[Characteristic and evaluation of soil pollution by heavy metal in different functional zones of Hohhot].

The residential areas, cultural and educational areas, city parks, commercial areas, urban roads, industrial zones, and development zones in Hohhot were selected as the research objects. Sixty-two soil samples were collected by triple subsampling technique in the seven functional zones. The aim of this study is to control the soil heavy metal pollution of Hohhot and provide the basic information. To investigate and analyze the heavy metal pollution in soil in different functional 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. Contents of seven kinds of heavy metals were analyzed in different functional zones 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 Zn were 2. 33 and 1. 85 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 the most severe in commercial areas, and the pollution degree was in the following order: Cu > Zn > Cr > Mn > As > Ni > Pb. Nemerow integrated pollution index showed that soils from the commercial areas were seriously contaminated by heavy metals. The soil of urban roads was moderately polluted. The soils from cultural and educational areas and the city parks were slightly polluted. The Nemerow integrated pollution index of the seven areas ranked as follows: commercial areas (3.03) > urban roads (2.12) > residential areas (1.98) > cultural and educational areas (1.81) > industrial zones (1.72) > development zones (1.36) > city parks (1. 28). The results of Principal Component Analysis showed that the heavy metals in soil of Hohhot came from different sources. Cr, Cu, Mn, Pb and Zn were mainly originated from anthropogenic sources while Ni and As were mainly controlled by natural sources. The healthy development of urban ecosystem has been threatened by soil heavy metal pollution in Hohhot.