Degradation of trifluoroacetate in oxic and anoxic sediments

Abstract

THE deleterious effect of chlorofluorocarbons on stratospheric ozone has led to international cooperation to end their use^{1– 3}. The search for acceptable alternatives has focused on hydrofluorocarbons (HFCs) or hydrochlorofluorocarbons (HCFCs) which are attractive because they have relatively short atmospheric residence times⁴. HFCs and HCFCs are attacked by tropospheric hydroxyl radicals, leading to the formation of trifluoroacetate (TFA)⁵. Most of the atmospheric TFA is deposited at the Earth's surface⁶, where it is thought to be highly resistant to bacterial attack⁵. Therefore, use of HCFCs and HFCs may lead to accumulation of TFA in soils, where it could prove toxic or inhibitory to plants and soil microbial communities^5,7. Although little is known about the toxic-ity of TFA, monofluoroacetate, which occurs at low levels in some plants⁸ and which is susceptible to slow attack by aerobic soil microbes⁹, is known to be acutely toxic^10–13. Here we report that TFA can be rapidly degraded microbially under anoxic and oxic conditions. These results imply that significant microbial sinks exist in nature for the elimination of TFA from the environment. We also show that oxic degradation of TFA leads to the formation of fluoroform, a potential ozone-depleting compound with a much longer atmospheric lifetime than the parent compounds.