Superoxide Dynamics in Irradiated Seawater

这项研究将增进对海洋中光如何影响活性氧物种(ROS)循环的理解，这是一个研究不足的课题，其速率可能被低估，并对表层海洋生物地球化学产生影响。ROS通过影响痕量金属的可利用性、细胞压力和有机化合物的性质来影响初级生产力和海洋中的碳循环。在光氧化过程中，超氧化物歧化酶是控制过氧化氢生成和二氧化物(O2)去向的主要ROS。研究人员将使用一系列受控实验研究，来解决在亮海水和暗海水中超氧化物形成的衰减率和途径，以及波长如何影响超氧化物产生的问题。该项目将支持一名早期职业科学家，以及将接受实地和实验室研究、光学、数据分析、光化学建模、会议陈述和手稿准备方面培训的研究生和本科生。研究人员将与当地高中化学教师合作，帮助他们在课堂上使用项目数据来展示环境应用并教授基础动力学。活性氧(ROS)、超氧化物(O2-)和过氧化氢(H2O2)共同参与了有机污染物的降解、有机碳循环、铁、铜和锰的氧化还原循环，这些循环反过来影响海洋浮游植物的分布，并导致海洋生物主要类群的外部氧化应激。对微生物在O2-氧化还原化学中作用的新理解，光学定义的光化学曝光系统的进展，以及通过灵敏、实时的化学发光在环境水平上同时测量O2-和H2O2的能力，创造了重新审视有关海水中的光氧化还原反应的未解问题的机会。这项研究的目的是通过进行受控实验来捕捉在有和没有辐射的情况下的衰减速率和路径，并建立一个改进的、全光谱的超氧化物光化学模型，以改进对阳光充足的海水中原位ROS动力学的估计，从而促进对海水中ROS光化学的理解。研究人员将使用溶解在人工溶液和天然海水中的各种标准和收集的有机成分的矩阵，并：1)识别、量化和限制在辐照期间观察到的海水中O2-浓度的光化学反应和热反应速率和机制的范围；2)量化O2-和H2O2产生的光谱光化学效率；以及3)使用基于光学的光化学模型的结果，跨时间和空间尺度以及各种光学和化学约束来估计海水中O2-和H2O2的光化学产生率。这项裁决反映了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 study will improve understanding of how cycling of reactive oxygen species (ROS) is affected by light in the ocean, a research topic that has been understudied, with rates likely underestimated, and with implications for surface ocean biogeochemistry. ROS affect primary productivity and carbon cycling in the ocean by influencing availability of trace metals, cellular stress, and properties of organic compounds. Superoxide is the primary ROS controlling hydrogen peroxide formation and the fate of dioxide (O2) in photooxidation. The investigators will use a series of controlled experimental studies to address questions about decay rates and pathways of superoxide formation in light versus dark seawater and how wavelength affects superoxide production. This project will support an early career scientist, as well as graduate and undergraduate students who will receive training in field and lab research, optics, data analysis, photochemical modeling, presentations at meetings and manuscript preparation. The investigator will collaborate with local high school chemistry teachers to help them use project data in the classroom to show environmental applications and teach basic kinetics. Together, the reactive oxygen species (ROS) superoxide (O2-) and hydrogen peroxide (H2O2) are involved in the degradation of organic pollutants, organic carbon cycles, redox cycling of iron, copper, and manganese which in turn affect marine phytoplankton distributions and contribute to external oxidative stress in major taxa of marine organisms. New understanding of microbial roles in O2- redox chemistry, advances in optically defined photochemical exposure systems, and the ability to simultaneously measure both O2- and H2O2 at environmental levels with sensitive, real-time chemiluminescence create an opportunity to re-examine unanswered questions about photo-redox reactions in seawater. The objective of this study is to advance understanding of ROS photochemistry in seawater by conducting controlled experiments to capture decay rates and pathways with and without irradiation and to assemble an improved, fully spectral photochemical model for superoxide that improves estimates of in situ ROS dynamics in sunlit ocean waters. The investigators will use a matrix of various standard and collected organic constituents dissolved in constructed solutions and natural seawater and: 1) identify, quantify, and constrain the range of photochemical and thermal reaction rates and mechanisms responsible for observed O2- concentrations in seawater during irradiation; 2) quantify the spectral photochemical efficiency of O2- and H2O2 production; and 3) use results in optically-based photo-chemical models to estimate O2-and H2O2 photochemical production rates in seawater across temporal and spatial scales and various optical and chemical constraints.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.