New course Atmospheric particulates part of Atmosfærisk Miljøkemi - PDF

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New course Atmospheric particulates part of Atmosfærisk Miljøkemi Merete Bilde og Ole John Nielsen C408 og C516 Thanks to Peter Wåhlin, Per Axel Clausen, Matthias Ketzel, Rainer

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New course Atmospheric particulates part of Atmosfærisk Miljøkemi Merete Bilde og Ole John Nielsen C408 og C516 Thanks to Peter Wåhlin, Per Axel Clausen, Matthias Ketzel, Rainer Vogt and Spyros Pandis for use of their material 11/11 Lecture 1 (OJN+MB) 11/11 Lecture 2 (OJN+MB) P-track, lab and roof 12/11 Lecture 3 (OJN+MB) 12/11 Lecture 4 (OJN+MB) 14/11 Problem solving 1a+b (OJN) 18/11 Lecture 5 (MB+OJN) 18/11 Lecture 6 (MB+OJN) 19/11 Lecture 7 (MB+OJN) 19/11 Lecture 8 (MB+OJN) 21/11 Problem solving 2a+b (MB) A set of exam problems Curriculum: Chapter 7 and 13 in Atmospheric Chemistry and Physics Citizens in X-city feel sick and think they have an excess mortality compared to other cities. They complain to the local EPA where you are the chairman. What do you do? Year X-city (17914) dead X-city Y-city (21618) dead Y-city Year X-city (17914) dead X-city Y-city (21618) dead Y-city 0 0 1, , , , , , , , , , , , , , , , , , , , , , , , , , , , ,865 1,000 0,950 0,900 0,850 Serie1 Serie2 0,800 0, Uncertainties? Rate Ratio 1,35 1,3 1,25 1,2 1,15 1,1 1, TSP Serie1 Rate Ratio 1,35 1,3 1,25 1,2 1,15 1,1 1,05 Serie Fine particles Danmarks Miljøundersøgelser PM 10 -monitors SM200: 24h-sampling at room temperature. Heating till 40 ºC during mass measurement (by beta-absorption). EU reference method? TEOM: Halfhour measurements using the Tapered-Element Oscillating Microbalance. Simultaneous sampling and mass measurements at 50 ºC. Danmarks Miljøundersøgelser Analysis of SM200 measurements in Jagtvej PM 10 (µgm -3 ) Average data for Jagtvej sorted after time of week Slope: 0.17±0.16 µgm -3 /ppb Interception: 22±4 µgm -3 Traffic (11 µgm -3 ) SM200 Workday Weekend Long range transport (22 µgm -3 ) [NO x ] (ppb) Danmarks Miljøundersøgelser Analysis of TEOM measurements in Jagtvej PM 10 (µgm -3 ) Average data for Jagtvej sorted after time of week Slope: 0.17±0.16 µgm -3 /ppb Interception: 22±4 µgm -3 Slope: 0.161±0.003 µgm -3 /ppb Interception: 11.4±0.2 µgm -3 SM200 TEOM Workday Weekend [NO x ] (ppb) What? What is an aerosol? Suspension/mixture of solid, liquid or mixed particles in a gas What is a particle? Cluster of molecules Size range? Upper and lower limits? nm-10µm ( g) Relative Size of Atmospheric Particles 0.1 nm 1 nm 10 nm 100 nm 1 µm m 10 µm m 100 µm..... Atoms Molecules Ultrafine Fine Coarse Clouds What? What is an aerosol? Suspension/mixture of solid, liquid or mixed particles in a gas What is a particle? Cluster of molecules Size range? Upper and lower limits? nm-10µm ( g) How many? Up to cm -3 How many 10nm particles to outweigh one 10µm particle? How many sources? Two different kinds? Primary and secondary sources. Relative Size of Atmospheric Particles Gas-Particle conversion Combustion, Vehicle-exhaust Mechanical processes: Sea salt, dust 0.1 nm 1 nm 10 nm 100 nm 1 µm m 10 µm m 100 µm Atoms Molecules..... Ultrafine Fine Coarse Clouds What? What is an aerosol? Suspension/mixture of solid, liquid or mixed particles in a gas What is a particle? Cluster of molecules Size range? Upper and lower limits? nm-10µm ( g) How many? Up to cm -3 How many 10nm particles to outweigh one 10µm particle? How many sources? Two different kinds? Primary and secondary sources What are they made of? Do they change? Requirements to describe an aerosol? Air Pollution in X/Y-City Requirements to describe an aerosol? Measure Particle Properties Physical Chemical Number Size Shape Volume nm all /Mass g Surface area Optical properties Composition Layers/Mix Changing No claim to completeness! Is it Difficult? YES! (many sources) Atmospheric Particles - Why are they important? Health Direct radiative forcing Indirect radiative forcing Usefull numbers all in W/m 2 S Solar constant (at 1 AU) 1360 S/4 Top of the atmosphere 340 (S/4)(1-a) Earth s albedo, a= % change in Earth s albedo 1 Effect of CO 2 since Modeled effect of doubling of CO 2 4 Radiative effects of clouds (cooling?) 20-30 The Global Mean Radiative Forcing of the Climate System for the Year 2000, Relative to 1750 Atmospheric Particles - Why are they important? Health Direct radiative forcing Indirect radiative forcing Influence on weather Visibility Participate in chemical reactions in the atmosphere (O 3 hole) Transport of nonvolatile material (Fe to the oceans) The most open research area in atmospheric science Positive effects Desirable Particles When particle properties known! Examples Coating surfaces with nanoparticles Nanostructures Particle engineering in chemical industry Inhalation of drugs & therapeutics previously had to be injected (e.g. insulin!) Concept Map - Atmospheric Particles - What and Why? Sources Primary - Secondary Size distributions Chem.Composition Shape Layers Phases Health Rf-direct Rf- Indirect Weather Visibility Het-Chem Transp (Fe) Important new research area Concept Map - Atmospheric Particles - What and Why? Sources Primary - Secondary Size distributions Chem.Composition Shape Layers Phases Health Rf-direct Rf- Indirect Weather Visibility Het-Chem Transp (Fe) Important new research area Instruments to Measure Particle Number Electron Microscopes (SEM, TEM) Offline only, not airborne Optical methods (LPC, OPC, Photometer) Electrical Methods (Aerosol EM) Only when charge known Condensation Technique (CPC) Today greatest variety: ultrafine, cleanroom, high-concentration, handheld Condensation Particle Counter (CPC) CPC principle (3 steps): Supersaturated vapor (1) condensed (2) on particle acting as nuclei, forming larger droplets Optics detects & counts (3) Absolute counter From to 3 µm CPC Technique: Pros & Cons Advantages Detect particles down to 2.6 nm! Single particle counting Real-time Extreme concentration accuracy Low background counts Disadvantage No size information Butanol? N (cm -3 ) CO (ppm) 0 Mo Tu We Th Fr Sa Su 0 Particles CO JGTV83_EXT (calc.) JGTV83_INT JGTV83_EXT (CPC) HCOE Particles (cm -3 ) Instruments to Measure Particle Size Electron microscopes (SEM, TEM) Optical counters (OPC) Aerodynamic methods Time-of-Flight particle sizers (Aerosizer, APS) Low-Pressure Impactors (Moudi, Berner, ELPI) Electrostatic methods Electrical mobility (EAA, EAS, DMPS, SMPS) Diffusion batteries Mobility Particle Sizers Family of instruments: (EAA), DMPS, SMPS Instrument Merete Bilde purchased recently A little more elaborate information Size range: to 1 µm Three main components: 1) Electrostatic Classifier 2) Choice of DMA 3) Choice of CPC Interconnecting Hardware and Software Electrostatic Classifier Principle In SMPS particle size Pre-impactor Neutralizer Charge equilibrium Differential Mobility Analyzer (DMA) Center rod (-), sheath air Attracts particles (+) Slit: classification Differential Mobility Analyzer Pictured: Nano-DMA MPEG video courtesy University of Duisburg dn/dlogdp 6,E+04 5,E+04 4,E+04 3,E+04 2,E+04 1,E+04 Jagtvej, Thursday August 10, 2000 Half-hour averages, KU DMA 0,E Dp, nm Serie1 Serie2 Serie3 Serie4 Serie5 Serie6 Serie7 Serie8 Serie9 Serie10 Serie11 Serie12 Serie13 Serie14 Jagtvej, Thursday August 10, 2000 One-hour averages, KU DMA dn/dlogdp Dp, nm Serie1 Serie2 Serie3 Serie4 Serie5 Serie6 Serie7 Vavihill Lille Valby HCØ Aqueous-phase chemistry SECONDARY POLLUTANTS Reactions Acid Rain ATMOSPHERIC AEROSOL Dispersion PRIMARY POLLUTANTS EMISSIONS Diameter (micrometers) Number (dn/dlogd p ), cm -3 x10 3 Aerosol Size Distribution Nucleation Mode Aitken Mode 0 Volume (dv/dlogd p ), µm 3 /cm Condensation Submode Accumulation Mode Droplet Submode Coarse Mode 0 Organic Atmospheric Aerosols What does the organic fraction consist of? EC (elemental carbon, black carbon, graphitic) - source? Organic Carbon (OC) - sources? How do you measure EC and OC? Measurement methods TOR: Thermal optical reflectance, TMO: Thermal Manganese Oxidation Organic Atmospheric Aerosols What is soot? EC+OC+. (C 8 H, 2 g cm -3 ) remarkably consistent - not a unique substance Soot formation C m H n + a O 2 2a CO + 0.5n H 2 + (m-2a) C s C m H n + (m+n/4) O 2 m CO 2 + n/2 H 2 O poorly understood depends on fuel and flame type Preliminary Fuel Comparison Smoke 6.0 Bosch Smoke Number Diesel DMM DME Brake Power - kw OC What does OC consist of? How do you find out? How much OC in different places? Marine 1 µg(c)/m 3 (80% from continental sources) Rural 3-5 µg(c)/m 3 Urban 4-20 µg(c)/m % PM 10 and PM 2.5 in more polluted areas Primary vs Secondary OC? How do you find out? How many sources of OC? (old overhead) Tracer compounds and models? (CMB) Ozone as indicator of SOA Production OC/EC Ratio (front quartz) Ozone OC/EC Ratio 15-Jul 16-Jul 17-Jul 18-Jul 19-Jul 20-Jul 21-Jul O 3 (ppb) OC/EC Ratio from measurements (July 2001) 10 8 OCpri= 1.7*EC+0.6 OC (µg/m 3 ) EC (µg/m 3 ) Denuded In-situ Analyzer (2-4 hrs samples) Formation of Secondary Organic Aerosol 1. Gas-Phase Chemistry High volatility products Reaction with OH, O 3, NO 3 Low volatility products Acids, aldehydes, ketones, organonitrates, etc. ~1000 compounds SOA Precursors Alkanes ( C7) Aromatics Olefins ( C6) Biogenics Dialkenes etc. ~100 compounds Emission of Precursor Volatile Organic Compounds Formation of Secondary Organic Aerosol 2. Partitioning Between Gas and PM High volatility products Reaction with OH, O 3, NO 3 Low volatility products Acids, aldehydes, ketones, organonitrates, etc. ~1000 compounds SOA Precursors Alkanes ( C7) Aromatics Olefins ( C6) Biogenics Dialkenes etc. ~100 compounds Emission of Precursor Volatile Organic Compounds Organic aerosol phase(s) Aqueous aerosol phase Inorganic aerosol components Formation of Secondary Organic Aerosol 3. Further Reactions High volatility products Reaction with OH, O 3, NO 3 Low volatility products Acids, aldehydes, ketones, organonitrates, etc. ~1000 compounds Gas-phase reactions Aqueous-phase reactions SOA Precursors Alkanes ( C7) Aromatics Olefins ( C6) Biogenics Dialkenes etc. ~100 compounds Emission of Precursor Volatile Organic Compounds Organic aerosol phase(s) Heterogeneous reactions Aqueous aerosol phase Inorganic aerosol components SOA Precursors Biogenics 16% Olefins 15% Alkanes 4% Biogenics 14% Alkanes 6% Olefins 7% Aromatics 65% Los Angeles Aromatics 73% Central CA Modeling results for South US, Germany, and Scandinavia suggest that the biogenic component may dominate the SOA composition in these heavily forested areas. The secondary organic aerosol formation potential of gasoline can be accounted for solely in terms of its aromatic fraction (Odum et al., 1997). Why are biogenic VOC s important? Emitted in very large quantities isoprene 500 Tg C/yr (no particles!) monoterpenes 100 Tg C/yr (How do you know?) Anthropogenic NMHC 100 Tg C/yr Important for budget of photochemical oxidants Photochemical products such as formic and acetic acid are mainly biogenic The fate of the major part of biogenic VOC s is more or less unknown Danish contributions (Odense and Valencia) Formation and Growth of Ultrafine PM July 2, 2001 Nucleation and Growth (August 11, 2001) Nucleation a few hours after sunrise SUNRISE HIGH SO2 Overview of Nucleation Events Occurring on 30-50% of study days Detailed analysis of 3 months (July, October, January) showed 42 days with nucleation bursts Correlated with low levels of preexisting aerosols and bright sunlight Spatial scale? Regional (100s of km), Urban (Pittsburgh) Local (near our sampling site) Chemistry? Initial nuclei Sulfuric acid/water Sulfuric acid/water/ammonia Low vapor pressure organics SOA Sources Difficult to explain SOA origin in Pittsburgh Using the biogenic tracers, one can account for only 3% of the estimated SOA No tracers for anthropogenic SOA were detected (too polar, very small concentrations) Urgent need for ambient measurements of SOA compounds Numerical model predictions are still uncertain by a factor of 2-3 (gas-phase chemistry, partitioning,heterogeneous chemistry, temperature and RH dependence) Despite the significant progress during the last 20 years SOA remains the least understood aerosol component Den organiske del af partikler består af 2 hovedkomponenter kaldet elemental carbon (EC) og organic carbon (OC). EC er grafitlignende 3 dimensionale gitre af kulstof med en lille mængde andre grundstoffer. EC har kun en kilde: direkte emission ved forbrænding. EC koncentrationer er µg m -3 (2-25%) (by) OC er alt resten tusindvis lavt-flygtige organiske forbindelse af mange forskellige typer. Der er to hovedkilder til OC: direkte emission ved forbrænding (primary OC) eller dannelse ved photooxidation af kulbrinter (secondary OC). OC koncentrationer er 4-20 µg m -3 (15-65%) (by) EC og OC kvantificeres ved hjælp af standardiserede metoder (appendix 13): thermal optical reflectance (TOR) eller thermal manganese oxidation (TMO). Soot er en blanding af EC og OC. Sod dannes ved al forbrænding af kulbrinter også når der er nok ilt/luft tilstede. Detaljerne er soddannelsen er ikke kendt. Ud over den fundamentale interesse i processerne er der er stor praktisk interesse i at kunne forhindre eller begrænse soddannelse specielt for diesel. Visse oxygenerede forbindelser f.eks. dimethylether (CH 3 OCH 3 ) og dimethoxymethan (CH 3 OCH 2 OCH 3 ) kan brænde som dieselbrændstoffer uden soddannelse. Der er en særlig dansk interesse, da det var en medarbejder hos Haldor Topsøe som DME s attraktive egenskaber. Forskning indenfor alternative sodbegrænsende brændstoffer foregår bl.a. hos Ford Motor Company. OC pri /EC forholdet kan bestemmes for individuelle kilder f.eks. forskellige former for motorkøretøjer (blyholdig benzin, blyfri benzin og forskellige former for diesel). Motorkøretøjers emission skal bestemmes ved hjælp af en såkaldt Federal Test Procedure (FTP, der er én i USA og en lidt anden i Europa). Man kan regne det forventede OC pri /EC forhold ud i et kildeområde ( i Los Angeles). Udfra EC kan man regne OC pri ud. Difference mellem det totale OC og OC pri er så OC sec. I LA er 32-74% af OC = OC sec. Hver enkelt kilde undersøges for OC pri og NMHC emissioner, der kan danne OC sec. Både primært og sekundært OC består af tusindvis forskellige kemiske forbindelser. Den kemiske sammensætning kan bruges til kildeopgørelser (Source apportionment). Der er meget få (hvis der overhovedet er nogen) 100% specifikke tracer-forbindelser. Aerosol Chemical Composition Sulfates Nitrates Ammonium Elemental Carbon Organic Carbon/material Crustal Species Sea Salt Hydrogen ions Water Different ambient aerosols 1. Urban Aerosol 2. Marine Aerosol 3. Rural Continental Aerosol 4. Remote Continental Aerosol 5. Free Tropospheric Aerosol 6. Polar Aerosol 7. Dessert Aerosol Characteristic Type Urban Urban Background Sources Distributions Conc (unit!) Modes Variations Content Other Many primary and secondary. Difficult, not many studies. Number dom 0.1um Marine Sea spray Wind dependence Rural Continental Remote Continental Free Tropospheric In/Above clouds Mixed natural and anthropogenic Pri: dust Sec: oxidationsprod. Transport and cloud processing None less than 0.01 um High ug/m3 2 i volume/mass Big Fine: sulfate, nitrate, organics. Coarse: Dust, salt, tire wear. TSP PM 10 PM 2.5 PM cm Wind Sea salt Important source of atomic Cl 20 ug/m3 2 at 0.02 um and mass at 7 um cm ug/m3 3? at 0.02, 0.1 and 2 um (?) Small 200 cm -3 2 at 0.01 and 0.25 um Polar Low 20 cm -3 Dessert (Sahara) Wind blown Sahara sand Haze - 200 cm -3 2 at 0.75 and 8 um Broad 3 (difficult to see from figure) 5-25 ug/m 3 No small particles left Small? Measured from airplanes and mountains Aged, haze in Feb-April Soil, crustal material Transport more than 5000 km Fine 1µm Coarse 1µm Sulfates YES YES, H 2 SO 4 +2NaCl - Na 2 SO 4 + 2HCl Nitrates YES NH 3 +HNO 3 YES, HNO 3 on NaCl - NaNO 3 +HCl Ammonium YES, HNO 3 +NH 3 Elemental Carbon YES Organic Carbon/material YES Secondary OC on aged partikler Crustal Species YES Sea Salt YES, H 2 SO 4 +2NaCl - Na 2 SO 4 + 2HCl Undetermined YES YES Solubility Largely soluble, hygroscopic Largely insoluble and non-hygroscopic Sources Combustion Gas-to-particle conversion Mechanical process: Resuspension, sea spray, wind blow dust,. Atmospheric Lifetime Days to weeks Minutes to days Travel Distance s km 10s km Size fractionation? Filters, impactors (Moudi, Berner), DMA (differential mobility analyzer), single particle MS Methods: Traditional, ion-chramatografi, MS, GC, GC-MS, LC-MS, PIXE (Proton Induced X-ray Emission, DMU), nothing in Denmark on the organic fraction Use of knowledge of chemical content: Sources apportionment H.C. Andersens Boulevard!
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