| China is an important energy country in the world,and its mineral resources are extremely rich.It accounts for a large proportion of the gross national product.However.the uncontrolled mining of mineral resources has largely disturbed the surrounding ecological environment and even caused great damagement.Especially in the Huainan mining area,the long-term mining activities lead to large-scale surface subsidence,the problem of heavy metal pollution in coal mining subsidence areas has received more and more attention.Therefore,the Huainan Panji mining subsidence area was selected to be the key research area,collects representative coal,coal gangue.soil,water body,sediment samples,and tests its heavy metal content and chemical forms.Using lead isotope to analyze the source of heavy metals,systematically and comprehensively reveal the degree of heavy metal pollution,spatial distribution,migration and transformation,pollution sources in the environment of coal mining subsidence area.Finally,the heavy metal content of biological samples(wheat,hair)in the study area was tested to explore the accumulation characteristics of heavy metals in the organism In order to provide a solid theoretical basis for the scientific prevention and control of heavy metal pollution in the subsidence area of coal mining.The results show:(1)The raw coal samples collected in the subsidence area were medium-high volatiles,ultra-low total moisture,low-medium ash,and low-sulfur coal.Coal gangue was mainly composed of clay minerals,mainly kaolinite and quartz.The soil pH was 6.56±0.32,the organic matter content was 38.55±13.89 g·kg~-1,the TN content was 4.00±1.64 g·kg~-1,and the TP content was 0.43±0.10 g·gs~-1.The temperature of the subsidence water was 15.3±1.62?.the EC was-77±19.78 mV,the pH was 8.41±0.29,and the concentrations of TP and TN in the subsided water were 0.21±0.09 mg·L~-1 and 1.51±0.63 mg·L~-1,respectively.The sediment pH was 8.06±0.33,the organic matter content was 46.99±9.55g·kg~-1,the total nitrogen content was 5.84±0.61g·kg~-1,and the total phosphorus content was 0.55±0.15g·kg~-1.(2)The study of heavy metal content showed that compared with the background values of Huainan coal,except for Cu,Zn and Pb,the Cd content in the subsidence area was 2.83 times of the background value,and the As content was 23.67 times of the background value.The Cd content in the coal gangue was 5.12 times of the background.And the As content is 1.33 times the background value.Compared with the background values of Huainan soil,the content of Cu,Zn,Pb and As in the subsidence area did not exceed its background values,and the Cd content was 4.14 times of the background value of Huainan soil.The contents of five heavy metals in the subsided water body were in line with the Class I water quality standard in China GB3838-2002,and the water was affected by human activities.Compared with the soil background values of Huainan,the Cu content in the sediment was 1.37 times of the background value,the Zn content was 1.08 times of the background value,the Pb content was 1.27 times of the background value,and the Cd content was 19.5 times of the background value.The As content was 21.49 times of the background value.The heavy metal content in the subsidence area had the basic laws of sediment>soil>coal and coal gangue.(3)The Tessier morphology extraction experiment showed that among the samples of coal,coal gangue,soil and sediment in subsidence area,the residual state of five heavy metal elements was the highest,followed by iron-manganese oxide bound state,organic matter bound state and carbonate combination.State,exchangeable state had the lowest proportion,but the proportion of potential bioavailable states was higher.(4)The study of bioaccumulation characteristics showed that the heavy metal content in different parts of wheat in subsidence area had the rule of Zn>Cu>Pb>Cd>As.Wheat had strong migration and transformation ability to heavy metals Zn and Cu.The harmful heavy metals Pb,Cd and As were accumulated in roots.The results of health ecological risk assessment indicated that there was a potential health risk of heavy metals in wheat in subsidence areas.The content of heavy metals Cu,Zn,Pb,Cd and As in the hair samples of the residents in the subsidence area were higher than that of the female hair samples.Compared with the hair samples of the residents in the heavy metal pollution areas in China,the heavy metal in the hair samples of the subsidence area were very low,and there were no obvious accumulative phenomenon.(5)The study of heavy metal sources in sediments showed that the heavy metals in sediments were mainly from the three main sources of automobile exhaust emissions,soil and coal gangue,the relative contribution rates of 30.90%,51.70%and 17.40%,respectively. |
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