For more information, please contact:

World Meteorological Organization

Research Department

Atmospheric Research and Environment Branch

7 bis, avenue de la Paix – P.O. Box 2300 – CH 1211 Geneva 2 – Switzerland

Tel.: +41 (0) 22 730 81 11 – Fax: +41 (0) 22 730 81 81

E-mail: AREP-MAIL@wmo.int

Website: http://www.wmo.int/pages/prog/arep/gaw/gaw_home_en.html

GAW Report No. 204

Standard Operating Procedures (SOPs)

for Air Sampling in Stainless Steel Canisters

for Non-Methane Hydrocarbons Analysis

© World Meteorological Organization, 2012

The right of publication in print, electronic and any other form and in any language is reserved by WMO. Short extracts from WMO publications may be reproduced without authorization, provided that the complete source is clearly indicated. Editorial correspondence and requests to publish, reproduce or translate this publication in part or in whole should be addressed to:

Chair, Publications BoardWorld Meteorological Organization (WMO)7 bis, avenue de la Paix Tel.: +41 (0) 22 730 84 03P.O. Box 2300 Fax: +41 (0) 22 730 80 40CH-1211 Geneva 2, Switzerland E-mail: publications@wmo.int

NOTE

The designations employed in WMO publications and the presentation of material in this publication do not imply the expression of any opinion whatsoever on the part of the Secretariat of WMO concerning the legal status of any country, territory, city or area, or of its authorities, or concerning the delimitation of its frontiers or boundaries.

Opinions expressed in WMO publications are those of the authors and do not necessarily reflect those of WMO. The mention of specific companies or products does not imply that they are endorsed or recommended by WMO in preference to others of a similar nature which are not mentioned or advertised.

This document (or report) is not an official publication of WMO and has not been subjected to its standard editorial procedures. The views expressed herein do not necessarily have the endorsement of the Organization.

WORLD METEOROLOGICAL ORGANIZATION GLOBAL ATMOSPHERE WATCH

STANDARD OPERATING PROCEDURES (SOPs) FOR AIR SAMPLING IN STAINLESS STEEL CANISTERS FOR NON-METHANE HYDROCARBONS ANALYSIS

Prepared by

Rainer Steinbrecher and Elisabeth Weiß

World Calibration Centre for Volatile Organic Compounds (WCC-VOCs)

September 2012

Table of Contents  INTRODUCTION ..............................................................................................................................................................1 1. SCOPE AND APPLICABILITY.............................................................................................................................2 2. PRINCIPLES OF SAMPLING...............................................................................................................................2 3. CAUTION ..............................................................................................................................................................3 4. REAGENTS AND MATERIALS............................................................................................................................3

4.1 Lines, tubing, connectors and valves .........................................................................................................3 4.2 Canisters ....................................................................................................................................................3 4.3 Pumps and pressure gauges .....................................................................................................................3 4.4 Filters .........................................................................................................................................................3 4.5 Gases and chemicals.................................................................................................................................4

5. CLEANING AND CONDITIONING OF CANISTERS............................................................................................4

5.1 General considerations ..............................................................................................................................4 5.2 Basic cleaning and conditioning of canisters .............................................................................................5 5.3 Destruction of microorganisms...................................................................................................................6 5.4 Check of canister blank values ..................................................................................................................6 5.5 Cleaning and conditioning of canisters with acceptable blank values........................................................6 5.6 Canister leak test .......................................................................................................................................7 5.7 Check of storage stability of NMHCs .........................................................................................................7 5.8 Transport....................................................................................................................................................7

6. CLEANING AND CONDITIONING OF THE AIR SAMPLING SYSTEM ..............................................................7

6.1 General considerations ..............................................................................................................................7 6.2 Basic cleaning and conditioning of the sampling system ...........................................................................7 6.3 Check of sampling system blank values ....................................................................................................8

7. AIR SAMPLING WITH CANISTERS ....................................................................................................................8

7.1 General considerations ..............................................................................................................................8 7.2 Canister preparation prior to sampling .......................................................................................................9 7.3 Sampling procedure ...................................................................................................................................9 7.4 Sampling protocol ......................................................................................................................................10 7.5 Equipment and canister storage ................................................................................................................10

References ......................................................................................................................................................................11 Main Contributors...........................................................................................................................................................12 Abbreviations and Acronyms........................................................................................................................................13

1

INTRODUCTION

The Global Atmosphere Watch (GAW) Programme of the World Meteorological Organization (WMO) is an international programme supporting long-term observations and analysis of the chemical composition and physical properties of the atmosphere that are relevant for understanding atmospheric composition and climate change. Reactive gases is one of the focal areas within GAW. This group includes Volatile Organic Compounds (VOCs), which are present only in trace quantities in the atmosphere but play an important role in atmospheric chemistry.

Reactive non-methane hydrocarbon compounds (NHMCs) impact the oxidizing capacity of the atmosphere, which is related to climate and air quality. VOCs are emitted by natural (biospheric) and anthropogenic (due to human activities, e.g., connected with fossil fuel processing and utilization) sources. They are removed from the atmosphere primarily by reaction with the hydroxyl radical. VOCs cause together with NOX photochemical formation of O3 and other photo-oxidant pollutants including secondary organic aerosols.

The importance of VOCs for understanding atmospheric chemistry is recognized by the research community and global coordinated observations are needed. Such a comprehensive high quality global observational network for VOCs is being established with the GAW Programme. The initial workshop held in February 2006 addressed the concept and desirable design of a VOC network, specified key species to be analyzed, formulated Data Quality Objectives (DQOs) and assigned different elements of the Quality Assurance (QA) System and data reporting (WMO, 2007). The progress in the implementation of the VOCs network is reviewed every two years at the specialized GAW expert meeting.

The QA system developed within the GAW Programme provides a framework to reach the required measurement compatibility for harmonization of data obtained by different GAW laboratories*. The most recent QA framework is described in the “WMO Global Atmosphere Watch (GAW) Strategic Plan: 2008-2015” (WMO, 2008).

The Quality Assurance system of GAW for VOCs consists of a number of elements and requires for its implementation

• The establishment and maintenance of a single reference scale (primary standard). • The establishment of the procedures linking observations to the primary standard (including

measurement guidelines and standard operating procedures, calibration procedures, guidelines for station audits and set up of comparison campaigns).

• Specification and rolling review of the Data Quality Objectives (DQOs) and the observational network by the designated Scientific Advisory Group (SAG).

• The use of harmonized terminology.

Several elements of the QA system for VOCs are currently in place, including the Central Calibration Laboratory (CCL) for NMHCs in the National Physics Laboratory (UK), the World Calibration Centre for VOCs (WCC-VOCs) at KarIsruhe Institute of Technology, Institute of Meteorology and Climate Research, Atmospheric Environmental Research (www.imk-ifu.kit.edu/wcc-voc). The WCC-VOC is funded by the German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety. The preparation of these Standard Operating Procedures (SOPs) was coordinated by the WCC-VOCs.

The Standard Operating Procedures (SOPs) described here for non-methane hydrocarbons

analysis by whole air sampling in stainless steel canisters are intended for use at stations and any other measurement platforms where VOCs are analyzed utilizing the canister sampling method. _______________

*Mention in the current document of trade names or commercial products utilized by different laboratories does not constitute endorsement or recommendation for use.

2

They also apply to institutions with experienced personnel having made these observations for many years. The present version of SOPs can be used as guidance for initiating and performing speciated non-methane hydrocarbons (NMHC) measurements for the WMO GAW network. It also contains quality control protocols to be used in the field and laboratory associated with canister air sampling.

These SOPs are based largely on the recommendations from the “Accurate Measurements

of Hydrocarbons in the Atmosphere” project AMOHA (Plass-Dülmer et al., 2006) and recommendations from US-EPA (1998, 1999) on determination of VOCs in ambient air.

Many other methods, in addition to the steel canister sampling described here, exist for whole air sampling for VOC analysis, e.g., glass flask air sampling in the US National Oceanic and Atmospheric Administration Cooperative Global Air Sampling Network (Pollmann et al., 2008). These other methods are not included in this document.

This report was drafted by the GAW expert group on VOCs and approved by the WMO

GAW Scientific Advisory Group for Reactive Gases (RG). The input and suggestions on the procedures described in this document provided by the GAW-VOC experts is appreciated as well as the contribution of the former head of the WCC-VOCs, Maurice Habram.

1. SCOPE AND APPLICABILITY This document gives guidance for sampling of atmospheric volatile non-methane

hydrocarbons (NMHCs) in whole air using electro-polished stainless steel canisters in the WMO GAW network.

The described procedures are appropriate for alkanes, alkenes, alkynes, and aromatic compounds with two to six carbon atoms (C2 to C6). NMHCs with more than six carbon atoms tend to be adsorbed on the canister surfaces and may only be partially recovered. The procedures are valid for analyzing volatile alkane, alkyl and isoprene mole fractions in continental background air with mole fractions at pmol/mol levels as well as for ambient air in and around urban areas in the range of µmol/mol. With caution, also mole fractions of alkenes and aromatics may be reported but at µmol/mol level only. These compounds tend to form artefacts in stainless steel canisters. Thus air sample storage time is recommended to be as short as possible before analysis. Hence, under conditions of normal usage for sampling ambient air, most NMHCs can be recovered from canisters near their original concentrations after storage times of up to thirty days (US-EPA, 1999). According to monitoring requirements, the sampling time may vary from seconds to several hours. From the canister samples the target compounds are then typically analysed by gas chromatography using flame ionisation detection and/or mass spectroscopy. 2. PRINCIPLES OF SAMPLING Air samples are to be collected in commercially available or custom-built electro-polished two-valve stainless steel canisters. A metal bellows or membrane (PTFE coated) pump with an in-line membrane filter is used to prevent contamination of samples. The filled canisters are either analyzed on-site or shipped to a laboratory and analyzed within a time for which their stability is guaranteed. Note: Ambient air samples may also be taken by grab sampling into evacuated canisters or by pressurizing one-valve canisters. These methods need to take into account (1) that the inner surface of the cylinder must be in equilibrium with conditions of the sample air before the sample is taken and (2) air samples at ambient pressure limit the sample size for analysis making repeated analysis from the same sample difficult. Therefore, it is recommended to use two-valve canisters.

3

3. CAUTION

• Contamination of the sampling system and canisters can occur if solvents or highly concentrated hydrocarbon gas mixtures (> 1 µmol/mol) are used around the sampling equipment and must be avoided.

• All threads and fittings in the sampling system or canisters must not be touched with bare hands but only with cleaned materials or lint free gloves.

• Tubing of canisters or pumps not in use must be capped or plugged immediately. • Pumps can be damaged if they are run with a plugged outlet for more than a few minutes. • The canister valves can be damaged by over-tightening. • The pressure in the canisters must not exceed the manufacturers specified limit (e.g., 5

bars or (74 psi) absolute). • The Good Laboratory Practice Handbook (WHO, 2009) and the general safety guidelines

for working in laboratories (BG RCI, 2011) apply in particular when working under pressure and with vacuum. The chemical compound specific safety regulations specified in the safety data sheets must be followed.

• For transport of pressurized air canisters specific transport rules may apply and must be followed.

4. REAGENTS AND MATERIALS

4.1 Lines, tubing, connectors and valves Generally, the use of materials other than stainless steel, glass, silica coated stainless steel, PFA and PTFE should be avoided for the measurement of NMHC in air samples. Especially, plastics other than PFA and PTFE must not be used to prevent memory effects.

4.2 Canisters Recommendations given in this document are limited to electro-polished stainless steel (ss) canisters. A variety of ss canisters with one or two valves may be purchased from several suppliers, e.g., Restek or TO-Can® Air Monitoring Canisters. The use of two valve canisters allows for more flexibility in air sampling and is recommended. The inner surface of the canisters is to be passivated, e.g. electro-polished. Stainless steel valves (e.g., Swagelok) must be used to seal the canisters inlets and outlets, respectively. The sampling procedures described in these SOPs are valid for two valve canisters.

4.3 Pumps and pressure gauges Air samples collected for measurements of NMHCs in small canisters must be pressurized. It is recommended to use pumps for filling the canisters that can reach a final pressure of > 3 bar ensuring a minimum gas flow rate at ambient pressure of > 10 l/min, e.g. MB-158 (metal bellows) or N 022 STE (KNF; PTFE). All parts of the pump with air contact must be of stainless steel or PTFE. Oil free vacuum pumps ensuring a vacuum of < 1 mbar have to be used e.g., the XtraDryTM 150-2 or ACP 15. Pressure can be checked by using oil free pressure gauges. The quality of the vacuum may be monitored with for instance the VD 85 instrument.

4.4 Filters A filter in the sampling system is recommended to protect the pressurizing pump and the canisters from contamination by micro-organisms and particles. A PTFE filter (pore size 0.45 µm, diameter 25 to 50 mm, stainless steel filter holder; e.g., Pall or Millipore) can be placed at the inlet of the pressurizing pump. Prior to use, a new filter must be purged with pure nitrogen (15 min with 1 l/min) or alternatively with sample air after assembling it in the sampling line because it may release traces of low volatility hydrocarbons (C7 to C12 and oxygenated VOCs). The filter membrane needs to be exchanged depending on exposure (guideline: every 25 samples for 1 L canisters).

4

4.5 Gases and chemicals All gases used for preconditioning the canisters need to be of the highest grade. If lower grade gases are used a suitable gas cleaning system must be employed and a gas purity of > 99.9999% has to be achieved. High purity water Type 1 grade must be used for cleaning and rinsing the equipment. If needed, a mild laboratory detergent together with high purity water can be used for removing surface impurities. Note: Type 1 grade reagent water can be prepared by distillation or other equal process, followed by purification with a mixed bed of ion exchange materials and a 0.2 µm membrane filter. Feedwater to the final purification step must have a maximum conductivity of 20 µS/cm at 298K (25°C). In this report, high purity water refers to this Type 1 grade reagent water. 5. CLEANING AND CONDITIONING OF CANISTERS 5.1 General considerations

To prevent contamination of air samples during their collection the components of the sampling system have to be cleaned before use. Recommendations for cleaning electro-polished stainless steel canisters are given below. The choice of a cleaning/conditioning procedure depends primarily on the grade of contamination of the canisters. Figure 1 shows a canister conditioning system. The system must be set up to stand an overpressure of 1.5 bar (22 psi) minimum in front of the canister and vacuum (< 1 mbar) after the canister. Additional information can be found in Notes 1 to 4. After cleaning, canisters are filled with clean humidified nitrogen using a gas washer (see Figure 1) until use.

Figure 1 - Conditioning system for stainless steel air sampling canisters. The flushing gas flow is adjusted to 200 ml/min. Valves are switched according to the process steps (see text)

5

Note 1: Generally the performance of canisters is not always reproducible even if they come from the same manufacturer. Different batches of canisters may exhibit different behaviour in terms of the degree of contamination and the stability of air samples. This phenomenon may be observed even within one batch. Therefore, newly procured canisters, after having been cleaned, have to be tested for their blank values and for stability of air samples. Note 2: The performance of canisters which have already been in use is influenced by the number and degree of pollution of previous air samples. Thus each canister needs its history recorded, i.e. the number and quality of air samples which passed through the canister. Different canister sets are recommended to be used for widely differing concentrations, e.g., for continental background air and urban air samples. Note 3: Canisters must be cleaned using a combination of heat, evacuation, and water. These methods have their limits with respect to the performance of the canisters. Heating at higher temperatures (>80 °C) may, e.g., damage the interior passivity and the valves. Do not use organic solvents as they may severely contaminate the canisters for a long time. Note 4: After each water refill of the humidifier, the system must be flushed for one hour and then the quality of the flushing gas checked. If some system blank problems are encountered, several additional one hour flushing steps are recommended until stable blank values are achieved. If the stable blank value still is not acceptable (>1 % of the concentration of a target compound) the inline hydrocarbon trap (charcoal filter) needs to be exchanged.

5.2 Basic cleaning and conditioning of canisters

New canisters or those previously used for collecting highly polluted air samples have to be cleaned using the following procedure (see Figure 1 for set up details; flushing gas-flow: approx. 200 ml/min):

(1) The canister (the valves need to be removed) is rinsed two times and then subsequently

filled with a mild detergent (e.g. 1% Mucasol® in high purity water) by using, e.g., a high volume syringe. After heating the canister to 80 °C the canister is placed in an ultrasonic bath for 30 min. Caution hot surfaces!

(2) The canister is then rinsed with high purity water and ultra-sonicated again for 10 min. This step is repeated two times with fresh high purity water.

(3) The canister is then finally rinsed with high purity water. (4) The removed valves are re-attached to the empty canister. (5) A leak test (see Section 5.6) must be performed before the canister is placed in a drying

oven and connected to the flushing gas system as shown in Figure 1. (6) The canister with closed valves is connected to the flushing system as shown in Figure 1.

The vacuum pump and the heater are switched on. (7) The N2-vent (4) is turned to vacuum position and the canister valve (3) is slowly opened.

The canister is subsequently dried for at least 12 h under vacuum (< 1 mbar) at 80 °C. No flushing gas flow needed.

(8) Valves of the flushing system (Figure 1) are set to the position that ensures a humidified and clean gas flow through the system (approx. 200 ml/min; dew point: 15 °C) with the N2-valve (1) in vent position. The system is purged for one hour. Watch pressure gauche! Set pressure regulator p2 to 1.5 bar (22 psi).

(9) Canister valve (2) is slowly opened. Caution: hot surface! Wait for five minutes. (10) Canister valve (3) is closed and the N2 valve (1) is slowly turned from the vent to the purge

position for filling the canister with humidified and clean nitrogen. Watch initial pressure drop followed by an increase! Pressure must not drop below 0.1 bar (2 psi) during filling. Do not over-pressurise the system (max. pressure: 1.5 bar (22 psi))!

(11) N2 valve (4) is turned to flushing position. Check gas flow and pressure. Switch off vacuum pump.

6

(12) The canister is finally flushed for 24 hours with clean and humidified (dew point 15 °C) and nitrogen at 80 ºC.

(13) After 24 hours canister flushing, the heater is switched off and the canister cooled down to room temperature.

(14) Canister valve (3) is closed and the canister is pressurized with the flushing gas to approx. 1 bar (15 psi). Do not over-pressurize the system (max. pressure: 1.5 bar (22 psi))!

(15) Canister valve (2) is closed and N2 valve (1) is turned to vent position.

The canisters are now ready for storage and use.

Caution must be taken that the system is not over-pressurized (max. pressure: 1.5 bar (22 psi)) when valves are switched. 5.3 Destruction of microorganisms

An important component of the cleaning procedure is heating to deactivate micro-organisms which may have reached the canister (micro-organisms may consume and produce NMHCs and thus alter the composition of an air sample).

The basic cleaning steps in section 5.2 ensure that the canister is sufficiently clean. 5.4 Check of canister blank values

After cleaning, pressurized canisters have to be checked for blank values. The canisters are proven suitable if blank values of the target NMHCs are less than 1% of the expected concentrations of the target compounds in air samples. A check for blank values must be repeated after every 10th sample. 5.5 Cleaning and conditioning of canisters with acceptable blank values

After analysing the air from canisters they have to be prepared for the next sampling with a humidified and clean gas flow (see below). (1) Valves of the flushing system (Figure 1) are set to the position that ensures a humidified

gas flow (approx. 200 ml/min; dew point: 15 °C) through the system with the N2 valve (1) in vent position. The system is flushed for one hour. Watch pressure gauche! Set pressure regulator p2 to 1.5 bar (22 psi).

(2) Switch the heater on (80 °C). (3) Connect the canister with closed valves to the flushing system. Open canister valve (3), set

N2 valve (4) to vent position, open canister valve (2). (4) Turn N2 valve (1) to flush position and purge canister with humidified and clean nitrogen for

1 h at 80 °C. (5) Close canister valve (3) and pressurize canister to 1 bar (15 psi) with humidified and clean

nitrogen. Do not over-pressurise the system (max. pressure: 1.5 bar (22 psi))! (6) Close canister valves (2) and turn N2 valve (1) to vent position. Caution hot surfaces! (7) Heat pressurized canister for 1 h at 80 °C. (8) Open slowly canister valve (3), then valve (2). Set N2 valve (1) to flushing position and

purge the canister with humidified nitrogen for 30 min. (9) Switch off heater and cool canister down to room temperature (10) Close canister valve (3) and pressurize canister with flushing gas to approx. 1 bar (15 psi).

Do not over-pressurise the system (max. pressure: 1.5 bar (22 psi))! (11) Close canister valve (2) and turn N2 valve (1) to vent position.

The canisters are now ready for storage and use.

Caution must be taken that the system is not over-pressurized (max. pressure: 1.5 bar (22 psi)) when valves are switched.

7

5.6 Canister leak test Canisters must be leak tested. First, canisters are pressurized to approximately 3 bar (44

psi) with clean nitrogen. The canister valves are kept closed and the initial pressure is measured. After 24 h the final pressure is checked. It is recommended that the leak rate for 1 L canisters does not exceed 0.01 mbar/h. Depressurize and condition the canister as described in Sections 5.2 or 5.5. It is recommended to perform a leak test after every 10th sample. 5.7 Check of storage stability of NMHCs

With increasing number of carbon atoms, the NMHCs tend to be lost on the canister surface during transport and storage. To check for the stability of the NMHCs, the canisters are filled with an ambient air sample. The aliquots of the sample are then analyzed immediately after sampling and repeatedly during anticipated storage time from sampling to measurement. Note: Ample evidence suggests that, in addition to the canister type, the NMHC stability in canisters is strongly dependent on the humidity of the sample. A minimum relative humidity of about 12% at room temperature is required to achieve stable NMHC concentrations (McClenny et al., 1991). 5.8 Transport

To prevent contamination of the inlet and outlet tubing sealing with appropriate caps is obligatory. It is also recommended to use a special transport case to avoid damage to cylinders and shut-off valves. 6. CLEANING AND CONDITIONING OF THE AIR SAMPLING SYSTEM 6.1 General considerations

The materials and pump used must comply with specifications in Section 4. The sampling system must be cleaned before the initial set-up to prevent a contamination of air samples during their collection. The same procedures apply if the system was contaminated during use. The cleaning and conditioning procedures must include also the pressurizing pump.

6.2 Basic cleaning and conditioning of the sampling system Procedures (1) Non-metallic parts are rinsed with high purity water and dried in a vacuum oven at 50 °C. (2) Stainless steel parts and fittings are cleaned by placing them in an ultrasonic bath with a

water based cleaning solution, e.g., Ultrasonic cleaner Elma clean 70 (Roth) for 15 min. (3) The parts are rinsed with high purity water and dried in a vacuum oven at 80 °C for 24 h. (4) After cooling down the heated parts to room temperature the sampling system is assembled

including the pressurizing pump. (5) Valves of the flushing system (Figure 2) are set to the position to ensure a humidified and

clean nitrogen flow (approx. 200 ml/min; dew point: 15 °C) through the system. (6) The entire sampling system including sampling pump and a canister is then connected to

the flushing system. (7) The pressurizing pump is switched on and canister valve (1) opened. (8) Valve (2) is opened slowly and the bypass gas flow is monitored (9) Keep valve (2) in the position with a bypass gas flow of approx. 50 ml/min. (10) The whole sampling system is then purged for 24 hours. (11) Blank values of the sampling system are then to be checked (Section 6.3). Caution must be taken that the system is not over-pressurized (max. pressure: 1.5 bar (22 psi)) when valves are switched.

8

6.3 Check of sampling system blank values The cleanliness of the whole sampling system must be checked by sampling zero air or

preconditioned nitrogen (Figure 2) into a proven clean canister following the procedures described in Section 7.3. The sampling system is proven suitable if blank values of the target NMHCs are less than 1% of the expected concentrations of the target compounds in air samples. It is recommended that blank checks of the sampling system are performed twice a year when air samples are collected continuously. For campaign based sampling it is recommended to perform a blank check before use.

Figure 2 - Conditioning system for the air sampling system with stainless steel canisters. The flushing gas flow is adjusted to 200 ml/min. Valves are switched according to the process steps (see text)

7. AIR SAMPLING WITH CANISTERS 7.1 General considerations

Canisters must be checked for leaks and blank values before air sampling. The entire sampling system and the main inlet tubing has to be clean and tight. The materials and the sampling pump used must comply with the specifications in Section 4.

Air monitoring stations even on different platforms (e.g. aircraft, shipboard, tower), typically use a main inlet tubing line and a downstream pump with high flow rate (several cubic meters per hour) to pull ambient air to a number of sampling ports. The gas samples are then usually drawn from a manifold near to the sampling device with a smaller flow rate (0.1 l/min to 0.5 l/min).

When sampling air with canisters an ozone scrubber during sampling is sometimes used (e.g. Plass-Duelmer et al., 2006). Hence only reactive alkene components such as 1,3-butadiene tend to oxidize during sampling and storage. For less reactive compounds, e.g., alkanes, no loss in stainless steel canisters has been observed. Surprisingly, this has also been reported for isoprene when ambient air with approximately 100 µg/m³ ozone was sampled into 1 L electro-polished stainless steel canisters (Leibrock, 1996; Palluau et al., 2007). This result may be explained by a rapid destruction of ozone on the stainless steel surface of sampling line and the canister. For the GAW NMHC target compounds the effect of ozone on sample integrity is assumed to be negligible and an ozone scrubber during air sampling is not required.

9

7.2 Canister preparation prior to sampling The set up of a continuous flow air sampling system for two valve canisters is schematically

shown in Figure 3. Cleaned canisters have to be prepared at the sampling location prior to air sampling. For this purpose all canisters are first flushed with sample ambient air prior to sampling (see Section 7.3). 7.3 Sampling procedure Procedure for continuous flow air sampling with 2 valve canisters (Figure 3): (1) Connect sampling system to a sampling port. (2) Open the canister valve (2). (3) Open canister valve (1), switch pump on and flush canister with sample air for a period

sufficient to exchange the volume of the canister ten times at the given sampling flow rate. (4) Close valve (2) and pressurize the canister with sample air up to 2.0 bar (29 psi).

Watch pressure gauge (3). (5) Open valve (2) to release the pressurized sample air. (6) Repeat Steps 3 and 4 three additional times. (7) Finally, pressurize the canister (valve (2) closed) up to 2.0 bar (29 psi) and close valve (1)

to retain the air sample. (8) Pack the canister in an appropriate shipping case (see Section 7.5) and ship the canister

with a copy of the sample data sheet (see Section 7.4) to the analysing laboratory. Note 1: Eight pressurization/release cycles are required when dry air at temperatures below 0 ºC is sampled to stabilize higher boiling compounds. Note 2: The technically specified maximum pump pressure must be at least 20% above the sample pressure of 2 bar (29 psi) for avoiding an overheating of the air during sampling. Sampling/pressurizing times must be checked after every 10 samples for consistency. Increasing sampling times indicate the need for pump service. Note 3: When sampling under high humidity air conditions water may condense during the pressurization step which is not a problem when analysing NMHC.

Figure 3 - Flushing and repeated pressurization/release for 2-valve-canisters

(valves closed/open according to the process step)

10

7.4 Sampling protocol The protocol needs to contain at least the following information: (1) Complete identification of the canister (each canister must have an engraved number). (2) The sampling location and sampling time period. (3) Final sampling pressure. (4) Any unusual features noted during the sampling (e.g.: canister was not pre-pressurised).

This sampling document must be kept at the site and a copy must be attached to the canister at all times. 7.5 Equipment and canister storage

The sampling equipment must be stored after sampling with capped in- and outlets in normal conditions (extreme temperatures and humidity have to be avoided) away from organic solvents. The canisters are recommended to be analyzed as soon as possible and storage time must not exceed 30 days (US-EPA, 1999). Storage time has to be documented on the sampling protocol for each canister.

11

References BG RCI (2011): Working safely in laboratories - basic principles and guidelines, 2nd edition,

BGI/GUV-I 850-0e, Jedermannverlag Germany, bgi850-0.vur.jedermann.de.

Leibrock E. (1996): Entwicklung eines gaschromatographischen Verfahrens zur Spurenanalytik von oxidierten Kohlenwasserstoffen in Luft, Wissenschafts-Verlag Maraun, Frankfurt a.M., McClenny, W.A., Pleil, J.D., Evans, G.F., Oliver, K.D., Holdren, M.W., Winberrry, W.T. (1991): Canister-based method for monitoring toxic VOCs in ambient air, J. Air Waste Manage. Assoc. 41, 1308-1318

McClenny, W.A., J.D. Pleil, G.F. Evans, K.D. Oliver, M.W. Holdren and W.T. Winberry (1991): Canister-based method for monitoring toxic VOCs in ambient air J. Air Waste Man. Ass., 41, 1308-1318

Palluau F., Ph Mirabel and M Millet (2007): Influence of ozone on the sampling and storage of volatile organic compounds in canisters, Environ Chem. Lett. 5, 51–55

Plass-Dülmer C., N. Schmidbauer J. Slemr, F. Slemr and H. D'Souza (2006): European hydrocarbon intercomparison experiment AMOHA part 4: Canister sampling of ambient air, J. Geophys. Res., 111, D04306, doi:10.1029/2005JD006351

PollmannJ., D. Helmig, J. Hueber, Ch. Plass-Dülmer and P. Tans (2008): Sampling, storage, and analysis of C2–C7 non-methane hydrocarbons from the US National Oceanic and Atmospheric Administration Cooperative Air Sampling Network glass flasks, J. Chromatogr., A 1188, 75-87

US-EPA (1998): Technical assistance document for analysis of ozone precursors, US-Environmental Protection Agency, EPA/600-R-98/161

US-EPA TO-14A (1999): Compendium of methods for the determination of toxic organic compounds in ambient air: determination of volatile organic compounds (VOCs) in ambient air using specially prepared canisters with subsequent analysis by gas chromatography, US-Environmental Protection Agency, Method TO-14A, 2nd ed., EPA/625/R-96/010b.

WHO (2009): Handbook on good laborartory practice, 2nd edition, World Health Organisation, ISBN 978 92 4 154755 0.

WMO (2007): A WMO/GAW Expert Workshop on Global Long-Term Measurements of Volatile Organic Compounds (VOCs) (Geneva, Switzerland, 30 January – 1 February 2006) (GAW Report No. 171, WMO TD No. 1373), 36 pp.

WMO (2008): WMO Global Atmosphere Watch (GAW) Strategic Plan: 2008 – 2015 (GAW Report No. 172, WMO TD No. 1384), 108 pp.

12

Main Contributors (in alphabetical order)

Detlev Helmig Institute of Arctic and Alpine Research (INSTAAR) University of Colorado 1560 30th Street Boulder, Colorado 80303 USA

Norbert Schmidbauer Norwegian Institute for Air Research P.O. Box 100 2007 Kjeller Norway

Paul C. Novelli Global Monitoring Division Earth System Research Laboratory Boulder, Colorado 80305 USA

Rainer Steinbrecher Karlsruhe Institute of Technology Institute for Meteorology and Climate Research (IMK-IFU) Kreuzeckbahnstr. 19 82467 Garmisch-Partenkirchen Germany

Christian Plass-Duelmer Deutscher Wetterdienst Meteorologisches Observatorium Hohenpeissenberg Albin-Schwaiger-Weg 10 82383 Hohenpeissenberg Germany

Elisabeth Weiß Karlsruhe Institute of Technology Institute for Meteorology and Climate Research (IMK-IFU) Kreuzeckbahnstr. 19 82467 Garmisch-Partenkirchen Germany

13

Abbreviations and Acronyms

ACP 15 Compact oil free vacuum pump from Adixen

AMOHA “Accurate Measurements of Hydrocarbons in the Atmosphere” project CCL Central Calibration Laboratory DQOs Data Quality Objectives GAW Global Atmosphere Watch Programme KNF Kurt Neuberger KG in Freiburg pupm company MB-158 Metal Bellows Vacuum Pump NHMCs Non-Methane Hydrocarbons PFA perfluoroalkoxy PTFE polytetrafluoroethylene QA Quality Assurance RCI Raw Materials and Chemical Industry RG Reactive Gases SAG Scientific Advisory Group SOPs Standard Operating Procedures ss stainless steel US-EPA Environment Protection Agency of USA VD85 Digital Compact Vacuum Meters VOCs Volatile Organic Compounds WCC-VOC World Calibration Centre for VOCs WHO World Health Organisation WMO World Meteorological Organization XtraDry™ 150-2

High-performance dry and oil-free piston vacuum pump

15

GLOBAL ATMOSPHERE WATCH REPORT SERIES

1. Final Report of the Expert Meeting on the Operation of Integrated Monitoring Programmes, Geneva, 2 -5 September 1980. 2. Report of the Third Session of the GESAMP Working Group on the Interchange of Pollutants Between the Atmosphere and

the Oceans (INTERPOLL-III), Miami, USA, 27-31 October 1980. 3. Report of the Expert Meeting on the Assessment of the Meteorological Aspects of the First Phase of EMEP, Shinfield Park,

U.K., 30 March - 2 April 1981. 4. Summary Report on the Status of the WMO Background Air Pollution Monitoring Network as at April 1981. 5. Report of the WMO/UNEP/ICSU Meeting on Instruments, Standardization and Measurements Techniques for Atmospheric

CO2, Geneva, 8-11; September 1981. 6. Report of the Meeting of Experts on BAPMoN Station Operation, Geneva, 23–26 November 1981. 7. Fourth Analysis on Reference Precipitation Samples by the Participating World Meteorological Organization Laboratories by

Robert L. Lampe and John C. Puzak, December 1981. 8. Review of the Chemical Composition of Precipitation as Measured by the WMO BAPMoN by Prof. Dr. Hans-Walter Georgii,

February 1982. 9. An Assessment of BAPMoN Data Currently Available on the Concentration of CO2 in the Atmosphere by M.R. Manning,

February 1982. 10. Report of the Meeting of Experts on Meteorological Aspects of Long-range Transport of Pollutants, Toronto, Canada, 30

November - 4 December 1981. 11. Summary Report on the Status of the WMO Background Air Pollution Monitoring Network as at May 1982. 12. Report on the Mount Kenya Baseline Station Feasibility Study edited by Dr. Russell C. Schnell. 13. Report of the Executive Committee Panel of Experts on Environmental Pollution, Fourth Session, Geneva, 27 September - 1

October 1982. 14. Effects of Sulphur Compounds and Other Pollutants on Visibility by Dr. R.F. Pueschel, April 1983. 15. Provisional Daily Atmospheric Carbon Dioxide Concentrations as Measured at BAPMoN Sites for the Year 1981, May 1983. 16. Report of the Expert Meeting on Quality Assurance in BAPMoN, Research Triangle Park, North Carolina, USA, 17-21

January 1983. 17. General Consideration and Examples of Data Evaluation and Quality Assurance Procedures Applicable to BAPMoN

Precipitation Chemistry Observations by Dr. Charles Hakkarinen, July 1983. 18. Summary Report on the Status of the WMO Background Air Pollution Monitoring Network as at May 1983. 19. Forecasting of Air Pollution with Emphasis on Research in the USSR by M.E. Berlyand, August 1983. 20. Extended Abstracts of Papers to be Presented at the WMO Technical Conference on Observation and Measurement of

Atmospheric Contaminants (TECOMAC), Vienna, 17-21 October 1983. 21. Fifth Analysis on Reference Precipitation Samples by the Participating World Meteorological Organization Laboratories by

Robert L. Lampe and William J. Mitchell, November 1983. 22. Report of the Fifth Session of the WMO Executive Council Panel of Experts on Environmental Pollution, Garmisch-

Partenkirchen, Federal Republic of Germany, 30 April - 4 May 1984 (WMO TD No. 10). 23. Provisional Daily Atmospheric Carbon Dioxide Concentrations as Measured at BAPMoN Sites for the Year 1982. November

1984 (WMO TD No. 12).

16

24. Final Report of the Expert Meeting on the Assessment of the Meteorological Aspects of the Second Phase of EMEP, Friedrichshafen, Federal Republic of Germany, 7-10 December 1983. October 1984 (WMO TD No. 11).

25. Summary Report on the Status of the WMO Background Air Pollution Monitoring Network as at May 1984. November 1984

(WMO TD No. 13). 26. Sulphur and Nitrogen in Precipitation: An Attempt to Use BAPMoN and Other Data to Show Regional and Global Distribution

by Dr. C.C. Wallén. April 1986 (WMO TD No. 103). 27. Report on a Study of the Transport of Sahelian Particulate Matter Using Sunphotometer Observations by Dr. Guillaume A.

d'Almeida. July 1985 (WMO TD No. 45). 28. Report of the Meeting of Experts on the Eastern Atlantic and Mediterranean Transport Experiment ("EAMTEX"), Madrid and

Salamanca, Spain, 6-8 November 1984. 29. Recommendations on Sunphotometer Measurements in BAPMoN Based on the Experience of a Dust Transport Study in

Africa by Dr. Guillaume A. d'Almeida. September 1985 (WMO TD No. 67). 30. Report of the Ad-hoc Consultation on Quality Assurance Procedures for Inclusion in the BAPMoN Manual, Geneva, 29-31

May 1985. 31. Implications of Visibility Reduction by Man-Made Aerosols (Annex to No. 14) by R.M. Hoff and L.A. Barrie. October 1985

(WMO TD No. 59). 32. Manual for BAPMoN Station Operators by E. Meszaros and D.M. Whelpdale. October 1985 (WMO TD No. 66). 33. Man and the Composition of the Atmosphere: BAPMoN - An international programme of national needs, responsibility and

benefits by R.F. Pueschel, 1986. 34. Practical Guide for Estimating Atmospheric Pollution Potential by Dr. L.E. Niemeyer. August 1986 (WMO TD No. 134). 35. Provisional Daily Atmospheric CO2 Concentrations as Measured at BAPMoN Sites for the Year 1983. December 1985

(WMO TD No. 77). 36. Global Atmospheric Background Monitoring for Selected Environmental Parameters. BAPMoN Data for 1984. Volume I:

Atmospheric Aerosol Optical Depth. October 1985 (WMO TD No. 96). 37. Air-Sea Interchange of Pollutants by R.A. Duce. September 1986 (WMO TD No. 126). 38. Summary Report on the Status of the WMO Background Air Pollution Monitoring Network as at 31 December 1985.

September 1986 (WMO TD No. 136). 39. Report of the Third WMO Expert Meeting on Atmospheric Carbon Dioxide Measurement Techniques, Lake Arrowhead,

California, USA, 4-8 November 1985. October 1986. 40. Report of the Fourth Session of the CAS Working Group on Atmospheric Chemistry and Air Pollution, Helsinki, Finland, 18-

22 November 1985. January 1987. 41. Global Atmospheric Background Monitoring for Selected Environmental Parameters. BAPMoN Data for 1982, Volume II:

Precipitation chemistry, continuous atmospheric carbon dioxide and suspended particulate matter. June 1986 (WMO TD No. 116).

42. Scripps reference gas calibration system for carbon dioxide-in-air standards: revision of 1985 by C.D. Keeling, P.R.

Guenther and D.J. Moss. September 1986 (WMO TD No. 125). 43. Recent progress in sunphotometry (determination of the aerosol optical depth). November 1986. 44. Report of the Sixth Session of the WMO Executive Council Panel of Experts on Environmental Pollution, Geneva, 5-9 May

1986. March 1987. 45. Proceedings of the International Symposium on Integrated Global Monitoring of the State of the Biosphere (Volumes I-IV),

Tashkent, USSR, 14-19 October 1985. December 1986 (WMO TD No. 151).

17

46. Provisional Daily Atmospheric Carbon Dioxide Concentrations as Measured at BAPMoN Sites for the Year 1984. December 1986 (WMO TD No. 158).

47. Procedures and Methods for Integrated Global Background Monitoring of Environmental Pollution by F.Ya. Rovinsky, USSR

and G.B. Wiersma, USA. August 1987 (WMO TD No. 178). 48. Meeting on the Assessment of the Meteorological Aspects of the Third Phase of EMEP IIASA, Laxenburg, Austria, 30 March

- 2 April 1987. February 1988. 49. Proceedings of the WMO Conference on Air Pollution Modelling and its Application (Volumes I-III), Leningrad, USSR, 19-24

May 1986. November 1987 (WMO TD No. 187). 50. Provisional Daily Atmospheric Carbon Dioxide Concentrations as Measured at BAPMoN Sites for the Year 1985. December

1987 (WMO TD No. 198). 51. Report of the NBS/WMO Expert Meeting on Atmospheric CO2 Measurement Techniques, Gaithersburg, USA, 15-17 June

1987. December 1987. 52. Global Atmospheric Background Monitoring for Selected Environmental Parameters. BAPMoN Data for 1985. Volume I:

Atmospheric Aerosol Optical Depth. September 1987. 53. WMO Meeting of Experts on Strategy for the Monitoring of Suspended Particulate Matter in BAPMoN - Reports and papers

presented at the meeting, Xiamen, China, 13-17 October 1986. October 1988. 54. Global Atmospheric Background Monitoring for Selected Environmental Parameters. BAPMoN Data for 1983, Volume II:

Precipitation chemistry, continuous atmospheric carbon dioxide and suspended particulate matter (WMO TD No. 283). 55. Summary Report on the Status of the WMO Background Air Pollution Monitoring Network as at 31 December 1987 (WMO

TD No. 284). 56. Report of the First Session of the Executive Council Panel of Experts/CAS Working Group on Environmental Pollution and

Atmospheric Chemistry, Hilo, Hawaii, 27-31 March 1988. June 1988. 57. Global Atmospheric Background Monitoring for Selected Environmental Parameters. BAPMoN Data for 1986, Volume I:

Atmospheric Aerosol Optical Depth. July 1988. 58. Provisional Daily Atmospheric Carbon Dioxide Concentrations as measured at BAPMoN sites for the years 1986 and 1987

(WMO TD No. 306). 59. Extended Abstracts of Papers Presented at the Third International Conference on Analysis and Evaluation of Atmospheric

CO2 Data - Present and Past, Hinterzarten, Federal Republic of Germany, 16-20 October 1989 (WMO TD No. 340). 60. Global Atmospheric Background Monitoring for Selected Environmental Parameters. BAPMoN Data for 1984 and 1985,

Volume II: Precipitation chemistry, continuous atmospheric carbon dioxide and suspended particulate matter. 61. Global Atmospheric Background Monitoring for Selected Environmental Parameters. BAPMoN Data for 1987 and 1988,

Volume I: Atmospheric Aerosol Optical Depth. 62. Provisional Daily Atmospheric Carbon Dioxide Concentrations as measured at BAPMoN sites for the year 1988 (WMO TD

No. 355). 63. Report of the Informal Session of the Executive Council Panel of Experts/CAS Working Group on Environmental Pollution

and Atmospheric Chemistry, Sofia, Bulgaria, 26 and 28 October 1989. 64. Report of the consultation to consider desirable locations and observational practices for BAPMoN stations of global

importance, Bermuda Research Station, 27-30 November 1989. 65. Report of the Meeting on the Assessment of the Meteorological Aspects of the Fourth Phase of EMEP, Sofia, Bulgaria, 27

and 31 October 1989. 66. Summary Report on the Status of the WMO Global Atmosphere Watch Stations as at 31 December 1990 (WMO TD No.

419).

18

67. Report of the Meeting of Experts on Modelling of Continental, Hemispheric and Global Range Transport, Transformation and Exchange Processes, Geneva, 5-7 November 1990.

68. Global Atmospheric Background Monitoring for Selected Environmental Parameters. BAPMoN Data For 1989, Volume I:

Atmospheric Aerosol Optical Depth. 69. Provisional Daily Atmospheric Carbon Dioxide Concentrations as measured at Global Atmosphere Watch (GAW)-BAPMoN

sites for the year 1989 (WMO TD No. 400). 70. Report of the Second Session of EC Panel of Experts/CAS Working Group on Environmental Pollution and Atmospheric

Chemistry, Santiago, Chile, 9-15 January 1991 (WMO TD No. 633). 71. Report of the Consultation of Experts to Consider Desirable Observational Practices and Distribution of GAW Regional

Stations, Halkidiki, Greece, 9-13 April 1991 (WMO TD No. 433). 72. Integrated Background Monitoring of Environmental Pollution in Mid-Latitude Eurasia by Yu.A. Izrael and F.Ya. Rovinsky,

USSR (WMO TD No. 434). 73. Report of the Experts Meeting on Global Aerosol Data System (GADS), Hampton, Virginia, 11 to 12 September 1990 (WMO

TD No. 438). 74. Report of the Experts Meeting on Aerosol Physics and Chemistry, Hampton, Virginia, 30 to 31 May 1991 (WMO TD No. 439). 75. Provisional Daily Atmospheric Carbon Dioxide Concentrations as measured at Global Atmosphere Watch (GAW)-BAPMoN

sites for the year 1990 (WMO TD No. 447). 76. The International Global Aerosol Programme (IGAP) Plan: Overview (WMO TD No. 445). 77. Report of the WMO Meeting of Experts on Carbon Dioxide Concentration and Isotopic Measurement Techniques, Lake

Arrowhead, California, 14-19 October 1990. 78. Global Atmospheric Background Monitoring for Selected Environmental Parameters BAPMoN Data for 1990, Volume I:

Atmospheric Aerosol Optical Depth (WMO TD No. 446). 79. Report of the Meeting of Experts to Consider the Aerosol Component of GAW, Boulder, 16 to 19 December 1991 (WMO TD

No. 485). 80. Report of the WMO Meeting of Experts on the Quality Assurance Plan for the GAW, Garmisch-Partenkirchen, Germany, 26-

30 March 1992 (WMO TD No. 513). 81. Report of the Second Meeting of Experts to Assess the Response to and Atmospheric Effects of the Kuwait Oil Fires,

Geneva, Switzerland, 25-29 May 1992 (WMO TD No. 512). 82. Global Atmospheric Background Monitoring for Selected Environmental Parameters BAPMoN Data for 1991, Volume I:

Atmospheric Aerosol Optical Depth (WMO TD No. 518). 83. Report on the Global Precipitation Chemistry Programme of BAPMoN (WMO TD No. 526). 84. Provisional Daily Atmospheric Carbon Dioxide Concentrations as measured at GAW-BAPMoN sites for the year 1991 (WMO

TD No. 543). 85. Chemical Analysis of Precipitation for GAW: Laboratory Analytical Methods and Sample Collection Standards by Dr Jaroslav

Santroch (WMO TD No. 550). 86. The Global Atmosphere Watch Guide, 1993 (WMO TD No. 553). 87. Report of the Third Session of EC Panel/CAS Working Group on Environmental Pollution and Atmospheric Chemistry,

Geneva, 8-11 March 1993 (WMO TD No. 555). 88. Report of the Seventh WMO Meeting of Experts on Carbon Dioxide Concentration and Isotopic Measurement Techniques,

Rome, Italy, 7-10 September 1993, (edited by Graeme I. Pearman and James T. Peterson) (WMO TD No. 669). 89. 4th International Conference on CO2 (Carqueiranne, France, 13-17 September 1993) (WMO TD No. 561).

19

90. Global Atmospheric Background Monitoring for Selected Environmental Parameters GAW Data for 1992, Volume I: Atmospheric Aerosol Optical Depth (WMO TD No. 562).

91. Extended Abstracts of Papers Presented at the WMO Region VI Conference on the Measurement and Modelling of

Atmospheric Composition Changes Including Pollution Transport, Sofia, 4 to 8 October 1993 (WMO TD No. 563). 92. Report of the Second WMO Meeting of Experts on the Quality Assurance/Science Activity Centres of the Global Atmosphere

Watch, Garmisch-Partenkirchen, 7-11 December 1992 (WMO TD No. 580). 93. Report of the Third WMO Meeting of Experts on the Quality Assurance/Science Activity Centres of the Global Atmosphere

Watch, Garmisch-Partenkirchen, 5-9 July 1993 (WMO TD No. 581). 94. Report on the Measurements of Atmospheric Turbidity in BAPMoN (WMO TD No. 603). 95. Report of the WMO Meeting of Experts on UV-B Measurements, Data Quality and Standardization of UV Indices, Les

Diablerets, Switzerland, 25-28 July 1994 (WMO TD No. 625). 96. Global Atmospheric Background Monitoring for Selected Environmental Parameters WMO GAW Data for 1993, Volume I:

Atmospheric Aerosol Optical Depth. 97. Quality Assurance Project Plan (QAPjP) for Continuous Ground Based Ozone Measurements (WMO TD No. 634). 98. Report of the WMO Meeting of Experts on Global Carbon Monoxide Measurements, Boulder, USA, 7-11 February 1994

(WMO TD No. 645). 99. Status of the WMO Global Atmosphere Watch Programme as at 31 December 1993 (WMO TD No. 636). 100. Report of the Workshop on UV-B for the Americas, Buenos Aires, Argentina, 22-26 August 1994. 101. Report of the WMO Workshop on the Measurement of Atmospheric Optical Depth and Turbidity, Silver Spring, USA, 6-10

December 1993, (edited by Bruce Hicks) (WMO TD No. 659). 102. Report of the Workshop on Precipitation Chemistry Laboratory Techniques, Hradec Kralove, Czech Republic, 17-21 October

1994 (WMO TD No. 658). 103. Report of the Meeting of Experts on the WMO World Data Centres, Toronto, Canada, 17 - 18 February 1995, (prepared by

Edward Hare) (WMO TD No. 679). 104. Report of the Fourth WMO Meeting of Experts on the Quality Assurance/Science Activity Centres (QA/SACs) of the Global

Atmosphere Watch, jointly held with the First Meeting of the Coordinating Committees of IGAC-GLONET and IGAC-ACE, Garmisch-Partenkirchen, Germany, 13 to 17 March 1995 (WMO TD No. 689).

105. Report of the Fourth Session of the EC Panel of Experts/CAS Working Group on Environmental Pollution and Atmospheric

Chemistry (Garmisch, Germany, 6-11 March 1995) (WMO TD No. 718). 106. Report of the Global Acid Deposition Assessment (edited by D.M. Whelpdale and M-S. Kaiser) (WMO TD No. 777). 107. Extended Abstracts of Papers Presented at the WMO-IGAC Conference on the Measurement and Assessment of

Atmospheric Composition Change (Beijing, China, 9-14 October 1995) (WMO TD No. 710). 108. Report of the Tenth WMO International Comparison of Dobson Spectrophotometers (Arosa, Switzerland, 24 July - 4 August

1995). 109. Report of an Expert Consultation on 85Kr and 222Rn: Measurements, Effects and Applications (Freiburg, Germany, 28-31

March 1995) (WMO TD No. 733). 110. Report of the WMO-NOAA Expert Meeting on GAW Data Acquisition and Archiving (Asheville, NC, USA, 4-8 November

1995) (WMO TD No. 755). 111. Report of the WMO-BMBF Workshop on VOC Establishment of a “World Calibration/Instrument Intercomparison Facility for

VOC” to Serve the WMO Global Atmosphere Watch (GAW) Programme (Garmisch-Partenkirchen, Germany, 17-21 December 1995) (WMO TD No. 756).

20

112. Report of the WMO/STUK Intercomparison of Erythemally-Weighted Solar UV Radiometers, Spring/Summer 1995, Helsinki, Finland (WMO TD No. 781).

112A. Report of the WMO/STUK ’95 Intercomparison of broadband UV radiometers: a small-scale follow-up study in 1999, Helsinki,

2001, Addendum to GAW Report No. 112. 113. The Strategic Plan of the Global Atmosphere Watch (GAW) (WMO TD No. 802). 114. Report of the Fifth WMO Meeting of Experts on the Quality Assurance/Science Activity Centres (QA/SACs) of the Global

Atmosphere Watch, jointly held with the Second Meeting of the Coordinating Committees of IGAC-GLONET and IGAC-ACEEd, Garmisch-Partenkirchen, Germany, 15-19 July 1996 (WMO TD No. 787).

115. Report of the Meeting of Experts on Atmospheric Urban Pollution and the Role of NMSs (Geneva, 7-11 October 1996)

(WMO TD No. 801). 116. Expert Meeting on Chemistry of Aerosols, Clouds and Atmospheric Precipitation in the Former USSR (Saint Petersburg,

Russian Federation, 13-15 November 1995). 117. Report and Proceedings of the Workshop on the Assessment of EMEP Activities Concerning Heavy Metals and Persistent

Organic Pollutants and their Further Development (Moscow, Russian Federation, 24-26 September 1996) (Volumes I and II) (WMO TD No. 806).

118. Report of the International Workshops on Ozone Observation in Asia and the Pacific Region (IWOAP, IWOAP-II), (IWOAP,

27 February-26 March 1996 and IWOAP-II, 20 August-18 September 1996) (WMO TD No. 827). 119. Report on BoM/NOAA/WMO International Comparison of the Dobson Spectrophotometers (Perth Airport, Perth, Australia, 3-

14 February 1997), (prepared by Robert Evans and James Easson) (WMO TD No. 828). 120. WMO-UMAP Workshop on Broad-Band UV Radiometers (Garmisch-Partenkirchen, Germany, 22 to 23 April 1996) (WMO TD

No. 894). 121. Report of the Eighth WMO Meeting of Experts on Carbon Dioxide Concentration and Isotopic Measurement Techniques

(prepared by Thomas Conway) (Boulder, CO, 6-11 July 1995) (WMO TD No. 821). 122. Report of Passive Samplers for Atmospheric Chemistry Measurements and their Role in GAW (prepared by Greg

Carmichael) (WMO TD No. 829). 123. Report of WMO Meeting of Experts on GAW Regional Network in RA VI, Budapest, Hungary, 5 to 9 May 1997. 124. Fifth Session of the EC Panel of Experts/CAS Working Group on Environmental Pollution and Atmospheric Chemistry,

(Geneva, Switzerland, 7-10 April 1997) (WMO TD No. 898). 125. Instruments to Measure Solar Ultraviolet Radiation, Part 1: Spectral Instruments (lead author G. Seckmeyer) (WMO TD No.

1066), 2001. 126. Guidelines for Site Quality Control of UV Monitoring (lead author A.R. Webb) (WMO TD No. 884), 1998. 127. Report of the WMO-WHO Meeting of Experts on Standardization of UV Indices and their Dissemination to the Public (Les

Diablerets, Switzerland, 21-25 July 1997) (WMO TD No. 921). 128. The Fourth Biennial WMO Consultation on Brewer Ozone and UV Spectrophotometer Operation, Calibration and Data

Reporting, (Rome, Italy, 22-25 September 1996) (WMO TD No. 918). 129. Guidelines for Atmospheric Trace Gas Data Management (Ken Masarie and Pieter Tans), 1998 (WMO TD No. 907). 130. Jülich Ozone Sonde Intercomparison Experiment (JOSIE, 5 February to 8 March 1996), (H.G.J. Smit and D. Kley) (WMO TD

No. 926). 131. WMO Workshop on Regional Transboundary Smoke and Haze in Southeast Asia (Singapore, 2 to 5 June 1998) (Gregory R.

Carmichael). Two volumes. 132. Report of the Ninth WMO Meeting of Experts on Carbon Dioxide Concentration and Related Tracer Measurement

Techniques (Edited by Roger Francey), (Aspendale, Vic., Australia).

21

133. Workshop on Advanced Statistical Methods and their Application to Air Quality Data Sets (Helsinki, 14-18 September 1998) (WMO TD No. 956).

134. Guide on Sampling and Analysis Techniques for Chemical Constituents and Physical Properties in Air and Precipitation as

Applied at Stations of the Global Atmosphere Watch. Carbon Dioxide (WMO TD No. 980). 135. Sixth Session of the EC Panel of Experts/CAS Working Group on Environmental Pollution and Atmospheric Chemistry

(Zurich, Switzerland, 8-11 March 1999) (WMO TD No.1002). 136. WMO/EMEP/UNEP Workshop on Modelling of Atmospheric Transport and Deposition of Persistent Organic Pollutants and

Heavy Metals (Geneva, Switzerland, 16-19 November 1999) (Volumes I and II) (WMO TD No. 1008). 137. Report and Proceedings of the WMO RA II/RA V GAW Workshop on Urban Environment (Beijing, China, 1-4 November

1999) (WMO-TD. 1014) (Prepared by Greg Carmichael). 138. Reports on WMO International Comparisons of Dobson Spectrophotometers, Parts I – Arosa, Switzerland, 19-31 July 1999,

Part II – Buenos Aires, Argentina (29 Nov. – 12 Dec. 1999 and Part III – Pretoria, South Africa (18 March – 10 April 2000) (WMO TD No. 1016).

139. The Fifth Biennial WMO Consultation on Brewer Ozone and UV Spectrophotometer Operation, Calibration and Data

Reporting (Halkidiki, Greece, September 1998)(WMO TD No. 1019). 140. WMO/CEOS Report on a Strategy for Integrating Satellite and Ground-based Observations of Ozone (WMO TD No. 1046). 141. Report of the LAP/COST/WMO Intercomparison of Erythemal Radiometers Thessaloniki, Greece, 13-23 September 1999)

(WMO TD No. 1051). 142. Strategy for the Implementation of the Global Atmosphere Watch Programme (2001-2007), A Contribution to the

Implementation of the Long-Term Plan (WMO TD No.1077). 143. Global Atmosphere Watch Measurements Guide (WMO TD No. 1073). 144. Report of the Seventh Session of the EC Panel of Experts/CAS Working Group on Environmental Pollution and Atmospheric

Chemistry and the GAW 2001 Workshop (Geneva, Switzerland, 2 to 5 April 2001) (WMO TD No. 1104). 145. WMO GAW International Comparisons of Dobson Spectrophotometers at the Meteorological Observatory

Hohenpeissenberg, Germany (21 May – 10 June 2000, MOHp2000-1), 23 July – 5 August 2000, MOHp2000-2), (10 – 23 June 2001, MOHp2001-1) and (8 to 21 July 2001, MOHp2001-2). Prepared by Ulf Köhler (WMO TD No. 1114).

146. Quality Assurance in monitoring solar ultraviolet radiation: the state of the art. (WMO TD No. 1180), 2003. 147. Workshop on GAW in RA VI (Europe), Riga, Latvia, 27-30 May 2002. (WMO TD No. 1206). 148. Report of the Eleventh WMO/IAEA Meeting of Experts on Carbon Dioxide Concentration and Related Tracer Measurement

Techniques (Tokyo, Japan, 25-28 September 2001) (WMO TD No 1138). 149. Comparison of Total Ozone Measurements of Dobson and Brewer Spectrophotometers and Recommended Transfer

Functions (prepared by J. Staehelin, J. Kerr, R. Evans and K. Vanicek) (WMO TD No. 1147). 150. Updated Guidelines for Atmospheric Trace Gas Data Management (Prepared by Ken Maserie and Pieter Tans (WMO TD

No. 1149). 151. Report of the First CAS Working Group on Environmental Pollution and Atmospheric Chemistry (Geneva, Switzerland, 18-19

March 2003) (WMO TD No. 1181). 152. Current Activities of the Global Atmosphere Watch Programme (as presented at the 14th World Meteorological Congress,

May 2003). (WMO TD No. 1168). 153. WMO/GAW Aerosol Measurement Procedures: Guidelines and Recommendations. (WMO TD No. 1178). 154. WMO/IMEP-15 Trace Elements in Water Laboratory Intercomparison. (WMO TD No. 1195).

22

155. 1st International Expert Meeting on Sources and Measurements of Natural Radionuclides Applied to Climate and Air Quality Studies (Gif sur Yvette, France, 3-5 June 2003) (WMO TD No. 1201).

156. Addendum for the Period 2005-2007 to the Strategy for the Implementation of the Global Atmosphere Watch Programme

(2001-2007), GAW Report No. 142 (WMO TD No. 1209). 157. JOSIE-1998 Performance of EEC Ozone Sondes of SPC-6A and ENSCI-Z Type (Prepared by Herman G.J. Smit and

Wolfgang Straeter) (WMO TD No. 1218). 158. JOSIE-2000 Jülich Ozone Sonde Intercomparison Experiment 2000. The 2000 WMO international intercomparison of

operating procedures for ECC-ozone sondes at the environmental simulation facility at Jülich (Prepared by Herman G.J. Smit and Wolfgang Straeter) (WMO TD No. 1225).

159. IGOS-IGACO Report - September 2004 (WMO TD No. 1235), 68 pp, September 2004. 160. Manual for the GAW Precipitation Chemistry Programme (Guidelines, Data Quality Objectives and Standard Operating

Procedures) (WMO TD No. 1251), 186 pp, November 2004. 161 12th WMO/IAEA Meeting of Experts on Carbon Dioxide Concentration and Related Tracers Measurement Techniques

(Toronto, Canada, 15-18 September 2003), 274 pp, May 2005. 162. WMO/GAW Experts Workshop on a Global Surface-Based Network for Long Term Observations of Column Aerosol Optical

Properties, Davos, Switzerland, 8-10 March 2004 (edited by U. Baltensperger, L. Barrie and C. Wehrli) (WMO TD No. 1287), 153 pp, November 2005.

163. World Meteorological Organization Activities in Support of the Vienna Convention on Protection of the Ozone Layer (WMO

No. 974), 4 pp, September 2005. 164. Instruments to Measure Solar Ultraviolet Radiation: Part 2: Broadband Instruments Measuring Erythemally Weighted Solar

Irradiance (WMO TD No. 1289), 55 pp, July 2008, electronic version 2006. 165. Report of the CAS Working Group on Environmental Pollution and Atmospheric Chemistry and the GAW 2005 Workshop,

14-18 March 2005, Geneva, Switzerland (WMO TD No. 1302), 189 pp, March 2005.

166. Joint WMO-GAW/ACCENT Workshop on The Global Tropospheric Carbon Monoxide Observations System, Quality Assurance and Applications (EMPA, Dübendorf, Switzerland, 24 – 26 October 2005) (edited by J. Klausen) (WMO TD No. 1335), 36 pp, September 2006.

167. The German Contribution to the WMO Global Atmosphere Watch Programme upon the 225th Anniversary of GAW

Hohenpeissenberg Observatory (edited by L.A. Barrie, W. Fricke and R. Schleyer (WMO TD No. 1336), 124 pp, December 2006.

168. 13th WMO/IAEA Meeting of Experts on Carbon Dioxide Concentration and Related Tracers Measurement Techniques

(Boulder, Colorado, USA, 19-22 September 2005) (edited by J.B. Miller) (WMO TD No. 1359), 40 pp, December 2006. 169. Chemical Data Assimilation for the Observation of the Earth’s Atmosphere – ACCENT/WMO Expert Workshop in support of

IGACO (edited by L.A. Barrie, J.P. Burrows, P. Monks and P. Borrell) (WMO TD No. 1360), 196 pp, December 2006. 170. WMO/GAW Expert Workshop on the Quality and Applications of European GAW Measurements (Tutzing, Germany, 2-5

November 2004) (WMO TD No. 1367). 171. A WMO/GAW Expert Workshop on Global Long-Term Measurements of Volatile Organic Compounds (VOCs) (Geneva,

Switzerland, 30 January – 1 February 2006) (WMO TD No. 1373), 36 pp, February 2007. 172. WMO Global Atmosphere Watch (GAW) Strategic Plan: 2008 – 2015 (WMO TD No. 1384), 108 pp, August 2008. 173. Report of the CAS Joint Scientific Steering Committee on Environmental Pollution and Atmospheric Chemistry (Geneva,

Switzerland, 11-12 April 2007) (WMO TD No.1410), 33 pp, June 2008. 174. World Data Centre for Greenhouse Gases Data Submission and Dissemination Guide (WMO TD No. 1416), 50 pp, January

2008.

23

175. The Ninth Biennial WMO Consultation on Brewer Ozone and UV Spectrophotometer Operation, Calibration and Data Reporting (Delft, Netherlands, 31-May – 3 June 2005) (WMO TD No. 1419), 69 pp, March 2008.

176. The Tenth Biennial WMO Consultation on Brewer Ozone and UV Spectrophotometer Operation, Calibration and Data

Reporting (Northwich, United Kingdom, 4-8 June 2007) (WMO TD No. 1420), 61 pp, March 2008. 177. Joint Report of COST Action 728 and GURME – Overview of Existing Integrated (off-line and on-line) Mesoscale

Meteorological and Chemical Transport Modelling in Europe (ISBN 978-1-905313-56-3) (WMO TD No. 1427), 106 pp, May 2008.

178. Plan for the implementation of the GAW Aerosol Lidar Observation Network GALION, (Hamburg, Germany, 27 - 29 March

2007) (WMO TD No. 1443), 52 pp, November 2008. 179. Intercomparison of Global UV Index from Multiband Radiometers: Harmonization of Global UVI and Spectral Irradiance

(WMO TD No. 1454), 61 pp, March 2009. 180. Towards a Better Knowledge of Umkehr Measurements: A Detailed Study of Data from Thirteen Dobson Intercomparisons

(WMO TD No. 1456), 50 pp, December 2008. 181. Joint Report of COST Action 728 and GURME – Overview of Tools and Methods for Meteorological and Air Pollution

Mesoscale Model Evaluation and User Training (WMO TD No. 1457), 121 pp, November 2008. 182. IGACO-Ozone and UV Radiation Implementation Plan (WMO TD No. 1465), 49 pp, April 2009. 183. Operations Handbook – Ozone Observations with a Dobson Spectrophotometer (WMO TD No. 1469), 91 pp, March 2009. 184. Technical Report of Global Analysis Method for Major Greenhouse Gases by the World Data Center for Greenhouse Gases

(WMO TD No. 1473), 29 pp, June 2009. 185. Guidelines for the Measurement of Methane and Nitrous Oxide and their Quality Assurance (WMO TD No. 1478), 49 pp,

September 2009. 186. 14th WMO/IAEA Meeting of Experts on Carbon Dioxide, Other Greenhouse Gases and Related Tracers Measurement

Techniques (Helsinki, Finland, 10-13 September 2007) (WMO TD No. 1487), 31 pp, April 2009. 187. Joint Report of COST Action 728 and GURME – Review of the Capabilities of Meteorological and Chemistry-Transport

Models for Describing and Predicting Air Pollution Episodes (ISBN 978-1-905313-77-8) (WMO TD No. 1502), 69 pp, December 2009, electronic version -July 2009.

188. Revision of the World Data Centre for Greenhouse Gases Data Submission and Dissemination Guide (WMO TD No.1507),

55 pp, November 2009. 189. Report of the MACC/GAW Session on the Near-Real-Time Delivery of the GAW Observations of Reactive Gases, Garmisch-

Partenkirchen, Germany, 6-8 October 2009, (WMO TD No. 1527), 31 pp. August 2010. 190. Instruments to Measure Solar Ultraviolet Radiation Part 3: Multi-channel filter instruments (lead author: G. Seckmeyer)

(WMO TD No. 1537), 55 pp. November 2010. 191. Instruments to Measure Solar Ultraviolet Radiation Part 4: Array Spectroradiometers (lead author: G. Seckmeyer) (WMO TD

No. 1538), 43 pp. November 2010. 192. Guidelines for the Measurement of Atmospheric Carbon Monoxide (WMO TD No. 1551), 49 pp, July 2010. 193. Guidelines for Reporting Total Ozone Data in Near Real Time (WMO TD No. 1552), 19 pp, April 2011 (electronic version

only). 194. 15th WMO/IAEA Meeting of Experts on Carbon Dioxide, Other Greenhouse Gases and Related Tracers Measurement

Techniques (Jena, Germany, 7-10 September 2009) (WMO TD No. 1553). 330 pp, April 2011. 195. WMO/GAW Expert Workshop on Global Long-term Measurements of Nitrogen Oxides and Recommendations for GAW

Nitrogen Oxides Network (Hohenpeissenberg, Germany, 8-9 October 2009) (WMO TD No. 1570), 45 pp, February 2011.

24

196. Report of the First Session of the CAS JSC OPAG-EPAC and GAW 2009 Workshop (Geneva, Switzerland, 5-8 May 2009) (WMO TD No. 1577).

197. Addendum for the Period 2012 – 2015 to the WMO Global Atmosphere Watch (GAW) Strategic Plan 2008 – 2015, 57 pp, May 2011.

198. Data Quality Objectives (DQO) for Solar Ultraviolet Radiation Measurements (Part I). Addendum to WMO/GAW Report No.

146 - Quality Assurance in Monitoring Solar Ultraviolet Radiation: State of the Art. 199. Second Tropospheric Ozone Workshop. Tropospheric Ozone Changes: observations, state of understanding and model

performances (Météo France, Toulouse, France, 11-14 April 2011), 226 pp, September 2011. 200. WMO/GAW Standard Operating Procedures for In-Situ Measurements of Aerosol Mass Concentration, Light Scattering and

Light Absorption (Edited by John A. Ogren), 134 pp, October 2011   201. Quality Assurance and Quality Control for Ozonesonde Measurements in GAW (Prepared by Herman Smit and ASOPOS

Panel). 202. Workshop on Modelling and Observing the Impacts of Dust Transport/Deposition on Marine Productivity (Sliema, Malta, 7-9

March 2011), 50 pp, November 2011. 203. The Atmospheric Input of Chemicals to the Ocean. Rep. Stud. GESAMP No. 84/GAW Report No. 203. 69 pp.