峰峰煤矿塌陷区典型农田土壤剖面重金素元素化学风化规律

Chemical Weathering Law of Heavy Metal Element in Typical Farmland Soil Profile in Subsidence Area of Fengfeng Coal Mine

采集峰峰煤矿塌陷区典型农田剖面土壤,通过测定分析不同埋深土壤重金属元素(As、Cu、Ni、Pb、Cr、Cd、Zn和Hg)分布特征,利用质量平衡理论进行化学风化规律研究,探究塌陷驱动下剖面土壤重金属元素化学风化过程。结果表明:峰峰煤矿塌陷区典型农田剖面土壤重金属元素Pb、Cd和As的含量超过国家农用地土壤污染风险管控标准,最大超标倍数分别为3.86、59.77、3.82;元素Cu、Ni、Zn、Cr和Hg未超标。重金属元素Cd和As可能在塌陷驱动下,受地表径流和雨水淋滤下渗影响,使得其含量自表层向下逐渐增加。表层土壤元素Cu、Pb、Cr、Hg迁入富集,元素Ni、As、Zn和Cd迁出淋滤;犁底层元素Cu、Ni、Zn和Pb迁出淋滤,Hg迁入富集,其余元素规律变化不明显。累积元素存在潜在风险,需要监控;淋滤元素存在直接风险,需要高度管控。实验结论为全面评估煤矿开采对土壤化学性能的影响,防治流域水土流失和保护区域生态环境提供科学依据。

The soil of a typical farmland section in the collapse area of Fengfeng Coal Mine was studied to explore the process of chemical weathering of heavy metal elements in the section soil driven by the collapse.The mass balance theory was used to study the chemical weathering laws by measuring and analyzing the distribution characteristics of heavy metal elements(As,Cu,Ni,Pb,Cr,Cd,Zn and Hg)in different buried depths of soil.The results show that the content of heavy metal elements Pb,Cd and As in soil of the typical farmland section in the subsidence area of Fengfeng Coal Mine exceeds the national agricultural land soil pollution risk management and control standards,and the maximum exceeding multiples are 3.86 times,59.77 times,and 3.82 times respectively.The elements Cu,Ni,Zn,Cr and Hg does not exceed the standard.Heavy metal elements Cd and As might be driven by subsidence and influenced by surface runoff and rainwater leaching,so that their contents gradually increase from the surface downward.The surface soil elements Cu,Pb,Cr and Hg migrated in and enriched,while the elements Ni,As,Zn and Pb migrated out and leached.The elements Cu,Ni,Zn and Pb in the bottom layer of plough migrated out and leached,while Hg enriched,and the migration of other elements was not obvious.Accumulated elements have potential risks and need to be monitored.At the same time,leaching elements have direct risks and need to be highly controlled.This experiment provides a scientific basis for the comprehensive evaluation of the effects of coal mining on soil chemical properties,the prevention and control of water and soil erosion in river basins and the protection of regional ecological environment.