Abiotic persistence of atrazine and simazine in water

Hydrolysis and photolysis experiments have been undertaken to investigate t he abiotic persistence of atrazine and simazine in a variety of waters. Hyd rolysis only occurs to a significant extent at pH values at the lower limit of those found in the natural aquatic environment (pH 4.0 or less). Photol ysis was initiated by a wide range of wavelengths in waters at pH 4.0, but only by more energetic wavelengths of less than 300nm at higher pH values ( pH 6 to 8). Based on these data, the aquatic half-life of atrazine and sima zine in well-lit acidic upland waters will be typically six days. In lowlan d rivers with higher pH (7 to 8.5), these triazines are likely to exhibit h alf-lives of months rather than days. In groundwaters, atrazine and simazin e will have half-lives in the order of years, due to the exceedingly slow r ate of hydrolysis. (C) 1999 Society of Chemical Industry.