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.

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

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

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?

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

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)

ECN GRAEGOR System: Denuder & Steam Jet Aerosol Collector

MARGA Denuder & Steam Jet Aerosol Collector (SJAC)

MARGA Performance Parameters (1-hour sampling)

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

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

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

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 50-1000 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.

Example AMS Time Series

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

The AMS Continues to Improve

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

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

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

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 (50-800 nm) future: 0.3-3 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)

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

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