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INVESTIGATION OF INTERACTIONS BETWEEN GLYCOLS AND AEROSOLS FOR AVAILABILITY ASSESMENT

This study aims to determine if aerosols affect the gas-phase consumption rates and reactivities of glycols. Chamber experiments are conducted with and without seed aerosols to assess the reactivity and utility of glycols. Preliminary results show no measurable effects of seed aerosol. The proposed next step is to investigate VOC uptake on aerosols.

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INVESTIGATION OF INTERACTIONS BETWEEN GLYCOLS AND AEROSOLS FOR AVAILABILITY ASSESMENT

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  1. INVESTIGATION OF INTERACTIONS BETWEEN GLYCOLS AND AEROSOLS FOR AVAILABILITY ASSESMENT By William P. L. Carter CE-CERT, University of California, Riverside • Objective: Determine if aerosols affect gas-phase consumption rates and reactivities of glycols • Approach: Conduct chamber experiments with ethylene glycol and propylene glycol with and without seed aerosols added. • Funded by: SCAQMD project to assess glycol reactivity and utility of chamber studies for availability assessment. • Results: No measurable effects of seed aerosol observed • Proposed next step: Investigate VOC uptake on aerosol Studies of Interactions of VOCs with Aerosols

  2. SUMMARY OF CHAMBER EXPERIMENTS • ROG - NOx ambient surrogate irradiations with and without ethylene and propylene glycols in dry air and no aerosol. • Characterization experiments to determine if humidity and aerosol changes chamber background effects • Dark decay experiments with ethylene and propylene glycol with 10 g/m3 (NH4)2SO4 seed aerosol at 35% RH. • ROG – NOx ambient surrogate irradiation with added propylene glycol with 9 g/m3 (NH4)2SO4 seed aerosol at 25% RH. • ROG – NOx ambient surrogate irradiation with added ethylene glycol with 7 g/m3 NH4HSO4 seed aerosol at 30% RH. • Note: Limited aerosol generation and humidification capacity. Seed and humidity could be added to only one reactor at a time. Studies of Interactions of VOCs with Aerosols

  3. RESULTS OF GLYCOL DARK DECAY EXPERIMENT Studies of Interactions of VOCs with Aerosols

  4. REACTIVITY DATA FORETHYLENE AND PROPYLENE GLYCOLS Dry air. No seed aerosol Studies of Interactions of VOCs with Aerosols

  5. EFFECT OF AEROSOL AND HUMIDITY ONGLYCOL OZONE REACTIVITY No base data in added aerosol runs because of limited humidification and aerosol generation capacity. Studies of Interactions of VOCs with Aerosols

  6. GLYCOL DECAY RATES IN REACTIVITY RUNS: COMPARISON WITH LITERATURE K(OH) VALUE Studies of Interactions of VOCs with Aerosols

  7. GLYCOL DECAY RATES IN REACTIVITY RUNS: COMPARISON WITH LITERATURE K(OH) VALUE Studies of Interactions of VOCs with Aerosols

  8. PRELIMIARY CONCLUSIONS AND DISCUSSION • No clear effect on glycol consumption rate or ozone reactivity for humidity up to 35% and (NH4)2SO4 or NH4HSO4 seed aerosol up to 10 mg/m3. • But there still may be a measurable effect at higher humidity or aerosol concentration, with a different type of aerosol • Upgrades are being made to the chamber facility to facilitate experiments at higher RH, aerosol levels. • But experiments that measure increases in aerosol mass when exposed to gas-phase VOCs may give a more sensitive measure of VOC uptake on aerosols at lower cost • Knowledge of VOC uptakes can serve as a basis for planning additional environmental chamber and other studies. Studies of Interactions of VOCs with Aerosols

  9. DIAGRAM OF PROPOSED INSTRUMENTATION TO MEASURE VOC UPTAKE ON AEROSOL Aerosol Generator First DMA (Selects one size) Could be based on injector for HONO flow system VOC Source (known concentration) Reactor (exposed for known time) VOC analysis (GC or total Carbon) Second DMA Measures size distribution Change DMA = Differential Mobility Analyzer. Selects aerosol size and measures size distribution. Studies of Interactions of VOCs with Aerosols

  10. DETERMINATION OF VOC UPTAKE Increase in total particle volume indicates growth of aerosol due to VOC uptake Original size distribution (From aerosol generator) DDp After reactor, reported by 2nd DMA Particles per unit volume After First DMA Particle Diameter Studies of Interactions of VOCs with Aerosols

  11. DISCUSSION OF PROPOSEDVOC UPTAKE DETERMINATION STUDY • Method should be able to detect VOC uptakes as low as ~3 ng/m3 (less than 1 ppt in gas phase, depending on MWt.) • Can be used to study effect of uptake on: • Nature of VOC • Nature of aerosol • VOC concentration • Estimated costs: • Set-up: less than $20K • Measurements: Approximately $500 per test • Less than $30K for proposed program with at least 20 tests • Data obtained may serve as a basis for planning most useful types of environmental chamber and other experiments Studies of Interactions of VOCs with Aerosols

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