Novel sinks for the atmospherically potent gas nitrous oxide
Novel sinks for the atmospherically potent gas nitrous oxide
Nitrous oxide (N2O) is a potent climate gas, with its strong warming potential and ozone-depleting properties both focusing research on N2O sources. While undersaturation in N2O have been reported in natural waters indicating sinks for N2O, most of these found in the surface ocean and shallow freshwaters remain unaccounted for. Although a sink for N2O through biological fixation has been observed in the Pacific, the regulation of N2O- compared to canonical N2 -fixation is unknown. Here I show that both N2O and N2 can be fixed by freshwater communities but with distinct seasonalities and temperature dependencies. N2O fixation appears less sensitive to temperature than N2 fixation, driving a strong sink for N2O in winter. Moreover, by quantifying both N2O and N2 fixation I show that, rather than N2O being first reduced to N2 through denitrification, N2O fixation is direct and could explain the widely reported N2O sinks in natural waters. N2O can be fixed into NH4 + , which could then be further oxidised to NO2 - and NO3 - and being available to the wider community. In the cold, total N2O reduction was higher and a higher proportion of the reduced N2O was conserved. In addition, with activity of nitrification not detected in most of the ponds and anammox not detected in any pond, denitrification seem to be the primary process producing both N2O and N2 . The availability of nitrate limits the temperature sensitivity of the production of N2O and N2 from denitrification, with production of both gases only sensitive to changes in temperature at high concentration of additional nitrate. With the high substrate, the net production ratio of N2O to N2 from denitrification increases at lower temperatures, which could provide more N2O relative to N2 for N fixation in the cold.
nitrogen cycling, Nitrous Oxide, Greenhouse gas, Denitrification, N fixation, Nitrification
Queen Mary University London
Si, Yueyue
da0cbb1d-cec8-426a-b537-4c7d4e2c1ef0
8 February 2024
Si, Yueyue
da0cbb1d-cec8-426a-b537-4c7d4e2c1ef0
Si, Yueyue
(2024)
Novel sinks for the atmospherically potent gas nitrous oxide.
Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
Nitrous oxide (N2O) is a potent climate gas, with its strong warming potential and ozone-depleting properties both focusing research on N2O sources. While undersaturation in N2O have been reported in natural waters indicating sinks for N2O, most of these found in the surface ocean and shallow freshwaters remain unaccounted for. Although a sink for N2O through biological fixation has been observed in the Pacific, the regulation of N2O- compared to canonical N2 -fixation is unknown. Here I show that both N2O and N2 can be fixed by freshwater communities but with distinct seasonalities and temperature dependencies. N2O fixation appears less sensitive to temperature than N2 fixation, driving a strong sink for N2O in winter. Moreover, by quantifying both N2O and N2 fixation I show that, rather than N2O being first reduced to N2 through denitrification, N2O fixation is direct and could explain the widely reported N2O sinks in natural waters. N2O can be fixed into NH4 + , which could then be further oxidised to NO2 - and NO3 - and being available to the wider community. In the cold, total N2O reduction was higher and a higher proportion of the reduced N2O was conserved. In addition, with activity of nitrification not detected in most of the ponds and anammox not detected in any pond, denitrification seem to be the primary process producing both N2O and N2 . The availability of nitrate limits the temperature sensitivity of the production of N2O and N2 from denitrification, with production of both gases only sensitive to changes in temperature at high concentration of additional nitrate. With the high substrate, the net production ratio of N2O to N2 from denitrification increases at lower temperatures, which could provide more N2O relative to N2 for N fixation in the cold.
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Published date: 8 February 2024
Keywords:
nitrogen cycling, Nitrous Oxide, Greenhouse gas, Denitrification, N fixation, Nitrification
Identifiers
Local EPrints ID: 500297
URI: http://eprints.soton.ac.uk/id/eprint/500297
PURE UUID: 4f0e4189-b817-49f4-a3a1-09ac1d2214f7
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Date deposited: 23 Apr 2025 17:03
Last modified: 24 Apr 2025 02:08
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Author:
Yueyue Si
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