Analysing the relationship between drought and soil erosion using vegetation health index and RUSLE models in Godavari middle sub-basin,India

Drought is a natural phenomenon posing severe implications for soil, groundwater and agricultural yield. It has been recognized as one of the most pervasive global change drivers to affect the soil. Soil being a weakly renewable resource takes a long time to form, but it takes no time to degrade. However, the response of soil to drought conditions as soil loss is not manifested in the existing literature. Thus, this study makes a concerted effort to analyze the relationship between drought conditions and soil erosion in the middle sub-basin of the Godavari River in India. MODIS remote sensing data was utilized for driving drought indices during 2000–2019. Firstly, we constricted Temperature condition index (TCI) and Vegetation Condition Index (VCI) from Land Surface Temperature (LST) and Enhanced Vegetation Index (EVI) derived from MODIS data. TCI and VCI were then integrated to determine the Vegetation Health Index (VHI). Revised Universal Soil Loss Equation (RUSLE) was utilized for estimating soil loss. The relationship between drought condition and vegetation was ascertained using the Pearson correlation. Most of the northern and southern watersheds experienced severe drought condition in the sub-basin during 2000–2019. The mean frequency of the drought occurrence was 7.95 months. The average soil erosion in the sub-basin was estimated to be 9.88 t ha^?1 year^?1. A positive relationship was observed between drought indices and soil erosion values (r value being 0.35). However, wide variations were observed in the distribution of spatial correlation. Among various factors, the slope length and steepness were found to be the main drivers of soil erosion in the sub-basin. Thus, the study calls for policy measures to lessen the impact of drought and soil erosion.     

The Energy Relationship between Ions and Soil Particles based on Wien Effect and Its Application in Soil Science

The interaction between ions and soil particles plays an important role in the mobilization and bioavailability of ions in soils, which is one of the main research areas of soil chemistry. The new method based on suspension Wien effect has been developed recently to determine the binding energy and adsorption energy between ions and soil particles. Compared with other methods on the basis of adsorption isotherm or ions activity, Wien effect method has more advantages including convenience and direct measurement. The term suspension Wien effect refers to the increase of electrical conductivity of suspension with increasing applied electrical field. In this review paper, we introduced the fundamentals of suspension Wien effect, the apparatus about the Wien effect measurement, and along with demonstrating their application to quantifying the particles-ions interactions for several systems of soils. Our studies indicated that divalent cations have larger binding energies and adsorption energies on soil particles than monovalent because of the electrostatic interaction. However, few studies about the interaction between Cr³⁺ and La³⁺ on soil particles showed that the binding energy and adsorption energy of trivalent cations are lower than those of divalent cations because of hydrolysis. Soil properties such as soil organic matter, soil pH, and iron oxides significantly affected the binding energy and adsorption energy of ions. Our results deepened our understanding about the non specific adsorption of ions in soil chemistry, and enlarged the research area of soil chemistry in fundamental and methodology.     

Prediction of soil properties using imaging spectroscopy: Considering fractional vegetation cover to improve accuracy

Spectroscopic techniques have become attractive to assess soil properties because they are fast, require little labor and may reduce the amount of laboratory waste produced when compared to conventional methods. Imaging spectroscopy (IS) can have further advantages compared to laboratory or field proximal spectroscopic approaches such as providing spatially continuous information with a high density. However, the accuracy of IS derived predictions decreases when the spectral mixture of soil with other targets occurs. This paper evaluates the use of spectral data obtained by an airborne hyperspectral sensor (ProSpecTIR-VS – Aisa dual sensor) for prediction of physical and chemical properties of Brazilian highly weathered soils (i.e., Oxisols). A methodology to assess the soil spectral mixture is adapted and a progressive spectral dataset selection procedure, based on bare soil fractional cover, is proposed and tested. Satisfactory performances are obtained specially for the quantification of clay, sand and CEC using airborne sensor data (R² of 0.77, 0.79 and 0.54; RPD of 2.14, 2.22 and 1.50, respectively), after spectral data selection is performed; although results obtained for laboratory data are more accurate (R² of 0.92, 0.85 and 0.75; RPD of 3.52, 2.62 and 2.04, for clay, sand and CEC, respectively). Most importantly, predictions based on airborne-derived spectra for which the bare soil fractional cover is not taken into account show considerable lower accuracy, for example for clay, sand and CEC (RPD of 1.52, 1.64 and 1.16, respectively). Therefore, hyperspectral remotely sensed data can be used to predict topsoil properties of highly weathered soils, although spectral mixture of bare soil with vegetation must be considered in order to achieve an improved prediction accuracy.     

Arsenic accumulation in the roots of Helianthus annuus and Zea mays by irrigation with arsenic-rich groundwater: Insights from synchrotron X-ray fluorescence imaging

The aim of this study was to investigate the accumulation of arsenic (As) in and on roots of Zea mays (maize) and Helianthus annuus (sunflower) by means of synchrotron-based micro-focused X-ray fluorescence imaging (μ-XRF). Plant and soil samples were collected from two field sites in the Hetao Plain (Inner Mongolia, China) which have been regularly irrigated with As-rich groundwater. Detailed μ-XRF element distribution maps were generated at the Fluo-beamline of the Anka synchrotron facility (Karlsruhe Institute of Technology) to assess the spatial distribution of As in thin sections of plant roots and soil particles. The results showed that average As concentrations in the roots (14.5–27.4 mg kg⁻¹) covered a similar range as in the surrounding soil, but local maximum root As concentrations reached up to 424 mg kg⁻¹ (H. annuus) and 1280 mg kg⁻¹ (Z. mays), respectively. Importantly, the results revealed that As had mainly accumulated at the outer rhizodermis along with iron (Fe). We therefore conclude that thin crusts of Fe-(hydr)oxides cover the roots and act as an effective barrier to As, similar to the formation of Fe plaque in rice roots. In contrast to permanently flooded rice paddy fields, regular flood irrigation results in variable redox conditions within the silty and loamy soils at our study site and fosters the formation of Fe-(hydr)oxide plaque on the root surfaces.     

Methodological comparison for quantitative analysis of fossil and recently derived carbon in mine soils with high content of aliphatic kerogen

In mine soil, quantification of soil organic carbon (OC) derived recently from biomass decomposition is complicated by the presence of fossil (geogenic) C derived from coal, oil shale, or similar material in the overburden. The only reliable method for such measurement is ¹⁴C analysis (i.e. radiocarbon dating) using instrumentation such as accelerator mass spectrometry, which is too expensive for routine laboratory analysis. We tested two previously used and two new methods for recent C quantification and compared them with ¹⁴C AMS radiocarbon dating as a reference using a set of soil samples (n = 14) from Sokolov, Czech Republic: (i) ¹³C isotope ratio composition, (ii) cross polarization magic angle spinning ¹³C nuclear magnetic resonance (CPMAS ¹³C NMR) spectroscopy, (iii) near infrared spectroscopy (NIRS) coupled with partial least squares regression and (iv) Rock–Eval pyrolysis. Conventional methods for OC determination (dry combustion, wet dichromate oxidation, loss-on-ignition) were also compared to quantify any bias connected with their use. All the methods provided acceptable recent carbon estimates in the presence of mostly aliphatic fossil C from kerogen. However, the most accurate predictions were obtained with two approaches using Rock–Eval pyrolysis parameters as predictors, namely (i) S₂ curve components and (ii) oxygen index (OI). The S₂ curve approach is based on the lower thermal stability of recent vs. fossil organic matter. The OI approach corresponded well with ¹³C NMR spectra, which showed that samples rich in recent C were richer in carboxyl C and O-alkyl C. These two methods showed the greatest potential as routine methods for recent C quantification.     

夏津县黄河故河道区土地沙化及防治

土地沙化问题的存在,不仅破坏了自然生态环境,而且对人民群众的生产和生活造成严重的影响。本文就夏津县黄河故道风蚀沙化地的发育现状、危害程度及形成原因进行分析,并提出了防治对策。     

Thermal conductivity modelling of terrestrial soil media—A comparative study

The paper describes prediction of thermal conductivity in terrestrial soil media. The model operates statistically by probability of occurrence for contacts between particular fractional compounds. It combines physical properties, specific to particular compounds, into one apparent conductance specific to the mixture. The concept of substituting grain compounds by hypothetical spheres is an essential tool to control porosity by the number of spheres, their radii and probability of contacts between them. The spheres are equal in radii. The spheres substitute compounds, regardless of the phase state. Control of particular phase states is possible by means of specific properties assigned to the spheres, at the input to the model. Performance of the model is successfully proved for many diverse terrestrial soil media in a wide range of bulk density, composition, water and water vapour content. Only the compounds of sand decline from the expected values and require introducing a correction to the thermal conductivity of sand grains. One possible explanation is that the thermal conductivity of sand is uncertain. Nevertheless, the model is useful and worth extending beyond terrestrial purposes.     

北京地区土壤背景值图的编制

本文对北京地区土壤背景值匿的编制进行了全面、系统的总结。编制土壤背景值图的基础资料有302十样点的无素测定值和运用计算机制图和因素分析法揭露的元素区域分布规律。土壤背景值图是采用分级统计图的形式。其制图单元：山区以母岩，平原地区以成土母质类型和土壤质地作为划分依据；背景值的数量分级采用显著性检验分级法。     

圈闭地形内斜坡破坏的多期性和规律性

本文以黄河上游某拟建水电站坝址场地为例,论证了圈闭地形内斜坡破坏的多期性和规律性问题。在充分的野外调查和室内研究资料的基础上,将区内的斜坡破坏分为两期,即第一期为已经失稳的老滑坡群;第二期为发育在第一期滑坡群圈闭状破裂壁之后的正处于蠕动和破坏阶段的变形坡体,进而将第一期的滑坡分为两个强度次序。同时,还揭示了圈闭地形内斜坡破坏的规律性,即随着期和序次的增高,斜坡破坏面积增大,滑坡个数增多,规模减小,强度降低,滑距变短,滑体破碎程度变弱。最后指出,上述多期性和规律性应具有普遍性意义。     

衡山自然保护区森林土壤中动物群落研究

作者通过一年的定位实验研究，初步阐明了衡山自然保护区森林土壤中动物群落的基本状况。共获得土壤动物30类，隶属于4门11纲，其中弹尾类、蝉螨类和线虫类为优势类群，占全部土壤动物捕获量的92.88％；平均土壤动物密度为67.27万个/m~3；地带性常绿林下发育的黄棕壤中土壤动物密度高达100.47万个/m~3，其次为针阔混交林和针叶林；土壤动物主要分布于森林凋落物层和土壤的腐殖质层中，向下急剧减少；在山地土壤垂直带上，土壤动物随海拔高度而变化。