CMAQv5.1 SOA Update

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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.

Figure 1: Schematic of CMAQv5.1 SOA in AERO6. Pathways in red are new to CMAQv5.1.


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