1. TOGA (Trace Organic Gas Analyzer)
Eric Apel, Alan Hills, Rebecca Hornbrook (ACOM/NCAR)
with frequent participation from the UCI Blake group
2 min continuous analysis of >50 VOCs
wide dynamic range, with detection limits at low pptv to sub-pptv range
samples processed in flight using fast online GC/MS
Post-processing of full data files takes ~ 2-3 days.
VOC tracers from several sources/types:
Biogenic VOCs and oxidation products
Anthropogenic VOCs
Oil and Gas Tracers
Long-lived Halogenated VOCs
Short-lived Halogenated VOCs
OVOCs, including HCHO
DMS
Alkyl Nitrates
Biomass burning tracers (HCN, CH3CN)
TOGA is the trace organic gas analyzer, which is a fast GC-MS that does continuous simultaneous measurements of 50 + VOCs. It has a wide dynamic range with low ppt to sub-ppt detection limits. Samples are quick-processed in flight, and full post-processing takes about 2-3 days.
VOCs provide tracers for several different sources, including biogenic VOCs, industrial and urban, O&G, oxidation products, including formaldehyde, DMS, alkyl nitrates and biomass burning.
Installed on the G-V
NCAR/ACOM TOGA group
ATom Science Team Meeting

2. Long vs. short lived compounds
Specific chemical compounds and groups of compounds are useful for isolating and understanding different physical and chemical processes
Long vs. short lived compounds
Compounds specific to different sources: emissions/ratios
Some chemical compounds or groups of compounds are useful for understanding different physical or chemical processes, such as comparing long and short-lived compounds, looking at emission ratios to identify different sources, comparing parent and oxidation products, and contrasting soluble and insoluble compounds.
Compound oxidation products
Soluble and insoluble compounds

3. …but we need to know up front!
TOGA Measured Compounds
NMHCs:
1-butene/isobutene
propane
isobutane
n-butane
isopentane
n-pentane
2-methylpentane
3-methylpentane
n-hexane
n-heptane
benzene
toluene
ethylbenzene/p-/m-xylene
o-xylene
1,2,3-trimethylbenzene
1,2,4-trimethylbenzene
Alkyl Nitrates:
methyl nitrate
ethyl nitrate
isopropyl nitrate
butyl nitrates
LOD; pptv 1 10
0.5 3
0.3
0.2 5
OVOCs:
formaldehyde (HCHO)
acetaldehyde (CH3CHO)
propanal
butanal
acetone (CH3COCH3)
MEK (butanone)
methanol (CH3OH)
ethanol (C2H5OH)
2-propanol
acrolein (CH2CHCHO)
MTBE (methyl tert-butyl ether)
Biogenic VOCs:
isoprene
MBO (2-methyl-3-buten-2-ol)
MVK
methacrolein
3-methylfuran
a-pinene
b-pinene
camphene
limonene/3-carene 20
Halogenated VOCs:
CFC-11 (CCl3F)
CFC-113 (CCl2FCClF2)
CH3Cl (methyl chloride)
CH2Cl2 (dichloromethane)
CHCl3 (chloroform)
CCl4 (tetrachloromethane)
C2Cl4 (tetrachloroethene)
C6H5Cl (chlorobenzene)
CH3Br (methyl bromide)
CH2Br2 (dibromomethane)
CHBr3 (bromoform)
CH3I (methyl iodide)
CH2I2 (diiodomethane)
C2H5I (ethyl iodide)
CH2ICl (chloroiodomethane)
CHBrCl2 (bromodichloromethane)
CHBr2Cl (dibromochloromethane)
Others:
DMS (dimethyl sulfide)
HCN (hydrogen cyanide)
Acetonitrile (CH3CN)
0.1
0.03
0.05
0.07
This is a list of all the compounds that we are currently able to quantify with TOGA, and the actualy targetted list for a given project can be tailored to best suit the experiment. The catch is that we need to plan the targetted list prior to the project, so if there are specific compounds that you’d like to see, please let us know well before the first deployment.
Targeted VOCs can be modified and tailored to best suit objectives of experiment.
…but we need to know up front!
NCAR/ACOM TOGA group
ATom Science Team Meeting

4. TOGA Species Measured and Lifetimes
Reactivity with OH
105 OH (low), 107 OH (high), 210K, 310K
TOGA species
Hours
Halocarbons
Sulfur Containing
Nitriles
Oxygenates
This is just another way of looking at the TOGA species, by OH reactivity lifetime. We measure compounds that range in lifetime from minutes to several months or even years.
Biogenics
Aromatics
Alkenes
Alkanes
NCAR/ACOM TOGA group
ATom Science Team Meeting

5. Aqueous phase interactions
Solubilities
Aqueous phase interactions
We are also considering compounds with different solubilities. For the most part, the hydrocarbons are effectively insoluble, but some nitriles and OVOCs have solubilities that are relevant to atmospheric processes.
NCAR/ACOM TOGA group
ATom Science Team Meeting

6. CAM-chem – predicts CO plume
Observations of tracers for air mass characterization during CONTRAST
CAM-chem – predicts CO plume
TOGA BB tracers:
HCN, acetone, acetonitrile
(lifetimes > 1 week)
This is an example of how TOGA compounds were used to characterize an air mass during CONTRAST. In the chemical forecast, CAM-chem was predicting a CO plume just north of Guam. When we intersected the region, we saw our BB tracers all responding, like acetone, HCN and acetonitrile. Other TOGA tracers with shorter lifetimes were helpful to constrain the age of the BB emissions.
Additional TOGA tracers with different lifetimes constrain age of air mass.
NCAR/ACOM TOGA group
ATom Science Team Meeting

7. Observations of North-South VOC gradients during CONTRAST (RF14)
Flight to Australia
Clear evidence of convective
influence near New Guinea
Benzene
Extremely clean air near Australia
Benzene
During the CONTRAST project, we flew from Guam down to 20°S between 12 and 15 km. These plots show the TOGA benzene observations from this time period. And you can see that while we were near New Guinea there were some higher concentrations due to convection, but further south, we encountered very low concentrations.
NCAR/ACOM TOGA group
ATom Science Team Meeting

8. Observations of North-South VOC gradients during CONTRAST (RF14)
TOGA
benzene
toluene
acetaldehyde
CAM-chem captures the benzene spatial distribution well – note the low values in SH
NCAR/ACOM TOGA group
ATom Science Team Meeting

9. TOGA Curtain Plots - CONTRAST
TOGA has the time resolution to do meaningful vertical profiles. We hope to use these data to understand the global budgets of a lot of the species we measure, including longer-lived species like acetone and shorter lived species like bromoform.
NCAR/ACOM TOGA group
ATom Science Team Meeting

10. TOGA Curtain Plots - CONTRAST
Main point for showing each of these compounds – tetrachloroethylene – anthropogenic tracer, HCN – BB tracer.
NCAR/ACOM TOGA group
ATom Science Team Meeting

11. TOGA Calibration Procedure
Overflow inlet during zeros/cals
In-flight Calibration system
TOGA Inlet
For our in flight calibration, we draw in and “clean” outside air through a (?) catalyst, and we add standards to generate a mixture with mid- to high-ppt concentrations of a number of VOCs, and then we overflow the inlet during this time. So this would be the only time that we send VOCs out through our inlet, which I know is a concern for any sampling inlets behind our inlet. So we can possibly do some sensitivity studies during a test flight, and plan coordinated calibrations during flights.
NCAR/ACOM TOGA group
ATom Science Team Meeting

12. Instrument status: Good
TOGA Instrument Status, Logistics and Payload Concerns
Instrument status: Good
Data: Normally report 10 – 15 compounds in flight near real time:
e.g. HCHO Acetone HCN
Acetaldehyde Methanol CH3CN
Butane DMS EtONO2
Benzene C2Cl4 i-PrONO2
Toluene CHCl3
Logistics: TOGA LN2 lasts ~ 10 hours , request possibility for in-flight LN2 addition
NCAR/ACOM TOGA group
ATom Science Team Meeting

13. Reminder: request specific compounds for TOGA to quantify
AND, for the 24-h data deadline, we can provide a subset of
high interest VOCs.
NCAR/ACOM TOGA group
ATom Science Team Meeting

15. TOGA Calibration and Standards
TOGA – Calibrations – in-house – NIST – NOAA standards
Compares well with established measurements – even at low mixing ratios
NMHC examples (CONTRAST comparison with AWAS – Atlas)
NCAR/ACOM TOGA group
ATom Science Team Meeting

16. TOGA Calibration and Standards
Halogenated species examples
NCAR/ACOM TOGA group
ATom Science Team Meeting

17. GC/MS - SIM NSF/NCAR Gulfstream V NSF/NCAR C130 TOGA Inlet TOGA on GV
Acetaldehyde
Isopentane
Butane
Methanol+Ethanol
Pentane
GC/MS - SIM
Acetone
Isobutane
Dichloromethane
Butanal, MEK
CH2O
Chloroform
Benzene
Toluene
Ethylbenzene+Xylenes