How important is abiotic dissipation in natural attenuation of polycyclic aromatic hydrocarbons in soil?

Natural attenuation capacity, as one of the most important ecosystem functions in soil, plays a vital role in the detoxification of organic pollutants such as polycyclic aromatic hydrocarbons (PAHs). However, despite the role of biodegradation is established, the contribution of abiotic dissipation to natural attenuation has long been overlooked. Herein, the abiotic dissipations of 16 types of PAHs in a past coking site and of anthracene (ANT) in various cultivated soils were studied. Results showed that the contributions of abiotic dissipation to the total attenuation were in a wide range from 11.8 to 99.7% depending on the types of PAHs. Specifically, abiotic dissipation is higher for heavy PAHs (68.3-99.7%) than for light PAHs (11.8-71.5%), with the exception of ANT (80.7%). Similarly, the contribution of abiotic dissipation to ANT attenuation ranged from 30.7 to 68.6% in eight soils. The abiotic dissipation rate of ANT followed the order of lateritic-red earth > gray-desery soil > coastal solonchaks > cumulated-irrigated soil > cinnamon soil > fluvo-aquic soil > purplish soil ~ yellow-brown earth, which was positively correlated with transition metal contents in soils. These findings demonstrated that the abiotic dissipation of PAHs is determined by both molecule properties and soil types. Overall, this work provided valuable insights into clarifying the roles of abiotic dissipation in PAH attenuation in soil.