四川北部林地土壤地球化学特征分析

Analysis on forest soil geochemical features of north Sichuan

【目的】对四川北部林地土壤地球化学特征进行宏观分析及重金属污染评估,为该地区林地土壤的物质组成研究及土地资源保护与合理利用提供科学依据。【方法】通过实地样品采集与数据分析,对四川北部平武、北川地区林地土壤元素含量特征进行分析,并运用单项污染指数(Pi)法和内梅罗综合污染指数(Pn)法进行土壤重金属污染评价。【结果】平武林区浅、深层土壤中As、Cd、Hg、Pb、Zn元素含量均高于全国平均值,北川林区则是Cd、Hg、Mn、Pb、Zn元素含量高于全国平均值。平武林区土壤重金属元素中As与Hg、Cd与Zn呈极显著正相关(P<0.01,下同),北川林区则是As与Cd、Hg,Cd与Hg、Pb、Zn,Pb与Hg、Zn呈极显著正相关。平武林区土壤重金属Pi排序为Cd>Zn>As>Hg>Pb,其中,Pb元素处于清洁状态,As、Hg、Zn元素属轻度污染,Cd元素属重度污染;北川林区土壤重金属Pi排序为Cd>Zn>Pb>As>Hg,其中,As、Hg元素处于清洁状态,Cd、Pb、Zn元素属轻度污染。平武和北川林区土壤的Pn分别为5.502和1.494,北川属轻度污染,平武属重度污染。【结论】四川北部地区林地土壤中Cd、Hg、Pb、Zn等重金属元素含量均高于全国平均水平,部分林地已达重度污染,且以Cd元素的污染贡献最大。

【Objective】The forest soil geochemical features and heavy metal pollution were studied, in order to provide scientific basis for research of forest soil composition, and protection and rational utilization of land resources in north Sichuan. 【Method】Based on on-site sample collection and data analysis, the soil element content features of Pingwu and Beichuan forests in north Sichuan were studied, and heavy metal pollution of soil was assessed by calculating single factor index（Pi） and Nemerow multi-factor index（Pn）. 【Result】The contents of As, Cd, Hg, Pb and Zn in shallow and deep soils of Pingwu forest were higher than national average, and the contents of Cd, Hg, Mn, Pb and Zn in shallow and deep soils of Beichuan forest were higher than national average. In addition, In Pingwu forest soil, As was significantly correlated with Hg, Zn was significantly correlated with Cd（P0.01, the same below）. In Beichuan forest soil, As was significantly correlated with Cd and Hg, Cd was significantly correlated with Hg, Pb and Zn, and Pb was significantly correlated with Hg and Zn. The order of soil heavy metals in Pingwu forest based on their Pivalues was CdZnAsHgPb. Pb was at clean level, As, Hg and Zn were at light pollution level, and Cd was at severe pollution level. The order of soil heavy metals in Pingwu forest based on their Pivalues was CdZnPbAsHg, and As and Hg were at clean level, Cd, Pb and Zn were at light pollution level. The Pnof Pingwu and Beichuan forest soils were 5.502 and 1.494, respectively, thus Beichuan forest was at light pollution level, and Pingwu forest was at severe pollution level. 【Conclusion 】The contents of heavy metal elements including Cd, Hg, Pb, Zn, etc., in forest soil of north Sichuan are higher than national average, some of which were at severe pollution level, Cd makes the largest contribution to pollution.