– Own expertise • online/offline VOC techniques in urban and rural areas; surface and airborne platforms • Head of WCC-VOC 2001-2004 – Current state • 1 st GAW VOC intercomparison (2003) – Recommendations on future steps • based on 1 st GAW VOC intercomparison (2003) Contribution to Contribution to WMO/GAW Expert Workshop on VOCs WMO/GAW Expert Workshop on VOCs Geneva, Jan 30 – Feb 1, 2006 Geneva, Jan 30 – Feb 1, 2006 Bernhard Rappengl Bernhard Rappenglü ck ck University of Houston University of Houston
Contribution to WMO/GAW Expert Workshop on VOCs Geneva, Jan 30 – Feb 1, 2006 Bernhard Rappengl ü ck 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 - PowerPoint PPT Presentation
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
– 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)
Contribution to Contribution to WMO/GAW Expert Workshop on VOCsWMO/GAW Expert Workshop on VOCs
Geneva, Jan 30 – Feb 1, 2006Geneva, Jan 30 – Feb 1, 2006 Bernhard Rappengl Bernhard Rappenglüück ck
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).
– 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.
VOC-Standard
0
2
4
6
8
10
12
Eth
yle
ne
Eth
an
e
Pro
pa
ne
i-b
ute
ne
n-b
uta
ne
c-2
-bu
ten
e
i-p
en
tan
e
2-m
e-1
-bu
ten
e
iso
pre
ne
c-2
-pe
nte
ne
2,2
dim
eb
uta
ne
3-m
e-1
-pe
nte
ne
cycl
op
en
tan
e
2-m
e p
en
tan
e
2-m
e-1
-pe
nte
ne
c-3
-he
xen
e
c-2
-he
xen
e
2,4
dim
e-p
en
tan
e
cycl
oh
exa
ne
2,3
dim
e-p
en
tan
e
2,2
,4 t
rim
e-p
en
tan
e
2,3
dim
eth
yl -
2-
pe
nte
ne
2,3
,4 t
rim
e-p
en
tan
e
2-m
e-h
ep
tan
e
3-m
e-h
ep
tan
e
et-
be
nze
ne
p-x
yle
ne
o-x
yle
ne
i-p
rop
-be
nze
ne
1,2
,3 t
rim
eth
yl b
en
zen
e
3-e
t-to
lue
ne
1,3
,5 t
rim
e-b
en
zen
e
1,2
,4 t
rim
e-b
en
zen
e
de
can
e
1,3
die
thb
en
z
n-b
ut-
be
nze
ne
un
de
can
e
[pp
bv
]
73 compounds Accuracy[%]
Precision[%]
Alkane 10 5Alkene 20 20Alkine 10 5Aromaten 15 10
AlkanesAlkenesAlkinesAromatics
mixing ratios < 0.1 ppb: 50% 50%
DQOs
– Standard• 1 STD canister (73 VOCs), prepared and certified by NCAR
VOC-Standard
0
2
4
6
8
10
12E
thyl
en
e
Ace
tyle
ne
Eth
an
e
Pro
pyl
en
e
Pro
pa
ne
i-b
uta
ne
n-b
uta
ne
i-p
en
tan
e
n-p
en
tan
e
iso
pre
ne
n-h
exa
ne
be
nze
ne
n-h
ep
tan
e
tolu
en
e
n-o
cta
ne
o-x
yle
ne
n-n
on
an
e
a-p
ine
ne
1,2
,4 t
rim
e-b
en
zen
e
de
can
e
un
de
can
e
[pp
bv
]
NIST-traceability: 21 compounds
Accuracy[%]
Precision[%]
Alkane 10 5Alkene 20 20Alkine 10 5Aromaten 15 10
AlkanesAlkenesAlkinesAromatics
Accuracy[%]
Precision[%]
Alkane 10 5Alkene 20 20Alkine 10 5Aromaten 15 10
AlkanesAlkenesAlkinesAromatics
mixing ratios < 0.1 ppb: 50% 50%
DQOs
– Standard• 1 STD canister (73 VOCs), prepared and certified by NCAR
green: NIST-traceable VOC ParticipantsVOC A B C D E F G H I J
– Repeatability [%] for a subset of 28 GAW target compounds. (Results that did not meet the DQOs are shown in red).
– Deviation [%] from the WCC-VOC reference values for each VOC. (Results that did not meet the DQOs are shown in red).green: NIST-traceable VOC ParticipantsVOC A B C D E F G H I J
– 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
• 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
in green: NIST traceable 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.
• 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 by any lab
– 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 1The 1stst GAW VOC Intercomparison 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 1The 1stst GAW VOC Intercomparison 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 1The 1stst GAW VOC Intercomparison 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 1The 1stst GAW VOC Intercomparison 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 GAW-wide calibration gas (e.g. NPL or butane/benzene mixture)» exchange of canisters for concurrent sampling and subsequent reciprocal analysis