Distribution characteristics, source analysis and ecological risk assessment of PAHs in tea garden soil in China

In this study, we collected 177 soil samples from major tea-producing areas in China, systematically investigated the spatial distribution characteristics of the polycyclic aromatic hydrocarbons (PAHs) in the soil of these tea plantations and discussed the environmental factors influencing of the PAHs in tea garden soil. The feature ratio method and source analysis methods were used to determine the PAHs source in tea garden soil, and the potential risk of PAHs in tea garden soil was also evaluated. The results showed that the concentrations of the 16 PAHs in 177 samples ranged from 6.21 to 4068.91 ng g-1, with an average of 257.00 ng g-1. The majority of PHAs in tea garden soils predominantly contained a 5-6 ring pattern, and the highest content was indeno (1,2,3cd) pyrene (InP, 23%) and benzo (b) fluoranthrene (BbF, 16%). In addition, 10.16% of the PAHs in tea plantation soils contained a 2-3-ring pattern, with naphthalene (NAP) having the highest content. PAH source in Chinese tea garden soil was predominantly mixed combustion, such as incomplete biomass combustion, petroleum combustion, coal combustion and wood combustion. The PAHs distribution was mainly affected by the industrial structure, geographical location of tea plantation, climatic conditions, soil properties and other factors in different regions. According to the Dutch Maliszewska-Kordybach grading standard, 79% of the soil samples from Chinese tea plantations were classified as unpolluted, 13% as mildly polluted, and 2% and 6% as moderately and severely polluted, respectively. Although the PAH pollution in tea plantations was generally low, BaP and InP pose significant ecological risk in some areas. Therefore, strategies such as effective guidelines and environmentally friendly technologies, must be developed to reduce the risk of PAH pollution in tea plantation soils.