Selenium volatilization from a soil-plant system for the remediation of contaminated water and soil in the San Joaquin Valley

Selenium (Se) contamination of agricultural drainage water is a major environmental problem facing California agriculture. To demonstrate the potential effectiveness of biological volatilization in removing Se from contaminated water and soil, Se volatilization was determined under field renditions from a soil-plant (Salicornia bigelovii Torr,) treatment system in the San Joaquin Valley, California. Volatile Se was collected using an open-now sampling chamber system, biweekly during the S. bigelovii growing season from February to September 1997, and monthly from September 1997 to January 1998, The rate of Se volatilization fluctuated under different field conditions during the study year, with an overall mean of 155 +/- 25 mu g Se m(-2) d(-1). Biological volatilization removed 62 mg Se m(-2) yr(-1) which accounted for 6.5% of the annual total Se input (958 mg Se m(-2) yr(-1)) to the S, bigelovii field. Forward trajectory analysis showed that the air mass that passed through the research area generally moved quickly out of the San Joaquin Valley within the first 24 h, probably transporting airborne Se from the research site toward the eastern Sierra Nevada in spring and fall, the southern mountainous areas in summer, and the Coast Mountain region in winter. This study suggests that biovolatilization represents an environmentally sound technology for managing Se-contaminated soil and agricultural drainage water. Future research will focus on establishing new means for enhancing Se volatilization in the field.