Water and Soil Pollution

Three components of the biosphere, soil, air, and water, can serve as toxicological sinks. These are often considered separately, but it should be obvious that they function as an integrated system. Thus, rain will transfer toxicants to soil and water, and evaporated surface water, and soil as airborne dust, can move them back into the air, where they may be transported over great distances by wind. Moreover, runoff from the soil, sewage, and industrial discharge are the main sources of water contamination. Seepage into deep aquifers from soil and surface water also may occur, and freshwater reservoirs are connected to the sea by rivers and estuaries. Thus, while this chapter tends to focus on water, both as an essential resource for human consumption and as marine and aquatic ecosystems, this should not detract from an understanding of the integrated nature of the biosphere. Soil often becomes the repository for our most toxic waste products and the consequences of this are touched upon later in this chapter. Chemicals may also enter foodstuffs grown in contaminated soil, and the spraying of crops with pesticides has been a matter of considerable public concern.