title: New Seasonal Shift in In-Stream Diurnal Nitrate Cycles Identified by Mining High-Frequency Data.
abstract: The recent development of in-situ monitoring devices, such as UV-spectrometers, makes the study of short-term stream chemistry variation relevant, especially the study of diurnal cycles, which are not yet fully understood. Our study is based on high-frequency data from an agricultural catchment (Studienlandschaft Schwingbachtal, Germany). We propose a novel approach, i.e. the combination of cluster analysis and Linear Discriminant Analysis, to mine from these data nitrate behavior patterns. As a result, we observe a seasonality of nitrate diurnal cycles, that differs from the most common cycle seasonality described in the literature, i.e. pre-dawn peaks in spring. Our cycles appear in summer and the maximum and minimum shift to a later time in late summer/autumn. This is observed both for water- and energy-limited years, thus potentially stressing the role of evapotranspiration. This concluding hypothesis on the role of evapotranspiration on nitrate stream concentration, which was obtained through data mining, broadens the perspective on the diurnal cycling of stream nitrate concentrations.
authors.affiliation: Institute for Landscape Ecology and Resources Management (ILR), Research Centre for BioSystems, Land Use and Nutrition (IFZ), Justus Liebig University Giessen, Heinrich-Buff-Ring 26, Giessen, Germany.
authors.forename: Alice H
authors.initials: AH
authors.lastname: Aubert
authors.affiliation: Institute for Landscape Ecology and Resources Management (ILR), Research Centre for BioSystems, Land Use and Nutrition (IFZ), Justus Liebig University Giessen, Heinrich-Buff-Ring 26, Giessen, Germany.
authors.forename: Lutz
authors.initials: L
authors.lastname: Breuer
mesh_terms: D000383:Agriculture; D057225:Data Mining; D004784:Environmental Monitoring; D005858:Germany; D009566:Nitrates / Q000032:analysis*; D010507:Periodicity; D045483:Rivers / Q000737:chemistry*; D012621:Seasons; D014867:Water / Q000032:analysis*
chemical_list: D009566:Nitrates; D014867:Water