Polycyclic aromatic hydrocarbons (PAHs) in agricultural soils from Ningde, China: levels, sources, and human health risk assessment.

Soil-bound polycyclic aromatic hydrocarbons (PAHs) in farmland are critical to human health. The level, composition, source, and cancer risk of sixteen PAHs in agricultural soil from Ningde, China, were investigated. The results indicated that the total concentrations of 16 PAHs ranged from 77.3 to 1188 ng g-1, with a mean value of 406 ng g-1. Five-ring PAHs were found to have the highest concentrations (148 ± 133 ng g-1), followed by four-ring (120 ± 101 ng g-1), three-ring (61.9 ± 54.2 ng g-1), six-ring (44.6 ± 61.0 ng g-1), and two-ring (31.3 ± 31.0 ng g-1). Employing positive matrix factorization (PMF), four PAH sources including biomass burning (36.3%), coal combustion (35.5%), traffic emissions (16.4%), and coke source (11.8%) were identified. Incremental lifetime cancer risk (ILCR) results showed that ILCR values ranged from 7.1 × 10-4 to 1.1 × 10-3, which will cause moderate-to-high cancer risk to human health mainly via the soil ingestion and dermal contact exposure pathways. The source-oriented results indicated that coal combustion (32.7%), traffic emission (34.3%), and biomass burning (32.4%) had similar contributions to the total cancer risk. Therefore, more attention should be paid to these pyrolysis-originated sources to protect humanity from the health risk of PAHs.