Aqueous-Phase Chemistry in TM4-ECPL: SOA Formation via Cloud Processes Stelios Myriokefalitakis 1 Kostas Tsigaridis 2,3 Maria Kanakidou 1

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1 TM meeting, Heraklion, June 2010 Aqueous-Phase Chemistry in TM4-ECPL: SOA Formation via Cloud Processes Stelios Myriokefalitakis 1 Kostas Tsigaridis 2,3 Maria Kanakidou 1 1 Environmental Chemical Processes Laboratory, Department of Chemistry, University of Crete, Heraklion, Greece 2 NASA Goddard Institute for Space Studies, New York, NY 10025, USA 3 Center for Climate Systems Research, Columbia University, New York, NY 10025, USA stelios@chemistry.uoc.gr

2 Aerosols in the Atmosphere Organics Continental mid-latitudes Others 20% 50% Tropical forested areas 90% SOA is the major component of atmospheric PM 2.5 Kanakidou et al., 2005

3 Partitioning Theory -The Traditional view of SOA formation- OH NO 1-Σa i Carbonyls, Other gas phase species, CO O 3 VOC RO 2 NO 3 a i NO 2 Semi-volatile compounds (gas-phase)

4 Traditional view of SOA formation in Models fails to fully explain atmospheric observations Heald et al., 2005 Altitude (Κm) Models Obs. Models Obs. Models Obs. Volkamer et al., Obs. Models 5-10

5 Closing the Gap Between Models and Observations Low volatile products can be formed through aqueous reactions in clouds, fogs and wet aerosols (Blando and Turpin, 2000; Glencser and Varga, 2005; Ervens et al., 2004; Carlton et al., 2006; Volkamer et al., 2007, Lim et al., 2010, Ervens ad Volkamer, 2010) Water soluble gases react (e.g., via photochemistry, acid catalysis, and with inorganic constituents) in the aqueous phase forming organic acids, oligomers, and organosulfates (Carlton et al., 2006; Guzman et al., 2006; Perri et al., 2010) Lower volatility products are retained, at least in part, in the particle phase after water evaporation (Loeffler et al., 2006; El Haddad et al., 2009) SOA formed through atmospheric aqueous chemistry is a strong candidate for closing the gap between the measured organic aerosol and atmospheric model predictions in part because it is formed from different precursors

6 SOA formation through aqueous chemistry 1. VOC photo-oxidation in the gas-phase 2. Production of water-soluble organic compounds in the gas-phase (e.g. aldehydes) 3. Phase transfer between the gas and the aqueous phase 4. Production of low volatile compounds in the aqueous-phase (e.g. oxalic acid) 5. Upon cloud evaporation new organic particulate matter is formed OH VOC O 3 R-CHO Henry NO 3

7 Aqueous Phase Chemical Scheme in TM4-ECPL Reactions Α E/R (mol - lt 1 s -1 ) (K) H 2 O 2 + hv 2OH IUPAC SO 2 + O 3 SO = 4 wets.f90 SO 2 +H 2 O 2 SO = 4 wets.f90 OH + H 2 O 2 HO 2 + H 2 O 2.7E7 Carlton et al., 2007 HO 2 + HO 2 H 2 O 2 + O 2 8.3E5 Carlton et al., 2007 HOCHCH(OH) 2 + OH (OH) 2 CHCH(OH) 2 + HO 2 5.0E8 Lim et al., 2005 HOCHCH(OH) 2 + OH (OH) 2 CHCOOH + HO 2 + HO 2 + H 2 O 1.0E8 Lim et al., 2005 (OH) 2 CHCH(OH) 2 + OH (OH) 2 CHCOOH + HO 2 1.1E Lim et al., 2005 CH 3 COCH(OH) 2 + OH 0.86(OH) 2 CHCOOH HCOOH 7.0E8 Lim et al., 2005 (OH) 2 CHCOOH + OH (COOH) 2 + HO 2 + H 2 O 1.5E8 Lim et al., 2005 (COOH) 2 + 2OH 2CO 2 + 2H 2 O 4.7E7 Lim et al., 2005 Ref.

8 TM meeting, Heraklion, June 2010 The aqueous_phase module

9 Gas Phase HOCH 2 CHO (glyocolaldehyde) CHOCHO (glyoxal) CH 3 COCHO (methylglyoxal) HOCH 2 CH(OH) 2 (glycolaldehyde-hydrated) (OH) 2 CHCH(OH) 2 (glyoxal-hydrated) CH 3 COCH(OH) 2 (methylglyoxal-hydrated) Aqueous Phase (OH) 2 CHCOOH (glyoxylic acid-hydrated) HCOOH (formic acid) Phase transfer Reactions with. ΟΗ (COOH) 2 (oxalic acid) CO 2

10 Solubility of Gases in Cloud Droplets Only 9 species are allowed to be partitioned between gas and aqueous phase during a cloud period : GLY, GLYAL, MGLY, PRV, HCOOH, OXL and also H 2 O 2, HO 2, OH The equilibrium solubility of gases in water is given by the Henry s law constant H ( T ) = [ C] P g or H eff ( T ) Ki( T ) = H ( T ) 1 + [ H + ] Given the temperature (T), the effective Henry s law coefficient H eff and the liquid water content (LWC), it can be defined a phase ratio P x (Lelieveld and Crutzen, 1991; Dentener, PhD Thesis, 1993) Px = H eff * R* T * LWC P x gives the fraction of molecules in a certain, cloud containing volume of air, which resides in the aqueous phase

11 Solubility of Gases in Cloud Droplets The relationship between the chemical concentration of X species in the liquid phase, the gas-phase and the total concentration (X tot molecule cm -3 ) is calculated using the P x X = P X [ ]( aq) x[ ]( gas) [ X ]( aq) Px [ X ] total = 1 + P x [ X ]( gas) [ X ] = 1 + P total x The conditions of establish this equilibrium are not always fulfilled, and the transfer of species between gas and aqueous phases have to be defined as mass transport, limited by diffusion in the gas phase and across the interface.

12 Deviations from Henry s Law Modeled actual ratio : Equilibrium phase ratio : The modeled phase ratios agree within 1% for CH 2 O, H 2 O 2, CH 3 OO, CH 3 OOH, NO, and NO 2, and agree within 20%, for O 3, OH, HCOOH, and HO 2. Species that clearly are not in equilibrium are OH, HO 2, HNO 3, and NO 3. Barth et al., 2003

13 Exchange between the gas and the aqueous phase The rate of change of a chemical species due to mass transfer between gas and liquid phase can be defined as: r r k t = Dg υa Where: k t is the transfer coefficient (s -1 ) r is the droplet radius (cm) D g is the gas-phase diffusion coefficient (cm 2 s -1 ), calculated as = 1.9( MW ) υ is the mean molecular speed (cm s -1 ), calculated as D g 8kBTN a υ = π ( MW ) and α is the mass accommodation coefficient

14 Species Some aqueous_phase parameters H Κ dlnh k /d(1/t) (Μ atm -1 ) (K) (298K) SO Sander, 1999 NH Sander, Lim et al., 2005 H 2 O Sander, Lim et al., 2005 HO Sander, Lim et al., 2005 SO = NH HCOOH Sander, Lim et al., 2005 CH 2 (OH)CHO Lim et al., 2005 CHOCHO Sander, Lim et al., 2005 CH 3 COCHO Lim et al., Lim et al., 2005 HOC(O)COOH Lim et al., Lim et al., 2005 (COOH) Lim et al., Lim et al., 2005 Cloud Parameters as in wets module: LWC_offset=1.e -10 and CC_offset =0.01 ph is calculated in wets module The radius of cloud droplets is 5 μm. Ref. α Ref.

15 TM meeting, Heraklion, June 2010 Some first OXL results with TM4-ECPL

16 Budget Calculations of Oxalate with TM4-ECPL Chemical Production ΟΗ Oxidation Sinks Dry Deposition Wet Deposition Burden Mean Global Lifetime 33 Tg yr -1 Biogenic VOC 30 Tg yr -1 (~91%) Anthropogenic VOC 3 Tg yr -1 (~9%) 0.1 Tg yr -1 (~0.5%) 2 Tg yr -1 (~6%) 30.4 Tg yr -1 (~92.5%) 0.5 Tg 5 days 13(41%) 15(47%) Glycolaldehyde 92.5% Wet Deposition Methylglyoxal Dry Deposition 5(12%) Glyoxal 0.5% 6.0% OH Oxidation

17 Oxalate Distributions First Results Biogenic Sources ~1 μg m -3 Anthropogenic and biogenic sources ~0.5 μg m -3

18 Comparison with Measurements First Results ng(oxl)/m³ Schauinsland (47.55N, 7.54E) ΤΜ4 Obs. ng(oxl)/m³ ΤΜ4 Obs. Pay de Dome (45.46N, 2.57E) 0 Ιαν Φεβ Μαρ Απρ Μαϊ Ιουν Ιουλ Αυγ Αυγ Σεπ Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Οκτ Νοε Δεκ 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ιαν Φεβ Μαρ Απρ Μαϊ Ιουν Ιουλ Αυγ Αυγ Σεπ Οκτ Νοε Δεκ ng(oxl)/m³ ΤΜ4 Obs. Finokalia (35.3N, 25.7E) ng(oxl)/m³ ΤΜ4 Obs. Amsterdam Island (37.5S, 77.3E) Ιαν Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Φεβ αρ Απρ Μαϊ Ιουν Ιουλ Αυγ Αυγ Σεπ Οκτ Νοε Δεκ 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ιαν Φεβ Μαρ Απρ Μαϊ Ιουν Ιουλ Αυγ Αυγ Σεπ Οκτ Νοε Δεκ

19 Future Work... Some more tests with the EBI solver in the aqueous phase compare to FACSIMILE More Validation of OXL results (mainly in C. Africa and the Amazon Basin extreme VOC emission cases) Oxalate production also in particulate water (Ervens and Volkamer, 2010, ACPD) Organic mass aqueous phase production through acid catalysis and with inorganic constituents to form organic acids, oligomers and organosulfates (Lim et al., 2010, ACPD)

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