Current-use insecticides in the Bohai Sea

Current-use insecticides (CUIs) are increasingly detected in coastal environments, yet the extent to which phase partitioning controls their cross-media coupling and air-sea exchange remains poorly resolved. Here, we quantified 46 CUIs across atmospheric gas and particle phases and seawater dissolved and particulate phases in the Bohai Sea, together with depth-resolved observations in the water column. All target compounds were detected in the atmospheric gas phase, whereas fewer were occurred in atmospheric particles, and seawater burdens were dominated by the dissolved fraction. Total atmospheric concentrations ranged from 12,488 to 35,989 pg m⁻³ and were overwhelmingly gas-dominated (99.0 ± 0.2%), whereas total seawater concentrations ranged from 21,102 to 76,898 pg L⁻¹ and were primarily dissolved (69.8 ± 12.5%). Across the water column, CUIs exhibited a recurrent V-shaped pattern, with concentrations decreasing from the surface to 10 m and increasing again near the bottom. Composition-based analyses further showed that cross-media coupling was strongly phase-structured: atmospheric gas and dissolved seawater were more compositionally aligned than particle-associated phases. Fugacity ratios indicated that most CUIs underwent net atmospheric deposition, whereas a small subset remained near equilibrium or displayed site-specific bidirectional exchange. Collectively, these results show that phase partitioning, rather than bulk concentration alone, constrains the transport, exchange, and redistribution of CUIs across the coastal air-sea continuum.