Persistence and bioavailability of hydrophobic organic compounds in the environment

Abstract

The extensive use of hydrophobic organic compoundssuch as pesticides, petroleum hydrocarbons, solvents, and so onhas resulted in widespread environmental contamination, eitherby broad use or by improper disposal or other unintentionalreleases. These organic contaminants become progressively persistin the environments and hence less available to living organismsand extraction. This phenomenon has been termed aging orsequestration, and widely observed with many hydrophobicorganic compounds in soil, aquifer, and sediment. As a result ofaging, remediation efforts for cleaning up organic chemical-con-taminated sites have been challenged in removing so called gedor nonextractable residues which are not practically (bio) degradedor extracted. Some portion of persistent organic compounds maystill be present in a site of interested where extensive remedialeforts have been applied. Data colected so far demonstrate thataged fractions of toxic pollutants behave much differently fromunaged fractions in the environment so that they do not exhibit thechemicals' inherent toxicity. Biodegradation is one of the majormechanisms by which organic contaminants are transformed,imobilized, or mineralized in the environment. A clear under-standing of the major processes that affect the interactionsbetwen hydrophobic organic contaminants, microorganisms, andenvironmental matrix is thus important for determing persis-tence of the compounds, for predicting in situ transformationrates, and for developing site remediation programs. In thisreview, therefore, we will discuss some of the major factors gov-erning biodegradation and bioavailability of hydrophobic organiccontaminants in the environment.