Spatial and temporal distribution of PCBs in the reclamation soils at Changjiang Estuary

This paper mainly studies the reclamation soils at Changjiang Estuary from the Changjiang River silt and the sediment areas accumulate annually. It takes the Chongming Island of Shanghai City as sampling regions and PCBs as the target analyte. The reclamation areas are divided to 5 time segments from 1974 to the present. We took the surface (0~15 cm) and deep (100 cm) soils at 5 spots respectively, which are located at separated time intervals of sediments. After sample pretreating through Soxhlet extraction and cleansing, we analyzed PCBs qualitatively and quantitatively by GC-MS, thereafter we can specify the distribution of PCBs concentration and composition characteristics. There are 35 PCB congeners detected in both the surface and deep soil samples. The concentration ranges of 35PCBs in the surface and deep soils are 1.95410-9~3.71610-9 and 2.64910-9~3.68510-9 respectively. The majority fraction of PCBs congeners in the reclamation soil samples are DiCBs and TetraCBs. In addition, the concentration of PCBs goes up till 1990s, and then goes down afterwards. Finally, we gave a brief analysis based on the Hierarchical Cluster analysis method. The results show that the polluting extent and pollutant source of the deep soils are proved to conform to those of the surface soils in the next time period.