Comparative Study On Persistent Organic Pollutants In Columnar Soil And Sediment In Changeable Ecological Environment

Persistent organic pollutants(POPs)mostly have such characteristics as biotoxicity,mobility,accumulation,persistence as well as the effects of carcinogenesis,teratogenesis and mutagenesis.They are extensively distributed in environmental media,posing huge impacts to humans and ecological environment.Now POPs have become priority in global governance.This research adopts the method of Gas Chromatography-Mass Spectrometer(GC-MS),chooses Yangzhuang and Xieqiao,two typical subsidences in Huainan mines,a changeable ecological encironment that evolves from terrestrial environment at the very beginning to aquatic environment and takes the soil before the coal mines were subsided,over 14 kinds of polychlorinated biphenyls in the bottom sediments of the waters after subsidence and the 16 kinds of polyaromatic hydrocarbons which are in priority control of Environmental Protection Agency(EPA)as the subjects to makes systematic comparative study on the characteristics of lateral and longitudinal distribution,material composition,pollution source and influence factor of POPs in columnar and different layers under changeable ecological environment and make a assessment of the pollution level of POPs.This research aims to understand the pollution characteristics and potential risks of typical POPs.The main research results are listed below:Though establishing a mature method of pretreatment,extraction and purification,qualitative analysis and quantitative analysis are conducted in the detection of POPs in the soil and sediments of subsidence areas under changeable ecological environment.The quality of process is controlled and guaranteed.The detection method has a high recovery rate,conforming to the requirements of some environment analysis like EPA.Under changeable ecological environment,the rest of PCB monomers are all detected except PCB105 PCB153 and PCB180 in the soil of Yangzhuang subsidence.The detection rate of the 16 kinds of PAHs in subsidence area is 100%.Based on the statistic analysis of the detection results of PCBs and PAHs in different layers in the soil and sediments of different subsidences under changeable ecological environment,the ΣPCBs concentration of soils in different layers of Yangzhuang subsidence is in the range of 1.052-19.252 ng/g dw;the ΣPCBs concentration of sediments in different layers is in the range of 1.024-62.514 ng/g.TheΣPCBs concentration of soils in different layers of Xieqiao subsidence is in the range of 1.244-27.774 ng/g;the ΣPCBs concentration of sediments in different layers is in the range of 0.239-12.622 ng/g.The ΣPAHs concentration of soils in different layers of Yangzhuang subsidence is in the range of 42.113-22149.023 ng/g;the ΣPAHs concentration of sediments in different layers is in the range of 43.968-7644.210 ng/g.The ΣPAHs concentration of soils in different layers of Xieqiao subsidence is in the range of 17.809-1617.749 ng/g;the ΣPAHs concentration of sediments in different layers is in the range of 35.673-264.553 ng/g.Based on the comparison of the pollution surveys of other districts,the pollutions of PCBs and PAHs in the soil and sediment of subsidence area is in medium low level.The pollution of POPs in the soil and sediment of Yangzhuang subsidence area is more severe than that in the soil and sediment of Xieqiao subsidence.Yangzhuang subsidence suffers from more human disturbance.The pollution level of PCBs and PAHs in the sediment of subsidence area is higher than that in the soil.By drawing the Arcgis interpolation and box-type maps of PCBs and PAHs in columnar in the soils and sediments of different subsidence under changeable ecological environment,the vertical and spatial characteristics of pollutants can be compared and analyzed.The concentration of PCBs in different layers in the sediments of Yangzhuang subsidence is apparently higher that that in soil.The vertical change of PCBs content in soil is more stable.The concentration of PCBs in the southwestern point in the bed of the Mud River is relatively higher.The concentration of PCBs in the southwest of the soil is also relatively high.The concentration of PCBs in the soil of Xieqiao subsidence is higher than that in the sediment,but the vertical change of the PCBs content in sediment is more stable and the concentration of PCBs in the west of Xieqiao subsidence is higher.For PAHs,the concentration of PAHs in Yangzhuang subsidence is higher than that in soil except the PAHs in the layer of 5cm to 10cm and the vertical change of PAHs in soil is more stable.The concentration of PAHs in the soil of Xieqiao coal mine subsidence is slightly higher than that in sediment and the vertical change of PAHs in sediment is more stable.The concentration of the PAHs in the sediment of west session is higher than that in the sediment of east session.The concentration of PAHs decreases as the water area near the vital communication line stretches towards east and west.The compositional characteristics of pollutants is compared and analyzed by drawing the percentage graph of composition,three phase diagram and histogram of monomers’distribution of PCBs and PAHs in different layers of soil and sediment in different subsidences under changeable ecological environment.At the same time,the possible pollution sources are initially determined with ratio method.The soil and sediments in Yangzhuang coal mining subsidence mainly consist of trichlorodiphenyl,tetrachlorobiphenyl and pentachlorodiphenyl.Sediments and soils turn out to have similar characteristics.The soil pollution in Xieqiao subsidence mainly consist of low PCBs which comes from long-distance migration.Trichlorodiphenyl,tetrachlorobiphenyl,pentachlorodiphenyl and hexachlorobiphenyl were all detected in the sediments.They are mixed,turning out to be composite pollution.For PAHs materials,the soil and sediment in Yangzhuang subsidence mainly consist of medium and low-ring materials.The main contributing materials of triaromatic hydrocarbon are Phe and F1,petroleum source.The main materials of four-ring aromatic hydrocarbon are Chr,Flu and Pyr,coming from the combustion of coal.PAHs turn out to be the source of composite pollution.The PAHs in the soil and sediment of Xieqiao mainly consist of triaromatic hydrocarbon,followed by four-ring aromatic hydrocarbon,also turning out to be composite pollution source.Though making the fitting curve of physicochemical indexes and correlation analysis of PCBs and PAHs in different layers in the soil and sediment of different subsidences under changeable ecological environment,following results can be found by comparing:there is a strong correlation between organic matter and PCBs and PAHs.The PCBs and PAHs in sediments and the fitting coefficient are higher than those in soil.The fitting coefficient firstly vertically goes up from the surface and then decreases progressively;there is a strong correlation between organic matter and such low-chloride biphenyl as trichlorodiphenyl and tetrachlorobiphenyl;Organic matter has significant correlation with most homologs of PAHs on the level of 0.01.For particle size,the fitting coefficient of PAHs and PCBs in different levels of soil and sediment is generally low,illustrating that medium and particle size distribution in different layers has no influence on the distribution of PAHs and PCBs.In conclusion,this research makes a comparison of the column-shaped layers of POPs in the soil and sediments of mining subsidence under changeable ecological environment,which is significant for the fiurther understanding of the transfer characteristics of POPs in media as well as the ecological health of subsidence area.