Movement of nonionic organic chemicals in agricultural soils

During the last decade, it has been reported that groundwater, surface water, food crops, livestock, and human tissue have all been contaminated with organic chemicals. Although much of the early work focused on pesticides, more recent studies have shown that a wider range of anthropogenic organic chemicals, many of which are designated as priority pollutants, also have been detected. Clearly, the movement of these chemicals through soil governs their potential to be transferred into water courses and foodchains. This review presents an overview of recent advances in sorption/desorption and transport phenomena. Theories currently being invoked to explain the mechanisms of sorption/desorption are discussed and their classification and numerical characterization are described. Water movement and its implications for solute transport are discussed, with emphasis being placed on the importance of soil structure. Finally, the impact of intrinsic factors, such as spatial and temporal variability of weather and climate and the natural heterogeneity of soil physico‐chemical properties, and extrinsic factors, such as cultivation technique, sludge application, drainage, irrigation, and crop residue disposal, on the persistence and movement of organic chemicals are evaluated. Emphasis is placed on behavior at the field scale and, whenever possible, recent examples from the literature are discussed.