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Modeling precipitation and sorption of elements during mixing of river water and porewater in the Coeur d'Alene River basin

Environmental Science and Technology

By:
, , and
DOI: 10.1021/es0303283

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Abstract

Reddish brown flocs form along the edge of the Coeur d'Alene River when porewater drains into river water during the annual lowering of water level in the basin. The precipitates are efficient scavengers of dissolved elements and have characteristics that may make metals associated with them bioavailable. This work characterizes the geochemistry of the porewater and models the formation and composition of the flocs. Porewater is slightly acidic, has suboxic to anoxic characteristics, tends to have higher alkalinity, and contains elevated concentrations of many constituents relative to river water. Laboratory mixing experiments involving porewater and river water were done to produce the precipitates. Thermodynamic predictions using PHREEQC indicate that predicted amounts of ferrihydrite and gibbsite agree with removal of Fe and Al. Predictions of element removal by adsorption onto ferrihydrite are consistent with observed removal using a combination of surface complexation constants for the generalized two-layer model (As and Se), alternative surface constants derived from experiments at high sorbate-to-sorbent ratios (Cd, Co, Cu, Ni, Pb, and Zn), and adjusted surface constants to fit experimental data (Cr, Mo, and Sb). This new set of surface complexation constants needs further testing in other contaminated systems.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Modeling precipitation and sorption of elements during mixing of river water and porewater in the Coeur d'Alene River basin
Series title:
Environmental Science and Technology
DOI:
10.1021/es0303283
Volume
37
Issue:
20
Year Published:
2003
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Environmental Science and Technology
First page:
4694
Last page:
4701
Number of Pages:
8