 47.1 3.17

38296 ZSPLALGTSE06A 10/22, 10/24/06 algae Z Spill 63.6 1.57

38297 ZSPLALGTSE06B 10/22, 10/24/06 algae Z Spill 60.1 1.72

38351 OOOONPTSE06A 10/20/06 plankton O --- 1.99

38352 OOOONPTSE06B 10/20/06 plankton O --- 3.51

38353 OOOONPTSE06C 10/20/06 plankton O --- 1.99

38348 POEDNPTSE06A 10/12/06 plankton Poe --- 4.51

38349 POEDNPTSE06B 10/12/06 plankton Poe --- 2.94

38350 POEDNPTSE06C 10/12/06 plankton Poe --- 3.21

38342 TTTTNPTSE06A 10/19/06 plankton T --- 3.70

38343 TTTTNPTSE06B 10/19/06 plankton T --- 2.92

38344 TTTTNPTSE06C 10/19/06 plankton T --- 3.51

38354 TR14NPTSE06A 10/14/06 plankton Trifolium 14 --- 2.89

38355 TR14NPTSE06B 10/14/06 plankton Trifolium 14 --- 3.01

38356 TR14NPTSE06C 10/14/06 plankton Trifolium 14 --- 2.81

38360 TR18NPTSE06A 10/13/06 plankton Trifolium 18 --- 3.60

38361 TR18NPTSE06B 10/13/06 plankton Trifolium 18 --- 8.08

38362 TR18NPTSE06C 10/13/06 plankton Trifolium 18 --- 4.61

38345 TR20NPTSE06A 10/15/06 plankton Trifolium 20 --- 3.52

38346 TR20NPTSE06B 10/15/06 plankton Trifolium 20 --- 3.43

38347 TR20NPTSE06C 10/15/06 plankton Trifolium 20 --- 2.90

38357 ZSPLNPTSE06A 10/22/06 plankton Z Spill --- 1.97

38358 ZSPLNPTSE06B 10/22/06 plankton Z Spill --- 2.22

38359 ZSPLNPTSE06C 10/22/06 plankton Z Spill --- 2.45

38310 OOOOCHITSE06A 10/18, 10/20, 10/23/06 midge O 61.8 3.93

38311 OOOOCHITSE06B 10/18, 10/20, 10/23/06 midge O 60.1 3.64

38307 POEDCHITSE06A 10/12, 10/21/06 midge Poe 54.5 6.42

38308 POEDCHITSE06B 10/12, 10/21/06 midge Poe 52.8 5.40

38309 POEDCHITSE06C 10/12, 10/21/06 midge Poe 52.8 5.21

38301 TTTTCHITSE06A 10/19/06 midge T 77.6 6.37

38302 TTTTCHITSE06B 10/19/06 midge T 77.4 5.79

38303 TTTTCHITSE06C 10/19/06 midge T 75.9 5.65

Field ID Collection date Matrix Drain

13
Table 5. Selenium concentrations in biota samples collected from Salton Sea irrigation drains, October 2006.—Continued

[USGS, U.S. Geological Survey; ID, identification; μg/g, microgram per gram] — Continued

USGS ID Moisture Selenium

Number (percent) (μg/g dry weight)

38312 TR14CHITSE06A 10/14/06 midge Trifolium 14 78.9 5.35

38313 TR14CHITSE06B 10/14/06 midge Trifolium 14 73.0 4.64

38314 TR14CHITSE06C 10/14/06 midge Trifolium 14 76.8 4.46

38318 TR18CHITSE06A 10/13, 10/16/06 midge Trifolium 18 78.6 24.0

38319 TR18CHITSE06B 10/13, 10/16/06 midge Trifolium 18 77.7 22.5

38320 TR18CHITSE06C 10/13, 10/16/06 midge Trifolium 18 73.0 20.8

38304 TR20CHITSE06A 10/11, 10/15/06 midge Trifolium 20 73.7 9.42

38305 TR20CHITSE06B 10/11, 10/15/06 midge Trifolium 20 73.5 8.78

38306 TR20CHITSE06C 10/11, 10/15/06 midge Trifolium 20 70.8 6.60

38315 ZSPLCHITSE06A 10/17, 10/22, 10/24/06 midge Z Spill 67.2 3.68

38316 ZSPLCHITSE06B 10/17, 10/22, 10/24/06 midge Z Spill 67.4 2.95

38317 ZSPLCHITSE06C 10/17, 10/22, 10/24/06 midge Z Spill 69.6 4.29

38257 OOOOGMBTSE06A 10/18/06 mosquitofish O 77.4 7.54

38258 OOOOGMBTSE06B 10/18/06 mosquitofish O 77.6 7.09

38259 OOOOGMBTSE06C 10/18/06 mosquitofish O 77.8 6.95

38260 OOOOSLMTSE06A 10/18/06 sailfin molly O 76.0 5.01

38261 OOOOSLMTSE06B 10/18/06 sailfin molly O 76.5 5.16

38262 OOOOSLMTSE06C 10/20/06 sailfin molly O 76.8 4.84

38251 POEDGMBTSE06A 10/12/06 mosquitofish Poe 77.7 10.5

38252 POEDGMBTSE06B 10/12/06 mosquitofish Poe 79.1 10.3

38253 POEDGMBTSE06C 10/12/06 mosquitofish Poe 79.0 9.16

38254 POEDSLMTSE06A 10/12/06 sailfin molly Poe 78.7 19.1

38255 POEDSLMTSE06B 10/12/06 sailfin molly Poe 78.3 18.1

38256 POEDSLMTSE06C 10/12/06 sailfin molly Poe 78.7 21.6

38239 TTTTGMBTSE06A 10/19/06 mosquitofish T 78.1 6.54

38240 TTTTGMBTSE06B 10/19/06 mosquitofish T 77.4 6.56

38241 TTTTGMBTSE06C 10/19/06 mosquitofish T 76.7 7.22

38242 TTTTSLMTSE06A 10/19/06 sailfin molly T 76.5 6.21

38243 TTTTSLMTSE06B 10/19/06 sailfin molly T 78.2 5.62

38244 TTTTSLMTSE06C 10/19/06 sailfin molly T 77.9 4.64

38263 TR14GMBTSE06A 10/14/06 mosquitofish Trifolium 14 79.8 5.81

38264 TR14GMBTSE06B 10/14/06 mosquitofish Trifolium 14 80.0 5.24

38265 TR14GMBTSE06C 10/14/06 mosquitofish Trifolium 14 81.2 4.49

38266 TR14SLMTSE06A 10/14/06 sailfin molly Trifolium 14 78.1 4.51

38267 TR14SLMTSE06B 10/14/06 sailfin molly Trifolium 14 77.8 4.65

38268 TR14SLMTSE06C 10/14/06 sailfin molly Trifolium 14 78.7 4.70

38275 TR18GMBTSE06A 10/13/06 mosquitofish Trifolium 18 78.6 14.3

38276 TR18GMBTSE06B 10/13/06 mosquitofish Trifolium 18 78.5 13.8

38277 TR18GMBTSE06C 10/13/06 mosquitofish Trifolium 18 78.1 14.5

38278 TR18SLMTSE06A 10/13/06 sailfin molly Trifolium 18 79.9 21.2

38279 TR18SLMTSE06B 10/13/06 sailfin molly Trifolium 18 81.5 28.7

38280 TR18SLMTSE06C 10/13/06 sailfin molly Trifolium 18 79.3 20.7

38245 TR20GMBTSE06A 10/11/06 mosquitofish Trifolium 20 78.1 4.69

38246 TR20GMBTSE06B 10/11/06 mosquitofish Trifolium 20 79.4 5.03

38247 TR20GMBTSE06C 10/11/06 mosquitofish Trifolium 20 78.8 4.74

38248 TR20SLMTSE06A 10/11/06 sailfin molly Trifolium 20 79.1 16.0

38249 TR20SLMTSE06B 10/11/06 sailfin molly Trifolium 20 79.8 15.5

38250 TR20SLMTSE06C 10/11, 10/15/06 sailfin molly Trifolium 20 79.9 14.6

Field ID Collection date Matrix Drain

14
Table 5. Selenium concentrations in biota samples collected from Salton Sea irrigation drains, October 2006.—Continued 

[USGS, U.S. Geological Survey; ID, identification; μg/g, microgram per gram] —Continued

USGS ID Moisture Selenium

Number (percent) (μg/g dry weight)

38269 ZSPLGMBTSE06A 10/17/06 mosquitofish Z Spill 78.7 6.43

38270 ZSPLGMBTSE06B 10/17, 10/22/06 mosquitofish Z Spill 78.3 6.23

38271 ZSPLGMBTSE06C 10/22/06 mosquitofish Z Spill 79.9 7.48

38272 ZSPLSLMTSE06A 10/17, 10/22/06 sailfin molly Z Spill 77.4 4.27

38273 ZSPLSLMTSE06B 10/22/06 sailfin molly Z Spill 75.0 4.72

38274 ZSPLSLMTSE06C 10/22/06 sailfin molly Z Spill 77.3 5.01

Field ID Collection date Matrix Drain

15
Table 6. Selenium concentrations in detritus and sediment samples collected from Salton Sea irrigation drains, October 2006.

[USGS, U.S. Geological Survey; ID, identification; μg/g, micrograms per gram]

USGS ID Moisture Selenium

Number (percent) (μg/g dry weight)

38330 OOOODETTSE06A 10/18/06 detritus O 70.0 6.65

38331 OOOODETTSE06B 10/18/06 detritus O 70.7 7.40

38332 OOOODETTSE06C 10/18/06 detritus O 72.5 9.91

38327 POEDDETTSE06A 10/21/06 detritus Poe 75.9 9.77

38328 POEDDETTSE06B 10/21/06 detritus Poe 80.1 10.1

38329 POEDDETTSE06C 10/21/06 detritus Poe 80.5 10.3

38321 TTTTDETTSE06A 10/19/06 detritus T 75.6 2.07

38322 TTTTDETTSE06B 10/19/06 detritus T 80.9 1.89

38323 TTTTDETTSE06C 10/19/06 detritus T 79.6 1.74

38333 TR14DETTSE06A 10/14/06 detritus Trifolium 14 73.7 3.88

38334 TR14DETTSE06B 10/14/06 detritus Trifolium 14 73.0 2.63

38335 TR14DETTSE06C 10/14/06 detritus Trifolium 14 71.9 5.24

38339 TR18DETTSE06A 10/13, 10/16/06 detritus Trifolium 18 80.6 14.9

38340 TR18DETTSE06B 10/13, 10/16/06 detritus Trifolium 18 77.3 17.0

38341 TR18DETTSE06C 10/13, 10/16/06 detritus Trifolium 18 79.0 15.2

38324 TR20DETTSE06A 10/15/06 detritus Trifolium 20 80.3 4.59

38325 TR20DETTSE06B 10/15/06 detritus Trifolium 20 85.5 5.94

38326 TR20DETTSE06C 10/15/06 detritus Trifolium 20 79.7 4.97

38336 ZSPLDETTSE06A 10/17, 10/22/06 detritus Z Spill 75.9 3.95

38337 ZSPLDETTSE06B 10/17, 10/22/06 detritus Z Spill 77.7 2.52

38338 ZSPLDETTSE06C 10/17, 10/22/06 detritus Z Spill 76.9 3.54

38182 OOOOSDTSE06 10/17/06 sediment O 49.5 1.02

38179 POEDSDTSE06 10/11/06 sediment Poe Rd 24.6 0.62

38183 TTTTSDTSE06 10/17/06 sediment T 56.8 1.11

38181 TR14SDTSE06 10/13/06 sediment Trifolium 14 43.1 1.91

38180 TR18SDTSE06 10/12/06 sediment Trifolium 18 63.5 4.67

38178 TR20SDTSE06 10/11/06 sediment Trifolium 20 50.2 1.64

38184 ZSPLSDTSE06 10/16/06 sediment Z Spill 69.9 2.23

Field ID Collection date Matrix Drain

16
Table 7. Particle size distributions in sediment samples collected from Salton Sea irrigation drains, October 2006.

[USGS, U.S. Geological Survey; ID, identification; >, greater than; mm, millimeter]

> 2 mm Sand Silt Clay

(percent) (percent) (percent) (percent)

38189 OOOOSDTOC06 O 1.43 33.6 27.5 37.5

38186 POEDSDTOC06 Poe Rd 2.29 65.8 23.2 8.74

38190 TTTTTSDTOC06 T 0.16 14.3 33.9 51.6

38188 TR14SDTOC06 Trifolium 14 10.2 23.4 35.0 31.4

38187 TR18SDTOC06 Trifolium 18 0.04 50.4 34.5 15.1

38185 TR20SDTOC06 Trifolium 20 8.69 28.0 53.5 9.86

38191 ZSPLSDTOC06 Z Spill 0.40 26.1 48.6 24.8

Particle size category USGS ID 

number Field ID Drain

17
Table 8. Total organic carbon in sediment samples collected from Salton Sea 

irrigation drains, October 2006. 

[USGS, U.S. Geological Survey; ID, identification; estimated total organic carbon based on 58 percent 

organic matter loss on ignition] 

USGS ID Total organic carbon 

number (percent)

38189 OOOOSDTOC06 O 2.17

38186 POEDSDTOC06 Poe Rd 1.12

38190 TTTTTSDTOC06 T 2.34

38188 TR14SDTOC06 Trifolium 14 2.46

38187 TR18SDTOC06 Trifolium 18 3.98

38185 TR20SDTOC06 Trifolium 20 2.54

38191 ZSPLSDTOC06 Z Spill 5.47

Field ID Drain

18
For more information concerning the research described 

in this report, contact: 

U.S. Geological Survey 

Columbia Environmental Research Center 

4200 New Haven Road 

Columbia, MO 65201 

(573) 875-5399 

http://www.cerc.usgs.gov