Characterization and sources analysis of polycyclic aromatic hydrocarbons in surface sediments in the Yangtze River Estuary

Eighteen polycyclic aromatic hydrocarbons (PAHs), including 16 PAHs selected as priorities for control by the US Environmental Protection Agency, 1-methylnaphthalene and 2-methylnaphthalene, were determined in sediment samples from the Yangtze River Estuary, including the intertidal marshes and the river plume area. Results showed the PAH concentrations in marsh sediments (316–792 ng g⁻¹) were higher than those in the river plume sediment (98–391 ng g⁻¹). Further analysis suggested the PAH concentrations are correlated with total organic carbon (r = 0.71, p < 0.05), as well as water current and industrial activities. However, particle size less affects distribution of PAHs in Yangtze River Estuary. Results also showed a difference in PAHs’ compositions between marsh and river plume sediments: PAHs with two rings were more abundant than other PAHs’ compositions in river plume sediments, while PAHs with 3–4 rings were dominated in marsh sediments. This distribution pattern suggested different contamination sources between marsh and river plume sediments. The diagnostic ratios of PAH isomers and principal component analysis further demonstrated the PAHs in the marsh sediment came from burning biomass or coal, and those from river plume sediments derived from a mixture of petrogenic and pyrolytic source. The concentrations of total PAHs in the sediments from Yangtze River Estuary were relatively low in comparison with other estuaries around the world. And ecological risk assessment also suggested that the PAHs in the Yangtze River Estuary sediments present little ecotoxicological risk. However, a risk assessment for chronic exposure to low PAH concentrations should be performed in a further study.