沈阳沈抚灌区上游土壤重金属镉和铬的现状及潜在生态风险评价

为调查沈抚灌区停灌10多年土壤环境质量状况,在沈阳沈抚灌区上游10个行政村布设了50个取样点,分析测定了土壤重金属镉和铬的含量,并对其进行评价.分析结果表明,有4个行政村土壤重金属镉和3个行政村土壤重金属铬超出辽宁省土壤环境背景值标准,但均未超出国家二级标准,说明沈抚灌区灌溉没有给采样区域土壤带来重金属镉和铬污染,但已有重金属富集.土壤重金属镉和铬变异系数在10%～100%之间,说明土壤扰动性较大.按照辽宁省土壤环境背景值标准进行单项污染指数和内梅罗综合污染指数以及潜在生态风险评价表明:重金属镉具有污染风险,存在着一定的生态风险.重金属铬一般无污染风险,生态风险较小.     

永城矿区土壤重金属污染评价研究

将永城矿区所在的永城市1994.4 km2土地面积按7 km×7 km网格均匀分为41个采样点,调查表层土壤Cu、zn、Pb、Cd、Ni、Cr、As和Hg 8种重金属的含量,利用数据统计方法进行数据处理;查清矿区土壤环境背景值,采用背景值、地质累积指数和标准对比评价方法对永城市土壤重金属元素污染进行评价,以此判断重金属...     

改进BP算法在城市土壤环境质量评价模型的应用

首先采用随机函数生成训练样本,并利用"比例压缩法"进行预处理;而后采用"试错法"确定隐含层神经元数,最终建立了结构为7∶8∶1的BPANN的土壤环境质量评价模型,并采用Matlab6.0进行模拟计算。模型检验结果表明:所建模型的拟合精度、检验精度以及实际评价效果均较好,能够比较客观、准确地对城市土壤环境质量进行评价。对长春市城市表层土壤的评价结果表明,其总体环境质量较好,约81%的土壤面积符合国家一级土壤标准,但局部重金属污染不容忽视,应注意控制重金属污染物排放,以保证土壤资源的可持续利用。     

天津湿地土壤重金属污染对比分析研究

对天津大黄堡、七里海、团泊洼和北大港湿地的土壤重金属含量进行监测,采用天津市土壤背景值和我国《土壤环境质量标准》一、二级标准作为评价考察区土壤环境质量分级标准,对考察区湿地土壤重金属环境质量进行了评价,并对湿地土壤的重金属污染状况进行了对比分析。     

基于Monte-Carlo模拟的土壤环境重金属污染评价法与实例研究

综合分析了现行确定性土壤环境质量评价中的不足,将Monte-Carlo模拟引入地累积指数模型中,并进一步通过数据的挖掘和对土壤中各重金属的生态风险差异的考量,构建了基于不确定性理论的土壤环境质量评价法.将所建方法应用于实例区域,分别构建重金属的实测含量参数和其对应背景值参数的概率分布模型,设定模拟中最大实验量为1 000,置信区间为95%,抽样方法为拉丁超立方(Latin hypercube sampling),得到基于不确定性理论的土壤环境质量评价结果:评价区域土壤中各重金属的污染排序为Cd>Ni>Zn>Cu>Cr,其中,Cd隶属于严重污染等级的概率高达98.1%;Ni和Zn有着明显的空间分布差异,并且属于严重污染的概率也分别达84.5%和87%;Cr和Cu的污染等级相对较低.而后,将所得结果与现行的确定性模型评价结果进行了对比分析,结果表明:所建基于不确定性的评价模型具有更好的评级分辨力,并可更全面、真实地表征该区域土壤重金属的污染特征和概率风险水平.     

基于灰色关联度的土壤环境重金属污染综合评价法

考虑到依据现行土壤环境质量标准(GB15618-1995)的土壤污染评价过程中存在较大的不确定性,将灰色理论引入土壤环境重金属的污染评价中,提出了基于灰色关联度的土壤环境重金属污染综合评价法.将灰色综合评价法应用于现实的案例土壤重金属的污染评价中,结果表明案例区域土壤重金属的8个采样点中只有S1为Ⅲ类土壤,其它样点均为Ⅰ类土壤.灰色综合评价法减少了在土壤污染综合评价中的主观人为因素,并可同时表征同一采样点不同级别和同一级别不同样点之间的土壤环境质量差异,并且在实例研究中发现其可提高预算的有效使用率,是一种可行的评价方法.     

临钢降尘重金属含量及风险评价

在2008年4月～2009年3月对临钢降尘样品进行采集,利用AAS nov AA400原子吸收光谱仪对降尘中重金属元素全量以及溶于水和弱酸中的重金属含量进行了测定与分析.结果表明,各采样点降尘中的Pb含量平均是当地土壤环境背景值的9倍之多,最高达11倍以上,其次Zn、Cd、Mn含量也都超过全球平均含量及当地土壤环境背景值;本次所监测的重金属都能不同程度的溶于水和弱酸中,临汾市的降雨多呈弱酸性,临钢降尘中的重金属可能随着雨水进入土壤,从而对土壤等环境造成污染.     

土壤环境基准的研究现状及展望

土壤环境基准的制修订是一项紧迫而艰巨的任务,它是土壤环境标准修订的基础及科学依据.阐述了土壤环境基准的内涵及分类,综述了发达国家土壤环境基准的研究进展,对我国土壤环境基准的研究现状进行了概述.我国现有的关于土壤环境基准的研究主要是基于土壤环境污染物的背景调查和通过土壤动物及植物的毒性实验而获得的生态毒理学数据.根据现有研究的不足,提出了在研究土壤环境基准时,应将土壤与各个介质关联起来,除了关注土壤生物安全、保障土壤生态安全外,还应综合考虑土壤污染对大气环境、地表径流及地下水的影响.在此基础上,对我国土壤环境基准今后的研究方向进行了展望,以制定满足我国实际需要、适用于我国各地区的使用的科学合理的土壤环境基准值,更好地指导我国土壤环境标准的制定及管理和决策.     

地质累积指数法在义马矿区土壤重金属及氟污染评价中的应用

利用多目标地球化学调查方法,在野外调查、大面积系统性采集土壤样品、测成分析、数理统计、查清矿区土壤环境背景值的基础上,应用地质累积指数法对义马矿区成土过程相同的义马和陕渑煤田土壤中Cr、As、Hg、Pb、Cd和F的污染进行评价,并与采用国家<土壤环境质量标准>为基准的标准对比评价结果进行对比研究.结果表明:矿区土壤中A...     

河南省土壤环境监测能力建设机制研究

河南省是国家粮食生产大省,是国家划定的粮食生产核心区,土壤环境质量是粮食生产能力、粮食生产安全的重要保障,土壤环境监测能力是研判土壤环境质量的决定基础,建立健全我省土壤环境监测能力建设机制,保障农产品质量安全意义重大。本文就该省的监测能力建设机制方面提出几点建议。     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

Perspherical Approaches for Electrons in Atoms and Charged Excitons in Quantum Wells

Instead of following Fock’s expansion,we solve the Schrodinger equation for some quantum mechanical manybody systems such as electrons in atoms and charged excitons in quantum wells in a similar way in hyperspherical coordinates by expanding the wave functions into orthonormal complete basis sets of the hyperspherical hannonics(HHs)of hyperangles and generalized Laguerre polynomials(GLPs)of the hyperradius.This leads the equation to     

Advances in broadband wireless communications under high-mobility scenarios

Future mobile communication systems aim at providing very high data transmission rates, even in high-mobility scenarios such as high-speed wheel-track trains, maglev trains, highway vehicles, airplanes, guided missiles or spacecraft. A particularly important commercial application is the strong and increasing worldwide demand for high- speed broadband wireless communications （up to 574.8 km/ h test speeds or 380 km/h commercial speeds） in railways, providing data, voice and video services for applications such as onboard entertainment services to passengers, train control, train dispatch, train sensor status handling and sur- veillance. In such high-mobility scenarios, there are a number of communication challenges, including fast hand- over, location updating, high-speed channel modeling, estimation and equalization, anti-Doppler spreading tech- niques, fast power control, and dedicated network architec- ture. Because signal transmission in very high-speed scenarios will inevitably experience serious deterioration, it is imperative to develop key broadband mobile communi- cation techniques for such high-speed vehicles.     

Wuhan University Journal of Natural Sciences TOTAL CONTENTS

<正>~~     

海南岛地体及其毗邻陆缘晚中生代—新生代古地磁研究和构造演化

本文叙述了对海南岛及其毗邻大陆边缘白垩纪到第四纪地层岩石进行古地磁研究的全部工作过程。通过分析岩石中剩余磁矢量的磁偏角及磁倾角的变化,提出海南岛白垩纪以来经历的构造演化模式如下:早期伴随顺时针旋转而向南迁移,后期伴随逆时针转动并向北运移。联系该地区及邻区的地质、地球物理资料,对海南岛上述的构造地体运动提出以下认识:北部湾内早期有一拉张作用,主要是该作用使湾内地壳显著伸长减薄,形成北部湾盆地。从而导致了海南岛的早期构造运动,而海南岛后期的构造运动则主要是受南海海底扩张的影响。海南地体运动规律的阐明对于了解北部湾油气盆地的形成演化有重要的理论和实际意义。     

Scale-based spatial data model for GIS

Being the primary media of geographical information and the elementary objects manipulated, almost all of maps adopt the layer-based model to represent geographic information in the existent GIS. However, it is difficult to extend the map represented in layer-based model. Furthermore, in Web-Based GIS, It is slow to transmit the spatial data for map viewing. In this paper, for solving the questions above, we have proposed a new method for representing the spatial data. That is scale-based model. In this model we represent maps in three levels: scale-view, block, and spatial object, and organize the maps in a set of map layers, named Scale-View, which associates some given scales.Lastly, a prototype Web-Based GIS using the proposed spatial data representation is described briefly.     

Exciton Seebeck in Molecular Systems

Various applications relevant to the exciton dynamics,such as the organic solar cell,the large-area organic light-emitting diodes and the thermoelectricity,are operating under temperature gradient.The potential abnormal behavior of the exicton dynamics driven by the temperature difference may affect the efficiency and performance of the corresponding devices.In the above situations,the exciton dynamics under temperature difference is mixed with     

Achieving Unusual States of Matter Under High Pressure

The elongation method,originally proposed by Imamura was further developed for many years in our group.As a method towards O(N)with high efficiency and high accuracy for any dimensional systems.This treatment designed for one-dimensional(ID)polymers is now available for three-dimensional(3D)systems,but geometry optimization is now possible only for 1D-systems.As an approach toward post-Hartree-Fock,it was also extended to