The Laboratory of Atmospheric Chemistry The Laboratory of Atmospheric Chemistry Aerosols and Climate Aerosols and Climate CO 2 and E Ecosystems t Aerosols NO x , VOC Ozone
Aerosols Definition: PM10 = Particles with aerodynamic diameter <10 µ m Examples: Examples: Ammonium sulfate: ca 0 1 µ m Ammonium sulfate: ca. 0.1 µ m Diesel soot: ca. 0.1 µ m Pollen: 10 - 100 µ m Sea salt: 0.2 - 10 µ m Mineral dust: 0.2 - 10 µ m
How big are aerosol particles? Size relationships x 20’000 x 20’000 Diesel soot Pin head Hot air balloon 100 Nanometer (nm) ( ) 2’000’000 nanometer (nm) = = = 40’000’000 micrometer ( µ m) 2’000 micrometer ( µ m) 0.1 micrometer ( µ m) = = = 40’000 millimeter (mm) 2 Millimeter (mm) 0.0001 millimeter (mm) = 40 Meter (m) 40 Meter (m) In one cubiccentimeter of air: typically 10‘000 particles
Aerosols Aerosols Aerosols Aerosols • Primary and secondary particles and size distributions • Instrumentation • Climate • Health • Source identification
IPCC, 2001 Primary particle emissions in 2000 (Tg yr -1 )
Formation of secondary aerosol • Sulfate, homogeneous reaction: SO 2 + •OH + M → HO • SO 2 + M HO • SO 2 + O 2 + M → HOO• + SO 3 + M SO 3 + H 2 O → H 2 SO 4 • • Sulfate heterogeneous reaction: Sulfate, heterogeneous reaction: SO 2 (g) ↔ SO 2 (aq) - (aq) + H 3 O + (aq) SO 2 (aq) + H 2 O ↔ HSO 3 Oxidation with H 2 O 2 , Ozon, NO 2 , … • Nitrate, homogeneous reaction : NO 2 + •OH → HNO 3 NO 2 + OH → HNO 3 NH 3 (g) + HNO 3 (g) ↔ NH 4 NO 3 (s) • Nitrate, heterogeneous reaction : NO 2 + O 3 → NO 3 (g) + O 2 NO O NO ( ) O NO 3 (g) + NO 2 + M → N 2 O 5 (g) + M N 2 O 5 (g) + H 2 O (aq) → 2 HNO 3 (aq) • Organics: VOC + OH, O 3 , … � SOA (secondary organic aerosol)
IPCC, 2001 Source strengths of sulfate and organic carbon (kg m -2 hr -1 )
IPCC, 2001 mineral dust and sea salt (kg m -2 hr -1 ) Source strengths of black carbon,
Size distributions of aerosol particles
Aerosol Size Distribution 40 x10 3 Nucleation Mode Mode gD p ), cm -3 x 30 Number 20 N (dN/dlog Aitken 10 Mode 0 m 3 /cm 3 40 Droplet dlogD p ), µ m Accumulation Acc m lation Submode Submode Volume 30 Mode Coarse Mode 20 Condensation Submode (dV/d 10 0 0.01 0.1 1 10 Diameter (micrometers)
Traffic emissions: Influence of dilution temperature 1.0E+10 Tair=15C Tair=25C 1.0E+09 Tair=35C Tair=42.5C ) m 3 ogDp (#/cm 1.0E+08 1 0E+07 1.0E+07 Dl DN/ 1 0E+06 1.0E+06 1 10 100 1000 Dp ( nm) Kittelson et al. (2000)
Size distribution in and around Zürich (day, night): ( y, g ) smallest particles are 10 times more abundant in the city compared to the country side and 100 smallest particles are 10 times more abundant in the city compared to the country side and 100 times more abundant duirng the day than in the night times more abundant duirng the day than in the night 6 10 5 10 4 4 10 -3 ) (cm 3 10 N/d(logD) 2 10 1 1 10 10 dN Urban Area: Rural Region: (Downtown Z ь rich) (Z ь rcher Oberland) 0 10 Day (SMPS) Day (SMPS) Night (SMPS) Night (SMPS) -1 10 Day (OPC) Day (OPC) Night (OPC) Night (OPC) -2 10 10 10 100 1000 10000 10 100 1000 10000 Dp (nm) Bukowiecki et al., 2002
S. Pandis Nucleation and Growth in Pittsburgh (August 11 2001) (August 11, 2001)
Baltensperger et al., 2002 Evidence for primary and secondary particle formation Size distributions in Milan: Time
Secondary organic aerosol production Secondary organic aerosol production
Terminology: Terminology: Primary versus secondary • Primary particles: directly emitted to the atmosphere • • Secondary particles: formed in the atmosphere by condensation Secondary particles: formed in the atmosphere by condensation (nucleation and growth) after chemical transformation • How about oxidized primary particles ? � aged primary (not secondary as Fuzzi et al. 2006 suggested) • How about primary particles that evaporate on dilution and condense after oxidation (Robinson et al., 2007) ? � secondary
Measurement Techniques Measurement Techniques • Number • Number size distribution • Mass • Optical properties • Aerosol composition (off-line / on-line)
Condensation Particle Counter (CPC) ( ) Example: TSI CPC 3010 Lowest detectable diameter: D = 10 nm Lowest detectable diameter: D = 10 nm Maximum particle concentration: 10 4 cm -3
Measuring the electrical mobility with a Differential Mobility Analyzers (DMA) Measurable sizes: D =3-150 nm or 20-900 nm A scan is possible within 60-300 seconds A scan is possible within 60 300 seconds Principle: • Defined electrical charging of the particles with radiocative source Defined electrical charging of the particles with radiocative source • The aerosol flows laminarily through cylindric condensator • An electrical field force the particles depending on their electrical mobility to An electrical field force the particles depending on their electrical mobility to move toward the inner electrode. • Particles of a specific mobility ( b=v p /E ) are sucked through a gap at the inner electrode and are detected (typically by a CPC) afterwards.
F Fast Analyzers: t A l • EEPS Engine Exhaust Particle Spectrometer. Scan time typ. 2 sec. • FPS • FPS Fast Particle Spectrometer Fast Particle Spectrometer (similar to EEPS) • FMPS Fast Mobility Particle Sizer (ambient air version of EEPS) Engine Exhaust Particle Sizer Spectrometer (EEPS, TSI) Fast Particle Spectrometer (DMS500, Cambustion)
Aerodynamic particle sizer
Mobile laboratory The PSI mobile laboratory CPC CPC FMPS MAAP AMS CO2 CO2
Aerosol size distribution (5.6-560 nm) in an Alpine valley 6 6 5x10 10 Highway Highway 9 80x10 Village Village 4 m -3 cm -3 # cm -3 60 dV/dlogdp/ nm dN/dlogdp / # 3 40 2 20 1 0 0 6 7 8 9 2 3 4 5 6 7 8 9 2 3 6 7 8 9 2 3 4 5 6 7 8 9 2 3 10 100 Alpine Valley Alpine Valley 10 100 d dp / nm / dp / nm Riviera 2005 Winter • Consistent picture : Nanoparticle concentrations <30 Consistent picture : Nanoparticle concentrations 30 nanometers very high on highway • In villages : much lower nanoparticle concentrations, in case of high wood burning contribution higher volume concentration high wood burning contribution, higher volume concentration
Particulate mass Particulate mass • Filters and gravimetric analysis • On-line : e.g. Betameters, TEOM O li B t t TEOM Tapered element oscillating microbalance (TEOM)
Optical instruments e.g. light absorption by aethalomete − ⋅ = b x I I e abs “Lambert-Beer’s Law” 0 I 0 ⎛ ⎛ ⎞ ⎞ ⎛ ⎛ 0 ⎞ ⎞ I I I I ⎜ ⎜ = × = × ⎜ ⎜ 0 r “Optical attenuation” ATN 100 ln 100 ln ⎜ ⎟ ⎝ ⎠ ⎝ ⎠ I I s Aerosol particles For the time interval ∆ t=t 2 -t 1 : x ⎛ ⎞ ⎛ ⎞ I ( t ) I ( t ) ⎜ ⎟ ⎜ ⎟ ∆ = − r 2 r 1 Quartz filter ATN ln ln ⎜ ⎟ ⎜ ⎟ ⎝ ⎝ ⎠ ⎠ ⎝ ⎝ ⎠ ⎠ I ( ( t ) ) I ( ( t ) ) s s 2 2 s s 1 1 S S I I R R The attenuation coefficient (filtered aerosol) The attenuation coefficient (filtered aerosol) The absorption coefficient (airborne aerosol) The absorption coefficient (airborne aerosol) ∆ A ATN = b ATN b abs ∆ Q t Correct ion needed, e. g. • Weingart ner et al. , 2003 • Arnot t et al. , 2005
The absorption exponent α Absorption exponent α : a measure 12.0 b abs ∝ λ −α of the spectral variation in aerosol light absorption 10.0 m) b abs (950nm Example power law fit ( λ -2.0 ) 8.0 Wood burning a λ -1.8 to -2.2 g 6.0 6 0 b abs ( λ ) / Traffic, diesel soot a,b λ -1.0 to -1.1 4.0 a Kirchstetter et al . 2004 2.0 b Schnaiter et al. 2003 & 2005 0.0 350 350 450 450 550 550 650 650 750 750 850 850 950 950 λ [nm] Enhanced UV- absorpt ion due t o t he presence of wood smoke Enhanced UV absorpt on due t o t he presence of wood smoke
Aerosol Chemical Analysis Online / Direct Sampling Offline: Part 2 Offline: Part 1 Extraction Interface Chemical Chemical Analyzer Analyzer Analyzer Data Data Data Data SO 4 = 7.2 µ g m -3 2- Pump 2- SO 4 Time Slide courtesy of Jose-Luis Jimenez
Examples of off-line analysis • Ion chromatography (NH 4 , NO 3 , SO 4 , organic acids) • X-ray fluorescence, Particle Induced x-ray emission (PIXE) Inter Coupled Plasma mass spectrometry (ICP (PIXE), Inter Coupled Plasma mass spectrometry (ICP- MS), Neutron activation, Atomic Asorption Spectroscopy (AAS) (elemental analysis: K, S, Pb, Zn, ..) (AAS) (elemental analysis: K, S, Pb, Zn, ..) • GC- / LC-MS (organic compounds: e g marker GC / LC MS (organic compounds: e.g. marker compounds hopanes, levoglucosan,) • IR / UV / proton-NMR- spectroscopy : functional groups • Mass spectrometry in general : isotope analysis, oligomers and more
On Line Analysis On-Line Analysis • Semi-online: EC-OC (separation of black/elemental carbon from organic carbon) b f i b ) Miyazaki et al. , JGR, 2007
On line analysis On-line analysis • ATOF-MS • Aerodyne Aerosol mass spectrometer • ..
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