Determination of OH
Concentration in San
Joaquin Valley
Benjamin Nault
SARP 2010
Senior Chemistry Major,
Purdue University
Why San Joaquin Valley?
Valley has multiple issues from emissions,
topography, agriculture, climate and
population growth
Valley has been tagged as a non-attainment
area for PM2.5, PM10, and hourly O3
Why OH radical?
OH radical is said to be the detergent of the
atmosphere
OH radical is the initial step for oxygenating
hydrocarbons
How OH is made
O3 + hv O(1D) + O2
O(1D) + H2O 2OH•
Photolysis of aldehydes (e.g., formaldehyde)
O3 reaction with alkenes
Simple Reaction Schemes (Atkinson 2000)
OH• + RH R• + H2O
R• + O2 RO2 •
RO2 • + NO RO • + NO2
RO • + O2 carbonyl + HO2
HO2 + NO OH • + NO2
Net: OH • + RH + 2NO carbonyl + 2NO2 + OH •
NO2 + hv NO + O(3P)
O(3P) + O2 + M O3 + M
Experimental Procedure
Two flights in DC-8
June 29, 2010 and July 1, 2010
Only used data below 5000 pressure feet
Collect samples every 2 minutes in 2 liter
evacuated canisters to a pressure of 40 PSIG
Experimental Procedure, cont.
Two different analysis used for data
Analysis of Chromatograms
Draw in baselines
Find area of standard (of known mixing ratio
(MR))
Response Factor (RF) = areastnd/MRstnd
Find area of sample
MRsample = Areasample/RF
Analysis for other necessary parameters
Went to CARB website (www.arb.ca.gov)
Temperature data from Eric
Determined Values for other Parameters
June 29 Flight July 1 Flight
Average 303.6(±2.9)K 299.5(±3.7)K
Temperature
Average [O3] 58.9(±9.4)ppb 55.5(±15.7)ppb
1.32x1012 molec/ 1.26x1012 molec/
cm3 cm3
Methodology of determining [OH]
Fully described in Jobson et al., 1998, 1999,
Williams et al., 2000, Karl et al., 2001 and
Bartenbach et al., 2007
Junge 1974: RSD = 0.14/ τ
τ = 1/e = 1/kI[i]*time
σ(ln(xi)) = A* τ i-b
Determination of [OH]
Plotted σ(ln(xi)) versus lifetime (τ) in days
τ = 1/([OH]*kOH,i*86400 s + hv*86400 s)
τ = 1/([OH]*kOH,i*86400 s + hv*86400 s +
[O3]*kO3,i*86400 s)
Rate constants from Karl et al., 2001,
Atkinson 2003, Atkinson and Arey 2003,
Martinez et al.,1992, and Atkinson et al.,
2006.
Example of a graphs
Results and Analysis
06/29 Flight 07/01 Flight
[OH] 2.5x106 molec/cm3 2x106 molec/cm3
R2 0.290363 0.367349
F test 5.73 > Fcrit,95 4.60 8.71 > Fcrit,95 4.54
Discussion—Comparison (σ(ln(x))=A*τ-b
A b
06/29 Flight 0.56±1.10 0.17±0.07
07/01 Flight 0.56±1.13 0.23±0.08
Boulder (Jobson 3.04±0.24 0.28±0.02
1998)
Hohenpessenburg 0.48±0.06 0.24±0.06
(Bartenbach 2007)
PEM-West B (Williams 4.3±0.6 0.53±0.02
2000)
Only measurement: ~1x107 molec./cm3 (0.44 pptv)
Data from Brune, PSU, 2008 ARTCAS
Conclusion
To my knowledge, first [OH] estimated in San
Joaquin Valley
Determined [OH] were 2.5x106 and 2 x106
molec/cm3
Most compounds lost through transportation
Relatively well mixed
Future Work
Have [O3] and [NOx] measured during flight
In situ measurements of OH for the San
Joaquin Valley
Try other methods to determine [OH]
Acknowledgements
Professor Don Blake
Matthew Gartner
Eric Buzay
Grad Mentors
Blake/Rowland Group
Air Group
Rick Shetter
Jane Peterson
Speakers
DC-8 Flight Crew
References
Atkinson, R. Atmospheric chemistry of VOCs and NOx. Atmos. Environ., 2000, 34, 2063 – 2101.
Atkinson, R. Kinetics of the gas-phase reactions of OH radicals with alkanes and cycloalkanes.
Atmos. Chem. Phys., 2003, 3, 2233 – 2307.
Atkinson, R., et al. Evaluated kinetic and photochemical data for atmospheric chemistry: Volume
II – gas phase reactions of organic species. Atmos. Chem. Phys., 2006, 6, 3625 – 4055.
Atkinson, R. and J. Arey. Atmospheric degradation of volatile organic compounds. Chem. Rev.,
2003, 103, 4605 – 4638.
Bartenbach, S., et al. In-situ measurements of reactive hydrocarbons at Hohenpeissenberg with
comprehensive two-dimensional gas chromatography (GCxGC-FID): use in estimating HO and
NO3. Atmos. Chem. Phys., 2007, 7, 1 – 14.
California Environmental Protection Agency Air Resource Board.
Jobson, B. T., et al. Spatial and temporal variability of nonmethane hydrocarbon mixing ratios
and their relation to photochemical lifetime. J. Geophys. Res., 1998, 103, 13,557 – 13,567.
Karl, T., et al. Variability-lifetime relationship of VOCs observed at the Sonnblick Observatory
1999—estimation of HO-densities. Atmos. Environ., 2001, 35, 5287 – 5300.
Jobson, B. T., et al. Trace gas mixing ratio variability versue lifetime in the troposphere and
stratosphere: Observations. J. Geophys. Res., 1999, 104, 16,091 – 16,113.
Junge, C. E. Residence time and variability of tropospheric trace gases. Tellus, 1974, 26, 477 –
488.
Martinex, R. D., et al. The near U.V. absorption spectra of several aliphatic aldehydes and
ketones at 300K. Atmos. Environ., 1992, 26A, 785 – 792.
Williams, J., et al. Variability-lifetime relationship for organic trace gases: A novel aid to
compound identification and estimation of HO concentrations. J. Geophys. Res., 2000, 105,
20,473 – 20,486.
Questions?
Extra Material
Checked for other radical chemistry
Jobson 1994
Derivation of Jobson Method (Jobson
1998)
At low variability, σ(ln(xi)) = RSD, but for high
variability, σ(ln(xi)) gives simpler behavior
ln(Xi/Xi0) = - t / τ
σ y2 = (δ/ δt ln(Xi/Xi0))2 σ t2 = (- t / τ)2 σ t2
σ y = σ(ln(xi)) = (1/ τ) * σ t
Other Plots
Lifetime
4000000
10.84837 Ethane (E)
0.32252 Ethene (E)
2.526291 Propane (B/E)
0.097568 Propene (E)
1.32801 i-Butane (B/E)
1.188886 n-Butane (B/E)
0.616576 n-Pentane (B/E)
0.541654 n-Hexane (E)
2.343097 Benzene (E)
0.184381 Acetaldhyde
8.711211 Acetone
0.616576 i-Pentane
0.541654 2-Methylpentane
0.541654 3-Methylpentane
0.528785 Toluene
12.05633 CO
