基于GIS的黄水河流域地下水脆弱性评价研究

从影响地下水脆弱性的因素出发,结合国内外已有的地下水脆弱性影响因素、评价指标和评价标准,根据研究区的具体情况和可获得资料,确定了北方滨海地区地下水脆弱性的影响因素,建立了地下水脆弱性评价DRAMTICH指标体系和评价标准。以黄水河流域为例,进行了地下水脆弱性评价和编图,为当地今后制订地下水资源保护与管理、土地利用及城市规划等政策措施提供决策依据。该方法同样适用于其它类似地区的地下水脆弱性评价。     

A statistical and geographical information system analysis for groundwater intrinsic vulnerability: a validated case study from Sfax–Agareb,Tunisia

The groundwater vulnerability to the pollution assessment was considered as an efficient tool to limit and to control its quantitative and qualitative degradation risks. The DRASTIC high, moderate and low groundwater vulnerability zones of the Sfax–Agareb basin (Tunisia) cover about 10, 29 and 61% of the study area, respectively. The validation of the DRASTIC vulnerability map was undertaken through comparison of areas of high nitrate concentration and their relative vulnerability index. The DRASTIC vulnerability map illustrates a good rate of coincidence between the nitrate concentration ranges and the various vulnerability classes as recognized by statistical analysis. The reliability of the final vulnerability map has been tested, showing a general positive trend relating the mean nitrate concentration in the wells to their relative vulnerability classes (R²=0.88). When correlating the 214 available groundwater nitrate concentrations to the DRASTIC index in these wells location, a significant positive correlation with Cor=0.55 was found.     

A GIS-based DRASTIC model for assessing aquifer vulnerability in Kakamigahara Heights, Gifu Prefecture, central Japan

Vulnerability assessment to delineate areas that are more susceptible to contamination from anthropogenic sources has become an important element for sensible resource management and land use planning. This contribution aims at estimating aquifer vulnerability by applying the DRASTIC model as well as utilizing sensitivity analyses to evaluate the relative importance of the model parameters for aquifer vulnerability in Kakamigahara Heights, Gifu Prefecture central Japan. An additional objective is to demonstrate the combined use of the DRASTIC and geographical information system (GIS) as an effective method for groundwater pollution risk assessment. The DRASTIC model uses seven environmental parameters (Depth to water, net Recharge, Aquifer media, Soil media, Topography, Impact of vadose zone, and hydraulic Conductivity) to characterize the hydrogeological setting and evaluate aquifer vulnerability. The western part of the Kakamigahara aquifer was dominated by "High" vulnerability classes while the eastern part was characterized by "Moderate" vulnerability classes. The elevated north-eastern part of the study area displayed "Low" aquifer vulnerability. The integrated vulnerability map shows the high risk imposed on the eastern part of the Kakamigahara aquifer due to the high pollution potential of intensive vegetable cultivation. The more vulnerable western part of the aquifer is, however, under a lower contamination risk. In Kakamigahara Heights, land use seems to be a better predictor of groundwater contamination by nitrate. Net recharge parameter inflicted the largest impact on the intrinsic vulnerability of the aquifer followed by soil media, topography, vadose zone media, and hydraulic conductivity. Sensitivity analyses indicated that the removal of net recharge, soil media and topography causes large variation in vulnerability index. Moreover, net recharge and hydraulic conductivity were found to be more effective in assessing aquifer vulnerability than assumed by the DRASTIC model. The GIS technique has provided efficient environment for analyses and high capabilities of handling large spatial data.     

Prioritisation of abstraction boreholes at risk from chlorinated solvent contamination on the UK Permo-Triassic Sandstone aquifer using a GIS

A 250 km2 area of the Permo-Triassic Sandstone aquifer in the West Midlands of England, UK, was selected as a test region for the development of a geographic information system (GIS)-based risk assessment methodology that incorporates contaminant source, groundwater vulnerability and groundwater abstraction catchment elements in order to prioritise areas and boreholes potentially at risk from chlorinated solvent pollution on a regional scale. Factors incorporated in the vulnerability assessment include the nature of soils, presence or absence of superficial or glacial deposits, fault density and depth to water table. ARCVIEW GIS was employed with a simple ranking system from which the derived vulnerability assessment index was combined with current chlorinated solvent user industry data and source protection zone components. Results indicate the presence of high-risk areas in urban locations where locally dense distributions of chlorinated solvent user industries combine with high vulnerability aquifers within the catchment of supply boreholes. Ranking of catchment-specific risk reveals the abstraction points under greatest stress. The proposed methodology has applications as a regional-scale initial screening tool to guide site selection for regulatory inspections and assist in prioritising monitoring strategies for existing boreholes. Future developments will provide guidance for locating new urban boreholes in areas of lowest risk.     

Application of DRASTIC and extension theory in the groundwater vulnerability evaluation

Groundwater vulnerability assessment plays a vital role in the utilization and protection of groundwater resources. DRASTIC is one of the most widely used models for groundwater vulnerability assessment. However, the DRASTIC model should be modified based on the local hydrogeological conditions in order to get a relatively accurate result. In this study, Baotou, China was chosen as a case study. The groundwater vulnerability was assessed using DRASTIC at first, but the evaluation results were not consistent with the groundwater quality. So the DRASTIC model was modified based on extension theory and analytic hierarchy process (AHP) method. The extension theory could be used to divide the groundwater vulnerability grades in the DRASTIC model. It is a new attempt to use extension theory and DRASTIC in the assessment of groundwater vulnerability, and the research results show that this method is better for assessing groundwater vulnerability.     

Quantitative assessment of intrinsic groundwater vulnerability to contamination using numerical simulations

Intrinsic vulnerability assessment to groundwater contamination is part of groundwater management in many areas of the world. However, popular assessment methods estimate vulnerability only qualitatively. To enhance vulnerability assessment, an approach for quantitative vulnerability assessment using numerical simulation of water flow and solute transport with transient boundary conditions and new vulnerability indicators are presented in this work. Based on a conceptual model of the unsaturated underground with distinct hydrogeological layers and site specific hydrological characteristics the numerical simulations of water flow and solute transport are applied on each hydrogeological layer with standardized conditions separately. Analysis of the simulation results reveals functional relationships between layer thickness, groundwater recharge and transit time. Based on the first, second and third quartiles of solute mass breakthrough at the lower boundary of the unsaturated zone, and the solute dilution, four vulnerability indicators are extracted. The indicator transit time t₅₀ is the time were 50% of solute mass breakthrough passes the groundwater table. Dilution is referred as maximum solute concentration C_max in the percolation water when entering the groundwater table in relation to the injected mass or solute concentration C₀ at the ground surface. Duration of solute breakthrough is defined as the time period between 25% and 75% (t_25%-t_75%) of total solute mass breakthrough at the groundwater table. The temporal shape of the breakthrough curve is expressed with the quotient (t_25%-t_50%) / (t_25%-t_75%). Results from an application of this new quantitative vulnerability assessment approach, its advantages and disadvantages, and potential benefits for future groundwater management strategies are discussed.     

基于熵权的集对分析方法在地下水脆弱性评价中的应用

针对传统集对分析在评价地下水脆弱性时认为各指标权重相同的缺点,以DRASTIC模型指标体系作为基础,将熵值理论与集对分析相结合,在集对分析中使用熵值法确定权重系数,对地下水脆弱性进行了评价,实现了特性权重随样本数据的动态变化。应用实例表明,该方法评价地下水脆弱性能够充分反映样本数据本身对指标权重的影响,评价结果更加客观、可靠。     

太原市盆地区浅层地下水脆弱性评价

本文从影响地下水脆弱性的因素出发,结合国内外已有的地下水脆弱性影响因素、评价指标和评价标准,根据研究区的具体实际情况和可获得资料,选取影响地下水脆弱性的地下水埋深、含水层净补给量、含水层介质、土壤包气带、地形、包气带介质和水力传导系数7个参数作为评价因子,建立太原市盆地区浅层地下水脆弱性评价DRASTIC指标体系和评价标准。依据标准对其所含的7个参数进行评分,并具体阐述了评分中所应注意的问题,在获得了DRASTIC模型的7个指标在研究区的评分图之后,利用GIS平台空间分析技术将7张评分图叠加,同时对7个指标按照各自的权重取其加权和,这样便得到了太原市盆地区浅层地下水脆弱性分区图,结果表明汾河沿岸和吴家堡工业区地下水脆弱性指数较高,在盆地两侧的黄土台塬区,地下水脆弱性评分为低或极低,评价模型能合理的反映太原市盆地区浅层地下水脆弱性的高低。研究结果可以为太原市土地利用规划、地下水水资源保护规划、地下水水质监测等提供参考,也可以提高公众关于地下水污染的风险意识。     

基于层次分析法的DRASTIC模糊评价方法探讨——以云南曲靖盆地为例

在分析DRASTIC方法的基础上,结合前人研究成果,运用层次分析法构建了二层评价指标体系,并结合多层次模糊评价理论,建立了基于层次分析的DRASTIC二层模糊评价模型,并将该模型应用到曲靖盆地地下水脆弱性评价中。结果表明,该模型评价灵敏度高,更能反映地下水脆弱性的空间连续性,且该模型计算方法较简便,进一步丰富了地下水脆弱性的评价方法。     

Ecological vulnerability analysis: A river basin case study

Assessing and quantifying ecosystem vulnerability is a key issue in site-specific ecotoxicological risk assessment. In this paper, the concept of vulnerability, particularly referred to aquatic ecosystems is defined. Sensitivity to stressors, susceptibility for exposure and recovery capability are described as component of vulnerability of biological communities. The potential for habitat changes must also be considered in ecosystem vulnerability assessment. A procedure based on the application of an ecosystem vulnerability index is proposed. The method allows the assessment of vulnerability of riverine ecosystems to multiple stressors. The procedure is applied to two river systems in northern Italy: River Serio, subject to strong human pressure, and River Trebbia, in semi-natural conditions, as reference system. Macrozoobenthos is chosen as the indicator community. The actual quality of River Serio was evaluated as the result of the multiple stressor pressure on the reference system. Values and limitations of the approach are discussed.     

VLDA模型及其在潜水脆弱性评价中的应用——以新疆焉耆县平原区为例

在地下水脆弱性评价的GOD法和DRASTIC模型的基础上,提出了VLDA模型,其中V为包气带岩性(1ithology of vadose zone)、L为土地利用方式(pattern of land use)、D为地下水埋深(groundwater depth)、A为含水层特征(aquifer characterist...     

城市公共交通优先发展的目标与指标体系研究

讨论了城市公共交通优先发展战略和公交都市建设的核心目标,提出了衡量公交优先发展绩效与公交都市建设成效的公共交通服务质量指标体系和公共交通服务品质指数,以期引导城市公共交通优先发展和公交都市建设回归到"以民为本、乘客至上"的正确理念与轨道上来。     

Predicting the vulnerability of reservoirs to poor water quality and cyanobacterial blooms

Cyanobacterial blooms in drinking water reservoirs present a major ecosystem functioning and human health issue. The ability to predict reservoir vulnerability to these blooms would provide information critical for decision making, hazard prevention and management. We developed a new, comparative index of vulnerability based on simple measures of reservoir and catchment characteristics, rather than water quality data, which were instead used to test the index’s effectiveness. Testing was based on water quality data collected over a number of seasons and years from 15 drinking water reservoirs in subtropical, southeast Queensland. The index correlated significantly and strongly with algal cell densities, including potentially toxic cyanobacteria, as well as with the proportions of cyanobacteria in summer months. The index also performed better than each of the measures of reservoir and catchment characteristics alone, and as such, was able to encapsulate the physical characteristics of subtropical reservoirs, and their catchments, into an effective indicator of the vulnerability to summer blooms. This was further demonstrated by calculating the index for a new reservoir to be built within the study region. Under planned dimensions and land use, a comparatively high level of vulnerability was reached within a few years. However, the index score and the number of years taken to reach a similar level of vulnerability could be reduced simply by decreasing the percentage of grazing land cover via revegetation within the catchment. With climate change, continued river impoundment and the growing demand for potable water, our index has potential decision making benefits when planning future reservoirs to reduce their vulnerability to cyanobacterial blooms.     

基于组合赋权TOPSIS法的区域森林火灾易损性研究

通过对区域森林火灾易损性进行评价,实现控制火灾风险和减轻损失。考虑到森林火灾暴露性程度和灾害应对能力等因素,构建了由暴露性程度、恢复性指标、敏感性指标、灾害应对能力4个准则层和16个指标层构成的区域森林火灾易损性评价指标体系。利用组合赋权TOPSIS法对四川省21个市（州）开展了森林火灾易损性评价,根据评估结果将四川省的森林火灾易损性水平划分为5个等级。     

Ecological vulnerability in risk assessment — A review and perspectives

This paper reviews the application of ecological vulnerability analysis in risk assessment and describes new developments in methodology. For generic non-site-specific assessments (e.g. for the requirements of most European directives on dangerous chemicals) risk is characterised just on the basis of the ratio between an effect indicator and an exposure indicator. However, when the actual risk for a specific ecosystem is desired, the concept of ecological vulnerability may be more appropriate. This calls for a change in thinking, from sensitivity at the organism level to vulnerability at higher organization levels, and thus forms the link from laboratory toxicology to field effects at population, community or ecosystem level. To do so, biological and ecological characteristics of the ecosystems under concern are needed to estimate the ecological vulnerability.In this review we describe different vulnerability analysis methods developed for populations (of a single species), communities (consisting of different populations of species) and ecosystems (community and habitat combined). We also give some examples of methods developed for socio-ecological systems. Aspects that all methods share are the use of expert judgment, the input of stakeholders, ranking and mapping of the results, and the qualitative nature of the results.A new general framework is presented to guide future ecological vulnerability analysis. This framework can be used as part of ecological risk assessment, but also in risk management. We conclude that the further quantification of ecological vulnerability is a valuable contribution to vulnerability assessment.     

Exploring the catchment area of an urban railway station by using transit card data: Case study in Seoul

To enhance transit ridership, Seoul introduced a transfer discount fare scheme that uses an automated fare collection system in Seoul 2004. The transfer discount fare system records all transfer information between rail and buses in transit smartcard data, which enabled us to explore an urban railway station's catchment area. In this study, we examined the geographic distribution of rail-to-bus transfer trips and their characteristics by using transit smartcard data. Mokdong station in Seoul was used as a case study to demonstrate the benefits of data mining for the depiction and easy evaluation of a station's catchment area. The results showed that the average transfer passenger traveled 1.7 km with five bus stops after boarding to access the business district during the morning peak hour. The cumulative distribution of alighting passengers by bus route helped with inferring the shape and size of the urban railway station's catchment area in each direction and depending on the time of day. We found that reliable transfer travel data constitute valuable information for evaluating an urban railway station's catchment area with respect to the type of land use and will help transit agencies with providing better transit services in terms of enhanced accessibility by changing bus headways and routes, as well as land use planners with evaluating transit-oriented development based on the expanded concept of a metro station's catchment area.     

Justice in public transport systems: A comparative study of Auckland,Brisbane, Perth and Vancouver

Although the concept of social justice seems to be ubiquitous in most transportation plans, methods adopted to evaluate transit systems have little engagement with political theories to define justice. Without a proper definition, transport planners will be unable to design transit systems that achieve justice. The present study proposes a combination of sufficientarianism and egalitarianism principles to define justice in transit. Based on this framework 1) access to public transport is a right, 2) public transport should provide a minimum accessibility, 3) public transport should benefit the less well-off groups, and 4) a just distribution has to be spatially evaluated. The framework proposes a method that can be used to measure and compare justice in transit systems. The framework is applied to four case study cities, Auckland, Brisbane, Perth, and Vancouver. The results show that Auckland's transit system performs well relative to the other three case study cities by accounting for people and providing a minimum access to jobs. However, Auckland's transit services fail in the just distribution as it favours more affluent neighbourhoods. This issue is more severe in Brisbane's and Perth's transit systems. Vancouver, on the other hand, provides a better service for low-income neighbourhoods. This study contributes to the field of justice in transit by providing a clearly defined framework which can be adopted to analyse a city's transit system and compare it with other cities. It is expected to assist practitioners in obtaining insights that can inform policy decisions.     

重金属离子和LNAPLs在非饱和土中的运移规律研究

以重金属和轻非水相流体(LNAPLs)为例,介绍了清华大学开展非饱和土中污染物运移规律研究的部分工作成果。利用土工离心机对污染物的运移过程模拟,取样得到污染物的浓度分布特征。同时采用数值分析手段对污染物的长期运移规律和其影响因素进行分析。研究表明:离心模型试验可以有效模拟污染物的运移过程,离心模型试验和数值分析相结合,是研究污染物在非饱和土中运移规律的有效手段。     

Determining transit nodes for potential transit-oriented development: Along the LRT corridor in Addis Ababa,Ethiopia

The aim of transit-oriented development (TOD) is to create a livable urban environment by improving the integration between land-use and transportation systems. The capital city of Ethiopia, Addis Ababa, aims to promote a sustainable transportation system by launching its first light rail transit (LRT) network to control the current pattern of increased congestion and the need for mass transport. Planning for TOD around existing transit stations helps achieve improved transit choice and encourages local economic development. Therefore, this article proposes a methodology to quantitatively measure the existing TOD in terms of a TOD index within the walkable distance of transit nodes by measuring the criteria that define TOD levels. The TOD index is calculated for areas of 22 stations on the East-West LRT line of Addis Ababa. Depending on the value of the TOD index, certain stations are identified to have a potential TOD but poor transit accessibility. With these results, the recommendation to improve TOD planning can become accurate for each station, depending on its relevant factors. Such results also help identify each station's potential for TOD planning and its improvements toward future local developments.