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Reactive transport of metal contaminants in alluvium - Model comparison and column simulation

Applied Geochemistry

By:
, , and
DOI: 10.1016/S0883-2927(99)00004-9

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Abstract

A comparative assessment of two reactive-transport models, PHREEQC and HYDROGEOCHEM (HGC), was done to determine the suitability of each for simulating the movement of acidic contamination in alluvium. For simulations that accounted for aqueous complexation, precipitation and dissolution, the breakthrough and rinseout curves generated by each model were similar. The differences in simulated equilibrium concentrations between models were minor and were related to (1) different units in model output, (2) different activity coefficients, and (3) ionic-strength calculations. When adsorption processes were added to the models, the rinseout pH simulated by PHREEQC using the diffuse double-layer adsorption model rose to a pH of 6 after pore volume 15, about 1 pore volume later than the pH simulated by HGC using the constant-capacitance model. In PHREEQC simulation of a laboratory column experiment, the inability of the model to match measured outflow concentrations of selected constituents was related to the evident lack of local geochemical equilibrium in the column. The difference in timing and size of measured and simulated breakthrough of selected constituents indicated that the redox and adsorption reactions in the column occurred slowly when compared with the modeled reactions. MINTEQA2 and PHREEQC simulations of the column experiment indicated that the number of surface sites that took part in adsorption reactions was less than that estimated from the measured concentration of Fe hydroxide in the alluvium.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Reactive transport of metal contaminants in alluvium - Model comparison and column simulation
Series title:
Applied Geochemistry
DOI:
10.1016/S0883-2927(99)00004-9
Volume
15
Issue:
1
Year Published:
2000
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Applied Geochemistry
First page:
35
Last page:
49
Number of Pages:
15