NH3-N as an input

[djb14128]

Hi,

How would I write NH3-N as an input to IPHREEQC? I don't want to write it as N in the input as it doesn't want other forms of N just NH3. It won't let me write it.

I have added N(-3) in the input worksheet. But now I have to worry about NH4+, N(0), and NH4SO4-in output worksheet. They are produced in the worksheet.

How do I suppress reactions? What do I write on the input?

Kind regards,
djb14128

[dlparkhurst]

The Amm.dat database (equivalent to the phreeqc.dat database from Appelo's web site) defines a separate element Amm, which corresponds to the species NH3. Amm is a separate "element" so that it does not interact with N and its valences states. In other words, Amm cannot participate in redox reactions.

Amm has species Amm and AmmH+. I do not think you want to suppress AmmH+ because it is the predominant species under most natural conditions. However, you can suppress the species by increasing the log K in the formation reaction for Amm.

[djb14128]

Hi,

It's because I have NH3 at the beginning instead of NH4+. It gives me a value whereby the concentration of NH3 is less than NH4+.

Kind regards,
djb14128

[dlparkhurst]

I don't know what you are doing, but I do not think you want to suppress the species NH4+. If pH is high, then NH4+ will be small; but if pH is lower for some reason, then NH4+ will become an important species. Just because you start with NH3 does not mean it will always be the predominant species.

[djb14128]

Hi,

Is it also possible to determine the diffusion coefficient for an ammonia/water vapour mixture on IPHREEQC?

Kind regards,
djb14128

[dlparkhurst]

The databases phreeqc.dat, Amm.dat, and pitzer.dat have tracer diffusion coefficients for aqueous species; diffusion coefficients are for the liquid phase, not for gases.

The Basic function DIFF_C provides the diffusion coefficient for a species. Note there is an error in the documentation, and the value is for the temperature of the calculation, not 25 C.

There are additional diffusion coefficient parameters for electro-diffusion. See documentation for SOLUTION_SPECIES at https://water.usgs.gov/water-resources/software/PHREEQC/documentation/phreeqc3-html/phreeqc3.htm