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Occurrence and Transport of Acetochlor in Streams of the Mississippi River Basin
Author(s) -
Clark G. M.,
Goolsby D. A.
Publication year - 1999
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq1999.00472425002800060014x
Subject(s) - acetochlor , alachlor , metolachlor , acetanilide , atrazine , streams , acetamide , hydrology (agriculture) , environmental science , surface runoff , growing season , chemistry , agronomy , pesticide , zoology , biology , ecology , geology , computer network , geotechnical engineering , organic chemistry , computer science
The herbicide acetochlor [2‐chloro‐ N ‐(ethoxymethyl)‐ N ‐(2‐ethyl‐6‐methylphenyl) acetamide] was first used on corn ( Zea mays L.) in the USA during the growing season of 1994. By 1996, it was the third most heavily used corn herbicide in the midwestern USA. During the growing season of 1997, 78% of 375 samples collected at 32 stream sites in the Mississippi River Basin contained detectable concentrations of acetochlor. However, concentrations in only 2% of the samples exceeded 2/µg/L, the maximum annual average concentration allowable in public water supplies derived primarily from surface water. The largest acetochlor concentrations were detected in streams draining basins in parts of Illinois, Indiana, and Iowa. The median concentration of acetochlor in streams was about 10% that of atrazine (6‐chloro‐ N ‐ethyl‐ N ‐isopropyl‐1,3,5‐triazine‐2,4‐diamine), about 25% that of metolachlor [2‐chloro‐ N ‐(2‐ethyl‐6‐methylphenyl)‐ N ‐(2‐methoxy‐1‐methylethyl) acetamide], about 50% that of cyanazine [2‐[[4‐chloro‐6‐(ethylamino)‐l,3,5‐triazin‐2‐yl]amino]‐2‐methylpropionitrile], and about threefold that of alachlor [2‐chloro‐2′,6′‐diethyl‐ N ‐(methoxymethyl) acetanilide]. Load estimates indicate that, during the growing season of 1997, agricultural subbasins draining areas of Illinois, Indiana, and Iowa contributed about 37 000 kg, or 74%, of the 50 000 kg of acetochlor measured in streams of the Mississippi River Basin.