Articles | Volume 19, issue 19
https://doi.org/10.5194/amt-19-6311-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/amt-19-6311-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
05 Oct 2026
Research article |
| 05 Oct 2026
| 05 Oct 2026
On-line analysis of N2O isotopic composition during biological nitrogen removal in wastewater treatment to disentangle production and reduction processes
Empa, Laboratory for Air Pollution/Environmental Technology, 8600 Dübendorf, Switzerland
Laurence Strubbe
Eawag, Swiss Federal Institute of Aquatic Science and Technology, Überlandstrasse 133, 8600 Dübendorf, Switzerland
Vito, Flemish Institute for Technological Research, Mol, 2400, Belgium
Paul M. Magyar
Empa, Laboratory for Air Pollution/Environmental Technology, 8600 Dübendorf, Switzerland
Adriano Joss
Eawag, Swiss Federal Institute of Aquatic Science and Technology, Überlandstrasse 133, 8600 Dübendorf, Switzerland
Andreas Froemelt
Eawag, Swiss Federal Institute of Aquatic Science and Technology, Überlandstrasse 133, 8600 Dübendorf, Switzerland
André Kupferschmid
Empa, Transport at Nanoscale Interfaces, 8600 Dübendorf, Switzerland
Klaus-Holger Knorr
Institute of Landscape Ecology, Ecohydrology & Biogeochemistry Group, University of Münster, 48149 Münster, Germany
Joachim Mohn
Empa, Laboratory for Air Pollution/Environmental Technology, 8600 Dübendorf, Switzerland
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Noémy Chénier, Paul M. Magyar, Jakob Zopfi, Claudia Frey, Thomas Kuhn, Moritz F. Lehmann, and Joachim Mohn
Biogeosciences, 23, 6705–6724, https://doi.org/10.5194/bg-23-6705-2026, https://doi.org/10.5194/bg-23-6705-2026, 2026
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N₂O is a greenhouse gas produced by microbes during nitrogen cycling. We studied two bacterial species and found that the isotope signatures of the N₂O they produced changed strongly depending on growth conditions and cell activity. Early during growth, the distribution of N isotopes within the N₂O molecule also changed unexpectedly. These results show that N₂O isotope signatures are more variable than previously assumed and depend strongly on physiology.
Henning Teickner, Julien Arsenault, Mariusz Gałka, and Klaus-Holger Knorr
Biogeosciences, 23, 5549–5570, https://doi.org/10.5194/bg-23-5549-2026, https://doi.org/10.5194/bg-23-5549-2026, 2026
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We present a method to estimate the degree of decomposition (fraction of initial mass remaining) of peat from mid-infrared spectra, which also allows to reconstruct the initial mass (aboveground net primary production). Both quantities are required to estimate the mass and carbon balance of peatlands and are useful to model peat physical and hydraulic properties. The approach is therefore useful to test and improve peatland models and our understanding of the long-term peatland carbon cycle.
Paul M. Magyar, Nico Kueter, Simone Brunamonti, Naizhong Zhang, Ivan Prokhorov, Noémy Chénier, Lukas Emmenegger, Béla Tuzson, and Joachim Mohn
Atmos. Meas. Tech., 19, 5267–5280, https://doi.org/10.5194/amt-19-5267-2026, https://doi.org/10.5194/amt-19-5267-2026, 2026
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Human activity drives increases in atmospheric nitrous oxide. Stable isotopes help trace the pathways involved. We developed a reliable way to calibrate measurements of rare isotopic variants of nitrous oxide so results from different labs can be compared. By heating nitrous oxide with a catalyst, the molecules reach well-defined equilibrium patterns suitable as a reference. To measure these isotopic variants quickly and precisely, we improved a laser-based measurement approach.
Nicolas Behrens, Klaus-Holger Knorr, Christoph Rückriem, and Mana Gharun
Biogeosciences, 23, 5071–5094, https://doi.org/10.5194/bg-23-5071-2026, https://doi.org/10.5194/bg-23-5071-2026, 2026
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We analysed carbon fluxes and their response to climate in a drained bog. Annual budgets varied from net emissions to near-neutral. Warm spring temperatures increased CO2 uptake, a warm autumn increased emissions. Atmospheric drought early in the year reduced CO2 uptake more than later. Our results show that carbon fluxes from drained bogs are variable and the timing of climate anomalies controls their impact on carbon fluxes. This will be increasingly important with ongoing climate warming.
Lina Oskamp, Marta Pérez Rodríguez, Adelina Calean, Olaf Rienitz, Klaus-Holger Knorr, Kazumasa Oguri, Masashi Tsuchiya, Marco Benkhettab Sindlev, Stephan Krisch, Arianna Olivelli, Frank Wenzhöfer, Ronnie N. Glud, and Harald Biester
EGUsphere, https://doi.org/10.5194/egusphere-2026-3608, https://doi.org/10.5194/egusphere-2026-3608, 2026
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Lead (Pb) isotopes in marine sediments are used as source tracers of Pb in the oceans. Recent studies suggested Pb isotope exchange on sinking particles, but it remained unknown if this affects isotope signatures. Our study on deep-sea sediments of the South Atlantic Ocean reveals that Pb isotope separation occurs in sinking particles and depends on the intensity of primary productivity.
Julius C. Havsteen, Mehr Fatima, Simone Brunamonti, Andrea Pogány, Thomas Hausmaninger, Benjamin Wolf, Reinhard Well, and Joachim Mohn
Atmos. Meas. Tech., 19, 3557–3580, https://doi.org/10.5194/amt-19-3557-2026, https://doi.org/10.5194/amt-19-3557-2026, 2026
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We present a new correction and calibration protocol to improve the accuracy of nitrous oxide isotope measurements obtained using laser spectroscopy. Through laboratory experiments, spectral simulations, and an automated MATLAB (Matrix Laboratory) reduction scheme, we identify and correct biases caused by matrix gas composition, spectral interferences and instrument variability. This protocol enables researchers to produce more reliable isotope data and supports standardised isotope analyses across laboratories.
Henning Teickner and Klaus-Holger Knorr
SOIL, 12, 497–519, https://doi.org/10.5194/soil-12-497-2026, https://doi.org/10.5194/soil-12-497-2026, 2026
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We developed models that predict physical and chemical peat properties from mid-infrared spectra (MIRS). These peat properties are necessary for modeling peatland dynamics. Compared to direct measurements of these properties, measurements of MIRS require less sample material and save time. Unlike existing models that focus on peat, the models developed here are openly available, relatively easy to use and have basic quality checks and estimates for prediction errors.
Henning Teickner, Edzer Pebesma, and Klaus-Holger Knorr
Earth Syst. Dynam., 16, 891–914, https://doi.org/10.5194/esd-16-891-2025, https://doi.org/10.5194/esd-16-891-2025, 2025
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The Holocene Peatland Model (HPM) is a widely used peatland model to understand and predict long-term peatland dynamics. Here, we test whether the HPM can predict Sphagnum litterbag decomposition rates from oxic to anoxic conditions. Our results indicate that decomposition rates change more gradually from oxic to anoxic conditions and may be underestimated under anoxic conditions, possibly because the effect of water table fluctuations on decomposition rates is not considered.
Henning Teickner, Edzer Pebesma, and Klaus-Holger Knorr
Biogeosciences, 22, 417–433, https://doi.org/10.5194/bg-22-417-2025, https://doi.org/10.5194/bg-22-417-2025, 2025
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Decomposition rates for Sphagnum mosses, the main peat-forming plants in northern peatlands, are often derived from litterbag experiments. Here, we estimate initial leaching losses from available Sphagnum litterbag experiments and analyze how decomposition rates are biased when initial leaching losses are ignored. Our analyses indicate that initial leaching losses range between 3 to 18 mass-% and that this may result in overestimated mass losses when extrapolated to several decades.
Carrie L. Thomas, Boris Jansen, Sambor Czerwiński, Mariusz Gałka, Klaus-Holger Knorr, E. Emiel van Loon, Markus Egli, and Guido L. B. Wiesenberg
Biogeosciences, 20, 4893–4914, https://doi.org/10.5194/bg-20-4893-2023, https://doi.org/10.5194/bg-20-4893-2023, 2023
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Peatlands are vital terrestrial ecosystems that can serve as archives, preserving records of past vegetation and climate. We reconstructed the vegetation history over the last 2600 years of the Beerberg peatland and surrounding area in the Thuringian Forest in Germany using multiple analyses. We found that, although the forest composition transitioned and human influence increased, the peatland remained relatively stable until more recent times, when drainage and dust deposition had an impact.
Laura Clark, Ian B. Strachan, Maria Strack, Nigel T. Roulet, Klaus-Holger Knorr, and Henning Teickner
Biogeosciences, 20, 737–751, https://doi.org/10.5194/bg-20-737-2023, https://doi.org/10.5194/bg-20-737-2023, 2023
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We determine the effect that duration of extraction has on CO2 and CH4 emissions from an actively extracted peatland. Peat fields had high net C emissions in the first years after opening, and these then declined to half the initial value for several decades. Findings contribute to knowledge on the atmospheric burden that results from these activities and are of use to industry in their life cycle reporting and government agencies responsible for greenhouse gas accounting and policy.
Matthias Koschorreck, Klaus Holger Knorr, and Lelaina Teichert
Biogeosciences, 19, 5221–5236, https://doi.org/10.5194/bg-19-5221-2022, https://doi.org/10.5194/bg-19-5221-2022, 2022
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At low water levels, parts of the bottom of rivers fall dry. These beaches or mudflats emit the greenhouse gas carbon dioxide (CO2) to the atmosphere. We found that those emissions are caused by microbial reactions in the sediment and that they change with time. Emissions were influenced by many factors like temperature, water level, rain, plants, and light.
Henning Teickner and Klaus-Holger Knorr
SOIL, 8, 699–715, https://doi.org/10.5194/soil-8-699-2022, https://doi.org/10.5194/soil-8-699-2022, 2022
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The chemical quality of biomass can be described with holocellulose (relatively easily decomposable by microorganisms) and Klason lignin (relatively recalcitrant) contents. Measuring both is laborious. In a recent study, models have been proposed which can predict both quicker from mid-infrared spectra. However, it has not been analyzed if these models make correct predictions for biomass in soils and how to improve them. We provide such a validation and a strategy for their improvement.
Cordula Nina Gutekunst, Susanne Liebner, Anna-Kathrina Jenner, Klaus-Holger Knorr, Viktoria Unger, Franziska Koebsch, Erwin Don Racasa, Sizhong Yang, Michael Ernst Böttcher, Manon Janssen, Jens Kallmeyer, Denise Otto, Iris Schmiedinger, Lucas Winski, and Gerald Jurasinski
Biogeosciences, 19, 3625–3648, https://doi.org/10.5194/bg-19-3625-2022, https://doi.org/10.5194/bg-19-3625-2022, 2022
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Methane emissions decreased after a seawater inflow and a preceding drought in freshwater rewetted coastal peatland. However, our microbial and greenhouse gas measurements did not indicate that methane consumers increased. Rather, methane producers co-existed in high numbers with their usual competitors, the sulfate-cycling bacteria. We studied the peat soil and aimed to cover the soil–atmosphere continuum to better understand the sources of methane production and consumption.
Liam Heffernan, Maria A. Cavaco, Maya P. Bhatia, Cristian Estop-Aragonés, Klaus-Holger Knorr, and David Olefeldt
Biogeosciences, 19, 3051–3071, https://doi.org/10.5194/bg-19-3051-2022, https://doi.org/10.5194/bg-19-3051-2022, 2022
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Permafrost thaw in peatlands leads to waterlogged conditions, a favourable environment for microbes producing methane (CH4) and high CH4 emissions. High CH4 emissions in the initial decades following thaw are due to a vegetation community that produces suitable organic matter to fuel CH4-producing microbes, along with warm and wet conditions. High CH4 emissions after thaw persist for up to 100 years, after which environmental conditions are less favourable for microbes and high CH4 emissions.
Ramona J. Heim, Andrey Yurtaev, Anna Bucharova, Wieland Heim, Valeriya Kutskir, Klaus-Holger Knorr, Christian Lampei, Alexandr Pechkin, Dora Schilling, Farid Sulkarnaev, and Norbert Hölzel
Biogeosciences, 19, 2729–2740, https://doi.org/10.5194/bg-19-2729-2022, https://doi.org/10.5194/bg-19-2729-2022, 2022
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Fires will probably increase in Arctic regions due to climate change. Yet, the long-term effects of tundra fires on carbon (C) and nitrogen (N) stocks and cycling are still unclear. We investigated the long-term fire effects on C and N stocks and cycling in soil and aboveground living biomass.
We found that tundra fires did not affect total C and N stocks because a major part of the stocks was located belowground in soils which were largely unaltered by fire.
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Short summary
We monitored nitrous oxide in a pilot wastewater treatment plant in real time to understand how microbes produce and remove this greenhouse gas. We designed and tested a laser-based analytical setup, with which we were able to show that denitrification is the main source of nitrous oxide emissions and that low oxygen concentrations enhances nitrous oxide removal. Our approach offers a new way to monitor the wastewater treatment processes and to cut climate-relevant nitrous oxide emissions.
We monitored nitrous oxide in a pilot wastewater treatment plant in real time to understand how...
