INFLUENCE OF NATURAL DISSOLVED ORGANIC MATTER, TEMPERATURE, AND MIXING ON THE ABIOTIC HYDROLYSIS OF TRIAZINE AND ORGANOPHOSPHATE PESTICIDES

摘要

Abiotic hydrolysis of simazine, atrazine, diazinon, methylparathion, and chlorpyrifos was studied in three different natural waters and buffered Milli-Q water. The triazines showed no detectable decrease in concentration in any of the waters over 43 days at pH 8.0 and 40 degrees C. The rates of hydrolysis for diazinon and methylparathion were statistically similar in all waters tested. Chlorpyrifos exhibited a similar to 32% decrease in hydrolysis rate in the presence of a high concentration of dissolved organic matter (DOM) (34.5 mg/L dissolved organic carbon). The activation energies are larger, and thus the predicted hydrolysis rates are significantly slower than those previously reported. The effect of continuous vigorous mixing on hydrolysis rates was investigated and found to have only a minor effect. The results suggest that uncatalyzed abiotic hydrolysis is very slow for these compounds at the temperatures and pH's typical of most natural waters and affirm the need for a greater understanding of the relative influence of DOM, catalysis, and biodegradation on the fate of organophosphate and triazine pesticides.