Transcript Contribution to WMO/GAW Expert Workshop on VOCs Geneva, Jan 30 – Feb 1, 2006 Bernhard Rappenglück University of Houston – Own expertise • online/offline VOC techniques.

Contribution to
WMO/GAW Expert Workshop on VOCs
Geneva, Jan 30 – Feb 1, 2006
Bernhard Rappenglück
University of Houston
– Own expertise
• online/offline VOC techniques in urban and rural areas; surface and airborne platforms
• Head of WCC-VOC 2001-2004
– Current state
• 1st GAW VOC intercomparison (2003)
– Recommendations on future steps
• based on 1st GAW VOC intercomparison (2003)
NMHC
Examples: online VOC Studies
N/NE FLOW
• Anthropogenic vs
biogenic VOC
PAUR-I campaign
1996
1400
Athens
40
1200
I
35
TI
tol.
isopr.*
1-hex.
und.
I
T
TItol.
tol.1-hex.
1-hex.
und.lim.
lim. lim.
IT
tol.lim.
ITtol.
T
30
I [W/m**2]
1000
25
800
20
600
15
400
10
200
0
06.06.
T [°C], NMHC [ppbv]
[ppbv]
presumably
biogenic VOC
5
07.06.
08.06.
09.06.
1996
10.06.
0
11.06.
Rappenglück et al. (1999)
isoprene&t-2-pentene&c-2-pentene
benzene
toluene
i-pentane
m-xylene
cyclopentane&2,3-dimethylbutane&2methylpentane
o-xylene
trans-2-hexene&2-methyl-2-pentene
n-hexane&2-methyl-1-pentene
n-pentane&2-methyl-1-butene
1-pentene
3-methylhexane
cis-2-hexene
n-butane&1-butene
2-methylheptane
1-hexene
p-xylene
ethylbenzene
1,2,4-tri-methyl-benzene
nonane
trans-3-methyl-2-pentene
3-methylheptane
limonene
n-heptane
2,5-dimethylhexane
m-ethyltoluene
cyclohexane
methylcyclopentane
n-decane
undecane
2-methylhexane
3-methylpentane
sec-butylbenzene
o-ethyltoluene
cumene
mesitylene
2,3-dimethylpentane
n-octane
methylcyclohexane
p-ethyltoluene
n-propylbenzene&dodecane
styrene
2,4-dimethylhexane
p-cymene
nonene
i-butylbenzene
1-octene
ethylcyclohexane
2,3,4-trimethylheptane
Examples: online VOC Studies
• Photochemistry & Emissions
Photochemistry reflected in VOC ratios
(same source)
Emissions reflected in VOC ratios
(different sources)
1,00
benzene/n-butane&1-butene&t-2-butene
1.00
ethylbenzene/m-xylene
0,80
0,60
0,40
0,20
0,00
00:00
06:00
12:00
18:00
0.80
0.60
0.40
0.20
0.00
00:00
time of day
median POH
median LAC
Chile - I
1996
06:00
12:00
18:00
time of day
median POH
median LAC
Median ethylbenzene/m-xylene ratios (left) and median benzene/n-butane&1-butene&t-2-butene ratios (right)
observed at Parque O´Higgins (POH) and Las Condes (LAC) in Santiago de Chile (Rappenglück et al. 2000).
Examples: online VOC Studies
• Transport &
photochemistry
toluene/
benzene
1:1
BERLIOZ
1998
Winkler J. et , al (2002)
1,5 : 1
transport of
urban plume
downwind
2:1
upwind
1:1
The 1st GAW VOC Intercomparison (2003)
– Participants
• 9 different stations/laboratories (10 instruments)
• 7 countries (Brazil, Canada [2 labs], Czech Republic, Finland, Germany [2 labs; 3
instruments], Ireland, and Slovakia)
• GC/FID (MS) - methods
– Sampling types
• Offline (6 labs)
• Online (3 labs; 4 instruments)
– Number of VOCs determined
• Offline: 25-150
• Online: 15-66
– equipment, sampling, analyis, calibration
• Unique sampling and analysis methods!!!
The 1st GAW VOC Intercomparison (2003)
– Implementation
• Objective:
– Examination of the performance of the analytical facilities of each laboratory and to check
whether the results meet the Data Quality Objectives (DQO) developed by WCC-VOC.
• Taks for participants:
– Identification and quantification of as many compounds of the WCC-VOC standard canister as
possible based on their routine identification and calibration methods.
0
Precision
[%]
10
20
10
15
5
20
5
10
undecane
Accuracy
[%]
n-but-benzene
1,3 diethbenz
mixing ratios < 0.1 ppb:
50%
decane
1,2,4 trime-benzene
1,3,5 trime-benzene
3-et-toluene
Alkanes
Alkane
Alkenes
Alkene
Alkine
Alkines
Aromaten
Aromatics
1,2,3 trimethyl benzene
12
i-prop-benzene
10
o-xylene
73 compounds
p-xylene
et-benzene
3-me-heptane
2-me-heptane
6
2,3,4 trime-pentane
8
2,3 dimethyl - 2- pentene
2,2,4 trime-pentane
2,3 dime-pentane
cyclohexane
2,4 dime-pentane
c-2-hexene
c-3-hexene
2-me-1-pentene
2-me pentane
cyclopentane
3-me-1-pentene
2,2 dimebutane
c-2-pentene
isoprene
2-me-1-butene
i-pentane
c-2-butene
n-butane
i-butene
Propane
Ethane
Ethylene
[ppbv]
– Standard
• 1 STD canister (73 VOCs), prepared
and certified by NCAR
VOC-Standard
DQOs
50%
4
2
– Standard
VOC-Standard
• 1 STD canister (73 VOCs), prepared
and certified by NCAR
DQOs
12
NIST-traceability: 21 compounds
Accuracy Precision
[%]
[%]
Accuracy
Precision
10
8
6
[%]
5
20 5
5 20
10 5
Aromaten
15ppb:
mixing
ratios < 0.1
Aromatics
50%
10
50%
4
undecane
decane
1,2,4 trime-benzene
a-pinene
n-nonane
o-xylene
n-octane
toluene
n-heptane
benzene
n-hexane
isoprene
n-pentane
i-pentane
n-butane
i-butane
Propane
Propylene
Ethane
0
Acetylene
2
Ethylene
[ppbv]
[%]
10
2010
1020
1510
Alkanes
Alkane
Alkenes
Alkene
Alkanes
Alkane
Alkine
Alkines
Alkenes
Alkene
Aromaten
Aromatics
Alkine
Alkines
– Repeatability [%] for a subset of 28 GAW target compounds.
(Results that did not meet the DQOs are shown in red).
Participants
green: NIST-traceable VOC
VOC
A
B
C
D
E
F
G
H
I
J
ethane
4.6
1.0
1.2
0.2
0.3
2.8
0.3
ethylene
4.5
2.7
0.6
0.8
2.5
2.5
0.4
acetylene
4.7
0.3
2.6
0.6
propane
3.8
0.2
2.1
0.5
3.9
2.2
0.9
3.0
0.2
propylene
3.9
0.7
2.2
0.3
6.4
2.0
23.4
3.1
1.4
i-butane
4.0
0.6
3.8
0.8
4.6
2.4
0.3
2.3
0.6
n-butane
5.3
0.3
1.9
0.1
7.1
2.5
0.3
2.0
0.6
1-butene
5.2
36.9
2.4
0.2
t-2-butene
4.7
2.7
2.6
0.6
i-butene
2.1
5.8
c-2-butene
1.8
1.4
i-pentane
2.1
0.6
n-pentane
2.4
0.2
isoprene
12.7
4.4
1.6
2.0
3.0
2.6
4.0
2.8
2.6
4.7
2.4
5.2
3.2
1.8
1.2
2.8
1.1
1.3
0.8
7.6
1.9
21.5
2.4
0.5
t-2-pentene
12.6
3.7
2.7
0.5
11.7
2.2
8.2
3.1
45.4
c-2-pentene
2.9
1.3
2.8
0.3
2.6
0.7
3.7
4.0
8.3
3.3
2.7
3.0
8.1
2.7
1.2
4.6
5.2
3.2
2.3
3.8
1.6
2-me pentane
2.9
3-me-pentane
4.4
0.3
4.4
0.3
2.9
1.8
n-hexane
9.8
3.3
4.3
0.3
benzene
1.4
1.1
1.9
0.9
cyclohexane
3.4
n-heptane
3.8
5.1
1.2
4.1
2.9
toluene
4.7
7.7
3.9
7.6
2.9
3.6
3.8
5.6
5.6
3.0
1.1
3.1
4.6
3.3
5.5
5.1
3.2
2.2
3.7
3.7
6.8
3.1
7.4
3.4
7.0
et-benzene
m,p-xylene
o-xylene
6.6
3.0
1.8
3.6
2.6
3.3
1.0
0.9
3.1
3.0
1,3,5 trime-benzene
4.6
4.9
10.8
1,2,4 trime-benzene
2.5
5.3
14.5
– Deviation [%] from the WCC-VOC reference values for each VOC.
(Results that did not meet the DQOs are shown in red).
Participants
green: NIST-traceable VOC
VOC
A
B
C
D
E
F
G
H
I
J
ethane
3.8
-64.2
-3.4
-1.2
-2.1
-4.4
-1.1
ethylene
5.2
-73.5
5.2
7.3
-16.5
-7.5
-2.3
-13.8
-54.7
-22.4
-25.1
propane
9.6
1.0
-0.1
2.1
-27.6
propylene
8.0
-1.9
5.4
11.5
i-butane
9.4
81.5
8.4
11.0
n-butane
6.7
78.8
-0.2
5.7
1-butene
4.2
137.3
6.4
11.2
t-2-butene
3.4
47.0
7.5
9.2
i-butene
6.9
2.7
10.3
acetylene
c-2-butene
4.0
-2.4
1.8
4.3
i-pentane
-14.3
-2.3
5.2
n-pentane
-26.3
-1.5
3.7
isoprene
-3.0
-2.7
-9.1
-1.0
-66.0
2.3
-15.7
-2.3
1.1
-33.7
-10.1
1.8
-4.3
2.5
-30.6
-9.0
-2.6
-3.5
-0.7
8.1
3.2
-18.1
-2.8
-7.6
-42.9
-3.8
-12.7
-7.4
-12.1
3.2
-2.5
-0.2
-0.6
-16.7
-2.5
5.2
1.4
-1.2
5.5
-98.0
-6.2
-17.0
t-2-pentene
-52.2
-22.9
92.3
6.6
-6.8
-4.0
-29.3
-11.6
23.8
c-2-pentene
-20.8
19.8
3.6
-0.6
-6.4
-1.7
-12.2
-5.4
1.0
2-me pentane
5.9
3-me-pentane
0.7
13.3
n-hexane
benzene
cyclohexane
n-heptane
toluene
-27.3
236.6
-3.0
4.3
6.3
208.2
-5.5
2.9
-78.8
-5.8
2.3
12.7
-40.8
51.4
1.2
-7.9
-4.6
-11.5
0.2
-30.7
-12.8
0.5
-0.4
-14.7
-5.2
2.3
-0.6
-22.7
5.1
-79.8
-6.5
4.3
-45.0
6.7
3.5
-1.4
-0.5
-5.1
10.1
-22.2
16.6
-6.5
et-benzene
1.1
-3.0
75.5
1.1
-21.1
3.0
5.3
m,p-xylene
4.1
-2.4
34.0
-14.3
-16.3
7.4
0.4
228.2
-22.9
-28.5
o-xylene
27.2
-17.2
1529.6
5.1
10.1
1,3,5 trime-benzene
-29.0
-90.8
-16.6
1,2,4 trime-benzene
30.0
-82.4
0.8
– Ranking of properly identified and quantified VOCs
(subset of 28 GAW target compounds)
X: related to all participants; Y: related to all participants who identified this specific VOC
in green: NIST traceable VOCs
VOC
X [%]
Y [%]
VOC
X [%]
Y [%]
VOC
X [%]
Y [%]
propane
80.0
88.9
i-butane
60.0
60.0
t-2-pentene
40.0
44.4
c-2-pentene
80.0
88.9
n-butane
60.0
66.7
n-hexane
40.0
40.0
isoprene
80.0
80.0
i-butene
50.0
100.0
2-me pentane
20.0
66.7
c-2-butene
70.0
100.0
et-benzene
50.0
71.4
o-xylene
10.0
20.0
benzene
70.0
87.5
m,p-xylene
50.0
71.4
acetylene
0.0
0.0
propylene
70.0
77.8
n-pentane
40.0
80.0
cyclohexane
0.0
0.0
ethylene
60.0
85.7
3-me-pentane
40.0
80.0
1,3,5 trime-benzene
0.0
0.0
t-2-butene
60.0
85.7
1-butene
40.0
80.0
1,2,4 trime-benzene
0.0
0.0
ethane
60.0
85.7
i-pentane
40.0
57.1
n-heptane
60.0
75.0
toluene
40.0
50.0
•
some NIST-traceable VOCs unambiguosly identified and properly quantified (e.g.
propane, isoprene, benzene, propylene)
•
difficulties in the proper determination of important VOCs, e.g. aromatic compounds
(apart from benzene), i-pentane, acetylene, and in general for low volatile VOCs
– Ranking of properly identified and quantified VOCs (all compounds)
X: related to all participants; Y: related to all participants who identified this specific VOC.
VOC
X [%]
Y [%]
VOC
X [%]
Y [%]
VOC
X [%]
Y [%]
propane
80.0
88.9
12
30.0
100.0
16
10.0
50.0
isoprene
80.0
80.0
3-me-1-butene
20.0
50.0
acetylene
0.0
0.0
c-2-pentene
80.0
88.9
2-me pentane
20.0
25.0
2,3 dime-butane
0.0
0.0
benzene
80.0
88.9
2-me-1-pentene
20.0
100.0
cyclopentane
0.0
0.0
ethylene
70.0
87.5
c-2-hexene
20.0
50.0
t-2-hexene
0.0
0.0
propylene
70.0
77.8
2,4 dime-pentane
20.0
66.7
cyclohexane
0.0
0.0
c-2-butene
70.0
87.5
3-me-heptane
20.0
66.7
2,3 dime-2-pentene
0.0
0.0
ethane
60.0
75.0
10
20.0
66.7
4-me-heptane
0.0
0.0
i-butane
60.0
60.0
2-me-2-butene
10.0
25.0
n-octane
0.0
0.0
t-2-butene
60.0
85.7
2,2 dime-butane
10.0
25.0
styrene
0.0
0.0
n-heptane
60.0
66.7
cyclopentene
10.0
50.0
n-nonane
0.0
0.0
n-butane
50.0
50.0
3-me-1-pentene
10.0
100.0
i-prop-benzene
0.0
0.0
i-butene
50.0
83.3
4-me-1-pentene
10.0
33.3
n-prop-benzene
0.0
0.0
n-pentane
50.0
62.5
c-3-hexene
10.0
100.0
1,3,5 trime-benzene
0.0
0.0
3-me-pentane
50.0
55.6
me-cyclopentane
10.0
33.3
2-et-toluene
0.0
0.0
1
50.0
83.3
2-me-hexane
10.0
50.0
1,2,4 trime-benzene
0.0
0.0
2
50.0
83.3
2,3 dime-pentane
10.0
50.0
decane
0.0
0.0
3
50.0
83.3
3-me-hexane
10.0
33.3
t-butyl benz
0.0
0.0
1-butene
40.0
80.0
2,2,4 trime-pentane
10.0
50.0
1,3 diet-benz
0.0
0.0
i-pentane
40.0
44.4
me-cyclohexane
10.0
33.3
n-but-benzene
0.0
0.0
t-2-pentene
40.0
44.4
2,3,4 trime-pentane
10.0
33.3
1,4 diet-benzene
0.0
0.0
n-hexane
40.0
40.0
2-me-heptane
10.0
33.3
1,2 diet-benzene
0.0
0.0
toluene
40.0
44.4
o-xylene
10.0
16.7
sec-butyl benzene
0.0
0.0
et-benzene
40.0
57.1
a-pinene
10.0
100.0
1,2,3 trime-benzene
0.0
0.0
m,p-xylene
40.0
57.1
3-et-toluene
10.0
50.0
undecane
0.0
0.0
1-pentene
30.0
60.0
4-et-toluene
10.0
50.0
11
0.0
0.0
2-me-1-butene
30.0
75.0
7
10.0
25.0
14
0.0
0.0
4
30.0
60.0
8
10.0
50.0
15
0.0
0.0
5
30.0
100.0
9
10.0
25.0
17
0.0
0.0
6
30.0
75.0
13
10.0
33.3
18
0.0
0.0
•
18 out of 90 compounds
accurately determined by
at least 50% of the
participants
• About 50 compounds
were accurately
determined by only 10%
of the labs
• nearly 30 compounds
could not be determined
Italic: NIST
VOCs
by traceable
any lab
1: 1-butene + i-butene
2: t-2-butene + 1-butene
3: 1-butene + 2-me-propene
4: 1-pentene + 2-me-2-butene
5: n-pentane + cyclopentane
6: n-pentane + 2-me-1-butene
7: me-cyclopentane + 2,2-dime-butane
8: 4-me + 3-me-pentene
9: 2,3-dime-butane + me-cyclopentane
10: 2-me-pentane + cyclopentane
11: 2,2- + 2,4-dime-pentane
12: benzene + 2,3-dime-pentane
13: 3-me-hexane + 2-me-hexane
14: me-cyclohexane + 2,2,3-trime-butane
15: o-xylene + styrene
16: 1-et-2-me-benzene + n-decane + i-butyl-cyclohexane
17: 1,2,4-trime-benzene + n-decane
18: n-but-benzene + 1,4-diet-benzene
– Ranking of the participating laboratories based on the resolved and
coeluting or combined VOC of the GAW standard (in total 90
compounds incl. coelutions). Ranking was based on the “total score”
being the sum of the columns X and Y.
X: Number of VOCs within DQO related to the total number of VOCs [%].
Y: Number of VOCs within DQO related to the number of VOCs identified by participant [%]
Participant
Number of VOCs
within DQO
X [%]
Y [%]
Total Score
D
24
26.7
88.9
115.6
C
25
27.8
83.3
111.1
G
14
15.6
87.5
103.1
J
35
38.9
60.3
99.2
H
19
21.1
63.3
84.4
F
34
37.8
46.6
84.4
A
15
16.7
57.7
74.4
I
24
26.7
43.6
70.3
B
4
4.4
9.3
13.7
E
2
2.2
10.0
12.2
The 1st GAW VOC Intercomparison
– Lessons learned
• Excellent:
– intercomparison of offline and online methods
– excellent feedback
– participants highly motivated
– very different laboratories integrated (e.g. programmes, experience,
infrastructure)
– some NIST-traceable VOCs unambiguosly identified and properly quantified (e.g.
propane, benzene, isoprene, propylene)
The 1st GAW VOC Intercomparison
– Lessons learned
• Difficulties:
– Logistics: varying delays due to customs!
– Data evaluation:
» wide range of number of determined VOCs (16-150!)
» varying return schedules for canisters and data
» proper consideration of coelution problems (typical for online applications)
troublesome
– Analytics :
» difficulties in the proper determination of important VOCs, e.g. aromatic
compounds (apart from benzene), i-pentane, acetylene, and in general for
low volatile VOCs
» significant variations of carbon response factor found for NCAR standard
> need for a suite of standards (e.g. NPL)
» heterogeneous results found in ambient air samplings (sometimes large
deviations) – not shown here
The 1st GAW VOC Intercomparison
– Lessons learned
• Current status:
– Due to the variety of sampling and analytical methods among the participants
both the number of identified species (16-150 VOCs) and their proper
quantification differed largely (mostly due to coelution problems).
– No clear quality difference among offline or online techniques, but lab
performance seems to be more important
The 1st GAW VOC Intercomparison
– Lessons learned
• Recommendations:
– Logistics: support requested from WMO for avoiding customs delays!
– Data evaluation:
» guideline for proper handling and evaluation of coelution problems.
» future guidelines for a “good” measurement:
(1) proper identification of as many as possible VOCs (incl. minor
compounds) or
(2) focus on the proper quantification of at least a few VOCs (standard
compounds)
– Future strategy:
» frequent intercomparisons with less VOC (5-10) on a more rigorous time
schedule basis
» stepwise raising number of VOCs to the full NPL-suite.
» apart from shipping unknown standards also shipping of a uniform GAWwide calibration gas (e.g. NPL or butane/benzene mixture)
» exchange of canisters for concurrent sampling and subsequent reciprocal
analysis