Nitrogen isotope ratios trace high-pH conditions in a terrestrial Mars analog site

High-pH alkaline lakes are among the most productive ecosystems on Earth and prime targets in the search for life on Mars; however, a robust proxy for such settings does not yet exist. Nitrogen isotope fractionation resulting from NH3 volatilization at high pH has the potential to fill this gap. To validate this idea, we analyzed samples from the Nördlinger Ries, a Miocene impact crater lake that displayed pH values up to 9.8 as inferred from mineralogy and aqueous modeling. Our data show a peak in δ15N of +17‰ in the most alkaline facies, followed by a gradual decline to around +5‰, concurrent with the proposed decline in pH, highlighting the utility of nitrogen isotopes as a proxy for high-pH conditions. In combination with independent mineralogical indicators for high alkalinity, nitrogen isotopes can provide much-needed quantitative constraints on ancient atmospheric Pco2 (partial pressure of CO2) and thus climatic controls on early Earth and Mars.

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Hydrothermal crystallization kinetics of m-ZrO2 and t-ZrO2

Journal of Materials Research ◽

10.1557/jmr.1990.2698 ◽

1990 ◽

Vol 5 (11) ◽

pp. 2698-2705 ◽

Cited By ~ 100

Author(s):

Raymond P. Denkewicz ◽

Kevor S. TenHuisen ◽

James H. Adair

Keyword(s):

Crystallization Kinetics ◽

Low Ph ◽

Formation Mechanisms ◽

Gel Structure ◽

Hydrothermal Conditions ◽

High Ph ◽

Ph Values ◽

Ph Conditions ◽

Apparent Activation Energies ◽

Kinetics Of

The isothermal nucleation and crystallization kinetics of hydrothermally prepared monoclinic and tetragonal ZrO2 have been determined at various pH conditions. It is shown that monoclinic ZrO2 precipitates at low pH whereas at high pH tetragonal ZrO2 crystallizes from an amorphous zirconium (hydrous) oxide, Zr(OH)xOy, precursor. At intermediate pH conditions mixtures of the polymorphs are formed suggestive of kinetically competing particle formation mechanisms. The data are explained by the proposed existence of three controlling regimes for the formation of crystalline ZrO2: dissolution/precipitation at low pH, a solubility controlled regime at intermediate pH values, and a gel structure controlled regime at high pH. Apparent activation energies for the nucleation and crystallization of monoclinic and tetragonal ZrO2 formed under hydrothermal conditions are presented.

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Mossbauer spectroscopic evidence of a IVFe3+ intermediate in the oxidation of Fe(Oh)2 to α-FeOOH

Soil Research ◽

10.1071/sr9910399 ◽

1991 ◽

Vol 29 (3) ◽

pp. 399 ◽

Cited By ~ 1

Author(s):

CM Cardile ◽

DG Lewis

Keyword(s):

Alkaline Solution ◽

Building Blocks ◽

Spectral Parameters ◽

Initial Oxidation ◽

Spectroscopic Evidence ◽

High Ph ◽

Ph Values ◽

Fe Species ◽

Ph Conditions ◽

Surrounding Liquid

Mossbauer spectroscopy was used to study the oxidation of Fe(OH)2 under high pH conditions with the aim of detecting the formation of Fe(OH)3. The Mossbauer spectral parameters indicated that a small IVFe3+ component was initially present in the Fe(OH)2. The Mossbauer spectra were recorded at 77 K, thus any Fe species in solution would also be observed in the frozen state. The small IVFe3+ component increased progressively with the oxidation of the Fe(OH)2, maximizing with the onset of �-FeOOH formation. As �-FeOOH formation increased, the IVFe3+ component decreased, with �-FeOOH being the final sole phase. It is suggested that the Mossbauer spectral parameters indicate that a component such as Fe(OH)2 may form at high pH values as used in this study. Furthermore, any Fe3+ produced by the initial oxidation of Fe(OH)2 is exsolved from the solid and at the high pH of the surrounding liquid produces Fe(OH)-4 until the formation of the more stable �-FeOOH begins. This suggests Fe(OH)2 could be the building blocks for �-FeOOH in alkaline solution. No apparent Fe(OH)3 phase was observed as anticipated.

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Nitrogen Isotope Ratios Trace High pH in a Terrestrial Mars Analog Site

10.46427/gold2020.2604 ◽

2020 ◽

Author(s):

Christopher Tino ◽

Eva Stüeken ◽

Gernot Arp ◽

Dietmar Jung ◽

Timothy W. Lyons

Keyword(s):

Nitrogen Isotope ◽

Isotope Ratios ◽

High Ph ◽

Mars Analog

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Impact of climate and bulking materials on characteristics of compost from ecological toilets

Journal of Water Sanitation and Hygiene for Development ◽

10.2166/washdev.2012.059 ◽

2012 ◽

Vol 2 (2) ◽

pp. 79-86 ◽

Cited By ~ 3

Author(s):

James W. McKinley ◽

Rebecca E. Parzen ◽

Álvaro Mercado Guzmán

Keyword(s):

Low Carbon ◽

Pathogen Inactivation ◽

High Ph ◽

Moisture Contents ◽

Urine Diversion ◽

Ph Values ◽

Dominant Process ◽

Nitrogen Ratio ◽

Storage Times ◽

Carbon Concentrations

Urine-diversion dehydration toilets (UDDT) are common throughout the developing world, and the toilet product is widely used as compost. There is no comprehensive research to date that characterizes the compost to determine its quality, extent of pathogen inactivation, and the effects of climate and bulking materials on the compost. Compost was collected from 45 UDDT in Bolivia and analyzed for physical, chemical, and biological parameters. Eighty percent and 56% of samples did not meet acceptable compost guidelines for moisture content and pH, respectively, indicating desiccation was the dominant process in UDDT. Bulking materials significantly impacted compost characteristics in terms of pH, carbon, carbon-to-nitrogen ratio, and carbon stability (P < 0.05). Composts with ash exhibited, on average, low carbon concentrations (4.9%) and high pH values (9.7), which can be harmful to plants and composting microorganisms. Composts with sawdust exhibited, on average, high carbon concentrations (40.0%) and carbon-to-nitrogen ratios (31.0). Climate had no significant impact on chemical characteristics, however composts from humid regions had significantly higher moisture contents (34.4%) than those from arid climates (24.8%) (P < 0.05). Viable Ascaris lumbricoides ova were identified in 31% of samples, including samples with high pH, low moisture contents, and long storage times.

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Nitrogen isotope fractionation during the reduction of NO3− to NH4+ by Desulfovibrio sp.

Canadian Journal of Microbiology ◽

10.1139/m83-038 ◽

1983 ◽

Vol 29 (2) ◽

pp. 231-234 ◽

Cited By ~ 24

Author(s):

R. G. L. McCready ◽

W. D. Gould ◽

R. W. Barendregt

Keyword(s):

Isotope Fractionation ◽

Nitrogen Isotope ◽

Initial Sample ◽

Minimum Value ◽

Nitrogen Isotope Fractionation ◽

Reductive Process

Desulfovibrio reduce NO3−to NH4+ via a dissimilatory pathway. In 21 days, four strains of Desulfovibrio reduced 36–48% of the available NO3− to ammonium. During this reductive process extensive nitrogen isotope fractionation occurred: the product NH4+ was enriched in 15N in the initial sample, then became enriched in 14N to a minimum value at approximately 20–25% reaction, and then became isotopically heavier as the reaction proceeded.

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Mechanism for nitrogen isotope fractionation during ammonium assimilation by Escherichia coli K12

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1216683110 ◽

2013 ◽

Vol 110 (21) ◽

pp. 8696-8701 ◽

Cited By ~ 21

Author(s):

J. Vo ◽

W. Inwood ◽

J. M. Hayes ◽

S. Kustu

Keyword(s):

Escherichia Coli ◽

Isotope Fractionation ◽

Nitrogen Isotope ◽

Ammonium Assimilation ◽

Escherichia Coli K12 ◽

Nitrogen Isotope Fractionation

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Expression patterns of two carbonic anhydrase genes, Na+/K+-ATPase and V-type H+-ATPase, in the freshwater crayfish, Cherax quadricarinatus, exposed to low pH and high pH

Australian Journal of Zoology ◽

10.1071/zo16048 ◽

2017 ◽

Vol 65 (1) ◽

pp. 50 ◽

Cited By ~ 3

Author(s):

Muhammad Yousuf Ali ◽

Ana Pavasovic ◽

Peter B. Mather ◽

Peter J. Prentis

Keyword(s):

Carbonic Anhydrase ◽

Expression Patterns ◽

Maximum Level ◽

Low Ph ◽

Freshwater Crayfish ◽

Α Subunit ◽

Cherax Quadricarinatus ◽

High Ph ◽

Internal Ph ◽

Ph Conditions

Carbonic anhydrase (CA), Na+/K+-ATPase (NKA) and Vacuolar-type H+-ATPase (HAT) play vital roles in osmoregulation and pH balance in decapod crustaceans. As variable pH levels have a significant impact on the physiology of crustaceans, it is crucial to understand the mechanisms by which an animal maintains its internal pH. We examined expression patterns of cytoplasmic (CAc) and membrane-associated form (CAg) of CA, NKA α subunit and HAT subunit a in gills of freshwater crayfish, Cherax quadricarinatus, at three pH levels – 6.2, 7.2 (control) and 8.2 – over 24 h. Expression levels of CAc were significantly increased at low pH and decreased at high pH conditions 24 h after transfer. Expression increased at low pH after 12 h, and reached its maximum level by 24 h. CAg showed a significant increase in expression at 6 h after transfer at low pH. Expression of NKA significantly increased at 6 h after transfer to pH 6.2 and remained elevated for up to 24 h. Expression for HAT and NKA showed similar patterns, where expression significantly increased 6 h after transfer to low pH and remained significantly elevated throughout the experiment. Overall, CAc, CAg, NKA and HAT gene expression is induced at low pH conditions in freshwater crayfish.

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