Polycyclic aromatic hydrocarbons (PAHs) in soils from a shale gas exploitation area in China: Quantitative sources...

The environmental implications and risks of polycyclic aromatic hydrocarbons (PAHs) emitted from shale gas exploitation to surrounding soils are not clear. In this study, concentrations of 16 priority-PAHs in soils of different land-use types from the Fuling shale gas exploitation area in Chongqing, the first commercial shale gas exploitation area in China established in 2013, were analysed by a gas chromatograph coupled with mass spectrometer (GC-MS). For the first time, the sources and risks of PAHs were systematically characterised by an integrated approach, combining multiple fractal inverse distance weighting and concentration-area model, the absolute principal component multiple linear regression model and Monte Carlo simulation. The average concentrations of 16 priority-PAHs in shale gas field soils (184 ng·g^-1) were higher than in background forest/grasslands (73.4 ng·g^-1) and in blowout land soils (56.4 ng·g^-1). Environmental geochemical maps showed that PAH hotspots were formed around towns and shale gas field sites, emphasising the dominant role of anthropogenic activities over soil physicochemical properties in PAH accumulation. Coal combustion/vehicle emissions and petrogenic sources are the major sources in the study area, contributing 41 % and 59 % of the total PAHs, respectively. Notably, the source-oriented risk assessment demonstrated that the ecological and health risks associated with petrogenic PAHs obviously exceeded those from coal combustion/vehicle emissions. The improved hybrid model can effectively quantify both PAH emission levels from shale gas exploitation activities and potential risks from distinct sources. This study highlights the impact of shale gas exploitation and provides a robust theoretical foundation for developing targeted strategies to mitigate PAH pollution risks in shale gas exploitation areas.