Study Of Content And Migration Characteristics Of Heavy Metals In Soil From Linhuan Mining District

In recent years,with rapid development of the coal industry,the content of heavy metals(HMs)in soil increased continuously.Being of great non-degradability,this kind of pollution not only degrades the quality of the water bodies,atmosphere and food crops,but also threatens the health and well-being of people by the way of food chain.Therefore,most experts and scholars at home and abroad always pay more attention to it.To study the content characteristics and migration regularity of HMs in soil from coal mining area,the present paper takes Linhuan mining district of Huaibei coalfield as the research area.A total of 42 representative surface soil,24 deep soil,and 34 maize plant samples were collected,and the total contents and each fraction contents of seven HMs(Mn,Cd,Cr,Pb,Ni,Zn and Cu)were determined.Two methods were performed to assess the pollution statues and ecological risk of HMs in soil.Furthermore,multivariate statistical analysis and geostatistics were applied to examine the possible sources and spatial distributions of HMs in soil.The horizontal and vertical migration regularities of HMs in soil were studied,and the migration regularity of HMs in soil-mazie system was also researched.The main conclutions were listed as follows:(1)With the exclusion of Cd,the concentrations of the other HMs did not exceed the secondary standard values of National Environment Quality Standard for Soil,however,Cr showed relatively low content.According to the assessment results,Cd had a feature of high pollution degree and moderate ecological risk,and the others belonged to clean and low ecological risk.Furthermore,the values of the two synthetic pollution index methods revealed that the contamination of Renlou,Haizi and Tongting was relatively serious.Multivariate statistical analysis suggested that Cd,Mn,Ni and Cr were mainly originated from the combined pollution sources(e.g.,coal mining activities,agricultural,and natural factors),while the other HMs was affected by traffic sources.Through analysis of the spatial distribution,except for Cd,the contamination of HMs in northwest of the study area was higher than southeast,and the central part of outdated coal mines in the north areas were the most seriously polluted.(2)The selected HMs in the main soil types were dominated by the residual fraction.Furthermore,the order of mobility of HMs in soil was:Ni>Cd>Pb>Mn>Cu>Zn>Cr.The content of Mn,Cd,Pb and Zn were relatively high in soil around the gangue,in addition,the contents of HMs in surface soil gradually reduced with increasing distance between the gangue hill and the soil.The order of the migration level of HMs in soil profile was Ni>Cu,Zn>Cr,Cd,Mn>Pb.Mn and Ni have certain mobility in horizontal and vertical direction of soil,respectively.(3)Mn and Cu in leaves were less affected by dust fall,while the other HMs in stems and leaves were mainly originated from roots,absorbing from the soil.In addition,the bioconcentration of Cd and transfer factor of Mn was biggest,and the absorption of Mn and Cd in different parts of maize plants was not affected by chemical fractions in soil.