title: Quantifying in-stream retention of nitrate at catchment scales using a practical mass balance approach.
abstract: As field data on in-stream nitrate retention is scarce at catchment scales, this study aimed at quantifying net retention of nitrate within the entire river network of a fourth-order stream. For this purpose, a practical mass balance approach combined with a Lagrangian sampling scheme was applied and seasonally repeated to estimate daily in-stream net retention of nitrate for a 17.4 km long, agriculturally influenced, segment of the Steinlach River in southwestern Germany. This river segment represents approximately 70% of the length of the main stem and about 32% of the streambed area of the entire river network. Sampling days in spring and summer were biogeochemically more active than in autumn and winter. Results obtained for the main stem of Steinlach River were subsequently extrapolated to the stream network in the catchment. It was demonstrated that, for baseflow conditions in spring and summer, in-stream nitrate retention could sum up to a relevant term of the catchment's nitrogen balance if the entire stream network was considered.
authors.affiliation: Water & Earth System Science (WESS) Competence Cluster, University of Tübingen, Hölderlinstr. 12, 72074, Tübingen, Germany.
authors.forename: Marc
authors.initials: M
authors.lastname: Schwientek
authors.affiliation: Institute of Earth and Environmental Science, University of Potsdam, Karl-Liebknecht-Strasse 24-25, 14476, Potsdam-Golm, Germany. bselle@beuth-hochschule.de.|Department III - Civil Engineering and Geoinformation, Beuth University of Applied Sciences, Luxemburger Str. 10, 13353, Berlin, Germany. bselle@beuth-hochschule.de.
authors.forename: Benny
authors.initials: B
authors.lastname: Selle
mesh_terms: D000383:Agriculture; D004784:Environmental Monitoring / Q000379:methods; D005858:Germany; D009566:Nitrates / Q000032:analysis; D009589:Nitrogen Oxides; D045483:Rivers; D012621:Seasons
chemical_list: D009566:Nitrates; D009589:Nitrogen Oxides
keywords: Catchment scale; In-stream processes; Mass balance approach; Nitrate retention; Stream network