12 Jan 2023
12 Jan 2023
Status: this preprint is open for discussion.

Evidence of Nitrogen Loss from Anaerobic Ammonium Oxidation Coupled with Ferric Iron Reduction in the Yellow River Wetland

Qingsong Guan1,2,3, Tao Li2,3, Yiqiao Zhou2,3, Fan Yang2,3, and Qingbin Li1 Qingsong Guan et al.
  • 1State key Laboratory of Hydroscience and Engineering, Beijing 100084, China
  • 2College of Application of Engineering, Henan University of Science and Technology, Sanmenxia 472000, China
  • 3Engineering Technology Research Center of Sanmenxia Yellow River Wetland Environmental Process and Ecological Restoration, Sanmenxia 472000, China

Abstract. Anaerobic ammonium oxidation coupled with iron(III) reduction (Feammox) is a recently discovered pathway of nitrogen removal. However, little is known about the pathways of N transformation via Feammox in the Yellow River wetland. In this study, the difference between Feammox in a natural wetland (site YJW) and a crop rotation wetland (site TEH) was researched using isotope tracing and metagenome techniques. The results revealed that Feammox occurred in TEH but not in YJW. The Feammox rates in the TEH samples were 0.02–0.13 mg N kg−1 d−1 in different depth intervals (0–5 cm, 5–10 cm, 10–20 cm, and 20–30 cm), and the maximum value for TEH occurred in the 5–10 cm depth interval. Iron reducing bacteria play an essential role in Feammox. Rotational tillage reduced the microbial diversity of the iron-reducing bacteria, but it increased the abundance of iron-reducing bacteria at the genus level, and the dominate iron-reducing bacteria responsible for the Feammox process were Anaeromyxobacter and Geobacter. The Feammox rate was less than the denitrification rate (0.55–1.09 mg N kg−1 d−1), an estimated nitrogen loss of 1.1–7.1 t N km−2 a−1 was associated with the Feammox in the wetland. However, the correlation between the functional genes of the iron-reducing bacteria and the rate remains unclear. Overall, the co-occurrence of ammonium oxidation and iron reduction suggest that Feammox can play an essential role in the pathway of nitrogen removal in the Yellow River wetland.

Qingsong Guan et al.

Status: open (until 25 Feb 2023)

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Qingsong Guan et al.

Qingsong Guan et al.


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Short summary
Rotational planting and harvesting increased the abundances of the iron-reducing bacteria, which led to a higher Feammox rate and a nitrogen loss of 21–27 %. The total nitrogen loss rate as a result of Feammox was estimated to be 1.1–7.1 t N km−2 a−1. The total nitrogen loss in the basin was about 313.5–2023.5 t N a−1. Anaeromyxobacter and Geobacter may be the major genus driving Feammox, but the functional genes leading to Feammox remain unclear.