Movement and retention of polychlorinated biphenyls in a paddy field of WenTai area in China

Polychlorinated biphenyls (PCBs) are classified as priority pollutants by environmental agencies. A field investigation on polychlorinated biphenyls movement and retention in paddy field was conducted during 1993, 1997 and 1999 at the WenTai area. Soil, air and rice samples were analyzed. PCB concentrations in the soil showed a reducing trend with respect to time and depth. Most of the di-, tri-, and tetra-chlorinated PCB congeners showed significant decreases during the period, while the more highly chlorinated PCBs were more persistent in soil. The results of field investigation data showed that even though 6 years the PCB concentrations in two fields were far from reaching uniform. In addition, rice grown in the field appeared somewhat contamination by PCBs, but it was not likely subjected to concentrating PCBs from contaminated soil significantly. It was shown that the PCB concentrations in rice samples were not directly proportional to their concentrations in soil. Principal component analysis was performed with the standardized relative abundance of PCBs in the samples. All these observations indicated that the pattern of PCBs in soil cannot be considered to reflect the original pollution source. (C) 2002 Elsevier Science B.V. All rights reserved.