Yidana Sandow Mark, Ophori Duke, Banoeng-Yakubo Bruce
Department of Earth and Environmental Studies, Montclair State University, NJ 07043, USA.
J Environ Manage. 2008 Sep;88(4):697-707. doi: 10.1016/j.jenvman.2007.03.037. Epub 2007 May 11.
Inverse geochemical modeling from PHREEQC, and multivariate statistical methods were jointly used to define the genetic origin of chemical parameters of groundwater from the Voltaian aquifers in the Afram Plains area. The study finds, from hierarchical cluster analysis that there are two main hydrochemical facies namely the calcium-sodium-chloride-bicarbonate waters and the magnesium-potassium-sulfate-nitrate waters in the northern and southern sections, respectively, of the Afram Plains area. This facies differentiation is confirmed by the distribution of the SO(4)(2-)/Cl(-) ratio, which associates groundwater from the northern and southern sections to areas influenced by contact with evaporites and seawater, respectively. Principal component analysis (PCA) with varimax rotation using the Kaiser criterion identifies four principal sources of variation in the hydrochemistry. Mineral saturation indices calculated from both major ions and trace elements, indicate saturation-supersaturation with respect to calcite, aragonite, k-mica, chlorite, rhodochrosite, kaolinite, sepiolite, and talc, and undersaturation with respect to albite, anorthite, and gypsum in the area. Inverse geochemical modeling along groundwater flowpaths indicates the dissolution of albite, anorthite and gypsum and the precipitation of kaolinite, k-mica, talc, and quartz. Both the PCA and inverse geochemical modeling identify the incongruent weathering of feldspars as the principal factors controlling the hydrochemistry in the Afram Plains area. General phase transfer equations have been developed to characterize the geochemical evolution of groundwater in the area. A very good relationship has been established between calcite and aragonite saturation indices in the Afram Plains area, with R(2)=1.00.
利用PHREEQC进行逆地球化学模拟，并结合多元统计方法来确定阿夫拉姆平原地区沃尔特含水层地下水化学参数的成因。该研究通过层次聚类分析发现，阿夫拉姆平原地区北部和南部分别存在两种主要水化学相，即钙 - 钠 - 氯化物 - 碳酸氢盐水和镁 - 钾 - 硫酸盐 - 硝酸盐 水。这种相的分化通过SO(4)(2 - )/Cl(-)比值的分布得到证实，该比值分别将北部和南部的地下水与受蒸发岩和海水接触影响的区域联系起来。使用凯泽准则进行方差最大化旋转的主成分分析（PCA）确定了水化学变化的四个主要来源。根据主要离子和微量元素计算的矿物饱和指数表明，该地区方解石、文石、钾云母、绿泥石、菱锰矿、高岭石、海泡石和滑石呈饱和 - 过饱和状态，而钠长石、钙长石和石膏呈不饱和状态。沿地下水流路径的逆地球化学模拟表明钠长石、钙长石和石膏的溶解以及高岭石、钾云母、滑石和石英的沉淀。PCA和逆地球化学模拟均确定长石的不一致风化是控制阿夫拉姆平原地区水化学的主要因素。已开发出通用的相转移方程来描述该地区地下水的地球化学演化。阿夫拉姆平原地区方解石和文石饱和指数之间建立了非常好的关系，R(2)=1.00。
