Degradation of carbon disulphide (CS^sub 2^) in soils and groundwater from a CS^sub 2^-contaminated site

This study is the first investigation of biodegradation of carbon disulphide (CS^sub 2^) in soil that provides estimates of degradation rates and identifies intermediate degradation products and carbon isotope signatures of degradation. Microcosm studies were undertaken under anaerobic conditions using soil and groundwater recovered from CS^sub 2^-contaminated sites. Proposed degradation mechanisms were validated using equilibrium speciation modelling of concentrations and carbon isotope ratios. A first-order degradation rate constant of 1.25 Ã-- 10^sup â '2^ h^sup â '1^ was obtained for biological degradation with soil. Carbonyl sulphide (COS) and hydrogen sulphide (H2S) were found to be intermediates of degradation, but did not accumulate in vials. A ^sup 13^C/^sup 12^C enrichment factor of â '7.5 ±Â 0.8 â[euro]° was obtained for degradation within microcosms with both soil and groundwater whereas a ^sup 13^C/^sup 12^C enrichment factor of â '23.0 ±Â 2.1 â[euro]° was obtained for degradation with site groundwater alone. It can be concluded that biological degradation of both CS^sub 2^-contaminated soil and groundwater is likely to occur in the field suggesting that natural attenuation may be an appropriate remedial tool at some sites. The presence of biodegradation by-products including COS and H2S indicates that biodegradation of CS^sub 2^ is occurring and stable carbon isotopes are a promising tool to quantify CS^sub 2^ degradation.[PUBLICATION ABSTRACT]