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 contamin ated with organic chemicals. Although much of the early work focused o n pesticides, more recent studies have shown that a wider range of ant hropogenic organic chemicals, many of which are designated as priority pollutants, also have been detected. Clearly, the movement of these c hemicals through soil governs their potential to be transferred into w ater courses and foodchains. This review presents an overview of recen t advances in sorption/desorption and transport phenomena. Theories cu rrently 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 transpo rt 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 hetero geneity of soil physicochemical properties, and extrinsic factors, suc h 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 s cale and, whenever possible, recent examples from the literature are d iscussed.