Quantifying Hydroxylating Species in Dissolved Organic Matter Photochemistry

在化学学部环境化学科学项目的资助下，dr。来自科罗拉多大学博尔德分校的Fernando Rosario-Ortiz和Garrett McKay正在研究溶解有机物（DOM）的光化学。DOM是存在于所有水生环境中的有机分子的混合物。DOM影响许多环境过程，包括水中有机污染物的降解。一部分DOM吸收阳光，这一部分通常被称为发色DOM （CDOM）。一旦CDOM吸收光，它可以形成一个反应性物质的集合，包括羟基自由基（OH）和其他通过羟基化反应以类似方式反应的物质。这些物种共同影响着环境中有机污染物的降解。这项研究的结果有助于环境化学家更好地了解地表水中有机污染物的命运和运输。研究所得的数据被纳入一门课程，并在研讨会上传播。羟基和其他羟基化物质由CDOM光化学产生的机制尚不清楚。总的来说，从CDOM生产OH的量子产率非常小。氢氧根的低稳态浓度和瞬态性质要求使用探针化合物进行测量。在过去的十年中，人们逐渐达成共识，CDOM光解生成的OH可以分为游离OH和类OH两种，它们比游离OH能量更低，反应性更弱。后者与OH探针反应产生的产物与与游离OH反应相同。在某些情况下，类OH物质对总OH反应活性的贡献高达50%，因此，由CDOM光解产生的类OH氧化剂在环境光化学过程中发挥重要作用，并最终在有机污染物的降解中发挥重要作用。本项目的重点是表征在CDOM光羟基化反应中产生的oh -样物质的形成和反应性。要做到这一点，需要对两个方面进行评估。首先,Drs。Rosario-Ortiz和McKay描述了在CDOM光化学中产生的低能氧化剂的反应性和特性。其次，研究了CDOM光羟基化反应中CDOM组成和反应活性与低能氧化剂形成的关系。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。

With funding from the Environmental Chemical Sciences program of the Division of Chemistry, Drs. Fernando Rosario-Ortiz and Garrett McKay, from the University of Colorado at Boulder, are studying the photochemistry of dissolved organic matter (DOM). DOM is a mixture of organic molecules present in all aquatic environments. DOM impacts many environmental processes, including the degradation of organic contaminants in water. A fraction of the DOM absorbs sunlight, and this fraction is commonly referred to as chromophoric DOM (CDOM). Once CDOM absorbs light, it can form a collection of reactive species, including the hydroxyl radical (OH) and other species that react in a similar manner through hydroxylation reactions. These species collectively impact how organic contaminants are degraded in the environment. The results from this study help environmental chemists better understand the fate and transport of organic contaminants in surface waters. Data from the research are incorporated into a course and disseminated in seminars. The mechanism by which OH and other hydroxylating species are photochemically produced from CDOM remain unclear. Overall, the measured quantum yields for the production of OH from CDOM are very small. The low steady-state concentration and transient nature of OH require the use of probe compounds for its measurement. Over the past decade, a consensus has grown that OH formation from CDOM photolysis can be apportioned into both free OH as well as OH-like species, which are lower in energy and less reactive than free OH. The latter of these species reacts with OH probes to produce products identical to reaction with free OH. The contribution of OH-like species to overall OH reactivity is up to 50% in some instances, and thus OH-like oxidants produced from CDOM photolysis play an important role in environmental photochemical processes, and ultimately in the degradation of organic contaminants. This project focuses on characterizing the formation and reactivity of OH-like species produced in CDOM photohydroxylation reactions. To accomplish this, two aspects are evaluated. First, Drs. Rosario-Ortiz and McKay characterize the reactivity and identity of low-energy oxidants produced in CDOM photochemistry. Second, the relationship between CDOM composition and reactivity towards formation of low-energy oxidants in CDOM photohydroxylation reactions is being investigated.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.