The occurrence characteristics and risk assessment of polycyclic aromatic hydrocarbons (PAHs) in tea garden soils from the Southeast of Hubei Province: a comparative study with surrounding agricultural and wasteland areas.

内容摘要

To reveal the pollution characteristics, sources, and ecological risks of polycyclic aromatic hydrocarbons (PAHs) in soils under different land use patterns in Yangxin County, southeastern Hubei Province, surface soil samples (0-20 cm) were collected from tea garden, camphor forest, rapeseed field, wasteland, and peach grove, and 16 priority PAHs were analyzed. The Σ16PAH concentration ranged from 8.29 to 194.39 ng/g, with a mean of 94.58 ng/g, indicating a relatively low contamination level compared with previously reported national soil PAH levels. Relatively high PAH concentrations were observed in the tea garden soils and in the single wasteland area-integrated composite sample, whereas generally lower concentrations occurred in camphor forest, rapeseed field, and peach grove soils. High molecular weight PAHs (5-6 ring) accounted for 53.7%, dominating the composition and suggesting high-temperature combustion sources. Exploratory source analysis (diagnostic ratios and principal component analysis) provided exploratory evidence that PAHs mainly originated from mixed combustion sources (coal, biomass burning, and vehicle exhaust), with a minor petroleum contribution. The mean toxic equivalent (TEQ) was 12.161 ng/g, with DahA and BaP accounting for approximately 70% of the total BaP-equivalent concentration (TEQBaP) Ecological risk assessment based on ERL/ERM benchmarks showed that all PAH concentrations were below ERM values. However, concentrations of phenanthrene (Phe), indeno[1,2,3-cd]pyrene (IcdP), benzo[b]fluoranthene (BbF), and benzo[ghi]perylene (BghiP) in some tea garden samples and in the wasteland composite sample fell between the ERL and ERM, indicating potential ecological risks. Cumulative ILCR differed among land-use types, and female values were consistently slightly higher than male values. Although the mean cumulative ILCR values for all land-use types were below the screening level of 1 × 10-6, the upper range in the tea garden exceeded this threshold, indicating that some sampling points may pose relatively higher carcinogenic risks. This study provides baseline information for PAH pollution control and ecological risk management in tea garden soils.