1. Eiko Nemitz Centre for Ecology and Hydrology (CEH) Edinburgh, U.K.
(Semi-) Continuous Measurement Techniques for Reactive Aerosol Components and Gases
Eiko Nemitz
Centre for Ecology and Hydrology (CEH) Edinburgh, U.K.

2. Overview of level 2 & 3 measurement techniques
Manual Daily Denuder / Filter Pack speciation samplers with automated samplers (URG, R & P Speciation Sampler)
Semi-continuous Measurement (time resolution 1 hr or better)
Furnace/vapouriser & gas monitor
Wet chemistry based
Aerosol mass spectrometry

3. Reasons for Automated Semi-Continuous Measurements
High time resolution
Source apportionment
Validation of transport in models
Low detection limit
No need for sample handling  minimises contamination, maximises sensitivity
Size-resolution
Health impacts
Climate impacts

4. Key Challenges Suited to ambient monitoring
Artefact free separation of gas and aerosol phase
Avoid loss of (semi-)volatiles, e.g. NH4NO3
Reasonable cost (purchase & operation)
Cover full range of compounds?

5. Technique Instrument Aerosol components Gases
NO3-
NH4+
Na+, K+, Ca2+, Mg2+
OC/EC
SO2
NH3
HNO3
HCl
Compound specific (gas) monitors
Pulsed fluorescence
Various, e.g. Thermo 43CTL 
Vaporisation & SO2 measurement; Harvard Technique
R&P 8400S, Thermo 5020SPA a
Flash vaporisation & NOx measurement
R&P 8400N
Automated evolved gas analysis; non-disp. IR detector
SunSet Lab, R&P 5400, …
Chemical Ionisation Mass Spectrometery
Non-commercial
Tunable Diode laser Absorption Spectrometery (TDL-AS)
Aerodyne TDL; Campbell Scientific Gas Analyser; …
NOy (Converter and NO analyser)
Denuder difference
Molybdenum Converter difference
e.g. Search TRN
Photo-acoustic
e.g. Pranalytica Nitrolux-100
Mass spectrometry
Thermal vaporisation
Aerodyne Aerosol Mass Spectrometer b OC
Laser ablation
e.g. TSI ATOFMS
Not quantitative
Wet chemistry
AiRRmonia
denuder / ion membrane / conductivity
URG 9000 Ambient ion monitor
Droplet inertial impaction / IC
Georgia Tech PILS
(OC)
ECN MARGA
Denuder & droplet inertial impaction/IC
ECN GRAEGOR
ditto, 2 inlets
a) Suitable to PM2.5 only; b) non-refractory component of PM1 only

6. Award Winners at the 2005 Meeting of the American Association for Aerosol Research (AAAR), Atlanta
Kenneth T. Whitby Award (Outstanding Technical Contribution to Aerosol Science by Young Scientist): Rodney Weber, Georgia Tech, for the development of the Particle Into Liquid Sampler (PILS)
Benjamin Y.H. Liu Award (Outstanding Contribution to Aerosol Instrumentation and Experimental Techniques that Have Significantly Advanced the Science and Technology of Aerosols): Douglas Worsnop and John Jayne, Aerodyne Research Inc, for the development of the Aerosol Mass Spectrometer (AMS)

7. ECN GRAEGOR System: Denuder & Steam Jet Aerosol Collector

8. MARGA Denuder & Steam Jet Aerosol Collector (SJAC)

9. MARGA Performance Parameters (1-hour sampling)

10. GRAEGOR Example Time Series
Trebs et al., 2004; Amazonia

11. Use of SJAC to measure NO3- size-distribution without evaporation losses
Mention use for measurement of water-soluble organic carbon (already tested in European intercomparison) and black carbon (as colloidal suspension).
ten Brink et al., 2004

12. ECN plans
Use for water-soluble organic carbon (already demonstrated in European intercomparison)
Extension to black carbon (as colloidal solution)
Use in the National Climate Research Programme (Meteo-tower Cabauw, NL11) (hopefully becoming supersite)
From start: major ions
From year 2: BC
From year 3: OC

13. Aerodyne Aerosol Mass Spectrometer (AMS)
Particle Beam
Particle
Aerodynamic Sizing
Generation
Composition
Quadrupole
Mass Spectrometer
Chopper
Thermal Vaporization &
Electron Impact Ionization
TOF Region
Aerodynamic Lens
(2 Torr)
The particles enter the AMS and are focused by an aerodynamic lens into a tight beam (<1 mm diameter). In the size range nm we get 100% of the particles transmitted from the inlet to the detector.
The chopper wheel defines the beginning of a time-of-flight period. Smaller particles move faster, so when a packet travels from chopper to detector, the smallest ones arrive first.
The detector consists of a 600 degree C oven that flash vaporizes the particles. The oven is located inside the ionizer region of a quadrupole mass spectrometer. Most of the gas phase molecules are lost in the first chamber of the AMS, so what reaches the ionizer is almost exclusively material that was in the particle phase.
Can use single ion monitoring mode to get quantitative information about single particles, or scan the quadrupole to get complete MS of average particles.
Particle Inlet (1 atm)
Turbo Pump
Turbo Pump
Turbo Pump
Jayne et al., Aerosol Science and Technology 33:1-2(49-70), 2000.

14. Example AMS Time Series

16. AMS Lens Transmission Vacuum aerodynamic diameter: Dva = Da rp
Liu et al., 2004

17. The AMS Continues to Improve

18. Comparison of continuous measurement techniques – SO42-
Jimenez et al., 2002; Atlanta Supersite 1999

19. Comparison of continuous measurement techniques – NO3-
Jimenez et al., 2002; Atlanta Supersite 1999

20. More recent intercomparison: SO42-
Drewnick et al., 2003: PM2.5 Technology Assessment and Characterization Study—New York (PMTACS-NY)

21. Advantages / Disadvantages
Aerosol Mass Spectrometer
Reliable
Fast
Size-distribution
Including OC
Sensitive
Currently semi-quantitative
Non-refractory only (e.g. no NaCl, NaNO3-)
Limited size-range ( nm) future: mm
Size-distribution
Price
IC Based System (MARGA / GRAEGOR / PILS)
Labour intensive to run
Full size-range
Size-distribution
Including gases
Sensitive
Time resolution limited (30 or 60 min)
No size information
Price
Requires affinity / expertise with wet chemistry (labour intensive)

22. Application for flux measurements
GRAEGOR:
MARGA gradient analyser
Calculation of fluxes with the Aerodynamic Gradient Method
Use of common detector (IC, membrane) to achieve precision of < 3%.
AMS:
10 Hz mode recently implemented for eddy-covariance flux measurements

24. TRN Diagram
SEARCH