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

Abstract

AbstractCities 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 (NOx). The nonlinear relationship between ozone (O3) and BVOC and NOx concentrations makes it crucial to investigate potential interactions between urban greening and anthropogenic emissions reductions. Here, we use regional atmospheric chemistry modeling to assess O3 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 O3 concentrations, with increased O3 concentrations up to 0.95 ppb during the day following increased biogenic emissions and reduced urban O3 concentrations up to 0.41 ppb at night following reduced ventilation of NOx. Under the future anthropogenic emissions scenario, reductions in NOx somewhat mitigated the daytime O3 penalties of urban greening but also dampened nighttime O3 reductions. Our results suggest that urban greening will likely have regional O3 penalties if new vegetation is high isoprene emitting, even as NOx emissions are drastically reduced following climate change mitigation.