Abstract
We developed a bioaccumulation model from an extensive set of monitoring data to predict selenium (Se) concentrations in biota within a terrestrial system (Kesterson Reservoir, CA). The model uses water-extractable Se and total Se concentrations in soil to estimate the expected mean and ranges of Se concentrations in biota at Kesterson for future scenarios. Biological monitoring data collected at Kesterson from 1989 to 1994 were used to parameterize the initial model. The model was tested and updated with additional sample results from 1995 through 2001 biological monitoring and validated and calibrated using Se concentrations from sampling conducted in 2004 and 2006. Minor adjustments were made to the model based on each additional year's results, and the model was used in 2014 to assess whether there were continuing threats to wildlife at Kesterson. The model predicts Se concentrations in small mammals, bird blood, and bird eggs in common species found at Kesterson. This model was used for the final assessment of Kesterson in 2014 and performed well, but there was variability in results, probably due to differences in individual diets and feeding ranges of animals. The model has been further refined since 2014, as we describe here. The model performs well for predicting central tendency and is conservative as the predicted upper limits of the biotic exposure distributions were mostly similar or higher than the measured. The trophic and tissue transfer factors and regression equations should be applicable to other Se-contaminated sites; adjusting weighting factors based on diet and range allows the model to be adapted and used at other sites.
Highlights
We developed a bioaccumulation model from an extensive set of monitoring data to predict selenium (Se) concentrations in biota within a terrestrial system (Kesterson Reservoir, CA)
Kesterson Reservoir received subsurface agricultural drainwater contaminated with selenium (Se) in the late 1970s and early 1980s (Ohlendorf and Santolo 1994)
Paired samples were used to describe the relation between detritus and W×Se concentrations (r2 = 0.51, n = 103, P < 0.001)
Summary
Kesterson Reservoir (hereafter, “Kesterson”) received subsurface agricultural drainwater contaminated with selenium (Se) in the late 1970s and early 1980s (Ohlendorf and Santolo 1994). Plant species at Kesterson are predominantly non-native annual forbs and grasses. Those species occur most abundantly in the more disturbed filled areas. The less disturbed areas support dominant native plant species such as saltgrass (Distichlis spicata), which continues to dominate many of the grassland areas. Most of the former cattaildominated wetlands that were drained had a thick thatch layer that persisted over many years due to the lack of moisture for decomposition, partly because of the drought conditions through 1993. Those areas showed the greatest habitat change as the cattail thatch decomposed
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