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Pesticide Fate and Transport throughout Unsaturated Zones in Five Agricultural Settings, USA

^a U.S. Geological Survey, 1730 East Parham Road, Richmond, VA 23228
^b U.S. Geological Survey, P.O. Box 25046, MS 407, Lakewood, CO 80225-0046
^c U.S. Geological Survey, 5231 South 19 Street, Lincoln, NE 68512
^d U.S. Geological Survey, 5957 Lakeside Boulevard, Indianapolis, IN 46278
^e U.S. Geological Survey, 934 Broadway, Suite 300, Tacoma, WA 98402

View larger version (21K): [in this window] [in a new window]   Fig. 1. Concentrations of atrazine and deethylatrazine (DEA) in solids and water at Maryland Site M22. Shaded zone at 9.7 m indicates range of fluctuations in depth of water table below land surface over time. See Table 3 footnotes for sampling dates.

View larger version (23K): [in this window] [in a new window]   Fig. 2. Concentrations of metolachlor, atrazine, and degradates over time at Nebraska Site N22b, located 7 m below land surface. DEA, deethylatrazine; ESA, ethanesulfonic acid; OXA, oxanilic acid.

View larger version (17K): [in this window] [in a new window]   Fig. 3. The occurrence of the target pesticides in the unsaturated zone as a function of soil half-life and organic carbon–normalized distribution coefficient (Koc) for all parent pesticides that were applied in the counties of the study sites in Indiana (IN), Maryland (MD), Nebraska (NE), and Washington (WA), based on data gathered by Nakagaki and Wolock (2005).

View larger version (18K): [in this window] [in a new window]   Fig. 4. Metolachlor ethane sulfonic acid (ESA) fraction (Eq. [1]) versus lysimeter depth at two Maryland sites. (A) Site M20. (B) Site M22. Different data points at each depth represent different sampling dates.

View larger version (21K): [in this window] [in a new window]   Fig. 5. Metolachlor ethanesulfonic acid (ESA) fraction (Eq. [1]) versus time at two study sites. (A) Nebraska Site N23. (B) Maryland Site M20.

View larger version (18K): [in this window] [in a new window]   Fig. 6. Comparison of concentrations of metolachlor oxanilic acid (OXA) and metolachlor ethanesulfonic acid (ESA) at three study sites: (A) Nebraska East Site N22, (B) Nebraska East Site N23, and (C) Maryland Site M22.