The physo-chemical state of the Scheldt estuary is closely monitored in Flanders and the Netherlands. The physical chemistry is closely related to external influences like climate change, pollution and the ecological functioning of the Scheldt estuary. The monitoring of the phyyso-chemical system includes the sampling of surface water, the water column and soil. Standard physical parameters such as temperature and salinity are measured, as well as water and soil quality, light quality and substances pointing to pollution. Physo-chemical parameters are being measured in many research projects.