The Supergene Environmental Characteristics Of Heavy Metals In Coal Mine Area Located At Qingshui River Basin And Potential Soil Remediation Method

As coal mining threatened the water and soil quality and ecological environment of surrounding water sources area,the study and prevention of heavy metal pollution in coal mine area have become a major environmental problem to be solved urgently.We comprehensively explored the pollution characteristics of heavy metals in various environmental media of coal mine area located at Qingshui River basin from the perspectives of source,particle size,and chemical fraction,and synthesized remediation materials aiming at heavy metals in contaminated soil.The main conclusions were as follows:Coal gangue in Qingshui River basin was low-sulfur,second-highest-iron,low-chlorine and high-ash.In natural environment,minerals containing Fe,Ca and Mn weathered or leached,while minerals containing Si and Ti were stable.Under simulated rainfall conditions,the mobility efficiencies of heavy metals from fresh coal gangue were much higher than that of weathered coal gangue,which was closely related to their mobility fractions.Among them,the mobility efficiencies of Zn and Cd were the highest.The leaching law of heavy metals from coal gangue was fluctuating and affected by intermittent reoxygenation process and surface minerals.Soils with high content heavy metals were around coal mine and roadsides of transportation.As,Cd,Cu and Pb in soil were mainly from coal mining,and contents of them in some sites exceeded environmental quality standards.Heavy metals leached from coal gangue were enriched in soil fine fractions with low TOC content,and coal dust containing heavy metals were enriched in soil fine fractions with high TOC content,while soil coarse fractions derived from soil parent material were almost unaffected.The profiles of heavy metals in different regions were closely related to the surrounding environment and heavy metals chemical fractions.The Mn mobility fraction in surface soil was relatively high,and leaching reduced Mn content change in profile.The non-carcinogenic and carcinogenic health risks generated by heavy metals in soil and groundwater were at the acceptable level.The water chemistry type of Qingshui River was affected by Pearl Lake in the upper reaches of Yongding River,and it changed after converging into Yongding River.After heavy metals from coal mining,Mn from bearing plants and Hg from scenic spot development entered the water body,the distribution of heavy metal contents was overlying water<pore water<sediment.Cr and Pb presented the highest logarithmic distribution coefficients in sediment and pore water,because they mainly exist in residue fraction.Coarse coal particles containing heavy metals were mainly concentrated in sediment coarse fractions,and heavy metals generated from acid mine drainage were mainly concentrated in fine fractions.Toxicity assessment showed that heavy metals in sediments and pore water of Pearl Lake belong to moderate level.For low-concentration As,Cd,Cu and Pb contaminated soil in coal mine area,new remediation material CPM was synthesized,and it could effectively reduce the total amount of heavy metals in soil and increase residue fractions percentages.As and Pb were mainly combined with MnFe2O4 of CPM.Part of As(?)was firstly oxidized to As(?)and then coordinated.Pb underwent ion exchange and electrostatic attraction.Cd and Cu mainly coordinated with chitosan of CPM.This study showed that heavy metal pollution in coal mine area was light,and heavy metal distribution of chemical fraction and particle fractions in soil and sediment was different.The CPM could effectively remove heavy metals in co-contaminated soil.This research provided a theoretical basis and potential technical support for water source protection and soil remediation in coal mine area.