| TREES AND AIR QUALITY |
| The right tree can improve air quality as well as provide other benefits such as
shade and beauty. However, some trees can have adverse effects on air quality and, because of their pollens,
can even affect people's ability to breathe. This site provides an introduction to the effects of trees on air
quality and identifies some websites that provide additional information. |
| BENEFITS OF TREES ON AIR QUALITY |
| Trees deliver air quality benefits by the cooling effect of their shade and by removing
certain pollutants. |
| COOLING |
| By cooling, trees reduce evaporative emissions from vehicles and other fuel storage.
By cooling homes and offices, trees reduce power generation emissions. General cooling also reduces the
speed of chemical reactions that lead to the formation of ozone and particulate matter. By using models at
ARB or at the Federal EPA, we can predict how well cooling by trees helps improve air quality. |
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Sacramento Shade
provides an excellent website to learn about the savings in energy and air quality, as well as the real estate
enhancements that trees can provide. The site is located at: http://www.smud.org/en/residential/trees.
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| POLLUTANT REMOVAL OR DEPOSITION |
| Leaves and needles have surface area that can allow for removal (deposition) of ozone,
nitrogen dioxide, and to a lesser extent particulate matter. Several different factors affect pollutant removal.
These factors include how long a parcel of air is in contact with the leaf, the amount of leaf area, as well
as the specific pollutant of interest. Because deposition has an affect on air quality, the Air Resources Board
(ARB) is interested in this phenomenon. For example, the ARB support a study to evaluate how well agricultural
crops remove ozone. For more on the California Ozone Deposition Experiment (CODE) please refer to: http://blg.oce.orst.edu/code91/twinotter/description/synopsis.html. |
| In addition, an excellent discussion of the impact of trees on ozone removal can
be found for Blodgett Forest
at: http://www.cnr.berkeley.edu/forestry/. |
| ADVERSE EFFECTS OF TREES ON AIR QUALITY |
| Trees can also have adverse effects on air quality by their release of compounds,
which can react to form ozone and particulate, and by the release of allergens such as pollen. |
| BIOGENIC EMISSIONS |
| Trees emit hydrocarbons (biogenic emissions) which can react with nitrogen oxides
that are emitted by sources such as cars and power plants to form ozone and particulate matter. These
biogenic hydrocarbons are sometimes even more efficient in forming ozone than those hydrocarbons emitted from
cars and power plants. A description of these emissions at a California site can be found at: http://www.cnr.berkeley.edu/forestry/. |
| Further the national biogenic modeling
effort is described at: http://www.ladco.org. |
| BIOGENIC ALLERGENS |
| Pollen from grasses, weeds, shrubs, and trees causes allergic reactions in sensitive
people. Some molds that grow on trees can also cause allergic reactions. Allergic responses have a wide spectrum
of effects but can be as severe as an acute asthma attack. |
| More information can be found at the National
Allergy Bureau's website at: http://aaaai.org/nab/. |
| TREE SELECTION |
| Tree advocacy groups are an excellent source for information to assist with tree
selection for planting. One such group, SelecTree for California, maintains a database that allows homeowners
and businesses to select a tree that meets their needs based on a variety of factors. The website is
located at: http://selectree.calpoly.edu/. |
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For further information, please contact: Ash Lashgari at (916) 323-1506.
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