Identification and management of nitrogen retention in a shallow groundwater-stream system of a small lowland catchment (Northern Germany)

摘要

Distributed modelling of soil- and groundwater processes has to be considered as a tool to increase knowledge of flow path, distribution of source and sink areas as well as of reactive sinks. This information can be used to target measures in areas with low denitrification capacities or high N-loads, or to de- cide on the priority of measures for ground- and surface water protection. Removal of nitrate is not independent of other geochemical processes, however. Also, the release of substances during denitrification reactions is of great concern for water quality. In-stream nitrate degradation can be identified as an important process in warm and dry periods in summer in the investigated lowland stream. The proposed new benthic flow chamber method offers opportunities to investigate single processes under changing boundary conditions like flow velocities, temperature, light or substance concentrations. The overall share of in-stream denitrification of total nitrogen degradation on the catchment scale still remains unclear. For the interactions between terrestrial and in-stream nitrogen turnover a coupling of a reactive transport groundwater model and a surface water quality model is required, implementing hyporheic zone processes.