Persistence and fate of methyl parathion in sea water

Experiments are described to assess the effect of salt content, settled sewage, and pH on the stability and fate of the pesticide methyl parathion. Whilst it was relatively stable under acidic conditions, increased hydrolysis occurred under neutral conditions at pH8.5. Rates of hydrolysis decreased with increased salt content although sodium chloride did not seem to be involved. In samples containing settled sewage rates of biodegradation were initially slow, however as the bacterial population adapted to the insecticide, degradation was achieved in relatively short periods. The degradation pathways included the reduction of the nitro group, dealkylation and hydrolysis of the ester linkage.