Levels of polychlorinated dibenzo-p-dioxins and dibenzofurans in mountainous and park soils in Beijing, China

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were analysed in 95 mountainous and park soil samples collected from 19 sites in Beijing, China. The levels of PCDD/Fs in the mountainous soils were low (0.086-0.59; mean 0.29; median 0.23 ng I-TEQ/kg). The levels in the park soils far from the city centre were a little higher (0.39-0.88, mean0.68; median 0.75 ng I-TEQ/kg). However, in the park soils near to the city centre, there were an abrupt jump in their concentration (1.7-3.2; mean 2.3, median 1.7 ng I-TEQ/kg), about ten times higher than those in the mountainous sites. Comparison of PCDD/Fs homologues and congener compositions between possible sources and samples indicated that the mountainous and park soils in Beijing had been slightly contaminated mainly by sodium pentachlorophenate, sewage sludge, atmospheric deposition and vehicle exhaust. These results have also been supported by the principal component analysis.