A EUROPEAN AEROSOL PHENOMENOLOGY: TOTAL CARBON, ELEMENTAL CARBON AND ABSORPTION COEFFICIENT

1. A EUROPEAN AEROSOL PHENOMENOLOGY: TOTAL CARBON, ELEMENTAL CARBON ANDABSORPTION COEFFICIENT Fabrizia Cavalli and JP Putaud European Commission – DG Joint Research Centre M. Zanatta Laboratory of Glaciology and Geophysics of Environment, St Martin d'Hères Cedex Paul Scherrer Institute, Laboratory of Atmospheric Chemistry, Villigen

2. Motivation: • Carbonaceous aerosol, i.e. Elemental Carbon and co-emitted Organic compounds, are receiving increasing attention due to effects on human health and on global climate • DIRECTIVE 2008/50/EC on ambient air quality and cleaner air for Europe (21 May 2008) • CHAPTER II - SECTION 1 - Article 6 Assessment criteria • In addition to the assessments referred to in paragraphs 2, 3 and 4, measurements shall be made, at rural background locationsaway from significant sources of air pollution, for the purposes of providing, as a minimum, information on the total mass concentration and the chemical speciation concentrations of fine particulate matter (PM2.5) on an annual average basis … • ANNEX IV MEASUREMENTS AT RURAL BACKGROUND LOCATIONS IRRESPECTIVE OF CONCENTRATION • Substances - Measurement of PM2.5 must include at least the total mass concentration and concentrations of appropriate compounds to characterise its chemical composition. At least the list of chemical species given below shall be included: • ▪ Major inorganic ions: SO42–, Na+, NH4+, Ca2+, NO3–, K+, Cl–, Mg2+ • ▪ Organic Carbon (OC) and Elemental Carbon (EC) Absorption coefficient Concentration

3. CONTENT of the STUDY: ▪ Total Carbon, Elemental Carbon, PM mass, absorption coefficient in PM2.5 and in PM10 ▪ 10 EUROPEAN REGIONAL BACKGROUND SUPER-SITES, part of the EMEP measurement NETWORK ▪ 4 YEARS of data: 2008 – 2011 ASPVRETEN BIRKENES NORDIC VAVIHILL MELPITZ HARWELL KOSETICE CONTINENTAL PUY de DÔME HIGH ALTITUDE ISPRA MONTSENY MEDITERRANEAN FINOKALIA

4. UNIQUE STUDY: HIGHLY HARMONISED DATASET AT ALL SITES RESEARCH&DEVELOPMENT and INTEGRATION ACTIVITIES for ATMOSPHERIC MEASUREMENTS within EUSAAR and ACTRIS EU-Integrated Infrastructures Initiatives (2006 – on going) • COMMON STANDARDISED METHODOLOGY plus COMPARABILITY INFORMATION on: • SAMPLING of CARBONACEOUS AEROSOLS on filters (leaded by JRC) • MEASUREMENT of: • Total Carbon andElemental Carbon concentration (leaded by JRC) • Absorptioncoefficient

5. Teflon filters Quartz fiber filters Sampler 1 Sampler 3 Sampler 2 TDQ TQ Q 1.1- DATA HARMONISATION: SAMPLING of CARBONACEOUS AEROSOLS b- TESTS to assess SAMPLING ARTIFACT across the network, in winter and summer a- DEVELOPMENT of a STANDARD method and ADOPTION EUSAAR - ARTIFACT-FREE SAMPLING TRAIN Denuder efficiency from 40%-90% at different sites Sampling Head Denuder Carbon honeycomb monoliths Front filter • - HARMONISATION CORRECTIONS for positive artifact: • Maximum average correction -30% for TC • no information for 3 sites • - negative artifact not exacerbated by denuder: <5% Back-up filters

6. 1.2- DATA HARMONISATION: ANALYSIS OF Total, Organic and Elemental Carbon a- DEVELOPMENT of a STANDARD method and ADOPTION EUSAAR_2 protocol (Cavalli et al., amt 2010) for thermal-optical analysis officially adopted as standard method by EMEP b- EXERCISES to assess INTER-LABORATORY COMPARABILITY within the NETWORK Five inter-laboratory comparisons • - laboratory systematic BIASES and HARMONISATION FACTORS: • max average deviation for EC/TC of 20% among sites using EUSAAR_2 • TC and EC with protocols other than EUSAAR_2 at two sites: max average deviation on EC/TC of a factor 2.3

7. 1.3- DATA HARMONISATION: measurement of ABSORPTION COEFFICIENT • FILTER-BASED INSTRUMENTS : • MAAP: MULTI ANGLE ABSORPTION PHOTOMETER (4) • PSAP: PARTICLE SOOT ABSORPTION PHOTOMETER (2) • AE: AETHALOMETER (2) • a- ADOPTION of STANDARDISED DATA CORRECTION PROCEDURES: • MAAP: SHIFT OF THE OPERATIVE WAVELENGTH (MÜLLER et al., 2011) • PSAP: CORRECTION FOR RESPONSE TO ABSORPTION AND SCATTERING (BOND et al., 1999; OGREN, 2010) • AE: CORRECTION FOR MULTIPLE SCATTERING AND SHADOWING EFFECTS (WEINGARTNER et al., 2003) • - ADJUSTED OF ABSORPTION COEFFICIENT TO A COMMON WAVELENGTH 637 nm • with constant Absorption Ångstrom Exponent of 1 • b- WORKSHOPS to assess the INTER-INSTRUMENT COMPARABILITY within the NETWORK • - instrument systematic BIASES and HARMONISATION FACTORS: • HFMAAP= 1 HFPSAP= 0.96-1.03 HFAE= 1.6

8. 2.1 a,b RESULTS: HARMONISED ANNUAL AVERAGE of PM mass, Total Carbon and Elemental Carbon • PM10 Mass: SIGNIFICANT POSITIVE GRADIENT from N to S 6 μgm-3 (BIR) - 30 μgm-3 (ISP) Mass μg m-3 northwest south Elemental Carbon Total Carbon μg m-3 • PM10 Total Carbon and Elemental Carbon: • SIGNIFICANT POSITIVE GRADIENT from N to S • TC: 1 μgm-3(BIR) - 10 μgm-3 (ISP) • EC: 0.1 μgm-3(BIR) - 2 μgm-3 (ISP) PdD high altitude site – special case!

9. 2.1 c RESULTS: HARMONISED ANNUAL AVERAGE of Absorption coefficient Absorption coefficient Mm-1 • SIGNIFICANT POSITIVE GRADIENT from N to S: 0.8 Mm-1 (BIR) - 11 Mm-1 (ISP)

10. 2.2a RESULTS: HARMONISED ANNUAL AVERAGE of Total Carbon / Mass Ratio Total Carbon / Mass Least carbonaceous aerosol at the Mediterraneansites, i.e. Finokalia and Montseny: 0.11 - 0.14 Most carbonaceous aerosol in Ispra: 0.30 - 0.40 Forthe majority of the sites, fairly homogeneous Total Carbon / Massratio: 0.16 - 0.24

11. 2.2b RESULTS: HARMONISED ANNUAL AVERAGE of Elemental Carbon / TotalCarbon Ratio Elemental Carbon / Total Carbon Fairly homogeneous (Puy de Dôme excepted) Elemental Carbon / Total Carbon ratio: 0.12-0.23 Elemental Carbon / Total Carbonratioaffected by the proximity of emission sources

12. 2.2c RESULTS: HARMONISED ANNUAL AVERAGE of Absorption coefficient / ElementalCarbon, i.e. mass absorption cross section m2g-1 MAC m2 g-1 • Homogeneity in the mac values: 6. 6 m2 g-1(VHL) —16.1m2 g-1(PdD) • (pddand vhl have a poorer data coverage with less than 150 data points) • “European regional background” MAC = 10.8 ± 3.00

13. 2.3a RESULTS: HARMONISED SEASONAL AVERAGES of Total Carbon / Mass Ratio PM2.5 PM10 Total Carbon / Mass FALL FALL SPRING SUMMER WINTER SPRING SUMMER WINTER • season-specific sources of carbonaceous aerosol modulate • the seasonal cycle of Total Carbon / Mass ratio

14. 2.3a RESULTS: HARMONISED SEASONAL AVERAGES of Total Carbon / Mass Ratio PM2.5 PM10 Total Carbon / Mass FALL FALL SPRING SPRING SUMMER WINTER SUMMER WINTER WINTER FALL TC / Mass SUMMER TRAFFIC SPRING WOOD BURNING WOOD BURNING BIOGENIC AEROSOL • Carbonaceous aerosol contribution from traffic constant throughout the year • Mostcarbonaceous aerosol in winter-fall due to wood burning • Biogenic aerosol peaks in summer • Leastcarbonaceous aerosol in spring • Inverse cycle at finokalia due to agricultural waste burning and forest fires in spring and summer

15. 2.3b RESULTS: HARMONISED SEASONAL AVERAGES of Elemental Carbon / TotalCarbon Ratio PM2.5 PM10 Elemental Carbon / Total Carbon FALL FALL SPRING SUMMER SPRING WINTER SUMMER WINTER Elemental Carbon / Total Carbon ratio seasonal cycle: maximum in fall-winter and minimum in summer

16. 2.3b RESULTS: HARMONISED SEASONAL AVERAGES of Elemental Carbon / TotalCarbon Ratio PM2.5 PM10 Elemental Carbon / Total Carbon FALL FALL SPRING SUMMER SPRING WINTER SUMMER WINTER SUMMER SPRING WINTER FALL EC / TC BIOGENIC AEROSOL TRAFFIC WOOD BURNING WOOD BURNING • Remarks: • Less pronounced cycle at continental sites due to weaker biogenic sources/or stronger traffic source • at Finokalia: maxima in spring-summer due to fires • at Puy de Dôme: cycle determined mainly by the boundary layer dynamic

17. 2.3c RESULTS: HARMONISED SEASONAL AVERAGES of Absorption coefficient / ElementalCarbon, i.e. mass absorption cross section MAC m2 g-1 FALL SPRING SUMMER WINTER Mac seasonal cycle: - maximum in summer at the majority of sites - In correspondence to the minimum of the ec/tc ratio (i.e. maximum abundance of organic carbon) - This would indicate an amplification of ecabsorptivity by the thicker Organic Carbon coating

18. 3. CONCLUSIONS • Methodological: • Importance of common standardisedprocedures from sampling to data submission • This is a more efficient and accurate approach than applying a-posteriori correction factors • Periodical checks of comparability • Phenomenological • Highly integrated network and a bias-free dataset allow • understanding sources and transformation of aerosols • On a European regional background scale: • Clear positive spatial gradient – from N to S – for all extensive aerosol properties: • PM mass, Total Carbon & elemental Carbon and absorption coefficient • homogeneity for all intensive aerosol properties: • Total Carbon / Mass, Elemental Carbon / Total Carbon and MAC • Seasonality of intensive aerosol properties and sources: • Total Carbon / Mass: Maxima in fall-winter (wood burning) and in summer (biogenic aerosol) • Elemental Carbon / Total Carbon: Maximum in fall-winter and minimum in summer • Absorption coefficient / Elemental Carbon: Minimum in fall-winter and Maximum in Summer • Scientific publication (Cavalli et al., in preparation) Jrc expertise Project products Pilot experiment • International Programmes (emep and aquila) • European Technical Body for standards – CEN wg 35 – in support to EU-DIR implementation • International observations-models comparison initiatives - AeroCom