Kelley C. Barsanti

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.

1. Introduction Click to copy section linkSection link copied! The Tijuana River (TR) flows through a binational watershed, with about 75% of its drainage area located in Mexico and the remaining 25% within the United States (Figure 1B). (1) The rapid industrial growth of the Mexican city of Tijuana, (2) combined with poor wastewater management, has significantly affected the TR, leading to a continuous influx of urban runoff, industrial effluents, and untreated sewage into the river.

Editor’s summary Intense industrial and urban wastewater pollution has plagued the Tijuana River for decades, causing long-term closure of neighboring beaches. Rico et al. showed that surging wastewater flows in the summer of 2024 enhanced water-to-air hydrogen sulfide (H2S) transfer at a turbulent hotspot, leading to nighttime atmospheric H2S peaks thousands of times greater than typical urban levels.