Contribution of atmospheric N deposition to riverine N load in a forest-dominated watershed through field monitoring for three years

Increased atmospheric nitrogen (N) deposition significantly impacts N cycling in freshwater ecosystems. Relative to lakes, the importance of N deposition in riverine N load is less studied. Thus, this study monitored N deposition and riverine N load for three years and then used the export coefficient model to explore N deposition's contribution to riverine N load in a forest-dominated watershed. It is found that the annual export of total N (TN) deposition could explain 17.4%-19.2% of riverine TN load. The contribution of TN deposition to riverine TN load was significantly higher (P < 0.05) during the crop production period (recorded as CPP, lasting from June to September, 22.7%) than the non-crop production period (Non-CPP, 13.8%). The application of chemical fertilizer and manure and the high precipitation were assumed as the primary reason for the increased N deposition and increased riverine TN load during CPP. This study shows that inland plain agriculture practices might considerably influence the nearby forest-dominated watershed, and it is necessary to develop sustainable agriculture programs for reducing riverine N load. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

The study found that nitrogen deposition significantly impacts riverine nitrogen load, with a higher contribution during crop production periods. The use of chemical fertilizer and manure, along with high precipitation, are assumed to be the main reasons for increased nitrogen deposition and riverine nitrogen load during crop production.