Polycyclic aromatic hydrocarbons in urban soils of different land uses in Beijing, China: Distribution, sources and their correlation with the city's urbanization history

Abstract

A total of 127 surface soil samples (0–20 cm) were collected from Beijing's urban district and determined for 16 polycyclic aromatic hydrocarbons (PAHs). The mean concentration of ∑PAHs was 1802.6 ng g −1 with a standard deviation of 1824.2 ng g −1. Average ∑PAHs concentration and the percentage of high-molecular weight PAHs (4–6-rings) decreased from inner city to exterior areas. This correlated with the urbanization history of Beijing's urban district and inferred an increasing trend of soil PAHs with accumulation time and age of the urban area. ∑PAHs in different land uses decreased in an order as: culture and education area (CEA) > classical garden (CG), business area (BA) > residential area (RA), roadside area (RSA) > public green space (PGS). PAHs in CEA mainly came from coal combustion, while soils of RSA exhibited clear traffic emission characteristics. PAHs in other land uses came from mixed sources. Principle component analysis followed by multivariate linear regression indicated that coal combustion and vehicle emission contributed about 46.0% and 54.0% to PAHs in Beijing's urban soils, respectively. Risk assessment based on the Canadian soil criterion indicated a low contamination level of PAHs. However, higher contents in some sensitive land uses such as CEA and CG should draw enough attention.