Quantifying Hydroxylating Species in Dissolved Organic Matter Photochemistry

在化学系环境化学科学项目的资助下，来自科罗拉多大学博尔德分校的Fernando Rosario-Ortiz博士和Garrett McKay博士正在研究溶解有机物(DOM)的光化学。DOM是存在于所有水环境中的有机分子的混合物。DOM影响许多环境过程，包括降解水中的有机污染物。DOM的一部分吸收阳光，这一部分通常被称为发色DOM(CDOM)。一旦CDOM吸收光，它可以形成一系列活性物种，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种。这些物种共同影响有机污染物在环境中的降解方式。这项研究的结果有助于环境化学家更好地了解有机污染物在地表水中的去向和迁移。来自研究的数据被纳入课程，并在研讨会上传播。从CDOM光化学产生OH和其他羟化物种的机理尚不清楚。总体而言，从CDOM生产OH的测量量子产率很小。OH的低稳态浓度和瞬变性质要求使用探针化合物来测量它。在过去的十年里，人们达成了一种共识，即CDOM光解生成的OH既可以被分配为游离的OH，也可以被分配为类OH，它们的能量更低，活性也更低。后者与羟基探针反应，生成与游离羟基反应相同的产物。在某些情况下，类OH物种对整个OH反应活性的贡献率高达50%，因此CDOM光解产生的类OH氧化剂在环境光化学过程中发挥着重要作用，最终在有机污染物的降解中发挥着重要作用。本项目致力于表征CDOM光羟化反应中产生的类OH物种的形成和反应活性。为了实现这一点，我们对两个方面进行了评估。首先，Rosario-Ortiz博士和McKay博士描述了CDOM光化学中产生的低能氧化剂的反应性和特性。第二，正在研究CDOM组成与CDOM光羟化反应中低能氧化剂形成的反应性之间的关系。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。

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.