1. Experience from the EMEP VOC measurements
EMEP TFMM Workshop Oslo November 2004
Sverre Solberg
NILU/EMEP-CCC

2. EMEP VOC measurements VOC measured regularly since 1992/-93
5-15 monitoring sites depending on the year

3. The objectives of the VOC monitoring
Establish the ambient concentration level
Compliance monitoring
Support the modelling activity
After 10(+) years:
Is the quality/precision of the data sufficient?
What can be said about compliance/trends?
What is the value for the modelling?

4. EMEP VOC measurements sampling and analyses
Measurements twice pr week
Hydrocarbons
spot samples in canisters sampled around noon
Analysed by GC/FID
C2 – C7 compounds detected (method developed for C2-C5 compounds)
Detection limit around 10 ppt(v)
Carbonyls
8h samples in DNPH adsorption tubes
Analysed by HPLC/UV

5. QA/QC for VOC monitoring
Procedures for sampling/analyses etc given by the EMEP manual
But no DQOs specified yet
Manual inspection of data and detection of outliers by local lab and CCC
Intercomparisons/parallel studies
Audits from CCC (to Germany and Spain until now, more to come...)
Close collaboration between CCC and national labs in the beginning (education, training courses, visits from CCC to all labs)

6. EU-project AMOHA intercomparison study of NMHC

7. AMOHA (contd.)

8. Parallel carbonyl measurements, France
2 ½ years of parallel anlyses of carbonyls at FR08, Donon.
Formaldehyde, acetaldehyde, acetone:
High correlation, but bias (FR02 < NILU)

9. Parallel carbonyl measurements, France
Other carbonyls:
Spikes more frequent
Lower correlation
Different blank values/detection limits

10. Parallel carbonyl measurements, France
”Tracers of isoprene” (MVK and MACR) + tracers of aromatics (glyoxal)
Very poor agreement
Values close to detection
Any value for modeling?
Either improve analyses or leave out?

11. Parallel carbonyl measurements, Germany
UBA reports formaldehyde, acetaldehyde and acetone.
High correlation, but bias (UBA > NILU)
Acetone problem solved in Very good agreement after that. 

12. Trends in VOC emissions
Nearly constant until 1990
36% reduction from1990 to 2002 according to official data

13. Trends in measured VOC Waldhof 1992-2002
Decline in winter median concentrations for all components
Strongest decline for iso-alkanes and benzene
Level off last years?
Varying meteorology  Modelling of NMHC needed to draw conclusions!

14. Trends in measured VOC, Kosetice 1992-2002
Less clear trends in measured winter medians
Increased winter medians last years  due to meteorological variations?

15. Trends in measured VOC (UK)
UK (sub)urban VOC monitoring network indicate marked reductions during 

16. Measured and modelled formaldehyde

17. Measured and modelled ethene

18. Measured and modelled ethene

19. Measured and modelled isoprene

20. Do we measure the right VOCs?
Derwent et al. (2003) ethanol and trimethylbenzenes important ozone precursors not measured today.
Significant fraction of VOC emitted as C6-C12 not measured today.

21. Conclusions Are the quality/precision of the data sufficient?
Hydrocarbons:
Very good agreement for many NMHC when using the same NPL standard for calibration.
Large differences seen for labs using other procedures/standards for calibration
NPL standard should be used.
Carbonyls:
High correlation but bias for formaldehyde, acetaldehyde, acetone.  Intercomparisons recommended
Variable agreement for other carbonyls. Procedures should be re-evaluated. Further audits needed.
DQOs should be specified.
Metadata for techn. procedures should be reported together with the data

22. Conclusions (contd.) What can be said about compliance/trends?
Long-term VOC measurements do indicate reduced general concentrations, but:
Year-to-year variations in meteorology  Compliance monitoring is (almost) impossible without supporting modelling
Modelling of individual NMHC species should be done to strengthen the basis for drawing conclusions

23. Conclusions (contd.) What is the value for the modelling?
Agreement with winter episodes of hydrocarbons
confidence in emission pattern in general
Good agreement for isoprene at some sites (in spite of short lifetime etc)
 confidence to emission algorithm for isoprene
Good agreement for formaldehyde
 confidence to photochemical formulation in the EMEP chemistry
Discrepancies could be used for model improvement
Summer peak of formaldehyde at Utø observed, not modelled
Use differences in VOC speciation for different transport directions to investigate differences in VOC emission speciations