THE INFLUENCE OF SALINITY AND SEDIMENT ON THE LOSS OF ATRAZINE FROM THE WATER COLUMN

Two experiments of 128 - 130 days duration were conducted to determine the influence of salinity and sediment type on the loss of atrazine f rom the water column. In the first experiment, atrazine did not exhibi t a significant loss after 128 days in any of the test conditions (atr azine concentrations of 5-5000 mu g/L and salinities of 5-35 ppt) prep ared with autoclaved water. However, a 17% loss was reported after 128 days in an ambient estuarine condition of 13 ppt. In the second 130 d experiment, the loss of 50 mu g/L atrazine from the water column was determined at salinities ranging from 5 to 25 ppt without sediment and with either sand or silt-clay sediment. Results after 130 days were n o loss of atrazine in the water only test conditions at the various sa linities; loss of atrazine in the water column was significant in both sediment conditions and type of sediment did not appear to influence the loss from the water column; atrazine adsorption to clay-silt sedim ent was approximately twice as high as sand and loss of atrazine in th e water column of both sediment conditions appeared greater at the hig her salinity (25 ppt) when compared to the lower salinity (5 ppt).