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Atmospheric Deposition of Air Toxics

Atmospheric Deposition of Air Toxics. Matt F. Simcik Division of Environmental and Occupational Health School of Public Health University of Minnesota. Why should we care about Atmospheric Deposition of Air Toxics?. Atmospheric Deposition is the only source to remote areas such as the

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Atmospheric Deposition of Air Toxics

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  1. Atmospheric Deposition of Air Toxics Matt F. Simcik Division of Environmental and Occupational Health School of Public Health University of Minnesota

  2. Why should we care about Atmospheric Deposition of Air Toxics? Atmospheric Deposition is the only source to remote areas such as the National Parks from EPA website

  3. The Atmospheric System Source(s) Transport Deposition Transformation Wet Combustion Volatilization Gas Gas-Particle Partitioning Particle Dry Cloud Scavenging Gas Reaction/Loss Particle OH Radical Photolysis

  4. Sources Combustion Produces both gas and particle phase toxics PCDDs/PCDFs PAHs Volatilization Produces only gas phase toxics DDT PCBs

  5. Transformations Gas-Particle Partitioning Cg Cp Controls fate of contaminant Governed by vapor pressure of toxic and amount of particles in air from Simcik 2001

  6. Transformations Cloud Scavenging from Simcik 2001

  7. Reaction/Loss • Reaction with the OH radical is predominant loss mechanism for most air toxics • Most reactions occur fastest in the gas phase • Reaction products can be more toxic than parent compounds

  8. Dry Particle Deposition from EPA website Dry deposition flux = Concentration on particles times deposition velocity. Deposition velocity is a function of particle size Typical value of 0.2 cm/s is often used.

  9. Dry Gas Deposition to Terrestrial Surfaces Cg Living plants, soils, and detritus represent a huge amount of surface area available for sorption of gas phase toxics. In particular, waxy, organic surfaces can take up a large amount of lipophilic contaminants.

  10. Wet Deposition from EPA website Wet deposition is best done as total deposition (dissolved and particle)

  11. Questions that need to be answered • What are the current atmospheric loadings of air toxics to the National Parks? • How do loadings compare to other areas? • What is the historical deposition of air toxics to the National Parks? • Are there any adverse effects of atmospheric deposition of air toxics?

  12. Loadings Estimation

  13. Air Sampling HI-Vol Air Sampler This provides an operationally defined gas and particle phase Typical 24 hour volumes of 720 m3

  14. Alternatives to HI-VOL Samplers

  15. Historical Deposition Lake sediments have often been used to investigate the historical deposition of toxic contaminants.

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