An Analytic Solution to Well-water Level Changes under Barometric Pressure

Under barometric pressure,groundwater flow in well-aquifer systems is a kind of hydro-mechanical coupling problem.Applying the flux boundary conditions on borehole wall and water pressure equilibrium conditions inside and outside the borehole wall under barometric pressure(BP),an analytic solution to well-water level changes has been proposed in this paper.The formulation shows that the BP coefficients increase with time and tend to BP constant.The Change of BP coefficients over time depends only on the ratio of transmissivity(T) to the well radius squared(r2w),and has nothing to do with the change in BP.The BP constant only relates to aquifer loading efficiency(B),and has nothing to do with the aquifer transmissivity and well radius.The BP coefficients change over time in the analytic formulation is consistent with the analysis of measured data from the Nanxi wells.Based on the BP coefficient changes over time,a parameter estimation method is suggested and discussed in its application to the estimation of the aquifer BP constant(or B) and transmissivity by using the Nanxi well data.     

Study on a failed dip slope with a thin sandy layer in 2004 Niigata-ken Chuetsu Earthquake

Among the extensive failed slopes in the 2004 Niigata-ken Chuetsu Earthquake, Japan, a dip slope at Yokowatashi, Ojiya, was investigated intensively. The sliding plane was along a weak thin tuff sandy layer which had been deeply weathered. Triaxial compression tests and plane strain compression tests were performed on undisturbed specimens obtained by block sampling and boring sampling to evaluate the strength that was mobilized on the sliding plane. Stability analysis based on the test results reveals that, at normal time, without earthquake and without an extremely high groundwater level, the slope is stable. Furthermore, the calculation of earthquake-induced displacement provides a reasonable simulation of the failure of this slope.     

Reduction of structural Fe(III) in nontronite by methanogen Methanosarcina barkeri

Clay minerals and methanogens are ubiquitous and co-exist in anoxic environments, yet it is unclear whether methanogens are able to reduce structural Fe(III) in clay minerals. In this study, the ability of methanogen Methanosarcina barkeri to reduce structural Fe(III) in iron-rich smectite (nontronite NAu-2) and the relationship between iron reduction and methanogenesis were investigated. Bioreduction experiments were conducted in growth medium using three types of substrate: H₂/CO₂, methanol, and acetate. Time course methane production and hydrogen consumption were measured by gas chromatography. M. barkeri was able to reduce structural Fe(III) in NAu-2 with H₂/CO₂ and methanol as substrate, but not with acetate. The extent of bioreduction, as measured by the 1,10-phenanthroline method, was 7-13% with H₂/CO₂ as substrate, depending on nontronite concentration (5-10 g/L). The extent was higher when methanol was used as a substrate, reaching 25-33%. Methanogenesis was inhibited by Fe(III) reduction in the H₂/CO₂ culture, but enhanced when methanol was used. High charge smectite and biogenic silica formed as a result of bioreduction. Our results suggest that methanogens may play an important role in biogeochemical cycling of iron in clay minerals and may have important implications for the global methane budget.     

Which households are most distant from health centers in rural China? Evidence from a GIS network analysis

In this paper we have two objectives—one empirical; one methodological. Although China’s leaders are beginning to pay attention to health care in rural China, there are still concerns about access to health services. To examine this issue, we use measures of travel distances to health services to examine the nature of coverage in Shaanxi Province, our case study. The mean distance by road to the nearest health center is still more than 6 km. When we use thresholds for access of 5 and 10 km we find that more than 40 (15) percent of the rural population lives outside of these 5 (10) kilometer service areas for health centers. The nature of the access differs by geographical region and demographic composition of the household. The methodological contribution of our paper originates from a key feature of our analysis in which we use Geographic Information System (GIS) network analysis methods to measure traveling distance along the road network. We compare these measures to straight-line distance measures. Road distances (produced by network analysis) produce measures (using means) that are nearly twice as great as straight-line distances. Moreover, the errors in the measures (that is, the difference between road distances and straight-line distances) are not random. Therefore, traditional econometric methods of ameliorating the effects of measurement errors, such as instrument variables regression, will not produce consistent results when used with straight-line distances.     

Mössbauer hyperfine parameters of iron species in the course of <Emphasis Type="Italic">Geobacter</Emphasis>-mediated magnetite mineralization

Amorphous ferric iron species (ferrihydrite or akaganeite of <5 nm in size) is the only known solid ferric iron oxide that can be reductively transformed by dissimilatory iron-reducing bacteria to magnetite completely. The lepidocrocite crystallite can be transformed into magnetite in the presence of abiotic Fe(II) at elevated pH or biogenic Fe(II) with particular growth conditions. The reduction of lepidocrocite by dissimilatory iron-reducing bacteria has been widely investigated showing varying results. Vali et al. (Proc Natl Acad Sci USA 101:16121–16126, 2004) captured a unique biologically mediated mineralization pathway where the amorphous hydrous ferric oxide transformed to lepidocrocite was followed by the complete reduction of lepidocrocite to single-domain magnetite. Here, we report the ⁵⁷Fe Mössbauer hyperfine parameters of the time-course samples reported in Vali et al. (Proc Natl Acad Sci USA 101:16121–16126, 2004). Both the quadrupole splittings and linewidths of Fe(III) ions decrease consistently with the change of aqueous Fe(II) and transformations of mineral phases, showing the Fe(II)-mediated gradual regulation of the distorted coordination polyhedrons of Fe³⁺ during the biomineralization process. The aqueous Fe(II) catalyzes the transformations of Fe(III) minerals but does not enter the mineral structures until the mineralization of magnetite. The simulated abiotic reaction between Fe(II) and lepidocrocite in pH-buffered, anaerobic media shows the simultaneous formation of green rust and its gradual transformation to magnetite plus a small fraction of goethite. We suggested that the dynamics of Fe(II) supply is a critical factor for the mineral transformation in the dissimilatory iron-reducing cultures.     

Mercury contamination and its potential health effects in a lead-zinc mining area in the karst region of Guangxi, China

Mercury contamination of the environment is of worldwide concern because of its global presence and its potent neurotoxicity. Mining, smelting and the electronics industry are the main sources of Hg pollution. However, few studies have been performed to investigate systemic Hg contamination in metal mining regions. In this study, concentrations of Hg in air, farmland soil, and crops were measured in a Pb-Zn mining area in the karst region of Guangxi, China. Key factors that could affect Hg distribution, such as the fate of waste ore and waste residue, were analyzed. Geo-statistical methods were adopted to analyze the characteristics of spatial structure and distribution of Hg. The results show that Hg contamination in this region is serious. The total mercury (T-Hg) content is far higher than the Level II Limit Value of Chinese Soil Standards of 0.30 mg kg⁻¹, showing obvious directional characteristics from WNW to ESE. Highest Hg concentrations were found in the WNW portion of the study area. The contamination of paddy soil is higher than that in dry farmland soil. The vertical distribution of T-Hg and its decrease with depth suggest that the important sources are waste water irrigation and the improper disposal of the waste ore and waste rock. The T-Hg concentrations in the agricultural products examined exceed the Chinese tolerance value (0.02 mg kg⁻¹ for rice and 0.01 mg kg⁻¹ for vegetables), indicating the seriousness of the problem. The ecological environment and the safety of food grown in this mining area are being affected, with the result that human health is possibly being affected.     

Moving Surface Spline Interpolation Based on Green’s Function

Some commonly used interpolation algorithms are analyzed briefly in this paper. Among all of the methods, biharmonic spline interpolation, which is based on Green’s function and proposed by Sandwell, has become the mainstream method for its high precision, simplicity and flexibility. However, the minimum curvature method has two flaws. First, it suffers from undesirable oscillations between data points, which is solved by interpolation with splines in tension. Second, the computation time is approximately proportional to the cube of the number of data constraints, making the method slow for situations with dense data coverage. Focusing on the second problem, this paper introduces the moving surface spline interpolation method based on Green’s function, and the interpolation error equations are deduced. Because the proposed method only chooses the nearest data points by using the merge sort algorithm for interpolating, the computation time is greatly decreased. The optimal number of the nearest points can be determined by using the interpolation error estimation equation. No matter how many data points there are, this method can be implemented without difficulty. Examples show that the proposed method can obtain high interpolation precision and high computation speed at the same time.     

吊脚支护桩在康大凤凰国际基坑中的应用

根据青岛市特殊的地层及基坑案例,对长螺旋吊脚桩支护结构设计、计算和应用进行了介绍和分析。工程实例表明,该支护结构与传统有嵌固支护桩一样能有效控制基坑变形。     

水沙过程变异下洞庭湖系统功能的连锁响应

从作用于洞庭湖系统功能的水沙过程人手,探讨水沙过程变异下湖泊系统功能的连锁响应认为:①洞庭湖是一个由其形态系统功能、生态系统功能和服务系统功能共同维系的巨系统;②水沙条件变化导致湖盆结构变形、湖面湖容缩小、生物多样性不稳定、航运里程缩短、水环境净化能力减弱、东方田鼠与钉螺极度膨胀、鱼类捕捞产量和水资源量减少等响应现象;...     

Evaluation on the two filling functions for the recovery of forest information in mountainous shadows on Landsat ETM + Image

In general,topographic shadow may reduce performance of forest mapping over mountainous regions in remotely sensed images.In this paper,information in shadow was synthesized by using two filling techniques,namely,roifill and imfill,in order to improve the accuracy of forest mapping over mountainous regions.These two methods were applied to Landsat Enhanced Thematic Mapper (ETM +) multispectral image from Dong Yang County,Zhejiang Province,China.The performance of these methods was compared with two conventi...