“The Kesterson effect” |
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Authors: | Theresa S Presser |
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Institution: | (1) National Research Program, US Geological Survey, 345 Middlefield Road (MS 435), 94025 Menlo Park, California, USA |
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Abstract: | Hypothesized to be derived from Cretaceous marine sedimentary rocks, selenium contamination of the Kesterson National Wildlife
Refuge is traced through irrigation drainage to the source bedrock of the California Coast Ranges. This biogeochemical pathway
of selenium is defined here as the “Kesterson effect.” At the refuge ponds, this effect culminated in 1983 in a 64% rate of
deformity and death of embryos and hatchlings of wild aquatic birds. From the previous companion paper on irrigation drainage,
the Kesterson effect has been implicated in nine of 11 reconnaissance areas studied in the western United States. Deformities
have resulted in at least five of these sites. Climatic, geologic, hydrologic, and soil conditions in these reconnaissance
areas are similar to those in the area surrounding Kesterson National Wildlife Refuge in the west-central San Joaquin Valley
of California. In California, selenium, as selenate, was ultimately found weathered with sulfur from marine sources in soluble
sodium and magnesium sulfate salts, which are concentrated by evaporation on farmland soils. The Se, mobilized by irrigation
drainage, is bioaccumulated to toxic levels in refuge wetland ponds that are located mainly in hydrologically closed basins
and thus act as concentrating disposal points. The depositional environment of the ponds may be similar to that of the nutrient-rich
continental shelf edge and slope in which Cretaceous, Eocene, and Miocene sediments found to be seleniferous in the California
Coast Ranges were deposited. Bioaccumulation may be therefore a primary mechanism of selenium enrichment in ancient sediments
in addition to that of the formerly suggested Cretaceous volcanic pathway. |
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Keywords: | Selenium Cretaceous marine sedimentary rocks Sulfate evaporative salts Selenoamino acids San Joaquin Valley “ Rock to duck” |
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