CCQM GAWG Meeting in Sydney, Oct. 2007

3 RD GAW EXPERT WORKSHOP ON VOC s

Summary of the session “VOC observations in the atmosphere” Chair: S.Penkett Rapporteur: A. Lewis

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.

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).

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

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.

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)?

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.

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.

Implications are: - Support calibration approaches that support both measurement technologies

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.

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.

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?

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

Summary of the session “Central Facilities : World Calibration Center” Chair: Rainer Steinbrecher Rapporteur: Berhard Rappenglück

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)

- 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!

VOC Central Calibration Laboratory (CCL) taking care of individual compounds (promising approaches!): + NMHC (NPL) + Monoterpenes (NIST) + oxyVOCs (VSL) + DMS, Acetonitrile (KRISS)

- 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)

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!

- 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)

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)

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)

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?)

Summary of actions agreed during the session on “Central Facilities: Central Calibration Laboratory” Chair: M. Milton,

02befc1c856fbaeed8a5bb2ec651845e.doc, 1 July 10 Rapporteur: Joële Viallon

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

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

Formaldehyde VSL certification of commercial BIPM to lead key comparison (Scott) standard at 5 ppm. Primary facility planned at BIPM 2011/2012

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

Dilution methods To be discussed at future GAWG 2011

Absorption tubes Survey of stations to determine Summer requirements. 2010

02befc1c856fbaeed8a5bb2ec651845e.doc, 1 July 10