渝西某煤矿区土壤重金属污染程度及其特征分析

【目的】研究渝西煤矿开采导致该区域土壤重金属污染的程度并进行特征分析，为当地煤矿区环境污染防控和生态修复提供科学依据。【方法】利用国家标准方法对渝西某废弃煤矿区土壤中碳氮磷和主要重金属含量进行测定，采用单因子污染指数法、内梅罗综合污染指数法及土壤污染负荷指数法评估该煤矿区土壤重金属的污染程度。【结果】渝西某煤矿区的土壤总氮、总磷和有机质含量分别在8.400~126.000 g/kg、1.508~6.033 g/kg和18.006~216.070g/kg，其中总氮和有机质含量在煤矿中心区域（运煤干线两侧、煤矿进口、矿山山坡和矸石场）含量较高，在煤矿周围区域（农田、居民区、公园和学校）含量较低，总磷含量则表现为煤矿中心区域低于煤矿周围区域。渝西煤矿的开采使该区域土壤重金属镉（Cd）、铬（Cr）、铜（Cu）、镍（Ni）、铅（Pb）和锌（Zn）]出现不同程度超标，各样地Cd和Cu含量均已超过重庆土壤背景值和国家土壤背景值，其中Cd的最小值已达农用地土壤污染风险筛选值的6.37倍。运煤干线两侧土壤中的Cr和Cu以及矸石场土壤中的Pb含量最高。污染程度评价结果显示，该煤矿区土壤Cd污染达严重污染水平，其单因子污染指数范围在25.811~60.023；内梅罗综合污染指数和土壤污染负荷指数均显示该煤矿区土壤为重度污染。【结论】渝西某煤矿区土壤已受到煤矿开采引起的多种重金属复合污染，其中Cd和Cu是威胁当地土壤生态环境健康的主要重金属元素。相比内梅罗综合污染指数法，土壤污染负荷指数法能更好地反映该煤矿区的污染特征。

Pollution degree and characteristics of heavy metals in soil of a coal mine area in western Chongqing

【Objective】 To study the degree of soil heavy metal pollution caused by coal mining in western Chongqing, and analyze its characteristics so as to provide scientific basis for environmental pollution prevention and control and ecological restoration in the local coal mining area.【Method】 The content of carbon, nitrogen, phosphorus and major heavy metals in the soil of an abandoned coal mine area in western Chongqing was determined by national standard method. The single factor pollution index method, Nemero comprehensive index method and soil pollution load index method were used to evaluate the pollution degree of heavy metals in the soil of the coal mine area.【Result】 The contents of total nitrogen, total phosphorus and organic matter in the soil in the coal mine area in western Chongqing ranged from 8.400 to 126.000 g/kg, 1.508 to 6.033 g/kg and 18.006 to 216.070 g/kg, respectively. The contents of total nitrogen and organic matter were higher in the central area of the coal mine(both sides of main coal transport lines, coal mine entrance, hillside of mine, and waste dump) and lower in the area around the coal mine(farmland, residential areas, parks, and schools), and the contents of total phosphorus were lower in the central area of the coal mine than in the area around the coal mine. The mining of coal mine in western Chongqing has resulted in the excessive of heavy metalscadmium(Cd), chromium(Cr), copper(Cu), nickel(Ni), lead(Pb), zinc(Zn) ]in the soil in this region to varying degrees. The content of Cd and Cu in various places has exceeded the Chongqing soil background value and the national soil background value, among which the minimum value of Cd has reached 6.37 times of the screening value of soil pollution risk in agricultural land. The content of Cr and Cu in soil on both sides of coal trunk line and Pb in soil of waste dump were the highest. The evaluation of pollution degree showed that soil Cd pollution in Yuxi coal mine area reached the serious pollution level, and the single factor pollution index ranged from 25.811 to 60.023. Both Nemerow composite pollution index and soil pollution load index showed heavy pollution in the coal mine.【Conclusion】 The soil in a coal mine area in western Chongqing has been polluted by multiple heavy metals caused by coal mining, among which Cd and Cu are the main heavy metal elements that threaten the health of local soil ecological environment.Compared with Nemerow index method, soil pollution load index method can better reflect the pollution characteristics of coal mine area in this study.