Water Resources Research Act Program

Details for Project ID 2011KY174B

By-proxy monitoring of aqueous nitrate photolysis and the effect of hydroxl radical

Institute: Kentucky
Year Established: 2011 Start Date: 2011-03-01 End Date: 2012-12-31
Total Federal Funds: $5,000 Total Non-Federal Funds: $10,001

Principal Investigators: Matthew Nee

Abstract: By using infrared (IR) vibrational spectroscopy, we will study photochemical reactions in aqueous solutions in the laboratory to refine the models used to predict the levels of NOx and ozone. While these experiments will be performed in the laboratory, they are critical to predicting the production of NOx and ozone from aquatic sources: the ultimate goal is to connect concentrations of nitrate ion and hydroxyl radical (OH∙) in field studies to levels of NOx and ozone detected in the air above them. For predictive correlations to be made, the kinetic model for the photochemical reactions following the photolysis of aqueous nitrate ion must be well-understood. Our group is developing methods to make use of the change in nitrate vibrational structure as a proxy for the chemical composition of the sample surrounding it. Vibrational spectroscopy combines speed of acquisition with molecular specificity, making it ideal for kinetics studies. Preliminary studies in our lab indicate that, after nitrate ion is photolyzed, the relative amounts of two different nitrate structures change over time. We hypothesize that this is a result of the influence of other compounds in the solution influencing the nitrate ion structure. We will investigate the effect of hydrogen peroxide as a proxy for highly reactive hydroxyl radicals, in order to explore how the molecular structure of nitrate ion changes during the course of a photochemical reaction. Our experiments will have two objectives: (1) the collection of temperature dependent data regarding the change in the asymmetric N-O stretching region following UV irradiation and (2) the collection of similar spectra with hydrogen peroxide added to assess the influence of hydroxyl radicals on the reaction.