Mikrobiologische Volatilisierung von anorganischem Selen aus Deponiesickerw?ssern bei umweltrelevanten Konzentrationen

摘要

Background, aim, and scope Determination of the rates of microbial alkylation are of interest with respect to natural attenuation of harmful selenium concentrations or selenium charges in contaminated ecosystems. Materials and methods Landfill gas and the headspace of microbial microcosm incubation vessels were sampled in Tedlar? bags. On-line hyphenation of an efficient enrichment method (cryotrapping-cryofocusing), a gaschromatographic separation technique, and the sensitive ICP-MS detection system was used for speciation of volatile organoselenium compounds. A detection limit at the ultra trace level (pg Se) was achieved with this CT-CF-GC-ICP-MS technique. Results Incubation of landfill leachate with Alternata alternata as an active methylating organism showed a production of volatile selenium compounds (DMSe, DMDSe, EMDSe, DEDSe) over the whole range of applied inorganic selenium concentrations (10?μg?L–1 to 10?mg?L–1), with volatilization rates of up to 10?mg m–3?d–1. For selenium concentrations of 1?mg?L–1 in the nutrient broth, up to 7?% of the inorganic selenium was volatilized after one week. The same volatile selenium compounds were observed in landfill gas. Discussion The amount of volatilized selenium was comparable to that found in other studies with microbial pure cultures as well as isolates from waters or soils, but at much lower initial concentrations used in the incubations. Conclusions The alkylation of selenium in the enriched mixed culture from landfill leachate at environmentally relevant concentrations indicates that the organoselenium compounds of same species composition and distribution determined in landfill gas are produced by microorganisms. Recommendations and perspectives The microbial alkylation of toxic inorganic selenium species to less toxic or non-toxic, volatile compounds is an efficient method for bioremediation of contaminated sites even at relatively low Se concentrations.