Politecnico di Milano, DICA, Piazza Leonardo da Vinci, 32-20133 Milano, Italy.
Politecnico di Milano, DICA, Piazza Leonardo da Vinci, 32-20133 Milano, Italy.
Sci Total Environ. 2019 Mar 15;656:1207-1222. doi: 10.1016/j.scitotenv.2018.11.416. Epub 2018 Nov 30.
Groundwater status in highly urbanized areas is particularly affected by anthropogenic influence due to diffuse pollution deriving from many sources. This makes very often challenging to determine whether the observed groundwater conditions are the result of localized pollutant sources (PS-Point Sources). In the EU legislative framework it is accepted that, when Natural Background Levels (NBLs) of undesirable elements are proven to be higher than specific Groundwater Quality Standards (GQSs), NBLs should be assumed as GQSs. No procedure is instead defined when anthropogenic Diffuse Pollution Background levels (DBPLs) are higher than GQSs and make unfeasible any remediation strategy. Among the many contaminants affecting groundwater, the chlorinated solvents, tetrachloroethylene (PCE), trichloroethylene (TCE) and trichloromethane (TCM) among the organics and hexavalent chromium, among the inorganics, having been widely used in several industries all over Europe, are very often the most prevalent contaminants in soil and groundwater. Aim of this paper is to discuss a multivariate statistical approach to address the issue of identification of anthropogenic Diffuse Pollution Background Levels. With such aim, an area of about 1600 km, including the Functional Urban Area of Milan, was considered and 10 independent geochemical datasets, provided by local and regional agencies, and covering the period 2003-2014 were merged into a single database after homogenization and multiple quality checks. A total of 618,258 chemical analyses from 3477 sampling wells were considered, being all samples collected and analyzed through internally consistent protocols. The analysis enabled to identify five main clusters, having specific hydrogeological characteristics, different temporal profiles and pollutant background concentration levels, which were also found to respond differently to meteo-climatic changes. This study offers a robust knowledge basis for drafting a diffuse pollution management plan of the area.
高度城市化地区的地下水状况特别受到人为影响的影响，因为来自许多来源的扩散污染。这使得确定观察到的地下水状况是否是局部污染源（PS-点源）的结果变得非常具有挑战性。在欧盟立法框架中，人们接受了这样的观点，即在证明不良元素的自然背景水平（NBL）高于特定地下水质量标准（GQS）时，应将 NBL 视为 GQS。但是，当人为扩散污染背景水平（DBPL）高于 GQS 并使任何修复策略变得不可行时，没有定义任何程序。在影响地下水的众多污染物中，有机氯代溶剂四氯乙烯（PCE）、三氯乙烯（TCE）和三氯甲烷（TCM）以及无机六价铬在欧洲的许多行业中被广泛使用，它们通常是土壤和地下水中最普遍的污染物。本文旨在讨论一种多元统计方法来解决识别人为扩散污染背景水平的问题。为此，考虑了一个约 1600 平方公里的区域，包括米兰的功能城市区域，并将当地和地区机构提供的 10 个独立地球化学数据集合并到一个单一数据库中，这些数据集涵盖了 2003-2014 年期间，经过均匀化和多次质量检查。总共考虑了 3477 个采样井的 618,258 个化学分析，所有样品均通过内部一致的协议进行收集和分析。分析结果确定了五个主要集群，它们具有特定的水文地质特征、不同的时间分布和污染物背景浓度水平，并且还发现它们对气象气候变化的响应不同。这项研究为制定该地区的扩散污染管理计划提供了可靠的知识基础。
