Estimating the long term leaching potential of PCBs in soil

Polychlorinated Biphenyls (PCBs) are a group of man-made organic chemicals known as chlorinated hydrocarbons. PCBs were banned in 1979 due to its toxicity and persistence in the environment. Variations of PCBs were determined in soils and plants. Degradation of PCB Aroclors and congener patterns were investigated from known contaminated site at a former Military Air Base. PCB concentrations ranged between 17 - 1,040 µg L-1 at 0 - 0.5 m depth, between 36 - 898 µg L-1 at 1.0 - 1.5 m depth, between 20 - 73 µg L-1 at 4 m depth and 21 µg L-1 at 8 m depth. There is also a negative correlation between the mean of the Toxicity Characteristic Leaching Procedure (TCLP) of PCBs versus the sampling depth. Linear regression analyses were used to determine the correlation of the factors such as depth, Octanol/Water Partition Coefficient (Kow) and solubility affected Soil/Water Distribution Coefficient (Kd). Effects were found only when the soil depth is at 0.3 - 0.5 m (at 95% confidence level). Kd is positively correlated with Kow while Kd has some level of negative correlation with solubility. No effect was found at 1.0 - 1.5 m, 4.0 m, and 8.0 m. Organic Carbon/Water Partition Coefficient (Koc) showed high results exceeding the log Koc criteria of 4.5; as a result, this is now a matter of concern on the potential adverse effects of the substance on terrestrial organisms within its vicinity.