Gas-Part - Gas/Particle Partitioning Why is gas/particle...

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Unformatted text preview: Gas/Particle Partitioning Why is gas/particle partitioning important? Dispersion of Pollutants Introduced into the Atmosphere as Determined by Residence Times (Husar and Patterson, 1980) Washout by rain: p g air rain T W W C C W +- = = ) 1 ( Washout consists of capture of gas and particle phases Gases equilibrate with rain via Henrys Law (reversible air-water exchange) Particles are irreversibly captured For PCBs: W g ~ 200-400, W p ~ 10 4 10 5 For PAHs: W g ~ 10-500, W p ~ 10 3 10 6 Atmospheric reactions Many (most?) organic species are reactive in the atmosphere via direct or indirect photolysis Half-lives of PAHs: Gas phase = minutes-hours Particle phase = hours-days How does this contradict figure 1? Health effects: Particles can deposit in lungs. What role does chemical makeup of these particles play? Background of gas/particle distribution Parameters affecting G/P distribution: 1. Chemicals properties (liquid VP, Koa) 2. particle characteristics: size distribution, carbon content, composition 3. Atmospheric conditions: T, RH How do we measure G/P partitioning? Traditional hi-vol air sampler uses a filter to capture particle phase and then an adsorbent to capture gas phase Filters: GFF, QFF, PTFE Adsorbents: PUF, polymer resin, tenax Denuder...
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Gas-Part - Gas/Particle Partitioning Why is gas/particle...

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