Sedimentary record of polycyclic aromatic hydrocarbons in mud deposits along the southeastern coast of Liaodong Peninsula and its relation to the anthropogenic and natural activities in the Northeast China

The concentrations of polycyclic aromatic hydrocarbons (PAHs) in two ²¹⁰Pb-dated sediment cores collected from mud deposits along the southeastern coast of the Liaodong Peninsula were investigated to reconstruct the sedimentary records of PAHs and their relationship with anthropogenic and natural activities. The concentrations of 16 PAHs (∑PAHs) were low and remained stable before the year 1820, reflecting an autarkic agricultural civilization. From 1820 to 1900, with the gradual lifting of prohibition, people migrated into Northeast China, resulting in the release of large amounts of ∑PAHs into the environment. At the beginning of the 1900s, the ∑PAH levels in the two cores displayed increasing trends with significant fluctuations, linked to a period of social turbulence with continuous wars in Northeast China. After 1949, vertical ∑PAH trends in the cores predominantly reflected trends in economic development. Based on the different PAH composition trends (2–3-ring and 4–6-ring PAHs), we consider that historical energy usage in Northeast China can be divided into three stages: biomass fuel use dominated before 1920, biomass and fossil fuels co-existed from 1920 to 1980, and fossil fuels dominated after 1980. In addition, this study also demonstrates that the PAH concentrations (2–3-ring PAHs) in these two sediment cores can be used, to a certain extent, to identify anthropogenic fire events.