Degradation of Organophosphorus Pesticides and Their Transformation Products in Estuarine Waters

Abstract

The degradation of 10 organophosphorus pesticides in natural estuarine waters was studied. Estuarine water samples were spiked with organophosphorus pesticides at 50 μg/L level and were placed into 2-L Pyrex flasks being exposed outdoor to ambient sunlight and temperature. A sample 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 determinations were performed by solid-phase extraction (SPE) with C 18 Empore disks followed by GC-NPD and GC-MS with El and by on-line SPE using PLRP-s exchangeable cartridges (Prospekt) followed by LC-DAD and LC-thermospray MS in PI mode. Five organophosphorus pesticides were stable for less than 1 week (disulfoton, fenamiphos, fenthion, malathion, and temephos), others had a half-life of ca. 1 week (chlorpyrifos-methyl, methidathion, and diazinon), and the rest showed a half-life of ca. 10 days (isofenphos and pyridafenthion). The half-life of three pesticide transformation products : disulfoton sulfoxide, disulfoton sulfone, and fenthion sulfoxide varied from 7 to 12 days.