Abstract: Using the  ²¹⁰Pb and ¹³⁷Cs dating technique combined with test results of polycyclic aromatic hydrocarbons (PAHs) in sediment cores on floodplain of Songhua River, we analyzed time trend of PAHs mass ratio in the past 90 years. Results show that the mass ratio of PAHs in sediment increases sharply from the 1960s to a peak in the early 1990s and subsequently decrease. The time trend of sedimentary PAHs in Songhua River is basically similar to that in Dianchi and some other urban lakes in China, but clearly different from that in developed countries. The results also show that the PAHs concentrations reach a relatively moderate level in the surface sediments compared with other domestic river sediments. The pollution characteristics of low ring compounds such as naphthalene, phenanthrene and so on are presented. According to the relative abundance of PAHs ring number and ratios of w(Ant)/w(Ant+Phe), w(Flt)/w(Flt+Pyr), the PAHs of sediment mainly comes from petroleum pollution. The stage change of mass ratio of PAHs is significantly correlated with the population and GDP in the watershed during the last 90 years, i.e. PAHs pollution of Songhua River is related to human activities.

Key words: sediment core, polycyclic aromatic hydrocarbons (PAHs), floodplain, Songhua River