Hi,
I am trying to simulate the concentration of NO3N in the soil profile at different depths due to the application of liquid hog manure. I know that hydrus gives out the concentration of solutes in the units mmol/cm3. However, I have the observed data in the units mg/kg which is the concentration of solute in soil. Is there any way I can compare the observed and simulated data ?
Simrat
Concentration units
Re: Concentration units
In HYDRUS you can actually use any concentration units for concentrations in the liquid phase you want, e.g., dimensionless, g/L, mmol/L, mmol/cm3, etc. Since the governing convectiondispersion equation is linear (unless you consider nonlinear sorption), the final results are the same no matter what units you use, as long as they are consistent between initial and boundary concentrations, and (zeroorder) reaction constants. If you have observed concentration data in mg/kg(of soil), you need to convert them to mg/Volume(of soil), i.e., in total concentrations, and then you can use them as well, providing that indicate that (i.e., in Solute Transport Boundary Conditions window you indicate that Initial Conditions are in total concentrations).Hydrus will then distribute solute mass between different phases based on the distribution coefficients.
J.
J.

 Posts: 9
 Joined: Thu Aug 20, 2015 5:07 pm
 Location: Canada
Re: Concentration units
Hello Jirka,
I've an another question regarding the units for root solute uptake. Since the concentration units of input and results are consistent in Hydrus 1D. Lets assume if I input the liquid phase initial concentrations of nitrate in mg/l and if I also consider the root solute uptake, then what would be the units of root solute uptake ? I can see it in mg/cm2 in my results. So shall I just multiply the root solute uptake by 100 to get the results in mg/ha ? I'm a bit confused.
I've an another question regarding the units for root solute uptake. Since the concentration units of input and results are consistent in Hydrus 1D. Lets assume if I input the liquid phase initial concentrations of nitrate in mg/l and if I also consider the root solute uptake, then what would be the units of root solute uptake ? I can see it in mg/cm2 in my results. So shall I just multiply the root solute uptake by 100 to get the results in mg/ha ? I'm a bit confused.
Re: Concentration units
Root Water Uptake (nodal), S: [L3L3T1]= [T1]
Transpiration, S*depth: [L3L3T1][L]= [T1] [L]= [L T1]
Cumulative root water uptake (cumulative transpiration), S*depth*time: [L3L3T1][L][T]= [L3L2]=[L]
Concentration, c: [ML3]
Solute Uptake (nodal), Sc: [L3L3T1][ML3]=[ML3T1]
Solute Uptake (profile), Sc*depth: [ML3T1][L]= [ML2T1]
Cumulative solute uptake (profile) , Sc*depth*time: [ML2T1][T]= [ML2]
Transpiration, S*depth: [L3L3T1][L]= [T1] [L]= [L T1]
Cumulative root water uptake (cumulative transpiration), S*depth*time: [L3L3T1][L][T]= [L3L2]=[L]
Concentration, c: [ML3]
Solute Uptake (nodal), Sc: [L3L3T1][ML3]=[ML3T1]
Solute Uptake (profile), Sc*depth: [ML3T1][L]= [ML2T1]
Cumulative solute uptake (profile) , Sc*depth*time: [ML2T1][T]= [ML2]
Re: Concentration units
Dear Hydrus users
I would like to insert an initial concentration of a pollutant in the profile graphical editor (Hydrus 1D). My measured concentrations are in mg/kg. Am I right if I do this using the following procedure:
 Solute transport general information: change mass units to mg
 Transport boundary conditions: change initial condition to 'in total concentrations mass solute/volume soil'
 Soil profile graphical editor  initial conditions concentration: now I can insert my initial concentration in mg/l soil ?
Thank you in advance for your reply
Lotte
I would like to insert an initial concentration of a pollutant in the profile graphical editor (Hydrus 1D). My measured concentrations are in mg/kg. Am I right if I do this using the following procedure:
 Solute transport general information: change mass units to mg
 Transport boundary conditions: change initial condition to 'in total concentrations mass solute/volume soil'
 Soil profile graphical editor  initial conditions concentration: now I can insert my initial concentration in mg/l soil ?
Thank you in advance for your reply
Lotte
Re: Concentration units
The default input for initial concentrations is “liquid phase concentrations”, which is in [mass/volume of water, which are standard concentration units]. Alternatively, one can enter as an initial condition “total concentrations”, which are in units of [mass of solute per volume of soil]. The latter option needs to be selected in the “Solute transport – Boundary Conditions” dialog window. If the latter option is selected, the total concentration is then divided into different phases (liquid, solid, gas).
If your measured concentration is in [mg/kg], you need to convert this value into units use by Hydrus using either dry or wet bulk density (depending on your measurements).
J.
If your measured concentration is in [mg/kg], you need to convert this value into units use by Hydrus using either dry or wet bulk density (depending on your measurements).
J.