title: What's in an EEM? Molecular signatures associated with dissolved organic fluorescence in boreal Canada.
abstract: Dissolved organic matter (DOM) is a master variable in aquatic systems. Modern fluorescence techniques couple measurements of excitation emission matrix (EEM) spectra and parallel factor analysis (PARAFAC) to determine fluorescent DOM (FDOM) components and DOM quality. However, the molecular signatures associated with PARAFAC components are poorly defined. In the current study we characterized river water samples from boreal Québec, Canada, using EEM/PARAFAC analysis and ultrahigh resolution mass spectrometry (FTICR-MS). Spearman's correlation of FTICR-MS peak and PARAFAC component relative intensities determined the molecular families associated with 6 PARAFAC components. Molecular families associated with PARAFAC components numbered from 39 to 572 FTICR-MS derived elemental formulas. Detailed molecular properties for each of the classical humic- and protein-like FDOM components are presented. FTICR-MS formulas assigned to PARAFAC components represented 39% of the total number of formulas identified and 59% of total FTICR-MS peak intensities, and included significant numbers compounds that are highly unlikely to fluoresce. Thus, fluorescence measurements offer insight into the biogeochemical cycling of a large proportion of the DOM pool, including a broad suite of unseen molecules that apparently follow the same gradients as FDOM in the environment.
authors.affiliation: Skidaway Institute of Oceanography, Marine Sciences Department, University of Georgia , Savannah, Georgia 31401, United States.
authors.forename: A
authors.initials: A
authors.lastname: Stubbins
authors.forename: J-F
authors.initials: JF
authors.lastname: Lapierre
authors.forename: M
authors.initials: M
authors.lastname: Berggren
authors.forename: Y T
authors.initials: YT
authors.lastname: Prairie
authors.forename: T
authors.initials: T
authors.lastname: Dittmar
authors.forename: P A
authors.initials: PA
authors.lastname: del Giorgio
mesh_terms: D004784:Environmental Monitoring / Q000295:instrumentation / Q000379:methods*; D005163:Factor Analysis, Statistical; D005453:Fluorescence; D005583:Fourier Analysis; D006812:Humic Substances / Q000032:analysis*; D013058:Mass Spectrometry / Q000379:methods; D011792:Quebec; D045483:Rivers / Q000737:chemistry*; D052616:Solid Phase Extraction; D013050:Spectrometry, Fluorescence / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D006812:Humic Substances; D014874:Water Pollutants, Chemical