N2O production by heterotrophic N transformations in a semiarid soil

Applying abundant manure to soils can accelerate nitrogen transformations and nitrous oxide (N2O) emissions. We conducted a laboratory incubation to examine the turnover of labile N in manured soils. Soils were collected from agricultural fields that had recently received spring-injected liquid manure with or without admixing nitrification inhibitors. Bands and interbands of the manure plots were incubated separately. Time courses of ammonium (NH4+) and nitrate (NO3-) were used to derive and contrast zero-, first- and second-order kinetics models. We found that nitrification rates were consistently better represented by first-order kinetics (k1). Furthermore, across all evaluated soils, the dependency of nitrification rate (k1 of NH4+) on initial NH4+ concentration was modelled by Michaelis-Menten kinetics reasonably well, with an affinity (Km) of 63 mg N kg-1 soil (R2= 0.82). Compared to the manure interbands, the initially NH4-enriched bands had a much faster nitrification rate, with half-life for NH4+ of only 4 days and rapid k1 (0.186 versus 0.011 day-1). Soil N substrate and k1 exerted control on N2O production. Nitrous oxide production increased linearly with both measured NH4+ intensity (R2= 0.47) and modelled k1–NH4+ (R2= 0.48). Conversely, N2O production increased non-linearly with NO3- intensity (R2= 0.68), where high NO3- caused a saturation plateau with a threshold of 96 mg N kg-1 day-1 – beyond which no additional N2O was produced. During peak N transformations, measured N2O-N flux was 1.4±0.3% of the inorganic N undergoing nitrification. Heavily manured soils exhibited augmented N turnover that increased N2O fluxes, but inhibitors reduced these emissions by half.

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Biological nitrification inhibition in the rhizosphere: determining interactions and impact on microbially mediated processes and potential applications

FEMS Microbiology Reviews ◽

10.1093/femsre/fuaa037 ◽

2020 ◽

Vol 44 (6) ◽

pp. 874-908

Author(s):

Pierfrancesco Nardi ◽

Hendrikus J Laanbroek ◽

Graeme W Nicol ◽

Giancarlo Renella ◽

Massimiliano Cardinale ◽

...

Keyword(s):

Ammonia Oxidation ◽

Natural Phenomenon ◽

Nitrification Inhibitors ◽

Nitrification Inhibition ◽

Microbial Conversion ◽

N Losses ◽

N2o Production ◽

N Transformations ◽

Potential Applications ◽

Biological Nitrification

ABSTRACT Nitrification is the microbial conversion of reduced forms of nitrogen (N) to nitrate (NO3−), and in fertilized soils it can lead to substantial N losses via NO3− leaching or nitrous oxide (N2O) production. To limit such problems, synthetic nitrification inhibitors have been applied but their performance differs between soils. In recent years, there has been an increasing interest in the occurrence of biological nitrification inhibition (BNI), a natural phenomenon according to which certain plants can inhibit nitrification through the release of active compounds in root exudates. Here, we synthesize the current state of research but also unravel knowledge gaps in the field. The nitrification process is discussed considering recent discoveries in genomics, biochemistry and ecology of nitrifiers. Secondly, we focus on the ‘where’ and ‘how’ of BNI. The N transformations and their interconnections as they occur in, and are affected by, the rhizosphere, are also discussed. The NH4+ and NO3− retention pathways alternative to BNI are reviewed as well. We also provide hypotheses on how plant compounds with putative BNI ability can reach their targets inside the cell and inhibit ammonia oxidation. Finally, we discuss a set of techniques that can be successfully applied to solve unresearched questions in BNI studies.

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Model Predicted N2O Production from Membrane-Aerated Biofilm Reactor is Greatly Affected by Biofilm Property Settings

Chemosphere ◽

10.1016/j.chemosphere.2021.130861 ◽

2021 ◽

pp. 130861

Author(s):

Xueming Chen ◽

Pengfei Huo ◽

Jinzhong Liu ◽

Fuyi Li ◽

Linyan Yang ◽

...

Keyword(s):

Biofilm Reactor ◽

N2o Production

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Microbial N2O consumption in and above marine N2O production hotspots

The ISME Journal ◽

10.1038/s41396-020-00861-2 ◽

2020 ◽

Author(s):

Xin Sun ◽

Amal Jayakumar ◽

John C. Tracey ◽

Elizabeth Wallace ◽

Colette L. Kelly ◽

...

Keyword(s):

Kinetic Parameters ◽

Substrate Affinity ◽

N2o Production ◽

Anoxic Waters ◽

Production And Consumption ◽

Consumption Rates ◽

Anoxic Zones ◽

First Time ◽

Microbial N

AbstractThe ocean is a net source of N2O, a potent greenhouse gas and ozone-depleting agent. However, the removal of N2O via microbial N2O consumption is poorly constrained and rate measurements have been restricted to anoxic waters. Here we expand N2O consumption measurements from anoxic zones to the sharp oxygen gradient above them, and experimentally determine kinetic parameters in both oxic and anoxic seawater for the first time. We find that the substrate affinity, O2 tolerance, and community composition of N2O-consuming microbes in oxic waters differ from those in the underlying anoxic layers. Kinetic parameters determined here are used to model in situ N2O production and consumption rates. Estimated in situ rates differ from measured rates, confirming the necessity to consider kinetics when predicting N2O cycling. Microbes from the oxic layer consume N2O under anoxic conditions at a much faster rate than microbes from anoxic zones. These experimental results are in keeping with model results which indicate that N2O consumption likely takes place above the oxygen deficient zone (ODZ). Thus, the dynamic layer with steep O2 and N2O gradients right above the ODZ is a previously ignored potential gatekeeper of N2O and should be accounted for in the marine N2O budget.

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Soil gross nitrogen transformations in forestland and cropland of Regosols

Scientific Reports ◽

10.1038/s41598-020-80395-x ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Xiao Ren ◽

Jinbo Zhang ◽

Hamidou Bah ◽

Christoph Müller ◽

Zucong Cai ◽

...

Keyword(s):

Land Use ◽

Southwest China ◽

Nitrification Rate ◽

Land Uses ◽

Nitrogen Transformations ◽

N Losses ◽

Retention Capacity ◽

N Transformations ◽

Autotrophic Nitrification ◽

Land Use Types

AbstractSoil gross nitrogen (N) transformations could be influenced by land use change, however, the differences in inherent N transformations between different land use soils are still not well understood under subtropical conditions. In this study, an 15N tracing experiment was applied to determine the influence of land uses on gross N transformations in Regosols, widely distributed soils in Southwest China. Soil samples were taken from the dominant land use types of forestland and cropland. In the cropland soils, the gross autotrophic nitrification rates (mean 14.54 ± 1.66 mg N kg−1 day−1) were significantly higher, while the gross NH4+ immobilization rates (mean 0.34 ± 0.10 mg N kg−1 day−1) were significantly lower than those in the forestland soils (mean 1.99 ± 0.56 and 6.67 ± 0.74 mg N kg−1 day−1, respectively). The gross NO3− immobilization and dissimilatory NO3− reduction to NH4+ (DNRA) rates were not significantly different between the forestland and cropland soils. In comparison to the forestland soils (mean 0.51 ± 0.24), the cropland soils had significantly lower NO3− retention capacities (mean 0.01 ± 0.01), indicating that the potential N losses in the cropland soils were higher. The correlation analysis demonstrated that soil gross autotrophic nitrification rate was negatively and gross NH4+ immobilization rate was positively related to the SOC content and C/N ratio. Therefore, effective measures should be taken to increase soil SOC content and C/N ratio to enhance soil N immobilization ability and NO3− retention capacity and thus reduce NO3− losses from the Regosols.

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Nitrogen isotope effects can be used to diagnose N transformations in wastewater anammox systems

Scientific Reports ◽

10.1038/s41598-021-87184-0 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Paul M. Magyar ◽

Damian Hausherr ◽

Robert Niederdorfer ◽

Nicolas Stöcklin ◽

Jing Wei ◽

...

Keyword(s):

Isotope Effect ◽

Isotope Composition ◽

Isotope Effects ◽

Nitrogen Isotope ◽

Anammox Bacteria ◽

Ammonium Oxidation ◽

Experimental Conditions ◽

N Transformations ◽

Natural Systems ◽

Inverse Isotope Effect

AbstractAnaerobic ammonium oxidation (anammox) plays an important role in aquatic systems as a sink of bioavailable nitrogen (N), and in engineered processes by removing ammonium from wastewater. The isotope effects anammox imparts in the N isotope signatures (15N/14N) of ammonium, nitrite, and nitrate can be used to estimate its role in environmental settings, to describe physiological and ecological variations in the anammox process, and possibly to optimize anammox-based wastewater treatment. We measured the stable N-isotope composition of ammonium, nitrite, and nitrate in wastewater cultivations of anammox bacteria. We find that the N isotope enrichment factor 15ε for the reduction of nitrite to N2 is consistent across all experimental conditions (13.5‰ ± 3.7‰), suggesting it reflects the composition of the anammox bacteria community. Values of 15ε for the oxidation of nitrite to nitrate (inverse isotope effect, − 16 to − 43‰) and for the reduction of ammonium to N2 (normal isotope effect, 19–32‰) are more variable, and likely controlled by experimental conditions. We argue that the variations in the isotope effects can be tied to the metabolism and physiology of anammox bacteria, and that the broad range of isotope effects observed for anammox introduces complications for analyzing N-isotope mass balances in natural systems.

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Nitrogen cycling in Sandusky Bay, Lake Erie: oscillations between strong and weak export and implications for harmful algal blooms

Biogeosciences ◽

10.5194/bg-15-2891-2018 ◽

2018 ◽

Vol 15 (9) ◽

pp. 2891-2907 ◽

Cited By ~ 14

Author(s):

Kateri R. Salk ◽

George S. Bullerjahn ◽

Robert Michael L. McKay ◽

Justin D. Chaffin ◽

Nathaniel E. Ostrom

Keyword(s):

Harmful Algal Blooms ◽

Algal Blooms ◽

Lake Erie ◽

N Uptake ◽

N Fixation ◽

N Budget ◽

N2o Production ◽

N Removal ◽

Uptake Rates ◽

N Loading

Abstract. Recent global water quality crises point to an urgent need for greater understanding of cyanobacterial harmful algal blooms (cHABs) and their drivers. Nearshore areas of Lake Erie such as Sandusky Bay may become seasonally limited by nitrogen (N) and are characterized by distinct cHAB compositions (i.e., Planktothrix over Microcystis). This study investigated phytoplankton N uptake pathways, determined drivers of N depletion, and characterized the N budget in Sandusky Bay. Nitrate (NO3-) and ammonium (NH4+) uptake, N fixation, and N removal processes were quantified by stable isotopic approaches. Dissimilatory N reduction was a relatively modest N sink, with denitrification, anammox, and N2O production accounting for 84, 14, and 2 % of sediment N removal, respectively. Phytoplankton assimilation was the dominant N uptake mechanism, and NO3- uptake rates were higher than NH4+ uptake rates. Riverine N loading was sometimes insufficient to meet assimilatory and dissimilatory demands, but N fixation alleviated this deficit. N fixation made up 23.7–85.4 % of total phytoplankton N acquisition and indirectly supports Planktothrix blooms. However, N fixation rates were surprisingly uncorrelated with NO3- or NH4+ concentrations. Owing to temporal separation in sources and sinks of N to Lake Erie, Sandusky Bay oscillates between a conduit and a filter of downstream N loading to Lake Erie, delivering extensively recycled forms of N during periods of low export. Drowned river mouths such as Sandusky Bay are mediators of downstream N loading, but climate-change-induced increases in precipitation and N loading will likely intensify N export from these systems.

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