# Natural emission tag in CMAQ-ISAM V5.4 **URL:** \ **Category:** CMAQ-ISAM\ **Created:** [September 1, 2023, 4:02am UTC](https://forum.cmascenter.org/t/natural-emission-tag-in-cmaq-isam-v5-4/4341 "2023-09-01T04:02:25Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![wry2233](https://yyz1.discourse-cdn.com/flex027/user_avatar/forum.cmascenter.org/wry2233/32/3458_2.png) [@wry2233](https://forum.cmascenter.org/u/wry2233)\ **Post date:** [September 1, 2023, 4:02am UTC](https://forum.cmascenter.org/t/natural-emission-tag-in-cmaq-isam-v5-4/4341/1 "2023-09-01T04:02:25Z")
Dear all, I plan to turn on MEGAN biogenic emissions and BDSNP soil NO emissions in my simulation. And I want to separate O3 contributions from different sources. The default ‘Stream Label’ for biogenic VOC emissions computed by MEGAN is ‘MIOG’. What ‘Stream Label’ for DSNP soil NO emissions? I couldn’t find relevant information in tutorial materials. ---
**Author:** ![hogrefe.christian](https://avatars.discourse-cdn.com/v4/letter/h/74df32/32.png) [@hogrefe.christian](https://forum.cmascenter.org/u/hogrefe.christian)\ **Post date:** [September 1, 2023, 1:51pm UTC](https://forum.cmascenter.org/t/natural-emission-tag-in-cmaq-isam-v5-4/4341/2 "2023-09-01T13:51:43Z")
The MIOG stream label captures the contributions of MEGAN emissions of both biogenic VOC and soil NO (either from BDSNP or the default Yienger-Levy scheme, depending on the option set in the run script). ---
**Author:** ![wry2233](https://yyz1.discourse-cdn.com/flex027/user_avatar/forum.cmascenter.org/wry2233/32/3458_2.png) [@wry2233](https://forum.cmascenter.org/u/wry2233)\ **Post date:** [September 3, 2023, 7:20am UTC](https://forum.cmascenter.org/t/natural-emission-tag-in-cmaq-isam-v5-4/4341/3 "2023-09-03T07:20:50Z")
Hi Hogrefe, Thanks for your response. And I wonder whether it calculate soil NO emission by YL95 scheme if I set _BDSNP\_MEGAN_ ‘N’. ---
**Author:** ![hogrefe.christian](https://avatars.discourse-cdn.com/v4/letter/h/74df32/32.png) [@hogrefe.christian](https://forum.cmascenter.org/u/hogrefe.christian)\ **Post date:** [September 3, 2023, 6:57pm UTC](https://forum.cmascenter.org/t/natural-emission-tag-in-cmaq-isam-v5-4/4341/4 "2023-09-03T18:57:57Z")
Correct. If BDSNP\_MEGAN is set to ‘N’, MEGAN uses the default YL95 scheme to calculate soil NO instead of using the BDSNP option. ---
**Author:** ![wry2233](https://yyz1.discourse-cdn.com/flex027/user_avatar/forum.cmascenter.org/wry2233/32/3458_2.png) [@wry2233](https://forum.cmascenter.org/u/wry2233)\ **Post date:** [September 5, 2023, 1:56am UTC](https://forum.cmascenter.org/t/natural-emission-tag-in-cmaq-isam-v5-4/4341/5 "2023-09-05T01:56:27Z")
Is there any way to distinguish the contribution of biogenic VOC emission and soil NO emission to O3? Is it possible to turn off online soil NO emissions calculations in CMAQ? ---
**Author:** ![hogrefe.christian](https://avatars.discourse-cdn.com/v4/letter/h/74df32/32.png) [@hogrefe.christian](https://forum.cmascenter.org/u/hogrefe.christian)\ **Post date:** [September 5, 2023, 11:46am UTC](https://forum.cmascenter.org/t/natural-emission-tag-in-cmaq-isam-v5-4/4341/6 "2023-09-05T11:46:41Z")
I think you could try using the mechanism-specific DESID control file to zero out soil NO from the MIOG inline MEGAN emission stream, something along these lines, but I haven’t tried this myself and don’t know for sure if it’d work: ``` 'EVERYWHERE', 'ALL' ,'NO' ,'NO' ,'GAS' ,1. ,'UNIT','a', 'EVERYWHERE', 'MIOG' ,'NO' ,'NO' ,'GAS' ,0. ,'UNIT','o', ``` ---
**Author:** ![wry2233](https://yyz1.discourse-cdn.com/flex027/user_avatar/forum.cmascenter.org/wry2233/32/3458_2.png) [@wry2233](https://forum.cmascenter.org/u/wry2233)\ **Post date:** [September 6, 2023, 9:09am UTC](https://forum.cmascenter.org/t/natural-emission-tag-in-cmaq-isam-v5-4/4341/7 "2023-09-06T09:09:59Z")
Thank you very much for your advice. I will try it later.