[Vertical Pollution Characteristics and Source Analysis of Soil PAHs in Different Land Use Types]

In order to study the vertical pollution characteristics of polycyclic aromatic hydrocarbons (PAHs) in soils of different land use types in suburban areas of Nanjing, 15 types of controlled PAHs were studied in each section (0-100 cm) of soils from six different land use types, including a vegetable field, forestland, residential area, urban land, paddy field, and industrial area. The vertical distribution and composition characteristics, influencing factors, and sources of PAHs were analyzed. The results showed that:the total concentrations of Σ₁₅PAHs in the six sampling site profiles were as follows:vegetable field (69.3-299.2 μg·kg^-1), forestland (20.8-128.3 μg·kg^-1), residential area (30.7-142.1 μg·kg^-1), urban land (185.6-1728.7 μg·kg^-1), paddy field (208.3-693.0 μg·kg^-1), and industrial area (165.6-739.2 μg·kg^-1). There was no pollution in the residential area or forestland and a light pollution level in the vegetable field, medium pollution level in the paddy field and industrial area, and more serious pollution in the urban land. Soil PAHs were mainly distributed in the surface or subsurface layer, except in the residential area and urban land; however, they were still detected in the deep layers, and high-molecular-weight PAHs were dominant in most depths and sampling sites. The vertical distribution and migration of PAHs in soils were affected by molecular characteristics and component concentrations of PAHs, soil physical and chemical properties, and land use types. PMF source analysis indicated that coke sources, traffic sources, and coal combustion sources from human activities were the main sources of PAHs in this study region.