Soil-air exchange in stage

How to consider the soil-air exchange of other pollutants in STAGE, and which parameters need to be modified?

Can you clarify what pollutants you were interested in, and also provide a description of your use case?

For your reference, please see the following description of STAGE in this paper, see section 2.2.2

2.2.2 Surface Tiled Aerosol and Gaseous Exchange (STAGE) deposition model

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Thank you for your help!

I am interested in polycyclic aromatic hydrocarbons(PAHs) and phthalates(PAEs). I have added these two species to CMAQv5.3.2. Since these two types of compounds are semi-volatile, there is a process of re-volatility from the soil. But I currently find it difficult to add their air–surface exchange process to CMAQ because I cannot get their concentration and emission information in the soil. My current plan is to test the impact of surface volatilization on PAHs and PAEs by turning off the dry deposition of PAHs and PAEs in the gas phase. I currently use M3dry. Of course, this is unreasonable, and the re-evaporation of the surface may not completely offset the subsidence process.

In the manual of CMAQ5.3, I saw “In this modeling framework, it is possible to consider bidirectional exchange for any species by providing a parametrization or constant that sets the stomatal, cuticular, soil and/or water compensation point as a value greater than 0.”

I am not sure whether they can be added to the air–surface exchange process by a simple method. If the soil concentration is not provided in the simulation, whether the soil concentration can be balanced by simulating a few days in advance and then the exchange flux can be calculated.

Bidirectional species can be added in STAGE in a couple of steps.

  1. Get the index values for the species in INIT_STAGE in STAGE_MOD.F, this is in the maploop lines 218 to 246.
  2. Create a conditional to set the soil concentration after line 443 in STAGE_MOD.F, e.g.

If( s .eq. s_PAH) Then
C_grnd = soil_pah_function or constant
End If

To test this out I would fist set C_grnd to some reasonable constant and then set it to a function, e.g. as you suggested a few days simulation to accumulate soil PAH or perhaps a c* type function. This will not change the deposition velocity and the emissions will not be currently captured in the output. Emissions will be stored in the bidi_emis array and can be output following the example or NH3_Emiss.

I am currently trying to make this process easier and would be happy to help out where I can.

Take care,


Hahahahaha, I will try it in my future research.
Thanks for your help.