title: Effect of moisture and casein on demethylation of trimethylselenonium in soil.
abstract: Trimethylselenonium ion (TMSe+) is a major urinary selenium (Se) metabolite of animals. The effect of soil moisture and casein on the demethylation of TMSe+ were examined in three California soils [Tulare Basin (TL), Losthill (LH) and Five Points (FP) upland areas] treated with 20 microg/g TMSe+. Results showed that soil moisture positively affected the demethylation of TMSe+ to volatile dimethylselenide (DMSe). In the non-saline TL and FP soils, the highest demethylation rates were 0.169-0.454, 0.646-2.71, and 3.15-6.01 microg/g per day from a 10, 20, and 100% moisture soil, respectively. During 51 days of the experiment, approximately 75.4-80.2% of added TMSe+ was demethylated to volatile DMSe. In contrast, in a saline LH soil, the demethylation rate was < 0.2 microg/g per day, and only 7% of the added TMSe+ was demethylated to volatile DMSe. Addition of casein stimulated the demethylation of TMSe+ in a 10% moisture TL soil. Dissolved DMSe, dimethylselenoxide (DMSeO) and TMSe+, and adsorbed TMSe+ were found in the three experimental soils. Concentrations of dissolved and adsorbed TMSe+ were much higher in the LH soil than in the TL and FP soils. This study showed that demethylation of TMSe+ dominates in the FP and TL soils, and adsorption of TMSe+ is a more important process in the LH soil.
authors.affiliation: Department of Environmental Sciences, University of California, Riverside 92521-0424, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Zhang
authors.forename: W T
authors.initials: WT
authors.lastname: Frankenberger
mesh_terms: D000818:Animals; D000829:Animals, Domestic; D004784:Environmental Monitoring; D018036:Selenium Compounds / Q000378:metabolism*; D012989:Soil Pollutants / Q000378:metabolism*; D014556:Urine / Q000737:chemistry
chemical_list: D018036:Selenium Compounds; D012989:Soil Pollutants; C003717:trimethylselenonium