Sedimentary record of polycyclic aromatic hydrocarbons in Songhua River, China

Concentrations of polycyclic aromatic hydrocarbons (PAHs) were determined in surface sediments and one dated sediment core from the Songhua River, Northeast China. The total concentration of 15 PAHs (16 priority pollutants designed by the United States Environmental Protection Agency minus naphthalene) in the surface sediments ranged from 16 to 421 ng/g dry weight. An evaluation of PAH sources based on diagnostic ratios suggested that PAHs in the most surface sediments were mainly derived from biomass and coal combustion, with the exception of those from Jilin City, where both petroleum contamination and combustion were possible sources of PAHs. A historical record of PAH contamination was reconstructed using a Pb-210 and Cs-137 dated sediment core from a backwater zone of the river. The characteristic changes in concentrations, fluxes and patterns of 15 PAHs over the past 75 years were captured in detail. Two increases in PAH fluxes were observed during the period from the early 1930s to the mid 1960s, and from the mid 1970s and the mid 1990s. The increases were attributed to the several wars (1937-1953) and reconstruction of new China (1949-1965) and the implementation of the Reform and Open Policy since 1978. Two declines in PAH fluxes were also observed from the mid 1960s to the mid 1970s and from the mid 1990s to the present. The decreases were attributed to the Great Cultural Revolution (1966-1976) and the implementation of some pollution reduction measures since the 1990s. This study is the first attempt to provide information on the sedimentary record of PAHs in the Songhua River.