Impact of acid effluent from Kawah Ijen crater lake on irrigated agricultural soils: Soil chemical processes and plant uptake

Volcanogenic contamination of irrigation water, caused by effluent from the hyperacid Ijen crater lake, has severely affected the properties of agricultural soils in East Java, Indonesia. From a comparison of acidified topsoil with subsoil and with top- and subsoil in a reference area, we identified processes responsible for changes in soil and soil solution chemistry induced by acid irrigation water, with emphasis on the nutrients Ca, Mg, Fe, and Mn, and on Al, which may become phytotoxic under acid conditions in soils. Compositional data for bulk soil composition and selective extractions with 1 M KCl and 0.2 M acid ammonium oxalate are used in a mass balance approach to specify element fluxes, including uptake by rice plants. The results show that input via irrigation water has produced an increase in the total aluminum content in the affected topsoil, which is of the same order of magnitude as the increase in labile Al. High bioavailability of Al, as reflected by concentrations in KCl extracts, is consistent with elevated concentrations observed in rice plants. In contrast, and despite the high input via irrigation water, Ca and Mg concentrations have decreased in all measured soil fractions through dissolution of amorphous phases and minerals, and through competition of Al for adsorption sites on the exchange complex and plant roots. Strong leaching is also evident for Fe and especially Mn. In terms of the overall mass balance of the topsoil, plant uptake of Al, Ca, Fe, Mg and Mn is negligible. If the use of acid irrigation would be stopped and the soil pH were to increase to values above 4.5, the observed phytotoxicity of Al will be halted. However, crops may then become fully dependent on the input from irrigation water or fertilizer for essential elements, due to the previous removal from the topsoil through leaching.     

Spatio-temporal analysis of potential aquifer recharge: Application to the Basin of Mexico

Regional estimates of aquifer recharge are needed in data-scarce regions such as the Basin of Mexico, where nearly 20 million people are located and where the Basin’s aquifer system represents the main water source. In order to develop the spatio-temporal estimates of aquifer recharge and to analyze to what extent urban growth has affected aquifer recharge, this work presents a daily soil water balance which uses different vegetation and soil types as well as the effect of topography on climatological variables and evapotranspiration. The soil water balance was applied on a daily time step in the Basin of Mexico for the period 1975–1986, obtaining an annually-lumped potential recharge flow of 10.9–23.8 m³/s (35.9–78.1 mm) in the entire Basin, while the monthly values for the year with the largest lumped recharge value (1981 = 78.1 mm) range from 1 m³/s (0.3 mm) in December to 87.9 m³/s (23.7 mm) in June. As aquifer recharge in the Basin mainly occurs by subsurface flow from its enclosing mountains as Mountain Block Recharge, urban growth has had a minimal impact on aquifer recharge, although it has diminished recharge in the alluvial plain.     

PS溶液渗透对非饱和土的增强效应研究

特定模数硅酸钾溶液(PS)已广泛的用于我国西北干旱地区土遗址加固保护工程中,并且取得了显著的效果.但是PS对潮湿地区遗址土加固效果,目前尚缺乏成熟的理论和实验验证.本文从室内试验的资料出发,研究PS对潮湿地区土遗址非饱和土的增强效应.本次研究土样取自位于潮湿环境中的浙江杭州良渚土遗址(3000 B C.),在实验室内对...     

Simulation of soil–foundation–structure interaction of Hualien large-scale seismic test using dynamic centrifuge test

Understanding the soil–structure interaction (SSI) mechanism is crucial in the seismic design of nuclear power plant (NPP) containment systems. Although the numerical analysis method is generally used in seismic design, there is a need for experimental verification for the reliable estimation of SSI behavior. In this study a dynamic centrifuge test was performed to simulate the SSI behavior of a Hualien large-scale seismic test (LSST) during the Chi-Chi earthquake. To simulate the soil profile and dynamic soil properties of the Hualien site, a series of resonant column (RC) tests was performed to determine the model soil preparation conditions, such as the compaction density and the ratio of soil–gravel contents. The variations in the shear wave velocity (V_S) profiles of the sand, gravel, and backfill layers in the model were estimated using the RC test results. During the centrifuge test, the V_S profiles of the model were evaluated using in-flight bender element tests and compared with the in-situ V_S profile at Hualien. The containment building model was modeled using aluminum and the proper scaling laws. A series of dynamic centrifuge tests was performed with a 1/50 scale model using the base motion recorded during the Chi-Chi-earthquake. In the soil layer and foundation level, the centrifuge test results were similar to the LSST data in both the time and frequency domains, but there were differences in the structure owing to the complex structural response as well as the material damping difference between the concrete in the prototype and aluminum in the model. In addition, as the input base motion amplitude was increased to a maximum value of 0.4g (prototype scale), the responses of the soil and containment model were measured. This study shows the potential of utilizing dynamic centrifuge tests as an experimental modeling tool for site specific SSI analyses of soil–foundation–NPP containment system.     

ROCESSES OF EPHEMERAL GULLY EROSION

IINTRoDUCTIONEphemeralgulliesaresmallerosionalchannelsonagriculturalIandscapescausedbytheconcentrationofoverlandflowtypicallybetweentwoopposingslopes(ahollow),oftenformedduringasingIerainfaIlevent.Sincethescouredsoilvolumeisnotverylargewithinthesegullies,farmerscaneasilyrefillthem.Ingeneral,ephemeralgulliescanreappearatornearthesamelocationonayearlybasisbecausethesurfacetopograPhyofthefielddoesnotchangeappreciably.Mostephemeralgulliesoccuroncultivatedfieldswithhighlyerodiblesoils,withlit…     

新一轮土地利用总体规划修编思路探讨——以即墨市土地利用总体规划修编为例

通过即墨市土地利用总体规划修编试点工作,提出了县级土地利用规划修编思路:力求土地利用现状数据可靠,实现图(实地)数一致;要对土地资源利用状况进行全面地分析;要科学地预测各业用地,综合协调和平衡用地规模;要运用专家论证与公众参与相结合的方法,逐步优化规划方案;应积极采用信息技术,并结合制度创新提高规划的科学性和可行性。     

从土壤腐殖质分组到分子有机质组学认识土壤有机质本质

梳理了与土壤生态系统功能相联系的,特别是对固碳减排的土壤有机质本质认识的研究进展及路径,探讨了经典腐殖质学说存在的问题,概述了新近的有机质保护稳定学说及腐殖质组学学说,并追溯了生物标志物有机质分子研究,最后从土壤学的基本理念和理论出发讨论和重新认识土壤有机质的本质及其价值。从形成条件、分离条件和分子鉴定等多方面分析,土壤腐殖质形成和稳定学说越来越显示出局限性;而面向气候变化的碳固定研究可以深入探析土壤有机质的复杂存在状态。越来越认识到土壤有机质是投入土壤的有机物质经不同程度生物利用或降解的产物残留,只是被土壤不同程度地区隔和封闭,本质上仍是分子量变化极大的生命源有机物的集合。因此,可通过生物标志物分子作为靶标在土壤中提取和识别,该技术的发展将孕育萌生土壤有机质分子组学。后者可以用于判读土壤有机质的结构支撑、反应活性和促生功能等方面的本质差别,这些差别可能是由有机分子组成结构及存在状态所决定而不是由有机分子稳定性决定的。从这个概念出发,类似于土壤微生物分子生态,土壤有机质的丰度、组成、结构与功能间的联系可能是土壤有机质本质的核心问题。对这种关系的量化和参数化表征可用以探索土壤有机质永续固定,且可以保持生命活性的土壤有机质的管理策略及技术,并配合土壤的团聚体理论诠释土壤的本质和生态系统功能服务,这将是未来土壤学服务人类可持续发展的理论立足点。     

Surface soil moisture retrievals from remote sensing: Current status,products & future trends

Advances in Earth Observation (EO) technology, particularly over the last two decades, have shown that soil moisture content (SMC) can be measured to some degree or other by all regions of the electromagnetic spectrum, and a variety of techniques have been proposed to facilitate this purpose.In this review we provide a synthesis of the efforts made during the last 20 years or so towards the estimation of surface SMC exploiting EO imagery, with a particular emphasis on retrievals from microwave sensors. Rather than replicating previous overview works, we provide a comprehensive and critical exploration of all the major approaches employed for retrieving SMC in a range of different global ecosystems. In this framework, we consider the newest techniques developed within optical and thermal infrared remote sensing, active and passive microwave domains, as well as assimilation or synergistic approaches. Future trends and prospects of EO for the accurate determination of SMC from space are subject to key challenges, some of which are identified and discussed within.It is evident from this review that there is potential for more accurate estimation of SMC exploiting EO technology, particularly so, by exploring the use of synergistic approaches between a variety of EO instruments. Given the importance of SMC in Earth’s land surface interactions and to a large range of applications, one can appreciate that its accurate estimation is critical in addressing key scientific and practical challenges in today’s world such as food security, sustainable planning and management of water resources. The launch of new, more sophisticated satellites strengthens the development of innovative research approaches and scientific inventions that will result in a range of pioneering and ground-breaking advancements in the retrievals of soil moisture from space.     

Three-dimensional finite element analysis of the direct simple shear test

This paper investigates two aspect of the direct simple shear (DSS) using three-dimensional finite element analysis. Firstly, the different total stress paths followed by DDS devices that impose constant cross-sectional area using a stiff external boundary, and those that use a constant total stress lateral boundary condition are explored. This is done by conducting finite element analysis of a single cubic element. It is shown that this element may be subjected to perfect simple shear using four different boundary condition types. Each boundary condition type results in the same effective stress path, but different total stress paths and excess pore pressures. The boundary condition types are related to DSS devices in use. The second aspect investigated is the fact that no DSS device can impose true simple shear conditions, as they are unable to generate the required complementary shear stress on the vertical boundaries. Full three-dimensional finite element analysis of a UWA/Berkeley type simple shear device, which has a constant total stress lateral boundary, is then presented. The results are compared to the ideal solution and effects of stress non-homogeneity on the friction angle and undrained shear strength, deduced from a standard interpretation, are established.     

Changes in the thermal and hydraulic regime within the active layer in the Qinghai-Tibet Plateau

The change trends of air temperature,precipitation and evaporation from 1999 to 2008 shows that the climate in the Qinghai-Tibet Plateau permafrost region had become warmer.The analysis of the systematic active-layer data monitoring network along the Qinghai-Tibet Highway indicated that the active-layer thickness had been increasing and the soil temperature was rising.The soil temperature was rising in winter but not at the end of spring or during the entire summer.With thickening and warming of the active layer,the liquid water content of the active layer had an obvious downward migration and liquid water content in the top horizons decreased,but in the deeper horizons it increased.