[OLD] Header part

[webmaster]

From: Yoshida Yasushi

Subject: header part

I have one question for the GWB database. n the header part of the Database, the data of c co2 1, c co2 2, c co2 3, c co2 4, c h2o 1, c h2o2, c h2o3 and c h2o4 are listed. n the GWB users' guide (p.172), c co2 1, c co2 2, c co2 3 and c co2 4 are the data for ' coefficients for calculating the activity coefficients for CO2 and some other electrically neutral species' and 'c h2o 1, c h2o2, c h2o3 and c h2o4' are the data for coefficients for calculation the activity of water', however there is no exact description for these data. would like to know the meaning of these coefficients.

* c co2 1

1.224e-1 1.127e-1 9.341e-2 8.018e-2

8.427e-2 9.892e-2 1.371e-1 1.967e-1

* c co2 2

-4.679e-3 -1.049e-2 -3.600e-3 -1.503e-3

-1.184e-2 -1.040e-2 -7.086e-3 -1.809e-2

* c co2 3

-4.114e-4 1.545e-3 9.609e-5 5.009e-4

3.118e-3 1.386e-3 -2.887e-3 -2.497e-3

* c co2 4

0. 0. 0. 0.

0. 0. 0. 0.

* c h2o 1

500. 1.45397 500. 1.55510

1.6225 500. 500. 500.

* c h2o 2

500. 2.2357e-2 500. 3.6478e-2

4.5891e-2 500. 500. 500.

* c h2o 3

500. 9.3804e-3 500. 6.4366e-3

4.5221e-3 500. 500. 500.

* c h2o 4

500. -5.362e-4 500. -7.132e-4

-8.312e-4 500. 500. 500.

From: Craig Bethke

Subject: Re: header part

The equations used for these calculations are listed on pages 111-114 of the “Geochemical Reaction Modeling� text. In case you're interested, I've listed at the bottom of this message the actual lines of code used to calculate these parameters.

 

tist = min(Tionst, Timax);

sist = min(Sionst, Simax);

// Set water activity, using method of Helgeson et al. (1970).

 

rootsi = sqrt(sist);

bhat = 1.0 + Bh2o[0]*rootsi;

capj = bhat - 2.0*log(bhat) - 1.0/bhat;

capd = 2.302590*Adh/(pow(Bh2o[0], 3)*sist);

osmot = 1.0 - capd*capj + Bh2o[1]*sist/2.0

+

2.0*Bh2o[2]*sist*sist/3.0

+

3.0*Bh2o[3]*sist*sist*sist/4.0;

awlog = -2.0*sist*osmot/(2.30259*55.508682);

Bas[H2O]-gamma = pow(10.0, awlog);

 

// Set activity coefficients for certain neutral aqueous species.

 

rootti = sqrt(tist);

algco2 = (Cco2[0]+(Cco2[1]+(Cco2[2]+Cco2[3]*tist)*tist)*tist)*tist;

aco2 = pow(10.0, algco2);