Photochemical Reactions of Particulate Mercury Species at the Water-Particle Interface in Aquatic Environments

在这个项目中，dr。佛罗里达国际大学的蔡勇（Yong Cai）、刘光良（Guangliang Liu）和凯文·奥谢（Kevin O’shea）受到美国国家科学基金会化学部环境化学科学项目的资助，研究与水生环境中颗粒有关的汞（Hg）的反应。这些颗粒汞（pHg）在自然水域中非常常见，它们通常被认为是不活跃的，不太可移动。然而，它们确实在阳光的影响下发生反应（光化学反应），需要考虑对汞循环的准确描述，特别是汞的空气-水交换。本项目旨在提供对这些光化学反应的基本认识，并探索pHg在空气-水汞交换中的作用。该项目对西班牙裔服务机构的研究、教育和外展有广泛的好处。它为博士和本科生提供培训。代表性不足的少数族裔学生获得了研究经验。独特的以环境化学为重点的博士课程开发正在加强。该项目还提高了公众对汞污染和健康风险的认识。由于水生粒子具有半导体性质和光敏性，因此研究人员将重点放在pHg的电子空穴对和活性氧的光化学反应上。他们定义了pHg光转化的反应途径，量化了氧化汞的光化学还原动力学和单质pHg的氧化。他们还研究了与pHg光反应有关的机制。利用不同带隙能的铁、钛和氧化锰模型粒子和场收集粒子进行实验，并结合量子化学计算。带隙能量分析使用光谱测量。采用电感耦合等离子体质谱（ICP-MS）和扫描电子显微镜（SEM）测定颗粒的化学成分和光学性质。溶解相和颗粒相中元素汞和氧化汞的分析是基于同位素稀释、吹扫和捕集、热解吸和ICP-MS方法。该研究有望阐明pHg物种参与汞光化学转化及其在空气-水汞交换中的作用。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

In this project, Drs. Yong Cai, Guangliang Liu, and Kevin O'Shea at the Florida International University are funded by the Environmental Chemical Sciences Program of the NSF Division of Chemistry to study the reactions of mercury (Hg) that is associated with particles in aquatic environments. These particulate Hg species (pHg) are very common in natural waters, and they are often thought of as unreactive and not very mobile. However, they do react under the influence of sunlight (photochemical reactions) and need to be considered for an accurate description of Hg cycling, especially the air-water exchange of Hg. This project aims to provide a basic understanding of these photochemical reactions and explore the role of pHg in the air-water Hg exchange. The project has a broad range of benefits to research, education, and outreach at a Hispanic Serving Institution. It provides training for PhD and undergraduate students. Underrepresented minority students gain research experience. The curriculum development of the unique Environmental Chemistry-focused PhD track program is being enhanced. The project also promotes public awareness on Hg contamination and health risks. Since the aquatic particles are semiconducting and photosensitizing in nature, the investigators focus on the photochemical reactions of pHg involving electron-hole pairs and reactive oxygen species. They define the reaction pathways of pHg phototransformations and quantify the kinetics of photochemical reduction of oxidized Hg species and the oxidation of elemental pHg. They also study the mechanisms related to the pHg photoreactions. Experiments using model iron, titanium, and manganese oxide particles of different band gap energies and field-collected particles are combined with quantum chemistry calculations. The bandgap energies analysis uses spectrometric measurements. Particle chemical composition and optical properties are determined using inductively coupled plasma mass spectrometry (ICP-MS) and scanning electron microscopy (SEM). The analysis of elemental and oxidized Hg in the dissolved and particulate phases is based on an isotope dilution, purge and trap, thermal desorption, and ICP-MS method. The research is expected to clarify the involvement of pHg species in Hg photochemical transformation and the role in air-water Hg exchange.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.