<p> 3 RD GAW EXPERT WORKSHOP ON VOC s</p><p>Summary of the session “VOC observations in the atmosphere” Chair: S.Penkett Rapporteur: A. Lewis</p><p>Overview of the VOC observations in the GAW programme. 1. INSTAAR flask network for light NMHCs provides a global picture of trends and distribution for small range of NMHC species. Flask network provides GAW-VOC with a common reference point for comparison with network on-line instruments and other VOC measurements, for example from aircraft.</p><p>2. In situ / on-line instruments within the network remain limited in number, but some stations do exist and report data to GAW data centers (only 2 stations at the moment).</p><p>3. Retrospective analysis of non-GAW VOC data to give further background trends appears a very profitable way to expand the spatial range of the GAW-VOC network. Some examples can be found in different projects, e.g. samples from aircraft (CARIBIC, research aircraft), data from emissions monitoring sites, urban air pollution sites</p><p>4. Interoperability of data appears generally good: - Common seasonal cycles seen with many NMHCs irrespective of location / institute - Generally good agreement in absolute mixing ratios for similar locations and measurements made in GAW and also with older literature - Common trends in VOCs reported over last 1-2 decades in many locations. Rate of change is similar between locations and researchers.</p><p>There is already a consistent GAW message on some VOC trends and behaviour. Nevertheless, current network has several drawbacks: • Observations outside of the basic C2-C7 NMHCs are less common in general, and very limited in the GAW-VOC network. • Main gaps lie in biogenic NMHCs (other than isoprene), DMS, and oVOC (including HCHO) • No single factor is responsible for this: – Limited instrument capability (e.g. difficult to measure monoterpenes on a PLOT column, may require a MS when only a FID is available. – Limited sampling capability ( e.g. species not stable in canisters) – Limited availability of stable standards (particularly oVOCs) – Potentially limited ‘enthusiasm’ to expand measurement complexity (seems not to be a problem)?</p><p>It isn’t a necessity that all stations measure all possible GAW target VOCs, rather that in its totality the GAW-VOC network covers the appropriate range of species.</p><p>Biogenic VOCs: - For biogenic VOCs both GC and PTR-MS based methods have an important role to play. -Potential to obtain ecosystem scale fluxes using PTR is very attractive when coupled with GC-MS for speciation of individual isomers. - Marine biogenic NMHCs are very low in mixing ratio but may be important for SOA formation.</p><p>Implications are: - Support calibration approaches that support both measurement technologies</p><p>02befc1c856fbaeed8a5bb2ec651845e.doc, 1 July 10 - Conduct regular side by side comparisons - Biogenic emissions are unique to an individual landscape type and so there is no one-size-fits-all set of GAW compounds that can be measured. - GAW-VOC priority list of five monoterpenes remains valid however.</p><p>DMS - Limited DMS data available – some good historical records of intra-annual behaviour available, for example at Cape Grim and Mace Head, but no long time series of data within GAW? - Key science driver for DMS remains however through its possible its role in maritime aerosol / CCN formation. oVOCs - GC and PTR both offer measurement opportunities - Care needs to be taken in understanding how isobaric species behave within a PTR ionisation system – for example ethanol / formic acid interferences. - GC methods require detailed calibration and standard gas stability can be a limiting factor. Eg Cape Verde uses a standardised carbon response, with permeation oVOC sources just as an inlet and instrument check. </p><p>GAW-VOC observations – Challenges • Network of observations draws heavily on existing infrastructure used for background monitoring of other long lived gases e.g. flask network, ozone sites. • Network biased somewhat towards mid/high latitudes and Northern hemisphere. • Network biased towards data measurements and assessment of trends of primarily anthropogenic emitted VOCs, due to observing locations. • GAW requires an expansion in to the tropical terrestrial environment. • Need to provide better linkage between surface VOC (through GAW) with Earth observation derived estimates of BVOCs derived from other properties. • Key areas include South America, central Africa and SE Asia as key hot spots (as seen via HCHO). • Continued need to improve links with modeling and the promotion of VOCs as a sensitive probe of model performance in terms of oxidation chemistry, emissions and transport / dilution properties. • Measurements of HCHO remain very challenging using in situ methods • Measurement challenges need to be overcome however to provide some ground truthing for space measurements. • Need to consider the role within GAW-VOC for surface based column measurements (eg through DOAS). • Other oxygenated VOCs remain difficult to calibrate irrespective of measurement method. t is essential that any method developed by NMI’s can be used by scientists in the field. • oVOCs have currently uncertain annual cycles (min or max in summer?). • Not enough data to provide evidence of longer term trends – have they declined with the primary emissions such as benzene? What fraction are natural vs secondary from anthropogenic emissions. • Need to improve submission rates of VOC data to WMO-GAW World data centres. • Requirements now to understand with users the current barriers to submission: – Format is too difficult for users? – Just not enough time? – Data already on national databases? – Lack of training for station scientists to aid in submissions? • Can the data centre help support us?</p><p>02befc1c856fbaeed8a5bb2ec651845e.doc, 1 July 10 GAW-VOC observations – Opportunities • Opportunities for expansion – Potentially prioritize expanding the spatial extent of GAW-VOC over the introduction of new VOC species in to existing locations. – Identify stable and practical tropical forested locations where long-term VOC measurements may be established – Science options may include: • Monitor BVOCs in a location where the landscape is likely to be directly manipulated (eg natural to agricultural) to quantify ecosystem response for reactive fluxes • Monitor BVOCs in a ‘secure’ natural environment where the drivers are external to landscape management, for example through climate alternation via changing rainfall, CO2, temperature, nutrients etc. • Potential partners in SE Asia may provide a major opportunity - Use of Royal Society / GAW station Danum Valley in Malaysian Borneo - Nascent GAW programme proposed by Indonesia - Both are options where WMO may provide some leadership</p><p>Summary of the session “Central Facilities : World Calibration Center” Chair: Rainer Steinbrecher Rapporteur: Berhard Rappenglück </p><p>Quality and comparability of VOC-measurements in the GAW-VOC network - global coverage achieved only through NOAA GMD glass flasks - QA/QC at GAW stations is implemented via: -GAW Central Facilities (WCC-VOC, CCL) - station audits, round robin exercise - Transfer of scales (primary/secondary standards; transfer/traveling standards)</p><p>- GAW targets: -NMHC (Ethane, Ethine, Propane, i-/n-Butane, i-/n-Pentane, Isoprene, Benzene, Toluene) - monoterpenes (a-, b-pinene, cineol, D-3-carene) -oxyVOCs (HCHO, Methanol, Ethanol, Acetone) - DMS - acetonitrile - 2010: NMHC standards are in place! others still need to become available! </p><p>VOC Central Calibration Laboratory (CCL) taking care of individual compounds (promising approaches!): + NMHC (NPL) + Monoterpenes (NIST) + oxyVOCs (VSL) + DMS, Acetonitrile (KRISS)</p><p>- Round Robin exercises and audits performed by WCC-VOC: + past experience (2003): Approx. only 50% of the labs perform reasonably well, so there was a need to harmonize stds + Current status (2010): Audits (in –situ): Jungfraujoch, Hohenpeissenberg, Cape Verde (global) Rigi, Egbert (regional)</p><p>02befc1c856fbaeed8a5bb2ec651845e.doc, 1 July 10 Audits (cans): - Institute of Alpine and Arctic Research (INSTAAR) - Environmental Science and Technology Centre, Environment Canada - MPI (CARIBIC) - U York, Dpt of Chemistry, FAAM Research Aircraft BAe146 Still room to improve, but overall better results than in 2003!</p><p>- Future plans: + finalize setup of CCL for VOC + Audit of Pallas & Cape Grim + Intra-lab AQ/QC procedures for NMHC and monoterpene analysis of the WCC- VOC + setup and test for oxy-VOCs + proceed to phase two of QA/QC measures within GAW-VOC (monoterpenes)</p><p>Opportunities Collaboration with ACTRIS (Aerosol, Clouds, and Trace Gases Research Infrastructure) + NOxy/VOC part + VOC part coordinated by EMPA (Reimann) + similar approaches like GAW (development of protocols/procedures), including: - elaboration of SOPs - round-robin, on-site intercomparison, station audits (incl. error assessment, data processing, QC criteria for data delivery) - test best measurement practice in QA experiments: (real air reference gas; in-situ intercomparison measurements campaigns (NMHC- Jungfraujoch[EMPA], OVOC at Finokalia [FORTH]) - link ground based in-situ with vertical profile information + focused on European partners + some issues not included (HCHO, DMS)</p><p>Challenges/Needs General: - availability of standards (MT, OVOCS, DMS, ACT) - ACTRIS: EU project; how will GAW be integrated (discussion on SOPs etc)? new techniques: - PTR-MS: promising, but also limitations - Cavity Ring Down: emerging, but expensive - Lewis: glass micro-fabricated system (GCxGC on chip)</p><p>Calibration procedures/SOPs: - elaborate SOPs audits/comparison campaigns: - formalization of ways to perform audits and comparisons ask previous participants (questionnaire) about suitability - cans should be sent out on a more frequent basis (e.g. 1/year) in between audits (ambient air?)</p><p>Summary of actions agreed during the session on “Central Facilities: Central Calibration Laboratory” Chair: M. Milton, </p><p>02befc1c856fbaeed8a5bb2ec651845e.doc, 1 July 10 Rapporteur: Joële Viallon</p><p>Reported - June 2010 Actions agreed Date NMHC (ppb level) MoU in place Traceability available to WCC and field stations NMHC (sub-ppb NIST/NPL/VSL comparison Continue with collaboration level) completed</p><p>Monoterpenes Stable standards of selected MTs NPL-NIST comparison of 4 MT at ppb levels from NPL and NIST mixture + comparison with VSL Validation of absorption tube dynamic facility performance for selected components at VSL. 2010/11</p><p>Formaldehyde VSL certification of commercial BIPM to lead key comparison (Scott) standard at 5 ppm. Primary facility planned at BIPM 2011/2012</p><p>DMS Stable standard prepared and KRISS to compare 10 ppm validated by KRISS at 10 ppm standard with VSL dynamic standard 2010/11 Acetonitrile Stable standard prepared and KRISS to continue with validation underway by KRISS at validation 10 ppm oxy-VOC Stability trials at 1 to 10 ppm NPL-VSL-NIST to carry out underway at NPL, VSL. comparison 2010/11</p><p>Dilution methods To be discussed at future GAWG 2011</p><p>Absorption tubes Survey of stations to determine Summer requirements. 2010</p><p>02befc1c856fbaeed8a5bb2ec651845e.doc, 1 July 10</p>