STRUCTURAL INFLUENCES OF LOW-MOLECULAR-WEIGHT DISSOLVED ORGANIC-CARBON MIMICS ON THE PHOTOLYTIC FATE OF ATRAZINE

The fate of atrazine 2-chloro-4-ethylamino-6-isopropylamino-s-triazine ) was examined in the presence of dissolved organic carbon (DOC) mimic s to discern the effect of the various structural characteristics of D OC with respect to direct photolysis and transformation via a photoini tiated nitrate-mediated hydroxy radical process (indirect photolysis). Experiments were conducted with coniferyl alcohol, 2-octanol, oxalic acid, pyrogallol, quinone, and salicylic acid. All mimics except octan ol and coniferyl alcohol caused an increase in the atrazine degradatio n rate when no nitrate was present. A decrease in atrazine degradation in indirect photolysis was observed for coniferyl alcohol, octanol, p yrogallol, and salicylic acid, whereas the rate increased with oxalic acid and quinone. Examination of the product ratios showed a dependenc e of the chemical activity (photosensitizer, OH. radical scavenger or OH. generator) on structure. Results revealed that structural aspects of DOG, in addition to concentration, must be considered when predicti ng the photolytic fate of pesticides.