我国耕地土壤重金属输入输出平衡变化分析

Analysis of the changes in the input and output balance of heavy metals in Chinese agricultural soils

为研究我国耕地土壤重金属输入输出平衡现状,本研究根据2015—2020年公开发表的文献和统计数据,建立了我国耕地土壤重金属的输入输出清单,并与2006—2015年的清单进行对比分析。研究结果表明,与2006—2015年相比,2015—2020年大气沉降对我国耕地土壤8种重金属(Cd、Hg、As、Pb、Cr、Cu、Zn、Ni)的输入量降低了15.8%~65.4%,灌溉水对Hg的输入量增加了86.8%,化肥对Zn的输入量增加了5.9%,畜禽粪便对Cu、Zn、Ni的输入量分别增加了19.4%、64.7%、6.6%,市政污泥对As和Cr的输入量分别增加了22.8%和3.5%。我国耕地土壤Cd、Hg、As、Pb、Cr和Ni的净输入量分别下降了28.0%、54.1%、43.7%、47.8%、60.7%和48.4%,对大气污染物排放和废水排放的严格管控、对化肥生产工艺和污泥净化工艺的优化、农作物产量的增加是造成重金属净输入量降低的主要原因;Cu和Zn的净输入量分别略微增加了2.4%和7.2%,主要原因是《饲料卫生标准》和《肥料中有毒有害物质的限量要求》缺少对Cu、Zn含量的限制。总体来看,我国当前耕地土壤重金属的输入量大于输出量,重金属呈累积状态,但累积量呈下降趋势。

To study the current status and analyze the changes in the input and output balance of heavy metals in Chinese agricultural soils,this study established an input and output inventory of heavy metals in Chinese agricultural soils based on published literatures and statistical data from 2015 to 2020 and compared it with that from 2006 to 2015.The results showed that,compared with 2006 to 2015,the input of atmospheric deposition to eight heavy metals(Cd,Hg,As,Pb,Cr,Cu,Zn,and Ni)in Chinese agricultural soils decreased by 15.8%-65.4%in 2015 to 2020,input of irrigation water to Hg increased by 19.4%,64.7%,and 6.6%,input of fertilizers to Zn increased by 5.9%,input of livestock manures to Cu,Zn,and Ni increased by 6.6%-64.7%,and input of sewage sludge to As and Cr increased by 22.8%and 3.5%,respectively.The net inputs of Cd,Hg,As,Pb,Cr,and Ni to Chinese agricultural soils decreased by 28.0%,54.1%,43.7%,47.8%,60.7%,and 48.4%,respectively.The main reasons for the decrease in heavy metal input were strict control of air pollutant emissions and wastewater discharges,optimization of fertilizer production processes and sludge purification processes,and the increase in crop yields.The net input of Cu and Zn increased by 2.4%and 7.2%,respectively,mainly due to the lack of restrictions on the content of Cu and Zn in the Feed Health Standards and the Requirements for the Limits of Toxic and Hazardous Substances in Fertilizers.The input of heavy metals to Chinese agricultural soils is generally greater than the output,and despite the accumulation of heavy metals,the accumulation is decreasing.