|Smith Jr, Sammie|
|Shields Jr, Fletcher|
Submitted to: International Journal of Ecology and Environmental Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/9/2006
Publication Date: 6/15/2006
Citation: Smith Jr, S., Cooper, C.M., Lizotte Jr, R.E., Shields Jr, F.D. Storm Pesticide Concentrations in Little Topashaw Creek, USA. International Journal of Ecology and Environmental Sciences. 32(2): 173-182, 2006 Interpretive Summary: The Little Topashaw Creek (LTC) project emphasizes the use of large woody debris and biotechnical techniques for stream corridor restoration/rehabilitation in deeply incised channels. Determining pesticide runoff from nonpoint sources during high flow is an important part of understanding the extent of potential contamination in streams due to current agricultural practices as well as the assessment of impacts on aquatic stream habitats. The purpose of the present study was to examine and report seasonal patterns of pesticide occurrence and concentrations in LTC during high flow storm events over the period of 2000-2004. Of the 58 storm events, 38% occurred in the second quarter (spring) of each year. On a quarter year basis, detections per storm event were highest for the second quarter of 2001. The most frequently detected pesticides per storm event were the insecticides DDT (and metabolites) and methylparathion, along with the herbicides atrazine and metolachlor. The annual “spring flush” likely accounts for these observations. Such information will address the limited availability of seasonal pesticide contamination data during high flows in streams and help in the establishment of appropriate TMDLs (Total Maximum Daily Loads) for streams.
Technical Abstract: A suite of 17 current and past-use pesticides (and/or metabolites) was measured in the Little Topashaw Creek channel, Mississippi, USA, during high flow storm events throughout the period, 2000-2004, in order to determine seasonal patterns of pesticide occurrence and concentrations. During the sampling period, 1176 storm water samples were collected from 58 high flow storm events. There were 2038 pesticide detections greater than or equal to 0.1ppb (ug/L), equivalent to 10.2% of the possible 19,992 detections. On a quarter year basis, detections per storm event were highest for the second quarter of 2001 (with 111), followed by the fourth quarter of 2001 (with 81). Of the 58 storm events, 22 (38%) occurred in the second quarter, followed by 14 (24%), 13 (22%), and 9 (16%) in the first, third, and fourth quarters, respectively. Overall, most detections were for p,p’-DDT (542) and metabolites (129), totaling 671, followed by methylparathion (366), atrazine (277), and metolachlor (198). Primary agricultural land use in the near drainage contributing area upstream of the experimental LTC site includes cotton (Gossypium spp.), sweet potato (Ipomoea batatas), corn (Zea spp.), sorghum (Sorghum spp.), wheat (Triticum spp.), and soybeans (Glycine spp.). Of the herbicides detected, atrazine and metolachlor had the highest mean concentrations in high flow storm runoff in the second quarter of 2001 with values of 2.50±7.53 and 1.28±3.13 ppb, respectively. Among the current-use insecticides in high flow storm water in the second quarter of 2001, bifenthrin and lambda-cyhalothrin had the highest mean concentrations with values of 0.70±2.88 and 0.40±0.52 ppb, respectively. However, the most frequently detected current-use insecticides were methylparathion and chlorfenapyr, with 53 and 49 detections, respectively, followed closely by bifenthrin with 41 detections. The so-called annual seasonal “spring flush” in many US stream and river systems likely accounts for this phenomenon.