Partitioning, desorption, and dechlorination of a PCB congener in sediment slurry supernatants

Partitioning and desorption played specific roles in the dechlorination of 2-chlorobiphenyl (2-CIBP) in sediment slurry supernatants, which are suspensions of dissolved organic matter (DOM). In short-term experiments, the partition coefficient (Kp) was related to the apparent dechlorination rate constant. The Kp value (160 L g(DOC)(-1)), which is independent of the DOM concentration, was determined based on the decrease of the apparent rate constant with the increase of the DOM concentration. In the long-term experiments, the overall rate of dechlorination can be described with a two-compartment model. The time constant for the sediment compartment was related to Kp and the desorption rate constant (k(d)). The k(d) value (0.21 h(-1)) was determined based on the decrease of the time constant values with an increasing DOM concentration. The use of DOM suspensions allowed a short time for equilibrium. Separation of the aqueous and DOM phases was not needed due to the dechlorination of 2-CIBP. The fundamental relationships between overall dechlorination rate constant and properties of the contaminant and sediment were established.