The Role of Photo-Generated Hydrated Electrons in Determining the Environmental Fate of Short-Chain Chlorinated Paraffins in Surface Waters

这一奖项来自化学部环境化学科学项目，以支持毕格罗海洋科学实验室的Christoph Aeppli博士。该项目的目标是研究阳光如何决定湖泊和海洋表层水中短链氯化石蜡(SCCP)的命运。这些化合物已被归类为持久性有机污染物，但没有足够的科学数据来评估它们在水相中的去向。具体地说，关于短链氯化石蜡的间接光解过程还存在知识空白。在这个项目中，这个过程是在实验室中环境相关的条件下进行研究的。短链氯化石蜡的降解是由间接光解的两个主要物种介导的：所谓的水合电子和羟基自由基。这些反应的机制和速度正在确定中。有迹象表明，水合电子介导的途径对降解疏水污染物非常有效，特别是在地表水中。在这样的体系中，溶解有机物的存在有望促进转化反应。这项研究的预期结果是更好地了解湖泊和海洋中一类重要污染物的损失和持久性。科尔比学院的本科生在暑假和学年都参与了这项研究。他们在实验室环境化学方面获得了丰富的实践研究经验。博士后研究人员学习光化学、高端分析技术和计算化学的交叉。本项目研究水合电子是否是地表水中短链氯化石蜡光解的活性物种。据推测，这种带有水合电子的光化学降解发生在溶解有机物(DOM)聚集体中。使用含DOM的体系和清洁体系进行辐照实验，这些体系允许分别研究水合电子和羟基自由基对SCCP的光解作用。用全二维气相色谱对高度复杂的短链氯化石蜡同系物的降解进行了定量。为了解释包含DOM的光解实验的结果，正在使用基于量子化学的计算化学工具来估计单个SCCP同系物对DOM相的亲和力。总体而言，该项目促进了对地表水中疏水性污染物的光化学去向的理解。该项目还改善了迄今为止研究不足的一种光反应物种--水合电子的基础知识。此外，该项目培训下一代研究人员，并包括一个重要的本科教育部分。此外，还有一个积极的外展计划，教育更广泛的社区了解研究的相关性。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This award from the Environmental Chemical Sciences Program in the Division of Chemistry supports Dr. Christoph Aeppli at Bigelow Laboratory for Ocean Sciences. The goal of this project is to study how sunlight determines the fate of short-chain chlorinated paraffins (SCCPs) in surface water of lakes and oceans. These compounds have been classified as persistent organic pollutants, but there are insufficient scientific data to assess their fate in the aqueous phase. Specifically, there are knowledge gaps about a process called indirect photolysis of SCCPs. In this project, this process is studied in the laboratory under environmentally relevant conditions. The degradation of SCCPs is mediated by two primary species responsible for indirect photolysis: the so-called hydrated electron and the hydroxyl radical. The mechanisms and rates of these reactions are being determined. There are indications that the pathway mediated by hydrated electrons is highly effective for degrading hydrophobic pollutants, especially in surface water. In such systems, the presence of dissolved organic matter is expected to facilitate the transformation reaction. The anticipated outcome of this research is a better understanding of the loss and persistence of an important class of pollutants in lakes and oceans. Undergraduate students from Colby college participate in this research both in the summer and during the academic year. They gain intense hands-on research experience in laboratory environmental chemistry. A postdoctoral researcher learns about the intersection of photochemistry, high-end analytical techniques, and computational chemistry. This project investigates whether hydrated electrons are the active species for the photolysis of SCCPs in surface water. It is hypothesized that this photochemical degradation with hydrated electrons occurs in dissolved organic matter (DOM) aggregates. Irradiation experiments are conducted using DOM-containing systems as well as clean systems that allow a separate investigation of the SCCP photolysis by hydrated electrons as well as by hydroxyl radicals. Comprehensive two-dimensional gas chromatography is used to quantify degradation of the highly complex mixture of SCCP congeners. To interpret results from the DOM-containing photolysis experiments, the affinity of individual SCCP congeners into the DOM phase is being estimated using quantum chemical-based computational chemistry tools. Overall, this project advances the understanding of the photochemical fate of hydrophobic pollutants in surface waters. The project also improves the fundamental knowledge of a so-far understudied photoreactive species, the hydrated electron. Furthermore, this project trains the next generation of researchers and includes a significant undergraduate education component. Additionally, there is an active outreach program to educate the broader community on the relevance of the research.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.