Seasonal perspectives of the Oxidation State and Sources of OA in Cape Corsica

Transcription

1 Seasonal perspectives of the Oxidation State and Sources of OA in Cape Corsica First results of 15-month continuous observations with ACSM J. Sciare (1), J. Nicolas (1), J.-E. Petit (1,2), F. Dulac (1), D. Lambert (3) and co-workers (1) LSCE, Gif/Yvette, France (2) INERIS, Verneuil-en-Halatte, France (3) LA, Toulouse, France

2 The Cape Corsica monitoring station. 6km 2.5km 4.5km S N

3 Oxidation State of OA/ First results from long term ACSM observations June 212 August 213 f44 (%) = m/z 44 / total Org signal Triangle plot from Ng et al. (ACP, 21) Mostly CO 2 + (acid and/or acid derived ester species) f43 (%) = m/z 43 / total Org signal Mostly C 2 H 3 O + for OOA (non acid oygenates for OOA) AGEING Mostly C 3 H 7 + for HOA

4 f43 f44.5 Comparison of f43 and f44 between ACSM and HR-ToF-AMS Cape Corsica (11-21 July 213) f44 (HR-Tof-AMS) f44 (ACMS).3.1 f44 (ACSM) = 45±29 f44 (HR-ToF-AMS) = 58±33 About 4% difference f43 (HR-ToF-AMS) f43 (ACSM) f43 (ACSM) = 41±6 f43 (HR-ToF-AMS) = 41±12 11/7 13/7 15/7 17/7 19/7 21/7 HR-ToF-AMS data courtesy of N. Marchand and L. Dewit (LCP); ANR-SAFMED project

5 f44 juin-12 juil.-12 août-12 sept.-12 oct.-12 nov.-12 déc.-12 janv.-13 févr.-13 mars-13 avr.-13 mai-13 juin-13 juil.-13 août-13 Seasonal variation of f44 (June 212 August 213).35.3 SUMMER 212 SUMMER f44 (Crete Isl.) Triangle plot from Ng et al. (ACP, 21) DURING SUMMER (June to Aug.): Very High values during summer (among the highest reported in litterature for AMS data). Probably no significant amount of SV-OOA Poor variability (mostly between &.3) / OA oxidation state is likely to be quite similar (although OA is more variable) DURING WINTER (From Nov. To Feb.) : Lower f44 but still in the range of.15 (still important oxidation, LV-OOA) Very High variability suggesting fast transport of poorly oxydized OA

6 f44 6/212 7/212 8/212 9/212 1/212 11/212 12/212 1/213 2/213 3/213 4/213 5/213 6/213 7/213 8/213 Comparison between f44 and oxalate Oxalate, µg/m OC, µgc/m SUMMER Oxalate OC [Oxalate]/[OC] 7% during summer [Oxalate]/[OC] 2% during winter Some similarities between f44 seasonal pattern and the fraction of oxalate in OA

7 f43 juin-12 juil.-12 août-12 sept.-12 oct.-12 nov.-12 déc.-12 janv.-13 févr.-13 mars-13 avr.-13 mai-13 juin-13 juil.-13 août-13 Seasonal variation of f43 (June 212 August 213).15 SUMMER 212 SUMMER f43 (Crete Isl.) Triangle plot from Ng et al. (ACP, 21) DURING SUMMER (June to Aug.): Very Low values during summer (among the lowest reported in litterature for AMS data). Probably no significant amount of SV-OOA Poor variability (mostly between 3 &.7) / OA oxidation state is likely to be quite similar (although OA is more variable) DURING WINTER (From Nov. To Feb.) : Higher f43 but in the range of.5-.7 (still important oxidation, LV-OOA) Very High variability suggesting fast transport of poorly oxydized OA

8 H/C H/C versus O/C: Fragmention of OA? Aiken et al. (Environ. Sci. Technol., 28) O/C = 382 xf Ng et al. (Atmos. Chem. Phys., 211) H/C = xf xf43² O/C Van Krevelen Triangle plot from Ng et al. (ACP, 211) Already highly oxidized OA during winter (carboxylic acids and/or alcohol+carbonyl) towards fragmentation with carboxylic acides during summer

9 : 3: 6: 9: 12: 15: 18: 21: : f43 Solar radiation, W/m² f44 Solar radiation, W/m² Diurnal variations of f43 & f f 44 (Acid OOA) : LT (morning) 21: LT (evening) f 43 (Non-Acid OOA) Photochemically-induced formation/destruction of non-acid OOA (f 43 ) Photochemically-induced formation of acid OOA (f 44 ). Possibly with fragmentation However, Diurnal variability remain rather small ( 8% amplitude of f44; 4% amplitude of f43)

10 Source apportionment of OA/ First results from long term ACSM observations June 212 August 213 PMF with 2 & 3 factors ME-2 with 2, 3, 4 factors Fix factors = HOA, MSA Comparison

11 Relative Intensity Results from PMF (2 factors) 14 months (june 212 Aug. 213) factor nb. 2, iteration nb CH SUMMER 212 C 2 H variables 7 HOA OOA 8 factor 1 factor 2 factor 1 factor SUMMER 213 Relative contribution Similar spectra compared to PMF (2 factors) restricted to during summer 213 BUT Slightly lower contribution of m/z 15 & 29 for the summer period (compare to m/z 41 and 45) 2 conc. / g m Is it something from the real world? (or PMF artefact) 4 2 1/7/212 1/9/212 1/11/212 1/1/213 1/3/213 1/5/213 1/7/213 date

12 oxalate, µg/m3 Black Carbon, µgc/m3 1/6/13 11/6/13 Comparison with tracers Summer 213 (June August 213) 21/6/13 1/7/13 11/7/13 21/7/13 31/7/13 1/8/13 OOA, µg/m3 HOA, µg/m BC (Aethalometer, 7-L) HOA Oxalate (PILS-IC) OOA

13 Results from PMF (2 factors) Fraction of OOA to the total OA, % Fraction of HOA to the total OA, % With observable seasonal variation* *(results from 15-month observations).9.35 On a yearly average 2% HOA OOA.15 8%.3 OOA HOA Month of the Year OOA 7% of OA during winter months 85% of OA during summer months Fraction of OOA is high along the year; Even higher during summer

14 Relative Intensity Relative Intensity Comparison between PMF and ME-2 results PMF results 2 factors ME-2 results 2 factors factor nb. 2, iteration nb CH 3 + C 2 H variables HOA OOA 7 HOA OOA 8 factor 1 factor factor 1 1. factor 2.8 HOA_Paris, a-value = Relative contribution Relative contribution

15 m/z fraction HOA from HOA profile obtained in PMF Comparison between PMF and ME-2 results CH C 2 H y =.7631x R² = 525 m/z at 15 and 29 are the two major m/z that differs between the 2 mass spectra. Why? 2 HOA (ME-2, 2 factors, a=.1), µg/m m/z fraction from HOA profile used in ME y = 539x R² = HOA (PMF, 2 factors), µg/m 3 + ME-2 gives results [HOA] lower compare to PMF. Why? + Why we have different fragments? Could m/z at 15 and 29 explain this difference?

16 Relative Intensity ME-2 results 3 factors (1 profile fix = HOA) factor 1 factor 2 factor 3 HOA_Paris, a-value = Relative contribution + Factor 2??? + Same results obtained with PMF (3 factors) 2 factor nb. 3, iteration nb factor 1 factor 2 factor variables Could a part of Chloride be in assimilated as OA in m/z 37? conc. / g m Need for further investigation factor 1/7/212 nb. 3, iteration nb. 1/9/ /11/212 1/1/213 1/3/213 1/5/213 1/7/213 date

17 Conclusions + OA at Cape Corsica are most of the time highly oxidized (even during wintertime) as seen with high f44. They even look like more oxidised that what has been observed in E. Mediterranean (Crete Island). + Strong variability on OA oxidation state during winter (influence of fast transport with low processes). During summer, OA shows quite high and stable oxidation state (poor dependance of fast transport processes from EU). + The highly oxidation state of OA suggest that fragmentation may appear during summertime (heterogeneous processes) + PMF and ME-2 leads to different HOA concentration levels but are very consistent (need more investigation) Thanks for your attention