Appendix IV . General Recommendations for Air Quality Improvement

Urban vegetation can directly and indirectly affect local and regional air quality by altering the urban atmosphere environment . Four main ways that urban trees affect air quality are ( Nowak 1995 ):

• Temperature reduction and other microclimate effects

• Removal of air pollutants

• Emission of volatile organic compounds ( VOC ) and tree maintenance emissions

• Energy effects on buildings

The cumulative and interactive effects of trees on climate , pollution removal , and VOC and power plant emissions determine the impact of trees on air pollution . Cumulative studies involving urban tree impacts on ozone have revealed that increased urban canopy cover , particularly with low VOC emitting species , leads to reduced ozone concentrations in cities ( Nowak 2000 ). Local urban management decisions also can help improve air quality .

Urban forest management strategies to help improve air quality include ( Nowak 2000 ):
Strategy	Result
Increase the number of healthy trees	Increase pollution removal
Sustain existing tree cover	Maintain pollution removal levels
Maximize use of low VOC-emitting trees	Reduces ozone and carbon monoxide formation
Sustain large , healthy trees	Large trees have greatest per-tree effects
Use long-lived trees	Reduce long-term pollutant emissions from
planting and removal
Use low maintenance trees	Reduce pollutants emissions from maintenance
activities
Reduce fossil fuel use in maintaining vegetation	Reduce pollutant emissions
Plant trees in energy conserving locations	Reduce pollutant emissions from power plants
Plant trees to shade parked cars	Reduce vehicular VOC emissions
Supply ample water to vegetation	Enhance pollution removal and temperature
reduction
Plant trees in polluted or heavily populated areas	Maximizes tree air quality benefits
Avoid pollutant-sensitive species	Improve tree health
Utilize evergreen trees for particulate matter	Year-round removal of particles

I-Tree Report of Ecosystem Analysis at Mount Auburn Cemetery Insert to the Climate Action and Sustainability Plan

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Climate Action and Sustainability Plan June 2021 | Page 126

Appendix IV . General Recommendations for Air Quality Improvement