Total luminescence spectral characteristics of natural organic matter (NOM) size fractions as defined by ultrafiltration and high performance size exclusion chromatography (HPSEC)

Natural organic matter (NOM) was isolated by reverse osmosis from two surface waters of differing climatic regimes and organic source material, in Norway and Georgia, USA. The NOM was separated into methodologically defined size fractions by ultrafiltration and high performance size exclusion chromatographic (HPSEC) techniques and the fractions were analyzed with UV-visible and total luminescence spectral techniques. While some systematic variation was observed, NOM from both systems had similar UV specific absorbance values and both had higher 254 nm specific absorbances in the larger molecular size fractions. Similarly, NOM from both systems had fluorescence spectral peaks in the regions of approximately λex/λem=225/425 nm and λex/λem=335/445 nm, consistent with spectra of humic substances in freshwater environments. Agreement of these measurements in two significantly different environments and with previously published literature indicates that freshwater NOM is very consistent relative to its absorbance and fluorescence chromophores, despite differences in the origin of the material and the early diagenetic processes to which plant material may be exposed.