CMAQ v5.1 cb05mp51 ae6 aq

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Brief Description

The cb05mp51_ae6_aq mechanism uses the cb05e51_ae6_aq mechanism to predict ozone and other criteria air pollutants and simulates the same hazardous (toxic) air pollutants as the cb05tump_ae6_aq mechanism.


The cb05mp51_ae6_aq mechanism modifies the AE and NR namelist of cb0e51_ae6_aq to predict several additional Hazardous Air Pollutants (HAPs). The latter mechanism already simulates benzene, gas phase mercury compounds, 1,3-butadiene, formaldehyde, acetaldehyde, acrolein, and reactive tracers for the emissions of the last three compounds. Several reactive tracers classified as HAPs are added to the NR namelist (Table 1). Although the photochemical mechanism does not use contain these tracers (i.e., the mech_cb05mp51_ae6_aq.def file does not use them.), they undergo exponential decay based on photochemical processes believed to destroy them (Luecken et al., 2006).

Aerosol and Cloud Physics

For toxic aerosol species, the mechanism needs to use the same aerosol and cloud modules as cb05tump_ae_aq to represent their model physics.

Building and Running

Building CMAQ with the cb05mp51_ae6_aq mechanism requires different build settings than the standard version of CMAQ. Table 2 shows the build settings needed to construct CCTM using this mechanism with its EBI solver. Settings not specified in Table 2 remain the same as the standard version. NOTE that the smvgear and ros3 options for the gas module also work for this mechanism.

To run the CMAQ with the cb05tump_ae6_aq mechanism, the user needs emissions files containing rates listed in the GC, NR and AE namelists files. A user must complete SMOKE processing with correct ancillary files such as GSREF and GSPRO and the merged NEI/Toxics database. To obtain these items contact the CMAS Help desk at

The depv/m3dry module allows simulating a bi-directional fluxes for atmospheric mercury in addition to ammonia. The environment variable, CTM_HGBIDI, determines whether a model execution  uses this capacity. To use the bi-directional fluxes for atmospheric mercury, add the below line to the runscript.


The default value is F. Consult the bidirectional notes for more information about using this option.

NOTE that simulations can subset or eliminate Hazardous Air Pollutants (HAPs) simulated. Users can then tailor their applications based on the HAPs of interest. Guidelines follow. For the NR namelist, any or all HAPs can be eliminated by deleting the rows that define them. Users can have to be more careful when removing HAPs from the AE namelist. They have to delete the group of rows that define all the aerosol modes for these HAPs. Two examples are below.

  • The user wants to simulate toxic metal aerosol species not but diesel species in particulate matter. To accomplish this objective, the AE namelist will not contain the rows that define the model species representing to the modes of DE_SO4, DE_NO3, DE_EC, DE_OC, DE_OTHR, and DE. The namelist retains the rows defining modes of the toxic metals. Note that NR namelist remains the same.
  • The user only wants to simulate the fate and transport of atmospheric mercury. They need to edit two namelists. For the NR namelist, the user deletes rows that defined all of its HAPs (see Table 1 and its footnote) and the result is equivalent to NR namelist for the CB05TUCL mechanism. For the AE namelist, the user deletes the rows that represent the HAPs in Table 3, EXCEPT FOR ROWS FOR PARTICULATE MERCURY SPECIES.

Significance and Impact

The cb05mp51_ae6_aq mechanism allows using the newest version of CB05 based mechanism in CMAQ version 5.1 to make air quality assessments and control plans for both criteria and hazardous air pollutants.

Affected files

  • MECH/cb05mp51_ae6_aq/*
  • gas/ebi_cb05mp51_ae6_aq/*



Table 1. Gas Phase HAP Species in NR namelist

Species Name Compound CAS# In mech.def
ACRYLONITRILE Acrylonitrile 107-13-1 No
CARBONTET Carbon Tetrachloride 56-23-5 No
PROPDICHLORIDE Propylene Dichloride 78-87-5 No
DICHLOROPROPENE 1,3-Dichloropropene 542-75-6 No
CL4_ETHANE1122 1,1,2,2-Tetrachloroethane 79-34-5 No
BR2_C2_12 1,2-Dibromoethane 106-93-4 No
CL2_C2_12 1,2-Dichloroethane 107-06-2 No
ETOX Ethylene Oxide 75-21-8 No
CL2_ME Methylene Chloride 75-09-2 No
CL4_ETHE Perchloroethylene 127-18-4 No
CL3_ETHE Trichloroethylene 79-01-6 No
CL_ETHE Vinyl Chloride 75-01-4 No
NAPHTHALENE Naphthalene 91-20-3 No
QUINOLINE Quinoline 91-22-5 No
HYDRAZINE Hydrazine 302-01-2 No
TOL_DIIS 2,4-Toluene Diisocyanate 584-84-9 No
HEXAMETHY_DIIS Hexamethylene 1,6-Diisocyanate 822-06-0 No
MAL_ANHYDRIDE Maleic Anhydride 108-31-6 No
TRIETHYLAMINE Triethylamine 121-44-8 No
DICHLOROBENZENE 1,4-Dichlorobenzene 106-46-7 No

Table 2. CCTM Build Script Settings Option settings needed in CCTM build script if using EBI solver.
NOTE that unspecific options remain same as CCTM with aerosols.

 1. Select a HAP mechanism
set MechMod = MECHS/cb05mp51_ae6_aq 2. Select correct EBI solver
# NOTE THAT ros3 and smvgear options also work
set ModGas = gas/ebi_cb05mp51_ae6_aq 3. AERO option required
set ModAero = aero/aero6_mp 4. cloud processing and aqueous chemistry setting
set ModCloud =cloud/acm_ae6_mp.


William T. Hutzell, National Exposure Research Laboratory, U.S. EPA