Fate Processes of Chlorobenzenes in Soil and Potential Remediation Strategies: A Review

Chlorobenzenes (CBs) are a group of organic pollutants that pose a high environmental risk due to their toxicity, persistence and possible transfer in the food chain. Available data in literature show that CBs are detected in different environmental compartments such as soil, water, air and sediment. The widespread presence of CBs in the environment is related to their former extensive use in agriculture and industry. Some CBs are ranked in the list of priority pollutants by the Stockholm Convention, and their reduction or elimination from the environment is therefore of high importance. Environmental risk assessment of CBs requires knowledge on the role and importance of the main environmental fate processes, especially in soil. Furthermore, development of remediation strategies for reduction or elimination of CBs from the environment is related to the enhancement of fate processes that increase their dissipation in various environmental compartments. The main objectives of the current review were to present up-to-date data on fate processes of CBs in the soil environment and to explore possible remediation strategies for soils contaminated with CBs. Dechlorination of highly-chlorinated benzenes is the main degradation pathway under anaerobic conditions, leading to the formation of lower-chlorinated benzenes. Biodegradation of lower-chlorinated benzenes is well documented, especially by strains of adapted or specialized microorganisms. Development of techniques that combine dechlorination of highly-chlorinated benzenes with biodegradation or biomineralization of lower-chlorinated benzenes can result in useful tools for remediation of soils contaminated with CBs. In addition, immobilization of CBs in soil by use of different amendments is a useful method for reducing the environmental risk of CBs.