Arrhenius equation construction and nitrate source identification of denitrification at the Lake Taihu sediment − water interface with 15 N isotope

Abstract

Total nitrogen in Taihu Lake, China has gradually decreased since 2015 while the total phosphorus concentration has exhibited an increasing trend, indicating an asynchronous change. The dominant nitrogen removal process in freshwater ecosystems is denitri cation which primarily occurs at the sediment-water interface. In this study, 15 N isotope incubation experiments were attempted to analyze the effect of water temperature on denitri cation, to construct the regional denitri cation Arrhenius equations considering water temperature, and to identify the nitrate source of denitri cation in Lake Taihu sediments. The results indicated that the potential N 2 production rates and denitri cation rates generally decreased in the west to east direction, which was signi cantly positively correlated with the nitrate concentration of overlying water by Pearson correlation coe cient analysis (P < 0.05). In addition, when the water temperature was lower than 30°C, the rates of the potential N 2 production and denitri cation were higher with an increase in water temperature, but when the water temperature was overhigh, denitri cation was inhibited. The ratio of the total denitri cation rate of nitrate from the water column in the sediment to the total denitri cation rate during the incubation experiment was above 0.5 at each sampling site. This indicated that the denitri cation in the Lake Taihu sediment primarily occurred at the expense of nitrate from the water column. The research results of Arrhenius equation construction and nitrate source identi cation of denitization can be applied to improve the accuracy of water quality model of Taihu Lake, which is of great signi cance to improve Taihu Lake water quality, and can act as a reference for the water environment treatment of other shallow eutrophic lakes in China and abroad.