Yidana Sandow M, Ophori Duke, Banoeng-Yakubo Bruce
Department of Earth and Environmental Studies, Montclair State University, Montclair, NJ 07043, USA.
J Environ Manage. 2008 Jan;86(1):80-7. doi: 10.1016/j.jenvman.2006.11.023. Epub 2007 Jan 16.
R-mode hierarchical cluster and principal component analysis (PCA) were simultaneously applied to surface water hydrochemical data from three different locations, Ankwaso, Dominase and Prestea, along the Ankobra Basin, Ghana, to extract principal factors corresponding to the different sources of variation in the hydrochemistry, with the objective of defining the main controls on the hydrochemistry at the basin scale. Using the Kaiser criterion, principal components (PC) were extracted from the data and rotated using varimax normalization, for each location. The varimax rotation ensured that variation in the data was maximized for easy interpretation of the results. The analysis reduced 30, 33 and 33 data points, respectively, for Ankwaso, Dominase and Prestea to four, three and four PC representing the sources of variation in the hydrochemistry at the three different locations. Though the PC analysis proved to be more robust at unveiling the sources of variation in the hydrochemistry than the R-mode hierarchical cluster analysis (HCA), the combined use of both techniques resulted in more reliable interpretations of the hydrochemistry. On the basis of these analyses, the hydrochemistry of the basin is controlled largely by the weathering of minerals (silicates, carbonates, gypsum and apatite) from the underlying meta-sediments of the Birimian and Tarkwaian Systems, and the decay of organic matter from the heavily forested regions. Concentrations of the major chemical parameters are within naturally acceptable limits and do not pose threats to the local ecology and humans. There is no strong evidence of high anthropogenic impacts on the major anions and cations used for this research, though there are variations at the different locations studied. The hydrochemistry at Ankwaso is principally controlled by the weathering of silicate minerals, whereas those of Dominase and Prestea are, respectively, influenced by precipitation and domestic wastewaters, and the decay of organic matter.
R 型层次聚类分析和主成分分析（PCA）同时应用于加纳安科布拉河流域三个不同地点（安夸索、多米纳塞和普雷斯蒂亚）的地表水水化学数据，以提取与水化学中不同变异来源相对应的主要因素，目的是确定流域尺度下水化学的主要控制因素。根据凯泽准则，从数据中提取主成分（PC），并对每个地点使用方差最大化正交旋转法进行旋转。方差最大化旋转确保数据中的变异最大化，以便于结果解释。该分析分别将安夸索、多米纳塞和普雷斯蒂亚的 30、33 和 33 个数据点减少为四个、三个和四个主成分，这些主成分代表了三个不同地点水化学的变异来源。尽管主成分分析在揭示水化学变异来源方面比 R 型层次聚类分析（HCA）更稳健，但两种技术的结合使用能对水化学做出更可靠的解释。基于这些分析，该流域的水化学主要受比里米安系和塔尔夸安系下伏变质沉积物中矿物（硅酸盐、碳酸盐、石膏和磷灰石）的风化以及森林茂密地区有机物腐烂的控制。主要化学参数的浓度在自然可接受的范围内，对当地生态和人类不构成威胁。尽管在所研究的不同地点存在差异，但没有强有力的证据表明本研究中使用的主要阴离子和阳离子受到高人为影响。安夸索的水化学主要受硅酸盐矿物风化的控制，而多米纳塞和普雷斯蒂亚的水化学分别受降水和生活污水以及有机物腐烂的影响。
