U.S. Geological Survey Toxic Substances Hydrology Program--Proceedings
of the Technical Meeting, Colorado Springs, Colorado, September 20-24, 1993,
Water-Resources Investigations Report 94-4015
  
Fate and Transport of Atrazine at the Plains, Georgia, Ground
Water Study Site
by
R. A. Leonard (U.S. Department of Agriculture, Agricultural Research
Service, Southeast Watershed Research Laboratory, Tifton, Ga.), L.R. Marti
(U.S. Department of Agriculture, Agricultural Research Service, Southeast
Watershed Research Laboratory, Tifton, Ga.), D.W. Hicks (U.S. Geological
Survey, Water Resources Division, Atlanta, Ga.), and J.B. McConnell (U.S.
Geological Survey, Water Resources Division, Atlanta, Ga.)
Abstract
Cooperative research between the U.S. Geological Survey, U.S. Department
of Agriculture, Agricultural Research Service, and U.S. Environmental Protection
Agency was initiated in 1986 near Plains, Georgia, to define processes that
affect movement and fate of agricultural chemicals and to establish a common
comprehensive data base for development and testing of mathematical models.
Data from one crop cycle (mid-March 1992 to mid-March 1993) are summarized
to illustrate the fate and present state of atrazine in the system after
four annual treatments at normal application rates for corn. In 1992, parent
atrazine dissipated in the root zone with a half-life of about 18 days.
The atrazine metabolites, desethylatrazine (DEA) and desisopropylatrazine
(DIA) accumulated in the root zone to a maximum 27 days after application;
DEA was the primary metabolite. The maximum DEA/atrazine ratio was 0.6 40
days after atrazine application. After crop harvest in mid-July 1992, atrazine,
DEA and traces of DIA were detected throughout the unsaturated zone to depths
of 8.7 meters. Because the area had been treated with atrazine during the
previous 3 years, the atrazine found could not be associated with a particular
application. By March 1993, atrazine in the unsaturated zone had decreased
from an estimated 360 grams per hectare to 100 grams per hectare. Atrazine
and DEA in ground water, at the time of sampling, were at greater concentrations
downgradient from the treated area, with the maximum concentrations about
60 meters downgradient from the treated plot boundary. Traces of atrazine
and DEA were detected 280 meters downgradient from the plot. DEA/atrazine
ratios were slightly higher in ground water compared to the unsaturated
zone, possibly indicating continued transformation along the ground-water
flow path.
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