1. INVESTIGATION OF INTERACTIONS BETWEEN GLYCOLS AND AEROSOLS FOR AVAILABILITY ASSESMENTBy
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
W. P. L. Carter /21/2018
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.
W. P. L. Carter /21/2018
Studies of Interactions of VOCs with Aerosols

3. RESULTS OF GLYCOL DARK DECAY EXPERIMENT
G:\txt\epacham\SCAQMD\availexp.xls “EPA315 Glycol decay” sheet. Size=100%
W. P. L. Carter /21/2018
Studies of Interactions of VOCs with Aerosols

4. REACTIVITY DATA FOR ETHYLENE AND PROPYLENE GLYCOLS
G:\txt\epacham\RctTalk.xls “Glycols” sheet
Dry air. No seed aerosol
W. P. L. Carter /21/2018
Studies of Interactions of VOCs with Aerosols

5. EFFECT OF AEROSOL AND HUMIDITY ON GLYCOL OZONE REACTIVITY
No base data in added aerosol runs because of limited humidification and aerosol generation capacity.
G:\TXT\EPACHAM\RCTTALK.XLS “Glycl Avail Expts” sheet. Size=120%
W. P. L. Carter /21/2018
Studies of Interactions of VOCs with Aerosols

6. Studies of Interactions of VOCs with Aerosols
GLYCOL DECAY RATES IN REACTIVITY RUNS: COMPARISON WITH LITERATURE K(OH) VALUE
G:\TXT\EPACHAM\SCAQMD\GlyKoh.xls “PR-GLYCL” sheet. Scale=135%
W. P. L. Carter /21/2018
Studies of Interactions of VOCs with Aerosols

7. Studies of Interactions of VOCs with Aerosols
GLYCOL DECAY RATES IN REACTIVITY RUNS: COMPARISON WITH LITERATURE K(OH) VALUE
G:\TXT\EPACHAM\SCAQMD\GlyKoh.xls “PR-GLYCL” sheet. Scale=135%
W. P. L. Carter /21/2018
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.
W. P. L. Carter /21/2018
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.
W. P. L. Carter /21/2018
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
W. P. L. Carter /21/2018
Studies of Interactions of VOCs with Aerosols

11. DISCUSSION OF PROPOSED VOC 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
Dave Cocker says detection limit is 2.2 ng/m3. Cocker says this is 0.5 ppb for MWT=100 and T=300K.
W. P. L. Carter /21/2018
Studies of Interactions of VOCs with Aerosols