|Smith Jr, Sammie|
Submitted to: International Journal of Ecology and Environmental Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 30, 2007
Publication Date: October 17, 2007
Citation: Smith Jr, S., Cooper, C.M., Lizotte Jr, R.E. 2007. Pesticides in shallow ground water in the forested wetland riparian area of the Beasley Lake Watershed, Mississippi, USA, 2001-2005. International Journal of Ecology and Environmental Sciences. 33(4):223-231. Interpretive Summary: The Beasley Lake watershed has a natural riparian area through which flows agricultural runoff containing pesticides. Using a series of sampling wells, the movement of pesticides into shallow ground water in this riparian area over the period of 2001-2005 was evaluated. The most frequently detected pesticides were p,p'-DDT and methyl parathion. The herbicides, metolachlor and atrazine were also frequently detected. The finding of p,p'-DDT and methyl parathion in shallow ground water was likely the result of enhanced solubility due to the relatively high soluble organic matter levels in riparian shallow ground water. The relatively high water solubility and high mobility rating of atrazine and metolachlor likely explain their frequent detection in shallow ground water. These findings of pesticide mixtures in shallow ground water corroborate results from other researchers and point to the continued need for studies on the long-term fate and implications of pesticides.
Technical Abstract: We evaluated the movement of pesticides into shallow ground water in a Mississippi Delta forested natural wetland riparian area in the Beasley Lake watershed (Sunflower County, Mississippi, USA). Four well sites were established, each with depths of 0.6, 1.5, 3.0, and 4.6 m (2’, 5’, 10’, and 15’, respectively). Present and past pesticide usage in the contributing watershed areas resulted in 17 pesticides (and/or metabolites) being targeted for analysis. Seven of the 16 wells (4 sites, 4 depths per site) produced shallow ground water sufficient for sampling. A total of 287 (range 26-50 over the 7 wells) shallow ground water samples were collected during 2001-2005 and each analyzed for the 17 targeted pesticides. There were 314 (6%) pesticide detections greater than or equal to 0.1 microgram L-1 (ppb) of a possible 4879 detections. The most frequently detected pesticide, p,p’-DDT, had 154 detections equivalent to 49% of the total 314 detections greater than or equal to 0.1 microgram L-1. Methyl parathion, the second most frequently detected pesticide, had 48 detections (15%) and the number of detections ranged from 1-9 over the 7 wells. The next most frequently detected pesticides were the herbicides metolachlor (41 detections, 13%) and atrazine (36 detections, 11%). Combined detections of p,p’-DDT, methyl parathion, metolachlor, and atrazine accounted for 89% (279) of all detections greater than or equal to 0.1 microgram L-1. The frequent finding of p,p’-DDT and methyl parathion in shallow ground water was likely due to the relatively high TOC levels in the riparian shallow ground water.