Submitted to: SETAC Conference
Publication Type: Abstract Only
Publication Acceptance Date: 7/15/2007
Publication Date: 11/12/2007
Citation: Denton, D.L., Moore, M.T., Cooper, C.M., Wrysinski, J., Miller, J.L., Reece, K., Crane, D., Robins, P. 2007. Assessment of Vegetated Agricultural Drainage Ditches for Irrigation Runoff Mitigation in California. Abstracts of the 2007 Annual Meeting of the Society of Environmental Toxicology and Chemistry. p. 53.
Interpretive Summary: Abstract only. Interpretive summary not required.
Technical Abstract: Widespread contamination of California water bodies by the organophosphate insecticides diazinon and chlorpyrifos is well documented. While their usage has decreased over the last few years, a concomitant increase in pyrethroid usage (e.g permethrin) (replacement insecticides) has occurred. Vegetated agricultural drainage ditches (VADD) have been proposed as a potential economical and environmentally efficient management practice to mitigate the effects of pesticides in irrigation and storm runoff. Three ditches were constructed in Yolo County, California for a field trial. A U-shaped vegetated ditch, a V-shaped vegetated ditch, and a V-shaped unvegetated ditch were each amended for 8 h with a mixture of diazinon, permethrin, and suspended sediment simulating an irrigation runoff event. Water, sediment, and plant samples were collected spatially and temporally and analyzed for diazinon and permethrin concentrations. Pesticide half-lives were similar between ditches and pesticides, ranging from 2.4-6.4 h. Differences in half-distances (distance required to reduce initial pesticide concentration by 50%) among pesticides and ditches were substantial, indicating importance of vegetation in mitigation. Cis-permethrin half-distances ranged from 22 m (V-vegetated) to 347 m (V-unvegetated). Half-distances for trans-permethrin were similar, ranging from 21 m (V-vegetated) to 239 m (V-unvegetated). Diazinon half-distances demonstrated the greatest differences (55 m for V-vegetated and 1155 m for V-unvegetated). Such economical and environmentally successful management practices will offer farmers, ranchers, and landowners a viable alternative to more conventional (and sometimes expensive) practices currently suggested by conservation organizations.