scholarly journals Anaerobic methane oxidation by nitrate: kinetic isotope effect

2018 ◽  
Vol 10 (1) ◽  
Author(s):  
Vasiliy A. Vavilin
Keyword(s):  
Dynamic Model ◽  
Carbon Isotope ◽  
Carbon Isotopes ◽  
Isotope Effect ◽  
Isotope Fractionation ◽  
Kinetic Isotope Effect ◽  
Stable Carbon Isotopes ◽  
Stable Carbon ◽  
Fractionation Factor ◽  
Kinetic Isotope

The ratio of stable carbon isotopes (13C/12C) in different environments serves as a significant limitation in estimating the global balance of methane [Hornibrook et al., 2000]. In this case, the value of 13C/12C largely depends on the kinetic isotope effect associated with the metabolism of microorganisms that produce and consume CH4. The article suggests a dynamic model of the processes of methane formation and its anaerobic oxidation with nitrate by methanotrophic denitrifying microorganisms (DAOM), which allowed estimating the fractionation factor of stable carbon isotopes. In the experiment with peat from the minerotrophic bog [Smemo, Yavitt, 2007], the dynamics of the amount of methane and was measured. The dynamic model showed that the introduction of nitrate leads to a slow decrease in the partial pressure of methane. Since methane in the DAOM process is a substrate, methane is enriched with heavier carbon 13C in the system under study. This leads to an increase in the value . The carbon isotope fractionation factor during methane oxidation with nitrate was equal to 1.018 and comparable with the fraction of carbon isotope fractionation in the process of acetoclastic methanogenesis (1.01). Model calculations have shown that during incubation the apparent fractionation factor of carbon isotopes with the simultaneous formation of methane and DAOM slowly decreases. The ratio of 13C/12C isotopes in dissolved and gaseous methane practically does not differ. The model showed that an increase in the initial concentration of nitrate increases the rate of DAOM, which leads to a decrease in the concentration of dissolved methane. In this case, the value of 13C/12C increases. In field studies, Shi et al. (2017) showed that the presence of DAOM in peat bogs in which fertilizers penetrate can be controlled by the amount of nitrate used and the depth of penetration into the anoxic layer. Two MATLAB files describing DAOM are attached to the article.

scholarly journals Evidence of Substantial Carbon Isotope Fractionation among Substrate, Inorganic Carbon, and Biomass during Aerobic Mineralization of 1,2-Dichloroethane byXanthobacter autotrophicus

2000 ◽  
Vol 66 (11) ◽  
pp. 4870-4876 ◽  
Author(s):  
D. Hunkeler ◽  
R. Aravena
Keyword(s):  
Carbon Isotope ◽  
Isotope Effect ◽  
Isotope Fractionation ◽  
Kinetic Isotope Effect ◽  
Inorganic Carbon ◽  
Mechanistic Model ◽  
Fractionation Factor ◽  
Carbon Isotope Fractionation ◽  
Kinetic Isotope ◽  
Factor Α

ABSTRACT Carbon isotope fractionation during aerobic mineralization of 1,2-dichloroethane (1,2-DCA) by Xanthobacter autotrophicusGJ10 was investigated. A strong enrichment of 13C in residual 1,2-DCA was observed, with a mean fractionation factor α ± standard deviation of 0.968 ± 0.0013 to 0.973 ± 0.0015. In addition, a large carbon isotope fractionation between biomass and inorganic carbon occurred. A mechanistic model that links the fractionation factor α to the rate constants of the first catabolic enzyme was developed. Based on the model, it was concluded that the strong enrichment of 13C in 1,2-DCA arises because the first irreversible step of the initial enzymatic transformation of 1,2-DCA consists of an SN2 nucleophilic substitution. SN2 reactions are accompanied by a large kinetic isotope effect. The substantial carbon isotope fractionation between biomass and inorganic carbon could be explained by the kinetic isotope effect associated with the initial 1,2-DCA transformation and by the metabolic pathway of 1,2-DCA degradation. Carbon isotope fractionation during 1,2-DCA mineralization leads to 1,2-DCA, inorganic carbon, and biomass with characteristic carbon isotope compositions, which may be used to trace the process in contaminated environments.

Fundamental studies on kinetic isotope effect (KIE) of hydrogen isotope fractionation in natural gas systems

2011 ◽  
Vol 75 (10) ◽  
pp. 2696-2707 ◽  
Author(s):  
Yunyan Ni ◽  
Qisheng Ma ◽  
Geoffrey S. Ellis ◽  
Jinxing Dai ◽  
Barry Katz ◽  
...  
Keyword(s):  
Natural Gas ◽  
Isotope Effect ◽  
Hydrogen Isotope ◽  
Isotope Fractionation ◽  
Kinetic Isotope Effect ◽  
Kinetic Isotope

Vertical stratification of Neotropical leaf-nosed bats (Chiroptera: Phyllostomidae) revealed by stable carbon isotopes

2011 ◽  
Vol 27 (03) ◽  
pp. 211-222 ◽  
Author(s):  
Katja Rex ◽  
Robert Michener ◽  
Thomas H. Kunz ◽  
Christian C. Voigt
Keyword(s):  
Carbon Isotope ◽  
Carbon Isotopes ◽  
Species Interactions ◽  
Rain Forest ◽  
Stable Carbon Isotopes ◽  
Stable Carbon Isotope ◽  
The Body ◽  
Vertical Stratification ◽  
Forest Site ◽  
Stable Carbon

Abstract:Tropical rain forests harbour the most diverse plant and animal assemblages known to science, but our understanding of assemblage structure and species interactions is limited. Bats, as the only flying mammals, have the potential to exploit resources from all strata in forest communities. Thus, fruit-eating phyllostomid bats often have been categorized into canopy-, subcanopy- and understorey-foraging species, based largely upon the height at which they were most frequently captured. Here we challenge this classification and use stable carbon isotopes to assess foraging height of bat species at an Amazonian rain-forest site in Ecuador and at a Caribbean lowland rain-forest site in Costa Rica for comparison with data from mist-net captures. The proportion of the heavy stable carbon isotope13C in relation to the lighter12C isotope increases in plants from ground level to the canopy (0.12‰ m−1–0.18‰ m−1), and these differences in stable carbon isotope signatures are reflected in the body tissue of phytophagous bats. We used the stable carbon isotope ratio (δ13C) of wing tissue to estimate the foraging heights of 54 phyllostomid species in two Neotropical bat assemblages. Based on stable isotope data, phyllostomid species exploit food resources at all vertical strata of the forest. Capture height was not a reliable predictor of foraging height and suggests that bats most likely use lower strata to commute between foraging sites to avoid predators. Vertical stratification is likely to be a key factor promoting niche partitioning, thus promoting high local species richness in many tropical animal assemblages.

scholarly journals Degradation changes stable carbon isotope depth profiles in palsa peatlands

2014 ◽  
Vol 11 (1) ◽  
pp. 1383-1412 ◽  
Author(s):  
J. P. Krüger ◽  
J. Leifeld ◽  
C. Alewell
Keyword(s):  
Carbon Isotope ◽  
Carbon Isotopes ◽  
Stable Carbon Isotopes ◽  
Stable Carbon Isotope ◽  
Stable Carbon ◽  
Δ13c Values ◽  
Depth Profiles ◽  
Degradation Rates ◽  
Aerobic Decomposition ◽  
Permafrost Thawing

Abstract. Palsa peatlands are a significant carbon pool in the global carbon cycle and are projected to change by global warming due to accelerated permafrost thaw. Our aim was to use stable carbon isotopes as indicators of palsa degradation. Depth profiles of stable carbon isotopes generally reflect organic matter dynamics in soils with an increase of δ13C values during aerobic decomposition and stable or decreasing δ13C values with depth during anaerobic decomposition. Stable carbon isotope depth profiles of undisturbed and degraded sites of hummocks as well as hollows at three palsa peatlands in northern Sweden were used to investigate the degradation processes. The depth patterns of stable isotopes clearly differ between intact and degraded hummocks at all sites. Erosion and cryoturbation at the degraded sites significantly changes the stable carbon isotope depth profiles. At the intact hummocks the uplifting of peat material by permafrost is indicated by a turning in the δ13C depth trend and this assessment is supported by a change in the C / N ratios. For hollows isotope patterns were less clear, but some hollows and degraded hollows in the palsa peatlands show differences in their stable carbon isotope depth profiles indicating enhanced degradation rates. We conclude that the degradation of palsa peatlands by accelerated permafrost thawing could be identified with stable carbon isotope depth profiles. At intact hummocks δ13C depth patterns display the uplifting of peat material by a change in peat decomposition processes.

scholarly journals Evidence for a major missing source in the global chloromethane budget from stable carbon isotopes

2018 ◽  
Author(s):  
Enno Bahlmann ◽  
Frank Keppler ◽  
Julian Wittmer ◽  
Markus Greule ◽  
Heinz Friedrich Schöler ◽  
...  
Keyword(s):  
Carbon Isotope ◽  
Carbon Isotopes ◽  
Stable Carbon Isotopes ◽  
Tropical Rainforest ◽  
Isotope Effects ◽  
Stratospheric Ozone ◽  
Mixing Ratios ◽  
Promising Tool ◽  
Kinetic Isotope ◽  
Phase Out

Abstract. Chloromethane (CH3Cl) is the most important natural input of reactive chlorine to the stratosphere, contributing about 16 % to stratospheric ozone depletion. Due to the phase out of anthropogenic emissions of chlorofluorocarbons, CH3Cl will largely control future levels of stratospheric chlorine. The tropical rainforest is commonly assumed to be the strongest single CH3Cl source, contributing over half of the global annual emissions of about 4000 to 5000 Gg (1 Gg = 109 g). This source shows a characteristic carbon isotope fingerprint, making isotopic investigations a promising tool for improving its atmospheric budget. Applying carbon isotopes to better constrain the atmospheric budget of CH3Cl requires sound information on the kinetic isotope effects for the main sink processes e.g. the reaction with OH and Cl in the troposphere. We conducted photochemical CH3Cl degradation experiments in a 3500 L smog chamber to determine the carbon isotope fractionation (ε) for the reaction of CH3Cl with OH and Cl. For the reaction of CH3Cl with OH, we determined a ε of (−11.2 ± 0.8) ‰ (n = 3) and for the reaction with Cl we found a ε of (−10.2 ± 0.5) ‰ (n = 1) being five to six times smaller than previously reported. Our smaller isotope effects are strongly supported by the lack of any significant seasonal covariation in previously reported tropospheric δ13C(CH3Cl) values with the OH driven seasonal cycle in tropospheric mixing ratios. Applying these new fractionation factors to the global CH3Cl budget using a simple two hemispheric box model, we derive a tropical rainforest CH3Cl source of (670 ± 200) Gg a−1, which is considerably smaller than previous estimates. A revision of previous bottom up estimates, using above ground biomass instead of rainforest area, strongly supports this lower estimate. Finally, our results suggest a large unknown tropical CH3Cl source of (1230 ± 200) Gg a−1.

Seedling growth, leaf water status and signature of stable carbon isotopes in C3 perennials exposed to natural phytochemicals

2012 ◽  
Vol 60 (8) ◽  
pp. 676 ◽  
Author(s):  
M. Iftikhar Hussain ◽  
Manuel J. Reigosa
Keyword(s):  
Water Use Efficiency ◽  
Carbon Isotope ◽  
Carbon Isotopes ◽  
Water Use ◽  
Stable Carbon Isotopes ◽  
Carbon Isotope Discrimination ◽  
Water Status ◽  
Perennial Species ◽  
Stable Carbon ◽  
Use Efficiency

In the present study, we evaluated the seedling growth, water status and signature of stable carbon isotopes in C3 perennial species exposed to natural phytochemicals. Three perennial species, cocksfoot (Dactylis glomerata), perennial ryegrass (Lolium perenne) and common sorrel (Rumex acetosa), were grown for 30 days in perlite, watered with Hoagland solution and exposed to the phytochemicals benzoxazolin-2(3H)-one (BOA) and cinnamic acid (CA) at 0, 0.1, 0.5, 1.0 and 1.5 mM concentrations. BOA markedly decreased the leaf and root fresh weights of D. glomerata and L. perenne in a concentration-dependent manner. The leaf fresh weight (LFW) of plants treated with CA (1.5 mM) was similarly affected by showing a decrease of LFW, being the lowest in L. perenne (56%) followed by D. glomerata (46%). The relative water contents of L. perenne, D. glomerata and R. acetosa were decreased while maximum RWC reduction was observed in L. perenne. Carbon isotope discrimination in L. perenne, D. glomerata and R. acetosa were reduced following treatment with BOA and CA at 1.5 mM. BOA at 1.5 mM decreased the ratio of intercellular to ambient CO2 concentration relative to control in L. perenne, D. glomerata and R. acetosa. There was an increase in water-use efficiency in L. perenne, D. glomerata and R. acetosa after treatment with BOA and CA. The dry weight of plants treated with CA (1.5 mM) showed different patterns of variation, being lowest in L. perenne (33%) followed by D. glomerata (3%) and R. acetosa (2%). Phytotoxicity was higher for the perennial grass than for the perennial broadleaf. These results clearly demonstrate a widespread occurrence of phytotoxicity among the three species, their tolerance and relationship between carbon isotope discrimination and intrinsic water-use efficiency.

Untersuchungen zur Reaktion der Alkoholdehydrogenase mit Tritium -markierten Substraten

1966 ◽  
Vol 21 (6) ◽  
pp. 547-551 ◽  
Author(s):  
Dieter Palm
Keyword(s):  
Alcohol Dehydrogenase ◽  
Isotope Effect ◽  
Isotope Fractionation ◽  
Kinetic Isotope Effect ◽  
Retention Volume ◽  
Deae Cellulose ◽  
Yeast Alcohol Dehydrogenase ◽  
Kinetic Isotope ◽  
Direct Indication ◽  
Rate Controlling Step

The temperature dependence of the kinetic isotope effect of NADH-T in the acetaldehyde reduction by yeast alcohol dehydrogenase showed a discontinuity which can be explained by a change of the rate controlling step. The magnitude of the isotope effect is largely dependent on the nature of the unlabelled aldehyde and increases in the order acetaldehyde, propionaldehyde, butyraldehyde. This is a direct indication that the second substrate influences the nature of the H-transfer from NADH. During substrate binding the aldehyde causes an effect on the transferable H of NADH. This effect is less pronounced for the less effective substrates propionaldehyde and butyraldehyde. Comparing the homologue aldehydes the small size of the isotope effect gives an indication that acetaldehyde is the natural substrate of yeast alcohol dehydrogenase.The purification of NADH-T on DEAE-Cellulose is connected with isotope fractionation which amounts to 0.4 — 1.1% of retention volume.

scholarly journals Stable carbon isotopes as indicators for environmental change in palsa peats

2011 ◽  
Vol 8 (7) ◽  
pp. 1769-1778 ◽  
Author(s):  
C. Alewell ◽  
R. Giesler ◽  
J. Klaminder ◽  
J. Leifeld ◽  
M. Rollog
Keyword(s):  
Environmental Change ◽  
Carbon Isotope ◽  
Carbon Isotopes ◽  
Climate Warming ◽  
Anaerobic Degradation ◽  
Stable Carbon Isotopes ◽  
Stable Carbon Isotope ◽  
Stable Carbon ◽  
Depth Profiles ◽  
Water Saturated

Abstract. Palsa peats are unique northern ecosystems formed under an arctic climate and characterized by a high biodiversity and sensitive ecology. The stability of the palsas are seriously threatened by climate warming which will change the permafrost dynamic and induce a degradation of the mires. We used stable carbon isotope depth profiles in two palsa mires of Northern Sweden to track environmental change during the formation of the mires. Soils dominated by aerobic degradation can be expected to have a clear increase of carbon isotopes (δ13C) with depth, due to preferential release of 12C during aerobic mineralization. In soils with suppressed degradation due to anoxic conditions, stable carbon isotope depth profiles are either more or less uniform indicating no or very low degradation or depth profiles turn to lighter values due to an enrichment of recalcitrant organic substances during anaerobic mineralisation which are depleted in 13C. The isotope depth profile of the peat in the water saturated depressions (hollows) at the yet undisturbed mire Storflaket indicated very low to no degradation but increased rates of anaerobic degradation at the Stordalen site. The latter might be induced by degradation of the permafrost cores in the uplifted areas (hummocks) and subsequent breaking and submerging of the hummock peat into the hollows due to climate warming. Carbon isotope depth profiles of hummocks indicated a turn from aerobic mineralisation to anaerobic degradation at a peat depth between 4 and 25 cm. The age of these turning points was 14C dated between 150 and 670 yr and could thus not be caused by anthropogenically induced climate change. We found the uplifting of the hummocks due to permafrost heave the most likely explanation for our findings. We thus concluded that differences in carbon isotope profiles of the hollows might point to the disturbance of the mires due to climate warming or due to differences in hydrology. The characteristic profiles of the hummocks are indicators for micro-geomorphic change during permafrost up heaving.

Nitrogen- and carbon-isotope fractionation between mothers and offspring in red-backed voles (Clethrionomys gapperi)

2005 ◽  
Vol 83 (5) ◽  
pp. 712-716 ◽  
Author(s):  
David T.J Sare ◽  
John S Millar ◽  
Frederick J Longstaffe
Keyword(s):  
Carbon Isotope ◽  
Small Mammals ◽  
Isotope Fractionation ◽  
Stable Carbon Isotopes ◽  
Mammary Glands ◽  
Trophic Relationships ◽  
Clethrionomys Gapperi ◽  
Stable Carbon ◽  
Isotopic Enrichment ◽  
In The Wild

Small mammals are income breeders, but the degree to which females draw from maternal reserves and partition nutrients to the mammary glands in the wild is not known. This study examined stable-nitrogen and stable-carbon isotopes in red-backed vole, Clethrionomys gapperi (Vigors, 1830), hair to determine mother–offspring trophic relationships and to consider the extent to which voles rely on maternal reserves during lactation. Both dependent and independent young showed isotopic enrichment in 15N and depletion of 13C in their hair relative to mothers. We suggest that growing offspring, both dependent and independent, may catabolize body reserves to support both growth and moult. We propose that the nitrogen- and carbon-isotope compositions of hair may be more useful indicators of metabolic rate than mother–offspring trophic relationships in small mammals.

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