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 ReclamationBuilt 1968-1975 by Bureau of Reclamation Originally from Five Points, CA, to BayOriginally from Five Points, CA, to Bay Reservoir = controlling reservoir, midpointReservoir = 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 pondsDryer northern ponds –Saltgrass (Distichlis) & alkali weed (Cressa) –Accumulates loose layer of organic detrius “Playas”“Playas” –Flooded in winter & spring, little organic matter –Ruppia spp then filamentous algae Flooded & wetFlooded & wet –Cattails (Typha) & alkali bulrush (Scirpus spp) –Stay wet  peat-like material SubmergedSubmerged –Algae dominant (Chara, then filamentous & diatoms) –Thick organic ooze deposits in open waters

9. 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

10. 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

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

12. Questions?