DEGRADATION OF ORGANOPHOSPHORUS PESTICIDES AND THEIR TRANSFORMATION PRODUCTS IN ESTUARINE WATERS

The degradation of 10 organophosphorus pesticides in natural estuarine waters was studied. Estuarine water samples were spiked with organoph osphorus pesticides at 50 mu g/L level and were placed into 2-L Pyrex flasks being exposed outdoor to ambient sunlight and temperature. A sa mple of 10-75 mL of water was collected every week for analysis during a period of 5-6 weeks from January to March. The analytical determina tions were performed by solid-phase extraction (SPE) with C-18 Empore disks followed by GC-NPD and GC-MS with EI and by on-line SPE using PL RP-s exchangeable cartridges (Prospekt) followed by LC-DAD and LC-ther mospray MS in PI mode. Five organophosphorus pesticides were stable fo r less than 1 week (disulfoton, fenamiphos, fenthion, malathion, and t emephos), others had a half-life of ca. 1 week (chlorpyrifos-methyl, m ethidathion, and diazinon), and the rest showeda half-life of ca. 10 d ays (isofenphos and pyridafenthion). The half-life of three pesticide transformation products: disulfoton sulfoxide,, disulfoton sulfone, an d fenthion sulfoxide varied from 7 to 12 days.