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Article

Episodes 2019; 42(4): 333-341

Published online December 1, 2019

https://doi.org/10.18814/epiiugs/2019/019027

Copyright © International Union of Geological Sciences.

Nitrogen cycles within the stream-to-riparian continuum under flood waves

Haoyu Zhu1,3,4, Dongsheng Liu1,2,3*, Wenqing Shi1,3, and Qiuwen Chen1,3

1State Key Laboratory of Hydrology-Water Resources & Hydraulic Engineering, Nanjing Hydraulic Research Institute, Nanjing 210029, China
2College of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing 210098, China
3Center for Eco-Environmental Research, Nanjing Hydraulic Research Institute, Nanjing 210098, China; *Corresponding author, E-mail: dsliu@nhri.cn
4School of River and Ocean Engineering, Chongqing Jiaotong University, Chongqing 400074, China

Correspondence to:*E-mail: dsliu@nhri.cn

Received: September 19, 2019; Revised: November 11, 2019; Accepted: November 11, 2019

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

By using a 2D-coupled flow and solute transport and reaction model across the stream-to-riparian continuum, this paper systematically studied the nitrogen-cycling processes driven by a flood wave and their spatial-temporal distributions. The influences on hyporheic nitrogen removal of different waves that vary by amplitude (A), duration (T), wave-type parameter (r) and rising duration (tp) were investigated. During the surface-water-infiltration period, the aerobic respiration, nitrification and denitrification in the hyporheic zone were gradually enhanced, and aerobic respiration was dominant. During the groundwater-backflow period, the reactions gradually weakened, and the role of denitrification was improved. The consumption of each solute continuously increased in the whole process, and the groundwater-backflow period corresponded to a larger consumption but at a smaller consumption rate. The reaction rates in space from high to low were as follows: riparian phreatic zone > variable saturated zone > stream bed. Hyporheic nitrogen removal increased with increasing A, T and tp and with decreasing r, which was contrary to the change rule of nitrogen removal efficiency. The hyporheic nitrogen removal exhibited a good linear relationship with the polynomial ‘A*T*tp/r’, which had great predictive significance.