A simple reactive-transport model of calcite precipitation in soils and other porous media
A simple reactive-transport model of calcite precipitation in soils and other porous media
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DOI：
10.1016/j.gca.2015.05.017
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发表时间：
2015-09
影响因子：
5
通讯作者：
G. Kirk;A. Versteegen;K. Ritz;A. Milodowski
中科院分区：
文献类型：
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作者：
G. Kirk;A. Versteegen;K. Ritz;A. Milodowski
土壤和其他多孔介质中的方解石形成通常发生在反应物的局部来源周围，例如植物根或土壤大孔，并且速率取决于反应物进出沉淀区的运输以及沉淀反应本身的动力学。然而，大多数研究都是在充分混合的系统中进行的，在这种系统中，这种传输限制在很大程度上被消除了。我们开发了一个数学模型的方解石沉淀附近的土壤中的基地来源，允许运输限制和沉淀动力学。我们测试了该模型对实验确定的方解石沉淀率和反应物的浓度-距离曲线在土壤柱与一层HCO 3 −-饱和交换树脂接触。模型参数值独立确定。考虑到实验的局限性，观测结果和预测结果之间的一致性是令人满意的，表明该模型正确地描述了重要的过程。敏感性分析表明，所有的模型参数都很重要，这表明简单的处理是不够的。敏感性分析表明，方解石沉淀量和沉淀区的扩展对反应物输运速率的控制参数（土壤含水量、含盐量、pH值、pH缓冲能力和CO2压力）以及沉淀速率常数敏感。我们说明了实际应用的模型与两个例子：pH值的变化和CaCO 3沉淀在土壤中的植物根周围，周围的土壤大孔含有一个来源的基地，如尿素。
Calcite formation in soils and other porous media generally occurs around a localised source of reactants, such as a plant root or soil macro-pore, and the rate depends on the transport of reactants to and from the precipitation zone as well as the kinetics of the precipitation reaction itself. However most studies are made in well mixed systems, in which such transport limitations are largely removed. We developed a mathematical model of calcite precipitation near a source of base in soil, allowing for transport limitations and precipitation kinetics. We tested the model against experimentally-determined rates of calcite precipitation and reactant concentration–distance profiles in columns of soil in contact with a layer of HCO3−-saturated exchange resin. The model parameter values were determined independently. The agreement between observed and predicted results was satisfactory given experimental limitations, indicating that the model correctly describes the important processes. A sensitivity analysis showed that all model parameters are important, indicating a simpler treatment would be inadequate. The sensitivity analysis showed that the amount of calcite precipitated and the spread of the precipitation zone were sensitive to parameters controlling rates of reactant transport (soil moisture content, salt content, pH, pH buffer power and CO2pressure), as well as to the precipitation rate constant. We illustrate practical applications of the model with two examples: pH changes and CaCO3precipitation in the soil around a plant root, and around a soil macro-pore containing a source of base such as urea.