diolution of Air composition

["Yong Wang" <ywang2@xxxxxxxxxxxxxx>]

Mr. Parkhurst:

Hi, how are you !

I am very appreciated of your help on my question last time . I don't know
if you had time to think over the question on caron dioxide. I remembered
that you said you were out of town for two weeks. I sent a email to you then
and i am not sure if you got it.

So I here sum it up in this way:

I am trying to simulate the disolution of the gas composition of air in
solution which is bubbled with a humidified air in lab experimental
condition. The concentration of carbonate is unknown.

I tried to set the initial data in

GAS_PHASE 1  Air
     		-fixed_pressure
		-pressure 		1.0
      	-temperature    25.0
		CO2(g)          0.000316
		O2(g)           0.2
		N2(g)           0.78

as well as

EQUILIBRIUM_PHASES 1
        Fix_H+   -8.0   NaOH    10.0
	CO2(g)	-3.5
	O2(g)       -0.69897
	N2(g)       -0.1079

The pH are set as fixed from 2-10.

There are 1 mg/l U in the soultion and adsortion by iron oxide are allowed
too.

The first one comes out with the carbonate distribution as shown in attached
file while the second one doesn't converge. I tried the KNOBS data but
didn't work. Butwhen I took away the O2(g) and N2(g) from the data set, it
gave a fairly good result.

Here is my questions:

1. which one data set should i use to represent the experimental condition ?

2. I used the Fixed_H+ for constant pH. In order to keep the acid-base and
calculation balance, I need to assumed some acid or base present as Manual
recommended. Don't  they influence the chemical reaction, such as to
increase or decrease the dissolution of CO2 ? how to avoid using the assumed
acid or base ? Any advices if necessary?

Thanks a lot for your precious time and help.

Yours sincerely,


Young Wang
Department of Geology
SUNY-Binghamton

Attachment: question.doc
Description: MS-Word document