Concentrations, sources and spatial distribution of polycyclic aromatic hydrocarbons in soils from Beijing, Tianjin and surrounding areas, North China

Abstract

The concentrations, profiles, sources and spatial distribution of polycyclic aromatic hydrocarbons (PAHs) were determined in 40 surface soil samples collected from Beijing, Tianjin and surrounding areas, North China in 2007, and all sampling sites were far from industrial areas, roadsides and other pollution sources, and across a range of soil types in remote, rural villages and urban areas. The total concentrations of 16 PAHs ranged from 31.6 to 1475.0 ng/g, with an arithmetic average of 336.4 ng/g. The highest PAH concentrations were measured in urban soils, followed by rural village soils and soils from remote locations. The remote-rural village-urban PAH concentration gradient was related to population density, gross domestic product (GDP), long-range atmospheric transport and different types of land use. In addition, the PAH concentration was well correlated with the total organic carbon (TOC) concentration of the soil. The PAH profile suggested that coal combustion and biomass burning were primary PAH sources.

Fig. 1

Map of sampling sites and ΣPAH₁₆ concentrations in soil. Three categories of sampling sites: urban (U), rural village (R) and background areas (B).

Fig. 2

The scatter plot between soil ΣPAH₁₆ concentration and TOC concentration. Both parameters are log-transformed.

Fig. 3

Cross plot of the Ant/(Ant + Phe) and Fla/(Fla + Pyr) ratio before and after using calibration factors.

Fig. 4

Scatter plots of soil ΣPAH₁₆ concentration in rural and urban soils against village or city population density (left) and GDP (right).

Fig. 5

The PAH profiles for background, rural and urban locations (2: 2-ring PAH; 3: 3-ring PAH; 4: 4-ring PAH; 5: 5-ring PAH; 6: 6-ring PAH).