Non-targeted tandem-mass spectrometry enables the tracking of anthropogenic pollutants from coastal seawater to sea spray aerosol

Daniel Petras1, Matthew Pendergraft2, Pedro Belda-Ferre3, Clare Morris4, Brock Mitts5, Jeremiah Minich6, Allegra T Aron7, Rob Knight8, Lihini Aluwihare9, Pieter Dorrestein10 and Kimberly A Prather9, (1)University of California San Diego, Scripps Institution of Oceanography, La Jolla, United States, (2)University of California San Diego, Chemistry and Biochemistry, La Jolla, CA, United States, (3)University of California San Diego, Department of Pediatrics, La Jolla, CA, United States, (4)University of California San Diego, Scripps Institution of Oceanography, La Jolla, CA, United States, (5)University of California, San Diego, Department of Chemistry and Biochemistry, La Jolla, CA, United States, (6)Scripps Institution of Oceanography, Marine Biology Research Division, La Jolla, CA, United States, (7)UNiversity of California San Diego, United States, (8)University of California San Diego, Departments of Pediatrics and Computer Science & Engineering, La Jolla, CA, United States, (9)Scripps Institution of Oceanography, La Jolla, United States, (10)University of California San Diego, Collaborative Mass Spectrometry Innovation Center, La Jolla, CA, United States
Abstract:
Anthropogenic pollutants inundate marine ecosystems as human population growth and urbanization rapidly increase along the coast. For the analysis of organic pollutants in seawater, several mass spectrometry methods are available, that typically target a restricted number of compounds or intent to characterize organic matter composition as a whole by high-resolution mass spectrometry. Such experiments provide non-targeted compound detection by exact mass and annotation as molecular formulas. However, identification of particular compounds on a structural level remain hidden. Transfer of organic pollutants from coastal waters via sea spray aerosols and potential exposure of coastal communities, on the other hand, are still understudied. To investigate coastal water pollution and potential aerosolization in the Tijuana River estuary in San Diego (USA), we took river, seawater and aerosol samples during a three-month time series in Winter 2019, and analyzed them by liquid chromatography high-resolution tandem mass spectrometry, which provides non-targeted molecular annotation on a structural level. We integrated an advanced bioinformatic pipeline that allows scalable quantitative comparison between samples and expanded spectral annotation using molecular networking. With several thousand observed features, the seawater chemotype shifted significantly after rainfall due to increased river and wastewater discharge. We could attribute molecular drivers of these shifts to hundreds of anthropogenic compounds, such as pesticides, industrial chemicals, cleaning products, pharmaceutical and their putative breakdown products. Exploring potential chemical transfer via sea spray aerosolization, we detected dozens of anthropogenic compounds in aerosol samples, depending on wind speed, direction and river discharge as well as on their chemical properties. These results provide important insights into potential exposure of coastal communities through organic pollutants from sea spray aerosols. The analytical pipeline applied in our study furthermore outlines a scalable framework for future monitoring and source-tracking of marine ecosystems and aerosols, which we hope will contribute to a more deliberate assessment of how chemical pollution impacts coastal environments.
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