成都平原某农田区大气降尘重金属含量特征及生态风险评价

Characteristics and Ecological Risk Assessment of Heavy Metals in Atmospheric Dust in a Farmland Area in Chengdu Plain

大气沉降是农田土壤重金属污染的重要来源之一,为探究研究区大气重金属污染状况,在成都平原某农田区设置36个采样点收集大气降尘样品,测试降尘重金属含量,运用富集因子法、聚类分析等进行降尘重金属污染特征及来源解析,并对各重金属元素进行空间插值分析,生态风险评价。结果表明,研究区大气降尘重金属As、Cd、Cr、Cu、Hg、Ni、Pb、Zn含量均高于土壤背景值,分别为土壤元素背景值的6.87倍、6.64倍、28.46倍、1.3倍、3.35倍、1.14倍、5.97倍、7.42倍,低含量的Cd远远超过背景值;重金属元素变异程度大,空间分布不均匀。根据元素富集特征(EF)分析发现各重金属均受人为活动影响,程度不同,Cd元素富集呈显著污染,需重点关注,Hg、Pb、Zn次之,Cr、Ni基本无污染。生态风险评价结果显示,Cd元素生态风险极高对研究区农田区域生态系统的危害最为严重,其次为Hg元素,总体上降尘重金属呈强生态危害。大气降尘重金属元素Cd、Pb、As、Hg为一类,主要受交通活动、汽车尾气排放、煤炭燃烧影响影响,Cu、Zn为一类,主要受工业活动、垃圾焚烧影响,Cr、Ni为一类,来源于地表扬尘,且研究区降尘重金属最主要受为交通活动、汽车尾气排放。研究技术和方法可为成都平原农田土壤重金属污染大气源研究提供借鉴参考,成果弥补了当地大气重金属污染研究空白,可为当地农田土壤重金属污染大气源控制提供科学支撑。

Atmospheric deposition is one of the important sources of heavy metal pollution in farmland soil.In order to explore the contamination of heavy metals in the atmospheric dust,36 samples of atmospheric dust were collected and analyzed from a farmland in Chengdu,Sichuan province.The heavy metal content in dust of the samples were tested,and characteristics and sources of heavy metal pollution in dust were analyzed by enrichment factor method and cluster analysis.The spatial interpolation analysis and ecological risk assessment were carried out for each heavy metal element.The results showed that the contents of heavy metals As,Cd,Cr,Cu,Hg,Ni,Pb and Zn were all higher than the soil background value,which were 6.87 times,6.64 times,28.46 times,1.3 times,3.35 times,1.14 times,5.97 times and 7.42 times of the soil background value,respectively.The low content of Cd far exceeded the background value.The content of heavy metals had a large degree of variation and uneven spatial distribution.According to enrichment factor analysis,all heavy metals were mainly affected by human activity to different degrees.The enrichment of Cd showed high contamination and affected by human activities severely,which needs to be paid attention to,followed by Hg,Pb and Zn.Cr and Ni were basically pollution-free.The ecological risk assessment results showed that the extremely high ecological risk of Cd element has the most serious damage to the ecosystem of the study area,followed by Hg element.In general,heavy metal caused strong ecological harm.Cd,Pb,As and Hg fall into one category,and their contents mainly originated from traffic emission,vehicle emission and coal combustion.Cu and Zn fall into one category,the contents of which mainly originated from waste incineration and factory emission.Cr and Ni fall into one category,and their contents mainly come from soil dust.Moreover,the heavy metals in dust of the study area are mainly affected by traffic emission and vehicle emission.The research techniques and methods can provide reference for the research of heavy metal pollution in dust of farmland soil in the Chengdu Plain.The results make up for the research blank of local heavy metal pollution in the atmosphere,and can provide scientific support for the control of atmospheric sources of heavy metal pollution in local farmland soil.