# PM25 OUTPUT ERROR about CMAQ5.3.3-ISAM
**URL:** https://forum.cmascenter.org/t/pm25-output-error-about-cmaq5-3-3-isam/6159
**Category:** CMAQ
**Created:** [March 8, 2026, 2:34pm UTC](https://forum.cmascenter.org/t/pm25-output-error-about-cmaq5-3-3-isam/6159 "2026-03-08T14:34:02Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@sher](https://forum.cmascenter.org/u/sher)
#### Post date: [March 8, 2026, 2:34pm UTC](https://forum.cmascenter.org/t/pm25-output-error-about-cmaq5-3-3-isam/6159/1 "2026-03-08T14:34:02Z")
Hello, I am using **CMAQ\_ISAM v5.3.3** and have tagged all **seven species related to PM2.5**. When analyzing the **PM2.5** data from the CMAQ-ISAM output, I found an issue: the total concentration of **tagged species** accounts for only **30–40%** of the total PM2.5. In addition, the **sectoral source contribution** results are also very abnormal and differ greatly from those reported in previous studies in the literature.
Could these abnormal results be related to a **low tagging ratio**? If not, what other factors might cause such abnormal results? I look forward to your reply.
The issue I encountered is that when calculating the tagged PM2.5 concentration (SA\_ACONC), I found that it differs significantly from the values in ACONC. In my calculation(SA\_ACONC), I only used:
PM25\_TOT [µg/m³] = (ATOTI × PM25AT) + (ATOTJ × PM25AC)
where:
ATOTI = ASO4I + ANO3I + ANH4I + ANAI + ACLI + AECI + AOTHRI + APOCI + APNCOMI
ATOTJ = ASO4J + ANO3J + ANH4J + ANAJ + ACLJ + AECJ + AOTHRJ + AFEJ + ASIJ + ATIJ + ACAJ + AMGJ + AMNJ + AALJ + AKJ + APOCJ + APNCOMJ
These species were included in the calculation because they are all the taggable species related to PM2.5. I would like to ask what might be the possible reasons for this. These are the only species that can be tagged in the file.`isamcontrol.txt`
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### Author:  [@lizadams](https://forum.cmascenter.org/u/lizadams)
#### Post date: [March 17, 2026, 9:15pm UTC](https://forum.cmascenter.org/t/pm25-output-error-about-cmaq5-3-3-isam/6159/2 "2026-03-17T21:15:08Z")
Please see this prior issue.
> [@Only Simulating Primary Particulate Matter (PPM) with CMAQ](https://forum.cmascenter.org/t/only-simulating-primary-particulate-matter-ppm-with-cmaq/3626/2):
>
> Dear Alpha\_Su, Thanks for your question. While quantifying the contribution of primary vs. secondary species to total PM is a highly valuable result, it can be a bit tricky to process it from CMAQ output. For some time, CMAQ has employed various chemical and mass transfer schemes to process aerosols that sort of blur the lines between primary and secondary – this is of course happening in the real atmosphere as well. As you point out, APOC and APOM are nominally ‘primary organic aerosol’, but …
This is the total for CMAQv5.4+, which is likely different that the version that you are using.
!! Total PM Aggregates
ATOTIJ\_ONR ,ug m-3 ,ASO4I\_ONR[1]+ANO3I\_ONR[1]+ANH4I\_ONR[1]+ANAI\_ONR[1]+ACLI\_ONR[1]
+AECI\_ONR[1]+AOTHRI\_ONR[1] \
+ASO4J\_ONR[1]+ANO3J\_ONR[1]+ANH4J\_ONR[1]+ANAJ\_ONR[1]+ACLJ\_ONR[1]
+AECJ\_ONR[1]+AOMIJ\_ONR[0]+AOTHRJ\_ONR[1]+AFEJ\_ONR[1]+ASIJ\_ONR[1]
+ATIJ\_ONR[1]+ACAJ\_ONR[1]+AMGJ\_ONR[1]+AMNJ\_ONR[1]+AALJ\_ONR[1]+AKJ\_ONR[1] here ONR is the tagged species