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Selenium and the Kesterson Reservoir

Selenium and the Kesterson Reservoir. Kayla Carpenter. San Joaquin Valley: Lots of farming Poorly drained Built drain to the San Francisco Bay. San Luis Drain. Built 1968-1975 by Bureau of Reclamation Originally from Five Points, CA, to Bay Reservoir = controlling reservoir, midpoint.

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Selenium and the Kesterson Reservoir

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  1. Selenium and the Kesterson Reservoir Kayla Carpenter

  2. San Joaquin Valley: • Lots of farming • Poorly drained • Built drain to the San Francisco Bay

  3. San Luis Drain • Built 1968-1975 by Bureau of Reclamation • Originally from Five Points, CA, to Bay • Reservoir = controlling reservoir, midpoint

  4. SELENIUM! • Water: 300 ppb from drain vs. <10ppb natural • Soil: above 100 ppm in evaporation ponds

  5. Deformity and death of waterfowl leads to closure

  6. 1988 • 500 ha site, 60% filled in • 15-150 cm uncontaminated soil • Wetland  upland grassland • PHYTOREMEDIATION! • Inexpensive, enviro friendly, rather effective • Brought in over 20 spp common weedy plants • Volatilized to atmosphere, dimethyl selenide • Aided by microorganisms, esp. in rhizosphere

  7. 4 Depositional Environments • Dryer northern ponds • Saltgrass (Distichlis) & alkali weed (Cressa) • Accumulates loose layer of organic detrius • “Playas” • Flooded in winter & spring, little organic matter • Ruppia spp then filamentous algae • Flooded & wet • Cattails (Typha) & alkali bulrush (Scirpus spp) • Stay wet  peat-like material • Submerged • Algae dominant (Chara, then filamentous & diatoms) • Thick organic ooze deposits in open waters

  8. Miscellaneous Findings • pH 6.5 –8.0 • Selenate, selenite, organic Se • Amount & speciation changed over time • Sharp decrease in water-extractable soil Se, esp top soil • Correlation between vegetation & water extractable Se • Plant roots can take up Se from lower soil profile  good news for aquifer • Food chain contamination less with upland than wetland • Plants in irrigated soils have higher Se concentrations • More volatilization in warm months & wet areas

  9. Rate of Removal • At current conditions, volatilization of 1-5% total selenium in top 60 cm • 5%: half gone 14 yrs, all gone 46 yrs • 1%: half gone 69 years, all gone 230 yrs • Further aided by irrigation, application of carbon & protein source (glucose & casein), aerobic conditions, and pH 8.0

  10. Conclusions • It is working • It’s slow • Still impacts food chain • Volatilized selenium

  11. Questions?

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