Own expertise

1. Contribution to WMO/GAW Expert Workshop on VOCsGeneva, 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)

2. presumably biogenic VOC Examples: online VOC Studies • Anthropogenic vs biogenic VOC N/NE FLOW PAUR-I campaign 1996 Athens Rappenglück et al. (1999)

3. Examples: online VOC Studies • Photochemistry & Emissions Photochemistry reflected in VOC ratios (same source) Emissions reflected in VOC ratios (different sources) Chile - I 1996 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).

4. 1 : 1 1,5 : 1 transport of urban plume downwind 2 : 1 1 : 1 Examples: online VOC Studies toluene/ benzene • Transport & photochemistry BERLIOZ 1998 Winkler J. et , al (2002) upwind

5. 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!!!

6. 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.

7. Standard • 1 STD canister (73 VOCs), prepared and certified by NCAR DQOs

8. Standard • 1 STD canister (73 VOCs), prepared and certified by NCAR DQOs

9. Repeatability [%] for a subset of 28 GAW target compounds. (Results that did not meet the DQOs are shown in red).

10. Deviation [%] from the WCC-VOC reference values for each VOC. (Results that did not meet the DQOs are shown in red).

11. 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 • 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

12. 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

13. 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 [%]

14. 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)

15. 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

16. 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

17. 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 GAW-wide calibration gas (e.g. NPL or butane/benzene mixture) • exchange of canisters for concurrent sampling and subsequent reciprocal analysis