Global Perspectives and Risk Assessment

This chapter presents some thoughts on the function of land as a receptor and emitter of toxic substances. The former function is an anthropogenic imposition on the land and its soils. Soils did not evolve to serve the role as a storage bin for toxic persistent, chemicals, at least not at the levels of input experienced in most industrialized areas over the last 100 years. The latter function of soil as an emitter is mostly determined by natural processes in the soil. One perspective on this function is that it serves to purge the soil of toxic materials, and so can be viewed as a useful function from the point of view of improving soil quality. On the other hand, in the process of purging itself of polluting substances, such substances may be passed on to vegetation, or possibly transferred to groundwaters. Since such transfers are guided by the natural laws of soil chemistry and physics, human control over the outcomes are limited. In light of the above, major questions arise regarding the management of these soils; i.e., the range of available options for insuring their long-term sustainability, and controlling soil emissions so that they do not degrade groundwaters, or toxify flora and fauna beyond acceptable limits.