Characterizing Ozone Sensitivity to Urban Greening in Los Angeles Under Current Day and Future Anthropogenic Emissions Scenarios

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Abstract Cities are simultaneously implementing urban greening and reducing anthropogenic emissions to combat climate change, but these strategies can have complex and potentially counteracting effects on regional atmospheric chemistry. Urban greening can increase emissions of volatile organic compounds (BVOCs), while climate change mitigation strategies reduce co‐emitted pollutants such as nitrogen oxides (NO x ). The nonlinear relationship between ozone (O 3 ) and BVOC and NO x concentrations makes it crucial to investigate potential interactions between urban greening and anthropogenic emissions reductions. Here, we use regional atmospheric chemistry modeling to assess O 3 sensitivity to a 50% increase in urban vegetation in the Los Angeles Basin. We evaluated potential interactions between urban greening and climate change mitigation by running urban greening simulations with current day and future anthropogenic emissions that reflect renewable energy adoption and electrification in Los Angeles, CA. Our model results show that urban greening increased daily maximum 8‐hr ozone concentrations with higher increases modeled under current day anthropogenic emissions. Urban greening had complex effects on hourly O 3 concentrations, with increased O 3 concentrations up to 0.95 ppb during the day following increased biogenic emissions and reduced urban O 3 concentrations up to 0.41 ppb at night following reduced ventilation of NO x . Under the future anthropogenic emissions scenario, reductions in NO x somewhat mitigated the daytime O 3 penalties of urban greening but also dampened nighttime O 3 reductions. Our results suggest that urban greening will likely have regional O 3 penalties if new vegetation is high isoprene emitting, even as NO x emissions are drastically reduced following climate change mitigation.

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