title: Characterisation of dissolved organic matter fluorescence properties by PARAFAC analysis and thermal quenching.
abstract: The fluorescence intensity of dissolved organic matter (DOM) in aqueous samples is known to be highly influenced by temperature. Although several studies have demonstrated the effect of thermal quenching on the fluorescence of DOM, no research has been undertaken to assess the effects of temperature by combining fluorescence excitation - emission matrices (EEM) and parallel factor analysis (PARAFAC) modelling. This study further extends previous research on thermal quenching by evaluating the impact of temperature on the fluorescence of DOM from a wide range of environmental samples, in the range 20 °C - 0 °C. Fluorescence intensity increased linearly with respect to temperature decrease at all temperatures down to 0 °C. Results showed that temperature affected the PARAFAC components associated with humic-like and tryptophan-like components of DOM differently, depending on the water type. The terrestrial humic-like components, C1 and C2 presented the highest thermal quenching in rural water samples and the lowest in urban water samples, while C3, the tryptophan-like component, and C4, a reprocessed humic-like component, showed opposite results. These results were attributed to the availability and abundance of the components or to the degree of exposure to the heat source. The variable thermal quenching of the humic-like components also indicated that although the PARAFAC model generated the same components across sites, the DOM composition of each component differed between them. This study has shown that thermal quenching can provide additional information on the characteristics and composition of DOM and highlighted the importance of correcting fluorescence data collected in situ.
authors.affiliation: School of Civil Engineering, University of Birmingham, B15 2TT, UK; National Institute of R&D for Optoelectronics, Atomistilor 409, 077125 Magurele, Romania. Electronic address: e.m.carstea@bham.ac.uk.
authors.forename: Elfrida M
authors.initials: EM
authors.lastname: Carstea
authors.affiliation: Connected Waters Initiative, University of New South Wales, Sydney, NSW 2052, Australia. Electronic address: a.baker@unsw.edu.au.
authors.forename: Andy
authors.initials: A
authors.lastname: Baker
authors.affiliation: Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ, UK. Electronic address: m.bieroza@lancaster.ac.uk.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Bieroza
authors.affiliation: Biological, Biomedical and Analytical Sciences, University of the West of England, Bristol BS16 1QY, UK. Electronic address: Darren.Reynolds@uwe.ac.uk.
authors.forename: Darren M
authors.initials: DM
authors.lastname: Reynolds
authors.affiliation: School of Civil Engineering, University of Birmingham, B15 2TT, UK. Electronic address: j.bridgeman@bham.ac.uk.
authors.forename: John
authors.initials: J
authors.lastname: Bridgeman
mesh_terms: D003080:Cold Temperature; D004739:England; D005163:Factor Analysis, Statistical; D005618:Fresh Water / Q000032:analysis*; D006812:Humic Substances / Q000032:analysis*; D013050:Spectrometry, Fluorescence / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D006812:Humic Substances; D014874:Water Pollutants, Chemical
keywords: Dissolved organic matter; Fluorescence spectroscopy; Parallel factor analysis; Temperature correction; Thermal quenching