Effects of PH, Electrolytes and Microbial Activity on the Mobilization of PCB and PAH in a Sandy Soil

Abstract

In the terrestrial environment, soils are the most important sinks for many anthropogenic xenobiotics. Airborne or otherwise introduced hydrophobic organic compounds such as polycyclic aromatic hydrocarbons (PAH) or polychlorinated biphenyls (PCB) accumulate mainly in the organic topsoils due to their high affinity for organic matter and their low water solubility. The further fate of these substances is dependent on their chemical structure and may include volatilization as the major pathway for the loss of lower chlorinated biphenyls from sewage sludge-treated soils (Alcock et al., 1993). Well documented is the biochemical degradation of low molecular weight PAHs in soils by autochthonous micro flora (Wild et al., 1990) or by introduced specialists such as certain genera of white rot fungi (Barr and Aust, 1994, Kästner and Mahro, 1996). However, 5- and 6-ring PAHs and PCBs seem to be largely resistant against biochemical attacks in the soil environment and are therefore regarded as highly persistent (Wild et al., 1990, Alcock et al., 1993). Furthermore, the bioavailability of organic chemicals, which is a prerequisite for degradation, can be greatly reduced due to incorporation into the macromolecular structures of humus molecules and the formation of so-called bound residues.