title: Photochemical production of organic matter triplet states in water samples from mountain lakes, located below or above the tree line.
abstract: The production of triplet states (T(*)) of chromophoric dissolved organic matter (CDOM), reacting with the probe molecule 2,4,6-trimethylphenol (TMP) was measured upon irradiation of water samples, taken from lakes located in a mountain area (NW Italy) between 1450 and 2750 m above sea level. The lakes are located below or above the tree line and surrounded by different vegetation types (trees, alpine meadows or exposed rocks). The most photoactive samples belonged to lakes below the tree line and their fluorescence spectra and CDOM optical features suggested the presence of a relatively elevated amount of humic (allochthonous) material. The lowest (negligible) photoactivity was found for a lake surrounded by exposed rocks. Its CDOM showed an important autochthonous contribution (due to in-lake productivity) and considerably higher spectral slope compared to the other samples, suggesting low CDOM molecular weight and/or aromaticity. Among the samples, CDOM photoactivity (measured as the rate of TMP-reactive T(*) photoproduction) decreased with changing vegetation type in the order: trees, meadows, rocks. It could be connected with decreasing contribution from catchment runoff and increasing contribution from autochthonous processes and possibly precipitation.
authors.affiliation: Università degli Studi di Torino, Dipartimento di Chimica, Via P. Giuria 5, 10125 Torino, Italy.
authors.forename: Elisa
authors.initials: E
authors.lastname: De Laurentiis
authors.forename: Marco
authors.initials: M
authors.lastname: Minella
authors.forename: Valter
authors.initials: V
authors.lastname: Maurino
authors.forename: Claudio
authors.initials: C
authors.lastname: Minero
authors.forename: Marcello
authors.initials: M
authors.lastname: Brigante
authors.forename: Gilles
authors.initials: G
authors.lastname: Mailhot
authors.forename: Davide
authors.initials: D
authors.lastname: Vione
mesh_terms: D003116:Color; D003408:Cresols / Q000737:chemistry*; D060106:Lakes / Q000737:chemistry*; D055668:Photochemical Processes; D025341:Principal Component Analysis; D013050:Spectrometry, Fluorescence; D014197:Trees; D014867:Water / Q000737:chemistry*
chemical_list: D003408:Cresols; D014867:Water; C505148:2,4,6-trimethylphenol