Contamination and source differentiation of Pb in park soils along an urbanerural gradient in Shanghai

Abstract

Urban soil Pb contamination is a great human health risk. Lead distribution and source in topsoils from 14 parks in Shanghai, China were investigated along an urban-rural gradient. Topsoils were contaminated averagely with 65 mg Pb kg-1, 2.5 times higher than local soil background concentrations. HCl extracts contained more anthropogenic Pb signatures than total sample digests as revealed by the higher 207/206Pb and 208/206Pb ratios in extracts (0.8613 and 2.1085 versus total digests 0.8575 and 2.0959). This suggests a higher sensitivity of HCl-extraction than total digestion in identifying anthropogenic Pb sources. Coal combustion emission was identified as the major anthropogenic Pb source (averagely 47%) while leaded gasoline emission contributed 12% overall. Urbanization effects were observed by total Pb content and anthropogenic Pb contribution. This study suggests that to reduce Pb contamination, Shanghai might have to change its energy composition to clean energy