Abstract

Activated carbon (AC) is currently being used to treat polychlorinated biphenyl (PCB) contaminated
 field sediment. In the presence of sediment, the sorption capacity of AC for PCBs can be reduced. In
 this study, sorption attenuation of AC is investigated using previously published data from 5
 sampling sites where reductions in aqueous concentrations caused by AC amendment have been
 reported. AC-water partitioning coefficients (KAC_clean_water) were determined at a relevant PCB
 concentration in clean water using polyoxymethylene (POM) passive samplers. Logarithmic ACwater
 partitioning coefficient values ranged from 7.39 to 9.59 for trichlorinated to pentachlorinated
 congeners. These AC-water partitioning coefficients were used in a numerical model to predict
 expected reductions in aqueous concentrations. Results reveal an overprediction of actual
 reductions by a median factor ranging from 2.5 to 5.6. To obtain an estimate of AC sorption
 attenuation, an AC-water partitioning coefficient more representative of sediment conditions
 (KAC_apparent) was fitted via the model based on the observed reductions in aqueous concentrations.
 On average, median KAC_apparent values of individual PCB congeners were smaller than KAC_clean_water
 values by 1.08 log units, or a factor of 12, with corrections ranging from 0.1 to 2.3 log units. The
 main controls on the reduction in sorption of PCBs to AC are PCB physico-chemical properties and
 AC amendment variables. Generally AC sorption attenuation increased with PCB hydrophobicity and
 decreased with increasing AC-sediment contact time and AC dose.

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