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.