Polychlorinated Biphenyls (PCBs) in Dissolved and Particulate Phases of Urban Stormwater before and after Bioretention Treatment

The presence of dissolved polychlorinated biphenyls (PCBs) and PCBs associated with particle influent and effluent samples from a bioretention stormwater control measure was studied. The Kaplan-Meier survival procedure was used to sum PCB congeners for concentrations below detection limits. For influent samples, concentrations of dissolved PCBs ranged from 66 +/- 17 to 752 +/- 23 ng/L, and the concentration decreased by 66-93% in the effluent after bioretention treatment to 20.8 +/- 5.1 to 53.0 +/- 10.0 ng/L. The concentrations of total PCBs in the particulate phase of the influent ranged from 176 to 649 ng/g (median of 316 ng/g). The particle-based PCB concentration decreased by 99.6% in one event due to bioretention treatment. The overall PCB load reduction via bioretention treatment is estimated at 82-85%. 3,3'-Dichlorobiphenyl (PCB 11) was detected in all stormwater influent samples and constituted 3-20% of the total dissolved PCB concentration. Particulate concentrations of PCBs ranged from only 3 to 15% of the total PCB mass in stormwater samples, showing that dissolved PCBs are important and must be considered in stormwater loads. Bioretention systems are effective infrastructure facilities for the reduction of PCB loads, although additional treatment may be needed to address dissolved PCBs.