International Research Fellowship Program: Using Computational Chemistry to Assess Reactivity of Contaminants in Surface Waters

国际研究奖学金计划使美国科学家和工程师能够在国外进行9到24个月的研究。该计划的奖项提供了联合研究的机会，并利用国外独特或互补的设施、专业知识和实验条件。该奖项将支持Jennifer J.Guerard博士与瑞士联邦水产科学与技术研究所的Silvio Canonica博士和瑞士联邦理工学院的J.Samuel Arey博士合作为期24个月的研究奖学金。天然水中的有机污染物有可能通过各种反应途径被降解。对这些污染物的去向和影响的评估往往在很大程度上取决于对其清除或转化为其他化合物的主要降解过程的量化。越来越多的人认识到，光诱导过程在许多水生污染物的降解中发挥着重要而复杂的作用。这个项目将使用最先进的计算方法来预测化合物的单电子氧化电位和反应动力学，这些化合物在光激发下可以发生电子转移到三重激发态(磺胺类和苯脲类除草剂)和溶解有机物的类似物(富电子酚和取代苯胺)，这是一种普遍存在于所有天然地表水的不均匀物质。一种新的计算方法将计算水溶液中的电离自由能，以提供可靠的有机污染物水相单电子氧化自由能的计算，误差在1-2千卡/摩尔以内。Rehm-Weller模型将用于描述三重态激发的DOM的氧化动力学。这些模型的发展将使我们能够更好地评估3DOM*对水生系统中更广泛的目标污染物的环境退化的意义。

0852999GuerardThe International Research Fellowship Program enables U.S. scientists and engineers to conduct nine to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad.This award will support a twenty-four-month research fellowship by Dr. Jennifer J. Guerard to work with Dr. Silvio Canonica at the Swiss Federal Institute of Aquatic Science and Technology and with Dr. J. Samuel Arey at Ecole Polytech Federale in Switzerland.Organic contaminants in natural waters have the potential to be degraded by a variety of reaction pathways. Assessment of the fate and impact of these contaminants often hinges heavily on quantification of the principal degradation processes responsible for their removal or transformation into other compounds. It is increasingly understood that light-induced processes play a significant and complicated role in the degradation of many aquatic contaminants. This project will use state of the art computational methods to predict the single electron oxidation potentials and reaction kinetics of compounds that can undergo electron transfer upon photo excitation to the triplet excited state (sulfonamides and phenylurea herbicides) and analogues for dissolved organic matter (electron-rich phenols and substituted anilines), a heterogeneous substance ubiquitous in all natural surface waters. A novel computational approach will calculate free energy of ionization in water solutions to provide reliable computation of aqueous one-electron oxidation free energies of organic contaminants to within 1-2 kcal/mol error. The Rehm-Weller model will be applied to describe the kinetics of oxidation by triplet-excited DOM. These model developments will allow us to better assess the significance of 3DOM* for the environmental degradation of a wider range of target pollutants in aquatic systems.