Assessing Stormwater Impacts on Marine VOC Concentrations in a Coastal Urban Environment Using Remote Sensing and In Situ Data on the Tijuana River Estuary

Coastal-urban environments can be particularly vulnerable to unique air quality challenges due to their proximity to a variety of urban and marine emissions as well as characteristic atmospheric dynamics. The combination of these emissions and dynamics can lead to important impacts on inland air quality and climate. The Tijuana River Estuary, a major source of runoff and water pollution, exemplifies these challenges due to its location near the cities of San Diego and Tijuana. Frequent discharge events of stormwater and untreated wastewater into the coastal ocean pose health hazards, due to the risk of both direct contact with contaminated water, as well as indirect exposure via sea spray aerosol emissions. Additionally, the interaction between stormwater discharge and coastal waters can lead to the release of marine volatile organic compounds (VOCs), which are emitted into the atmosphere and can influence air quality and cloud formation through the formation of secondary organic aerosols (SOA). These VOCs, produced by both biological processes and chemical reactions in the ocean, can contribute to aerosol formation and photochemical reactions that impact atmospheric composition and climate. The mixing of polluted runoff with coastal waters may influence VOC emissions, further linking water quality to atmospheric outcomes. Turbidity, a commonly used indicator of water quality, is particularly effective for monitoring runoff events as it measures changes in suspended particles commonly associated with stormwater and wastewater plumes. Remote sensing turbidity data products thus offer a method for quantifying runoff influences on water quality and associated air quality outcomes. This study aims to investigate the connections between stormwater runoff events and marine VOC emissions in coastal environments by combining high-resolution satellite imagery with in situ measurements of both water quality and coastal VOC concentrations. We begin by using spectral analysis of satellite imagery to identify and classify stormwater plumes using images from two high resolution remote sensing data products. Next, we track the spatial and temporal evolution of these plumes following the rain events. Finally, we assess the impact of these runoff events on marine atmospheric emissions, focusing on marine VOCs as a key indicator. To ensure the accuracy of our observations, we validate changes in remotely sensed turbidity with in situ water quality measurements. By integrating these data sources, we aim to develop modified emissions inventories tying runoff events to air quality impacts. This research highlights the potential of combining remote sensing and in situ data to enhance our understanding of water quality dynamics and their environmental implications in coastal environments. Our findings are expected to contribute to improved pollution management practices and support efforts to protect coastal ecosystems through real-time monitoring of plume behavior and resulting marine emissions.