In situ nitrogen removal processes in intertidal wetlands of the Yangtze Estuary

Zongxiao Zhang , Cheng Liu , Lijun Hou , Min Liu , Yanling Zheng , Guoyu Yin , Hongpo Dong , Xia Liang , Xiaofei Li , Dengzhou Gao


Received February 02, 2020,Revised , Accepted March 16, 2020, Available online April 09, 2020

Volume 32,2020,Pages 91-97

Estuarine and intertidal wetlands are important sites for nitrogen transformation and elimination. However, the factors controlling nitrogen removal processes remain largely uncertain in the highly dynamic environments. In this study, continuous-flow experiment combined with 15N isotope pairing technique was used to investigate in situ rates of denitrification and anaerobic ammonium oxidation (anammox) and their coupling with nitrification in intertidal wetlands of the Yangtze Estuary. The measured rates varied from below the detection limit to 152.39 µmol N/(m2·hr) for denitrification and from below the detection limit to 43.06 µmol N/(m2·hr) for anammox. The coupling links of nitrogen removal processes with nitrification were mainly dependent on nitrate, organic carbon, sulfide, dissolved oxygen and ferric iron in the estuarine and intertidal wetlands. Additionally, it was estimated that the actual nitrogen removal processes annually removed approximately 5% of the terrigenous inorganic nitrogen discharged into the Yangtze Estuary. This study gives new insights into nitrogen transformation and fate in the estuarine and intertidal wetlands.

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