Kesterson Reservoir Research Articles

Nonpoint sources

Nonpoint sources

Selenium in Kesterson Reservoir Ephemeral Pools Formed by Groundwater Rise: II. Laboratory Experiments

AbstractThe formation of seleniferous ephemeral pools that result from shallow water table rise through seleniferous soils was studied in laboratory columns of soils from Kesterson Reservoir, Merced County, California. Variables included in the column experiments included the depth interval of the soils, the rate of shallow water table rise and temperature. The columns were packed with either surface (0–0.15 m) soils (with and without the original salt crust), or subsurface soils (0.15–0.30 m) sampled from the southwest corner of Pond 1, Kesterson Reservoir. Controlled inputs of nonseleniferous, saline water through the bottoms of the columns provided water table rise rates of 3, 10 and 30 mm d−1. The soil columns were maintained at either room temperature (≈25°C) or 5°C. The amount of Se transported from the soils into the overlying ponding waters was proportional to the water‐extractable soil Se content, and was positively correlated with the rate of water table rise. The 5°C experiments resulted in greater Se transfers into the ponding waters in the columns subjected to 10 and 30 mm d−1 rates of water table rise (relative to comparable room temperature columns), while the reverse effect was observed with 3 mm d−1 columns.

Selenium in Kesterson Reservoir Ephemeral Pools Formed by Groundwater Rise: I. A Field Study

AbstractOne of the principal initial plans for managing Se contamination at Kesterson Reservoir (Merced County, California) entailed excavation to a depth of at least 0.15 m in order to remove soils with Se concentrations higher than 4 mg kg−1. Prior to implementing this plan, surface waters were collected from numerous shallow ephemeral pools that formed during the winters of 1986 to 1988. Elevated concentrations of Se were measured in all of these pools. Pools formed during this period from a combination of overland flow from adjacent nonseleniferous pond waters, rainfall ponding, and emergence of the fluctuating shallow water table above the soil surface. Selenium in these ephemeral pool waters originated primarily from dissolution of surface salt crusts and from displacement of seleniferous soil solutions up to the surface. Through the monitoring of a test plot where 0.30 m of the surface soil had been removed, the potential was demonstrated for shallow water table rise to displace seleniferous soil solutions to the surface, resulting in highly seleniferous ephemeral pools. In the test plot, ephemeral pool Se concentrations often exceeded 103µg L−1. This study clearly demonstrated (i) that pools formed over soils with total Se concentrations in the range of 0.5 to 1.7 mg kg−1 could still provide a highly seleniferous aquatic environment, (ii) that the total Se concentration in a soil can be a misleading parameter to use in determining target goals for remediation, and (iii) that the excavation strategy was inappropriate for the Kesterson Reservoir setting.

Selenium detoxification in wetlands by permanent flooding: I. Effects on a macroalga, an epiphytic herbivore, and an invertebrate predator in the long-term mesocosm experiment at Kesterson Reservoir, California

Storage of Se-rich agricultural drainwater in an inland saline marsh (Kesterson Reservoir) resulted in heavily contaminated biota (100 to 300 ppm Se as dw). A hypothesis was proposed that permanent flooding of the marsh with low-Se water (to create anoxic sediments) would immobilize Se in an insoluble fraction unavailable to aquatic biota. This was tested in a 0.4 ha mesocosm at Kesterson Reservoir over 2.3 yr by measuring the decline in Se in plants and animals. The study was part of a larger project, only data for soluble and particulate Se, in the submerged macroalga Chara, and in the aquatic and aerial forms of typical epifloral invertebrates — a herbivore (chironomid), and one of its predators (damselfly) are reported here. Permanent flooding resulted in biologically immobile Se. A rapid initial decline in Se lasting a few months was followed by a slower, irregular but persistent decrease. Soluble Se declined most quickly, followed by that in damselfly and chironomid populations. Declines in the vegetation were slowest but Se fell to a lower level (3 to 4 ppm) than in the animals (14 to 15 ppm), although Se levels were still dropping in all biota at the end of the experiment. Between 85 and 93% of initial Se was lost by the 3 types of organisms over 2.3 yr. There was little difference in loss rates between predator and herbivore. Because Chara was the most common submerged vegetation, its loss of 94% of initial Se to concentrations considered safe for wildlife, is most important to detoxification of the entire wetland.

Soil selenium fractionation, depth profiles and time trends in a vegetated site at Kesterson Reservoir

Kesterson Reservoir, in the San Joaquin Valley of California, was used for disposal of saline, seleniferous agricultural drain waters during the years 1981 - 1986. The combined effects of infrequent drain water application, reduction and oxidation of Se, and evapotranspirative removal of soil water within the upper 1 m of the soil profiles appear to provide explanations for distribution patterns of Se in soils of upland sites. From 1987 to 1990, an approximate doubling in average soil solution Se concentrations was observed. It is shown that currently only relatively insignificant quantities of Se have been transported into the Pond 11 soils from the shallow water table. Sequential extraction of these upland soils indicated that substantial inventories of Se were associated with soluble, adsorbed, carbonate, and soil organic matter fractions, while Se retained within refractory inorganic fractions were minor. The mobilization of Se from these potentially labile pools may account for the observed increases in soil solution concentrations of Se following the draining of Kesterson Reservoir.

Groundwater contamination at the Kesterson Reservoir, California: 1. Hydrogeologic setting and conservative solute transport

Shallow groundwater under Kesterson Reservoir, Merced County, California, was contaminated over a period of 6 years while the reservoir was used for disposal of brackish subsurface agricultural drainage water from farmlands in the San Joaquin Valley. Drainage water contained an average of 10,000 mg/L total dissolved solids (TDS), high concentrations of selenium (300 μg/L), nitrate (37 mg/L as nitrogen), boron (15 mg/L), and lesser amounts of mercury, chromium, and molybdenum. Infiltration and lateral migration of this water created a 20‐m‐deep plume of high‐TDS, boron‐rich water covering an area of about 5 km2. Transport of selenium and nitrate was inhibited by biogeochemical reactions in the pond bottom sediments, so that migration of these two constituents into the aquifer was limited. This paper focuses on physical parameters affecting seepage and lateral migration of nonreactive solutes and on hydrogeological factors associated with selenium break‐through into the shallow aquifer. An accompanying paper describes biogeochemical processes that limit nitrate and selenium migration (White et al., this issue). The regional hydrogeologic system at Kesterson Reservoir is dominated by the presence of four lithostratigraphic units. These are, in order of increasing depth, a fine‐grained surfical layer extending to depths of as much as 8 m, a semiconfined sandy aquifer extending to 60 m, a widespread lacustrine clay confining layer, and a confined sandy aquifer. Within each of these units, order of magnitude variations in the hydrologic properties of the sediments occur ubiquitously over lateral distances of tens of meters and vertical distances of a fraction of a meter. Seepage rates from the ponds into the underlying aquifer are dominated by local hydrogeologic properties and thickness of the fine‐grained surface layer. Selenium migrated into the aquifer in an area where the fine‐grained surface layer was thin or absent. Once in the aquifer, local rates of migration are controlled by the small‐scale structure and hydrogeologic properties of the sediments. The aquifer is composed of a heterogeneous mixture of sands, silts, and clays. Individual sand beds, which average about 0.3 m thick, do not appear to extend over lateral distances of more than 30 m. The large range of velocities combined with a limited lateral extent of individual layers are expected to create a broadly dispersed plume of solutes migrating downgradient from Kesterson. A noninvasive electromagnetic survey of electrical conductivity distributions in the shallow aquifer appears to confirm this conceptual model for transport in the shallow aquifer.

Groundwater contamination at the Kesterson Reservoir, California: 2. Geochemical parameters influencing selenium mobility

Transport of selenium in groundwater at the Kesterson Reservoir in the Central Valley of California was strongly retarded because of chemical reduction and precipitation mediated by microbial activity. Under such conditions, negative correlations were documented between aqueous Se and Fe2+, Mn, and H2S. Locally, the presence of oxidizing species, notably O2 and NO3, suppressed this reduction, permitting Se mobilization in the shallow aquifer. Selenate, the dominant and most oxidized form of Se, was in electrochemical disequilibrium with subordinate concentrations of selenite. Normally slow inorganic reduction rates were accelerated by microbial activity which utilizes oxidized chemical species including selenate as electron donors during the oxidation of organic matter. Two stratified redox barriers to selenium migration were documented beneath Kesterson: an underlying shallow anoxic zone underlying most of the pond bottom, characterized by high organic content and sulfate reduction, and a deeper dynamic front established by localized O2 infiltration from the overlying ponds and Fe2+ release from aquifer materials. The reducing nature of this deeper aquifer ultimately precludes Se transport to regional groundwater.

Route‐dependent pharmacokinetics, distribution, and placental permeability of organic and inorganic selenium in hamsters

Inorganic selenium (Se) salts (selenite and selenate oxyanions) and the organic selenoamino acids (selenomethionine and seleniferous grains) are teratogenic and embryolethal in domestic and wild birds. Selenium bioaccumulation has been held responsible for reproductive failure among waterfowl at the Kesterson Reservoir (California), the Ouray and Stewart Lake Wildlife Refuges (Utah), and the Carson Sink (Nevada). Anecdotal field and controlled laboratory reports have implicated Se exposure in mammalian embryotoxicity (including human), but developmental toxicity studies in hamsters failed to demonstrate an adverse response, except at maternally toxic doses (Ferm et al., Reprod. Toxicol., in press). Uptake, distribution, and elimination of Se after a single bolus equimolar dose (60 mumol/kg) of selenate or selenomethionine by oral or intravenous administration were compared using day 8 pregnant hamsters. Intravenous selenate was eliminated ten times more rapidly from maternal plasma than oral selenate, but concentrated in liver, kidney, and placenta to the same degree. Intravenous (iv) L-selenomethionine achieved lower maximum circulating total [Se], but it was eliminated more slowly than iv selenate. Larger areas under the plasma and peripheral tissue [Se]:time curve (AUC) after oral or parenteral selenomethionine than after equimolar selenate were consistent with previous studies in rodents and in humans. Embryonic [Se] plateaued at 3 nmol/g after selenate, but embryonic [Se] after selenomethionine continued to accumulate (80 nmol/g) as gestation progressed. The lack of a teratogenic response in hamsters at doses of either selenate or selenomethionine less than those associated with maternal intoxication cannot be attributed to lack of Se accumulation in early embryonic and placental tissue.

Measurement and Interpretation of Low Levels of Dissolved Oxygen in Ground Water

AbstractA Rhodazine‐D colorimetric technique was adapted to measure low‐level dissolved oxygen concentrations in ground water. Prepared samples containing between 0 and 8.0 μmoles · 1‐1 dissolved oxygen in equilibrium with known gas mixtures produced linear spectrophotometric absorbance with a lower detection limit of 0.2 μmoles · 1‐1. Excellent reproducibility was found for solutions ranging in composition from deionized water to sea water with chemical interferences detected only for easily reduced metal species such as ferric ion, cupric ion, and hexavalent chromium. Such effects were correctable based on parallel reaction stoichiometries relative to oxygen. The technique, coupled with a downhole wire line tool, permitted low‐level monitoring of dissolved oxygen in wells at the selenium‐contaminated Kesterson Reservoir in California. Results indicated a close association between low but measurable dissolved oxygen concentrations and mobility of oxidized forms of selenium in the shallow aquifer which were in general electrochemical disequilibrium.

Selenium Immobilization in a Pond Sediment at Kesterson Reservoir

AbstractKesterson Reservoir, Merced County, CA, a disposal facility for agricultural drain water, became the object of intense scientific investigation following discovery in 1983 that Se‐laden agricultural drain water was having serious effects on the reproductive success of waterfowl. A remedial measure involving permanent flooding with low‐Se water, aimed at taking advantage of low Se solubility under reducing conditions, was proposed as a means of limiting Se movement into groundwater and biota. A field experiment was undertaken to evaluate the feasibility of the proposed remedial measure, its impact on the quality of shallow groundwater and for quantifying Se immobilization and transport through a newly flooded pond bottom soil. Extensive soil water and groundwater sampling demonstrated that although initial soluble Se concentrations in the top 1.22 m (4 ft) of soil typically ranged from approximately 1000 to 3000 µg L−1, Se concentrations declined dramatically after flooding and elevated concentrations below 1.22 m were observed at only one of five sampling sites. Analysis of the temporal and spatial changes in the distribution of dissolved Se and Cl− indicated that 66 to 108% of the initial soluble Se present in the top 1.22 m was immobilized shortly after flooding. These estimates were consistent with the low Se concentrations observed in shallow monitoring wells. The extent to which Se immobilization occurred correlated inversely with average pore water velocity. Data presented suggest that reducing conditions in the newly flooded soils lead to the microbially mediated transformation of selenate to less soluble or mobile forms.

Volatilization of selenium from agricultural evaporation pond sediments

Microbial volatilization of Se was evaluated as a means of detoxifying Se-contaminated sediments. Sediment samples containing 60.7 (Kesterson Reservoir) and 9.0 mg Se kg −1 (Peck ponds) were incubated for 273 days in closed systems located in the greenhouse. Volatile Se was collected from a continuous air-exchange stream using activated carbon. Various economical and readily available organic and inorganic amendments were tested for their capacity to enhance the microbial process, including Citrus (orange) peel, Vitis (grape) pomace, feedlot manure, barley straw, chitin, pectin, ZnSO 4, (NH 4) 2SO 4, and an inoculum of Acremonium falciforme (an active Se methylating fungus). With the Kesterson sediment, the highest Se removal (44.0%) resulted from the combined application of citrus peel and ZnSO 4, followed by citrus peel alone (39.6%), and citrus peel combined with ZnSO 4, (NH 4) 2SO 4 and A. falciforme (30.1%). Manure (19.5%), pectin (16.4%), chitin (9.8%) and straw plus N (8.8%) had less pronounced effects. Without the amendments, cumulative Se volatilization was 6.1% of the initial inventory. Grape pomace (3.0%) inhibited the process. With the Peck sediment, the highest amount of Se removed was observed with chitin (28.6%), manure (28.5%), and citrus peel alone (27.3%). Without amendments, 14.0% of the native Se was volatilized in 273 days. Cumulative Se volatilization was 24.7% with citrus plus Zn and N, 17.2% with citrus plus Zn, and 18.8% with citrus plus Zn, N and A. falciforme. Pectin (15.2%), straw plus N (16.4%), and grape pomace (7.3%) were among the less effective amendments for the Peck sediment. The differences in the effectiveness of each treatment between the two seleniferous soils may be a result of the residual N content of the sediments. With the Kesterson sediment, which was high in organic C and N, added N inhibited volatilization of Se, while with Peck sediments (low in organic C and N) N-rich materials tended to accelerate Se volatilization. Inoculation with A. falciforme did not enhance Se evolution from either sediment, indicating that there was a sufficient population of microflora capable of producing gaseous Se.

The effect of nitrate and organic matter upon mobility of selenium in groundwater and in a water treatment process

Kesterson Reservoir in Merced County, California was formerly used as a storage and evaporation facility for Se-contaminated agricultural drain water. Very little Se entered the shallow aquifer below the ponds with percolating pond water. With few localized exceptions, most of the Se was removed from the water and retained in the first decimeter of soil, which was rich in decaying organic matter. Where it was present in groundwater, Se was nearly always associated with nitrate. Nitrate induces mildly oxidizing conditions (Eh ≈ 350 mV) and inhibits microbial fixation of Se. In the absence of nitrate, relatively reducing conditions prevail in the groundwater (Eh ≈ -50 mV), and Se is quickly removed. Selenate follows oxygen and nitrate in the order that soil microbes utilize electron acceptors. The process of Se removal from water by soil was reproduced in the laboratory, and the effect of nitrate was confirmed. This natural process might be applied to water treatment for Se removal. The deep water ecosystem at Kesterson Reservoir was highly productive. Vegetation growing in water treatment ponds should supply enough organic matter to maintain anaerobic conditions in the sediment. This process, including algae culture, was operated in an outdoor 79 cm column for 100 days. At percolation rates of 15 and 30 m yr−1 Se removal averaged 94%, with an additional 2% converted to volatile compounds.

Vegetable Insect Control with Minimal Use of Insecticides

Large scale commercial vegetable producers rarely adopt minimum input or sustainable agricultural practices for altruistic reasons. While some family-owned concerns have followed this approach with the intent of passing their land onto the next generation in as pristine a state as possible, much of California’s vegetable hectarage is managed by large corporations. Thus, development and implementation strategies using reduced pesticide input are less likely the result of environmental concerns and more likely due to economic incentives, legislation limiting pesticide use, or the development of significant levels of pesticide resistance. In terms of pesticide use, the California vegetable industry is approaching a critical period. California’s expanding urban population has led to an increase in the influence of environmental activists, labor unions, and other consumer groups that are increasingly vocal in their opposition to pesticides. In addition, the current senate and assembly, committees in California that deal with pesticides have few members with rural or agricultural backgrounds. This situation has lead to an increase in legislation restricting pesticides. At least 26 new bills relevant to the subject were introduced in California in 1987 alone. Nearly all of these would require further restrictions on the use of chemicals for insect control. The impact of the new laws dealing with ground water contamination -and plant-back restrictions has dramatically changed pesticide use patterns in California; as a consequence, the application of persistent pesticides has declined appreciably. The impact of laws generated by referendum (placed on the ballot after proponents file the required number of signatures on petitions) is less well-defined. Such consumer-generated legislation provides evidence of the growing perception that consumers take the risk when pesticides are used, while growers reap the profits. There also has been a resurgence in environmental concern by the general population. In the past few years, incidents of environmental concern at Love Canal and Kesterson Reservoir, as well as the tragic events at Bhopal, India, have been given considerable time on television. The publicity associated with the watermelon contamination incident in California and the recent National Academy of Sciences report (National Research Council, 1986) highlighting the potential for pesticidal contamination in vegetables, have brought this concern into nearly every household in the country. Our ability to find residues at the parts-per-trillion level has aggravated this problem. Many consumers do not recognize differences in risk levels between parts per hundred and parts per trillion, they only recognize that no level of risk is acceptable. An additional stimulus for reduced insecticide use is the declining availability of efficacious insecticides. The rate of development of insecticide resistance is increasing exponentially (Georghiou, 1986). Nearly every entomologist study vegetable crop production can cite cases of extensive losses resulting from insecticide resistance. The $20 million loss documented by California’s celery industry in 1984 following the development of resistance by the leafminer [Liriomyza trifolii (Burgess) (Diptera: Agromyzidae)] to diverse chemicals provides an excellent example (California Celery Research Advisory Board, 1986). Thus, the need has been adequately demonstrated to

Selenium in wetlands and waterfowl foods at Kesterson Reservoir, California, 1984

Kesterson Reservoir (Kesterson) received subsurface agricultural drainwater containing high levels of salts and selenium from farmland in the San Joaquin Valley of California. The accumulation of selenium in wetlands and waterfowl foods at Kesterson was investigated during May, August, and December of 1984. High concentrations of selenium vegetation, and aquatic insects. Mean selenium concentrations in aquatic plants and insects ranged from 1.5 to 170 micrograms/g dry weight and were about 11 to 290 times those found at a nearby reference site. Concentrations in some waterfowl food plants and insects at Kesterson were up to 64 times those reported to be a health hazard to birds. Selenium concentrations were more seasonally variable in aquatic plants than in aquatic insects. Few differences in selenium accumulation were found among ponds. Deposition of selenium in plant parts was not uniform; rhizomes contained higher concentrations than seeds and leaves were intermediate. Most biota bioaccumulated maximum selenium concentrations that were 1,000 to nearly 5,000 times the concentration in the water.

Bioaccumulation of selenium in birds at Kesterson Reservoir, California

This study was conducted to determine selenium (Se) concentrations in tissues of birds collected during the 1983-1985 nesting seasons at Kesterson Reservoir (an area receiving high-Se irrigation drainage water), compare them with birds from reference sites within California's Central Valley, and relate them to food-chain Se concentrations at the study sites. Within years, Se in livers of adult birds collected early and late in the nesting season changed significantly at both Kesterson and the primary reference site (Volta Wildlife Area). These changes were related to the length of time birds had been present at the study sites and the associated accumulation (at Kesterson) or depuration (at Volta) of Se. All species showed significant location differences, which were greatest in species that occurred at Kesterson throughout the year or fed more consistently within the reservoir. There were few species differences in Se for birds at the reference sites (where food-chain Se levels were "normal" [less than or equal to 2 micrograms/g, dry wt]). At Kesterson (where bird foods generally contained greater than 50 micrograms Se/g), species patterns varied by year, probably because of varying periods of residence and other factors. Se concentrations in kidneys and livers of American coots (Fulica americana) were significantly correlated (r = 0.9845); Se concentrations in breast muscles and livers of juvenile ducks (Anas spp.) also were correlated (r = 0.8280). Body weights of adult coots were negatively correlated with liver Se concentration. Late-season resident breeding birds or pre-fledging juvenile birds reared at a site usually provided the best indication of site-specific Se bioaccumulation.

Influence of temperature and organic amendments on the mobilization of selenium in sediments

Toxic amounts of selenium have been found in sediments and water at Kesterson Reservoir (Merced County, Calif.). A sediment column study was established for determination of Se 0 (Se volatilization potential) and k (Se voltalization rate coefficient) derived from a first-order kinetics model. Increasing the temperature from 15 to 35°C promoted volatilization of Se ( Q 10 = 1.96). The amount of Se leached out of the sediments was independent of the initial total Se inventory. Volatilization of Se followed a first-order reaction and was highly dependent on the initial Se concentration. The Se 0 ranged from 0.18 to 3.63 mg Se kg −1 sediment with k values ranging from 0.003 to 0.053 day −1. The addition of organic amendments promoted volatilization with Se being less available for leaching. The application of gluten, a wheat storage protein, was found to enhance voltilization of Se (1.7 to 3.2-fold over the control) more strongly than other treatments (e.g. casein, orange peel and cattle manure). Volatilization may be an important dissipation mechanism for detoxification of seleniferous sediments.

The distribution, speciation and geochemical cycling of selenium in a sedimentary environment, Kesterson Reservoir, California, U.S.A.

The well-defined and intensively studied episode of Se contamination at Kesterson Reservoir (Merced County, California, U.S.A.) provided a unique opportunity to describe the distribution, speciation and geochemical transformations of Se in a variety of geochemical and ecological settings, ranging from permanent ponds to semi-arid grasslands and salt flats. Kesterson Reservoir comprises 500 ha of land contaminated with Se from agricultural drain water. In most places. Se was concentrated in surficial organic detritus and the surficial decimeter of mineral soil. At dry sites, selenate ion predominated below 20 cm depth. Elemental selenium (Se 0) also was prominent. The amount of zero-valent Se increased slowly with time. Although selenate is thermodynamically stable in the vadose zone in the presence of oxygen, Se 0 is an additional, metastable product of the mineralization of organic selenium. Thiols and inorganic sulfides dramatically increase the solubility of Se 0. Decreasing pH inhibits the reaction, explaining the observed decrease in solubility and biological availability of Se in soil and aquatic systems at low pH. Adding thiols or methionine to soil increases the emission of volatile Se compounds several-fold, suggesting that thiols play a major role in the microbial cycling of Se in soil.

Recruitment Failure in American Avocets and Black-Necked Stilts Nesting at Kesterson Reservoir, California, 1984-1985

We evaluated recruitment by American Avocets (Recurvirostra americana) and Black-necked Stilts (Himantopus mexicanus) in 1984 and 1985 at the selenium-contaminated Kesterson Reservoir and at a nearby reference site, the Volta Wildlife Area, both in western Merced County, California. Nests were monitored to determine their outcomes, including hatching success, and broods were censused three times per week during the breeding season. Chicks were counted and broods classified according to age. Although large numbers of chicks were presumed to have hatched at Kesterson, only one chick older than about 2 weeks of age was observed there during the 2-year study. It is unlikely that chicks of either species survived to fledging at Kesterson during the study period, whereas one-month-old or older avocet and stilt broods were seen both years at Volta. Selenium occurred at high concentrations in food-chain organisms only at Kesterson and was the most likely cause of the recruitment failure of stilts and avocets at Kesterson Reservoir.

Selenium accumulation by raccoons exposed to irrigation drainwater at Kesterson National Wildlife Refuge, California, 1986

In February-March 1986, eight raccoons (Procyon lotor) were collected at Kesterson Reservoir (Merced Co., California), which had received selenium-contaminated irrigation drainwater, and four raccoons were collected at the nearby Volta Wildlife Area, which had not. Selenium concentrations in Kesterson raccoons averaged 19.9 ppm (micrograms/g dry wt) in liver, 28.3 ppm (dry wt) in hair, 21.6 ppm (dry wt) in feces, and 2.61 ppm (wet wt) in blood and exceeded Volta concentrations by 12, 30, 21, and 10 times, respectively. Selenium concentrations in livers of Kesterson raccoons were less than those in five of nine other mammal species sampled in 1984. Selenium concentrations in hair provided the strongest statistical separation between study areas. Hemoglobin levels in two Kesterson raccoons equalled levels reported in rats with selenium-induced anemia, but the raccoons showed no illness. Amyloidosis in one Kesterson raccoon may have been selenium-induced. Our data indicate that raccoon births peaked about 2 months later than was previously reported. Based on our sample of 12 raccoons, we found no evidence that contamination by irrigation drainwater had negative effects on raccoons inhabiting Kesterson.

Nest Success, Cause-Specific Nest Failure, and Hatchability of Aquatic Birds at Selenium-Contaminated Kesterson Reservoir and a Reference Site

Comparaison du succes reproducteur, des causes specifiques d'echec et des taux d'eclosion pour 8 especes d'oiseaux aquatiques nichant sur le Reservoir Kesterson (Californie) avec un site de reference non contamine par le selenium