[Pollution of polycyclic aromatic hydrocarbons (PAHS) in middle and lower reaches of the Yellow River].

Samples of water, suspended particulate matter (SPM) and sediment in the Yellow River was analyzed. The total concentration of PAHs in the main river varies from 179 ng/L to 369 ng/L (sigma 15PAHs) in water, from 54 microg/kg to 155 microg/kg (sigma 13PAHs) in SPM dry weight, and from 31 microg/kg to 133 microg/kg (sigma 13PAHs) dry weight in sediment. The levels of PAHs in water of tributaries are higher than those in the corresponding sites in the main river, and concentrations of benzo(a)pyrene in most of the stations sampled are above drinking water standard. In SPM, PAHs of 3 to 6 benzene rings are mainly correlated to the content of total organic carbon (TOC) in different sites of the main river, while only 4 to 6 rings PAHs in sediment of main river are correlated to TOC for the influence of Mengzhou Canal, whose concentration of 3-ring PAHs are quite high. The distribution of PAHs in all media sampled in the main river indicates that PAHs are mainly transported from water into SPM between Mengzhou and Jiaogong Bridge, while in the reach between Jiaogong bridge and Huayuankou a great reduce of PAHs in SPM is mainly due to the diluting effect in the interchanging process between sediment and SPM. Source analysis also reveals that PAHs are mainly originating from coal burning, although in some tributaries PAH inputs could come from combustion of petroleum.