Electric conductivity, pH, redox potential
and dissolved oxygen were either measured continuously and logged every 15 min with SC1000
sensors (Hach Lange sc-sensors 3798-S, phD-S,
1200-S, LDO) or measured daily with a handheld multi-electrode metre (WTW Multiline
350i). Dissolved ions were determined by photometry (Hach Lange LCK tests, Cadas30)