Microbial Formation of Volatile Selenium Compounds in Soil

Abstract Selenium was volatilized from soils amended with elemental Se, selenite, selenate, trimethylselenonium chloride, selenomethionine, and selenocystine and incubated in air or anaerobically. The processes were wholly or largely the result of microbial action. The conversion of selenite and selenate to volatile products was enhanced if soil was amended with organic materials. Indigenous soil Se was also volatilized in the presence of supplemental organic matter. The products were identified by combined gas chromatography‐mass spectrometry. Dimethyl selenide was generated from all Se compounds tested when amended soils were incubated in the presence of air. Under anaerobic conditions, dimethyl selenide was produced from the three organic Se compounds and selenate, and a product tentatively identified as hydrogen selenide (H 2 Se) was evolved from soil receiving elemental Se, selenite, selenate, or selenocystine. Dimethyl diselenide was also formed from selenomethionine in soil incubated in air or anaerobically.