BIOGEOCHEMICAL CYCLES AND PROCESSES LEADING TO CHANGES IN MOBILITY OFCHEMICALS IN SOILS

There is a general lack of long-term field research showing the enviro nmental fate of soil contaminants after agricultural land is converted to other uses. One concern is that long-term changes in soil properti es induced by an alternative land use might cause a non-linear increas e in the solubility and mobility of soil chemical contaminants. If a f airly rapid increase in contaminant mobility is delayed for years, the n this event may be difficult to predict and to control. To help provi de insights to long-term fate of soil contaminants, this paper gives a n overview of some factors controlling their solubility and mobility. Because of their indefinite residence time in soils, heavy metals and other trace elements input to agricultural lands with soil amendments may pose the greatest (albeit undetermined) long-term threat. Certain macronutrients, especially N and P, and organic pesticides may have sh orter-term detrimental effects on water quality and the environment. I mportant properties influencing soil contaminant solubility and mobili ty are the type of contaminant (e.g., heavy metal cation, oxyanion, pe sticide), soil matrix composition (e.g., mineralogy and organic matter content), soil heterogeneity, pH, redox potential, and variations in dissolved organic matter concentration. By understanding the mechanism s of contaminant binding in the soil in relation to these properties, the long-term fate of contaminants is more predictable. (C) 1998 Elsev ier Science B.V.