Afbraak van Organische Halogeen Verbindingen in Anaeerobe Sediment-Water Systemen (Reductive Dehalogenation of Organic Pollutants in Anaerobic Sediments)

摘要

A scientific exchange program between the section Environmental Chemistry of the Laboratory EMD (RIVM) and the Environmental Research Laboratory (ERL) of US-EPA, Athens (GA) is reported. The objective of the research project was reductive dehalogenation of organic pollutants in anaerobic sediments. The degradation of chlorinated aromatic compounds in anaerobic water-sediment systems was investigated. The most relevant degradation process is reductive replacement of chlorine with hydrogen atoms at the aromatic ring. Dichloroanilines (DCA's) were investigated of which the 3,4-isomer, a metabolite of widely used herbicides, was converted to 3-chloroaniline after a lag period of 3 weeks. After the sediment was acclimated to mineralize 2,4- or 3,4-dichlorophenol, it proved highly active in transforming 2,4- and 3, 4-DCA into 3- and 4-chloroaniline respectively. Cross-adaptation was not observed between chlorinated phenols and anilines on one side and chlorinated benzoic acids on the other. New was also that reductive dechlorination of 2,4-dichlorobenzoic acid was found. Without microbial activity the reaction rate is virtually zero for all chlorinated aromatic compounds studied. The (first order) rate constant of 18 halogenated hydrocarbons ranging several orders of magnitude was evaluated and correlated to different structure parameters. The QSAR could be made operative for the prediction of the abiotic reduction rate of any given halogenated hydrocarbon in a given sediment or aquifer system.