Soil survey was conducted in Shunde area with the method of 1:50 000 ecological geochemistry detailed survey to evaluate the source and the current status of heavy metal contamination in soils. A total of 495 samples of soil were collected from Shunde area. The statistical analysis shows that the levels of Cd, Cu, Pb, Zn, As and Hg are obviously higher than their soil average threshold values in Guangdong, implying heavy pollution. The mean values of heavy metals in soil samples exceed the corresponding background values in Guangdong Province. The mean values of Cd and As are 18 and 6.8 times, respectively, as high as the soil background values. According to different determinations, we divided the study area into four parts: river way, industrial soil (including furniture factory and electric appliance), fishpond land and residential area. The pollution index (Pi) of each metal and the Nemerow integrated pollution index (P综) were calculated in the different functional zones. The pollution degree is in order of Cd>As>Zn>Cu>Hg>Pb. The Nemerow integrated pollution indexes of the different areas are in order of river way > furniture factory > residential area > fishpond > electric appliance. Combined with the study of water and vegetables in Shunde area, the authors have revealed that the soil-water-plant system has been contaminated. Using the Pearson's correlation coefficient and the principal component analysis, the authors have found that there is a significant positive correlation between Cd, Cu, Pb and Zn, which constitute a typical combination of the lead-zinc mine and suggest a delta deposit controlled by natural factors. As comes not only from the river but also from the industrial activity; Hg is mainly derived from anthropogenic source. Combined with the natural mode of occurrence of soil and land-use type, the authors can judge the source of heavy metal in the study area. It is held that the serious contamination of heavy metals and the high adaptive disease in the study area originate from natural depositition and anthropogenic sources.
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