Pesticide Residues in Surface Water and Groundwater

Agricultural food production accounts for about 70%–80% of the total pesticide use. Application of pesticides has greatly increased crop yields and reduced losses. The majority of agricultural pesticides are herbicides. Their widespread use has reduced the extent of mechanical cultivation of soil in the control of weeds. However, with respect to human exposure through food, insecticides and fungicides are the most important pesticides because they are applied shortly before or after harvesting. Herbicide residues are the most frequently detected residues in environmental waters (Manahan 2001). The temporal and spatial changes of pesticide concentration in surface water are related to the timing of CONTENTS 9.1 Sources of Pesticide Residues in Water ........................................................................... 259 9.1.1 Pesticide Entry Routes into Water ....................................................................... 261 9.2 Fate of Pesticides in Water ................................................................................................ 263 9.3 Regulatory Issues and Levels of Pesticide Residues in Surface Water and Groundwater ...................................................................................................................... 268 9.3.1 Regulatory Issues Concerning Pesticide Residues in Surface Water and Groundwater .......................................................................................................... 268 9.3.2 Levels of Pesticide Residues Found in Surface Water and Groundwater ...... 270 9.4 Removal of Pesticide Residues During Drinking Water Production ......................... 272 9.4.1 Water Treatment Technology ............................................................................... 273 9.5 Methods for Monitoring Pesticide Residues in Water .................................................. 276 9.5.1 Sample Preparation ............................................................................................... 276 9.5.1.1 Solid-Phase Extraction ............................................................................277 9.5.1.2 Recent Trends .......................................................................................... 282 9.5.2 Analyte Detection .................................................................................................. 282 9.5.2.1 GC Detection Methods ........................................................................... 282 9.5.2.2 LC Detection Methods ...........................................................................283 9.5.2.3 Comparison Between GC and LC Methods ........................................285 9.5.2.4 Recent Trends .......................................................................................... 286 Acknowledgments ...................................................................................................................... 287 References ..................................................................................................................................... 287 its seasonal application. It is more frequent and concentrated during late spring and early summer months, following the spring application, and diminishes signi cantly in fall and winter (Pereira and Hostettler 1993; Bradford et al. 2010). For instance, it was determined that almost 80% of the annual herbicide load to the Gulf of Mexico occurred during the growing season, that is, from May to August (Clark and Goolsby 2000).