Persistence of organic compounds extended through ocean transport and air–sea exchange

Abstract Atmospheric volatile organic compounds (VOCs) are generally assumed to be spatially constrained by rapid atmospheric oxidation, limiting their influence to near-source regions. Here, analysis of air samples collected along a coastal transect during a large-scale anthropogenic perturbation demonstrates that ocean-mediated transport can act as a control on reactive compounds, extending their spatiotemporal distributions. VOCs derived from anomalous dry-season wastewater flows through the Tijuana River were detected in air ~ 35 km north of this riverine source. Mechanistic constraints and integrated analyses of atmospheric and hydrographic data revealed that ocean advection and air–sea exchange enabled the persistence of VOCs at the distal site. Coupled ocean–atmosphere processes extended VOC lifetimes longer than predicted based solely on atmospheric oxidative loss processes, broadening regional influence and shifting potential exposure patterns. These findings challenge the current understanding of pollutant fate in these coastal environments and the conventional view that offshore discharge of wastewater effectively mitigates coastal pollution.