Nutrient ratios (P_C_Ratio and N_C_Ratio)

Question

Hi,

I have a simple question on the nutrient ratios provided in Chapter 8 (page 164).

The default values of 0.3 P_C_Ratio and 3.0 N_C_Ratio are too high.

It seems to me the values are multiplied by 10 approximately.

Could you check the unit or numbers for me? Thank you.

Se-Woong Chung

Chungbuk Naitonal University

Answer 1

Hi Se-Woong,

Sorry, these values (or any of the example values) are not really meant as defaults.  The model will just use what the user has given and the ratios are dimensionless (ie mg:mg).  

I can't remember now where I got these values from but it would have been an old CAEDYM configuration.

Chris

Comments

Hi Chris,
Thank you for your reply. I found that the unit is mg-P/mg-Chla not mg-P/mg-C. The variable names P_C_Ratio and N_C_Ratio made me confused. I think P_Chla_Ratio is a better name in this case.
Se-Woong

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Se-woong the variable is mg-P/mg-C (Carbon).

 There is a chance I copied the values for  mg-P/mg-Chla when doing the example.

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Chris, they used to be mg-P/mg-Chla and mg-N/mg-Chla in the old CAEDYM.
Do you mean that you have changed them to  mg-P/mg-C and mg-N/mg-C in the new water quality code in AEM3D? It is very important to make it clear this out because the value will be about 50 times different.

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Sorry, I've just read through the code and this is still consistent with CAEDYM, the value will be mg-P/mg-Chla if the phyto group is using Chla and mg-P/mg-Carbon if the phyto group is using Carbon

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Thank you for clarifying it.