In search of the pristine environments in the lowland river system of Flanders for assessing the impact of past human occupation on current phosphate concentrations

The Flemish region cannot cope with the guidelines set out in the European Water Framework Directive for good water quality, mainly due to excess nutrients. Over 80% of the data from rivers and lakes exceed the phosphate (P) limit. The P concentrations in surface water fail to decrease despite reduced P emissions during the last 20 years. We have recently shown that P concentrations in Flemish waters are mainly affected by internal loading of the sediment, a process that is accelerated by the specific geophysical conditions of a lowland river system that makes it susceptible to redox cycling. The objective of this project is to estimate the natural fraction of that process, i.e. the pre-anthropogenic concentration range of P in surface water of Flanders. In addition, this project wants to quantify the role of human development on the current P concentration range. An archeological and geophysical approach will be used to infer historic time trends (10,000 y BP-current) in sediment and surface water P in relation to the past population density and agricultural development. The historical reconstruction will be complemented with emission modelling and experiments on internal loading. The expected scientific outcomes is new information on past population history and the role of human development on regional enrichment of sediments and waters with P. The expected practical outcome is the provision of tools for the government to make regional specific nutrient limits.