Modeling precipitation and sorption of elements during mixing of river water and porewater in the Coeur d'Alene River basin
Modeling precipitation and sorption of elements during mixing of river water and porewater in the Coeur d'Alene River basin
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DOI：
10.1021/es0303283
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发表时间：
2003-10-15
影响因子：
11.4
通讯作者：
Tonkin, JW
中科院分区：
文献类型：
--
作者：
Balistrieri, LS;Box, SE;Tonkin, JW
在流域内每年水位下降期间，当孔隙水排入河水时，沿Coeur d 'Alene河边缘沿着形成红棕色絮体。沉淀物是溶解元素的有效清除剂，并且具有可以使与它们相关的金属生物可利用的特性。这项工作的孔隙水的地球化学特征和模型的絮凝物的形成和组成。孔隙水是微酸性的，具有亚氧至缺氧的特征，倾向于具有较高的碱度，并且相对于河水含有高浓度的许多成分。实验室混合实验，包括孔隙水和河水进行生产的沉淀物。PHREEQC的热力学预测表明，预测的水铁矿和三水铝石的量与Fe和Al的去除相一致。通过水铁矿吸附去除元素的预测与使用广义两层模型的表面络合常数组合观察到的去除相一致（As和Se），从高吸附剂-吸附剂比实验中得出的替代表面常数（Cd，Co，Cu，Ni，Pb和Zn），并调整表面常数以拟合实验数据（Cr，Mo和Sb）。这套新的表面络合常数需要在其他污染系统中进一步测试。
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.