不同利用方式农用地土壤重金属污染状况及其动态变化特征——以广东省徐闻县为例

A case study of heavy metals pollution and their seasonal changes in soils with different use types in Xuwen, Guangdong province

通过分析广东省徐闻县不同季节香蕉地、菜地、桉树林地和甘蔗地等4种不同利用方式农用地土壤As、Cu、Pb、Zn、Cd重金属含量,应用单项污染指数法和内梅罗综合指数法对土壤重金属污染状况进行评价,并得出其动态变化特征。结果表明,(1)根据重金属单项污染指数可知,所研究的5种重金属中,Cu污染最为严重,4种农用地土壤Cu污染程度大小顺序为菜地>桉树地>香蕉地>甘蔗地;其次是Cd污染,污染程度依次为菜地>香蕉地>甘蔗地>桉树地;菜地受到轻度Zn污染;其他元素含量均未超过国家标准。从重金属综合污染指数来看,菜地受到重金属中度污染,香蕉地、桉树地和甘蔗地均为轻度污染。(2)在不同季节,土壤重金属污染状况差异较大。Cu在4种农用地土壤中的污染指数年内呈递减规律;Cd在菜地和香蕉地中夏季污染指数最低而冬季最高。(3)土壤重金属相关性分析结果表明,Cu与Pb在4种土壤中的相关系数都较高,说明土壤中Cu与Pb同源,主要来自成土母质。菜地中,Zn与碱解N,Cd与有机质在0.05水平上存在显著负相关性,这说明土壤Zn和Cd污染不是来自有机肥,可能主要来自化肥和农药。

To investigate the heavy metals pollution in different types of agricultural soils as well as their seasonal changes in Xuwen, China, soil samples collected from vegetable fields （VF）, banana gardens （BG）, eucalypts forests （EF） and sugarcane fields （SF） in different seasons were determined for the concentrations of As, Cu, Pb, Zn and Cd with ICP-MS. By use of the single pollution indexmethod, it could be found that Cu pollution was the most serious among the five heavy metals examined and the extent to which the soils were polluted by Cu decreased as the following order： VF〉EF〉BG〉 〉SF. Cd pollution was also noticeable, and the content of Cd in all the soils decreased in the order ofVF〉 BG〉SF〉EF. Only vegetable fields were slighted polluted by Zn, and the pollution ofAs and Pb was not found in all the soils because of their contents below the national environmental standards. In addition, according to the Nemero comprehensive index methods, VF were moderately polluted by heavy metals and BG, EF and SF were slightlypolluted. Furthermore, correlation analysis of the heavy metals concentrations indicated that Cu and Pb in all different types of agricultural soils positively correlated, which suggested they entered into the soils from the same sources, namely, the parent materials. In VF, negative correlation exited between in either the pair of Zn and alkali-hydrolyzed N or the pair of Cd and organic matters with p〈 0.05, which, consequently, showed that the pollution of Zn and Cd did not result from organic fertilizers but the application of chemical fertilizers and pesticides.