Investigation of polycyclic aromatic hydrocarbons in the soils of Benevento Province, Italy

Benevento Province, located in the Campania region of Italy, may experience environmental quality impacts from neighboring developed areas such as Naples and Caserta. Previous studies have suggested that some agricultural chemicals from Naples, such as hexachlorobenzene, may be transported through the air to rural areas of Benevento. Additionally, high concentrations of polycyclic aromatic hydrocarbons (PAHs) have been detected in Naples and Caserta, making Benevento Province a potential PAH "sink." This study systematically investigated the occurrence of PAHs in soil from Benevento Province, southern Italy, and their correlations with environmental factors, soil-air exchange processes, and health risks. Over 95% of sampling sites exhibited ∑₁₆PAHs concentrations at non-polluted levels (9.50-1188 ng/g, mean = 55.0 ± 152 ng/g), and four-ring PAHs were the dominant pollutants contributing to 28.3% of ∑₁₆PAHs. The spatial distribution of PAHs presented significant heterogeneity, with hotspots concentrated near landfills. The results of Positive Matrix Factorization (PMF) model showed that the main sources of PAHs were vehicle emissions, coal/biomass combustion, and petroleum products volatilization/leakage, contributing 42.2%, 40.2%, and 17.6%, respectively. Most of PAHs correlated significantly with total organic carbon in the soil and population density, while only Benzo(b)fluoranthene (BbF) showed a significantly negative correlation with pH. The mass inventory of ∑₁₆PAHs ranged from 0.94 to 29.4 tons, averaging 2.45 tons. The synergistic effects of pollution hotspots and the persistent accumulation of PAHs in the soil suggested that the soil might act as a secondary source of PAHs. Toxicity equivalent and probabilistic risk assessments indicated that health risks from PAHs remained within acceptable limits.