Carbonaceous aerosol: properties, sources and analytical methods Willy Maenhaut Ghent University (UGent), Department of Analytical Chemistry, Krijgslaan 281, S12, 9000 Gent, Belgium Carbonaceous Aerosol

Carbonaceous aerosols consist of organic matter (OM) and black or elemental carbon (BC/EC) BC and EC refer to roughly the same component, but term BC is used when the component is measured with an optical technique term EC used when the measurement is done with a thermal technique There may also be inorganic carbon [mostly carbonate carbon (CC)] present in the carbonaceous aerosol (especially in PM10 or TSP), but this will not be discussed Carbonaceous Aerosol

Organic matter (OM) and EC Primary sources of OM incomplete combustion of fossil fuels and biomass biological particles (PBAP) Secondary sources of OM (SOA) oxidation of volatile organic compounds (VOCs) of natural and anthropogenic origin EC / BC / soot primary aerosol component formed by incomplete combustion of fossil fuels (e.g., diesel) or of biomass Distinction between OM and EC not so straightforward more on this later there is also something like brown carbon (normally included with OM) Distinction between primary and secondary OM also less clear in recent years oxidized (aged) primary OM counted as secondary OM Carbonaceous Aerosol

Primary biological aerosol particles (PBAP) BACTERIA VIRUSES POLLEN FUNGI PLANT DEBRIS ALGAE Very large and likely short-lived PBAP have not traditionally been considered part of the OA budget, but this has been revised in recent years Not so much is known about emissions, processing, climate effects Carbonaceous Aerosol

Secondary organic aerosol (SOA) formation VOCs oxidized to less-volatile OC Partitioning to aerosol phase depends on vapor pressure high equilibrium vapor pressure  high tendency to stay in gas phase low equilibrium vapor pressure  partition to aerosol phase – non-volatiles Large organics (C> 6) tend to form aerosols while organics with C<6 do not Oligomerization on/in acidic aerosol Carbonaceous Aerosol

Biogenic hydrocarbons (BVOCs) Isoprene (C5H8) Monoterpenes (C10H16) Sesquiterpenes (C15H24) Anthropogenic SOA-precursors = aromatics (emissions are 10x smaller) Carbonaceous Aerosol

SOA production from BVOCs Biogenic VOC Emissions Oxidation Reactions (OH, O3, NO3) Nucleation (oxidation products) Growth Condensation on pre-existing aerosol Over 500 reactions to describe the formation of SOA precursors, ozone, and other photochemical pollutants [Griffin et al., 2002; Griffin et al., 2005; Chen and Griffin, 2005] Carbonaceous Aerosol

Formation of SOA from BVOCs Aldehydes RC(O)H Ketones RC(O)R Dicarbonyls RC(O)-C(O)R (C5H8) OH, O3 absorption into aerosol Monoterpenes (C10H16) oxidation Carboxylic acids RC(O)OH polymerization Carbonaceous Aerosol

Properties and environmental importance of carbonaceous aerosols have effects on human health (e.g., respiration, cardiovascular problems) scatter (OM) or absorb (BC) solar and IR radiation decrease visibility have effects on climate direct (the particles themselves) indirect (particles can act as CCN) water-soluble and/or hydrophilic OM can act as CCN and plays thus a role in cloud formation are involved in heterogeneous (and multi-phase) reactions … Carbonaceous Aerosol

Off-line chemical analysis of aerosol samples for carbonaceous components Aerosol samples collected with filter devices or cascade impactors at ground level (or towers) on land on ship platforms with aircraft platforms Carbonaceous Aerosol

OC/EC differentiation Pöschl, 2005 Carbonaceous Aerosol

OC/EC analysis by thermal-optical methods quartz fibre filter punch heated in quartz oven first phase (in pure He): OM compounds desorb -> CO2 -> CH4 second phase (in He/O2 mixture): EC and PC combusted -> CO2 -> CH4 transmission (TOT) or reflectance (TOR) of laser light through/by the filter punch continuously monitored Carbonaceous Aerosol

EC : area below the blue line after the OC/EC split point PC OC = OC1 + PC (with PC: pyrolytic carbon) : area below the blue line prior to the OC/EC split point (vertical brown line) EC : area below the blue line after the OC/EC split point Carbonaceous Aerosol

Full brown line : laser transmission (T) signal vertical full brown line : OC/EC split point for T Dashed purple line : laser reflectance (R) signal vertical dashed purple line : OC/EC split point for R Carbonaceous Aerosol

Analysis for water-soluble OC (WSOC) normally done with a total organic carbon (TOC) analyzer (part of) sample extracted with high-purity water filtered extract injected in TOC instrument 2-step procedure (2 different injections) water-soluble total carbon (WSTC) analysis: OM combusted to CO2 -> measured with NDIR detector water-soluble inorganic carbon (WSIC) analysis: filtered extract injected in reaction vessel, where the sample is acidified with phosphoric acid to obtain a pH <3; evolved CO2 measured with NDIR detector WSOC = WSTC – WSIC WSOC is a proxy for secondary OC; WIOC for primary OC Percentage of PM2.5 OC, which is WSOC urban sites: ~30-40% rural & forested sites: ~60% biomass burning OC: ~70% marine sites: ~30% Carbonaceous Aerosol

Analysis for water-soluble inorganic (and LMW organic) species by ion chromatography (IC) (part of) sample extracted with high-purity water; filtered extract injected separation with ion exchange column eluent for anions: hydroxide (OH-) gradient suppression of conductivity of the eluent conductivity of analyte ionic species measured Carbonaceous Aerosol

Isotopic analysis of carbonaceous aerosols e.g., 14C analysis with accelerator mass spectrometry (AMS) to differentiate between old (fossil fuel) and new (biogenic or biomass burning) carbon Carbonaceous Aerosol

Analysis of atmospheric aerosols for individual organic compounds ion chromatography (for C1 – C5 ionic species): aqueous extracts capillary electrophoresis Organic mass spectrometry Sample preparation sample extracted with organic solvent (e.g., methanol; CH2Cl2) extract pre-concentrated (evaporation) + re-dissolved derivatisation (methylation, trimethylsilylation) for gas chromatography (GC) Techniques gas chromatography / mass spectrometry (GC/MS) liquid chromatography / mass spectrometry (LC/MS) chromatographic separation with suitable column Carbonaceous Aerosol

LC/MS analysis of PM2.5 sample from Brasschaat TIC chromatogram [Gómez González, ACP, 2010] 10 20 30 40 50 60 70 Time (min) 10000 20000 30000 40000 50000 60000 Intensity 2.3 18.0 22.4 17.6 15.1 25.7 20.5 3.5 5.6 6.8 Carbonaceous Aerosol

Extent of OC explained by detailed organic analysis PM2.5 samples from 2007 summer campaign in Brasschaat } measured by IC Carbonaceous Aerosol

Extent of OC explained by detailed organic analysis PM10 samples from 1998 W & S campaigns in Ghent [Kubátová et al., JGR, 2002] samples analysed by GC/MS ~100 compounds identified and quantified identified compounds accounted for ~3.1% of the organic matter (OM) Carbonaceous Aerosol

On-line (in-situ) chemical analysis of atmospheric aerosols for carbonaceous components Carbonaceous Aerosol

Measurement of OC/EC (thermal) & BC (optical, PASS) OC/EC measurement semi-continuous OC-EC field analyzer (Sunset Lab) 45 min filtration followed by 15 min analysis analysis based on TOT (cfr. lab OC-EC analyzer) BC (LAC) measurement aethalometer (7-wavelength) aerosol collected on filter tape light absorption by the aerosol measured at 7 wavelengths multi-angle absorption photometer (MAAP) photo acoustic soot spectrometer (PASS) measures aerosol absorption at three wavelengths without first collecting particles on a filter Carbonaceous Aerosol

Measurement of BC with 7-wavelength aethalometer For traffic BC (diesel soot) Abs. coeff ~ λ-1 Åabs = 1 For BC from wood burning: brown carbon Åabs : 2 – 10 Åabs = 1 Carbonaceous Aerosol

Measurement of WSOC and water-soluble ionic species by particle-into-liquid sampler PILS-TOC-IC Timonen et al., AMT, 2010 Commercially available (IC): MARGA (Metrohm) Carbonaceous Aerosol

Measurement of levoglucosan with Particle-into-Liquid Sampler – High-Performance Anion Exchange Chromatography – Mass Spectrometry (PILS-HPAEC-MS) Saarnio et al., AMT, 2013 Carbonaceous Aerosol

Aerosol Mass Spectrometry (AMS) Several AMS instruments available from Aerodyne, including Aerosol Chemical Speciation Monitor (ACSM) High-resolution (HR) Time-of-Flight (TOF) AMS The instruments collect the PM1 aerosol In most instrument types only the non-refractory (NR) components of the aerosol are analysed NH4+, NO3-, SO42-, Cl- organic matter (OM) The contribution from the various aerosol types (and for the organic matter from HOA, OOA, BBOA, …) is obtained by PMF of the data set (time series of intensities of m/z ions) m/z marker ions for levoglucosan 60 (and 73) there are contributions from several other species Carbonaceous Aerosol

Measurement of non-refractory aerosol components with Aerodyne aerosol mass spectrometer (AMS) Canagaratna et al., 2007 Carbonaceous Aerosol

Organic aerosol components worldwide (PM1) Carbonaceous Aerosol Jimenez et al., Science, 2009

CO2+ Ng et al., ACP, 2010 mostly C2H3O+ Carbonaceous Aerosol

Off-line techniques vs On-line (real-time) techniques for assessing the contribution from biomass burning Off-line: sample collection in the field followed by chemical analysis in the lab collection with filters or cascade impactors analysis for inorganic and/or organic constituents On-line: in situ sampling and analysis (in real time) Aerosol Mass Spectrometry (AMS) Aethalometer Model (AeM) Particle-into-Liquid Sampler (PILS) and analysis for levoglucosan Carbonaceous Aerosol

Quantification of contribution from biomass burning with Off-line methods Chemical mass balance (CMB) method Multivariate methods, such as Positive Matrix Factorization (PMF) Using a single marker compound, typically levoglucosan Carbonaceous Aerosol

Quantification of contribution from biomass burning with Off-line methods - CMB Source profiles are needed Can be done on a single ambient aerosol sample Classical example: Schauer et al. [AE, 1996] measured: EC, Al, Si, and 101 organic species, of which there were 8 wood smoke markers source profiles for fireplace combustion of hardwood and softwood were combined to form an emissions-weighted average wood smoke source profile Average contribution (%) to the measured fine PM for 1982 Pasadena 9.6 Downtown LA 5.7 West LA 10.8 Rubidoux 1.3 Uncertainty of the method: about 20% (relative) Carbonaceous Aerosol

Quantification of contribution from biomass burning with Off-line methods - PMF NO source profiles needed Several species are needed A series of samples is needed (> 30) Example Gianini et al. [STE, 2013] Carbonaceous Aerosol

Gianini et al. [STE, 2013] – PMF and CMB Study at 4 Swiss sites Uncertainty: “the overall uncertainty of the applied source apportionment methods is unknown and their results should whenever possible be verified by comparison of different methods” Carbonaceous Aerosol

Quantification of contribution from biomass burning with Off-line methods, using a single marker compound, typically levoglucosan Concentration ratio of the PM mass to a marker compound in biomass smoke needs to be known Concentration of marker compound in each ambient sample then multiplied by that ratio implies that the marker compound in the ambient sample originates exclusively from biomass burning The concentration ratio of the PM mass to a marker compound in wood smoke depends on many parameters type of fuel burnt (hard wood / soft wood) type of wood stove or fireplace operating / burning conditions (flaming / smoldering) the PM size fraction Ratios used in studies for the VMM [Maenhaut et al., STE, 2012] PM10 mass / levoglucosan: 10.7 PM10 OC / levoglucosan: 5.6 estimated that the uncertainty that is associated with the wood smoke OC and PM mass contributions is around 30% Carbonaceous Aerosol

Methods for the determination of levoglucosan (in ACTRIS 2013 intercomparison) Using mass spectrometry (MS) for detection Gas Chromatography (GC)/MS Thermal Desorption (TD)-GC/MS High-Performance Liquid Chromatography (HPLC)-MS High-Performance Anion Exchange Chromatography (HPAEC)-MS Using pulsed amperometric detection (PAD) Ion Chromatography (IC)-PAD HPLC-PAD HPAEC-PAD Carbonaceous Aerosol

7-site study in Flanders in 2010-2011 (Chemkar-3) [Maenhaut et al 7-site study in Flanders in 2010-2011 (Chemkar-3) [Maenhaut et al., STE, 2012] In winter (blue) for 6 of the 7 sites: around 10% of PM10 mass, on average, from wood burning At Hamme in winter: 22% of PM10 mass, on average, from wood burning Carbonaceous Aerosol

On-line (real-time) techniques for assessing the contribution from biomass burning Aerosol Mass Spectrometry (AMS) Aethalometer Model (AeM) Particle-into-Liquid Sampler (PILS) and analysis for levoglucosan, e.g., Saarnio et al. [AMT, 2013] is less sensitive than Off-line methods Common features provide much better time resolution than Off-line methods assessing the contribution from biomass burning with AMS and AeM is more involved (and has thus a larger uncertainty) than in the case of Off-line methods Carbonaceous Aerosol

Example of AMS study: Elsasser et al. [ACP, 2012] Other sources than levoglucosan contribute to the intensity of the m/z = 60 ion Carbonaceous Aerosol

Aethalometer Model (AeM) Uses a 7-wavelength Aethalometer Introduced by Sandradewi et al. [EST, 2008] PMWB = c babs(490 nm)WB with absorption coefficient babs(490 nm)WB derived from the Aethalometer data for estimating c independent data are needed (e.g., 14C, AMS, HiVol filter data) c can be considered a site-specific constant Carbonaceous Aerosol

Example of AeM study: Favez et al. [ACP, 2010] Wintertime study in Grenoble; deployed HiVol filter, data analysed by CMB 7-wavelength Aethalometer, data analysed by AeM c-TOF AMS, data analysed by PMF Carbonaceous Aerosol

Some words on SOA from biomass burning It is increasingly realized in recent years that biomass burning gives also rise to SOA, e.g., Yee et al. [ACP, 2013] chamber study on SOA formation from biomass burning intermediates: phenol and methoxyphenols SOA compounds from wood or biomass burning in field samples methyl-nitrocatechols [Iinuma et al., EST, 2010] several nitro-aromatic compounds [Kitanovski et al., JChrA, 2012] several nitro-organic compounds [Kahnt et al., AE, 2013] their summed concentration at Hamme in winter was only 7% of the concentration of levoglucosan It is unclear how much SOA from biomass burning is included (if any) in the several apportionment or contribution calculations discussed in this presentation Carbonaceous Aerosol

Thank you Carbonaceous Aerosol

Carbonaceous Aerosol

Carbonaceous Aerosol

Wood burning vs. biomass burning and primary and secondary PM Biomass burning encompasses all burning of biogenic material from plants, such as trees (forests) grasses (savannas) agricultural residues chemically unconverted biomass fuel wood logs pellets other biofuel, such as charcoal Numerous gaseous and particle-phase species are emitted by biomass burning [Andreae and Merlet, GBC, 2001] some gases (both inorganic and organic) can be converted to particulate species and thus give rise to secondary inorganic aerosol (SIA) (e.g., SO42-, NH4+) secondary organic aerosol (SOA) In this presentation I will only deal with PM and particulate species (mostly primary) Carbonaceous Aerosol

Tracers and markers for smoke from biomass burning Inorganic tracers excess fine K [Andreae, Science, 1983] black carbon (BC) Zn NH4+, S, halogens (Cl, Br, I), Rb Organic tracers (incomplete combustion) retene (PAH) (conifer) [Ramdahl, Nature 1983] levoglucosan (cellulose) [Simoneit et al., AE, 1999] 49 other major tracers in Table 1 of review paper by Simoneit [Appl. Geochem., 2002] levoglucosan is the most abundant of the organic tracers retene is usually present in very low concentrations usually not included in measurements for PAHs there are about 7 times more WoS publications dealing with levoglucosan than with retene Carbonaceous Aerosol

Sources of levoglucosan in the atmosphere Simoneit et al., AE [1999] introduced levoglucosan as an indicator for wood burning levoglucosan (C6H10O5) arises from the pyrolysis of cellulose, the main building material of wood, at temperatures higher than 300 °C the cellulose content of wood is 40-50% Other sources of atmospheric levoglucosan besides wood burning burning of nearly all plants and of various forms of plant-derived material Levoglucosan / OC ratio (in %) for some types of biomass (domestic solid fuel) burnt [Kourtchev et al., STE, 2011] ash wood 24 peat 11 bituminous coal 1.2 smokeless coal 0.18 Carbonaceous Aerosol

Stability of levoglucosan in the atmosphere Various studies [Locker, PhD Thesis, 1988; Fraser and Lakshmanan, EST, 2000; Simoneit et al., EST, 2004] indicated that levoglucosan is quite stable in the atmosphere In recent years, however, Hoffmann et al. [EST, 2010] and Hennigan et al. [GRL, 2010] have published cautionary articles on the stability of levoglucosan, especially at high OH levels and under high RH conditions Maenhaut et al. [STE, 2012] stated that such conditions may be quite important for biomass burning particles in tropical areas and during long-range aerosol transport, but are expected to be of minor importance for Belgium, where the levoglucosan originates mainly from rather nearby sources Kessler et al. [EST, 2010] estimated that the heterogeneous oxidation lifetime of levoglucosan is 10.6 days which is near the estimated depositional lifetimes (∼5-12 days) Carbonaceous Aerosol

Aerosol Mass Spectrometry (AMS) Several AMS instruments available from Aerodyne, including Aerosol Chemical Speciation Monitor (ACSM) High-resolution (HR) Time-of-Flight (TOF) AMS The instruments collect the PM1 aerosol In most instrument types only the non-refractory components of the aerosol are analysed NH4+, NO3-, SO42-, Cl- organic matter (OM) The contribution from the various aerosol types (and for the organic matter from HOA, OOA, BBOA, …) is obtained by PMF of the data set (time series of intensities of m/z ions) m/z marker ions for levoglucosan 60 (and 73) there are contributions from several other species Carbonaceous Aerosol

Quantification of contribution from biomass burning with Off-line methods - PMF NO source profiles needed Several species are needed A series of samples is needed (> 30) Two recent examples Ducret-Stich et al. [ESPR, 2013] Gianini et al. [STE, 2013] Carbonaceous Aerosol

Ducret-Stich et al. [ESPR, 2013] - PMF Study in Swiss Alpine valley PMF on data set with OC, EC, and 20 elements % of PM10 mass attributed to biomass burning winter 26 summer 9 Uncertainty: ? Carbonaceous Aerosol

Gianini et al. [STE, 2013] – PMF and CMB Study at 4 Swiss sites Ratio (wood combustion PM10 mass) / levoglucosan, as derived from the annual average data from the 4 sites PMF 23 (15 – 29) CMB 15 (12 – 19) Carbonaceous Aerosol

Quantification of contribution from biomass burning with Off-line methods, using a single marker compound, typically levoglucosan Concentration ratio of the PM mass to a marker compound in biomass smoke needs to be known Concentration of marker compound in each ambient sample then multiplied by that ratio implies that the marker compound in the ambient sample originates exclusively from biomass burning The concentration ratio of the PM mass to a marker compound in wood smoke depends on many parameters type of fuel burnt (hard wood / soft wood) type of wood stove or fireplace operating / burning conditions (flaming / smoldering) the PM size fraction As a first (rough) guess: making use of emission data as given by Andreae and Merlet [GBC, 2001] ratio of TPM / levoglucosan for extratropical forest: 23 this ratio likely not applicable for wood burning in Flanders Carbonaceous Aerosol

Quantification using levoglucosan Ratios PM mass to levoglucosan for biomass smoke as used in Europe or deduced from European studies 8 (Baden-Wurttemberg <Bavaria) [Pfeffer et al., GRdL, 2013] 10.7 (Austria) [Schmidl et al., AE, 2008] 20 (Austria) [Schmidl et al., AE, 2011] 13 (North Rhine - Westphalia) [Pfeffer et al., GRdL, 2013] 15 (4 Swiss sites; using CMB) [Gianini et al., STE, 2013] 6-13 (Portugal; PM2.5) [Goncalves et al., AE, 2012] 37 (Swiss Alpine Valley) [Ducret-Stich et al., ESPR, 2013] 24 ± 9 (Finland) [Saarnio et al., BER, 2012] Ratios used in studies for the VMM [Maenhaut et al., STE, 2012] PM10 mass / levoglucosan: 10.7 PM10 OC / levoglucosan: 5.6 estimated that the uncertainty that is associated with the wood smoke OC and PM mass contributions is around 30% Carbonaceous Aerosol

Example of AMS study: Elsasser et al. [ACP, 2012] OCWB / levo = 7.0/1.4 = 5 compares well with the 5.6 used for the VMM studies Carbonaceous Aerosol

Summary and conclusions Use of the single marker species levoglucosan to assess the contribution from wood burning to the OC and PM10 mass in Flanders is justified other sources of levoglucosan than wood burning are expected to be quite small The issues with regard to the stability of levoglucosan in the atmosphere are probably not important in Flanders except maybe to some extent during summer The main uncertainty is in the (PM10 mass / levoglucosan) factor it may well be that a factor of 13 (or even 15) is more approriate than the factor of 10.7 used Secondary PM from biomass burning (both SIA and SOA) is likely underestimated when using levoglucosan only The contribution from biomass burning to the PM10 mass in Flanders may well be larger than was estimated in Maenhaut et al. [STE, 2012] the actual contribution could be up to 30% larger (at most 50%) Combining levoglucosan with other tracers and performing CMB and/or PMF may reduce the uncertainty that is associated with the assessment of the contribution from wood burning to the PM10 mass in Flanders Carbonaceous Aerosol

Thank you Carbonaceous Aerosol