Coupled Physical-Biogeochemical Dynamics of Polycyclic Aromatic Compounds in the East China Sea

Polycyclic aromatic compounds (PACs), including harmful
polycyclic
aromatic hydrocarbons (PAHs) and more toxic derivatives, are continuously
released contaminants. Their provenance and dynamics in coastal oceans
remain poorly understood. This study presents the first comprehensive
assessment of PACs in coastal oceans by combining their presence with
key hydrological and biogeochemical indicators, and potential microbial
degradation. High concentrations of Σ92PACs (48–660
ng/L) were observed in the East China Sea, influenced vertically by
upwelling and related sediment resuspension during winter. Spatial
heterogeneity reveals distinct distribution patterns: PAHs and alkyl-PAHs
were mainly influenced by riverine inputs, horizontal transport via
coastal currents, and fronts acting as barriers, in contrast, oxygen-PAHs
and nitro-PAHs were primarily shaped by secondary transformations
within warm water masses rich in nutrients. The relationship between
dissolved PACs and chlorophyll a underscores the
dominance of biodegradation over the marginal biological pump effect
during wintertime low primary productivity. Metagenomic analysis further
highlights microbial degradation as a crucial PAC removal pathway,
with enhanced microbial diversity driven by terrigenous advection
and upwelling. The methodologies and findings of this research provide
valuable insights into PAC cycling in coastal oceans.