Trees air-polution


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Air Pollution

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Trees air-polution

  1. 1. Trees & Air Pollution Cool Communities October 22, 2003 Dudley R. Hartel Technology Transfer Specialist USDA Forest Service Athens, Georgia SRS-4901 Southern Center for Urban Forestry Research & Information
  2. 2. Trees & Air Pollution Definitions Processes Resources (to understand & answer questions) New Research
  3. 3. Trees & Air Pollution Definitions VOCs NO x Ozone SMOG Biogenic & Anthropogenic
  4. 4. Trees & Air Pollution VOCs Volatile Organic Compounds Evaporate readily (vaporize) Carbon Many sources Vegetation Solvents, paints Vehicle emissions (benzene)
  5. 5. Trees & Air Pollution VOCs are a Varied Group Harmful (toxic) to health Benzene, PAH (polycyclic aromatic hydrocarbons) Not harmful to health Biogenic (NASA study indicates these may reduce airborne molds & bacteria)
  6. 6. Trees & Air Pollution NO x Emmissions Nitrogen Oxides Soil, lightning, & volcanoes Human activity (combustion) Cars, trucks, electric generation, industry, gasoline powered lawn equipment Fire (i.e. prescribed burning) Heavily fertilized agricultural crops (corn, cotton, wheat)
  7. 7. Trees & Air Pollution Ozone O 3 (3 atoms of Oxygen are combined) Troposphere (up to 10 miles) Stratosphere (10 - 30 miles)
  8. 8. Trees & Air Pollution Ozone Ozone has the same chemical structure whether it occurs high above the earth or at ground level and can be good or bad, depending on its location in the atmosphere. Ozone: Good Up High, Bad Nearby Protects life on earth from the sun’s harmful ultraviolet rays (UV-b) Creates health problems
  9. 9. Trees & Air Pollution SMOG Historically: Industrial SMOG (London 1950s) Smoke + Fog Current: Photochemical SMOG Non-smoke producing combustion NO x & VOC s + Sunlight (Ozone)
  10. 10. Trees & Air Pollution Biogenic Produced by living organisms or biological processes Trees (woody plants) Grass (herbaceous plants) Soil Anthropogenic Human activity (related to use of fossil fuels)
  11. 11. Trees & Air Pollution Pollution Process (requirements) Sunlight Oxides of nitrogen (NO x ) Volatile organic compounds (VOC s ) Temperatures >18 degrees Celsius (64.4F)
  12. 12. Trees & Air Pollution Trees & VOC Emmisions 1 1 grams/tree/day Benjamin & Winer 1998 2.4 0.0 Pistacia chinensis 1.4 0.0 Pinus taeda 0.1 0.9 Quercus rubra 0.1 0.5 Quercus alba 0.4 0.0 Cedrus deodara 0.2 0.0 Acer negundo Monoterpene Isoprene Species
  13. 13. Trees & Air Pollution Two VOC Emission Issues Individual species & trees Benjamin & Winer Landscape level (regional) for air pollution studies Guenther & Geron
  14. 14. Trees & Air Pollution Trees & VOC Emissions Terpenes Isoprene (oak) & monoterpene (pine) YES! Trees Emit VOCs VOC s are not pollutants VOC s + NOx + Sunlight = Problem
  15. 15. Trees & Air Pollution Resources GHASP Galveston-Houston Association for Smog Prevention WWW.GHASP.ORG Trees & Our Air, 1999 Researchers Chris Geron & Alex Guenther Nat’l Center for Atmospheric Research, Boulder, CO Michael T. Benjamin & Arthur M. Winer School of Public Health, UCLA David J. Nowak USDA FS, Syracuse, NY
  16. 16. Trees & Air Pollution New Research & Questions VOC emissions: 2-28x higher than previously recorded (methodology, lab vs. field) for trees May not be dependent on age of tree Canopy level may not be important Considerable variability reported More research needed
  17. 17. Trees & Air Pollution Despite Uncertainty in VOC Data Trees: Do not create pollution! Have a positive effect on UHI Evaporative cooling Shade Cooler temps mean less ozone, less AC Remove particulates & CO 2 Reduce runoff & erosion Have a positive impact on mental health
  18. 18. Trees & Air Pollution Suburban Lawns! Recent research in Australia (Kirstine) Grass & cut grass are important sources of VOC emissions Estimate that about 1/3 of photochemically reactive VOCs in an urban airshed are from grass & grass cutting These emissions should be part of models
  19. 19. Trees & Air Pollution Suburban Lawns! Unlike trees, turf does not: Provide as much evaporative cooling Provide shade (for humans) Reduce energy demand Provide an equivalent (any) pervious surface Provide mental health benefits (no research)
  20. 20. Trees & Air Pollution Urbanization effects on tree growth Jillian W. Gregg, July 10, 2003; Nature Cottonwood NYC and surrounding rural sites Growth better in city Higher rural O 3 levels reduced growth NO x scavenging reactions in the city reduce O 3 levels Urban pollutants effects extend beyond the urban core