DIFFUSION AND DEGRADATION OF ATRAZINE IN A WATER/SEDIMENT SYSTEM

Abstract

This study determined the effects of temperature and residence time on diffusion and degradation of [14C]atrazine applied to the surface of sterilized and nonsterilized river water over a sediment. Water and sediment were placed in glass columns and incubated at 5 or 24°C. Samples were collected at 0, 7, 14, 28, 42, 56, and 112 d before and after disturbance. The warmer temperature (24°C) initially increased the rate of 14C distribution in the aqueous phase. Disturbance caused approximately 15% of the total 14C to be removed from the aqueous phase by sterile or unsterile sediment incubated at 5°C. At 24°C, the level of 14C in disturbed sediments incubated for more than 28 d gradually increased. This increased retention of 14C by sediment coincided with greater detection of the polar metabolite hydroxyatrazine (HA). More HA was recovered in nonsterilized than in sterilized sediments, indicating the contribution of biological processes to the production of this metabolite. In undisturbed sediments at 24°C, approximately 32% and 10% of the applied 14C permeated the top and bottom 1-cm segments, respectively. In columns incubated at 5°C, less than 5% of the 14C reached the surface of the submerged sediment. The potential impact of atrazine on biota associated with sediment would diminish with time because of dilution in the aqueous phase, transformation to HA, and bound residue formation.