Vital Soil Versus Contaminants

The vital soil gradually evolved after the formation of earth. Beyond the illusion of the day there should be awareness that recycling of elements is a phenomenon existing over billions of years. Whereas the anoxic processes are far older than the oxic ones and consequently have a longer history of evolution. The principle of the infallibility of nature in recycling of elements is also applicable for the biodegradation of organic contaminants. The history of environmental pollution, resulting in soil/sediment contamination, is relatively short. One of the first pollution affairs dates from the Roman period (Hong et al., 1996) and refers to heavy metals, the open smelting of ores. Since than non-optimal metal-processing industries resulted in heavy metal fallout, causing elimination of sensitive species in soils but also adaptation. Metal resistant grasses are Agrostis and Festuca (Ernst 1989), whereas Arabidopsis halleri became a hyper accumulator of Zn (Ernst, 2004). The soil microflora (Doelman et al., 1994) and the soil fauna (Hopkins, 1994) became affected in many ways. The soil contamination by organics is more recent and is mostly the result of mismanagement, such as overdoses of plant-protection chemicals as DDT. Since the early 1950s there is concern on those issues. The book Silent Spring (Carson, 1962) questioned the accumulation of DDT in food chains: birds of prey became well known victims. The relation between soil contamination and higher animals is qualitatively and quantitatively shown by Van den Brink (2004). Simultaneously those spillages became a source of inspiration to study their fate as microbial degradation. The anaerobic degradation pathways of oil compounds such as BTEX (Wilson et al., 1986) and of degreasing compounds, applied in the dry cleaning industry, were discovered and could be applied in in-situ remediation. Degradation rates and preferable degradation conditions became known. In table 1 some relevant historical events are mentioned.