1. Long-neglected contribution of nitrification to N 2 O emissions in the Yellow River.
- Author
-
Wang S, Li S, Ji M, Li J, Huang J, Dang Z, Jiang Z, Zhang S, Zhu X, and Ji G
- Subjects
- China, Air Pollutants analysis, Water Pollutants, Chemical analysis, Water Pollutants, Chemical metabolism, Bacteria metabolism, Nitrification, Nitrous Oxide analysis, Rivers chemistry, Environmental Monitoring, Denitrification
- Abstract
Rivers play a significant role in the global nitrous oxide (N
2 O) budget. However, the microbial sources and sinks of N2 O in river systems are not well understood or quantified, resulting in the prolonged neglect of nitrification. This study investigated the isotopic signatures of N2 O, thereby quantifying the microbial source of N2 O production and the degree of N2 O reduction in the Yellow River. Although denitrification has long been considered to be the dominant pathway of N2 O production in rivers, our findings indicated that denitrification only accounted for 18.3% (8.2%-43.0%) of the total contribution to N2 O production in the Yellow River, with 50.2%-80.2% being concurrently reduced. The denitrification contribution to N2 O production (R2 = 0.44, p < 0.01) and N2 O reduction degree (R2 = 0.70, p < 0.01) were positively related to the dissolved organic carbon (DOC) content. Similar to urban rivers and eutrophic lakes, denitrification was the primary process responsible for N2 O production (43.0%) in certain reaches with high organic content (DOC = 5.29 mg/L). Nevertheless, the denitrification activity was generally constrained by the availability of electron donors (average DOC = 2.51 mg/L) throughout the Yellow River basin. Consequently, nitrification emerged as the primary contributor in the well-oxygenated Yellow River. Additionally, our findings further distinguished the respective contribution of ammonia-oxidizing bacteria (AOB) and archaea (AOA) to N2 O emissions. Although AOB dominated the N2 O production in the Yellow River, the AOA specie abundance (AOA/(AOA + AOB)) contributed up to 32.6%, which resulted in 25.6% of the total nitrifier-produced N2 O, suggesting a significant occurrence of AOA in the oligotrophic Yellow River. Overall, this study provided a non-invasive approach for quantifying the microbial sources and sinks to N2 O emissions, and demonstrated the substantial role of nitrification in the large oligotrophic rivers., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)- Published
- 2024
- Full Text
- View/download PDF