Table of Contents
Ecosystems (nature) can filter, fix, and degrade or store air pollutants such as carbon dioxide/oxygen balance, ozone, levels of sulfur oxide, nitrogen oxides, volatile organic compounds, particulates, aerosols that directly affect human health or infrastructure.
Aboveground plant parts (i.e., leaves, bark, and other exposed parts) generally act as persistent absorbers in a polluted environment and trees can intercept air pollutants and act as biological filters.
Tree leaves can filter out particulate matter and many other pollutants from the atmosphere . The average reduction of particulate matter near a tree is between 7-24%.
Transpiration of water during photosynthesis can help to reduce air temperatures, an average reduction of temperature near a tree is up to 2°C.
Wind erosion is reduced with increasing ground cover, additional structural complexity (canopy layers) further reduces particle displacement and increases particle interception. In addition, vegetation can serve as a barrier to the movement of soil dust fronts, thus mitigating the effects of dust storms.
Particulate matter may stick to plant structures (e.g., leaves) and later washed-out to soil, thus reducing the inhalation exposure of people. Trees with a large leaf surface area can remove 60 to 70 times more gaseous pollutants a year than small ones.
Plant leaves absorb many different air chemical compounds that can be harmful for people, contributing to scavenge air pollutants in their organic structure. For instance, plants can absorb atmospheric NO2 and use it as a source of nitrogen in metabolism. Nitrogen and sulphur gases may also be washed out to soils, transformed into other compounds, and be further absorbed by plant roots. Some air pollutants may not be directly absorbed by plant leaves or roots. However, once they are deposited in plant parts (leaves, branches, trunks), free-living or endophytic microorganisms may help to sequester, degrade, or detoxify these compounds into non-toxic forms, which can be further absorbed by plants. Once leaves fall or pollutants are washed out to soils, these processes may also be mediated by soil biodiversity.