平原河网地区农田土壤重金属污染特征及来源解析

Pollution characteristic and source apportionment of heavy metals in farmland soil from a plain river network region

为实现对平原河网地区农田土壤重金属的精准管控,保障农产品的质量安全,本研究以典型平原河网地区——嘉兴市为例,通过采集表层(0~20 cm)土壤样品(n=40),分析土壤中重金属的含量水平与分布特征,利用地累积指数法和潜在生态风险指数法,评价重金属的污染风险,并结合相关性分析、绝对主成分得分-多元线性回归(APCS-MLR)和正定矩阵因子分解模型(PMF),定量解析重金属的污染来源。结果显示:土壤中铜(Cu)、镍(Ni)、铬(Cr)、锌(Zn)、铅(Pb)、镉(Cd)、砷(As)和汞(Hg)的含量分别为(28.8±3.73)、(36.5±5.98)、(60.7±5.38)、(70.5±8.04)、(33.2±6.25)、(0.08±0.04)、(7.30±1.52)mg·kg^(-1)和(0.31±0.15)mg·kg^(-1)。其中,部分点位Hg含量超过农用地土壤风险筛选值(超标率为12.5%)。研究区域主要污染元素为Hg,其地累积指数(Igeo)为(0.20±0.77),呈轻微至轻度污染(67.5%);综合潜在生态风险(RI)为(122±39.8),属于中度风险,Hg是主要风险因子(64.4%)。源解析结果表明,农田土壤重金属的来源为工业源(32.0%)、自然源(28.2%)、农业源(25.8%)和交通源(14.0%),其中Hg主要来源于农业源(62.9%)和工业源(37.1%)。未来可加强对农业投入品及工业三废的管控,降低农田土壤中Hg的输入,保障农田土壤的安全利用及农产品的质量安全。

The purpose of this study is to achieve accurate control of heavy metals in farmland soil from the plain river network area,so as to ensure the quality and safety of agricultural products.In this study,we selected Jiaxing City,a typical plain river network area,as a study area.The concentration and distribution of heavy metals in soil were examined by collecting surface soil samples(0–20 cm,n=40);then,two methods[the geo-accumulation index(Igeo)and the potential ecological risk index]were used to evaluate the risks posed by heavy metals.Moreover,absolute principal component score-multiple linear regression and positive matrix factorization were combined to quantitatively analyze the sources of heavy metals.The content of copper(Cu),nickel(Ni),chromium(Cr),zinc(Zn),lead(Pb),cadmium(Cd),arsenic(As),and mercury(Hg)in soil were(28.8±3.73),(36.5±5.98),(60.7±5.38),(70.5±8.04),(33.2±6.25),(0.08±0.04),(7.30±1.52)mg·kg^(-1),and(0.31±0.15)mg·kg^(-1),respectively.Among these,the Hg content exceeded the screening value of soil pollution risk for agricultural land(the over-standard rate was 12.5%).The dominant element was Hg[Igeo=(0.20±0.77)],showing slight to mild pollution(67.5%).Moreover,the comprehensive potential ecological risk[RI=(122±39.8)]was found to be moderate,and Hg was established to be the main risk factor(64.4%).The sources of heavy metals in farmland soil were industrial sources with a contribution of 32.0%,followed by natural(28.2%),agricultural(25.8%),and transportation(14.0%)sources.Among these,Hg was mainly derived from agricultural(62.9%)and industrial(37.1%)sources.In the future,the control of agricultural inputs and industrial waste can be strengthened to reduce the input of Hg into farmland soil,ensuring the safe utilization of farmland soil and the quality and safety of agricultural products.