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Visit at the LSCE
• Presentations
– Overview of the LSCE and the CAE Team
– The PTR-MS
– The OH reactivity
• Workshop on PTR-MS and OH reactivity (2 groups:
20min+20min)
• Visit at the SIRTA Station (2 groups/20 min each)
1
Climate and Environment Sciences Laboratory
5 axes of research
• Dynamics and climate archives:
• Climate modeling, biogeochemical cycles and their interactions
• Transfers and Tracers in the Environment
• Atmospheric composition and surface fluxes
+ Interactions Human-Climate-Environment
300 people, including 150 permanent
2
Air q
ua
lityC
lima
teM
arin
e
Bio
ge
och
em
istry
Photochemistry, aging,
deposition
Experimental Atmospheric Chemistry (CAE) Team
Characterization of reactive gases (VOC) and aerosols
3
Permanent Researchers: B. Bonsang, V. Gros, J. Sciare, C. Boissard , F:Dulac
Engineers: R.Sarda-Estève, N.Bonnaire, D.Baisnee
PhD students: J-E. Petit, A. Baudic, A-C. Genard, Nora Zannoni, Cerise Kalogridis
Post-Doc: V. Crenn
CAE TeamIntensive Measurement campaigns & Long-term Observations
Urban RuralRemote
PARIS city center/MEGAPOLI
PARIS tunnel-ring road
Ile-de-France/ACTRIS
Oak Forest in
South France
Crete and Corsica
ChArMeX
Amsterdam island
ANR CANOPEE/
ChArMeX
4
The Mediterranean region
ChArMEx: Chemistry-Aerosol Mediterranean Experiment
Ozone levels in the tropospheric column- Summer 2000-satellite GOME (Dobson Unit)
• Almost enclosed sea surrounded by very urbanized
littorals
• Emissions and reactivity of BVOCs enhanced due to
high temperatures and sunny conditions :
• Models predicts ozone increases in the future
• Interest for the SOA production
• Region Sensible to climatic change (IPCC, 2007)
ChArMEx aim: scientific assessment of the present and future
state of the atmospheric environment and of its impacts in the
Mediterranean basin
Target: particulate and gaseous tropospheric trace species
Measurements sites:
• Oak Observatory of Haute Provence (FRANCE) –2012/2014:
• Finokalia (Crete-GREECE)- FAME 2011
• Cap Corse (France)- CHARMEX 2013
Study the photooxidation of BVOCs and its impact on ozone
production
• (Malta, Sardignia..)
5
Volatile Organic Compounds
6
VOC measurements
by Proton-Transfer Reaction Mass Spectrometer (PTR-MS)
• Online technique for measuring VOC concentrations
• Developed at the University of Innsbruck
(Hansel et al., Int. J. Mass Spectrom., 1995; Lindinger et al., Int. J. Mass Spectrom.,
1998)
• Commercial quadrupole and time-of-flight instruments
• Very sensitive ( few pptv)
• Measure in real time (>100 ms)
• No sample preparation
• Measure sequentially a wide range of VOCs (1-512 amu)
7
PTR-QMS Operation
8
PTR-QMS Operation
H2O
The Ion Source:
• Soft Ionization: formation of H3O+
• Very low impurity content< 1% (mainly O2+): No need for mass filter
• High intensity (about 40 M counts)
1:
HC
2:
DS
First Chamber: hollow cathode
� +��� → ��� + � + 2�
� +��� → �� + �� + 2�
� +��� → �� + �� + 2�
� +��� → ���� + 2�
Second Chamber: short source drift region
��� +��� → ���
� + ��
�� +��� → ���
� + �
�� +��� → ���
� + �
��� +�� → �� + �
9
PTR-QMS Operation
[ - VOC ]
Proton affinity < H2O
N2
O2
H2O.H+ + Ar � NO REACTION
CO2
CH4
Proton affinity > H2O
C3H6 � C3H6 H+
C6H6 � C3H6 H+
H2O.H+ + CH3OH � CH3OH H+
CH3CN � C3H6 H+
VOCs
The Reaction chamber (or drift tube):
Low fragmentation, No buffer gas needed
Pdrift=2.2 mbar, Udrift=600V
[ + VOC]
10
PTR-QMS Operation
H+ VOC
Quadrupole
• Vacuum chamber: reduces collisions
between ions and molecules
• Analyte ions are mass selected (m/z
RH+)
• Sequential detection depending on the
voltage applied on the parallel rods
• Mass resolution : 1 amu
• No distinction between
isomers/isobares
11
PTR-QMS Operation
ION DETECTOR: Secondary Electron Multiplier + ion counting system
• I(H3O+) and I(MH+) measured in counts per second (CPS):
proportional to the respective densities of these ions
H+ VOC
12
PTR-QMS Operation
13
PTR-QMS data process overview
Raw signal (cps) ���� Concentration (ppb)
• Normalization to the number of primary ions (decrease with time)
• m/z 19: H3O+ (about 40 M counts)� saturation of SEM
• m/z 21: H318O+ (about 2.104 counts), with (m/z 19)/(m/z21) = 500
• Normalization to water cluster formation in the drift tube (dependent on
Humidity)
• m/z 37: (H2O) H3O+
• Substraction of the instrumental background (measured using a scrubber)
• Calibration
[��]���= 10�� � ���
� ��(����)!"#$
%/'�(∗*++�%/',-* fi
14
PTR-MS Application
BVOC emission rates at the branch-scale
Concentration of BVOCs
Flux measurements (Disjunct Eddy covariance)
Total OH reactivity measurements
C.Kalogridis et al., 2014 ACPD
A-C.Genard et al., in prep
Zannoni et al., in prep
15
VOC Flux measurements by PTR-MS
The eddy covariance technique:
Same principle but enable the use of:
• Relatively slow response instruments in single-compound measurements
• Fast response instruments in multi-compound measurements (e.g) PTR-MS
First measurements by Karl et al. (Atmos. Chem. Phys., 2002)
The disjunct eddy covariance technique:
High frequency
analyzers!
16
PTR-MS and Disjunct Eddy covariance
Lower frequency for VOC measurements by PTR-MS:
• 100-500 ms/mass minimum
• Multi-compound sequential measurements:
a few seconds for one cycle
1000
800
600
400
200
0
PT
R-M
S r
m/z
69
raw
sig
na
l [cp
s]
706050403020100seconds
-1.4
-1.2
-1.0
-0.8
-0.6
-0.4
-0.2
0.0
vertica
l win
d sp
ee
d [m
/s]
Isoprene measurements (ci) High frequency vertical wind measurements (wi)
High frequency of Wind velocity measurements (10–20 Hz).
Resulting in a disjunct concentration time series!
17
18
Total OH reactivity measurements with
the Comparative Reactivity Method
(CRM)
Nora Zannoni
19
Contents
• Introduction
- The total OH reactivity
- The Comparative Reactivity Method (CRM)
- Experimental set up
• Exemples of
- Measured OH reactivity with CRM
- Measured vs. Calculated
-Missing Reactivity
• Outlook
20
OH role in the atmosphere
• OH sources: O3, HO2+O3, HO2+NO
• OH Sinks? (atmospheric composition? K
rate?)
Total OH reactivity
Total loss rate of OH radicals due to the
presence of reactive compounds in the
atmosphere
Calculated reactivity
Measured ReactivityMissing reactivity?
∙OHCH4
CO
NO2
?
21
Measuring the Total OH reactivity:
The Comparative Reactivity Method (CRM)(Sinha et al., 2008)
• Glass reactor + PTR-MS
• OH produced in situ
• Pyrrole (m/z 68) reference compound
• Competition between pyrrole and ambient reactive compounds
Pyrrole + zero air
Hg lamp N2 dry pump
To PTR-MS
14 cm
3 cm
20x103
18
16
14
12
10
8
6
pyrr
ole
conc
entr
atio
n (c
ps)
1:00 PM 2:00 PM 3:00 PM 4:00 PM 5:00 PM 6:00 PMTime
1)31(
)23(CKp
CC
CCRair ⋅⋅
−−=
C0 Lamp on
C1Wet N2 in
C2ambient air in
C3
Pyrrole + ambient air
N2 wet
22
Experimental set up
CRM scheme used in ChArMEx, 2013Bubbling N2
4way valve
N2 Pyrrole Propane Zero air
GCU
4-way
valve4way
valve
MFC MFC MFC MFC
3 way
valve
pump
pump
Glass
reactor
PTR-MS
MFC
Ambient air
23
Project name/
where
Type of
environment
Investigated OH
reactivity range (s-1)
LOD of
CRM (s-1)
Reference
GABRIEL
(Suriname)
Tropical forest 28-72 6 Sinha et al.,
2008
Mainz Urban 6±3-18±4 6 Sinha et al.,
2008
BFORM
(Hyttiala,
Finland)
Boreal forest 3.5-60 3.5 Sinha et al.,
2010
CABINEX (USA) Boreal forest Up to 1000 15 Kim et al., 2011
HUMPPA-COPEC
(Hyttiala,
Finland)
Boreal forest 3-76 3-4 Noelscher et al.,
2012
DOMINO (El
Arenosillo,
Spain)
Rural site 3.5-84 3.5 Sinha et al.,
2012
MEGAPOLI
(Paris, France)
Urban Up to 130 3.5 Dolgouroky et
al., 2012
Germany Boreal forest
(Norwey spruce)
4-15 3-4 Noelscher et al.,
2013
Previous studies with the CRM
24
First field deployment of our set upCARBOSOR 2013: Cape Corsica monitoring station (42.97°N, 9.38°E, alt 533 m)
6 km2.5 km
Courtesy of J.Sciare
24/06/13
Installation
and tests
01/07/13 08/07/13 13/07/13 16/07/13 05/08/13
Intercomparison with CRM MD
Plant experimentMeasurement campaign
Total measured OH reactivity [s-1] from 16/07/2013- 05/08/2013
20
15
10
5Tot
al O
H r
eact
ivity
(s-
1)
16/07/2013 21/07/2013 26/07/2013 31/07/2013 05/08/2013
hourly avg OH reactivity OH reactivity
• Measurements from 16/07/2013- to 5/08/2013 � 3 weeks of data
• A data point every 10 minutes
• 2 major gaps: humidity problem, atmospheric conditions
• avg value of 5.5 s-1, up to 20 s-1
• LOD of the system≈ 2.5 s-1
• Uncertainty of CRM ≈ 20% (k rate, flow fluctuations in MFCs, instrumental error, pyrrole
standard) 25
preliminary results
26
Compound K (cm3/mol*s) Compound K
(cm3/mol*s)
Compound K (cm3/mol*s)
isoprene 1.00E-10 ethane 2.41E-13 Hexane 5.20E-12
2-methyl-2-butene 8.72E-11 b-pinene 7.81E-11 2,2,3-trimethylbutane 3.81E-12
1,3-butadiene 6.66E-11 a-pinene 5.33E-11 Isooctane 3.34E-12
T2-butene 6.37E-11 styrene 5.30E-11 Benzene 1.28E-12
T2-pentene 5.71E-11 hexene 3.70E-11 NO2 7.51E-11
C2-pentene 5.71E-11 m-xylene 2.45E-11 NO 3.30E-11
C2-butene 5.60E-11 p-xylene 1.52E-11 HCHO 9.38E-12
isobutene 5.18E-11 tridecane 1.51E-11 CO 1.49E-13
3-methyl-1-butene 3.17E-11 o-xylene 1.47E-11 CH4 6.28E-15
1-butene 3.11E-11 dodecane 1.32E-11 Methanol 9.00E-13
1-pentene 2.74E-11 undecane 1.23E-11 Acetonitrile 2.20E-14
propene 2.60E-11 nonane 9.70E-12 acetaldehyde 1.50E-11
ethylene 8.51E-12 octane 8.11E-12 formic acid 4.50E-13
1-butyne 7.27E-12 ethylbenzene 7.51E-12 Acetone 1.80E-13
pentane 3.84E-12 cyclohexane 6.97E-12 acetic acid 8.00E-13
n-butane 2.36E-12 2-methylhexane 6.69E-12 MVK+ MACR 3.00E-11
2,2-dimethylbutane 2.23E-12 2,3,4-trimethylpentane 6.50E-12 MGLYOX 1.72E-11
isobutane 2.14E-12 2,3-dimethylpentane 6.46E-12 MEK 1.20E-12
propane 1.09E-12 toluene 6.16E-12 propionic acid 1.20E-12
2,2-dimethylpropane 8.40E-13 2,4-dimethylpentane 5.48E-12 EVK 3.60E-11
acetylene 7.79E-13 2-methylpentane 5.20E-12 Butiric acid 1.79E-12
Nopinone 1.43E-11
Pinonaldehyde 4.00E-11
GC-FID, MD
NOx analyser, LAMP
Hantzsch, LSCE
Picarro, LSCE PTR-TOF-MS, MD
Measured vs calculated OH reactivity (s-1) from 16/07/2013- 05/08/2013
16
14
12
10
8
6
4
2
Tota
l OH
reac
tivity
(s-1
)
16/07/2013 21/07/2013 26/07/2013 31/07/2013 05/08/2013
Calculated Measured
27
preliminary results
28
Missing OH reactivity in-depth: unknown
known
20
15
10
5Tot
al O
H r
eact
ivity
(s-
1)
16/07/2013 21/07/2013 26/07/2013 31/07/2013 05/08/2013
hourly avg OH reactivity OH reactivity
32%
68%
52% 48%
26%
74% 44%
56%
36%
64%
average all campaign
50% 50%
preliminary results
29
Outlook• We are not able to know precisely the atmospheric composition and the
kinetics of many reactions is still unknown (discrepancies between studies and
data missing)…
• …total OH reactivity measurements give information on the total loading of
reactants in the atmosphere
• Comparative Reactivity method employs a glass reactor and a PTR-MS: many
applications so far but still some technical optimization needed!
• We can calculate the OH reactivity of the measured gases and compare this
value with the measured one: we have the missing reactivity;
• Investigations on the missing reactivity helps to understand the chemical
processes
Thank you for your attention!
30
Thank you for your attention!
Acknowledgments:
MD: Sebastien Dusanter, Stephane Sauvage, Nadine Locoge, Thierry Leonardis, Vincent Michoud;
LSCE: Cerise Kalogridis, Cyril Vuillemin, Francois Dulac, Eric Hamonou;
LAMP: Aurelie Colomb, Jean Marc Pichon