Bulk Water Content Research Articles

Revised mass-radius relationships for water-rich rocky planets more irradiated than the runaway greenhouse limit

Mass-radius relationships for water-rich rocky planets are usually calculated assuming most water is present in condensed (either liquid or solid) form. Planet density estimates are then compared to these mass-radius relationships, even when these planets are more irradiated than the runaway greenhouse irradiation limit (around 1.1 times the insolation at Earth for planets orbiting a Sun-like star), for which water has been shown to be unstable in condensed form and would instead form a thick H2O-dominated atmosphere. Here we use a 1-D radiative-convective inverse version of the LMD generic numerical climate model to derive new theoretical mass-radius relationships appropriate for water-rich rocky planets that are more irradiated than the runaway greenhouse irradiation limit, meaning planets endowed with a steam, water-dominated atmosphere. As a result of the runaway greenhouse radius inflation effect introduced in previous work, these new mass-radius relationships significantly differ from those traditionally used in the literature. For a given water-to-rock mass ratio, these new mass-radius relationships lead to planet bulk densities much lower than calculated when water is assumed to be in condensed form. In other words, using traditional mass-radius relationships for planets that are more irradiated than the runaway greenhouse irradiation limit tends to dramatically overestimate -possibly by several orders of magnitude- their bulk water content. In particular, this result applies to TRAPPIST-1 b, c, and d, which can accommodate a water mass fraction of at most 2, 0.3 and 0.08%, respectively, assuming planetary core with a terrestrial composition. In addition, we show that significant changes of mass-radius relationships (between planets less and more irradiated than the runaway greenhouse limit) can be used to remove bulk composition degeneracies in multiplanetary systems such as TRAPPIST-1. Broadly speaking, our results demonstrate that non-H2/He-dominated atmospheres can have a first-order effect on the mass-radius relationships, even for rocky planets receiving moderate irradiation. Finally, we provide an empirical formula for the H2O steam atmosphere thickness as a function of planet core gravity and radius, water content, and irradiation. This formula can easily be used to construct mass-radius relationships for any water-rich, rocky planet (i.e., with any kind of interior composition ranging from pure iron to pure silicate) more irradiated than the runaway greenhouse irradiation threshold.

Evaluation of MSW Compost and Digestate Mixtures for a Circular Economy Application

In order to obtain a product with agronomic characteristics and biological stability consistent with the EU fertilizer decree for the market of EU fertilising products three different mixtures obtained from sludge digestate from municipal wastewater treatment plant, fresh compost and mature compost have been studied and characterized. For the experimental activity, the raw samples and three mixing ones were collected for the analytical characterization. The biological stability was then assessed for all samples using different stability criteria such as Specific Oxygen Uptake Rate, Rottegrad self-heating factor, Residual biogas potential. Specific enzymatic tests provided information about the status of nutrient cycles (C, P and S) and to overall microbial activity. Physical (bulk density, particle density, air capacity and water content), nutritional (C, N, P, K, Mg, and Ca) and toxicological properties (seedling growth tests on Lepidum sativum L., Cucumis sativus L., Lolium perenne L.) were also evaluated in order to assess the feasibility of agronomic use of the digestate-based mixtures. All the digestate-based mixtures responded to the main characteristics of compost quality requirements proposed in national and international regulations. The evidence found in this study highlighted that the strategy of mixing of sludge digestates with the composts allowed to mitigate the environmental risk posed by each starting material and to valorize their nutrient content.

Effect of bulk density, age, and water content on the erosional strength of streambank soils

The purpose of this study is to investigate the influence of physical properties, more specifically the bulk density and water content, to the erosional strength of streambank soils. Thirty (30) soil samples were extracted from the crest, midbank and toe of the bank at Clear Creek in Iowa City, Iowa. Out of those thirty (30) samples, six (6) samples were tested in the standard soil laboratory for obtaining their bulk density and particle size distribution, six (6) samples were tested their bulk density and heterogeneity using Gamma radiation scanning, and eighteen (18) samples were tested their erosional strengthr*f. In addition, six (6) pure Kaolinite-clay samples were constructed with various degrees of consolidation or age and water content for measuring their T>-:f using conduit flume technique. The results of the conduit flume tests revealed an increasing trend in magnitude of Hf moving from the crest to the toe of the bank. The T<--t values were 1.57, 1.53, and 1.92 Pa for the crest, midbank, and toe soils from the left bank. In similar order, the Tc.f values were 1.46, 1.47, and 1.83 Pa for the soils from the right bank. A similar trend was obtained for the bulk density based on standard laboratory test and gamma radiation scanning. According to standard laboratory test, the average bulk density values for the crest, midbank, and toe of the right bank were 1299, 1618, and 1880 kg/m3. Similarly, based on gamma radiation technique, the average bulk density values for the crest, midbank, and toe of the right bank soils were 1273 kg/m3, 1594 kg/m3 and 1863 kg/m3, respectively. This agreement in the trend of Tr-f and bulk density suggests a positive correlation between those to parameters. The results of Kaolinite-clay sample experiments demonstrated that samples with higher degree of consolidation or more age would have higher ^V. In addition, the Kaolinite-clay samples with higher water content would have lower rct. These findings suggest the presence of spatial and temporal variability in Ta of streambank soils. Therefore, incorporating this Tc,i variability in modelling streambank erosion will give more accurate results.

Shear Wave Speed of Shallow Seafloor Sediments in the Northern South China Sea and Their Correlations With Physical Parameters

AbstractIn this study, shear wave speed and related physical properties were measured for 21 seafloor sediment cores collected in the northern South China Sea. Results reveal that the shear wave speed in this study area ranges between 15.57 and 75.55 m/s and demonstrates a pattern of regional distribution. The sediment in the continental shelf area shows characteristics of high shear wave speed, high wet bulk density, low porosity, and large grain size. Contrarily, the sediment in the continental slope area exhibits characteristics of low shear wave speed, low wet bulk density, high porosity, and fine particles. Accordingly, the correlation between shear wave speed and physical properties such as porosity, wet bulk density, water content, and average grain size was studied. Prediction formulas of shear wave speed of sediments in this study area containing single and double physical parameters were established via regression analysis. The comparison between single‐parameter and double‐parameter prediction formulas indicates that the determined coefficient of the double‐parameter prediction formulas based on porosity and average grain size is higher than that of single‐parameter prediction formulas. It indicates that the double‐parameter prediction formulas based on porosity and average grain size have better prediction performance. Moreover, the prediction formulas established in this study were further compared with those of other study areas, and their differences were analyzed accordingly.

Simultaneous state and fuel property estimation in biomass boilers - theory and practice

A key factor for the further distribution of biomass boilers in modern energy systems is the capability of changing the applied feedstock during normal plant operation. This is only possible with the application of advanced control strategies that utilize knowledge about the state variables and varying fuel properties. However, neither the state variables nor the fuel properties are measurable during plant operation and, thus, need to be estimated. This contribution presents a method for the simultaneous real-time estimation of the state variables and the fuel properties in fixed-bed biomass boilers which is a novel approach in the field of biomass boilers. The method bases on an Extended Kalman Filter using a nonlinear dynamic model and measurement data from the combustion process. The estimated variables are the masses of dry fuel and water in the fuel bed as well as the fuel’s bulk density, water content, chemical composition and lower heating value. The proposed method is easy to implement and requires moderate computational effort which increases the potential of its application at actual biomass boilers. The proposed method is verified with simulation studies and by test runs performed at a representative small-scale fixed-bed biomass boiler. The estimation results show a good agreement with the actual values, demonstrating that the proposed method is capable of accurately estimating the biomass boiler’s state variables and simultaneously its fuel properties. For this reason, the presented method is a key technology to ensure the further distribution of biomass boilers in modern energy systems.

Changes in surface soil properties and macroinvertebrate communities with the conversion of secondary forests to oil palm (Elaeis guineensis) plantations

The conversion of natural forest to oil palm (Elaeis guineensis Jacq.) plantation is perceived as a threat to biodiversity conservation. The aims of this investigation were to assess variation in soil physico-chemical parameters and macroinvertebrate structures following the conversion of secondary forests to oil palm plantations, and to understand what to expect with the aging of the plantations. We hypothesised that soil properties would be improved with respect to biodiversity conservation with the aging of the oil palm plantations. Sampling was carried out in secondary forests, and in 13-, 20- and 39-year-old oil palm plantations at the La Mé Station, Côte d’Ivoire. Three sampling areas were established in each land-use type and age class, for a total of 12 sampling areas. Over a 50-m transect, litter-dwelling macroinvertebrates were sampled by using pitfall traps, and topsoil (0–10 cm) macroinvertebrates by using monoliths (50 cm by 50 cm by 10 cm), following the modified ‘Tropical soil biology and fertility’ method. Soil physical and chemical parameters were characterised. The results showed that the conversion of secondary forests to oil palm plantations was characterised by changes in soil macroinvertebrate density (–30%), taxonomic richness (–37%) and functional groups (–17%), as well as soil bulk density (+14%) and water content (+16%), after ~39 years of conversion. Soil organic carbon, total nitrogen and organic matter increased with the aging of plantations, and reached conditions similar to those of secondary forests. The human interference imposed on macroinvertebrate communities during site preparation and planting was not compensated by the reduction in the soil-degradation index over time. The results have implications for implementation of conservation agriculture and the related management practices.

Https://doi.org/10.36873/agp.v20

ABSTRACTSince 1990s, the conversion of peatlands in Central Kalimantan from forest land cover and shrubs toagricultural land can cause the change of the characteristics of the peat. For this reason, this researchon the condition of peat properties is needed, especially the physical properties as a reference materialin the management of sustainable peatlands. This study was aims to determine the characteristics ofpeat under several land cover in the transition peat and the inland peat as well as the relationshipbetween the parameters. The research was conducted in September - December 2017, where located inWest Kanamit Village, Maliku Subdistrict and Taruna Jaya Village, Jabiren Raya Subdistrict, PulangPisau Regency, Central Kalimantan Province. The laboratory analysis at the Laboratory of Agronomyand the Laboratory of Analytical, University of Palangka Raya. Sampling in this study was uses aprofile with the size of one m2. This study was uses regression analysis and correlation methods thatare conducted to determine the pattern of relationships and the relationship between the variables ofthe physical properties of the peat. The results of the study indicate there is a similarity in the physicalproperties of the transition peat of West Kanamit Village and the inland peat of Taruna Jaya Village.The level of decomposition of peat from all locations was sapric with black to reddish black color. Theaverage values of the peat in West Kanamit Village are bulk density (0.09-0.18 g cm-3), water content(451.52-1,013.18%), fiber content (7.62-14.60%), ash content (1.73-26.15%), and organic C (42.83-57.00%). The results of the study in Taruna Jaya Village had the average values as follows as bulkdensity (0.10-0.17 g cm-3), moisture content (361.79-846.99%), fiber content (7.62-14.60 %), ashcontent (0.84-2.69%), and organic C (56.44-57.52%). Hydrophobicity in all study locations were 1.1-3.4 seconds with the WDPT method and the ratio of 0.06-0.49 with the FTIR methods. Moreover, therelationship between the peat characteristics shows a positive relationship and a negative relationship.Keyword : Acrotelm, Catotelm, Transition, Inland Peat

The effect of exogenous organic matter on the thermal properties of tilled soils in Poland and the Czech Republic

PurposeOrganic matter improves soil fertility and water and thermal properties, but its content often decreases. This decrease may be mitigated by the addition of exogenous organic matter (EOM). The aim of this study was to assess the effect of EOMs, including compost from manure, slurry, and straw (Ag); industrial organic compost from sewage sludge (Ra); animal meal from animal by-products (Mb); and digestate from a biogas fry factory (Dg) on soil thermal conductivity, heat capacity, thermal diffusivity, water content, and bulk density in the top (0–15-cm) layer of two soils in Poland and the Czech Republic.Materials and methodsIrrespective of EOM type, the total yearly nitrogen application rate being 200 kg N ha−1 (100%) was from a given EOM at the rates 0, 50, 75, and 100% and the remaining parts from the mineral fertilizer. The study was conducted in 2013–2014 in Poland (Braszowice) and the Czech Republic (Pusté Jakartice) on loam silt and clay silt loam, respectively, as part of a cross-border cooperation project. The soil properties were examined using classical descriptive statistics, semivariograms, and kriging-interpolated maps.Results and discussionAnalysis of linear regressions (trends) showed that the EOM application rate influenced (positively or negatively) the soil properties in most measurement occasions. The variability of all soil properties was low and medium (coefficient of variation 7.3–34%). Geostatistical analysis indicated that the spatial dependence (C0/(C0 + Cs)) of the soil properties on the EOM-amended plots was very strong or moderate. The maps revealed that the heterogeneity and degree of patch fragmentation were greater for thermal conductivity and heat capacity than for thermal diffusivity, water content, and bulk density. In general, all the soil properties were spatially more variable in the Braszowice than Pusté Jakartice soil and in spring than autumn in both sites.ConclusionsThe spatial analysis and maps enhance the comprehensive understanding of changes in soil thermal properties in response to EOM application. Suitability of the results from the field experiments in models predicting some thermal properties based on soil bulk density and water content in relation to EOM addition was indicated. Expressing the amount of EOMs added using the organic carbon content basis (% kg OC/kg of soil) instead of the nitrogen content basis allowed identifying areas on the kriging-interpolated maps where the distribution of soil thermal properties resembled that of soil organic carbon content, water content, and bulk density. Thus, the effect of EOMs on soil thermal properties is considered along with changes in soil water content and bulk density.The results will be helpful in forecasting effects of exogenous organic matter on the soil thermal properties affecting surface-energy partitioning, temperature distribution in soil, and plant growth.

Calibration of DEM material parameters to simulate stress-strain behaviour of unsaturated soils during uniaxial compression

Discrete element method (DEM) is an appealing technique to simulate soil deformation. However, the calibration of the material parameters in the model remains challenging due to the high computational cost associated with it. In this study, the stress-strain relation of 125 unsaturated soil samples was simulated using DEM and material parameters were calibrated with Kriging. The Young's modulus and friction angle were found to be the most sensitive DEM material parameters, and they had a significant correlation with the bulk density, clay content and water content of the undisturbed soil samples. The DEM simulation showed that the deformation process was a combination of elastic and plastic processes, also at low stresses. Further improvement such as the coupling with (and calibration of) a fluid dynamics model might allow to more accurately simulate the dynamic behaviour of unsaturated soil compression.

Water in Garnet Pyroxenite from the Sulu Orogen: Implications for Crust‐Mantle Interaction in Continental Subduction Zone

AbstractMineral water contents, together with the elements and isotopes of minerals and whole‐rock, were determined for garnet pyroxenites enclosed by ultrahigh‐pressure (UHP) metamorphic gneiss at Hujialin in the Sulu orogen. The results suggest that the garnet pyroxenites were generated in the Triassic by metasomatic reaction of the mantle wedge peridotite with hydrous felsic melts derived from partial melting of the deeply subducted continental crust. Measured water contents vary from 523 to 1213 ppm for clinopyroxene, and 55 to 1476 ppm for garnet. These mineral water contents are not only correlated with mineral major and trace element abundances but also relatively homogenous within single mineral grains. Such features preclude significant disturbance of the mineral water contents during pyroxenite exhumation from the mantle depth to the surface and thus indicate preservation of the primary water contents for the UHP metasomatites. The garnet pyroxenites are estimated to have bulk water contents of 424–660 ppm, which are higher than those for the MORB source, similar to or higher than those for the OIB sources and close to the lower limit for the arc magma source. The relationships between contents of mineral water and some elements suggest that the high water contents of garnet pyroxenites are primarily determined by the abundance of water‐rich clinopyroxene. Calculated whole‐rock H2O/Ce ratios are 63–145, higher than those for Hawaiian garnet pyroxenites and SWIR abyssal pyroxenites. These observations suggest that metasomatic pyroxene‐rich lithologies have the capacity to contribute high H2O concentrations and variable H2O/Ce ratios to the mantle. This lends support to the interpretation that the source of some intraplate basalts may be a heterogeneous mixture of peridotite and pyroxenite. On the other hand, the high water contents of garnet pyroxenites suggest that the ultramafic metasomatites are an important water reservoir in the mantle wedge.

CASE STUDY ON ENHANCED LANDFILL MINING AT MONT-SAINT-GUIBERT LANDFILL IN BELGIUM: CHARACTERIZATION AND POTENTIAL OF FINE FRACTIONS

Within the framework of the “EU Training Network for Resource Recovery through Enhanced Landfill Mining – NEW-MINE”, around 371 Mg of waste were excavated from a landfill site in Mont-Saint-Guibert, Belgium. Parameters such as bulk density, water content, particle size distribution and material composition of the fine fractions (material <90 mm) were determined and analyzed. The variations of bulk density and water content with particle size were studied as well and grouped material fractions were employed for the classification of the material composition. The present article has the main objective to document and disseminate the findings on the material characterization of the fine fractions obtained in this case study, since such information is of critical relevance for the design of an effective and efficient mechanical processing in (enhanced) landfill mining projects. Additionally, the potential of fine fractions for material and energy recovery is discussed. The fine fractions accounted for about 77 wt.% of the total amount of excavated material in raw state. These fractions presented an overall bulk density range of 720-1000 kg/m3 (raw state) and a total water content range of 25-30 wt.%. Results on the material composition in dry state reveal that amounts of 2.1-19.7 wt.% “Combustibles”, 31.1-35.4 wt.% “Inert” and 0.6-1.8 wt.% “Total metals” could be recovered from fine fractions 90-10 mm, while 37.8-55.6 wt.% “Fine fractions <10 mm” could be processed further in order to increase the recovery amounts of the previous fractions and produce a soil substitute material.

Water Abundance of Dunes in Gale Crater, Mars From Active Neutron Experiments and Implications for Amorphous Phases

AbstractWe report the water abundance of Bagnold Dune sand in Gale crater, Mars by analyzing active neutron experiments using the Dynamic Albedo of Neutrons instrument. We report a bulk water‐equivalent‐hydrogen abundance of 0.68 ± 0.15 wt%, which is similar to measurements several kilometers away and from those taken of the dune surface. Thus, the dune is likely dehydrated throughout. Furthermore, we use geochemical constraints, including bulk water content, to develop compositional models of the amorphous fraction for which little information is known. We find the amorphous fraction contains ∼26‐ to 64‐wt% basaltic glass and up to ∼24‐wt% rhyolitic glass, suggesting at least one volcanic source for the dune material. We also find a range of hydrated phases may be present in appreciable abundances, either from the incorporation of eroded aqueously altered sediments or the direct alteration of the dune sand.

A mechanical-dielectric-high frequency acoustic sensor fusion for soil physical characterization

The aim of this study was to develop a new soil multi-sensor fusion by combining mechanical, dielectric and acoustic responses in layered soils for estimation of soil water content, degree of compactness and texture. The load cell, dielectric and acoustic sensors were integrated on a 25 mm diameter, 45-deg conical probe. Functioning of the dielectric sensor is based on the fringe-field between the two adjacent ring electrodes. Passive acoustic responses (emissions) at high frequency (10–350 kHz) were measured using an acoustic emission (AE) piezo sensor during probe penetration into the layered soil. The AE sensor was installed inside the cone (close to the cone tip) to receive passive AEs originating at the cone-soil interface and between soil particles surrounding the moving probe. The multi-sensor probe was evaluated using laboratory vertical penetration tests in various layered soil columns consisting of three soil types: clay, loam and sand. Each soil texture was prepared at three soil water contents (0.4, 0.6 and 0.8 × lower plastic limit) and remolded at three bulk densities (1.25, 1.4 and 1.55 Mg m−3) in the column. The acoustic frequency distribution spectra clearly distinguished the sandy soil texture (irrespective of bulk density and water content) from the clay and loam soil textures, with a relatively poor discrimination between clay and loam soil. The results indicate that the dielectric sensor output is highly correlated to soil volumetric water content (R2 = 0.78, mean absolute error (MAE) = 0.025 m3 m−3) with a minor effect of bulk density. Data fusion of mechanical, dielectric and acoustic sensors significantly improved the measurement of soil water content (R2 = 0.93, MAE = 0.014 m3 m−3). Degree of soil compactness was well predicted from data fusion of the three sensors (R2 = 0.80, MAE = 3.32%). Therefore, the multi-sensor probe developed in this study is an economical and viable instrument that shows promising potential for in-situ use in soil physical characterization. Laboratory and field evaluations to further examine the sensor for practical applications, such as on-the-go soil physical sensing in precision agriculture, are needed.

Soil load support capacity increases with time without soil mobilization as a result of age-hardening phenomenon

Soil compaction is a result of soil compression, and this effect depends on the pressure applied and the soil structure. Nevertheless, studies regarding the effects of long-term tillage systems on strengthening of particle bonds are scarce. Thus, we aimed to study the soil bond strengthening due to the age-hardening phenomenon using the soil load support capacity model of an Oxisol managed under different tillage systems in Southern Brazil. Soil samples were collected from three soil layers (0.0–0.10 m; 0.10–0.20 m and 0.20–0.30 m) and five soil tillage systems of conventional tillage; minimum tillage with chiselling performed every year or every three years; and no-tillage for 11 or 24 years. Age-hardening was investigated using the soil load support capacity model. Soil cores were equilibrated at four matric potentials (−6, −33, −100 and −500 kPa) and submitted to uniaxial compression tests to obtain preconsolidation pressure. The soil load support capacity models were affected by the tillage systems. The long-term no-tillage presented the highest soil load support capacity for the same bulk density and water content in all layers, demonstrating greater resistance to additional compaction. Higher preconsolidation pressure values in long-term no-tillage at the same soil bulk density and water content were attributed to the age-hardening phenomena, which increased the number and strength of bonds among soil particles, leading to higher soil cohesion. Longer time under no-tillage improves the soil structure and soil load support capacity. Thus, soil mobilization strongly affected the soil structure by breaking particle bonds leading to the greater compaction.

Bulk density and water content-dependent electrical resistivity analyses of different soil classes on a laboratory scale

The goal of this study was to achieve relations between electrical conductivity and the most influential soil properties which should be transferable to natural field conditions. Electrical conductivity of soil is mainly affected by soil moisture. This, for many soil applications like determination of thermal soil properties, crucial relation is focused within this article. Electrical conductivity was measured in dependency of bulk density and water content by applying a laboratory setup which enables a comparison to natural in-situ conditions. For this purpose, four different pressure loads and up to 12 saturation steps were performed on the textural soil types of sand, silt loam and clay. A comparison between electrical conductivity and saturated pore volume confirms the impact of soil moisture. For the final analysis natural conditions were specified using field capacity ranges and defined bulk densities. With these predetermined ranges of water content and bulk density a healthy regulation for defining natural conditions has been constructed. Due to this generated constraint a soil texture independent relation between electrical conductivity and soil moisture content with a correlation coefficient of r2 = 0.95 has been developed. This correlation was also implemented within the developed measurement tool of the GeoSurf project for determining the thermal potential of soil.

The transition from arable lands to rubber tree plantations in northern Thailand impacts weed assemblages and soil physical properties

In South‐East Asia, rapid land use changes in recent decades have raised concerns for biodiversity and soil conservation. Weeds provide many ecosystemic services for soil protection and support biodiversity, and could mitigate the negative effects of intensification. We investigated the changes in weed assemblages and weed–soil interactions on a chronosequence from annual crops to mature rubber tree plantations. We sampled five fields for each of four land uses in mountainous northern Thailand (rainfed upland rice, maize, young rubber tree (RT) intercropped with maize, and mature RT). We characterized weed assemblages (abundance, richness) and soil properties (bulk density, water, carbon and nitrogen content). Rice had the most diverse and abundant weed assemblages. Weed assemblages differed between (i) rice, (ii) maize and young RT with maize and (iii) mature RT. Soil water content was the highest in mature RT. Other soil properties varied strongly within and among fields, and did not vary significantly among land uses. Water and nitrogen content increased overall with living soil cover but decreased with weed species richness in mature RT. Such interactions could provide a basis for sustainable weeding practices favourable to soil and biodiversity conservation.

Simultaneous determination of soil bulk density and water content: a heat pulse‐based method

SummarySoil bulk density (ρb) and volumetric water content (θ) determine the volume fractions of soil solids, water and air, and influence mass and energy transfer in soil. It is desirable to monitor ρb and θ concurrently and non‐destructively. We present a heat pulse‐based method for simultaneous determination of ρb and θ from soil thermal properties. The method uses equations that relate ρb and θ to soil volumetric heat capacity (C) and to soil thermal conductivity (λ). We developed a three‐step procedure to calculate ρb and θ from C and λ measured by a heat pulse sensor, with soil texture and specific heat of soil solids known a priori. Laboratory evaluation of soil samples with various textures showed that the three‐step method provided reliable estimates of ρb and θ at θ values greater than the critical water content (θc) when λ started to respond notably to increases in θ. This method provides a new way to determine ρb and θ simultaneously with heat pulse sensors.Highlights We developed an approach to determine soil bulk density (ρb) and water content (θ) simultaneously with a heat pulse sensor. We estimated ρb and θ from soil thermal properties based on heat capacity and thermal conductivity models. The new approach provided reliable ρb and θ values at water contents &gt;θc, the critical value. At θ &lt; θc, the approach gave unstable results because soil thermal conductivity was insensitive to ρb.

Soil Organic Carbon Components and Their Correlation with Soil Physicochemical Factors in Four Different Land Use Types of the Northern Tarim Basin

In order to clarify the distribution of each component of soil organic carbon (SOC) in arid areas, and to develop methods to rationally solve problems caused by inefficient land use and blind tillage, we studied the effects of different land use patterns on the SOC, microbial biomass carbon (MBC), dissolved organic carbon carbon (DOC), and easily oxidized organic carbon (EOC) on four different land use types: saline soil, natural forest, sandy land, and 30 a cotton field in the northern Tarim Basin. The relationships between different carbon components and soil physicochemical factors were researched by redundancy analysis (RDA). The results showed that the SOC showed the highest value (1.92 g·kg-1) in natural forests and increased with soil depth, while the other land use types showed a downward trend as a whole. The MBC showed the highest level in natural forests, and decreased with soil depth, but there was no obvious change trends in other land use types. The highest and lowest DOC contents appeared in the 80-100 cm layer (143.23 mg·kg-1 and 30.00 mg·kg-1, respectively) in the natural forest and 30 a cotton field, respectively, and increased with soil depth in the natural forest (P<0.05). In the saline soil, the DOC content of the soil decreased with increased depth, and the contents of different soil layers showed significant differences (P<0.05). The EOC content did not show a obvious regularity in different soil layers of different land use types. Sensitivity analysis of each organic carbon component showed that the MBC was the most sensitive to soil layer changes, and the DOC was the most sensitive to different land use patterns. The MBC has a certain indication of soil layer change, which may be due to the fact that microbial biomass C in different layers has different living environments, so the content was significantly different. The DOC has a certain indication of land use types change, which may be due to the adaptation to different situations. Through the RDA, it was found that there was a positive correlation between soil components and soil water content (SWC), total nitrogen (TN) and pH, and a negative relationship between bulk density (BD) and electrical conductivity (EC). The order of importance of environmental factors to the contents of carbon components is as follows: BD > SWC > EC > TN > pH. This indicates that bulk density and water content are the main factors affecting organic carbon components in arid regions.

In Situ X-Ray Tomography Imaging of Soil Water and Cyanobacteria From Biological Soil Crusts Undergoing Desiccation

Biological soil crusts (biocrusts) are millimeter-sized microbial communities developing on the topsoils of arid lands that cover some 12% of Earth’s continental area. Biocrusts consist of an assemblage of mineral soil particles consolidated into a crust by microbial organic polymeric substances that are mainly produced by the filamentous bundle-forming cyanobacteria, among which Microcoleus vaginatus is perhaps the most widespread. This cyanobacterium is the primary producer for, and main architect of biocrusts in many arid soils, sustaining the development of a diverse microbial community. Biocrusts are only active when wet, and spend most of their time in a state of desiccated quiescence, from which they can quickly recover upon wetting. Despite their ecological importance for arid ecosystems, little is known about the mechanisms that allow biocrust organisms to endure long periods of dryness while remaining viable for rapid resuscitation upon wetting. We had previously observed the persistence of significant rates of light-dependent carbon fixation in apparently dry biocrusts dominated by M. vaginatus, indicating that it may be able to remain hydrated against a background soil of very low water potential. One potential explanation for this may be that the abundant exopolysaccharide sheaths of M. vaginatus can preferentially retain moisture thus slowing the water equilibration with the surrounding soil allowing for extended activity periods. In order to test this hypothesis we aimed to develop methodologies to visualize and quantify the water dynamics within an undisturbed biocrust undergoing desiccation. We used synchrotron based X-ray microtomography and were able to resolve the distribution of air, liquid water, mineral particles and cyanobacterial bundles at the microscale. We could demonstrate the formation of steep, decreasing gradients of water content from the cyanobacterial bundle surface outward, while the bundle volume remained stable, as the local bulk water content decreased linearly, hence demonstrating a preferential retention of water in the microbes. Our data also suggest a transfer of hydration water from the EPS sheath material into the cyanobacterial filament as desiccation progresses. This work demonstrates the value of X-ray tomography as a tool to study microbe-scale water redistribution in biocrusts.

Intrusion of shoshonitic magmas at shallow crustal depth: T–P path, H2O estimates, and AFC modeling of the Middle Triassic Predazzo Intrusive Complex (Southern Alps, Italy)

The multi-pulse shoshonitic Predazzo intrusive complex represents an ideal igneous laboratory for investigating the chemical and physical conditions of magma emplacement in a crustal context, since numerical models can be constrained by field evidence. It constitutes the most intriguing remnant of the Middle Triassic magmatic systems of the Dolomitic Area (Southern Alps), preserved by the Alpine tectonics. Predazzo Intrusive Complex comprises silica saturated (pyroxenites/gabbros to syenites), silica undersaturated (gabbros to syenites), and silica oversaturated (granites and syenogranites) rock suites. In this paper, we modeled its emplacement and evolution with a multiple thermo-/oxy-barometric, hygrometric, and EC-AFC approach. At odds with what proposed in literature but according to the field evidence, the emplacement of the Predazzo Intrusive Complex occurred at shallow depth (< 6 km). In this context, the different pulses differed slightly in bulk water content, but shared a common thermal regime, with temperatures between 1000 and 1100 °C and ~ 600 °C at low-to-moderate oxidizing conditions (− 0.1 to + 0.7 ΔFMQ). The interaction between the intrusion and the shallow crustal rocks was minimal, with Sr and Nd isotopic compositions indicating an average of 5–6% assimilation of crust. A thermo- and oxy-barometric comparison with the nearby Mt. Monzoni also enabled to speculate about the solidification time of the intrusion, which we infer took place over about 700 ka.