– 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

University of HoustonUniversity of Houston

Examples: online VOC StudiesExamples: online VOC Studies

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PAUR-I campaign1996

Athens

Rappenglück et al. (1999)

NMHC

isoprene&t-2-pentene&c-2-pentene benzene toluene

i-pentane m-xylene

cyclopentane&2,3-dimethylbutane&2-methylpentane

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

presumably biogenic VOC

N/NE FLOW

• Anthropogenic vs biogenic VOC

Examples: online VOC StudiesExamples: online VOC Studies

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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).

• Photochemistry & Emissions

Photochemistry reflected in VOC ratios

(same source)

Emissions reflected in VOC ratios

(different sources)

Chile - I1996

Winkler J. et , al (2002)

transport ofurban plume

toluene/benzene

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Examples: online VOC StudiesExamples: online VOC Studies

• Transport & photochemistry

BERLIOZ1998

The 1The 1stst GAW VOC Intercomparison (2003) 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 1The 1stst GAW VOC Intercomparison (2003) 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.

VOC-Standard

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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

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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

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 12.7 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 4.4

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 1.6

t-2-butene 4.7 2.7 2.6 0.6 2.0 3.0 1.8

i-butene 2.1 5.8 2.9 2.8

c-2-butene 1.8 1.4 2.6 2.6 4.7 5.2

i-pentane 2.1 0.6 4.0 0.3 2.4 3.2

n-pentane 2.4 0.2 1.8 1.2

isoprene 1.9 21.5 2.4 0.5 4.4 2.8 1.1 1.3 0.8 7.6

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

2-me pentane 2.9 3.3 2.7

3-me-pentane 4.4 0.3 3.0 8.1 3.0

n-hexane 9.8 3.3 4.3 0.3 6.6 2.7 1.2 4.6 5.2 2.6

benzene 1.4 1.1 1.9 0.9 3.2 2.3 3.8 1.6

cyclohexane 3.4 3.4 3.3

n-heptane 3.8 5.1 1.2 4.1 2.9 1.0 0.9 3.1

toluene 4.7 7.0 7.7 3.9 7.6 2.9 3.6 3.0

et-benzene 3.8 5.6 5.6 3.0 1.1 3.1 4.6

m,p-xylene 3.3 5.5 5.1 3.2 2.2 3.7 3.7

o-xylene 1.8 3.6 6.8 3.1 7.4

1,3,5 trime-benzene 4.6 4.9 10.8

1,2,4 trime-benzene 2.5 5.3 14.5

– 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

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

acetylene -13.8 -54.7 4.0 -22.4 -25.1

propane 9.6 1.0 -0.1 2.1 -27.6 -3.0 -2.7 -9.1 -1.0

propylene 8.0 -1.9 5.4 11.5 -66.0 2.3 -15.7 -2.3 1.1

i-butane 9.4 81.5 8.4 11.0 -33.7 -10.1 1.8 -4.3 2.5 8.1

n-butane 6.7 78.8 -0.2 5.7 -30.6 -9.0 -2.6 -3.5 -0.7

1-butene 4.2 137.3 6.4 11.2 3.2

t-2-butene 3.4 47.0 7.5 9.2 -18.1 -2.8 12.7

i-butene 6.9 2.7 10.3 2.3 -3.8

c-2-butene -2.4 1.8 4.3 -7.6 -12.7 -7.4 3.2

i-pentane -14.3 -2.3 5.2 -42.9 -5.8 -12.1 -2.5

n-pentane -26.3 -1.5 3.7 -0.2 -0.6

isoprene 5.5 -98.0 -6.2 -17.0 -78.8 -16.7 -2.5 5.2 1.4 -1.2

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 -17.2 1.2

3-me-pentane 0.7 13.3 -7.9 -4.6 2.3

n-hexane -27.3 236.6 -3.0 4.3 -40.8 -11.5 0.2 -30.7 -12.8 -0.6

benzene 6.3 208.2 -5.5 2.9 0.5 -0.4 -14.7 -5.2

cyclohexane 51.4 -22.7

n-heptane 5.1 -6.5 4.3 -45.0 6.7 3.5 -1.4 -0.5

toluene 27.2 -79.8 -5.1 10.1 -22.2 16.6 -6.5 10.1

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

o-xylene 1529.6 5.1 228.2 -22.9 -28.5

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

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

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.

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

Italic: NIST traceable VOCs 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

• 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