N2 and N2O production and emission variation during the flood period of Poyang Lake (China)
Lakes are globally important sites to alleviate nitrogen (N) concentrations through gaseous N production and emission, and hydro-geomorphological characteristics can influence the spatial variation, patterns, and efficiency of N removal in lakes. In this study, gaseous N removal via dinitrogen (N2) and nitrous oxide (N2O) production and emission in different hydro-geomorphological areas of Poyang Lake, China, were investigated through direct measurement of excess dissolved N2 and N2O (ΔN2 and ΔN2O) using the N2:Ar ratio method and headspace equilibrium technique, respectively. The highest value of ΔN2 (75.2 ± 31.0 μmol N2 L−1) was observed in the open lake, while the lowest ΔN2 (47.2 ± 14.9 μmol N2 L−1) occurred in the south estuarine delta (p < 0.05). However, the distribution of ΔN2O was opposite to that of ΔN2 with the highest ΔN2O being observed in the south estuarine delta (5.1 ± 5.0 nmol N2O L−1). Gaseous N2 removal fraction (the ΔN2 proportion among the sum of dissolved inorganic nitrogen (DIN) concentration and ΔN2) varied from 36% in the south estuarine delta to 48% in the open lake, while N2O yield (the ΔN2O proportion among the sum of ΔN2 and ΔN2O) varied from 0.04‰ in the open lake to 0.10‰ in the south estuarine delta. Correlation analyses showed that NO3− was the main factor controlling N2O yield. This study confirmed that N removal fractions and patterns vary with different hydro-geomorphological areas.
KeywordsGaseous nitrogen removal Dinitrogen Nitrous oxide Floodplain lake
This study was financially supported by the National Natural Science Foundation of China (Nos. 41771519, 41671477 and 51839011), the Chinese Academy of Sciences Technology Service Network Program (STS) and Major Science and Technology Program for Water Pollution Control and Treatment (2017ZX07204005). We thank the Poyang Lake Laboratory for Wetland Ecosystem Research (PLLWER) for providing the instruments and labs. We sincerely thank Weitao Lin and Ting Liu for their assistance in field sampling and sample analyses. We also thank the anonymous reviewers for their careful review and suggestions.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflicts of interest.
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