CMAQ5.3.1: how can we calculate the dust PM2.5 concentration?

Hi,

My question is a bit similar than the one posted in https://forum.cmascenter.org/t/questions-on-windblown-dust-and-pm10-calculation-by-cmaq/1750; but I do not find the useful information in the replies.

Is it possible to calculate the dust contribution in PM2.5 as we can calculate the SIA or other components with the combine postprocessing script?

For example, Foroutan et al. (2017) (doi:10.1002/2016MS000823) does not show « dust » concentrations and to illustrate a dust plume, this website (Windblown Dust in CMAQ | CMAQ: The Community Multiscale Air Quality Modeling System | US EPA) only presents the ASOILJ concentrations.

Does it mean PM25_SOIL corresponds to the PM25 dust ?

I use CMAQv5.3.1.

Best regards,
Matthieu

Hello Matthieu,

I think you are asking whether there is a way to isolate and quantify the contribution of windblown dust emissions to the PM concentrations in the standard CMAQ output files. If that is the question, the answer is that generally this is not possible.

The reason for this is that the crustal species emitted in the windblown dust module (see table dust_spc on lines 426 - 456 of AERO_DATA.F) are also emitted from certain anthropogenic primary PM sources. Put differently, none of the CMAQ PM concentration species is a unique tracer for windblown dust emissions.

That said, depending on the relative abundance of windblown dust emissions and anthropogenic primary PM emissions in a given area and time period, the “ASOILJ” combination defined in combine as combination of AALJ, ASIJ, ACAJ, AFEJ, and ATIJ and/or the CMAQ species AOTHRJ can be used as a proxy for concentration variations caused by windblown dust emissions if windblown dust emissions of these species in the area and time period of interest dominate over anthropogenic sources. The ASOILJ quantify has the added advantage that it can be compared to an equivalent observed quantify derived from the same trace elements measured at PM speciation monitors. This was the approach taken in the Foroutan et al. (2017) study that focused on areas and time periods heavily influenced by windblown dust emissions.

To directly quantify the contribution of windblown dust emissions to ambient PM concentrations, you would want to employ ISAM configured to track windblown dust emissions and/or perform a brute force sensitivity simulation in which you zero out primary PM emissions from all sources except windblown dust.

I apologize if I misunderstood your question.

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Thank you very much.
Yes, you have understood my question. This is helpful!