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Indication of aerosol aging by Aethalometer optical absorption measurements Luka Drinovec 1, Griša Močnik 1, Irena Ježek 1, Jean-Eudes Petit 2,3, Jean.

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Presentation on theme: "Indication of aerosol aging by Aethalometer optical absorption measurements Luka Drinovec 1, Griša Močnik 1, Irena Ježek 1, Jean-Eudes Petit 2,3, Jean."— Presentation transcript:

1 Indication of aerosol aging by Aethalometer optical absorption measurements Luka Drinovec 1, Griša Močnik 1, Irena Ježek 1, Jean-Eudes Petit 2,3, Jean Sciare 2, Olivier Favez 3, Peter Zotter 4, Robert Wolf 4, André S.H. Prévôt 4, and Anthony D.A. Hansen 1,5 1. Aerosol d.o.o., Kamniška 41, SI-1000 Ljubljana, Slovenia 2. LSCE (CEA-CNRS-UVSQ), Orme des Merisiers, Gif-sur-Yvette, France; 3. INERIS, Verneuil-en-Halatte, France 4. Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland 5. Magee Scientific, 1916A M.L. King Jr. Way, Berkeley, CA 94704, USA Keywords: Aethalometer, source apportionment, ACSM, AMS, PSCF Contact author Presenting author ACCENT Symposium 2013, Urbino (Italy)

2 1. Introduction to BC measurements Sources - Combustion Effects of black carbon (BC): -Public health effects -Climate change How to reduce harmfull effects: -Indentify sources: traffic vs household heating -Indentify sources: local vs. regional d pp =20 nm Note change in scale d m =472 nm

3 3 Analytical Instrument : Aethalometer™ Collect sample continuously. Optical absorption ~ change in ATN. Measure optical absorption continuously : λ = 370 to 950 nm. Convert optical absorption to concentration of BC: BC (t) = b abs (t) /   - mass absorption crossection Real-time data: 1 s/1 minute ATN = ln (I 0 / I) Reference I 0 Sensing IBC Light Source Filter with Sample Light Detectors  b abs ~  ATN

4 Filter loading effect

5 BC vs ATN analysis – ambient data 5 Linear reduction of the instrumental response due to loading of the filter fiber. Jump at the tape advance (similar to Virkkula (2007) model). ambient data – no dependence of BC on ATN slope k variable: site, source, aerosol age, composition need to determine it dynamically – do not assume, rather measure BC (reported) = BC (zero loading) · { 1 - k · ATN } Large loading effect Small loading effect k=0.005 k=0.001

6 6 Dual spot Aethalometer – AE33 ATN 1 = ln (I 0 / I 1 ) Reference I 0 Sensing I1BC 1 Light Source Filter with Sample Light Detectors  Sensing I2 ATN 2 = ln (I 0 / I 2 ) Two parallel spots with different flow, therefore -> From different loading and attenuation loading compensation parameter k(λ) is calculated. Absorption data is compensated: b abs =b abs1 /(1-k*ATN 1 ) Payerne Winter 2013 BC 2

7 measure attenuation with the Aethalometer absorption coefficient - b abs for pure black carbon: b abs ~1/λ generalize Angstrom exponent: b abs ~1/λ α diesel: α ≈ 1 wood-smoke: α ≈ 2 and higher BC source apportionment 7 J. Sandradewi et al., A study of wood burning and traffic aerosols in an Alpine valley using a multi-wavelength Aethalometer, Atmospheric Environment (2008) 101–112

8 b(λ) = b wb (λ,wood) + b ff (λ,fossil) λ = 470 nm, 950 nm BC source apportionment 8 Sandradewi 2008 b i (470 nm) / b i (950 nm) = (470 nm / 950 nm) -  α = 1,0 ± 0,1 (fossil) Bond & Bergstrom 2004 α = 2,0 -0,5/+1,0 (wood) Kirchstetter 2004, Day 2006, Lewis 2008 BC wb BC ff

9 Measurement campaign EMEP: summer 2012 & winter 2013 Payerne site - Payerne aerological station - Rural background site - NW Swiss Paris site - SIRTA Atmospheric Research Observatory - located in a semi-urban environment - 25 km south of the Paris city center SiteCampaignBC (ng/m 3 )Biomass burning (%) PayerneWinter Summer ParisWinter Summer

10 Back trajectory analysis Back trajectory analysis using Potential Source Contribution Function (PSCF) Represents the probability that an air parcel may be responsible for high concentrations observed at the receptor site 72h back trajectories calculated with Hysplit v4.9 starting at 500m AGL An example: - PSCF analysis of BC - Paris winter 2013

11 Indentification of source locations - Angstrom exponent α obtained from AE33 spectral data - PSCF ( Back trajectory analysis using Potential Source Contribution Function ) α < 1.3 (traffic emissions)α > 1.3 (biomass burning) Paris – EMEP winter campaign 2013

12 Differentiation of fresh and aged aerosols Payerne summer Payerne winter Spectral fingerprint Summer and winter aerosols have different optical properties - k(λ) For background locations with aged aerosol loading effect at 880 nm (where BC is measured) is small!

13 Differentiation of fresh and aged aerosols k 880nm >0.002 (fresh aerosols) k 880nm <0.002 (aged aerosols) Paris – EMEP summer campaign Compensation parameter k 880nm obtained from AE33 - PSCF ( Back trajectory analysis using Potential Source Contribution Function )

14 Particle coating hypotesis Changes in k(λ) are caused by transparent coating SMPS: Fresh soot particle size = nm Aged particle size > 100 nm Particle diameter [nm]

15 Particle coating hypotesis Aerosol mass spectrometers: ACSM & AMS (Aerodyne) -> Aerosol chemical composition is obtained Coating factor (CF) – ratio between the sum of nonrefractory aerosol mass to BC: CF = (Org + NH 4 + SO 4 +NO 3 )/BC

16 Particle coating hypotesis – summer data AE33 compensation parameter ACSM Paris Summer2012 campaign Compensation parameter k 880nm and coating factor correlate well.

17 Summary Spectral absorption data from Aethalometer AE33 was used for BC source apportionment during EMEP campaigns in Paris (France) and Payerne (Switzerland). Back trajectory analysis using Potential Source Contribution Function (PSCF) was used to determine fossil fuel and biomass burning locations. PSCF: Aged aerosols have small k 880nm Aethalometer and ACSM/AMS measurements were used for calculation of the coating factor (CF): Big CF = Small k 880nm

18 Acknowledgements The work described herein was co-financed by the EUROSTARS grant E!4825 and JR- KROP grant Measurements performed at SIRTA (LSCE) were funded by CNRS, CEA, the EU-FP7( ) 'ATRIS' project under grant agreement n°262254, the Primequal Predit 'PREQUALIF' project (ADEME contract n°1132C0020), and the DIM R2DS (AAP 2010) 'PARTICUL'AIR' project. Measurements in Payerne were conducted by the Swiss Federal Office for the Environment (FOEN). Thank you for your attention!


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