Polycyclic aromatic hydrocarbons in sediment–porewater system from the East China Sea: Occurrence, partitioning, and diffusion

The distribution, partitioning behavior, and diffusion of polycyclic aromatic hydrocarbons (PAHs) within sediment–porewater system were determined in two cores obtained from the Min-Zhe coastal mud of the East China Sea (ECS). Depth profiles of apparently dissolved PAH levels exhibited greater varia...

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Bibliographic Details
Published in:Environmental research 2022-06, Vol.209, p.112755-112755, Article 112755
Main Authors: Wu, Zilan, Lin, Tian, Hu, Limin, Guo, Tianfeng, Guo, Zhigang
Format: Article
Language:English
Subjects:
China
Diffusion
East China Sea
Environmental Monitoring
Geologic Sediments
PAHs
Partitioning behavior
Polycyclic Aromatic Hydrocarbons - toxicity
Sediment–porewater system
Soot
Water Pollutants, Chemical - analysis
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Summary:The distribution, partitioning behavior, and diffusion of polycyclic aromatic hydrocarbons (PAHs) within sediment–porewater system were determined in two cores obtained from the Min-Zhe coastal mud of the East China Sea (ECS). Depth profiles of apparently dissolved PAH levels exhibited greater variabilities, with their elevated levels at depth and a high abundance of two-to three-ring PAHs observed. These distribution and composition patterns were inconsistent with the corresponding sediment PAHs, indicating differences in controlling factors for PAHs present in the system. In addition to compound's hydrophobicity, low detection of heavier PAHs in porewater was possibly correlated with the sediment transport process, as indicated by a relatively high weathering ratio in southern Min-Zhe coastal mud. PAH sorption affinity to the collected core sediments exhibited a generally decreasing trend downcore, as expressed by sediment–porewater partition coefficients. This was consistent with the higher content of porewater PAHs in deep core sediment. The established sediment total organic carbon (TOC)–porewater partitioning profiles in cores were predicted with amorphous organic carbon (AOC)-, coal tar-, and TOC-based distribution models, suggesting a dominant nonlinear sorption of PAHs to AOC. Through activity determinations, PAH diffusion within porewater was elucidated, with significant upward and downward mass transfer for PAHs occurring in both cores. The upward diffusion in the core collected from northern Min-Zhe coastal mud was in significant association with sediment TOC. This suggests that sediment TOC (especially AOC)-desorption of lighter PAHs into porewater, and therefore the possibility of their participation in environmental cycling. Baseline toxicity potential and toxic unit calculations indicated a relatively low exposure risk for benthic organisms to porewater PAHs. •Profiles and dominating factors of PAH levels in sediment and porewater differed.•Sorption of PAHs to amorphous organic carbon prevailed overall sorptive process.•Porewater PAHs presented upward and downward diffusion based on activity profiles.•PAH diffusion tendency in porewater was correlated with core sediment sorption.
ISSN:0013-9351
1096-0953
DOI:10.1016/j.envres.2022.112755