Identification of optimal soil hydraulic functions and parameters for predicting soil moisture

Abstract

The accuracy of six combined methods formed by three commonly-used soil hydraulic functions and two methods to determine soil hydraulic parameters based on a soil hydraulic parameter look-up table and soil pedotransfer functions was examined for simulating soil moisture. A novel data analysis and modelling approach was used that eliminated the effects of evapotranspiration so that specific sources of error among the six combined methods could be identified and quantified. By comparing simulated and observed soil moisture at six sites of the USDA Soil Climate Analysis Network, we identified the optimal soil hydraulic functions and parameters for predicting soil moisture. Through sensitivity tests, we also showed that adjusting only the soil saturated hydraulic conductivity, K_s , is insufficient for representing important effects of macropores on soil hydraulic conductivity. Our analysis illustrates that, in general, soil hydraulic conductivity is less sensitive to K_s than to the soil pore-size distribution parameter.

Editor D. Koutsoyiannis; Associate editor D. Hughes

Citation Pan, F., McKane, R.B. and Stieglitz, M., 2012. Identification of optimal soil hydraulic functions and parameters for predicting soil moisture. Hydrological Sciences Journal, 57 (4), 723–737.     

Metasomatic hydrous fluids in amphibole peridotites from Zabargad Island (Red Sea)

Combining textural, petrological, chemical and isotopic (Sr, H and O) data for amphiboles and whole rocks from the Zabargad peridotite diapir allows three different events to be distinguished. During each event, which can be related to a specific tectonic process of the rifting of the Red Sea, hydrous fluids produced amphiboles.

The first and the second generations of amphiboles have characteristics consistent with the involvement of mantle-derived hydrous fluids. The first generation consists of scarce Ti-pargasites which crystallized from small amounts of fluid at temperatures of around 900–1000°C. Their growth was linked to magma percolation in the peridotites before their deformation during diapiric uplift. The second generation consists of Cr-pargasites which crystallized locally (and abundantly) during reaction between the peridotites and a sodium/potassium-bearing hydrous fluid at temperatures of around 700–800°C. These amphiboles grew synchronously with the diapiric uplift. The hydrous fluids probably originated in the sub-continental mantle and were released during the diapiric uplift of the peridotites.

The third generation consists of amphiboles (pargasitic hornblende, hornblende sensu lato and tremolite) which are localized in shear zones and veins. They crystallized at temperatures estimated between 700°C and 450°C, again from a sodium/potassium-bearing hydrous fluid. However, this fluid is extraneous to the peridotites, as shown by the Sr, H and O isotope compositions which suggest seawater penetration either during or after the final emplacement of the peridotite diapir.

Although the peridotite diapir was emplaced in granulitic gneisses of the pan-African deep continental crust, no evidence was found for a contribution of hydrous continental fluids in the production of the amphiboles present in the peridotite bodies of Zabargad Island.     

Convective scaling of the average dissipation rate of temperature variance in the atmospheric surface layer

The flux of sensible heat from the land surface is related to the average rate of dissipation of temperature fluctuations in the atmospheric surface layer through the temperature variance budget equation. In many cases it is desirable to estimate the heat flux from measurement or inference of the dissipation rate. Here we study how the dissipation rate scales with atmospheric stability, using three inertial range methods to calculate the dissipation rate: power spectra, second order structure functions, and third order structure functions. Experimental data are analyzed from a pair of field experiments, during which turbulent fluctuations of velocity and temperature were measured over a broad range of neutral and unstable atmospheric flows. It is shown that the temperature dissipation rate scales with a single convective power law continuously from near-neutral to strongly unstable stratification. The dissipation scaling is found to nearly match production in the near-neutral region, but to be consistently lower than production in the more convective regimes. The convective scaling is shown to offer a simplified means of computing sensible heat flux from the dissipation rate of temperature variance.Also at Johns Hopkins University, Baltimore, MarylandAlso at Los Alamos National Laboratory, Los Alamos, New Mexico.     

Tracking denudation and sediment production and transport with cosmogenic 10Be in arid,high-altitude Himalayan half-grabens,Zanskar, northern India

Understanding the extent to which local factors, including bedrock and structure, govern catchment denudation in mountainous environments as opposed to broader climate or tectonic patterns provides insight into how landscapes evolve as sediment is generated and transported through them, and whether they have approached steady-state equilibrium. We measured beryllium-10 (¹⁰Be) concentrations in 21 sediment samples from glaciated footwall and hanging wall catchments, including a set of nested catchments, and 12 bedrock samples in the Puga and Tso Morari half-grabens located in the high-elevation, arid Zanskar region of northern India. In the Puga half-graben where catchments are underlain by quartzo-feldspathic gneissic bedrock, bedrock along catchment divides is eroding very slowly, about 5 m/Ma, due to extreme aridity and ¹⁰Be concentrations in catchment sediments are the highest (~60–90 × 10⁵ atoms/g SiO₂) as colluvium accumulates on hillslopes, decoupled from their ephemeral streams. At Puga, ¹⁰Be concentrations and the average erosion rates of a set of six nested catchments demonstrate that catchment denudation is transport-limited as sediment stagnates on lower slopes before reaching the catchment outlet. In the Tso Morari half-graben, gneissic bedrock is also eroding very slowly but ¹⁰Be concentrations in sediments in catchments underlain by low grade meta-sedimentary rocks, are significantly lower (~10–35 × 10⁵ atoms/g SiO₂). In these arid, high-elevation environments, ¹⁰Be concentrations in catchment sediments have more to do with bedrock weathering and transport times than steady-state denudation rates. © 2020 John Wiley & Sons, Ltd.     

Mercury distribution, partitioning and speciation in coastal vs. inland High Arctic snow

Atmospheric mercury deposition on snow at springtime has been reported in polar regions, potentially posing a threat to coastal and inland ecosystems receiving meltwaters. However, the post-depositional fate of Hg in snow is not well known, and no data are available on Hg partitioning in polar snow. During snowmelt, we conducted a survey of Hg concentrations, partitioning and speciation in surface snow and at depth, over sea ice and over land along a 100 km transect across Cornwallis Island, NU, Canada. Total Hg concentrations [THg] in surface snow were low (less than 20 pmol L⁻¹) and were significantly higher in marine vs. inland environments. Particulate Hg in surface snow represented up to 90% of total Hg over sea ice and up to 59% over land. At depth, [THg] at the snow/sea ice interface (up to 300 pmol L⁻¹) were two orders of magnitude higher than at the snow/lake ice interface (ca. 2.5 pmol L⁻¹). Integrated snow columns, sampled over sea-ice and over land, showed that particulate Hg was mostly bound to particles ranging from 0.45 to 2.7 μm. Moreover, melting snowpacks over sea ice and over lake ice contribute to increase [THg] at the water/ice interfaces. This study indicates that, at the onset of snowmelt, most of the Hg in snow is in particulate form, particularly over sea ice. Low Hg levels in surface snow suggest that Hg deposited through early spring deposition events is partly lost to the atmosphere from the snowpack before snowmelt. The sea ice/snow interface may constitute a site for Hg accumulation, however. Further understanding of the cycling of mercury at the sea ice/snow and sea ice/seawater interfaces is thus warranted to fully understand how mercury enters the arctic food webs.     

Dark energy model with variable q and ω in LRS Bianchi-II space-time

The present study deals with spatial homogeneous and anisotropic locally rotationally symmetric (LRS) Bianchi-II dark energy model in general relativity. The Einstein’s field equations have been solved exactly by taking into account the proportionality relation between one of the components of shear scalar $(\sigma^{1}_{1})$ and expansion scalar (?), which, for some suitable choices of problem parameters, yields time dependent equation of state (EoS) and deceleration parameter (DP), representing a model which generates a transition of universe from early decelerating phase to present accelerating phase. The physical and geometrical behavior of universe have been discussed in detail.     

Ecotoxicological approach for assessing the contamination of a Hawaiian coral reef ecosystem (Honolua Bay, Maui) by metals and a metalloid

The goal of this study was to assess the contamination of Honolua Bay using an ecotoxicological approach. First, the concentrations of 9 contaminants (metals and metalloid) were assessed in sediments and tropical marine organisms (alga Halimeda kanaloana, goatfish Parupeneus multifasciatus and urchin Tripneustes gratilla) sampled from Honolua and surrounding Bays. Then, the ecological parameters characterizing coral health (e.g. coral cover) were evaluated in Honolua Bay in the context of these contaminants. High concentrations of Co, Cr, Mn, Ni, and V in sediments from Honolua and Honokohau Bay were measured, but these concentrations were not mirrored in the organisms examined, except for Mn, suggesting that the metals are generally bound in chemically inert forms in these sediments. Moreover, few anthropogenic activities impact these bays and so the elevated Co, Cr, Mn, Ni and V concentrations in sediments appear to stem from their high natural background in Honolua and Honokohau watersheds. An analysis of the relationship between the ecological parameters and metal concentrations in Honolua Bay revealed a significant correlation between coral cover and Co, Cr, Mn, Ni, V, Zn concentrations in sediments, with coral cover decreasing with increasing metal concentration. Collectively, however, the data suggest that a complex mixture of land-based stressors (e.g. sediment, metals, nutrients) affect the coral health in Honolua Bay, rather than metal stress alone.     

Fluid–rock interactions associated with regional tectonics and basin evolution

An integrated approach consisting of fracture analysis, petrography, carbon, oxygen and strontium‐isotope analyses, as well as fluid‐inclusion micro‐thermometry, led to a better understanding of the evolution of fluid–rock interactions and diagenesis of the Upper Permian to Upper Triassic carbonates of the United Arab Emirates. The deposited carbonates were first marked by extensive early dolomitization. During progressive burial, the carbonates were affected by dolomite recrystallization as well as precipitation of vug and fracture‐filling dolomite, quartz and calcite cements. After considerable burial during the Middle Cretaceous, sub‐vertical north–south oriented fractures (F1) were cemented by dolomite derived from mesosaline to hypersaline fluids. Upon the Late Cretaceous maximum burial and ophiolite obduction, sub‐vertical east–west fractures (F2) were cemented by dolomite (Dc2) and saddle dolomite (Ds) derived from hot, highly saline fluids. Then, minor quartz cement has precipitated in fractures from hydrothermal brines. Fluid‐inclusion analyses of the various diagenetic phases imply the involvement of increasingly hot (200°C) saline brines (20 to 23% NaCl eq.). Through one‐dimensional burial history numerical modelling, the maximum temperatures reached by the studied rocks are estimated to be in the range of 160 to 200°C. Tectonically‐driven flux of hot fluids and associated diagenetic products are interpreted to have initiated during the Late Cretaceous maximum burial and lasted until the Oligocene–Miocene compressional tectonics and related uplift. The circulation of such hydrothermal brines led to partial dissolution of dolomites (Dc2 and Ds) and to precipitation of hydrothermal calcite C1 in new (mainly oriented north–south; F3) and pre‐existing, reactivated fractures. The integration of the obtained data confirms that the diagenetic evolution was controlled primarily by the interplay of the burial thermal evolution of the basin and the regional tectonic history. Hence, this contribution highlights the impacts of regional tectonics and basin history on diagenetic processes, which may subsequently affect reservoir properties.     

Répartition de l'uranium et du thorium dans les apatites : implications pour la thermochronologie UTh/He

The UTh/He thermochronology technique assumes a homogeneous distribution of U and Th within the analysed crystals. Cathodoluminescence imaging reveals a strong chemical heterogeneity within apatite a mineral widely used for UTh/He dating. This heterogeneity is then susceptible to induce large errors when calculating the UTh/He age. Chemical analysis using laser ablation ICP–MS of the various zones shown by cathodoluminescence display a link between the Ce, U and Th concentration and the luminescence intensity allowing the UTh/He age to be corrected for zonation. To cite this article: M. Jolivet et al., C. R. Geoscience 335 (2003).     

The Phase A study of the ESA M4 mission candidate ARIEL

ARIEL, the Atmospheric Remote sensing Infrared Exoplanet Large survey, is one of the three M-class mission candidates competing for the M4 launch slot within the Cosmic Vision science programme of the European Space Agency (ESA). As such, ARIEL has been the subject of a Phase A study that involved European industry, research institutes and universities from ESA member states. This study is now completed and the M4 down-selection is expected to be concluded in November 2017. ARIEL is a concept for a dedicated mission to measure the chemical composition and structure of hundreds of exoplanet atmospheres using the technique of transit spectroscopy. ARIEL targets extend from gas giants (Jupiter or Neptune-like) to super-Earths in the very hot to warm zones of F to M-type host stars, opening up the way to large-scale, comparative planetology that would place our own Solar System in the context of other planetary systems in the Milky Way. A technical and programmatic review of the ARIEL mission was performed between February and May 2017, with the objective of assessing the readiness of the mission to progress to the Phase B1 study. No critical issues were identified and the mission was deemed technically feasible within the M4 programmatic boundary conditions. In this paper we give an overview of the final mission concept for ARIEL as of the end of the Phase A study, from scientific, technical and operational perspectives.