Fate and Transport of Pesticides in the Ground Water Systems of Southwest Georgia, 1993–2005

Abstract

Modern agricultural practices in the United States have resulted in nearly unrivaled efficiency and productivity. Unfortunately, there is also the potential for release of these compounds to the environment and consequent adverse affects on wildlife and human populations. Since 1993, the National Water-Quality Assessment (NAWQA) program of the U.S. Geological Survey has evaluated water quality in agricultural areas to address these concerns. The objective of this study is to evaluate trends in pesticide concentrations from 1993-2005 in the surficial and Upper Floridan aquifers of southwest Georgia using pesticide and pesticide degradate data collected for the NAWQA program. There were six compounds-five herbicides and one degradate-that were detected in more than 20% of samples: atrazine, deethylatrazine (DEA), metolachlor, alachlor, floumeturon, and tebuthiuron. Of the 128 wells sampled during the study, only eight wells had pesticide concentrations that either increased (7) or decreased (1) on a decadal time scale. Most of the significant trends were increasing concentrations of pesticides in older water; median pesticide concentrations did not differ between the surficial and Upper Floridan aquifers from 1993 and 2005. Deethylatrazine, in the Upper Floridan aquifer, was the only compound that had a significant change (increase) in concentration during the study. The limited number of wells with increases in pesticide concentrations suggest that ground-water sources of these compounds are not increasing in concentration over the time scale represented in this study.

Estimating nitrate concentrations in groundwater at selected wells and springs in the surficial aquifer system and Upper Floridan aquifer, Dougherty Plain and Marianna Lowlands, Georgia, Florida, and Alabama, 2002-50

“…Frick and others (1996) described nitrogen sources in the lower ACFB. Groundwater quality in the lower ACFB also was described in Frick and others (1998), Frick and Dalton (2007), and Dalton and Frick (2008).…”

Methods for evaluating temporal groundwater quality data and results of decadal-scale changes in chloride, dissolved solids, and nitrate concentrations in groundwater in the United States, 1988-2010

“…Analysis of the short-term variation in water quality (within-year variability) for NAWQA trends data was conducted by Rosen and others (2008). Additional regional trend studies of data from the program were conducted by Frans (2008), Burow and others (2008), Debrewer and others (2008), Paschke and others (2008), Saad (2008), and Dalton and Frick (2008).…”

The quality of our Nation's waters: water quality in the Upper Floridan aquifer and overlying surficial aquifers, southeastern United States, 1993-2010

“…(14) Use of the Floridan aquifer system has increased substantially since the mid- In Georgia, agriculture is most extensive in the southwestern part of the State, and irrigation has increased with the introduction of center pivot systems in the 1970s. (15) In 2004, irrigation was used on almost 40 percent of the cropland in the study area in Georgia, which has greatly increased crop productivity and helped agriculture play a major role in the regional economy. (9) Crop types planted in the study area have changed from a mostly corn and peanut rotation in the 1970s to mostly cotton and peanuts.…”

“…(9) Crop types planted in the study area have changed from a mostly corn and peanut rotation in the 1970s to mostly cotton and peanuts. (15) Large quantities of groundwater withdrawals from the Floridan aquifer system have caused extensive waterlevel drawdowns and saltwater intrusion in several areas.…”