scholarly journals Earth's Critical Zone and hydropedology: concepts, characteristics, and advances

2010 ◽  
Vol 14 (1) ◽  
pp. 25-45 ◽  
Author(s):  
H. Lin
Keyword(s):  
Systems Approach ◽  
Water Cycle ◽  
Lower Boundary ◽  
Critical Zone ◽  
Global Alliance ◽  
Modeling Framework ◽  
Terrestrial Environment ◽  
Near Surface ◽  
Hydrologic Processes

Abstract. The Critical Zone (CZ) is a holistic framework for integrated studies of water with soil, rock, air, and biotic resources in the near-surface terrestrial environment. This most heterogeneous and complex region of the Earth ranges from the vegetation top to the aquifer bottom, with a highly variable thickness globally and a yet-to-be clearly defined lower boundary of active water cycle. Interfaces among different compartments in the CZ are critical, which provide fertile ground for interdisciplinary research. The reconciliation of coupled geological and biological cycles (vastly different in space and time scales) is essential to understanding the complexity and evolution of the CZ. Irreversible evolution, coupled cycling, interactive layers, and hierarchical heterogeneity are the characteristics of the CZ, suggesting that forcing, coupling, interfacing, and scaling are grand challenges for advancing CZ science. Hydropedology – the science of the behaviour and distribution of soil-water interactions in contact with mineral and biological materials in the CZ – is an important contributor to CZ study. The pedosphere is the foundation of the CZ, which represents a geomembrance across which water and solutes, as well as energy, gases, solids, and organisms are actively exchanged with the atmosphere, biosphere, hydrosphere, and lithosphere, thereby creating a life-sustaining environment. Hydropedology emphasizes in situ soils in the landscape setting, where distinct pedogenic features and soil-landscape relationships are essential to understanding interactive pedologic and hydrologic processes. Both CZ science and hydropedology embrace an evolutionary and holistic worldview, which offers stimulating opportunities through steps such as integrated systems approach, evolutionary mapping-monitoring-modeling framework, and fostering a global alliance. Our capability to predict the behaviour and evolution of the CZ in response to changing environment can be significantly improved if cross-site scientific comparisons, evolutionary treatment of organized complex systems, and deeper insights into the CZ can be made.

scholarly journals Experimental Investigation of the Atmosphere-Regolith Water Cycle on Present-Day Mars

Sensors ◽  
2021 ◽  
Vol 21 (21) ◽  
pp. 7421
Author(s):  
Abhilash Vakkada Ramachandran ◽  
María-Paz Zorzano ◽  
Javier Martín-Torres
Keyword(s):  
Water Content ◽  
Triple Point ◽  
Liquid Water ◽  
Water Cycle ◽  
Pure Liquid ◽  
Martian Surface ◽  
Atmospheric Water ◽  
Near Surface ◽  
Martian Regolith

The water content of the upper layers of the surface of Mars is not yet quantified. Laboratory simulations are the only feasible way to investigate this in a controlled way on Earth, and then compare it with remote and in situ observations of spacecrafts on Mars. Describing the processes that may induce changes in the water content of the surface is critical to determine the present-day habitability of the Martian surface, to understand the atmospheric water cycle, and to estimate the efficiency of future water extraction procedures from the regolith for In Situ Resource Utilization (ISRU). This paper illustrates the application of the SpaceQ facility to simulate the near-surface water cycle under Martian conditions. Rover Environmental Monitoring Station (REMS) observations at Gale crater show a non-equilibrium situation in the atmospheric H2O volume mixing ratio (VMR) at night-time, and there is a decrease in the atmospheric water content by up to 15 g/m2 within a few hours. This reduction suggests that the ground may act at night as a cold sink scavenging atmospheric water. Here, we use an experimental approach to investigate the thermodynamic and kinetics of water exchange between the atmosphere, a non-porous surface (LN2-chilled metal), various salts, Martian regolith simulant, and mixtures of salts and simulant within an environment which is close to saturation. We have conducted three experiments: the stability of pure liquid water around the vicinity of the triple point is studied in experiment 1, as well as observing the interchange of water between the atmosphere and the salts when the surface is saturated; in experiment 2, the salts were mixed with Mojave Martian Simulant (MMS) to observe changes in the texture of the regolith caused by the interaction with hydrates and liquid brines, and to quantify the potential of the Martian regolith to absorb and retain water; and experiment 3 investigates the evaporation of pure liquid water away from the triple point temperature when both the air and ground are at the same temperature and the relative humidity is near saturation. We show experimentally that frost can form spontaneously on a surface when saturation is reached and that, when the temperature is above 273.15 K (0 °C), this frost can transform into liquid water, which can persist for up to 3.5 to 4.5 h at Martian surface conditions. For comparison, we study the behavior of certain deliquescent salts that exist on the Martian surface, which can increase their mass between 32% and 85% by absorption of atmospheric water within a few hours. A mixture of these salts in a 10% concentration with simulant produces an aggregated granular structure with a water gain of approximately 18- to 50-wt%. Up to 53% of the atmospheric water was captured by the simulated ground, as pure liquid water, hydrate, or brine.

scholarly journals North polar trough formation due to in-situ erosion as a source of young ice in mid-latitudinal mantles on Mars

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
J. Alexis P. Rodriguez ◽  
Kenneth L. Tanaka ◽  
Ali M. Bramson ◽  
Gregory J. Leonard ◽  
Victor R. Baker ◽  
...  
Keyword(s):  
Katabatic Wind ◽  
Spiral Pattern ◽  
Near Surface ◽  
Valuable Source ◽  
History Of ◽  
North Polar ◽  
Human Exploration ◽  
Erosional Event

AbstractThe clockwise spiral of troughs marking the Martian north polar plateau forms one of the planet’s youngest megastructures. One popular hypothesis posits that the spiral pattern resulted as troughs underwent poleward migration. Here, we show that the troughs are extensively segmented into enclosed depressions (or cells). Many cell interiors display concentric layers that connect pole- and equator-facing slopes, demonstrating in-situ trough erosion. The segmentation patterns indicate a history of gradual trough growth transversely to katabatic wind directions, whereby increases in trough intersections generated their spiral arrangement. The erosional event recorded in the truncated strata and trough segmentation may have supplied up to ~25% of the volume of the mid-latitude icy mantles. Topographically subtle undulations transition into troughs and have distributions that mimic and extend the troughs’ spiraling pattern, indicating that they probably represent buried trough sections. The retention of the spiral pattern in surface and subsurface troughs is consistent with the megastructure’s stabilization before its partial burial. A previously suggested warm paleoclimatic spike indicates that the erosion could have occurred as recently as ~50 Ka. Hence, if the removed ice was redeposited to form the mid-latitude mantles, they could provide a valuable source of near-surface, clean ice for future human exploration.

Nanoscale Mechanical Properties of In-Situ Tribofilms Generated from ZDDP and F-ZDDP with and without Antioxidants

2007 ◽  
Vol 7 (12) ◽  
pp. 4378-4390 ◽  
Author(s):  
Anuradha Somayaji ◽  
Ramoun Mourhatch ◽  
Pranesh B. Aswath
Keyword(s):  
Electron Microscopy ◽  
Wear Debris ◽  
Surface Region ◽  
Nucleation And Growth ◽  
Near Surface ◽  
Transmission Electron ◽  
Dialkyl Dithiophosphates ◽  
Wear Tests ◽  
Diphenyl Amine

Tribofilms with thickness ranging from 100–200 nm were developed in-situ during wear tests using a zinc dialkyl dithiophosphates (ZDDP) and fluorinated ZDDP (F-ZDDP). The influence of the antioxidant alkylated diphenyl amine on the formation and properties of these tribofilm is examined. Results indicate that the thickness of the tribofilms formed when F-ZDDP is used is always thicker than the tribofilm formed with ZDDP. In addition, in the presence of antioxidants the tribofilm thickness is increased. The hardness of these tribofilms in the absence of the antioxidants is significantly higher at the near surface region (0–30 nm) when compared to the films formed in the presence of antioxidant. Nanoscratch tests conducted to examine the abrasion resistance of the tribofilms also indicate that the tribofilms formed by F-ZDDP are more resistant to scratch compared to films formed by ZDDP. In the presence of antioxidant, tribofilms formed by F-ZDDP are significantly thicker while both films behave in a similar fashion in nanoscratch tests. Transmission electron microscopy of the wear debris formed during the tests were examined and results indicate the nucleation and growth of nanoparticles of Fe3O4 with an approximate size of 5–10 nm embedded within an otherwise amorphous tribofilm.

Phosphate biogeochemical barrier for uranium in situ immobilization in an aquifer nearby sludge repository

2021 ◽  
Author(s):  
Grigory Artemiev ◽  
Alexey Safonov ◽  
Nadezhda Popova
Keyword(s):  
Essential Elements ◽  
Ion Concentration ◽  
Soluble Form ◽  
High Concentration ◽  
Rapid Reduction ◽  
Near Surface ◽  
Nitrate Ions ◽  
Uranium Migration ◽  
Storage Facilities

<p>Uranium migration in the oxidized environment of near-surface groundwater is a typical problem of many radiochemical, ore mining and ore processing enterprises that have sludge storage facilities on their territory. Uranium migration, as a rule, occurs against a high salt background due to the composition of the sludge: primarily, nitrate and sulfate anions and calcium cations. One of the ways to prevent the uranium pollution is geochemical or engineering barriers. For uranium immobilization, it is necessary to create conditions for its reduction to a slightly soluble form of uraninite and further mineralization, for example, in the phosphate form. An important factor contributing to the rapid reduction of uranium is a in the redox potential decreasing and the removal of nitrate ions, which can be achieved through the activation of microflora. It should be added that phosphate itself is one of the essential elements for the development of microflora. This work was carried out in relation to the upper aquifer (7-12 m) near the sludge storage facilities of ChMZ, which is engaged in uranium processing and enrichment. One of the problems of this aquifer, in addition to the high concentration of nitrate ions (up to 15 g / l), is the high velocity of formation waters.<br>In laboratory conditions, the compositions of injection solutions were selected containing sources of organic matter to stimulate the microbiota development and phosphates for uranium mineralization. When developing the injection composition, special attention was paid to assessing the formation of calcite deposits in aquifer conditions to partially reduce the filtration parameters of the horizon and reduce the rate of movement of formation waters. This must be achieved to ensure the possibility of long-term deposition of uranium and removal of nitrate. The composition of the optimal solution was selected and in a series of model experiments the mineral phases containing the lowest hydrated form of the uranium-containing phosphate mineral meta-otenite were obtained.<br>In situ mineral phosphate barrier Formation field tests were carried out in water horizon conditions in a volume of 100m3 by injection of an organic and phosphates mixture. As a result, at the first stage of field work, a significant decreasing nitrate ion concentration, and reducing conditions formation coupled with the dissolved uranium concentration of decreasing were noted.</p>

Mercury trends and cycling in northern Wisconsin related to atmospheric and hydrologic processes

2019 ◽  
Vol 76 (5) ◽  
pp. 831-846 ◽  
Author(s):  
C.J. Watras ◽  
D. Grande ◽  
A.W. Latzka ◽  
L.S. Tate
Keyword(s):  
Time Series ◽  
Water Cycle ◽  
Water Levels ◽  
Hydrologic Processes ◽  
Littoral Sediments ◽  
Long Term Trends ◽  
Acid Base Status ◽  
Explanatory Mechanism ◽  
Regional Water

Atmospheric deposition is the principal source of mercury (Hg) to remote northern landscapes, but its fate depends on multiple factors and internal feedbacks. Here we document long-term trends and cycles of Hg in the air, precipitation, surface water, and fish of northern Wisconsin that span the past three decades, and we investigate relationships to atmospheric processes and other variables, especially the regional water cycle. Consistent with declining emission inventories, there was evidence of declining trends in these time series, but the time series for Hg in some lakes and most fish were dominated by a near-decadal oscillation that tracked the regional oscillation of water levels. Concentrations of important solutes (SO4, dissolved organic carbon) and the acid–base status of lake water also tracked water levels in ways that cannot be attributed to simple dilution or concentration. The explanatory mechanism is analogous to the “reservoir effect” wherein littoral sediments are periodically exposed and reflooded, altering the internal cycles of sulfur, carbon, and mercury. These climatically driven, near-decadal oscillations confound short or sparse time series and complicate relationships among Hg emissions, deposition, and bioaccumulation.

scholarly journals Spatially Separated Electron and Proton Beams in a Simulated Solar Coronal Jet

2021 ◽  
Vol 923 (2) ◽  
pp. 163
Author(s):  
Ross Pallister ◽  
Peter F. Wyper ◽  
David I. Pontin ◽  
C. Richard DeVore ◽  
Federica Chiti
Keyword(s):  
Particle Acceleration ◽  
Particle Deposition ◽  
Lower Boundary ◽  
Impulsive Phase ◽  
Null Point ◽  
Solar Photosphere ◽  
In Situ Observations ◽  
Magnetic Null ◽  
Magnetic Null Point

Abstract Magnetic reconnection is widely accepted to be a major contributor to nonthermal particle acceleration in the solar atmosphere. In this paper we investigate particle acceleration during the impulsive phase of a coronal jet, which involves bursty reconnection at a magnetic null point. A test-particle approach is employed, using electromagnetic fields from a magnetohydrodynamic simulation of such a jet. Protons and electrons are found to be accelerated nonthermally both downwards toward the domain’s lower boundary and the solar photosphere, and outwards along the axis of the coronal jet and into the heliosphere. A key finding is that a circular ribbon of particle deposition on the photosphere is predicted, with the protons and electrons concentrated in different parts of the ribbon. Furthermore, the outgoing protons and electrons form two spatially separated beams parallel to the axis of the jet, signatures that may be observable in in-situ observations of the heliosphere.

scholarly journals Climate-dependent propagation of precipitation uncertainty into the water cycle

2020 ◽  
Author(s):  
Ali Fallah ◽  
Sungmin O ◽  
Rene Orth
Keyword(s):  
Hydrological Model ◽  
Water Cycle ◽  
State Of The Art ◽  
Rain Gauge ◽  
Multiple Sources ◽  
Current State ◽  
Wide Range ◽  
The Impact ◽  
Conceptual Hydrological Model

Abstract. Precipitation is a crucial variable for hydro-meteorological applications. Unfortunately, rain gauge measurements are sparse and unevenly distributed, which substantially hampers the use of in-situ precipitation data in many regions of the world. The increasing availability of high-resolution gridded precipitation products presents a valuable alternative, especially over gauge-sparse regions. Nevertheless, uncertainties and corresponding differences across products can limit the applicability of these data. This study examines the usefulness of current state-of-the-art precipitation datasets in hydrological modelling. For this purpose, we force a conceptual hydrological model with multiple precipitation datasets in > 200 European catchments. We consider a wide range of precipitation products, which are generated via (1) interpolation of gauge measurements (E-OBS and GPCC V.2018), (2) combination of multiple sources (MSWEP V2) and (3) data assimilation into reanalysis models (ERA-Interim, ERA5, and CFSR). For each catchment, runoff and evapotranspiration simulations are obtained by forcing the model with the various precipitation products. Evaluation is done at the monthly time scale during the period of 1984–2007. We find that simulated runoff values are highly dependent on the accuracy of precipitation inputs, and thus show significant differences between the simulations. By contrast, simulated evapotranspiration is generally much less influenced. The results are further analysed with respect to different hydro-climatic regimes. We find that the impact of precipitation uncertainty on simulated runoff increases towards wetter regions, while the opposite is observed in the case of evapotranspiration. Finally, we perform an indirect performance evaluation of the precipitation datasets by comparing the runoff simulations with streamflow observations. Thereby, E-OBS yields the best agreement, while furthermore ERA5, GPCC V.2018 and MSWEP V2 show good performance. In summary, our findings highlight a climate-dependent propagation of precipitation uncertainty through the water cycle; while runoff is strongly impacted in comparatively wet regions such as Central Europe, there are increasing implications on evapotranspiration towards drier regions.

scholarly journals MULTI-WAVE ULTRASONIC CONTROL OF CONCRETE

2017 ◽  
Vol 16 (4) ◽  
pp. 289-297
Author(s):  
D. Yu. Snezgkov ◽  
S. N. Leonovich
Keyword(s):  
Rayleigh Wave ◽  
Pulse Propagation ◽  
Ultrasonic Method ◽  
Physical And Mechanical Properties ◽  
Pulse Velocity ◽  
Energy Localization ◽  
Near Surface ◽  
In Situ Conditions ◽  
Selection Of

The existing non-destructive testing system of structure concrete is actually orientated on the usage of longitudinal acoustical waves. This is due to simplicity of technical realization for measuring velocity (time) of acoustical pulse propagation in bulk concrete. But a reverse side of simple measuring procedure is a loss of additional information on concrete which is contained in the accepted acoustical signal. Therefore usage of an ultrasonic concrete testing method is limited by assessment of its strength. Joint usage of several wave types, so-called multi-wave testing, allows to refine metrology parameters of the ultrasonic method and to gain more information while determining physical and mechanical properties of concrete in laboratory and in situ conditions. The paper considers testing of elongated concrete elements and structures by an ultrasonic pulsing method on the basis of longitudinal subsurface and Rayleigh waves. It has been proposed to use methodology for time selection of wave components according to amplitude parameter and it has been applied for standard acoustical transformers with considerable reverberation time and not possessing spatial selectivity Basic principle of the proposed methodology is visual (according to oscillogram of the received signal) determination of characteristic time moments which are used for calculation of differential value of a propagation velocity in the Rayleigh wave impulse. The paper presents results pertaining to simulation of acoustical pulse propagation on the basis of 0.15 m and data of concrete ultrasonic in situ testing on measuring bases from 0.25 to 1.75 m. Advantage of large baseline for sonic test is a possibility for execution of a hundred percent inspection for surface of large-sized elements and structures, and so there is no need to make a selective inspection in some control areas as it is stipulated by provided by existing regulations. Responsivity of the Rayleigh wave parameters to near surface concrete defects permits quickly and efficiently to detect crack areas in a reinforced structure. Energy localization of a surface wave in a layer having width λ/2–λ provides a possibility to ignore reinforcement availability under appropriate selection of oscillation frequency. In addition to this, large measuring baseline makes it possible to lower effect of concrete structural inhomogeneity on statistical stability for pulse velocity assessment that ultimately reveals a possibility to register an appearance of concrete acoustical elasticity effect under in situ conditions.

scholarly journals Carbon-Involved Near-Surface Evolution of Cobalt Catalyst during Reaction: An in-situ Study

2020 ◽  
Author(s):  
Feng Yang ◽  
Haofei Zhao ◽  
Wu Wang ◽  
Qidong Liu ◽  
Xu Liu ◽  
...  
Keyword(s):  
Chemical Vapor ◽  
Carbon Diffusion ◽  
Deposition Process ◽  
Catalytic Performance ◽  
Surface Evolution ◽  
Near Surface ◽  
Co Catalysts ◽  
Transmission Electron ◽  
Walled Carbon Nanotubes

Abstract When carbon-containing species are involved in reactions catalyzed by transition metals at high temperature, the diffusion of carbon on/in catalysts dramatically influence the catalytic performance. Acquiring information on the carbon-diffusion-involved evolution of catalysts at atomic level is crucial for understanding the reaction mechanism yet also challenging. For the chemical vapor deposition process of single-walled carbon nanotubes (SWCNTs), we developed methodologies to record in-situ the near-surface structural and chemical evolution of Co catalysts with carbon permeation using an aberration-corrected environmental transmission electron microscope and the synchrotron X-ray absorption spectroscopy. The nucleation and growth of SWCNTs were linked with the partial carbonization of catalysts and the alternating dissolvement-precipitation of carbon in catalysts. The dynamics of carbon atoms in catalysts brings deeper insight into the growth mechanism of SWCNTs and also sheds light on inferring mechanisms of more reactions. The methodologies developed here will find broad applications in studying catalytic and other processes.

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