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Seasonal occurrence and export of five herbicides from a North Carolina Coastal Plain watershed
- Novak, J.M., Watts, D.W., Stone, K.C., Johnson, M.H.
- Transactions of the ASAE 2001 v.44 no.5 pp. 1201-1206
- water pollution, atrazine, cyanazine, agricultural land, herbicide residues, watersheds, losses from soil, streams, seasonal variation, metolachlor, alachlor, ametryn, coastal plains, North Carolina
- Herbicide detection in surface water sources has caused concern about contamination of these sources and adverse effects on human and aquatic health. Understanding surface water herbicide transport from agriculturally intensive watersheds is useful for development of herbicide best management practices to reduce off-site movement. The seasonal occurrence and load of five herbicides exported by a stream were determined for a North Carolina Coastal Plain watershed. Grab samples were collected across the watershed, and composite samples were collected at the watershed outlet using a flow-proportional sampler. Samples were extracted for the herbicides alachlor [2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl) acetamide], ametryn [N-ethyl-N'-(1-methylethyl)-6-methylthio-1,3,5-triazine-2,4-diamine], atrazine [6-chloro-N-ethyl-N'-(1-methylethyl)-1,3,5-triazine-2,4-diamine], cyanazine [2-([4-chloro-6-(ethylamino)-1,3,5-triazin-2-yl]amino)-2-methyl propanenitrile], and metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl) acetamide]. Herbicides we re detected in 15% (n = 415) of the grab samples with atrazine, cyanazine, and metolachlor detected in 3% to 6%, while alachlor and ametryn were detected in 1% of the samples. The mean stream water herbicide concentrations in grab samples were < 0.9 microgram L-1. Herbicides were detected during all four seasons, with most detections occurring during the summer. The low number of herbicide detects and low total mass of these five herbicides exported from the watershed (<0.01% of herbicide applied) suggests that the five investigated herbicides have had a minimal influence on the quality of water exiting this watershed.