scholarly journals Long-term drying of Mars by sequestration of ocean-scale volumes of water in the crust

Science ◽  
2021 ◽  
Vol 372 (6537) ◽  
pp. 56-62 ◽  
Author(s):  
E. L. Scheller ◽  
B. L. Ehlmann ◽  
Renyu Hu ◽  
D. J. Adams ◽  
Y. L. Yung
Keyword(s):  
Isotope Ratio ◽  
Chemical Weathering ◽  
Loss Rate ◽  
Hydrological Cycle ◽  
Observational Constraints ◽  
Geological Evidence ◽  
Atmospheric Escape ◽  
Water Volumes ◽  
Hydrogen Isotope Ratio

Geological evidence shows that ancient Mars had large volumes of liquid water. Models of past hydrogen escape to space, calibrated with observations of the current escape rate, cannot explain the present-day deuterium-to-hydrogen isotope ratio (D/H). We simulated volcanic degassing, atmospheric escape, and crustal hydration on Mars, incorporating observational constraints from spacecraft, rovers, and meteorites. We found that ancient water volumes equivalent to a 100 to 1500 meter global layer are simultaneously compatible with the geological evidence, loss rate estimates, and D/H measurements. In our model, the volume of water participating in the hydrological cycle decreased by 40 to 95% over the Noachian period (~3.7 billion to 4.1 billion years ago), reaching present-day values by ~3.0 billion years ago. Between 30 and 99% of martian water was sequestered through crustal hydration, demonstrating that irreversible chemical weathering can increase the aridity of terrestrial planets.

Authenticity of sugar – Identification of plant source and determination of geographical origin of sucrose

2015 ◽  
pp. 40-43 ◽  
Author(s):  
Andreas G. Degenhardt
Keyword(s):  
Metabolic Pathways ◽  
Isotope Ratio ◽  
Geographical Origin ◽  
Hydrological Cycle ◽  
Isotope Ratios ◽  
Saccharum Officinarum ◽  
Mass Spectrometric ◽  
C3 And C4 Plants ◽  
Plant Source

The isotope ratios of water, organic matter and micronutrients from food are dependent on the circumstances and sites of their origin and production. Analytical methods, based on mass spectrometry, are established for routine determination of isotopes. Differentiation between metabolic pathways of C3 and C4 plants is realizable by determination 13C/12C ratios which can distinguish and identify sucrose from pure beet (Beta vulgaris) and pure cane (Saccharum officinarum). Influenced by the worldwide hydrological cycle the isotope ratios of 2H/1H and 18O/16O vary systematically, the variations give information about geographical origin. The exemplarily determination of authenticity is demonstrated by using mass spectrometric isotope ratio evaluation for identification of plant source and geographical origin with the help of selected sugar samples with known origin.

scholarly journals Tooth loss in complying and non-complying periodontitis patients with different periodontal risk levels during supportive periodontal care

2021 ◽  
Author(s):  
Roberto Farina ◽  
Anna Simonelli ◽  
Andrea Baraldi ◽  
Mattia Pramstraller ◽  
Luigi Minenna ◽  
...  
Keyword(s):  
Active Treatment ◽  
Clinical Relevance ◽  
Tooth Loss ◽  
Loss Rate ◽  
Risk Levels ◽  
Recall Interval ◽  
Level 3 ◽  
The Difference ◽  
Periodontal Risk

Abstract Objectives To evaluate yearly tooth loss rate (TLR) in periodontitis patients with different periodontal risk levels who had complied or not complied with supportive periodontal care (SPC). Materials and methods Data from 168 periodontitis patients enrolled in a SPC program based on a 3-month suggested recall interval for at least 3.5 years were analyzed. For patients with a mean recall interval within 2–4 months (“compliers”) or > 4 months (“non-compliers”) with different PerioRisk levels (Trombelli et al. 2009), TLR (irrespective of the cause for tooth loss) was calculated. TLR values were considered in relation to meaningful TLR benchmarks from the literature for periodontitis patients either under SPC (0.15 teeth/year; positive benchmark) or irregularly complying with SPC (0.36 teeth/year; negative benchmark). Results In both compliers and non-compliers, TLR was significantly below or similar to the positive benchmark in PerioRisk level 3 (0.08 and 0.03 teeth/year, respectively) and PerioRisk level 4 (0.12 and 0.18 teeth/year, respectively). Although marked and clinically relevant in non-compliers, the difference between TLR of compliers (0.32 teeth/year) and non-compliers (0.52 teeth/year) with PerioRisk level 5 and the negative benchmark was not significant. Conclusion A SPC protocol based on a 3- to 6-month recall interval may effectively limit long-term tooth loss in periodontitis patients with PerioRisk levels 3 and 4. A fully complied 3-month SPC protocol seems ineffective when applied to PerioRisk level 5 patients. Clinical relevance PerioRisk seems to represent a valid tool to inform the SPC recall interval as well as the intensity of active treatment prior to SPC enrollment.

scholarly journals A routing-benefited deployment approach combining static and dynamic layouts for underwater optical wireless networks

2021 ◽  
Vol 17 (2) ◽  
pp. 155014772199961
Author(s):  
Zhongwei Shen ◽  
Hongxi Yin ◽  
Yanjun Liang ◽  
Rigele Maao ◽  
Lianyou Jing
Keyword(s):  
Optical Communication ◽  
Loss Rate ◽  
Communication Model ◽  
Optical Wireless ◽  
Wireless Optical Communication ◽  
Area Of Interest ◽  
Virtual Force ◽  
The Impact ◽  
Term Monitoring

A routing-benefited deployment algorithm combining static and dynamic layouts is proposed, and its comprehensive performance evaluation is given in this article. The proposed routing-benefited deployment algorithm is intended to provide a suitable network deployment and subsequent data transmission approach for underwater optical networking and communication. Static nodes are anchored for long-term monitoring, and movable nodes can adjust their depths based on the virtual force and move with the variation of area-of-interest changing. Then, nodes begin to collect data that they can monitor and transmit to sink nodes. Here, the underwater wireless optical communication model is described to actualize the real environment, and the vector-based forwarding protocol is particularly considered to compare the impact of different deployment algorithms on routing. It is shown by simulation experiment results that routing-benefited deployment algorithm outperforms several existing traditional virtual force deployment algorithms in terms of coverage, lifetime, energy consumption balance, packet-loss rate, and time-delay.

scholarly journals Chemical weathering and long-term CO2consumption in the Ayeyarwady and Mekong river basins in the Himalayas

2015 ◽  
Vol 120 (6) ◽  
pp. 1165-1175 ◽  
Author(s):  
Takuya Manaka ◽  
Souya Otani ◽  
Akihiko Inamura ◽  
Atsushi Suzuki ◽  
Thura Aung ◽  
...  
Keyword(s):  
Chemical Weathering ◽  
River Basins ◽  
Mekong River

scholarly journals Hydro-Meteorological Trends in an Austrian Low-Mountain Catchment

Climate ◽  
2021 ◽  
Vol 9 (8) ◽  
pp. 122
Author(s):  
Gerald Krebs ◽  
David Camhy ◽  
Dirk Muschalla
Keyword(s):  
Hydrological Cycle ◽  
Potential Evapotranspiration ◽  
Remote Sensing Data ◽  
Kendall Test ◽  
Adaptation Measures ◽  
Mitigation And Adaptation ◽  
Regional Impacts ◽  
Long Term Trends ◽  
Annual Scale

While ongoing climate change is well documented, the impacts exhibit a substantial variability, both in direction and magnitude, visible even at regional and local scales. However, the knowledge of regional impacts is crucial for the design of mitigation and adaptation measures, particularly when changes in the hydrological cycle are concerned. In this paper, we present hydro-meteorological trends based on observations from a hydrological research basin in Eastern Austria between 1979 and 2019. The analyzed variables include air temperature, precipitation, and catchment runoff. Additionally, the number of wet days, trends for catchment evapotranspiration, and computed potential evapotranspiration were derived. Long-term trends were computed using a non-parametric Mann–Kendall test. The analysis shows that while mean annual temperatures were decreasing and annual temperature minima remained constant, annual maxima were rising. Long-term trends indicate a shift of precipitation to the summer, with minor variations observed for the remaining seasons and at an annual scale. Observed precipitation intensities mainly increased in spring and summer between 1979 and 2019. Catchment actual evapotranspiration, computed based on catchment precipitation and outflow, showed no significant trend for the observed time period, while potential evapotranspiration rates based on remote sensing data increased between 1981 and 2019.

Increase in soil stable carbon isotope ratio relates to loss of organic carbon: results from five long-term bare fallow experiments

Oecologia ◽  
2014 ◽  
Vol 177 (3) ◽  
pp. 811-821 ◽  
Author(s):  
Lorenzo Menichetti ◽  
Sabine Houot ◽  
Folkert van Oort ◽  
Thomas Kätterer ◽  
Bent T. Christensen ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Carbon Isotope ◽  
Isotope Ratio ◽  
Stable Carbon Isotope ◽  
Carbon Isotope Ratio ◽  
Stable Carbon ◽  
Stable Carbon Isotope Ratio ◽  
Bare Fallow

scholarly journals Climatic effects on rapid chemical and physical denudation rates measured with cosmogenic nuclides in the Ōhau catchment, New Zealand

2021 ◽  
Author(s):  
◽  
Maia Bellingham
Keyword(s):  
Carbon Dioxide ◽  
New Zealand ◽  
Chemical Weathering ◽  
Southern Alps ◽  
Grain Sizes ◽  
Denudation Rates ◽  
Climate Stability ◽  
Mountain Landscapes ◽  
Carbon Dioxide Cycling

<p>Understanding how active mountain landscapes contribute to carbon dioxide cycling and influences on long-term climate stability requires measurement of weathering fluxes from these landscapes. The few measured chemical weathering rates in the Southern Alps are an order of magnitude greater than in the rest of the world. Rapid tectonic uplift coupled with extreme orographic precipitation is driving exceptionally fast chemical and physical denudation. These rates suggest that weathering in landscapes such as the Southern Alps could play a significant role in carbon dioxide cycling. However, the relative importance of climate and tectonics driving these fast rates remains poorly understood.   To address this gap, in situ ¹⁰Be derived catchment-averaged denudation rates were measured in the Ōhau catchment, Canterbury, New Zealand. Denudation rates in the Dobson Valley within the Ōhau catchment, varied from 474 – 7,570 m Myr⁻¹, aside from one sub-catchment in the upper Dobson Valley that had a denudation rate of 12,142 m Myr⁻¹. The Dobson and Hopkins Rivers had denudation rates of 1,660 and 4,400 m Myr⁻¹ respectively, in these catchments. Dobson Valley denudation rates show a moderate correlation with mean annual precipitation (R²=0.459). This correlation supports a similar trend identified at local and regional scales, and at high rates of precipitation this may be an important driver of erosion and weathering.   Sampling of four grain sizes (0.125 to > 8 mm) at one site in the Dobson Valley resulted in variability in ¹⁰Be concentrations up to a factor of 2.5, which may be a result of each grain size recording different erosional processes. These observations demonstrate the importance of assessing potential variability and the need to sample consistent grain sizes across catchments.   Chemical depletion fractions measured within soil pits in the upper Dobson Valley indicate chemical weathering contributes 30% of total denudation, and that physical erosion is driving rapid total denudation. Chemical weathering appears to surpass any proposed weathering speed limit and suggests total weathering may not be limited by weathering kinetics. This research adds to the paucity of research in New Zealand, and for the first time presents ¹⁰Be derived denudation rates from the eastern Southern Alps, with estimates of the long-term weathering flux. High weathering fluxes in the Southern Alps uphold the hypothesis that mountain landscapes play an important role in carbon dioxide cycling and long-term climate stability.</p>

scholarly journals Technical note: GUARD – An automated fluid sampler preventing sample alteration by contamination, evaporation and gas exchange, suitable for remote areas and harsh conditions

2018 ◽  
Author(s):  
Arno Hartmann ◽  
Marc Luetscher ◽  
Ralf Wachter ◽  
Philipp Holz ◽  
Elisabeth Eiche ◽  
...  
Keyword(s):  
Gas Exchange ◽  
Field Experiments ◽  
Hydrological Cycle ◽  
Technical Note ◽  
Production Costs ◽  
Environmental Research ◽  
Remote Areas ◽  
Wide Range ◽  
Public And Private Sector

Abstract. Automated water sampling devices adapted to field operation have proven highly useful for environmental research as well as in the public and private sector, where natural or artificial waters need to be tested regularly for compliance with environmental and health regulations. Such autosamplers are already available on the market in slightly differing versions, but none of these devices are capable of sealing the collected samples to prevent sample alteration by contamination, evaporation or gas exchange. In many sampling cases, however, this feature is essential, for instance for studying the hydrological cycle based on isotopes in rainwater, or for monitoring waters contaminated with toxic gases or other volatile compounds detrimental to biota and human health. Therefore, we have developed a new mobile autosampler, which injects water samples directly into airtight vials, thus preventing any sample alteration. Further advantages include low production costs, compact dimensions and low weight allowing for easy transport, a wide range of selectable sampling intervals as well as a low power consumption, which make it suitable for long-term applications even in remote areas and harsh (outdoor) conditions due to its heavy-duty water-proof casing. In this paper, we demonstrate (1) the sampler's mechanical functioning, (2) the long-term stability of the collected samples with regard to evaporation and gas exchange and (3) the potential of our device in a wide variety of applications drawing on laboratory and field experiments in different karst caves, which represent one of the most challenging sampling environments.

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