Abstract The presence of naturally occurring contaminants in groundwater is a public health concern in rural areas of northeastern North America, where public and private wells are important sources of drinking water. In southern Quebec (Canada), inorganic groundwater chemistry data have been recently collected following standard procedures in several regional hydrogeological projects implemented by the government of Quebec. In this study, a groundwater chemistry database was compiled from 16 regional projects altogether covering an area of approximately 100,000 km2. The database includes information on water supply infrastructures, geological settings, hydrogeological conditions and inorganic water chemistry for 2369 water samples. Samples were mostly collected from private domestic wells, and to a lesser extent from municipal and observation wells. The data revealed that fluoride, barium, manganese and arsenic are the most common elements exceeding Canadian drinking water guidelines. Exploratory data analysis techniques were applied to selected subsets of data to gain insight into the sources and distribution of these hazardous groundwater contaminants. These exploratory methods include graphical data analysis (maps, Piper and empirical cumulative distribution function plots), multivariate compositional data analysis (clustering and correlation analysis) and geochemical modeling (saturation index calculations). The results suggest that fluoride, barium, manganese and arsenic are all derived from natural sources. Elevated fluoride concentrations are mainly associated with dilute Ca–Na–HCO3 bedrock groundwaters from granitic areas (Grenville Province), and more geochemically evolved Na–HCO3 to Na–HCO3–Cl bedrock groundwaters from shale areas (St. Lawrence Platform). High-F groundwaters are generally characterized by low Ca concentrations ( 8), suggesting that F is mainly controlled by fluorite (CaF2) precipitation and anion exchange with OH−. Barium is present at elevated concentrations in mineralized Ca–Na–HCO3, Na–HCO3 to Na–HCO3–Cl waters from bedrock aquifers of the St. Lawrence Lowlands. These groundwaters are mainly chemically evolved, strongly reducing waters occurring in confined aquifers and near major faults, which appear to correspond to discharge areas for deep regional flow. High Ba concentrations are generally associated with very low SO4 concentrations (

中文翻译：

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一种探索性数据分析方法，用于评估魁北克南部（加拿大）地下水中天然污染物（F、Ba、Mn、As）的来源和分布

摘要 地下水中天然污染物的存在是北美东北部农村地区的一个公共卫生问题，那里的公共和私人水井是重要的饮用水源。在魁北克南部（加拿大），最近根据魁北克政府实施的几个区域水文地质项目的标准程序收集了无机地下水化学数据。在这项研究中，地下水化学数据库由 16 个区域项目汇编而成，总面积约为 100,000 平方公里。该数据库包括 2369 个水样的供水基础设施、地质环境、水文地质条件和无机水化学信息。样本主要是从国内私人水井中采集的，以及在较小程度上来自市政和观测井。数据显示，氟化物、钡、锰和砷是超过加拿大饮用水准则的最常见元素。探索性数据分析技术被应用于选定的数据子集，以深入了解这些危险地下水污染物的来源和分布。这些探索性方法包括图形数据分析（地图、Piper 和经验累积分布函数图）、多元成分数据分析（聚类和相关分析）和地球化学建模（饱和指数计算）。结果表明，氟化物、钡、锰和砷均来自天然来源。氟化物浓度升高主要与花岗岩地区（格伦维尔省）的稀释 Ca-Na-HCO3 基岩地下水有关，以及更多地球化学演化的 Na-HCO3 到来自页岩地区的 Na-HCO3-Cl 基岩地下水（圣劳伦斯平台）。高 F 地下水通常以低 Ca 浓度为特征 (8)，表明 F 主要受萤石 (CaF2) 沉淀和与 OH− 的阴离子交换控制。钡在来自圣劳伦斯低地基岩含水层的矿化 Ca-Na-HCO3、Na-HCO3 到 Na-HCO3-Cl 水中的浓度升高。这些地下水主要是化学演化的，大大减少了承压含水层和主要断层附近的水，这些水似乎对应于深层区域流的排放区。