Collaborative Research: Application of fluorescence spectroscopy for the characterization of dissolved organic matter: Disentangling common misconceptions and underlying chemistry

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Dissolved organic matter (DOM) is a complex mixture of carbon containing molecules that are present in all aquatic environments. DOM plays an important role in aquatic ecosystems. Thus, variations in DOM chemical composition may inform understanding of different processes in the environment. Fluorescence has emerged as a common tool to characterize DOM, but many challenges are associated with its use. In this research collaboration between the University of Colorado at Boulder and Montana State University, the connection between fluorescence characterization of DOM and specific chemical constituents within this mixture will be evaluated. The results from this study will impact the field of environmental engineering and aquatic science by providing specific guidelines and education regarding the use of fluorescence as a broad metric for DOM chemical understanding in aquatic ecosystems. The characterization of dissolved organic matter (DOM) by fluorescence spectroscopy has become ubiquitous in the environmental engineering and science communities. Specifically, the use of excitation emission matrices (EEMs) has emerged as one of the most common tools used by researchers examining DOM on numerous natural and engineered processes. Given the amount of data collected in an EEM, several qualitative and quantitative approaches have been developed to analyze the results. In most cases, these approaches attempt to tie a fluorescence response to a chemical constituent or behavior within DOM. The environmental engineering and science community has embraced fluorescence as an important tool for the characterization of DOM. However, little progress has been made in understanding what specific factors (e.g., chemical structures and molecular composition) controls the observed fluorescence response. The main goal of this project is to fill the deficiencies in chemical interpretations of fluorescence information by conducting a detailed evaluation of fluorescence analyses as a broad measure to interpret the chemical composition and variability of DOM. The results from this proposal will offer guidelines to engineers and scientists regarding the use of fluorescence for the characterization of DOM. The use of different commonly used fluorescent interpretation metrics will be calibrated against distinct chemical analyses of DOM samples from highly fluorescing environmental fractions. It is expected that this project will provide the community with detailed guidelines regarding the limitations of the use of fluorescence for DOM research in natural and engineered systems. The educational component will focus on the incorporation of results from this study into collegiate curricula and departmental seminars at the collaborating institutions. Graduate and undergraduate students will be educated in analytical chemistry techniques routinely used for water quality assessments. They will also learn advanced analytical DOM characterization techniques at the molecular level. The fluorescent community will be informed of the results from this work via convened sessions organized at domestic and international scientific conferences and publications in high impact scientific journals.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.