Degradation of Atrazine in Estuarine Water/Sediment Systems and Soils

Herbicides have been postulated as a cause of the disappearance of submerged aquatic vegetation in the Chesapeake Bay. This research was undertaken to determine the longevity of 2‐chloro‐4‐ethylamino‐6‐isopropylamino‐ s ‐triazine (atrazine) in two estuarine water/sediment microcosm systems and two agricultural soil systems over an 80‐d period under aerobic and low‐O 2 conditions. Atrazine degradation proceeded more rapidly in the estuarine systems than in the soil systems. The disappearance of atrazine from the estuarine water was relatively rapid, with the half‐life (50% remaining in the water column) of the parent compound ranging from 3 to 12 d. Atrazine half‐life was determined to be 15 and 20 d for the two estuarine sediments and 330 and 385 d for the two agricultural soils. Hydroxyatrazine (2‐hydroxy‐4‐ethylamino‐6‐isopropylamino‐ s ‐triazine) was the major short‐term metabolite in both the estuarine and terrestrial systems. By the 21st day of the experiment, the percent of total extracted residues corresponding to atrazine and hydroxyatrazine were: 65, 20 and 10, 85 for the two estuarine systems; and 66, 29 and 93, 5 for the two soil systems. Decreased O 2 levels had little effect on atrazine degradation in the experimental systems. The rapid degradation of atrazine to hydroxyatrazine in estuarine water and sediment indicates a low probability for the accumulation of atrazine in the estuary.