Modeling and assessment of polychlorinated biphenyls contamination in soil at a burial site of power capacitors

Numerous industrial or burial sites contaminated by persistent organic pollutants such as polychlorinated biphenyls (PCBs) and pesticides were discovered in China recently. Due to improper choice of technology, many remediation cases had cost too much; however, failed to attain expected goals. In this study, the distribution and transport of PCBs at a burial site were investigated using tested PCBs concentration in order to support the choice of remediation technology and estimate the remediation results. Site characterization was carried out in order to investigate the hydrogeological condition and PCBs pollution nearby the capacitor burial site located in Shanxi, China. Results of PCBs measurement indicated that the proportion of contaminated soil with concentration above 500 mg/kg is 7.8 % and the value for soil with concentration between 50 and 500 mg/kg is 18.0 %. Considering adsorption and biodegradation, the two-dimensional PCBs transport model was established based on advection-dispersion equation. The model calibration showed a good agreement between measured and computed values, indicating the feasibility of this model used for predicting the transport and disappearance of PCBs in soil. Results of 100 years' simulation demonstrated the slow migration and biodegradation of PCBs. Simulations were conducted for before and after remediation scenarios. Comparison of the results indicates that the remediation alternatives of excavation-incineration and thermal desorption have successfully removed most of the organics and thus reduced the environmental risk to a low level.

Keywords
Polychlorinated biphenyls (PCBs); Remediation; Soil-water distribution; Transport modeling