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 by Bureau of ReclamationBuilt by Bureau of Reclamation Originally from Five Points, CA, to BayOriginally from Five Points, CA, to Bay Reservoir = controlling reservoir, midpointReservoir = controlling reservoir, midpoint

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

Deformity and death of waterfowl leads to closure

ha site, 60% filled in 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

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

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

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

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

Questions?