Toward Understanding of Long-Term Nitrogen Transport and Retention Dynamics Across German Catchments

Long-term nitrogen (N) transport and retention dynamics across catchments are not well understood. Using a process-based model for 89 German catchments, results across study catchments reveal that most N surplus (during 1950-2014) was removed by denitrification (mean +/- standard deviation: 58 +/- 15%) while the remaining fraction was mostly stored in the soil (14% +/- 11%). The mean groundwater transit times in these catchments varied from 3.2 to 20.3 years. These results indicate that past N inputs could continue to affect surface and groundwater quality in the coming years. We identified four catchment groups with distinct archetypal N transport and retention dynamics, which are linked to the catchments' climate, topographic, and geological conditions. Overall, our results shed light on long-term N dynamics in German catchments and how they are linked to catchment characteristics, emphasizing the role of long-term N accumulation and transport for water quality management and evaluation programs.

Automated summary

Long-term nitrogen transport and retention dynamics in 89 German catchments were studied. Results showed that most nitrogen surplus was removed by denitrification, while the remaining portion was stored in the soil. The study also identified four catchment groups with distinct nitrogen transport and retention dynamics, highlighting the importance of long-term nitrogen accumulation and transport for water quality management.