# HONO estimation in CB6 chemical mechanism

**URL:** https://forum.cmascenter.org/t/hono-estimation-in-cb6-chemical-mechanism/3625
**Category:** CMAQ
**Tags:** smoke
**Created:** [October 16, 2022, 9:47am UTC](https://forum.cmascenter.org/t/hono-estimation-in-cb6-chemical-mechanism/3625 "2022-10-16T09:47:45Z")
**Posts on this page:** 1
**Page:** 1

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### Author: ![LYM](https://avatars.discourse-cdn.com/v4/letter/l/b38774/32.png) [@LYM](https://forum.cmascenter.org/u/LYM)
#### Post date: [October 16, 2022, 9:47am UTC](https://forum.cmascenter.org/t/hono-estimation-in-cb6-chemical-mechanism/3625/1 "2022-10-16T09:47:45Z")

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Hi, everyone,  
When I process NEI2017 through the 2017 emissions modeling platform that uses CB6 chemical mechanism, I find that HONO is added as a species from NOX in CB6. In this case, NOX is splitted into NO, NO2, and HONO in gspro file:

HONO;“NOX”;“NO2”;0.092;46.0;0.092  
HONO;“NOX”;“NO”;0.9;46.0;0.9! See EMF “Note” documenting profile N002  
HONO;“NOX”;“HONO”;0.008;46.0;0.008

Why should HONO emission included in NOX? According to my understanding of the related literature, actually we don’t know HONO emission, but we can estimate HONO emission by the ratio of HONO emission to the known NOX emission. Accordingly, why weren’t NO, NO2, and HONO allocated as followed in gspro file?

HONO;“NOX”;“NO2”;0.1;46.0;0.092  
HONO;“NOX”;“NO”;0.9;46.0;0.9! See EMF “Note” documenting profile N002  
HONO;“NOX”;“HONO”;0.008;46.0;0.008

Thank you very much for your help!