Zhang Fan, Luo Wensui, Parker Jack C, Spalding Brian P, Brooks Scott C, Watson David B, Jardine Philip M, Gu Baohua
Environmental Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, MS 6038, Oak Ridge, Tennessee 37831, USA.
Environ Sci Technol. 2008 Nov 1;42(21):8007-13. doi: 10.1021/es800311m.
Many geochemical reactions that control aqueous metal concentrations are directly affected by solution pH. However, changes in solution pH are strongly buffered by various aqueous phase and solid phase precipitation/dissolution and adsorption/desorption reactions. The ability to predict acid-base behavior of the soil-solution system is thus critical to predict metal transport under variable pH conditions. This studywas undertaken to develop a practical generic geochemical modeling approach to predict aqueous and solid phase concentrations of metals and anions during conditions of acid or base additions. The method of Spalding and Spalding was utilized to model soil buffer capacity and pH-dependent cation exchange capacity by treating aquifer solids as a polyprotic acid. To simulate the dynamic and pH-dependent anion exchange capacity, the aquifer solids were simultaneously treated as a polyprotic base controlled by mineral precipitation/ dissolution reactions. An equilibrium reaction model that describes aqueous complexation, precipitation, sorption and soil buffering with pH-dependent ion exchange was developed using HydroGeoChem v5.0 (HGC5). Comparison of model results with experimental titration data of pH, Al, Ca, Mg, Sr, Mn, Ni, Co, and SO4(2-) for contaminated sediments indicated close agreement suggesting that the model could potentially be used to predictthe acid-base behavior of the sediment-solution system under variable pH conditions.
许多控制水中金属浓度的地球化学反应直接受溶液pH值影响。然而，溶液pH值的变化受到各种水相和固相沉淀/溶解及吸附/解吸反应的强烈缓冲。因此，预测土壤-溶液系统酸碱行为的能力对于预测可变pH条件下的金属迁移至关重要。本研究旨在开发一种实用的通用地球化学建模方法，以预测添加酸或碱条件下金属和阴离子在水相和固相中的浓度。利用斯波尔丁和斯波尔丁的方法，将含水层固体视为多元酸来模拟土壤缓冲容量和pH依赖的阳离子交换容量。为了模拟动态和pH依赖的阴离子交换容量，将含水层固体同时视为由矿物沉淀/溶解反应控制的多元碱。使用HydroGeoChem v5.0（HGC5）开发了一个平衡反应模型，该模型描述了水相络合、沉淀、吸附以及具有pH依赖离子交换的土壤缓冲作用。模型结果与污染沉积物的pH、Al、Ca、Mg、Sr、Mn、Ni、Co和SO4(2-)的实验滴定数据的比较表明两者吻合度高，这表明该模型有可能用于预测可变pH条件下沉积物-溶液系统的酸碱行为。
