Quantifying the Relative Ability of Tree Species in Intercepting and Removing Particle Pollution (0897-50-G-43)

This project quantified the relative ability of individual tree species in removing PM 2.5 (fine pollution particulates).

According to the findings by the Natural Resources Defense Council, dust, soot, and many particles in polluted air over the nation's 239 major cities cause 64,000 of premature heart and lung-related deaths each year. In light of the new reports, the Environmental Protection Agency (EPA) has announced the plan to impose tougher restrictions to include fine particulates less than 2.5 microns (PM2.5). The new regulations could cost more than $2.5 billion a year to implement in a city like Chicago alone. Previous studies have indicated that trees in Chicago removed 234 tons of particulate matter less than 10 microns (PM10) annually. To the extend that trees can control particulate pollution there is potential for improved air quality and substantial cost savings. The proposed project will quantify the relative ability of individual tree species in removing PM2.5. Therefore, urban trees can be evaluated by decision makers in terms of dollars saved associated with avoided investment in new control strategies. Quantification of PM2.5 removal is important for integration into the UFORE model being developed.

Statistical analysis indicated that there were significant differences among different tree species in intercepting particulate matter (PM2.5). Duncan Multiple Range Test indicated the relative comparisons of the experimental species interms of their ability to remove PM2.5 (Table 1). Trees can act as efficient biological filters, removing significant amounts of particulate pollution from urban atmospheres. Live Oaks (Quercus virginiana) , River Birch ( Betula Nigra), and Sugar hackberry (Celtis occidentalis) seems to be statistically more efficient at capturing pollutant particles of less than 2.5 microns than species trees such as Red Maple (Acer Rubrum), Southern Magnolia (Magnolia grandiflora), and Sycamore (Platanus occidentalis). It should be noted that even some species indicate better efficiency in removing particle pollution, the total contribution to pollution removal is based on the canopy size as well as age and other plant and environmental factors. Therefore, it is possible that a mature Sycamore tree would contribute more to particle removal than a River Birch tree due to the larger canopy size. There appears to be no significant differences among some species. There appears to be a negative correlation between the species with high total leaf area and their efficiency in removing particles. Species with smaller total leaf areas seems to do a better task of removing particles. However, it should be noted that the leaf morphology of these trees are different. Stomatal conductance and net-photosynthetic capability of trees were affected by the exposure to PM2.5. This was expected as it has been reported by many investigators. Electron microscopy examinations revealed possible morphological characteristics which may play an important role in particle removal.

The main objectives of this project are:

1)To quantify the relative ability of selected urban tree species to remove particulate pollution of less than 2.5 microns (PM2.5)

2)To quantify the detrimental effect of the particulate pollution on the tree species

3)To use modeling techniques for projecting the findings toward mature tree species

4)To develop a management guideline for practical application of the findings

Attachments

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