3.2 Water chemical parameters
Water chemical parameters were measured in situ at shore transect and time series sampling spots A and I, using a Multi 3630 IDS multiparameter device (WTW, Weilheim, Germany), equipped with a WTW TetraCon 925 electrical conductivity measuring cell. At the A. P. Møller Skolen salinity and temperature was measured using a modular multi-parameter probe (WTW multimeter 3440), mounted with TetraCon® 925-P and MPP 930 IDS electrical conductivity cells. Before each application the cells were calibrated with E-Set Trace 0.01 M KCl calibration solution based on PTB/NIST. For samples from DZBC-timeseries (spots B-H), a WTW 1970i conductivity meter and TetraCon 325 measuring cell were used to analyse electrical conductivity / salinity in the laboratory.
Salinity maps (Fig. 2) were produced in QGIS 3.14 using the inverse distance weighted interpolation tool with a squared weighting coefficient for the sampling periods March and July 2020. Herefore, the in-situ measured salinity values were used for spatial interpolation, in combination with data derived from monthly monitoring stations of local authorities (LUNG; Landesamt für Umwelt, Naturschutz, Geologie of the German State Mecklenburg-Vorpommern) (Fig. 2). For March 2020, some additional values were derived from HOBO U24-002-C salinity loggers (Onset, Bourne, USA), which were installed at different locations around the Rügener boddens. Data were only interpolated within the riverine-marine mixing zone, while the open Baltic Sea was excluded.