Objective Sea sediment is one of the major environment fates of poly aromatic hydrocarbons (PAHs). The research of PAHs in sea area adjacent to land-based discharge outlets is rare. This study aims to investigate the PAHs pollution level and major resource in sediments adjacent to land-based sewage outlets to the sea of Fujian province.

Methods Concentrations of PAHs were determined for 27 sediment samples collected from sea area adjacent to 6 land-based sewage outlets of Fujian Province from 2018 to 2020 by Gas Chromatography-Mass Spectrometry method.

Results The spatial distribution and sources of PAHs were studied and the ecological risk of PAHs was assessed. The results revealed that the concentration of PAHs were in the range of 70.5~508.9 ng/g with mean of 195.9 ng/g, which was low compared to the concentration of other coastal sediments. The PAHs concentrations were determined by the location of the sewage outlets instead of the type of the outlets. PAHs from sewage outlet discharge may be the important input resource of Fujian coastal sediments. The proportions of different rings of PAHs were comparable in the sewage outlet, thermal power station effluent, and oil refinery discharge; however, these proportions differed significantly in the textile printing and dyeing effluent, electroplating outlet, and bleaching and dyeing discharge. By analysis of the relative abundance of rings and isomer ratio of PAHs, it was found that the sources of PAHs in sediments adjacent to land-based sewage outlets were different, mainly related to the discharged sewage; and the major source was combustion source. The ecological risk assessment revealed that PAHs in the coastal sediment environment posed minimal ecological risk, exerting few adverse effects on living organisms.

Conclusion In summary, concentrations of PAHs in sediments of adjacent to land-based sewage outlets to the sea of Fujian province were low and varied among different sea areas. The major source of PAHs was combustion source. PAHs in coastal sediment environment had few negative ecological effects to the living organisms with minimum ecological risk.