Simplified preparation for the δ15N-analysis in soil NO3- by the denitrifier method

Mørkved, Pål Tore; Dörsch, Peter; Søvik, Anne Kristine; Bakken, Lars R.

doi:10.1016/j.soilbio.2007.02.004

Cited by 14 publications

(31 citation statements)

References 23 publications

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“…This is consistent with previous research that showed only 30-50% of NO 3 -was denitrified over 50 h in a 2 M KCl matrix, while there was no change in a 0.1 M matrix. [17] The difference between the expected N 2 O production and measured N 2 O production apparent in Fig. 3 may be the result of incomplete conversion of sample NO 3 -into N 2 O due to the KCl matrix or, alternatively, a secondary reaction related to high KCl concentrations may have removed N 2 O from the headspace of the vial (e.g., chemodenitrification).…”

Section: Effects Of Kcl On Nomentioning

confidence: 88%

“…These reference standards were chosen because they represent the two endmembers of our isotope calibration curve and they do not contain any excess 17 O isotope, which can introduce error into δ 15 N measurements of NO 3 -. [14] The reference samples were prepared in DIW as well as in a 1 M KCl solution made with Fisher-Reagent KCl, and then precisely mixed to create a gradient of isotope working standards in both DIW and KCl matrices.…”

Section: Experiments 4: Effect Of Kcl Molarity On Isotope Fractionationmentioning

confidence: 99%

“…3 may be the result of incomplete conversion of sample NO 3 -into N 2 O due to the KCl matrix or, alternatively, a secondary reaction related to high KCl concentrations may have removed N 2 O from the headspace of the vial (e.g., chemodenitrification). Morkved et al [17] hypothesized that, when creating a soil slurry, the presence of soil denitrifiers can reduce headspace N 2 O to N 2 gas over time, and this needs to be taken into account for soil extracts. We are conducting additional experiments to determine the underlying causes of lower than expected N 2 O production in high molarity KCl extracts.…”

Section: Effects Of Kcl On Nomentioning

confidence: 99%

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Correcting for background nitrate contamination in KCl-extracted samples during isotopic analysis of oxygen and nitrogen by the denitrifier method

Bell

Sickman

2014

Rapid Commun. Mass Spectrom.

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RATIONALE:Previous research has shown that the denitrifying bacteria Pseudomonas chlororaphis ssp. aureofaciens (P. aureofaciens) can be used to measure the δ 15 N and δ 18 O values of extracted soil nitrate (NO 3 -) by isotope ratio mass spectrometry. We discovered that N 2 O production from reference blanks made in 1 M KCl increased relative to blanks made of deionized water (DIW). Further investigation showed that isotopic standards made in KCl yielded δ 15 N and δ 18 O values different from the standards prepared in DIW. METHODS: Three grades of crystalline KCl were dissolved in DIW to create solutions of increasing molarity (0.1 M to 2 M), which were added to P. aureofaciens broth and measured as blanks. Reference standards USGS-32, USGS-34, and USGS-35 were then dissolved in a range of KCl concentrations to measure isotopic responses to changing KCl molarity. Reference blanks and standards created in DIW were analyzed as controls to measure the impact of KCl on the δ 15 N and δ 18 O values. RESULTS: The amount of N 2 O in the KCl blanks increased linearly with increasing molarity, but at different rates for each KCl grade. The isotopic values of the reference standards measured in KCl were systematically different from those measured in DIW, suggesting contamination by background NO 3 -in the KCl reagents. However, we also noted reduced conversion of NO 3 -into N 2 O as the KCl molarity increased, suggesting there is a physiological response of P. aureofaciens to KCl. CONCLUSIONS: There is a small amount of NO 3 -present in crystalline KCl, which can bias isotopic measurement of NO 3 -at low sample concentrations. This can be minimized by making standards and blanks in the same KCl as is used in samples, diluting all samples and standards to the appropriate NO 3 -concentration using matched KCl solutions, and adding samples and standards to the broth at a constant volume to standardize the KCl molarity in the reaction vial. Copyright © 2014 John Wiley & Sons, Ltd.Mass spectrometry of the stable isotopes of oxygen (O) and nitrogen (N) of nitrate (NO 3 -) through bacterial denitrification has advanced our understanding of reactive nitrogen in terrestrial, freshwater and marine ecosystems. [1][2][3][4] Anthropogenic and naturally produced NO 3 -have distinct isotopic signatures of both δ 15 N and δ 18 O. [5] Mixing models based on these values and background NO 3 -concentrations can help identify the sources and transformation of nitrogen within a local system. [4,6,7] Recent studies have analyzed potassium chloride (KCl) solutions containing NO 3 -extracted from soil samples using the denitrifying bacteria Pseudomonas chlororaphis ssp. aureofaciens (P. aureofaciens) without identifying any isotopic artifacts, [7][8][9] although earlier work by Stark and Hart [10] measured NO 3 -contamination by 2 M KCl while performing diffusion digests. While conducting similar analyses on KCl-extracted soils in southern California, we noted an increase in N 2 O production in blanks prepared in KCl and worrying shifts in th...

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Section: Effects Of Kcl On Nomentioning

confidence: 88%

Section: Experiments 4: Effect Of Kcl Molarity On Isotope Fractionationmentioning

confidence: 99%

Section: Effects Of Kcl On Nomentioning

confidence: 99%

See 1 more Smart Citation

Correcting for background nitrate contamination in KCl-extracted samples during isotopic analysis of oxygen and nitrogen by the denitrifier method

Bell

Sickman

2014

Rapid Commun. Mass Spectrom.

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“…Several methods using ion‐exchange resin have been established for ammonium and nitrate analysis in fresh‐water samples; however, high ion concentrations in soil extracts overload the ion‐exchange capacity and make this method unsuitable for soil extracts 12–14. The 'denitrifier method'15, 16 uses denitrifying bacteria that lack N 2 O reductase and therefore have N 2 O as metabolic end product, which is subsequently analyzed by purge‐and‐trap isotope ratio mass spectrometry (PTIRMS, Fig. 1).…”

mentioning

confidence: 99%

Vaulted trans‐Bis(salicylaldiminato)platinum(II) Crystals: Heat‐Resistant, Chromatically Sensitive Platforms for Solid‐State Phosphorescence at Ambient Temperature

Komiya

Okada

Fukumoto

et al. 2013

Chemistry A European J

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The synthesis, structure, and solid-state emission of vaulted trans-bis(salicylaldiminato)platinum(II) complexes are described. A series of polymethylene (1: n=8; 2: n=9; 3: n=10; 4: n=11; 5: n=12; 6: n=13) and polyoxyethylene (7: m=2; 8: m=3; 9: m=4) vaulted complexes (R=H (a), 3-MeO (b), 4-MeO (c), 5-MeO (d), 6-MeO (e), 4-CF3O (f), 5-CF3O (g)) was prepared by treating [PtCl2(CH3CN)2] with the corresponding N,N'-bis(salicylidene)-1,ω-alkanediamines. The trans coordination, vaulted structures, and the crystal packing of 1-9 have been unequivocally established from X-ray diffraction studies. Unpredictable, structure-dependent phosphorescent emission has been observed for crystals of the complexes under UV excitation at ambient temperature, whereas these complexes are entirely nonemissive in the solution state under the same conditions. The long-linked complex crystals 4-6, 8, and 9 exhibit intense emission (Φ77K =0.22-0.88) at 77 K, whereas short-linked complexes 1-3 and 7 are non- or slightly emissive at the same temperature (Φ77K <0.01-0.18). At 298 K, some of the long-linked crystals, 4a, 4b, 5c, 5e, 6c, 6e, and 9b, completely lose their high-emission properties with elevation of the temperature (Φ298K <0.01-0.02), whereas the other long-linked crystals, 5a, 6a, 9a, and 9d, exhibit high heat resistance towards emission decay with increasing temperature (Φ298K =0.21-0.38). Chromogenic control of solid-state emission over the range of 98 nm can be performed simply by introducing MeO groups at different positions on the aromatic rings. Orange, yellow-green, red, and yellow emissions are observed in the glass and crystalline state upon 3-, 4-, 5-, and 6-MeO substitution, respectively, whereas those with CF3 O substituents have orange emission, irrespective of the substitution position. DFT calculations (B3LYP/6-31G*, LanL2DZ) showed that such chromatic variation is ascribed to the position-specific influence of the substituents on the highest-occupied molecular orbital (HOMO) and lowest-unoccupied molecular orbital (LUMO) levels of the trans-bis(salicylaldiminato)platinum(II) platform. The solid-state emission and its heat resistance have been discussed on the basis of X-ray diffraction studies. The planarity of the trans-coordination sites is strongly correlated to the solid-state emission intensities of crystals 1-9 at lower temperatures. The specific heat-resistance properties shown exclusively by the 5a, 6a, 9a, and 9d crystals are due to their strong three-dimensional hydrogen-bonding interactions and/or Pt···Pt contacts, whereas heat-quenchable crystals 4a, 4b, 5c, 5e, 6c, 6e, and 9b are poorly bound with limited interactions, such as non-, one-, or two-dimensional hydrogen-bonding networks. These results lead to the conclusion that Pt···Pt contacts are an important factor in the heat resistance of solid-state phosphorescence at ambient temperature, although the role of Pt···Pt contacts can be substituted by only higher-ordered hydrogen-bonding fixation.

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“…Nitrifiers in soil can be stimulated to release N 2 O at low O 2 availability (∼5% air sat. ; Bollmann and Conrad, 1998), soil moisture content of up to ∼60% WFPS (Bateman and Baggs, 2005) and low pH (Mørkved et al, 2007). Denitrifying microorganisms can be stimulated to release N 2 O by sudden onset of anoxia (Morley et al, 2008), high concentrations of

{NO}_{3}^{-}

(Blackmer and Bremner, 1978; Blicher-Mathiesen and Hoffmann, 1999), and low pH (Simek and Cooper, 2002).…”

Section: Introductionmentioning

confidence: 99%

Extreme Emission of N2O from Tropical Wetland Soil (Pantanal, South America)

Liengaard¹,

Nielsen²,

Revsbech³

et al. 2013

Front. Microbio.

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Nitrous oxide (N2O) is an important greenhouse gas and ozone depleter, but the global budget of N2O remains unbalanced. Currently, ∼25% of the global N2O emission is ascribed to uncultivated tropical soils, but the exact locations and controlling mechanisms are not clear. Here we present the first study of soil N2O emission from the Pantanal indicating that this South American wetland may be a significant natural source of N2O. At three sites, we repeatedly measured in situ fluxes of N2O and sampled porewater nitrate MathClass-open(NO3-MathClass-close) during the low water season in 2008 and 2009. In 2010, 10 sites were screened for in situ fluxes of N2O and soil NO3- content. The in situ fluxes of N2O were comparable to fluxes from heavily fertilized forests or agricultural soils. An important parameter affecting N2O emission rate was precipitation, inducing peak emissions of >3 mmol N2O m−2 day−1, while the mean daily flux was 0.43 ± 0.03 mmol N2O m−2 day−1. Over 170 days of the drained period, we estimated non-wetted drained soil to contribute 70.0 mmol N2O m−2, while rain-induced peak events contributed 9.2 mmol N2O m−2, resulting in a total N2O emission of 79.2 mmol N2O m−2. At the sites of repeated sampling, the pool of porewater nitrate varied MathClass-open(0.002-7.1μmolNO3-gdW-1MathClass-close) with higher concentrations of NO3- (p < 0.05) found in drained soil than in water-logged soil, indicating dynamic shifts between nitrification and denitrification. In the field, O2 penetrated the upper 60 cm of drained soil, but was depleted in response to precipitation. Upon experimental wetting the soil showed rapid O2 depletion followed by N2O accumulation and a peak emission of N2O MathClass-open(2.5 - 3.0mmolN2Om-2day-1MathClass-close). Assuming that the observed emission of N2O from these wetland soils is generally representative to the Pantanal, we suggest that this undisturbed tropical wetland potentially contributes ∼1.7% to the global N2O emission budget, a significant single source of N2O.

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Simplified preparation for the δ15N-analysis in soil NO3- by the denitrifier method

Cited by 14 publications

References 23 publications

Correcting for background nitrate contamination in KCl-extracted samples during isotopic analysis of oxygen and nitrogen by the denitrifier method

Correcting for background nitrate contamination in KCl-extracted samples during isotopic analysis of oxygen and nitrogen by the denitrifier method

Vaulted trans‐Bis(salicylaldiminato)platinum(II) Crystals: Heat‐Resistant, Chromatically Sensitive Platforms for Solid‐State Phosphorescence at Ambient Temperature

Extreme Emission of N2O from Tropical Wetland Soil (Pantanal, South America)

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