1. EMEPs experience Measurements of gas/particles with focus on nitrogen compounds
Wenche Aas
Status of EMEP measurements today
Field intercomparison
Campaign studies
Recommendations / Conclusions

2. Status of EMEP particle/gas measurement, 2002

3. Field intercomparison, sum NH4
Filterpack at both

4. Field intercomparison, sum NH4
Filterpack at both

5. Field intercomparison, NO3
NILU : Filterpack RIVM: PM10 sampler

6. Field intercomparison, sum NO3
CZ: HNO3 on NaCl impr filter; CCC: NaOH impr filter
Main error in HNO3. Field blanks problem ?

7. Field intercomparison, sum NH4
Problems with NH4NO3 contamination on Zeflour filter

8. NH4 at NO01 and NO08

9. NH4 at NO08

10. Gas to particle distribution for sNO3 and sNH4 from filterpack
Filterpack has proven to be reliable, easy to use
The artefact problem with filter packs is well known
Countries are encouraged to report both gas and particle data even when using filterpack

11. EMEP Denuder campaign, 1993
Particle/gas ratio varies a lot, but are usually above 1

12. Denuder campaign, sum red N

13. Denuder campaign, sum red N

14. Denuder campaign, sum NO3

15. Denuder camp., main findings:
Aerosol conc higher than gas concentration (some exceptions in summer and spring with high NH3)
Sum of SO4 and NO3 is always less than NH4 due to presence of other base cation (Na,Mg,Ca)
Not all NO3 as NH4NO3
Higher conc. than the diss. const of NH4NO3 would predict.
High diurnal variations
High NH3 conc when low HNO3 conc and vice versa
Mostly 1:1 comparing sumN for denuder and filterpack. Some deviations due to difference in cut off and instruments problems
Accurate denuder measurements require good training and experience

16. Nordic Field intercomparison
Very preliminary results
A PM10 - inlet has been modified to fit the filter pack.
Compared with ordinary filterpack
Funded by the Nordic council of Ministers
Differences in method:
Cut off
Conditioning before weighing

17. Nordic Field intercomparison

18. Nordic Field intercomparisonNa

19. Nordic field intercomparison
Sum HNO3+NO3
Sum NH3+NH4
NH4NO3 lost in Finnish PM10-filterpack (due to conditioning?)
Enhanced NH4, Na, Ca (NO3) at NO01 –why? Cut off??

20. Conclusions
Filterpack is robust method and easy to implement at new sites
Important to continue chemical speciation of the filterpack measurements for time trend studies.
Denuders requires good training and experience
Diurnal variations of the Gas-Particle distribution
The chemical speciation at size segregated samples is influenced of
Cut off (Coarse particles like NaNO3 may be lost)
Conditioning of filters Loss of NH4NO3 + other comp
 recommended to measure chem comp in filterpack in addition to e.g PM2.5
Filter type (quartz, teflon,cellulose)