Elevated Aerosol and VOC Concentrations in Imperial Beach, California, Associated with Sewage Discharges to the Tijuana River and Ocean
LEA EL KHOURY, Shihao Zhai, Katarina Konon, Daniel Sung, Chou-Hsien Lin, Evelyn Deveraux, Kimberly Prather, Pawel K. Misztal, Lea Hildebrandt Ruiz, University of Texas at Austin
Abstract Number: 415
Working Group: Urban Aerosols
Abstract
Imperial Beach, California, a coastal city near the U.S.-Mexico border, is frequently impacted by sewage discharges from the Tijuana River. Residents have reported respiratory and other health problems that appear to be associated with this pollution; yet, airborne emissions and air quality impacts are poorly characterized. Here we present our work from an ambient measurement campaign conducted in September 2024 in Imperial Beach (IB), California. Volatile organic compounds (VOCs) and non-refractory particulate matter (NR-PM) were measured using an electric mobile van equipped with a Vocus 2R Proton-Transfer-Reaction Time-of-Flight Mass Spectrometer (Vocus PTR-TOF-MS) and High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS). Stationary and mobile measurements were conducted during different times of the day. We observed episodic high aerosol concentrations with a maximum NR-PM1 (particulate matter with a diameter ≤1 µm) concentration of 100 µg m-3. During the highest concentration period, the organic aerosol composed 90% of NR-PM1, and the wind direction was from the south, downwind of the Tijuana River (TR). PM has several sources in this area, including sea spray aerosol, cross-border sewage pollution, vehicle and other urban emissions, and we use positive matrix factorization to separate these sources. Consistently, VOC magnitudes and compositions differed between various odorous plumes downwind of the TR and IB hotspots which are comprehensively analyzed in terms of aerosol precursors, odor activity, and toxicity. Overall, our results highlight that airborne pollutants originating from sewage discharge substantially impact air quality in Imperial Beach.