VOLATILIZATION OF SELENIUM FROM A DEWATERED SELENIFEROUS SEDIMENT - AFIELD-STUDY

One of the major concerns in central California (San Joaquin Valley) i s the level of selenium (Se) in evaporation ponds containing agricultu ral drainage water. The objective of this work was to determine if vol atilization of Se could be used as a bioremediation program to detoxif y a saline seleniferous sediment of a dewatered evaporation pond. The dewatered sediment was rototilled, divided into subplots, and amended with various organic materials including citrus (orange) peel, cattle manure, barley straw and grape pomace. Some of the subplots were ferti lized with nitrogen [(NH4)(2)SO4] and zinc (ZnSO4). Selenium volatiliz ation was monitored in the field with a flux chamber system utilizing alkaline peroxide to trap the gas. Overall, the greatest emission of g aseous Se was recorded in the summer months and the lowest emission du ring the winter months. The background emission of volatile Se average d 3.0 mu g Se h(-1) m(-2). The most effective organic amendment was ca ttle manure with an avg. Se emission of 54 mu g Se h(-1) m(-2). Compos ite soil samples from each subplot (upper 15 cm) were analyzed for tot al Se on a monthly interval during the course of this field study. Aft er 22 months, the application of water plus tillage alone removed 32.2 % of the Se content while the cattle manure treatment removed 57.8%. A mong the parameters which enhanced volatilization of Se were an availa ble C source, aeration, moisture, and high temperatures. This held stu dy indicates promising results in detoxifying seleniferous sediments v ia microbial volatilization once environmental conditions have been op timized.