Some people who reside in the southern portion of San Diego County, California, say it stinks to live there. Literally. For years, residents have complained that odors emanating from the polluted Tijuana River, which flows from Mexico into the U.S. toward the Pacific Ocean, are causing eye, nose and throat irritation, respiratory problems, fatigue, and headaches.
A new study shows that turbulence in polluted waters of the Tijuana River transfers contaminants to the air. In this photo, culverts at the Saturn Boulevard river crossing generate high turbulence, enhancing the transfer of toxic wastewater pollutants. The location was identified by members of the local community as a source of particularly strong odors. | Credit: Beatriz Klimeck / UC San Diego
Now, a new study from scientists at UC, San Diego Scripps Institution of Oceanography; UC, Riverside; San Diego State University; the National Science Foundation; and National Center for Atmospheric Research (NCAR) says the residents are not imagining things. The research found that the contaminated river is contaminating the air—releasing large quantities of the toxic gas hydrogen sulfide—commonly known as “sewer gas” because of its rotten egg smell.
In September 2024, the team had set up air quality monitors in San Diego’s Nestor community in the South Bay. One location was where water tumbles from a culvert, which as it falls, creates enough turbulence to send aerosolized particles of pollutants from the river into the air.
The scientists measured peak concentrations of hydrogen sulfide that were some 4,500 times what is typical for an urban area. In addition, they identified hundreds of other gases released into the air by the river and its ocean outflow, showing for the first time, a direct link between poor water quality and bad air quality—a connection lead investigator Kimberly Prather says had not been made before.
Untreated sewage and industrial waste have plagued the Tijuana River for decades, causing long-term closures of beaches. In July, the U.S. and Mexico signed a memorandum of understanding that requires both nations to expedite stormwater and sewage infrastructure projects on each side of the border.
Last week, EPA announced the completion of a ten-million-gallon-per-day expansion of the South Bay International Wastewater Treatment Plant in San Diego, which could help mitigate the issue, but as inewsource reports, it’s unclear as to when it will be operating at its new capacity.
The paper was published in the journal Science.
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