DISSIPATION OF 2,4-D DMA AND BEE FROM WATER,MUD, AND FISH AT LAKE SEMINOLE,GEORGIA1

ABSTRACT: Four 10-ha plots in dense watermilfoil beds of Lake Seminole, Georgia, were each treated with either 2,4-D DMA or 2,4-D BEE at rates of 22.5 and 45 kg a.e./ha. Both formulations were shown to be rapidly converted to the 2,4-D acid form, with no detection of 2,4-D DMA or 2,4-D BEE in the water within less than 24 hours after treatment. The maximum detected 2,4-D concentrations in the high rate 2,4-D DMA and 2,4-D BEE plots were 3.6 and 0.68 mg/, respectively. However, all but seven samples at a 2,4-D BEE plot showed nondetectable herbicide levels by day 7, with all water samples showing nondetectable levels by day 13. Dimethylnitrosamine and 2,4-dichlorophenol, potentially toxic transformation products of the herbicide formulations, were at nondetectable levels in all water samples. Sediment samples showed no significant net accumulation of 2,4-D, 2,4-D BEE, or 2,4-dichlorophenol during the summer monitoring; dimethylnitrosamine remained at nondetectable levels. There was no accumulation of 2,4-D in fish collected from the two plots treated with 2,4-D DMA. Four of 24 game fish from the 2,4-D BEE treatment plots contained low levels of 2,4-D in muscle tissue, with a maximum value of 0.29 μg/g. In contrast, 18 of 20 gizzard shad collected from these plots through day 13 contained detectable 2,4-D in the muscle, with a maximum concentration of 6.9 μg/g. All fish collected after day 13 contained nondetectable levels of 2,4-D. Small decreases in dissolved oxygen and pH, associated with the complete watermilfoil control in all plots, had returned to normal summer values by day 28.