Vertical Distribution Characteristics Of Polychlorinated Biphenyls In Sediment And Soil From Coal Mining Subsidence Area

After the subsidence and water retention due to coal mining, the original terrestrial environment evolved into the aquatic environment, the soil before subsidence turned into the water sediment, and contaminants in soil also migrated and transformed. In view of the harmfulness of PCBs, study on distribution of PCBs in soil and sediment will have great significance to the further study of PCBs migration among different media. Therefore, this paper takes Yangzhuang coal-mining subsidence area as its study area to analyze and research the content of PCBs in soil and sediment, based on exploration of experimental scheme. Results are listed as follows:1. In order to ensure the precision and quality of the experimental data, the corresponding quality control and assurance are established in this paper, PCB65and PCB155were used as the surrogates to control the recovery. The average recovery rate of PCB56and PCB155(both are soil samples)respectively ranged from70.56%to128.4%and from77.7%to122.6%, while PCB65and PCB155(both are sediment samples) respectively ranged from80.5%to124.4%and from97.8%to126.1%.2. The detectable rate of PCBs in soil sample was100%; PCBs in soil samples at different depths were dominated by TriCB and PentaCB, the average contribution rates of TriCB and PentaCB were above70%; The general vertical distribution law of soil was not obvious, but that of various sampling sites was quite obvious.3. The detectable rate of PCBs in sediment sample was100%; PCBs in sediment samples at different depths were dominated by TriCB and PentaCB, the average contribution rates of TriCB and PentaCB was above85%; The horizontal distribution of PCBs in sediments at different depth was similar, and the concentration in the southeast area of water was higher than that in other area. The results showed that the sediment Ni lake itself had a great effect on the content of PCBs; PCBs content was relatively stable in sediment samples at different depths and reached an equilibrium state.4.CBs in sediment was higher than that in soil at the same depth, and more well-distributed.5. The concentration of TriCB in soil showed an uneven distribution in contrast with that in sediment, and was higher. Higher-chlorinated congeners can transfer from water to sediment more easilier because of the increasing number of chlorine atoms and reducing of water solubility, thus the concentration of PentaCB in sediment was higher than that in the sediment.6. The correlations among each lower-chlorinated PCBs of the soil and sediment samples were apparent, which showed their homology. There was a positive correlation between TriCB and OM because of the equilibrium state of the TriCB in sediment. The paper holds that TriCB and TetraCB of the research area came from the transformer oil and capacitor impregnant, while PentaCB came from the paint.