Hydrogeochemistry of iron, manganese, sulfur and organic matter in the Fraser River Delta aquifer system

本研究的目的是建立一个框架，以了解和预测减少地下水在三角洲含水层-弱透水层系统的地球化学演化。在不列颠哥伦比亚省的弗雷泽河三角洲含水层系统中，所有者和监管机构正在努力管理受污染和未受干扰地点的高铁锰浓度地下水。 人们认识到，厌氧条件下的有机物降解是导致高铁、锰和砷等微量元素的过程的关键驱动因素。然而，我们对有机物厌氧降解的地球化学途径的理解存在差距，如何在模型中代表这些途径，以及如何描述有机物的原位或非原位特征，以便模型可以参数化。在许多情况下，有机物的来源，无论是深层沉积有机物还是来自池塘或土壤的表面，都是未知的。 厌氧有机物降解过程与铁、锰和硫的还原相结合，不能孤立地进行研究。本文提出了一个野外-实验室-模拟一体化的研究方案. 研究现场位于不列颠哥伦比亚省温哥华的弗雷泽河三角洲系统。该方法取决于四个组成部分：1）自然系统的现场表征;评估和开发表征策略; 2）样品的矿物学和地球化学分析; 3）受控条件下的实验室实验;以及4）在现场规模评估假设的机制建模，以整合和解释数据。 在这里开发的框架将是有用的，在应用程序中的工程问题，如修复和环境评估，并改善未受干扰和污染的网站的管理。该研究将适用于其他环境，如阿尔伯塔的油砂，页岩气开发和南亚的大三角洲。

The goal of this research is to develop a framework to understand and predict the geochemical evolution of reducing groundwater in deltaic aquifer-aquitard systems. In the Fraser River Delta aquifer system in British Columbia, owners and regulators are struggling to manage groundwater with high iron and manganese concentrations at both contaminated and undisturbed sites. It is recognized that organic matter degradation under anaerobic conditions is the key driver of the processes leading to high iron, manganese and trace elements such as arsenic. However, there is a gap in our understanding of the geochemical pathways of anaerobic degradation of organic matter, how to represent those pathways in models and how to characterize organic matter in - or ex situ so that models can be parameterized. The source of the organic matter, whether detrial sedimentary organic matter or surface derived from ponds or soils is not known in many cases. The processes of anaerobic organic matter degradation are coupled to the reduction of phases of iron, manganese and sulfur and cannot be examined in isolation. An integrated field - laboratory - modeling research program is proposed here. The research field site is in the Fraser River Delta system in Vancouver BC. The methodology hinges upon four components: 1) field characterization of natural systems; assessment and development of characterization strategies; 2) mineralogical and biogeochemical analysis of samples; 3) laboratory experiments under controlled conditions; and 4) mechanistic modeling to evaluate hypotheses at the field scale, to integrate and to interpret data. The framework developed here will be useful in application to engineering problems such as remediation and environmental assessment and improve management of undisturbed and contaminated sites. The research will be applicable to other settings such as the oil sands of Alberta, shale gas developments, and the great deltas of South Asia.