Experiment: Caltech Atmospheric Chamber_20150130_METHACROLEIN/Methyl nitrite/10102-44-0_Hydroxyl radical_Ammonium sulfate_RH40%


Name: Caltech Atmospheric Chamber_20150130_METHACROLEIN/Methyl nitrite/10102-44-0_Hydroxyl radical_Ammonium sulfate_RH40%
Date: 2015-01-30

Caltech Atmospheric Chamber

Near/Far Bag 2012-2015 (Tran)

Experiment Set
MPAN, Methacrolein, Isobutyraldehyde, and 231MBO photoxidation experiments

This experiment was done to study the Methacrolein high NO2 photoxidation in the presence of wet ammonium sulfate (AS) seeds at RH 40%, since the other experiments were done at low RH and without seed particles. The hypothesis is that particle liquid water will decrease SOA formation because water will hydrolyze HMML instead of allowing it to oligomerize on the particle surface. This liquid water is also hypothesized to liberate 2-methylgycleric acid (2MGA) from the aerosol to the gas phase.

Interestingly, gas-phase 2MGA is not significantly enhanced and aerosol mass is not significantly decreased in the 40% RH experiment (Exp. #12) compared to the dry experiments. It is possible that the liquid water content under these conditions (∼30 vol%) is not high enough to dominate the reaction with HMML or there is a barrier to 2MGA volatilization. We do see the hypothesis confirmed in the fully deliquesced particle in the 85% RH experiment (150208)

Additional Notes
Equivalent to Exp#12 in the PCCP paper.

Experiment Details


  • Gas phase chemical reaction
  • Aerosol formation
Temperature: 25
Relative Humidity: 40
Seeded Experiment: No
Fuchs Adjusted Surface Area:
Condensation sink rate coefficient: 40
Reaction type:
Oxidant Name: Hydroxyl radical
Initial Oxidant Concentration Value: 2e7 (molecules_per_cubic_centimeter)
RO2 Main Fate: NO2
RO2 Lifetime: (Seconds)
Pressure: 750 Torr

Data Set plots
Choose a file: Choose the X-Axis:

Experiment Set Details

Name: MPAN, Methacrolein, Isobutyraldehyde, and 231MBO photoxidation experiments
Time format and units: Experiment time (minutes, local)
Photoxidation of synthesized methacryloyl peroxynitrate (MPAN) to understand its pathways of SOA formation, leading to 2-methylglyceric acid in the particle phase. It is hypothesized that MPAN produces an unstable intermediate called HMML (hydroxymethyl methyl-a-lactone) that ring opens when it hits a surface, with co-product NO3. Some experiments were done with alpha-pinene as an NO3 scavenger, with the production of pinene nitroxy hydroperoxide (PNP, m/z 316 C10H17NO5) evidence of the alpha-pinene + NO3 chemistry. Photoxidation of methacrolein (MACR) was performed for comparison. Photooxidation of 2-methyl-but-3-ene-1-ol (231MBO) and isobutyraldehyde were performed because they are (or can produce) analogous compounds that will give insight into the oxidation mechanism. Experiments were mainly performed dry and with no seeds, although 2 experiments were performed on with varying particle liquid water on ammonium sulfate (AS) seeds. Note that particle wall loss has already been applied to SMPS data, but the raw data are also provided as well as the wall loss kinetic parameters.


  • Tran Nguyen UC Davis
  • Paul Wennberg Caltech


Principal investigator:

John H Seinfeld
Phone: (626) 395-4635
E-mail: seinfeld@caltech.edu
OrcID: https://orcid.org/0000-0003-1344-4068

Data Manager:

Stephanie Kong
Phone: 626-395-3194
E-mail: wkong@caltech.edu


Reactant Compound type Concentration Concentration units
  • Aldehyde
  • Alkene
200 Parts Per Billion
Methyl nitrite (12231) 200 Parts Per Billion
10102-44-0 (3032552)
  • NOx
180 Parts Per Billion

150130_Timeline.csv Timeline

Local time (hh:mm) Action (Time zero is "Lights On" time)
8:00 turned off heating in the chamber (it was being flushed at 40 celsius overnight)
9:15 Turning instruments on
10:35 Started humidifying the chamber
13:35 Humidity at RH40%
13:50 Started atomizing ammonium sulfate (AS) seeds through a wet wall denuder
13:52 Stopped atomizing and washed the atomizer because mz203 (IEPOX) was going up in the CIMS
14:00 Started atomizing AS seeds again with a new solution of 0.015M AS in water and clean atomizer (mz203 is no longer rising)
15:20 Injecting NO2 (approx 80 ppb)
16:00 Injecting 11.5 torr of CH3ONO (approx 200 ppb)
16:15 Injecting 17 uL of methacrolein (approx 200 ppb)
16:27 All injections stopped
16:35 Lights on 10%
20:10 Lights off
20:15 Filter collection started
1:15 Filter collection stopped

Light Flux Characterizations:
2013-12-13 (#30)
Particle Loss Characterizations:
2013-03-24 (#30)
Vapor Loss Characterizations:

Chamber Details

Name: Near/Far Bag 2012-2015 (Tran)
Volume in cubic meters: 27
Shape: Rectangular Prism
Surface area in cubic meters: 41.8
Flow Mode: Batch
Flow through rate in liters per minute:
Body Material: Teflon
Body thickness: 50
Replacement date:
Replacement frequency: As needed
Cleaning method: Flushing with air
o3 background: 0.5 ppb
nox background: 0.1 ppb for Near, > 0.1 ppb for Far
Particle background in micrograms per cubic meter: < 0.1 ug/m3
Air filtration method: Custom Filter
Mixing method: 0
Mixing method material:
Temparature Control: Yes
Temparature measurements recorded: Yes
Temparature range (min degrees celcius): 20
Temparature range (max degrees celcius): 45
Humidity Control: Yes
Humidity Measurements Recorded: Yes
Relative humidity range (min percent): 5
Relative humidity range (max percent): 100
Particle experiment capability: 1
Lights: Yes
Light source type(s): UVA Black Lamps
Supplemental information: https://www.worldscientific.com/doi/abs/10.1142/9789813147355_0001
Additional Notes: