Multivariate statistical analysis of geochemical data as indicative of the hydrogeochemical evolution of groundwater in a sedimentary rock aquifer system
Multivariate statistical analysis of geochemical data as indicative of the hydrogeochemical evolution of groundwater in a sedimentary rock aquifer system
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DOI：
10.1016/j.jhydrol.2008.02.015
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发表时间：
2008-05-30
影响因子：
6.4
通讯作者：
Savard, Martine M.
中科院分区：
文献类型：
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作者：
Cloutier, Vincent;Lefebvre, Rene;Savard, Martine M.
魁北克省古生代 Basses-Laurentides 沉积岩含水层系统的地下水水文地球化学研究产生了大型地球化学数据集。在 1500 km(2) 研究区域的 153 个地点采集了地下水样本，并分析了主要和次要离子。大量数据可能导致结果的整合、解释和表示困难。将两种多元统计方法，即层次聚类分析 (HCA) 和主成分分析 (PCA) 应用于数据集的子组，以评估它们对地下水样本进行分类和识别控制地下水地球化学的地球化学过程的有用性。该子组由 144 个样品和 14 个参数组成（Ca2+、Mg2+、Na+、K+、HCO3-、Cl-、SO42-、Fe2+、Mn2+、Br-、Sr2+、F-、Ba2+、HS-）。七个地球化学上不同的簇，C1-C7，由 HCA 产生。 C3、C4、C6 和 C7 簇的样本大多位于优先补给区。这些样品中的大多数含有 Ca-Mg-HCO3 补给地下水（C3、C6、C7）和 Na-HCO3 演化地下水（C4）。其他三个簇（C1、C2、C5）的样本是受限条件下含水层系统的特征。这些样品中的大多数含有 Na-HCO3 演变的地下水（C1、C5）和 Na-Cl 古代地下水，其 Br-(C2) 浓度升高。除了认识到水文地质条件对地下水地球化学的重要性外，簇的分布还表明了地质构造对微量元素和微量元素（如Fe2+、Mn2+、Sr2+、F-和Ba2+）的重要性。 PCA 的前五个分量占数据集中总方差的 78.3%。分量 1 由 Na+、Cl- 和 Br- 的高正负载定义，与地下水与尚普兰海水的混合以及来自海洋粘土弱透水层的溶质扩散有关。组分 2 中 Ca2+ 和 Mg2+ 的高正负载表明该含水层系统中碳酸盐岩溶解的重要性。根据其特征负载，前两个分量分别定义为“盐度”和“硬度”分量。第 3-5 部分与更多的局部和地质影响有关。 HCA 和 PCA 的集成以及地下水类型的常规分类。与水文地质和地质背景一样，将该区域划分为四个主要地球化学区域，从而更好地了解含水层系统动态和地下水水文地球化学演化的区域图景。以下因素被认为影响每个地球化学区域中确定的地下水的演化：（1）地质特征，包括沉积岩类型和耕层矿物学； (2)以围堵程度和水力梯度为代表的水文地质特征； （3）地质历史，包括最近的冰川作用和尚普兰海入侵。通过综合方法，这项水文地球化学研究有助于复杂地下水流系统的表征和理解，并提供了在海水入侵的重大扰动后水文地质系统长期地球化学演化的例子。 (c) 2008 Elsevier B.V. 保留所有权利。
The study of groundwater hydrogeochemistry of the Paleozoic Basses-Laurentides sedimentary rock aquifer system in Quebec produced a Large geochemical dataset. Groundwater samples were collected at 153 sites over a 1500 km(2) study area and analyzed for major and minor ions. The large number of data can lead to difficulties in the integration, interpretation and representation of the results. Two multivariate statistical methods, hierarchical cluster analysis (HCA) and principal components analysis (PCA), were applied to a subgroup of the dataset to evaluate their usefulness to classify the groundwater samples, and to identify geochemical processes controlling groundwater geochemistry. This subgroup consisted of 144 samples and 14 parameters (Ca2+, Mg2+, Na+, K+, HCO3-, Cl-, SO42-, Fe2+, Mn2+, Br-, Sr2+, F-, Ba2+, HS- ). Seven geochemically distinct clusters , C1-C7, resulted from the HCA. Samples from clusters C3, C4, C6 and C7 are mostly located in preferential recharge areas. The majority of these samples have Ca-Mg-HCO3 recharge groundwater (C3, C6, C7) and Na-HCO3 evolved groundwater (C4). Samples from the other three clusters (C1, C2, C5) are characteristic of an aquifer system under confined conditions. The majority of these samples have Na-HCO3 evolved groundwater (C1, C5) and Na-Cl ancient groundwater that exhibits elevated concentrations in Br-(C2). In addition to recognizing the importance of hydrogeological conditions on groundwater geochemistry, the distribution of clusters also showed the importance of the geological formations on minor and trace elements, such as Fe2+, Mn2+, Sr2+, F- and Ba2+. The first five components of the PCA account for 78.3% of the total variance in the dataset. Component 1 is defined by highly positive loadings in Na+, Cl- and Br- and is related to groundwater mixing with Champlain Sea water and solute diffusion from the marine clay aquitard. The high positive loadings in Ca2+ and Mg2+ of component 2 suggest the importance of dissolution of carbonate rocks in this aquifer system. From their characteristic loadings, the first two components are defined as the "salinity" and "hardness" components, respectively. Components 3-5 are related to more local and geological effects. The integration of the HCA and the PCA, with conventional classification of groundwater types, as well. as with the hydrogeological and geological contexts, allowed the division of the region into four main geochemical areas, providing an improved regional picture of the aquifer system dynamics and hydrogeochemical evolution of groundwater. The following factors were recognized as influencing the evolution of groundwater identified in every geochemical area: (1) geological characteristics including sedimentary rock type and till mineralogy; (2) hydrogeological characteristics represented by the level of confinement and the hydraulic gradient; and (3) the geological history including the latest glaciation and the Champlain Sea invasion.With its integrated approach, this hydrogeochemical study contributes to the characterization and understanding of complex groundwater flow systems, and provides an example of the long-term geochemical evolution of hydrogeological systems after a major perturbation in this case seawater invasion. (c) 2008 Elsevier B.V. All rights reserved.