Alachlor and Two Degradates of Alachlor in Ground And Surface Water, Southwestern Georgia And Adjacent Parts Of Alabama And Florida, 1993-2005
Frick, Elizabeth A.
Dalton, Melinda S.
MetadataShow full item record
Alachlor and Two Degradates of Alachlor in Ground And Surface Water, Southwestern Georgia And Adjacent P Ground- and surface-water samples have been collected in the Apalachicola–Chattahoochee–Flint River Basin (ACFB) and Georgia-Florida Coastal Plain (GAFL) study units since 1993 as part of the U.S. Geological Survey’s National Water-Quality Assessment Program (NAWQA) program. This paper focuses on the use and occurrence of the herbicide alachlor and two degradates of alachlor in several ACFB and GAFL NAWQA ground- and surface-water sampling networks within agricultural areas in southwestern Georgia and adjacent parts of Alabama and Florida. Alachlor was analyzed during cycle I (1993–2001 water years) and to date in cycle II (2002–2005) of NAWQA. Two degradates of alachlor—alachlor ethane sulfonic acid (alachlor ESA) and alachlor oxanilic acid (alachlor OA)—were analyzed in a subset of cycle II samples collected during water year 2002 and during May 2004. Although alachlor use in the study area declined from the 13th most used herbicide during 1992 to the 24th most used herbicide during 2002, alachlor was the third most frequently detected pesticide in ground water for 1993–2005 behind the more frequently used herbicides atrazine and metolachlor. Alachlor was the only pesticide analyzed during this study that exceeded a U.S. Environmental Protection Agency maximum contaminant level standard (2 micrograms per liter) or health-advisory level in ground-water samples collected within the study area. When analyzed, alachlor ESA and alachlor OA were typically detected more frequently and at higher concentrations than alachlor.