Department Seminar: Qindan Zhu

Title: Decoding Urban Ozone Pollution: Emissions, Chemistry and Policy Implications

Abstract: Ground-level ozone is a major secondary pollutant that leads to negative impacts on human health and the ecosystem. Despite decades of contingent emission control measures aimed at improving air quality, many counties in US continue to experience severe ozone pollution during summertime, emphasizing the need for further regulatory actions to address air pollution. My research decodes the urban ozone pollution from its chemistry and emissions and discusses its policy implications. First, I utilize machine learning and satellite remote sensing to predict surface OH in 49 North American cities. Using OH as a proxy for ozone production rate, I conclude that 75% of these cities are in the NOx limited regime, prioritizing further controls on NOx emissions to regulate ozone. Second, I utilize airborne flux measurements to estimate the cultivated soil NOx emissions and show that current soil NOx schemes applied in air quality modeling significantly underestimate the soil NOx emissions in the San Joaquin Valley. Lastly, I update an air quality model to accurately simulate O3 chemistry in Los Angeles and use the model to conduct a thorough sensitivity analysis of the impact of the zero-emission vehicle regulation on O3 pollution. I demonstrate that the zero-emission vehicle regulation would benefit both air pollution and climate change in Los Angeles. Looking ahead, I aim to study the interaction between air pollution and climate change, especially focusing on weather-sensitive emissions and multi-scale OH chemistry.