| Distribution of Copper (Cu), Zinc (Zn), Nickel (Ni), Lead (Pb), Chromium (Cr), Cadmium (Cd), Arsenic (As), and Mercury (Hg) in soils from the typical regions of Shantou such as electrical wastes recycling sites were studied, and pollution risk of heavy metals on the environment was evaluated. Among the 118 surface soil samples, 42 (corresponding to 35.6%) were above the national standards when evaluated with single factor index method. Specifically, Ni, Cu, Hg, and As exceeded the standards by 26.3%, 18.6%, 7.6%, and 0.85%, respectively. Among the 20 samples from five section soil sites, 7 (corresponding to 35.0%) were above the national standards with Ni, Hg, and Cu exceeding respectively by 20.0%, 15.0%, and 10.0%. The composite pollution index of all samples ranged from 0.32 to 6.08, with an average of 1.26. Overall, 39.1% of soils were polluted, and which composed of heavily (7.2%), moderately (10.9%), and lightly (21.0%) contaminated soils. The highest composite pollution index (1.98) was found in Chaoyang district, followed with descending order by Jinping, Chenghai, Chaonan, Longhu, Haojiang districts, and Nanao town. Pollution, industrial and agricultural wastes, and contaminated irrigation water were the main sources of heavy metal contamination in soils. Except for Cr and As, concentrations of Cu, Pb, and Hg in soils from Shantou districts were much higher than the corresponding soil background concentrations recorded for Guangdong province, China, and the whole world. Controlling heavy metal output from industrial and agricultural sources and reducing the concentrations of soil heavy metals through integrated treatment techniques are the effective methods to improve the soil quality in Shantou. |
