Fate of Al+++ in environment

[AdamL]

In south west of Western Australia there are naturally occurring acid saline groundwaters (pH<4, TDS> 30000 mg/L). The surface water can be alkaline and saline through various reduction reactions. With the clearing of native vegetation for agriculture, it has increased recharge to groundwater, watertables have risen and increased baseflow to surface water bodies. With the increase of baseflow of acid saline groundwaters to some surface waters, it has led to acidification of these water bodies. I am trying to simulate the process of acidification of surface waters by gradually adding acid saline groundwater solution to a surface water solution and modelling the changes in water quality. I am interested in the fate of metals particularly Al+++ due to its environmental toxicity. Can this be done?

 

acid Groundwater (in mg/l)

Ca++ 132

Mg++ 1355

Na+ 12500

K+ 241

SO4-- 2960

Cl- 20400

Br- 42

Al total 122

Fe total 37

Mn total 0.94

pH 3.48

 

Surface waters

Ca++ 454

Mg++ 2490

Na+ 18300

K+ 249

HCO3- 265

SO4-- 4380

Cl- 30400

pH 8.1

O2(aq) 1.36

[Tom Meuzelaar]

Hi Adam:

 

You can do this using React, a simple mixing model, and the Pickup command. First add your acid groundwater to the React Basis. Speciate this water, and use the Config - Pickup - Reactants command to load the speciated water into the Reactants tab. Next load your surface water into the Basis tab. You now have a model simulating gradual titration of acidic groundwater into surface water.

 

You'll run into a problem due to the fact that your surface water does not have all the components of your acid groundwater (Br-, Al, Fe, Mn). Remedy this by either excluding these components from your acid groundwater analysis, or by adding acceptably low concentrations for these components to your surface water in the Basis.

 

I hope that helps,

 

Tom Meuzelaar

RockWare, Inc.