PM2.5 concentration, splitting primary and secondary component

[enricopisoni]

Dears

we usually use, for PM2.5 concentrations, the EMEP variable named 'SURF_ug_PM25_rh50'

we need now to estimate the primary and secondary component of PM2.5 concentrations. To do so, is it ok to use:

• SURF_ug_PPM25 (as primary component of PM2.5 concentration)
• SURF_ug_PM25_rh50 - SURF_ug_PPM25 (as secondary component of PM2.5 concentration) ?

or should we do something different?

thanks bests Enrico

[svetlanat]

Well, the difference (SURF_ug_PM25_rh50 - SURF_ug_PPM25) will contain primary natural particles (sea salt and dust)

[enricopisoni]

Hi Svetlana

and thanks for your reply

so, please, could you tell me how to get the:

• primary component of PM25 concentrations
• secondary component of PM25 concentrations using the EMEP output variables?

Thanks Bests Enrico

[svetlanat]

Enrico, I do not know what output parameters you have and what you plan to do with natural PPM.

Within SURF_ug_PM25_rh50, primary PM : SURF_ug_PPM25 is anthropogenic fine PPM,
SEASALT_F and DUST_F are natural primary fine PM. ffire_BC, ffire_remPPM25 - primary PM from forest fires

[enricopisoni]

Dear Svetlana

sorry, but from the manual (https://emep-ctm.readthedocs.io/en/latest/Output.html#output-parameters-netcdf-files) it seems that 'SURF_ug_PM25_rh50' is the total PM2.5 concentrations, not the primary PM... can you confirm this?

then, what I want to know is simply if it is possible, from other EMEP variables, to split the total PM2.5 concentrations (SURF_ug_PM25_rh50) in primary and secondary PM2.5 components

thanks for your help

bests Enrico

[svetlanat]

Yes, 'SURF_ug_PM25_rh50' is the total PM2.5 concentrations. I've just listed to you the primary PM included in it. If you subtract from SURF_ug_PM25_rh50 all PPM, you'll get secondary PM25.

[enricopisoni]

ok thanks, so to get the secondary PM for PM2.5 I will do:

'secondary PM2.5' = SURF_ug_PM25_rh50 - SURF_ug_PPM25 - SEASALT_F - DUST_F - ffire_BC - ffire_remPPM25

thanks for your help bests Enrico

[svetlanat]

Yes, that would be what I'd do :) Actually, there is one more to subtract: ffire_OM.

I'll be away for 2 weeks and kind of stressed now. I'd recommend you to double check this formula with David Simpson @mifads

[mifads]

Hmm, depends on your outputs. To start from PM2.5 one would also need to subtract the background ug_OM25_BGND. An easier way might be to add ug_SIA25 + ugPM_ASOA + ugPM_BSOA? Note that some of this ug_OM25_BGND should also be secondary, and even some of the ffire_OM since we treat the emissions as inert, but maybe this includes some assumed fast SOA formation.

[svetlanat]

I was also going to suggest adding up all secondary PMs, but decided it was more "dangerous" - all of a sudden it would become incomplete, so that PPM25+secondaryPM 25 \= total PM25

[mifads]

ug_OM25_BGND is needed for mass balance if starting from PM25.