Heavy Metals in the Soil-Water-Plant System

Abstract

Heavy metals, like any other chemical element in a terrestrial ecosystem, may be dissolved in the soil solution, adsorbed onto colloidal surfaces, occluded into soil minerals, precipitated with other components in soil, or incorporated into biological materials. These processes are influenced by many factors, such as soil pH, Eh, temperature, organic matter content, mineralogical compositions as will as the type and concentration of other dissolved constituents. Furthermore, the chemical behavior of a heavy metal in the soil-water-plant system is affected by interactions with other elements and/or soil components and the environmental conditions. The knowledge of the interactions may lead to a better understanding of the relationship between crop yield and quality and the nutrient level of soils (Ohno and Grunes, 1985). Research on these interactions should attract more attention because it relates to ecosystem balance, environment qualities and human health (Chen and Zheng, 1992; 1994b). This, however, has not been the case until recently. To illustrate the effects of interactions on chemical behavior of the elements in soil-water-plant system, some results obtained recently in laboratory and greenhouse studies by our research group were chosen (Zheng and Chen 1990; Chen et al.,1991a,b; Chen and Zheng, 1994a,b; Zang et al.,1987, 1989).