Understanding the transformation of emerging organic contaminants in surface and groundwater

在世界各地的地表水和地下水中都检测到农药，对生态系统和公众健康构成重大威胁。为了保护自然世界和公众健康，必须尽可能多地保护我们的水资源。为了解决这个问题，揭示环境中这些污染物转化的过程至关重要。这将使我们能够制定加速这些化学品转化的战略。然而，环境中污染物的降解往往表现为一个黑盒子，因为许多过程，难以解开，可以发生。化合物特异性稳定同位素分析（CSIA）是一种很有前途的方法，可以提供特定过程的信息。在转化过程中，具有轻同位素（如12C）的分子通常以与具有重同位素（如13C）的分子不同的速率降解，导致未降解分子的分馏。这种方法是强大的，因为它可以检测特定的降解过程，甚至量化它们，这是极其困难的方法，仅依靠浓度测量。我研究的长期目标是揭示驱动水资源中污染物降解的转化途径。该计划的重点是阿特拉津、甲草胺（除草剂）及其转化产物，因为它们对生态系统和人类健康具有毒性。它们在加拿大也被广泛应用，经常在水资源中被检测到。生物降解有望成为环境中农药减少的主要途径之一。非生物过程可以大大促进地表水和地下水的退化，但研究较少。我的研究计划的短期目标是：i)识别和量化地表水中阿特拉津和异甲草胺的不同降解过程，重点是光降解。ii)确定地下水中异丙甲草胺非生物转化的相关性。工作将在不同的空间尺度上进行，从实验室实验到在qusamubec湖泊和安大略省的一个含水层进行实地研究。在实地应用前，将在控制条件下测定不同过程的同位素分异，如光降解、还原性硫种对异丙甲草胺的非生物降解和生物降解，以揭示不同转化过程对总体观察到的降解的相对贡献。我的研究将告诉我们水中无处不在的有毒农药的转化过程的程度，这些过程对整体退化的相对贡献，它们的空间和时间变异性，以及它们的限制因素。这些知识对于预测这些农药对水资源的长期影响至关重要，并将有助于确定有希望的补救策略，以保护饮用水并减少农药对环境的影响。

Pesticides are detected in surface and groundwater worldwide and pose a major threat to ecosystems and public health. In order to protect the natural world and public health, it is essential to preserve, as much as possible, our water resources. To address this, it is critical to unveil the processes responsible for the transformation of these contaminants in the environment. This will allow us to develop strategies to accelerate the transformation of these chemicals. However, the degradation of contaminants in the environment often appears as a black box since many processes, difficult to disentangle, can occur. A promising approach, giving process-specific information, is compound-specific stable isotope analysis (CSIA). During their transformation, molecules with light isotopes (e.g., 12C) are usually degraded at a different rate than those with heavy isotopes (e.g., 13C), leading to a fractionation in undegraded molecules. This approach is powerful because it can detect specific degradation processes and even quantify them, which is extremely difficult to do with approaches relying only on concentration measurements. The long-term objective of my research is to unveil the transformation pathways driving the degradation of contaminants in water resources. This program focuses on atrazine, metolachlor (herbicides) and their transformation products because of their toxicity to ecosystems and human health. They are also widely applied in Canada and often detected in water resources. Biodegradation is expected to be one of the main pathways for pesticide mitigation in the environment. Abiotic processes can substantially contribute to degradation in surface water and groundwater, but are less studied. The short-term objectives of my research program are: i)To identify and quantify different degradation processes of atrazine and metolachlor in surface water, focusing on photodegradation. ii)To determine the relevance of abiotic transformation of metolachlor in groundwater. Work will be done at different spatial scales, from the laboratory experiments to the field study in Québec lakes and in one aquifer in Ontario. The isotope fractionation of different processes such as photodegradation, abiotic degradation of metolachlor by reduced sulfur species and biodegradation will be determined in controlled conditions before application on the field to reveal the relative contributions of different transformation processes to the overall observed degradation. My research will inform us on the extent of transformation processes of ubiquitous and toxic pesticides in water, the relative contribution of each of these processes to the overall degradation, their spatial and temporal variability, and their limiting factors. This knowledge is critical to predict the long-term impact of these pesticides on water resources, and will help identify promising remediation strategies to protect drinking water and decrease the environmental impact of pesticides.