Trace Gas Evolution in the Present and Past Atmosphere
Nitrous oxide (N2O) is a very important trace greenhouse gas in the atmosphere. With anincreasing atmospheric concentration of 327 ppb at present, and a warming potential 300times that of CO2, the signicance of N2O has been rapidly increasing since the 1950s. It isgenerally known that N2O primarily...
Main Author: | |
---|---|
Format: | Book |
Language: | English |
Published: |
The Niels Bohr Institute, Faculty of Science, University of Copenhagen
2016
|
Subjects: | |
Online Access: | https://curis.ku.dk/portal/da/publications/trace-gas-evolution-in-the-present-and-past-atmosphere(b4242ddb-bad3-4134-b97b-fafff4c2a205).html https://soeg.kb.dk/permalink/45KBDK_KGL/fbp0ps/alma99122096950905763 |
id |
ftcopenhagenunip:oai:pure.atira.dk:publications/b4242ddb-bad3-4134-b97b-fafff4c2a205 |
---|---|
record_format |
openpolar |
institution |
Open Polar |
collection |
University of Copenhagen: Research |
op_collection_id |
ftcopenhagenunip |
language |
English |
description |
Nitrous oxide (N2O) is a very important trace greenhouse gas in the atmosphere. With anincreasing atmospheric concentration of 327 ppb at present, and a warming potential 300times that of CO2, the signicance of N2O has been rapidly increasing since the 1950s. It isgenerally known that N2O primarily originates from microbial production in terrestrial andaquatic ecosystems. In this thesis I present measurements of the intramolecular distributionof 15 N in N2O given as site preference (difference in abundance of the isotopomers), σ 15 N bulk (average abundance of the isotopomers), and measurements of σ 18 O-N2O. The isotopes ofN2O are used in investigations of both the specic reactions pathways influencing N2O emissions and the general evolution of N2O.In Part II, I presents continuous incubation experiments with the two primary microbialcommunities responsible for N2O production. The two microbial communities have beenstudied numerous times, but to the best of our knowledge never continuously. Continuousmeasurements of the microbial evolution of N2O is possible due to the recent instrumentdevelopment of a cavity ringdown spectroscopy-based analyzer, which allows for continuousposition dependent 15 N measurements.Continuous incubation experiments are presented with nitrifying bacteria Nitrosomonas mobilis revealing strong indications of N2O production from different chemical reactions.The measurements revealed a three step site preference pattern in the range of nitricationand denitrication and we therefore suggest that Nitrosomonas mobilis is of the bacterialcommunity nitrifier denitrication. The experiments furthermore revealed the bacterialpotential for cyclic use of the most abundant substrate rather than the most energy effcient.Continuous incubation experiments with denitrifying bacteria are also presented with Pseudomonas fluorescens (producing and reducing N2O) and Pseudomonas chlororaphis(only producing N2O). Measurements revealed a clear transient pattern of KNO3 to N2Oand KNO3 to N2O to N2 for the two bacterial species, respectively. A Rayleigh type distillationmodel modied for isotopomers and simultaneous reduction, allowed for determinationof isotopic fractionation values during both production and reduction of N2O, comparableto previous studies.In Part III, I present measurements of ice core samples analyzed for isotopes of N2O. Icesamples from three time periods of the Holocene and one from the glacial were selectedand measured for isotopic composition of N2O using isotope ratio mass spectrometry. Theanalysis resulted in isotopic variations comparable with previous findings of site preference,σ 15 N bulk , and σ 18 O-N2O. Source identification analysis using the isotopic composition resultedin a discussion of the primary source region being nitrification in aquatic ecosystems,while inclusion of the stratospheric sink effect leads to heavy depletion in all isotopes, henceshifting the primary source region towards denitrication in terrestrial ecosystems.In Part IV, I present N2O measurements from eld studies performed 1) on the Arctictundra and 2) on an inclined temperate slope. 1) Previous studies has shown that largeamounts of N2O is being emitted after thawing of permafrost. We investigated a downslopesite covering a moisture gradient area in the arctic tundra. Moss-covered sites revealed highnitrication potential, low nitrate levels, and emission of denitrication marked N2O. Thenatural nitrogen cycle in the arctic is therefore hypothesized to reduce the atmospheric N2Oconcentration by denitrication, which contrasts the opening nitrogen cycle in temperate andtropical areas. 2) On an inclined temperate slope N2O emission variations were investigatedon a mesoscale range. A temperate changing interface with oxic nitrification enhancingconditions upslope and anoxic denitrification enhancing conditions downslope was discoveredwith high N2O production. |
format |
Book |
author |
Winther, Malte Nordmann |
spellingShingle |
Winther, Malte Nordmann Trace Gas Evolution in the Present and Past Atmosphere |
author_facet |
Winther, Malte Nordmann |
author_sort |
Winther, Malte Nordmann |
title |
Trace Gas Evolution in the Present and Past Atmosphere |
title_short |
Trace Gas Evolution in the Present and Past Atmosphere |
title_full |
Trace Gas Evolution in the Present and Past Atmosphere |
title_fullStr |
Trace Gas Evolution in the Present and Past Atmosphere |
title_full_unstemmed |
Trace Gas Evolution in the Present and Past Atmosphere |
title_sort |
trace gas evolution in the present and past atmosphere |
publisher |
The Niels Bohr Institute, Faculty of Science, University of Copenhagen |
publishDate |
2016 |
url |
https://curis.ku.dk/portal/da/publications/trace-gas-evolution-in-the-present-and-past-atmosphere(b4242ddb-bad3-4134-b97b-fafff4c2a205).html https://soeg.kb.dk/permalink/45KBDK_KGL/fbp0ps/alma99122096950905763 |
geographic |
Arctic |
geographic_facet |
Arctic |
genre |
Arctic Ice ice core permafrost Tundra |
genre_facet |
Arctic Ice ice core permafrost Tundra |
op_source |
Winther , M N 2016 , Trace Gas Evolution in the Present and Past Atmosphere . The Niels Bohr Institute, Faculty of Science, University of Copenhagen . < https://soeg.kb.dk/permalink/45KBDK_KGL/fbp0ps/alma99122096950905763 > |
op_rights |
info:eu-repo/semantics/closedAccess |
_version_ |
1766341413418565632 |
spelling |
ftcopenhagenunip:oai:pure.atira.dk:publications/b4242ddb-bad3-4134-b97b-fafff4c2a205 2023-05-15T15:10:22+02:00 Trace Gas Evolution in the Present and Past Atmosphere Winther, Malte Nordmann 2016 https://curis.ku.dk/portal/da/publications/trace-gas-evolution-in-the-present-and-past-atmosphere(b4242ddb-bad3-4134-b97b-fafff4c2a205).html https://soeg.kb.dk/permalink/45KBDK_KGL/fbp0ps/alma99122096950905763 eng eng The Niels Bohr Institute, Faculty of Science, University of Copenhagen info:eu-repo/semantics/closedAccess Winther , M N 2016 , Trace Gas Evolution in the Present and Past Atmosphere . The Niels Bohr Institute, Faculty of Science, University of Copenhagen . < https://soeg.kb.dk/permalink/45KBDK_KGL/fbp0ps/alma99122096950905763 > book 2016 ftcopenhagenunip 2021-09-23T17:57:34Z Nitrous oxide (N2O) is a very important trace greenhouse gas in the atmosphere. With anincreasing atmospheric concentration of 327 ppb at present, and a warming potential 300times that of CO2, the signicance of N2O has been rapidly increasing since the 1950s. It isgenerally known that N2O primarily originates from microbial production in terrestrial andaquatic ecosystems. In this thesis I present measurements of the intramolecular distributionof 15 N in N2O given as site preference (difference in abundance of the isotopomers), σ 15 N bulk (average abundance of the isotopomers), and measurements of σ 18 O-N2O. The isotopes ofN2O are used in investigations of both the specic reactions pathways influencing N2O emissions and the general evolution of N2O.In Part II, I presents continuous incubation experiments with the two primary microbialcommunities responsible for N2O production. The two microbial communities have beenstudied numerous times, but to the best of our knowledge never continuously. Continuousmeasurements of the microbial evolution of N2O is possible due to the recent instrumentdevelopment of a cavity ringdown spectroscopy-based analyzer, which allows for continuousposition dependent 15 N measurements.Continuous incubation experiments are presented with nitrifying bacteria Nitrosomonas mobilis revealing strong indications of N2O production from different chemical reactions.The measurements revealed a three step site preference pattern in the range of nitricationand denitrication and we therefore suggest that Nitrosomonas mobilis is of the bacterialcommunity nitrifier denitrication. The experiments furthermore revealed the bacterialpotential for cyclic use of the most abundant substrate rather than the most energy effcient.Continuous incubation experiments with denitrifying bacteria are also presented with Pseudomonas fluorescens (producing and reducing N2O) and Pseudomonas chlororaphis(only producing N2O). Measurements revealed a clear transient pattern of KNO3 to N2Oand KNO3 to N2O to N2 for the two bacterial species, respectively. A Rayleigh type distillationmodel modied for isotopomers and simultaneous reduction, allowed for determinationof isotopic fractionation values during both production and reduction of N2O, comparableto previous studies.In Part III, I present measurements of ice core samples analyzed for isotopes of N2O. Icesamples from three time periods of the Holocene and one from the glacial were selectedand measured for isotopic composition of N2O using isotope ratio mass spectrometry. Theanalysis resulted in isotopic variations comparable with previous findings of site preference,σ 15 N bulk , and σ 18 O-N2O. Source identification analysis using the isotopic composition resultedin a discussion of the primary source region being nitrification in aquatic ecosystems,while inclusion of the stratospheric sink effect leads to heavy depletion in all isotopes, henceshifting the primary source region towards denitrication in terrestrial ecosystems.In Part IV, I present N2O measurements from eld studies performed 1) on the Arctictundra and 2) on an inclined temperate slope. 1) Previous studies has shown that largeamounts of N2O is being emitted after thawing of permafrost. We investigated a downslopesite covering a moisture gradient area in the arctic tundra. Moss-covered sites revealed highnitrication potential, low nitrate levels, and emission of denitrication marked N2O. Thenatural nitrogen cycle in the arctic is therefore hypothesized to reduce the atmospheric N2Oconcentration by denitrication, which contrasts the opening nitrogen cycle in temperate andtropical areas. 2) On an inclined temperate slope N2O emission variations were investigatedon a mesoscale range. A temperate changing interface with oxic nitrification enhancingconditions upslope and anoxic denitrification enhancing conditions downslope was discoveredwith high N2O production. Book Arctic Ice ice core permafrost Tundra University of Copenhagen: Research Arctic |