INVOLVEMENT OF HYDROGEN-SULFIDE IN THE DEGRADATION OF PARATHION IN FLOODED ACID SULFATE SOIL

There is increasing evidence that certain pesticides, resistant to degradation in aerobic systems, undergo fairly rapid degradation in anaerobic ecosystems such as flooded soil1,2. After flooding, the soil components NO3-, Fe3+, Mn4+ and SO42- are reduced almost in a thermodynamic sequence with a corresponding shift in favour of anaerobic microorganisms3. Although anaerobic microorganisms have been implicated directly in the degradation of some pesticides in anaerobic environments1,2, there is circumstantial evidence for chemically catalysed reactions, involving, for example, the iron redox system4 or reduced iron porphyrins 5. However, the importance of this and other dominant redox reactions in the behaviour of pesticides in a flooded soil is not well understood. We report here the involvement of hydrogen sulphide, the end product of sulphate reduction, in the degradation of parathion in a flooded acid sulphate soil. © 1979 Nature Publishing Group.