不同农业利用方式对土壤重金属累积的影响及原因分析

Effects of Land Use on Heavy Metal Accumulation in Soils and Source Analysis

【目的】探讨不同农业利用方式下土壤中重金属的累积及其影响要素,制定有效降低土壤中重金属含量的技术和策略。【方法】系统采集了吉林省四平市部分区域内设施菜地、露天菜地、大田玉米地及林地4种土地利用类型的148个样品,分析了其Cr、Ni、Cu、As、Cd、Pb、Zn等重金属的含量,并进行了相应的调查。【结果】在研究区域内,不同利用方式对土壤中Cr、Ni、Cu、As、Cd、Zn的含量有较大的影响,平均含量顺序均为:设施菜地>露天菜地>大田>林地,但对Pb含量的影响不显著。4种土地利用方式中,以设施菜地中Cr、Ni、Cu、As、Cd、Zn的累积最多,其次是露天菜地、大田玉米地,林地未出现累积。研究的7种重金属元素中以Cd的累积较严重,其次是Cu。其中设施菜地的Cd含量平均达0.467mg·kg-1,超过了《土壤环境质量标准》(GB15618-1995)中II级标准(0.3mg·kg-1,6.5<pH<7.5),也相当于自然状态下林地Cd含量平均值的5.2倍;但4种利用类型中其它重金属含量的平均值均低于国家II级标准。分析认为,与土地利用年限相比,农用化学品、特别是肥料的质量和数量是导致不同利用方式下土壤重金属含量差异的重要原因。【结论】土地利用方式对Cr、Ni、Cu、As、Cd、Zn的累积具有显著影响,其中以设施菜地累积较显著,避免重金属含量较高化肥、有机肥和农药的施用是防止土壤重金属累积、促进土壤健康和可持续利用的重要保障。

【Objective】 Heavy metals accumulation and their influential factors were studied in different land use soils,which will provide a theoretical basis for controlling the content of heavy metals in soils. 【Method】 To identify the effects of land use on the accumulation of heavy metals in soils,148 samples were collected from four land use types including greenhouse,open vegetable field,maize field and forest land in Siping area,Jilin Province,and Cr,Ni,Cu,As,Cd,Pb,and Zn contents of those samples were determined with ICP-Mass. 【Result】 The result showed that there was a rather large difference in effects of the accumulation of Cr,Ni,Cu,As,Cd,Zn in soils under different land use types,except Pb. Based on the assessment compared with background concentrations in soil,the higher accumulation of heavy metals was found in greenhouse and open vegetable field,lesser in maize field and forest field. The order of mean contents of heavy metals in soils was greenhouse〉open vegetable field〉maize field〉 forest field. Cd ,Cu had relatively serious accumulation in soils compared with Cr,Ni As and Zn. The mean content of Cd in greenhouse was 0.467 mg·kg^-1,which exceeded the Grade II of Chinese Soil Quality Criterion GB15618-1995 （6.5〈pH〈7.5） for Cd standard of 0.3 mg·kg^-1,and was 5.2 times of Cd in forest field. The mean contents of Cr,Ni,Cu,As,Pb,Zn in soils under four land use types were lower than gradeⅡ of Chinese Soil Quality Criterion. Compared with the age of land use,agricultural chemical compounds application （especial the quality and quantity of applied fertilizer） was the important reason for leading to difference in accumulation of heavy metals in soils under the studied land use types. 【Conclusion】 Heavy metals （Cr,Ni,Cu,As,Cd,Zn） accumulation in soils was significantly affected by land use types,soil in greenhouse accumulates more heavy metals than others. It is suggested that the application of high contents of heavy metals in chemical fertilizer,organic fertilizer and pesticides should be avoided to prevent the accumulation of heavy metal and keep high quality soils for sustainable use.