Hi all, I was trying to compare diesel exhaust SCC (speciation classification code) from the diesel exhaust SCC profile in Speciation Tool and CB05 and CB06 diesel profiles in SMOKE, it turns out that there is one VOC species missing - acetone. Is there any reason for this?
While this is not my area of expertise, my colleague tells me that acetone is exempted from the definition of VOC. Therefore the VOC/TOG ratio is used to account for the exempt VOC and give the correct speciation for the VOC emissions.
Thanks for reply. However, based on the lumping species of CB06, there is definitely one lumping species (ACET) named for acetone. Therefore this should not be the reason why acetone is not included in VOC. If this is the case, then formaldehyde should also be exempted from VOC.
FYI, ACET is not a CBO5 species but it is a CB06 species
For CB05, acetone is lumped into PAR, which doesn’t mean it is not belonging to VOC.
Shengpo - can you provide more detail on the profile code(s) in question? Is your question why is the profile missing the model species “ACET” or the SPECIATE species “acetone”? Have you looked at the SPECIATE database to find the SPECIATE species in this profile? Also, for your information, SCC means source classification code, not speciation classification code.
mstrum: Thanks for clarification of the SCC long-name. I have looked up the SPECIATE (version 4.0, 4.2, 4.3, 4.4, 4.5, 5.0, 5.1) species of diesel profile (#4674, Diesel Exhaust - Medium Duty Trucks), and cross-checked the individual species listed in the reference (Schauer et al., 1999). It turns out there is one species (acetone) missing in the SPECIATE table. Therefore, the following lumping processes are missing this species. Currently I checked CB05 and CB06, and their diesel profilings are wrong. Possibly all other chemical mechanisms are also misleading for diesel while using SPECIATE database.
profile 4674 is a VOC profile and not a TOG profile. The reason it is not a TOG profile is that methane and ethane were not measured. In SPECIATE, you can’t make a VOC profile and put acetone in it because acetone is NOT a VOC; therefore, Schauer’s acetone data were removed. You can see this based on the notes in the calculation workbook for this profile which you can access at https://gaftp.epa.gov/Air/emismod/SPECIATE_supportingdata/v4_0/ (select "Schauer_paper72_.mddiesel-9-27-4.xlsx) So actually, the very first answer was correct. ACETONE cannot be present in a VOC profile because it is NOT a VOC. If ethane were measured, then this could have been an “NMOG” profile (non-methane organic gases) and in that case it would have had the acetone. You may want to choose a different diesel exhaust profile. I looked at the SPECIATE database and there are several mobile diesel exhaust profiles (off road and onroad) with acetone in them such as 95332 and 95335a (there are many more). You may also want to look at the documentation of speciation profiles used in EPAs emissions model MOVES3 at https://nepis.epa.gov/Exe/ZyPDF.cgi?Dockey=P1010THD.pdf to review the profiles used in that model for diesel exhaust.
Thanks for reply. I can understand 4674 is a VOC profile and not a “TOG” profile, but this cannot explain why acetone is not included. If acetone is not a VOC you mentioned, what is the definition of VOC as you suggest? Also, if acetone is not in 4674 profile just because it is a OVOC, what about formaldehyde and acetaldehyde? They are also OVOC but included in 4674.
In the emissions inventory and SPECIATE, we use EPA’s regulatory definition of VOC, which is in the Code of Federal regulations, Title 40, Chapter I, Subchapter C, part 51, 51.100 (definitions). Note that under that definition, formaldehyde and acetaldehyde are both VOC but acetone, ethane, methane and many other organic gaseous compounds are NOT VOC. The underlying excel workbook (the link from my last reply) clearly indicates the reason acetone was not included, and that is because this is a VOC profile and acetone is NOT a VOC.
Here is where you can find the regulatory definition of VOC.
I have copied that definition in the below:
(s) Volatile organic compounds (VOC) means any compound of carbon, excluding carbon monoxide, carbon dioxide, carbonic acid, metallic carbides or carbonates, and ammonium carbonate, which participates in atmospheric photochemical reactions.
(1) This includes any such organic compound other than the following, which have been determined to have negligible photochemical reactivity: Methane; ethane; methylene chloride (dichloromethane); 1,1,1-trichloroethane (methyl chloroform); 1,1,2-trichloro-1,2,2-trifluoroethane (CFC-113); trichlorofluoromethane (CFC-11); dichlorodifluoromethane (CFC-12); chlorodifluoromethane (HCFC-22); trifluoromethane (HFC-23); 1,2-dichloro 1,1,2,2-tetrafluoroethane (CFC-114); chloropentafluoroethane (CFC-115); 1,1,1-trifluoro 2,2-dichloroethane (HCFC-123); 1,1,1,2-tetrafluoroethane (HFC-134a); 1,1-dichloro 1-fluoroethane (HCFC-141b); 1-chloro 1,1-difluoroethane (HCFC-142b); 2-chloro-1,1,1,2-tetrafluoroethane (HCFC-124); pentafluoroethane (HFC-125); 1,1,2,2-tetrafluoroethane (HFC-134); 1,1,1-trifluoroethane (HFC-143a); 1,1-difluoroethane (HFC-152a); parachlorobenzotrifluoride (PCBTF); cyclic, branched, or linear completely methylated siloxanes; acetone; perchloroethylene (tetrachloroethylene); 3,3-dichloro-1,1,1,2,2-pentafluoropropane (HCFC-225ca); 1,3-dichloro-1,1,2,2,3-pentafluoropropane (HCFC-225cb); 1,1,1,2,3,4,4,5,5,5-decafluoropentane (HFC 43-10mee); difluoromethane (HFC-32); ethylfluoride (HFC-161); 1,1,1,3,3,3-hexafluoropropane (HFC-236fa); 1,1,2,2,3-pentafluoropropane (HFC-245ca); 1,1,2,3,3-pentafluoropropane (HFC-245ea); 1,1,1,2,3-pentafluoropropane (HFC-245eb); 1,1,1,3,3-pentafluoropropane (HFC-245fa); 1,1,1,2,3,3-hexafluoropropane (HFC-236ea); 1,1,1,3,3-pentafluorobutane (HFC-365mfc); chlorofluoromethane (HCFC-31); 1 chloro-1-fluoroethane (HCFC-151a); 1,2-dichloro-1,1,2-trifluoroethane (HCFC-123a); 1,1,1,2,2,3,3,4,4-nonafluoro-4-methoxy-butane (C4F9OCH3 or HFE-7100); 2-(difluoromethoxymethyl)-1,1,1,2,3,3,3-heptafluoropropane ((CF3)2CFCF2OCH3); 1-ethoxy-1,1,2,2,3,3,4,4,4-nonafluorobutane (C4F9OC2H5 or HFE-7200); 2-(ethoxydifluoromethyl)-1,1,1,2,3,3,3-heptafluoropropane ((CF3)2CFCF2OC2H5); methyl acetate; 1,1,1,2,2,3,3-heptafluoro-3-methoxy-propane (n-C3F7OCH3, HFE-7000); 3-ethoxy- 1,1,1,2,3,4,4,5,5,6,6,6-dodecafluoro-2-(trifluoromethyl) hexane (HFE-7500); 1,1,1,2,3,3,3-heptafluoropropane (HFC 227ea); methyl formate (HCOOCH3); 1,1,1,2,2,3,4,5,5,5-decafluoro-3-methoxy-4-trifluoromethyl-pentane (HFE-7300); propylene carbonate; dimethyl carbonate; trans-1,3,3,3-tetrafluoropropene; HCF2OCF2H (HFE-134); HCF2OCF2OCF2H (HFE-236cal2); HCF2OCF2CF2OCF2H (HFE-338pcc13); HCF2OCF2OCF2CF2OCF2H (H-Galden 1040x or H-Galden ZT 130 (or 150 or 180)); trans 1-chloro-3,3,3-trifluoroprop-1-ene; 2,3,3,3-tetrafluoropropene; 2-amino-2-methyl-1-propanol; t-butyl acetate; 1,1,2,2- Tetrafluoro -1-(2,2,2-trifluoroethoxy) ethane; cis-1,1,1,4,4,4-hexafluorobut-2-ene (HFO-1336mzz-Z); and perfluorocarbon compounds which fall into these classes:
(i) Cyclic, branched, or linear, completely fluorinated alkanes;
(ii) Cyclic, branched, or linear, completely fluorinated ethers with no unsaturations;
(iii) Cyclic, branched, or linear, completely fluorinated tertiary amines with no unsaturations; and
(iv) Sulfur containing perfluorocarbons with no unsaturations and with sulfur bonds only to carbon and fluorine.
Thanks for reply.
Based on the “regulatory” definition of VOC(§51.100 Definitions), the (s) is the general definition of VOC, and I think the issue came due to (1). It took me a while to think about the (1) definition. The (1) definition removes many species even if some of them are with large amounts (like methane and ethane). It brings more three questions:
-
How can one VOC profile decide whether they want to remove species listed in (1)? Because as you mentioned, some of them are keeping the removed species (like acetone in 95332 and 95335a).
-
If the removed species are decided to divide from the VOC profile, the weighting of species will be changed. For example, the 4674 profile removed acetone, then the sum of VOC is changed, and then the % of each species will be different (ex: formaldehyde % is changed from 7.8% to 8.5% after acetone is removed). What’s your input for this one?
-
Since the species defined in (1) are with negligible photochemical reactivity, their photochemistry can also be presented by photochemical chemistry calculated in the model. Why do we need a extra work to remove them prior to the CTM modeling?
For question 1. If the "MASTER_POLLUTANT in the SPECIATE database is VOC, then the profile developer should not include species that do not fit the definition. If the “MASTER_POLLUTANT” is TOG, then the developer should include ALL organic gases. If the MASTER_POLLUTANT is “NMOG” (non-methane organic gases) then the user should include ALL organic gases except methane. In some cases, As an example, see G95241TOG in the SPECIATE database and read the notes.
2. It is the same as item 1. the weight percent depends on the MASTER_POLLUTANT. Compare G95231TOG with 95241 and you will see large differences in the weight percents because the MASTER_POLLUTANT changed. That is why it is so important to properly specify the master pollutant in SPECIATE. In the National Emissions Inventory, VOC is inventoried, not TOG. In SMOKE, the speciation profile is used to convert VOC to TOG and speciate the TOG. If a profile is already VOC then only the VOC will end up being speciated into its components.
3. SPECIATE needs to be true to the MASTER_POLLUTANT. If we define the MASTER_POLLUTTANT as VOC we cannot include a non-VOC in the species. I suppose we could have called the MASTER_POLLUTANT “VOCPLUS” and then included the acetone. You are free to run the Speciation Tool with an update to that profile with the acetone included. Then the TOG to VOC ratio will be something larger than 1 (due to the acetone) and you will ultimately get the proper quantities of each SPECIATE species (including acetone),
Hi Mstrum:
Thanks for the details of the explanation for this issue.
I can understand the removal of species like acetone based on the definition of VOC. However, the reason for deleting acetone is because the species is considered as the one to have “negligible photochemical reactivity (Code of Federal regulations)”. As for CMAQ modeling, each (lumped) VOC species have their own photochemical reactivities by applying chemical reactions; if the species is with “negligible photochemical reactivity” then its rate constant should be lower, and it doesn’t need to be removed in the emission speciation. Also, after CB06, the acetone has been typed as single lumped VOC (ACET), is it possible that this kind of VOC treatment will underestimate the amount of ACET?
Another question is that if some of the species in one VOC profile is removed, the sum of VOC emissions will be changed, as well as the speciation ratio for each species. For example, in 4674 diesel profile, the speciation ratio of n-butane is 1.34% in original profile; after remove acetone, because the total amount of emissions is reduced, the ratio of n-butane changed to 1.46% (the one used in Speciation Tool). How do you take care of this difference?
Sorry for brining this issue again because I may need more explanation for figure this out.
I am not sure what is meant by “the acetone has been typed as a single lumped VOC (ACET)” If you want to add acetone after the speciation is done, that seems like it would work. The main issue is whether the emissions of VOC from the SCC that is assigned to that profile are truly VOC or are VOC+acetone. SPECIATE presumes they are VOC (that is the master pollutant) and because of that, the weight percents of all VOC are correct as long as the mass going into the speciation process is truly VOC.
Since acetone is not a VOC, then it is not part of the VOC profile – the weight percents are based on VOC, not VOC+acetone.