Transport of Sr2+ and SrEDTA2- in partially-saturated and heterogeneous sediments

Strontium-90 has migrated deep into the unsaturated subsurface beneath leaking storage tanks in the Waste Management Areas (WMA) at the U.S. Department of Energy's (DOE) Hanford Reservation. Faster than expected transport of contaminants in the vadose zone is typically attributed to either physical hydrologic processes such as development of preferential flow pathways, or to geochemical processes such as the formation of stable, anionic complexes with organic chelates, e.g., ethylenediaminetetraacetic acid (EDTA). The goal of this paper is to determine whether hydrological processes in the Hanford sediments can influence the geochemistry of the system and hence control transport of Sr(2+) and SrEDTA(2-). The study used batch isotherms, saturated packed column experiments, and an unsaturated transport experiment in an undisturbed core. Isotherms and repacked column experiments suggested that the SrEDTA(2-) complex was unstable in the presence of Hanford sediments, resulting in dissociation and transport of Sr(2+) as a divalent cation. A decrease in sorption with increasing solid:solution ratio for Sr(2+) and SrEDTA(2-) suggested mineral dissolution resulted in competition for sorption sites and the formation of stable aqueous complexes. This was confirmed by detection of MgEDTA(2-), MnEDTA(2-), PbEDTA(2-), and unidentified Sr and Ca complexes. Displacement of Sr(2+) through a partially-saturated undisturbed core resulted in less retardation and more irreversible sorption than was observed in the saturated repacked columns, and model results suggested a significant reservoir (49%) of immobile water was present during transport through the heterogeneous layered sediments. The undisturbed core was subsequently disassembled along distinct bedding planes and subjected to sequential extractions. Strontium was unequally distributed between carbonates (49%), ion exchange sites (37%), and the oxide (14%) fraction. An inverse relationship between mass wetness and Sr suggested that sandy sediments of low water content constituted the immobile flow regime. Our results suggested that the sequestration of Sr(2+) in partially-saturated, heterogeneous sediments was most likely due to the formation of immobile water in drier regions having low hydraulic conductivities.     

Environmental disasters,migration and displacement. Insights and developments from L’Aquila's case

This paper analyses the environmentally-induced migration and displacement resulting from L’Aquila's earthquake of 2009. After a general critical overview of the social science literature on this topic, the main changes in the migration system are analysed looking at the roots and trajectories of the forced human displacement that followed the earthquake, and reflecting on the challenges related to post-earthquake demographic movements and post-disaster resettlement. Through the analysis of the pre disaster (2002–2008) and recovery period (2009–2013) data, this paper offers a general model of how environmental disaster might affect migration and displacement and suggests the main challenges related to the post-disaster governance. Relying on ISTAT data on internal migration in Italy this paper argues that the post-seismic recovery period is characterized by a strong increase of out-flows from L’Aquila to other provinces, within the Abruzzo region and outside it, in particular toward the closest regions (Latium, Campania).     

Estimating the influence of overhead transmission power lines and landscape context on the density of little bustard Tetrax tetrax breeding populations

Collision with conductors and earth cables is a known impact generated by transmission power lines, however there is virtually no information on how these infrastructures might affect bird distribution in a landscape context. With this work we specifically hypothesise that transmission power lines may affect the occurrence of a threatened bird, the little bustard (Tetrax tetrax). To test this hypothesis we used a Stochastic Dynamic Methodology (StDM), analysing the effects of power lines in a landscape perspective and simulating population trends as a response to power line installation and habitat changes induced by agricultural shifts in southern Portugal. The data used in the dynamic model construction included relevant gradients of environmental conditions and was sampled during the breeding seasons of 2003-2006. Transmission power lines were significantly avoided by the little bustard and the developed StDM model showed that the distance to these utility structures is the most important factor determining breeding densities in sites with suitable habitat for the species, which possibly leads to displacement of populations and habitat fragmentation. The model simulations also provided the base to analyse the cumulative effects caused by the habitat degradation that can ultimately lead to the extinction of local populations. Within priority conservation sites, the dismantling of existing transmission lines should be considered whenever possible, in order to ensure adequate breeding habitat. The model is considered useful as an auxiliary tool to be used in environmental impact assessments, management and conservation studies.     

基于电磁感应和位移传感原理的电梯门锁啮合长度检测研究

电梯门锁锁紧元件啮合状态可靠性是确保电梯门系统安全运行的重要保障。针对现有电梯门锁啮合长度检验方法存在的测量精度不足、自动化程度低、通用性不强等问题,提出了一种基于传感器的检测方法。分析了电磁感应开关通断检测原理和接触式位移传感工作原理,在此基础上开发了门锁啮合长度检測装置,并介绍了使用该装置的检验步骤。实测结果表明:该检验方法和检验装置可以实现门锁啮合长度的快速准确检验,数据可重复性高。     

Visitor Response to Management Regulations—A Study Among Recreationists in Southern Norway

/ The objectives of nature area management are often twofold: To protect the natural environment and to facilitate recreational use. In order to maintain the natural setting, it is sometimes necessary to regulate the recreational use of an area. In deciding on a management action, one problem can be the lack of knowledge about the effects of management actions on visitors. In order to enhance the knowledge base for future management practices, this study empirically evaluates the effects of management regulations in a Norwegian nature area. In this area camping outside commercial campgrounds was restricted in 1992. The management regulations seems to have influenced the use of Sjodalen for camping in several ways. The number of campers using the area has decreased. The user composition seems to have changed, with new campers in the area after the regulation being more tolerant of human influence on the natural environment than the campers before the regulations. In addition, a considerable proportion of the existing users ceased to stay overnight in Sjodalen, totally or partly due to the regulations. The behavioral response among existing users is related both to environmental preferences and place attachment. Implications for management and future research studies on impact assessment in general, and displacement specifically, are discussed.KEY WORDS: Outdoor recreation; Management regulations; Behavioral response; Displacement, Place attachment     

A case study of promoting CH4 discharge and preventing coal & gas outburst accidents by using cross-layer liquid injection technology

To solve the problem of gas extraction in coal bodies with the outburst risk, the cross-layer drilling fluid injection technology for protecting rock pillars is adopted to promote gas extraction. We combined theoretical calculations, laboratory experiments, and field tests to analyze the degree of fissure development in different parts of the coal body. We also determined the liquid injection parameters and negative extraction pressures. The CH₄ extraction effects of three stages before, during, and after liquid injection was compared. The results show that the possibility of coal outbursts in different parts is reduced by 58%∼70% by using liquid injection and pumping technology. The peak value of CH₄ pure flow in the main pipe is increased by 1.5–2.8 times, and the average value is increased by 1.8–2.6 times. The peak value of gas concentration at the orifice of the extraction hole is increased by 1.6–3.5 times, and the average value is increased by 1.6–4 times. Liquid injection to promote extraction greatly improves the gas extraction efficiency in coal bodies, which is of great significance to reducing cost, shortening the construction period, and ensuring safe production, and providing a reference for similar engineering construction.     

Experimental research on displacing coal bed methane with supercritical CO2

The high-gas and low-permeability are the common problems of China coal mine, which restrain the mining of coal-seam gas resources safely and efficiently. Hence, to solve the problem of low permeability of coal seam, an experimental system was set up and experimental research was conducted to investigate the effect of the displacement of methane by injecting supercritical CO₂ into coal samples. The experimental results indicated that, the extraction effect of supercritical CO₂ changes the coal’s porosity, and broadens the seepage channel for methane. Thus, the methane could be desorbed effectively from the coal matrix, and flow through more cracks at higher speed.     

Numerical investigation of flow erosion and flow induced displacement of gas well relief line

High-pressure particle-laden gas flow should be discharged through relief line of gas well timely to ensure safe test and exploitation. Erosion and vibration usually take place on the bend in relief lines, bringing a potential safety hazard to field operation. The majority of this paper investigates the factors affecting the erosion of bend and displacement of relief line in the downstream of bend using the computational fluid dynamics (CFD) methodology. A three-dimensional elbow pipe is selected as computational domain in this investigation. The kinematics and trajectory of discrete solid particles and liquid droplets are described by discrete phase model (DPM) while the hydrodynamic characteristics of continuous phase are obtained based on Reynolds-Averaged-Navier-Stokes (RANS) equations. An empirical erosion model is employed to predict the erosion rate of bend, and a fluid–structure interaction (FSI) model is adopted to calculate the displacement of relief line. The effects of types of multiphase flow (such as gas–solid two-phase flow and gas–liquid–solid three-phase flow), inlet flow rate and pipe diameter on erosion and displacement are discussed. The results show that large displacement and severe erosion present with large inlet flow rate in minor diameter pipe. The increase in liquid droplet content has less effect on flow erosion than that by the same increase in sand particle content.     

岩层移动角选取的神经网络方法研究

岩层移动角是进行各类保护煤柱设计时的关键性参数 ,涉及地表建 (构 )筑物的安全。在综合分析影响岩层移动角因素的基础上 ,采用人工神经网络方法建立岩层移动角选取的模型。该模型采用改进的BP算法 ,运用我国典型的地表移动观测站资料作为学习训练样本和测试样本 ,对模型的计算结果与实测值进行了对比分析。分析结果表明 :用人工神经网络方法求算岩层移动角考虑的因素更为全面 ,结果更接近于实际。笔者为岩层移动角的理论计算探索出了一种新的方法。     

Investigation of exhaled pollutant distribution in the breathing microenvironment in a displacement ventilated room with indoor air stability conditions

This study experimentally studied the dispersion of exhaled pollutant in the breathing microenvironment (BM) in a room equipped with a displacement ventilation (DV) system and indoor air stability conditions (i.e., stable and unstable conditions). The vertical temperature differences and the carbon dioxide (CO₂) concentration in the BM were measured. Results show that when DV is combined with the stable condition (DS), pollutant tends to accumulate in the BM, leading to a high pollutant concentration in this region. Whereas, when DV is combined with the unstable condition (DU), pollutant diffuses to a relatively wider area beyond the BM, thus the pollutant concentration in the BM is substantially reduced. Moreover, increasing the flow rate can reduce the pollutant concentration in the BM of the DS but yields little difference of the DU. In addition, personal exposure intensity increases with time, and the DS has a relatively higher increase rate than DU. The results suggest that indoor air stability will affect the performance of DV systems. DS will lead to a higher health risk for people when they stay in the indoor environment with pollutant sources, and DU is recommended for minimizing pollutant level in the BM in order to reduce the pollutant concentration and providing better air environments for the occupants.