such as "Introduction", "Conclusion"..etc
MADISON, WI, JUNE 23, 2008– Numerous
studies over the past four decades have established that pesticides,
which are typically applied at the land surface, can move downward
through the unsaturated zone to reach the water table at detectable
concentrations. The downward movement of pesticide degradation
products, formed in situ, can also contribute to the contamination of
ground water. Once in ground water, pesticides and their degradation
products can persist for years, depending upon the chemical structure
of the compounds and the environmental conditions.
at the U.S. Geological Survey (USGS) investigated the occurrence of
selected pesticides and their degradation products in ground water
during a study funded by the USGS National Water-Quality Assessment
(NAWQA) Program. Specifically, the authors examined several of the
factors that can influence the likelihood with which pesticides and
their degradation products are detected in shallow ground
water—including oxidation-reduction (redox) conditions and ground-water
residence times—at four study sites across the United States. Results
from the study were published in the May-June 2008 issue of the Journal of Environmental Quality.
study revealed that the pesticides and degradation products detected
most frequently in shallow ground-water samples from all four areas
were predominantly from two classes of herbicides—triazines and
chloroacetanilides. None of the insecticides or fungicides examined
were detected in ground-water samples. In most samples, the concentrations of the pesticide degradation products greatly exceeded those of their parent compounds. Pesticides
or their degradation products were detected most commonly in ground
water that recharged between 1949 and 2004, and in monitoring wells
spanning the full depth range (about 2 to 52 m) examined—from the
shallowest to the deepest wells—in all four study areas. Comparisons
of pesticide concentrations with a variety of environmental variables
indicated that redox conditions, ground-water residence times, and the
concentrations of dissolved oxygen and excess nitrogen gas from
denitrification (the breaking down of nitrogen compounds such as
nitrate) were all important factors affecting the concentrations of
pesticides and their degradation products in all four ground-water
four sites selected for this study were located in agricultural
landscapes in Maryland, Nebraska, California, and Washington. They were
also selected for variability in overall land use, crops grown,
climate, agricultural practices, irrigation, geohydrologic settings,
and redox conditions. During the spring of 2004, water samples were
collected from a network of 59 shallow single or clustered monitoring
wells and analyzed for the occurrence of 45 pesticides and 40 pesticide
degradation products, including herbicide, insecticides, and fungicides.
Steele, senior author for this study, stated “Atrazine and its
degradation product deethylatrazine both persisted in similar amounts
at the Nebraska site, but in water samples from the other three study
sites, there was little change with apparent age of water as the
fraction as deethylatrazine generally exceeded 80% of the sum of
atrazine and deethylatrazine. On the other hand, in three of the four
areas studied (Washington excluded because it did not have any
detections of metolachlor or its degradation products), the proportion
of metolachlor in ground water was far less than that for its
News release provided by Soil Science Society of America (SSSA) on June 23, 2008.
The full article is available for no charge for 30 days following the date of this summary. View the abstract at http://jeq.scijournals.org/cgi/content/abstract/37/3/1116.
The Soil Science Society of America (SSSA)
is a progressive, international scientific society that fosters the
transfer of knowledge and practices to sustain global soils. Based in
Madison, WI, and founded in 1936, SSSA is the professional home for
6,000+ members dedicated to advancing the field of soil science. It
provides information about soils in relation to crop production,
environmental quality, ecosystem sustainability, bioremediation, waste
management, recycling, and wise land use.
SSSA supports its
members by providing quality research-based publications, educational
programs, certifications, and science policy initiatives via a
Washington, DC, office. For more information, visit www.soils.org.
is the founding sponsor of an approximately 5,000-square foot
exhibition, Dig It! The Secrets of Soil, opening July 19, 2008 at the
Smithsonian's National Museum of Natural History in Washington, DC.
Enter the code exactly as it appears. All letters are case insensitive, there is no zero.