# O3 formed from NOx in CMAQ-ISAMv5.4

**URL:** <https://forum.cmascenter.org/t/o3-formed-from-nox-in-cmaq-isamv5-4/4629>\
**Category:** CMAQ-ISAM\
**Tags:** cmaq\
**Created:** [January 16, 2024, 12:54pm UTC](https://forum.cmascenter.org/t/o3-formed-from-nox-in-cmaq-isamv5-4/4629 "2024-01-16T12:54:28Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![laidemian](https://avatars.discourse-cdn.com/v4/letter/l/edb3f5/32.png) [@laidemian](https://forum.cmascenter.org/u/laidemian)\
**Post date:** [January 16, 2024, 12:54pm UTC](https://forum.cmascenter.org/t/o3-formed-from-nox-in-cmaq-isamv5-4/4629/1 "2024-01-16T12:54:28Z")

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Dear staff,  
I am wondering whether I can identify O3 formed from NOx in CMAQ-ISAMv5.4 In other words, I would like to know the contribution of NOX from another location to the ozone of the receptor. For example, I would like to know how much NOX from New York forms ozone during transmission, and how much of this NOX ultimately contributes to the ozone in Washington. May I ask if it is possible to label and track NOX in New York in ISAM? I saw other posts suggesting tracking NOX in two different situations, such as GRIDDED\_ EMIS1\_ NOX, GRIDDED\_ EMIS1\_ NOTNOX, I have a question. What is the difference between this operation and BFM? Does this operation also have non-linear effects on ozone？ Looking forward to your reply

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**Author:** ![sergey](https://avatars.discourse-cdn.com/v4/letter/s/9fc348/32.png) [@sergey](https://forum.cmascenter.org/u/sergey)\
**Post date:** [January 16, 2024, 2:39pm UTC](https://forum.cmascenter.org/t/o3-formed-from-nox-in-cmaq-isamv5-4/4629/2 "2024-01-16T14:39:14Z")

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CMAQ-ISAM allows from tracking from defined geographical areas. Refer to included Users Guide chapter on ISAM and general literature on source apportionment.

Sergey