Spatial-temporal characteristics of nitrogen degradation in typical Rivers of Taihu Lake Basin, China

Abstract

In this study, we focus on the measurement of different nitrogen (N) forms and investigate the spatial-temporal variability of degradation coefficient in river channels. We aim to provide a new approach of deriving in-situ degradation coefficients of different N forms, and highlight factors that determine the spatial-temporal variability of degradation coefficients. Our results are based on a two-year field survey in 34 channels around the Taihu Lake Basin, eastern China. The derived degradation coefficients of different N forms based our newly-developed experimental device are: degradation coefficients of TN, NH₄⁺-N and NO₃-N range from 0.006-0.449 d^-1, 0.022-1.175 d^-1 and -0.096-2.402 d^-1, respectively. The degradation coefficients of N show strong dependence on N concentration and water temperature. The seasonal difference of water temperature and N concentration leads to spatial-temporal variability of degradation coefficients. The derived degradation coefficients of N are further verified through one-dimensional water quality model simulations. The degradation coefficient obtained in this study and the influencing factors of its spatial-temporal variability provide invaluable reference for studies in aquatic environment.

Keywords: Dissolved inorganic nitrogen degradation; Spatial-temporal variation; Taihu Lake Basin; Urbanization.