CMAQv5.1 SOA Update
Contents
Brief Description
Overview of AERO6 SOA Updates
Two Secondary Organic Aerosol (SOA) mechanisms are available in CMAQv5.1. The one used in aero6 is documented here. The SOA in aero6i (only compatible with saprc07tic) is documented in SAPRC07tic_AE6i.
SOA formation from long chain alkanes (C6-C20), naphthalene, ISOPRENE+NO3 reactions, and IEPOX are added to cb05e51- and saprc07-based mechanisms. Older mechanisms revert to the CMAQv5.0.2 SOA treatment.
In addition, for all mechanisms, the semivolatile SOA partitioning routines (newt and associated) are replaced with a new bisection method and the original system of equations is replaced with one equation for one unknown (see derivation below).
Organic Aerosol Species in v5.1 AERO6
Table 1: POA species introduced in CMAQ v5.0.2
| POA species | description | molec wt (g/mol) | reference |
|---|---|---|---|
| POCI | primary organic carbon in aitken mode | 220 | Simon and Bhave 2012 |
| POCJ | primary organic carbon in accumulation mode | 220 | Simon and Bhave 2012 |
| ANCOMI | non-carbon organic matter (H, O, etc.) attached to POC in aitken mode | 220 | Simon and Bhave 2012 |
| ANCOMJ | non-carbon organic matter (H, O, etc.) attached to POC in accumulation mode | 220 | Simon and Bhave 2012 |
Table 2: SOA Species
- SOA species in blue are semivolatile.
- SOA species in green are low volatility and treated as effectively nonvolatile.
- SOA species in yellow form due to reactive uptake and are treated as nonvolatile.
- SOA formed from particle-phase processing is in purple.
| SOA species | version introduced | precursor | oxidants | semivolatile | alpha (mass-based) | C* (ug/m3) | enthlapy (kJ/mol) | number of C | molec wt (g/mol) | OM/OC | Model ref | Experimental ref |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| AALK1 | v5.1 | long-chain alkanes | OH | SV_ALK1 | 0.0334 | 0.1472 | 53.0 | 12 | 168 | 1.17 | Pye and Pouliot 2012 | Presto et al. 2010 |
| AALK2 | v5.1 | long-chain alkanes | OH | SV_ALK2 | 0.2164 | 51.8774 | 53.0 | 12 | 168 | 1.17 | Pye and Pouliot 2012 | Presto et al. 2010 |
| AXYL1 | v4.7 | XYL/ARO2 excluding naphthalene | OH,NO | SV_XYL1 | 0.0310 | 1.3140 | 32.0 | 8 | 192 | 2.0 | Carlton et al. 2010 | Ng et al. 2007 |
| AXYL2 | v4.7 | XYL/ARO2 excluding naphthalene | OH,NO | SV_XYL2 | 0.0900 | 34.4830 | 32.0 | 8 | 192 | 2.0 | Carlton et al. 2010 | Ng et al. 2007 |
| AXYL3 | v4.7 | XYL/ARO2 excluding naphthalene | OH,HO2 | NA-nonvolatile | 0.36 | NA | NA | NA | 192 | 2.0 | Carlton et al. 2010 | Ng et al. 2007 |
| ATOL1 | v4.7 | TOL/ARO1 | OH,NO | SV_TOL1 | 0.0310 | 2.3260 | 18.0 | 7 | 168 | 2.0 | Carlton et al. 2010 | Ng et al. 2007 |
| ATOL2 | v4.7 | TOL/ARO1 | OH,NO | SV_TOL2 | 0.0900 | 21.2770 | 18.0 | 7 | 168 | 2.0 | Carlton et al. 2010 | Ng et al. 2007 |
| ATOL3 | v4.7 | TOL/ARO1 | OH,HO2 | NA-nonvolatile | 0.30 | NA | NA | NA | 168 | 2.0 | Carlton et al. 2010 | Ng et al. 2007 |
| ABNZ1 | v4.7 | benzene | OH,NO | SV_BNZ1 | 0.0720 | 0.3020 | 18 | 6 | 144 | 2.0 | Carlton et al. 2010 | Ng et al. 2007 |
| ABNZ2 | v4.7 | benzene | OH,NO | SV_BNZ2 | 0.8880 | 111.1100 | 18 | 6 | 144 | 2.0 | Carlton et al. 2010 | Ng et al. 2007 |
| ABNZ3 | v4.7 | benzene | OH,HO2 | NA-nonvolatile | 0.37 | NA | NA | NA | 144 | 2.0 | Carlton et al. 2010 | Ng et al. 2007 |
| APAH1 | v5.1 | naphthalene | OH,NO | SV_PAH1 | 0.2100 | 1.6598 | 18 | 10 | 243 | 2.03 | Pye et al. 2012 | Chan et al. 2009 |
| APAH2 | v5.1 | naphthalene | OH,NO | SV_PAH2 | 1.0700 | 264.6675 | 18 | 10 | 243 | 2.03 | Pye et al. 2012 | Chan et al. 2009 |
| APAH3 | v5.1 | naphthalene | OH,HO2 | NA-nonvolatile | 0.73 | NA | NA | NA | 243 | 2.03 | Pye 2012 | Chan 2009 |
| AISO1 | v4.7 | isoprene | OH,NO3 | SV_ISO1 | 0.2320 | 116.010 | 40 | 5 | 96 | 1.6 | Carlton et al. 2010 | Kroll et al. 2006 |
| AISO2 | v4.7 | isoprene | OH,NO3 | SV_ISO2 | 0.0288 | 0.6170 | 40 | 5 | 96 | 1.6 | Carlton et al. 2010 | Kroll et al. 2006 |
| AISO3 | v5.1 | IEPOX | NA-acid catalyzed uptake | NA-nonvolatile | NA | NA | NA | NA | 168.2 | 2.7 | Pye et al. 2013 | Eddingsaas et al. 2010 |
| ATRP1 | v4.7 | monoterpenes | OH,O3P,O3,NO3 | SV_TRP1 | 0.1393 | 14.7920 | 40 | 10 | 168 | 1.4 | Carlton et al. 2010 | Griffin et al. 1999 |
| ATRP2 | v4.7 | monoterpenes | OH,O3P,O3,NO3 | SV_TRP2 | 0.4542 | 133.7297 | 40 | 10 | 168 | 1.4 | Carlton et al. 2010 | Griffin et al. 1999 |
| ASQT | v4.7 | sesquiterpenes | OH,O3,NO3 | SV_SQT2 | 1.5370 | 24.9840 | 40 | 15 | 378 | 2.1 | Carlton et al. 2010 | Griffin et al. 1999 |
| AOLGA | v4.7 | anthropogenic SOA | time | NA-nonvolatile | NA | NA | NA | NA | 176.4 | 2.1 | Carlton et al. 2010 | Kalberer et al. 2004 |
| AOLGB | v4.7 | biogenic SOA | time | NA-nonvolatile | NA | NA | NA | NA | 252 | 2.1 | Carlton et al. 2010 | Kalberer et al. 2004 |
| AORGC | v4.7 | SOA from cloud processing of glyoxal, methylglyoxal | OH | NA-nonvolatile | NA | NA | NA | NA | 177 | 2.0 | Carlton et al. 2008 |
The reference temperature for table properties (C* and enthalpy) is 298 K.
If more than one gas-phase precursor is named, the first name corresponds to CB05 and the second to SAPRC07.
All gas-phase semivolatiles use a dry deposition surrogate of ORA (acetic acid, H-law=4.1e3 M/atm) and a wet deposition surrogate of ADIPIC ACID (H-law=2.0e8 M/atm).
Number of carbons is used to conserve carbon upon oligomerization to nonvolatile form.
Significance and Impact
Updates affect SOA from anthropogenic and biogenic sources. According to CMAQ, Alkane SOA is predicted to be responsible for ~30% of SOA from anthropogenic VOCs with the largest absolute concentrations in summer in urban (source) areas. Naphthalene (PAH) oxidation is predicted to produce modest amounts of SOA (Pye and Pouliot 2012). Note that PAH SOA in CMAQ v5.1 only considers naphthalene as the parent hydrocarbon which is about half of the PAHs considered as SOA precursors in Pye and Pouliot (2012).
For cb05e51 and SAPRC07 mechanisms with IEPOX formation in the gas-phase, heterogeneous uptake of IEPOX on acidic aerosol results in SOA (Pye et al. 2013). This IEPOX SOA replaces the old AISO3J treatment based on Carlton et al. 2010. The AISO3J species name is retained for IEPOX SOA in cb05e51. Additional speciation of SOA into 2-methyltetrols, 2-methylglyceric acid, organosulfates, and oligomers/dimers is available in SAPRC07tic with aero6i.
Affected files
Modified modules
- MECHS (cb05e51, racm, saprc07tb, saprc07tc, saprc07tic)
- aero/aero6
Table 3: Species updated or added in CMAQv5.1
| Aerosol Species | Change since v5.0.2 | Applicable Mechanism | Description |
|---|---|---|---|
| AH3OP | added | all | Hydronium ion (predicted by ISORROPIA), used for IEPOX uptake |
| APAH1,2 | added | cb05e51, saprc07tb, saprc07tc, saprc07tic, racm | naphthalene aerosol from RO2+NO reactions |
| APAH3 | added | cb05e51, saprc07tb, saprc07tc, saprc07tic, racm | naphthalene aerosol from RO2+HO2 reactions |
| AISO1,2 | updated | cb05e51, saprc07tb, saprc07tc*, racm | aerosol from isoprene reactions NO3 added with yields following the OH pathway |
| AISO3 | updated | cb05e51, saprc07tb, saprc07tc*, racm | aerosol from reactive uptake of IEPOX on aqueous aerosol particles |
| AALK1,2 | added | cb05e51, saprc07tb, saprc07tc, saprc07tic, racm | alkane aerosol |
| AALK | removed | all | deprecated alkane aerosol |
*saprc07tic does not include SOA from isoprene+NO3 in AISO1,2 (it is included in AISOPNNJ). saprc07tic does not include IEPOX SOA in AISO3 (it is included in AITETJ, AIEOSJ, AIDIMJ, etc). AISO3 is approximately zero in saprc07tic.
Additional Information
Calculation of OC and OM (for species definition file and combine). Be sure to check the spacing and place on one line before using.
AOCIJ ,ugC/m3 ,(AXYL1J[1]+AXYL2J[1]+AXYL3J[1])/2.0+ (ATOL1J[1]+ATOL2J[1]+ATOL3J[1])/2.0+ (ABNZ1J[1]+ABNZ2J[1]+ABNZ3J[1])/2.0 + (AISO1J[1]+AISO2J[1])/1.6+AISO3J[1]/2.7+ (ATRP1J[1]+ATRP2J[1])/1.4+ASQTJ[1]/2.1+ 0.64*(AALK1J[1]+AALK2J[1])+ AORGCJ[1]/2.0+(AOLGBJ[1]+AOLGAJ[1])/2.1+ APOCI[1]+APOCJ[1]+ APAH1J[1]/2.03+APAH2J[1]/2.03+APAH3J[1]/2.03+
AOMIJ ,ug/m3 ,AXYL1J[1]+AXYL2J[1]+AXYL3J[1]+ ATOL1J[1]+ATOL2J[1]+ATOL3J[1]+ ABNZ1J[1]+ABNZ2J[1]+ABNZ3J[1]+ AISO1J[1]+AISO2J[1]+ATRP1J[1]+ATRP2J[1]+ASQTJ[1]+ (AALK1J[1]+AALK2J[1])+AORGCJ[1]+ APOCI[1]+APOCJ[1]+APNCOMI[1]+APNCOMJ[1]+ APAH1J[1]+APAH2J[1]+APAH3J[1]+
New partitioning equation algorithms
We would like to solve for the partitioning of each semivolatile species, i, between the gas (G) and aerosol (A) phase.
Equations:
(1) Total moles in aerosol phase
N = nonvolatile + sum_i ( Ai/mi )
where nonvolatile is the moles of nonvolatile aerosol (umol/m3)
N is the total number of moles in the aerosol (umol/m3)
Ai is the mass concentration of species i in the aerosol (ug/m3)
mi is the molecular weight of species i
(sum_i indicates sum over species i)
(2) Equilibrium equation for species i
Cstari = Gi mi N / Ai
where Cstari is the saturation concentration of species i at the relevant temperature (ug/m3)
Gi is the mass concentration of species i in the gas phase (ug/m3)
(3) Species mole balance
Toti = Gi + Ai
where Toti is the total mass concentration of species i in the system (ug/m3)
Solve for N:
Rearrange equation (3) for Gi and plug into (2). Solve for Ai:
(4) Ai = Toti mi N / ( Cstari + mi N )
Plug (4) into equation (1) to obtain one equation for one unknown and solve for N:
(5) f(N) = 0 = nonvolatile/N + sum_i ( Toti / ( Cstari + mi N ) ) - 1
With the value of N, Ai (from 4) and Gi (from 3) can be computed.
References
Carlton, A. G.; Bhave, P. V.; Napelenok, S. L.; Edney, E. D.; Sarwar, G.; Pinder, R. W.; Pouliot, G. A.; Houyoux, M., Model representation of secondary organic aerosol in CMAQv4.7. Environmental Science & Technology 2010, 44 (22), 8553-8560. article
Carlton, A. G.; Turpin, B. J.; Altieri, K. E.; Seitzinger, S. P.; Mathur, R.; Roselle, S. J.; Weber, R. J., CMAQ Model Performance Enhanced When In-Cloud Secondary Organic Aerosol is Included: Comparisons of Organic Carbon Predictions with Measurements. Environmental Science & Technology 2008, 42 (23), 8798-8802. article
Chan, A. W. H.; Kautzman, K. E.; Chhabra, P. S.; Surratt, J. D.; Chan, M. N.; Crounse, J. D.; Kurten, A.; Wennberg, P. O.; Flagan, R. C.; Seinfeld, J. H.Secondary organic aerosol formation from photooxidation of naphthalene and alkylnaphthalenes: Implications for oxidation of intermediate volatility organic compounds (IVOCs) Atmos. Chem. Phys. 2009, 9 (9), 3049-3060. article
Eddingsaas, N. C.; VanderVelde, D. G.; Wennberg, P. O., Kinetics and products of the acid-catalyzed ring-opening of atmospherically relevant butyl epoxy alcohols. J. Phys. Chem. A. 2010, 114 (31), 8106-8113. article
Griffin, R. J.; Cocker, D. R.; Flagan, R. C.; Seinfeld, J. H., Organic aerosol formation from the oxidation of biogenic hydrocarbons. J. Geophys. Res. 1999, 104 (D3), 3555-3567. article
Kalberer, M.; Paulsen, D.; Sax, M.; Steinbacher, M.; Dommen, J.; Prevot, A. S. H.; Fisseha, R.; Weingartner, E.; Frankevich, V.; Zenobi, R.; Baltensperger, U., Identification of polymers as major components of atmospheric organic aerosols. Science 2004, 303 (5664), 1659-1662. article
Kroll, J. H.; Ng, N. L.; Murphy, S. M.; Flagan, R. C.; Seinfeld, J. H., Secondary organic aerosol formation from isoprene photooxidation. Environ. Sci. Technol. 2006, 40 (6), 1869-1877. article
Ng, N. L.; Kroll, J. H.; Chan, A. W. H.; Chhabra, P. S.; Flagan, R. C.; Seinfeld, J. H., Secondary organic aerosol formation from m-xylene, toluene, and benzene. Atmos. Chem. Phys. 2007, 7 (14), 3909-3922. article
Presto, A. A.; Miracolo, M. A.; Donahue, N. M.; Robinson, A. L.Secondary organic aerosol formation from high-NOx photo-oxidation of low volatility precursors: n-alkanes Environ. Sci. Technol. 2010, 44, 2029– 2034. article
Pye, H. O. T., R. W. Pinder, I. Piletic, Y. Xie, S. L. Capps, Y.-H. Lin, J. D. Surratt, Z. Zhang, A. Gold, D. J. Luecken, W. T. Hutzell, M. Jaoui, J. H. Offenberg, T. E. Kleindienst, M. Lewandowski, and E. O. Edney, Epoxide pathways improve model predictions of isoprene markers and reveal key role of acidity in aerosol formation, Environ. Sci. Technol., 2013, 47 (19), 11056-11064. article
Pye, H. O. T. and G. A. Pouliot, Modeling the role of alkanes, polycyclic aromatic hydrocarbons, and their oligomers in secondary organic aerosol formation, Environ. Sci. Technol., 2012, 46 (11), 6041-6047. article
Simon, H. and P. V. Bhave, Simulating the degree of oxidation in atmospheric organic particles, Environ. Sci. Technol., 2012, 46, 331-339, 2012. article
Contact
Havala Pye, National Exposure Research Laboratory, U.S. EPA
