Particle-bound nutrients in (semi-)natural rivers: Do simplified assumptions lead to inappropriate recommendations for action?

Rivers have the possibility of self-purification through physico-chemical and biological processes. These are influenced by the combination of plants, microbiological activities and higher aquatic organisms such as macroinvertebrates and fish, and thus represent a balance between substance input and degradation or transformation. However, these ecosystems are in a delicate balance that can be disturbed by external influences. There are increasing ecological problems due to elevated nutrient concentrations in small rivers, especially during low water periods. The project focusses on (particle-bound) nutrients as well as nutrient retention and transport, taking into account the (semi-)natural substrate conditions in rivers. Laboratory experiments are used to investigate the influence of the bed substrate on particle-bound nutrient transport.