呼和浩特市绿地土壤重金属污染特征及评价

Characteristic and Evaluation of Soil Pollution by Heavy Metal in Different Greenbelts of Hohhot

选择呼和浩特市城区公园绿地、居民小区绿地和道路绿化带为研究对象,采集城市中心和东南西北5个区域共45个样品。通过对不同绿地类型和不同区域土壤6种重金属含量的分析,采用单项污染指数法和内梅罗综合污染指数法对重金属的污染程度进行评价,采用主成分分析法分析重金属污染的来源,以期为呼和浩特市绿地土壤环境保护及其重金属污染防治提供科学依据。结果表明:呼和浩特市城区不同绿地类型土壤中4种重金属的平均含量均超过内蒙古的土壤背景值,重金属Cu和Cr含量分别达到背景值的2.20倍和1.68倍;单项污染指数评价结果显示,不同绿地类型土壤中重金属存在不同污染程度,重金属Cu在道路绿化带和居民小区绿地呈中度污染,在公园绿地呈轻度污染。不同土壤重金属元素污染程度依次为Cu>Cr>Zn>Pb>Ni>As。内梅罗综合污染指数法评价结果表明,道路绿化带呈中度污染,其次是居民小区绿地,污染水平为轻度污染,公园绿地污染程度最轻;城西呈中度污染,其余均为轻度污染。不同绿地类型和不同区域土壤重金属综合污染指数大小为道路绿化带(2.09)>居民小区绿地(1.83)>公园绿地(1.54);城西(2.04)>城南(1.78)>城东(1.77)>城中(1.76)>城北(1.73)。主成分分析结果显示,呼和浩特市绿地土壤不同重金属的来源存在差异,其中Cu、Cr和Ni主要来自交通污染源和人们日常生活废弃物的堆放;As主要来源于自然源。

The city parks,residential areas,and urban roads in Hohhot were selected as the research objects.Forty-five soil samples were collected by triple subsampling technique in the three functional zones.To investigate and analyze the heavy metal pollution in soil in different green spaces and different zones of Hohhot,the pollution of heavy metal was assessed with single factor pollution index and Nemerow integrated pollution index,and the pollution sources were discriminated by principal component analysis.The aim of this study was to provide a scientific basis for soil environmental protection and heavy metal pollution prevention in green space of Hohhot.Contents of six kinds of heavy metals were analyzed in different green spaces of Hohhot.The mean contents of heavy metals in soil samples exceeded the corresponding background values in the Inner Mongolia Autonomous Region.The mean contents of Cu and Cr were 2.20 times and 1.68 times,respectively,as high as the soil background values of the Inner Mongolia Autonomous Region.Single factor pollution index showed that the urban soil in Hohhot has been polluted by heavy metals.The Cu pollution was moderate in road greenbelts and residential areas,and mild in park greenbelts.The pollution degree was Cu>Cr>Zn>Pb>Ni>As.Nemerow integrated pollution index showed that soils from the road greenbelts were moderately polluted by heavy metals.The soils from residential areas were mildly polluted.And the soils from city parks were slightly polluted.The soils were moderately polluted by heavy metals in the west of Hohhot.The rest of the soils were mildly polluted.The Nemerow integrated pollution index of the different areas ranked as follows,road greenbelts(2.09)>residential areas(1.83)>city parks(1.54);west(2.04)>south(1.78)>east(1.77)>centre(1.76)>north(1.73).The results of principal component analysis showed that the heavy metals in soil of Hohhot came from different sources.Cu,Cr and Ni were mainly originated from anthropogenic sources while As was mainly controlled by natural sources.