Moving towards a technical specification for fluorescence excitation-emission mapping and absorbance analysis of colored dissolved organic matter

Abstract

Colored Dissolved Organic Matter (CDOM) measurements with fluorescence and absorbance are important for a variety of natural water sources. Uncertainties have been propagated regarding CDOM spectral data from different instruments, sampling conditions and analysis algorithms. Recent efforts have thus focused on standardizing sample preparation, spectroscopic evaluation, and mathematical analysis to minimize interlaboratory variation The practical significance of simultaneous acquisition of the corrected absorbance spectrum and fluorescence excitation-emission map is discussed as a means to provide the least ambiguity. Variation can be caused by different light-exposure history (especially UV) in separate instruments, dissolved-oxygen content from temperature changes, and oxidation kinetics. Concentration changes in CDOM can be associated with optical anomalies, including self-quenching and -absorption, which systematically alter the fluorescence spectrum. Monitoring the absorbance and fluorescence simultaneously avoids these sampling variations and facilitates spectral correction. The proposed method(s) described are discussed regarding their potential as the basis for an international technical specification of the instrument and sampling conditions for CDOM analysis and reporting. © 2012 WIT Press.