Distribution characteristics and source apportionment of polycyclic aromatic hydrocarbons (PAHs) in soil across functional zones in mainland China.

Numerous studies have documented the severe hazards of soil polycyclic aromatic hydrocarbon (PAH) contamination, however, no research to date has systematically examined concentration variations and source differences across functional zones at a national scale. In this study, we analyzed the concentration, distribution characteristics and source apportionment of surface soil PAHs in mainland China through the collection of data from over 53,000 surface soil samples, 2234 sampling sites in 440 published articles. The results revealed that the concentrations of ∑PAHs ranged from 1.01 to 6,100,000 ng/g, with an average of 9995.95 ng/g, and nearly 70% of the surveyed areas in China faced significant PAHs pollution. The soil PAH concentrations in North China were significantly higher than those in South China, while eastern regions were higher compared to western areas. Temporal analysis revealed an inverted U-shaped distribution pattern in PAHs pollution levels for Central China, East China, and Northwest China. The PAH concentrations across functional zones ranked as follows: industrial zone (37,873.51 ng/g) > traffic zone (2639.62 ng/g) > commercial residential zone (1588.91 ng/g) > urban park (1178.16 ng/g) > agricultural zone (807.28 ng/g) > ecological function zone (635.64 ng/g). Source apportionment indicated that coal combustion (51.6%), traffic emissions (44%), petroleum sources (58.4%), coal combustion (38.1%), coal combustion (34.6%)/biomass burning (34%), and petroleum sources (33.7%) were the dominant contributors in industrial zone, urban park, traffic zone, agricultural zone, commercial residential zone, and ecological function zone, respectively. Clarifying the impacts of human activities on soil PAHs across functional zones are critical for mitigating global warming and supporting China's carbon neutrality goals.