Persistence and bioavailability of hydrophobic organic compounds in the environment

Abstract

The extensive use of hydrophobic organic compounds such as pesticides, petroleum hydrocarbons, solvents, and so on has resulted in widespread environmental contamination, either by broad use or by improper disposal or other unintentional releases. These organic contaminants become progressively persist in the environments and hence less available to living organisms and extraction. This phenomenon has been termed aging or sequestration, and widely observed with many hydrophobic organic compounds in soil, aquifer, and sediment. As a result of aging, remediation efforts for cleaning up organic chemical-contaminated sites have been challenged in removing so called aged or nonextractable residues which are not practically (bio) degraded or extracted. Some portion of persistent organic compounds may still be present in a site of interested where extensive remedial efforts have been applied. Data collected so far demonstrate that aged fractions of toxic pollutants behave much differently from unaged fractions in the environment so that they do not exhibit the chemicals' inherent toxicity. Biodegradation is one of the major mechanisms by which organic contaminants are transformed, immobilized, or mineralized in the environment. A clear understanding of the major processes that affect the interactions between hydrophobic organic contaminants, microorganisms, and environmental matrix is thus important for determining persistence of the compounds, for predicting in situ transformation rates, and for developing site remediation programs. In this review, therefore, we will discuss some of the major factors governing biodegradation and bioavailability of hydrophobic organic contaminants in the environment.