Multi-isotope approaches : towards taking into account cumulative impacts of contaminants on groundwater

在加拿大，环境影响评估对批准工业项目至关重要。传统上，一个地区不同项目的影响是以个人为基础进行评估的。然而，随着经济发展和气候变化对生态系统和水资源造成越来越大的压力，我们显然必须考虑到环境影响在空间和时间上的累积特征。这是一个新兴的研究领域，未来将在加拿大发挥重要作用(加拿大科学院理事会，2019)，并承诺为子孙后代更好地保护环境。现在解决这一问题将使加拿大在可持续发展方面处于世界领先地位。在这个早期阶段，至关重要的是制定一个健全的科学框架，提高我们考虑累积影响的能力。事实上，在给定的工业背景下，我们必须能够回答以下问题：1)该地区污染物的潜在来源是什么？2)我们是否了解这些污染物的迁移路径，以便我们知道从哪里寻找这些污染物？3)我们是否能够区分环境中同一污染物的不同来源？4)我们能否预测生态系统对污染物随时间和空间积累的反应？在这项研究计划的第一个5年周期中，我的目标是为回答上述前三个问题做出重大贡献，具体污染物从深层地质构造(&gt；500米)垂直迁移到浅层含水层(&lt；200米)。实际上，淡水含水层处于“三明治”的中心位置，它包括上方(例如道路除冰盐、化肥)和下方(例如采矿、碳氢化合物生产)的污染源。虽然来自上方的污染物受到了相当大的关注，但来自下方的污染物在很大程度上被忽视了，主要是因为它们所经过的深层迁移路径很难研究。更准确地说，HQP领导的活动将允许表征地下矿山爆破作业中污染物(主要是硝酸盐)的释放。到目前为止，这种地下硝酸盐来源的记录非常少。研究活动还将以改进卤水来源识别方法为目标，卤水通常与深部地质构造有关。最后，将利用最近编制的数据库，开始筛选自然连接魁北克深层和浅部地质构造的优先迁徙路径，以评估哪些含水层受到深层工业活动污染的风险更大。这一研究计划的成功依赖于最先进的技术，包括地球化学建模和同位素表征。后者是环境取证中的一个强大工具，它允许对分子进行指纹识别，以便找到它们的来源。

In Canada, environmental impact assessments are critical to the approval of industrial projects. Traditionally the impacts of different projects in a region have been evaluated on an individual basis. However, as economic development and climate change put an increasing pressure on ecosystems and water resources, it becomes clear that we must take into account the cumulative character of environmental impacts, both in space and time. This is an emerging research field that will play a major role in Canada in the future (Council of Canadian Academies, 2019), and that promises better protection of the environment for generations to come. Tackling this issue now will position Canada as a worldwide leader in sustainable development. At this early stage, it is crucial to develop a sound scientific framework and improve our ability to consider cumulative impacts. Indeed, in a given industrial context, we must be able to answer the following questions: 1) what are the potential sources of contaminants in this area?; 2) do we understand the migration pathways for these contaminants, so that we know where to look?; 3) will we be able to distinguish different sources of a same contaminant in the environment?; and 4) can we predict the ecosystem's response to the accumulation of contaminants over time and space? For the first 5-year cycle of this research program, I aim to bring significant contribution to answering the first 3 questions above, for specific contaminants that migrate vertically from deep geological formations (> 500 m) towards shallow aquifers (<200 m). Indeed, freshwater aquifers are in the central position of a «sandwich» which comprises sources of contaminants both above (e.g. road de-icing salts, fertilizers) and below (e.g. mining, hydrocarbon production). While contaminants from above have received considerable attention, those coming from below have been largely overlooked, mainly because the deep migration pathways through which they travel are difficult to study. More precisely, HQP-led activities will allow characterizing the release of contaminants (mainly nitrate) from underground mine blasting operations. Such underground sources of nitrate have been very poorly documented so far. The research activities will also target the improvement of source identification methods for brines, which are commonly associated with deep geological formations. Finally, recently-produced databases will be used to initiate a screening of preferential migrations pathways naturally linking deep and shallow geological formations in Quebec, in order to assess which aquifers are at greater risk of contamination by deep industrial activities. The success of this research program relies upon state-of-the art techniques, including geochemical modelling and isotopic characterization. The latter is a powerful tool in environmental forensics, which allows fingerprinting molecules in order to find their source.