Urban Greening and Air Quality

This investigation of atmospheric emissions from trees in urban areas will help determine which trees are more likely to act as a source or a sink of air pollutants. Gaseous emissions from urban trees can contribute to the formation of secondary air pollutants, such as ozone and secondary organic aerosol, while urban trees can also provide leaf surfaces for dry deposition serving as a sink for atmospheric particulate matter. Information about which trees are best to plant to help reduce air pollution can inform decisions about tree planting in parks and urban areas. This project includes both field measurements and laboratory experiments with the objectives of assessing: (1) the uncertainties in the emission rates and composition of biogenic volatile organic compounds (BVOCs) in urban areas, and (2) the particle deposition efficiency on different types of leaves and needles (particle deposition leaf resistance). The results will provide a survey of the BVOC emission rates and composition of the top 10 major tree species located in Los Angeles parks and streets and generate a range of different particle leaf resistance values that can be integrated with a resistance framework for particle dry deposition parameterizations. Box modeling will be used to quantify the net effect of urban trees on atmospheric particle number concentrations, size distributions, and mass loadings under a range of urban greening and climate scenarios. Although the results are primarily applicable to the Los Angeles region, the data and methods of this project have broader application to other urban areas. This project also will support the development, testing, implementation, and evaluation of a series of high school curriculum activities focused on urban air quality, environmental justice, and data literacy, coordinated in collaboration with the University of California at Irvine’s Center for Environmental Biology (CEB) and the Orange County Department of Education. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.