Spatial characterization of the composition of the isotope hydrobiogeochemistry along the Warnow River

A spatial study of the isotopic hydrobiogeochemical composition along the the Warnow River, which drains into the southern Baltic Sea, was carried out. The sampling took place on 29-30 April 2019 from the source up to the estuary. In addition to in situ physico-chemical parameters, surface water was sampled using a telescopic rod and a plastic beaker and preserved for further analysis. Major and trace elements and selected nutrients were measured using an ICP-OES (iCAP, 7400, Duo Thermo Fischer Scientific). Ammonium (NH4) and nitrate (NO3) concentrations were measured using a QuAAtro autoanalyzer system. Chloride (Cl) concentrations were measured by electrical potential difference precipitation with 0.05 M AgNO3. Dissolved inorganic carbon (DIC), and δ13CDIC were measured using an isotope gas mass spectrometer (MAT 253) coupled to a Gasbench II. Dissolved organic carbon (DOC) and δ13CDOC using an Elementar iso TOC cube with Thermo Electron MAT 253 mass spectrometry, δ18OH2O, and δ2HH2O using a CRDS system (laser cavity-ring-down-spectroscopy, Picarro L2140- I). δ34S and δ18O of SO4 using a gas-isotope mass spectrometer MAT253 (Thermo-Finnigan) with EA-Isolink (Thermo-Fisher-Scientific).