基于UNMIX模型和莫兰指数的湖南省汝城县土壤重金属源解析

Source Apportionment of Soil Heavy Metals in Rucheng County of Hunan Province Based on UNMIX Model Combined with Moran Index

工业化正在加剧我国的土壤重金属污染.湖南省汝城县矿产资源丰富,工矿企业密集,粗放的矿业生产给当地土壤环境带来了一系列问题,准确掌握其污染来源是土壤污染防治的关键和前提.采集汝城县233个土壤样本,对重金属含量进行模型分析后选择拟合效果较好的Cd、Hg、As、Pb、Cr、Cu、Ni七种重金属为研究对象,测定其含量,使用UNMIX模型解析其污染来源,并结合空间插值与莫兰指数方法,从空间关系的角度验证模型并补充说明研究区土壤重金属的来源.结果表明:①研究区土壤中Cd、Hg、As、Pb、Cr、Cu、Ni含量的平均值分别为0.29、0.18、19.91、44.17、66.31、28.67、25.16 mg kg,除Cr、Ni外,Cd、Hg、As、Pb、Cu含量的平均值均高于当地背景值.除Hg外的其他6种重金属存在含量超出GB 15618—2018《土壤环境质量农用地土壤污染风险管控标准(试行)》筛选值的情况.②研究区土壤中7种重金属的含量主要受到自然源、大气沉降与工业直接排放混合源、污水源和工业直接排放源的影响,贡献率分别为41.87%、33.10%、13.27%和11.76%.其中,自然源对Cr和Ni的贡献率较大,大气沉降与工业直接排放主要影响Cd和Pb,污水源和工业直接排放源分别对Hg和As的贡献最大.③UNMIX模型与空间分析方法的结合,一方面验证了受体模型的解析结果,同时也对土壤重金属的来源起到了补充说明的作用.研究显示,汝城县土壤重金属含量与工业活动关系密切,工业排放除直接对附近土壤造成污染外,通过大气沉降、河流输送对远距离土壤环境的影响也尤为突出.

Industrialization is aggravating soil heavy metal pollution in China.Rucheng County of Hunan Province is rich in mineral resources and the industrial and mining enterprises are dense.The developed mining production has brought a series of problems to the local soil environment.Accurate understanding of the pollution sources is the key and premise for soil pollution control.In order to find out the sources of heavy metals in the soil in this area,233 soil samples were collected in the study area.Seven heavy metals Cd,Hg,As,Pb,Cr,Cu and Ni with good model fitting effect were selected as the research objects and their contents were measured.The UNMIX model was used to analyze the pollution sources,combined with the spatial interpolation and Moran index method.The model was validated from the perspective of spatial relationship and the sources of heavy metals in the soil were supplemented.The results showed that:(1)The average content of Cd,Hg,As,Pb,Cr,Cu,and Ni in the soil of the study area was 0.29,0.18,19.91,44.17,66.31,28.67,25.16 mg kg,respectively.Except for Cr and Ni,the average values of Cd,Hg,As,Pb,and Cu content were all higher than the local background values.The contents of other 6 heavy metals except Hg exceeded the screening value of Soil Environmental Quality,Agricultural Land Soil Pollution Risk Control Standard(Trial)(GB 15618-2018).(2)The contents of the 7 heavy metals in the soils were mainly affected by natural sources,mixed sources of atmospheric deposition and industrial direct discharge,sewage sources and direct industrial sources,and their contribution rates were 41.87%,33.10%,13.27%and 11.76%,respectively.Among them,natural sources had a greater contribution rate to Cr and Ni,atmospheric deposition mainly affected Cd and Pb,and sewage and industrial sources had the largest contributions to Hg and As,respectively.(3)The combination of the UNMIX model and the spatial analysis method not only verified the analytical results of the receptor model on the one hand,but also served as a supplementary explanation for the sources of heavy metals in the soil.The results show that the heavy metal content of soil in this region is closely related to industrial activities.In addition to the direct pollution of the nearby soil caused by industrial emissions,the influence of atmospheric deposition and river transportation on the remote soil environment is also particularly prominent.The research results can provide a reference for the source control of soil pollution prevention and control.