The fate of selected pesticides in aboveground disposal vessels

Pesticide use occurs on most farms and may lead to groundwater contamination if improperly handled. The residual pesticide in sprayers, pesticide rinse water and rinse water from sprayers may be sprayed on fence rows or dumped at the preparation site. This research was conducted to determine if a low cost pesticide disposal system for farmers was feasible. The system included a rinse collection area, raised soil filled steel collection vessels residing on a concrete slab and walls to contain any spills. Rinse water was applied on a weekly basis to each soil filled steel vessel. Besides the pesticides entering from the farm operation, seven pesticides were applied to each vessel over two years and monitored for dissipation. The monitored pesticides were carbaryl, simazine, alachlor, chlorpyrifos, endosulfan I and II, and captan. Over two growing seasons from May through October a total of 390 g a.i. of each of the pesticides were applied to each of six steel research vessels containing a locally obtained soil. To monitor the dissipation of the selected pesticides, air and soil samples were analyzed for the parent compound and the major metabolite. At the end of the second growing season the following amount of compounds remained from the 390 g a.i. applied: carbaryl 20.3 g or 5.2%; simazine 139.6 (35.8%); alachlor 40.6 g (10.4%); chlorpyrifos 70.6 g (18.1%); endosulfan 1 92.4 g (23.7%); endosulfan II 71.4 g (18.3%) and captan 16.0 g (4.1%). Volatilization accounted for greater than 50% of the loss for each of the following: chlorpyrifos; endosulfan I and II; alachlor; and captan. Carbaryl and simazine were near the 30% range for airborne losses. Carbaryl appeared to be primarily degraded by chemical and/or microbial action. Simazine loss was nearly equal between volatilization and soil degradation. Overall the system appeared to work effectively to dissipate the monitored pesticides over the 17 month period. The system was able to dissipate approximately 4800 gallons of pesticide rinse water in the first year. In the second year more than 5200 gallons or 97% of the second years grand total volume was dissipated.