Experiments on vertical transverse mixing in a large-scale heterogeneous model aquifer

Vertical transverse mixing is known to be a controlling factor in natural attenuation of extended biodegradable plumes originating from continuously emitting sources. We perform conservative and reactive tracer tests in a quasi two-dimensional 14 m long sand box in order to quantify vertical mixing in heterogeneous media. The filling mimics natural sediments including a distribution of different hydro-facies, made of different sand mixtures, and micro-structures within the sand lenses. We quantify the concentration distribution of the conservative tracer by the analysis of digital images taken at steady state during the tracer-dye experiment. Heterogeneity causes plume meandering, leading to distorted concentration profiles. Without knowledge about the velocity distribution, it is not possible to determine meaningful vertical dispersion coefficients from the concentration profiles. Using the stream-line pattern resulting from an inverse model of previous experiments in the sand box, we can correct for the plume meandering. The resulting vertical dispersion coefficient is approximately approximately 4 x 10(-)(9) m(2)/s. We observe no distinct increase in the vertical dispersion coefficient with increasing travel distance, indicating that heterogeneity has hardly any impact on vertical transverse mixing. In the reactive tracer test, we continuously inject an alkaline solution over a certain height into the domain that is occupied otherwise by an acidic solution. The outline of the alkaline plume is visualized by adding a pH indicator into both solutions. From the height and length of the reactive plume, we estimate a transverse dispersion coefficient of approximately 3 x 10(-)(9) m(2)/s. Overall, the vertical transverse dispersion coefficients are less than an order of magnitude larger than pore diffusion coefficients and hardly increase due to heterogeneity. Thus, we conclude for the assessment of natural attenuation that reactive plumes might become very large if they are controlled by vertical dispersive mixing.     

Development of continental scale multimedia contaminant fate models: integrating GIS

The incentives and approaches for modelling chemical fate at a continental scale are discussed and reviewed. It is suggested that a multi-media model consisting of some 20-30 regions, each of which contains typically seven environmental compartments represents a reasonable compromise between the issues of the need for detailed resolution, avoidance of excessive data demands and inherent complexity and transparency. Strategies adopted in compiling the Berkley-Trent (BETR) model for North America are discussed and used to illustrate the issues of selecting appropriate number and nature of segments, treatment of air and water flows and the acquisition of environmental data. It is suggested that GIS software can play a valuable role in gathering and processing such data and in the display and interpretation of the results of the model assessment. The BETR model will be a useful tool for describing the nature of persistence and long-range transport of chemicals of concern in the North American environment.     

影像融合技术在滩涂湿地植被分类中的应用

选择上海崇明东滩鸟类自然保护区的盐沼植被为对象,利用该地区2004年TM多光谱影像与同期SPOT5全色影像进行多种规则的融合,通过计算信息熵、均值、标准差、平均梯度、偏差指数、相关系数和均方根差7项指标,评价选取光谱信息较丰富、空间信息更清晰的融合影像.在此基础上,利用该融合影像进行植被分类,得到滩涂地区典型植被、光滩和水体等专题分类影像及其信息,并利用实地观测的134个样区进行比较验证.研究结果表明:相对于融合前的TM影像,利用Wavelet +IHS方法融合后的图像数据能很好地保留TM影像的多光谱信息,同时增加了其空间分辨率.融合技术可以充分利用各类遥感影像的空间和光谱信息,有效提高海岸带资源调查与监测的精度.     

含能材料反应釜温度模型仿真辨识

目的验证一种基于遗忘因子最小二乘法(FFRLS)的含能材料反应釜温度预测模型辨识方法的正确性和有效性。方法首先利用基于机理建模方法对系统模型进行分段处理,并得到其具体结构,然后结合历史数据,利用FFRLS对系统模型参数进行辨识,最后得到含能材料反应釜温度仿真模型。结果在Matlab仿真平台上对该方法的正确性和有效性进行验证,模型参数慢时变状态下该方法辨识参数的模型参数均方根误差(RMSE)皆小于10%,模型参数突变状态下,参数RMSE最小为5.89%,最大为18.69%。结论该方法能准确、有效地对含能材料反应釜温度模型进行辨识。     

Development of rapid,cost effective coral survey techniques: tools for management and conservation planning

Coral reefs are highly dynamic and productive marine ecosystems, providing habitat and refuge for an enormous number of species including fish, invertebrates and algae. With increased anthropogenic pressures and global climate change, many coral reefs are rapidly declining. Currently, there is limited knowledge on condition and community assemblage composition of shallow fringing coral reefs along the south-eastern coast of Queensland, Australia. With increased demand to determine existence of coastal fringing reefs by National Regional Management groups, a rapid cost effective method to determine reef composition and condition was required. The aim of this study was to determine the benthic structure and extent of two small coastal fringing reefs (Hummock Hill Reef and Stringers Reef) along the Southern Great Barrier Reef. Reef substrate assessments were carried out using a rapid assessment technique and a Point Intercept Method (PIM). The data were analysed and classified using a Geographic Information System (GIS). Percent substrate cover was calculated using a visual basic image analysis program. The Point intercept method showed higher accuracy over the rapid assessment technique (up to 15–40% difference) and was thus deemed a more suitable classification tool for reefs with high structural complexity and heterogeneity. This study focused on piloting a rapid, cost effective Point Intercept Technique using random point count methodology to document coral benthic habitat and extent over a commonly used rapid assessment method as a tool for reef coastal management and conservation. The two techniques were compared and substrate classification success, limitations and errors were discussed.     

National,regional and local attitudes towards climate change: identifying appropriate target audiences for communications

A government-funded scheme, the UK Climate Change Communications Initiative (UKCCCI), has provided money for organisations to deliver projects that attempt to impact positively on people's attitudes towards climate change. This devolution of communications is a relatively novel approach after previous centralised campaigns. This paper considers what size of target audience is most appropriate for attitude change initiatives. It compares data from a regional UKCCCI project aimed at residents of two counties with a nationally representative dataset. Regional data are also analysed to see if there are differences in attitudes within the two-counties target audience. The study suggests that attitude change interventions must strike a balance between personalisation of information and the higher cost of targeting smaller groups with more specific material.     

Comparing the utility of image algebra operations for characterizing landscape changes: the case of the Mediterranean coast

The aim of this study is to compare various image algebra procedures for their efficiency in locating and identifying different types of landscape changes on the margin of a Mediterranean coastal plain, Cukurova, Turkey. Image differencing and ratioing were applied to the reflective bands of Landsat TM datasets acquired in 1984 and 2006. Normalized Difference Vegetation index (NDVI) and Principal Component Analysis (PCA) differencing were also applied. The resulting images were tested for their capacity to detect nine change phenomena, which were a priori defined in a three-level classification scheme. These change phenomena included agricultural encroachment, sand dune afforestation, coastline changes and removal/expansion of reed beds. The percentage overall accuracies of different algebra products for each phenomenon were calculated and compared. The results showed that some of the changes such as sand dune afforestation and reed bed expansion were detected with accuracies varying between 85 and 97% by the majority of the algebra operations, while some other changes such as logging could only be detected by mid-infrared (MIR) ratioing. For optimizing change detection in similar coastal landscapes, underlying causes of these changes were discussed and the guidelines for selecting band and algebra operations were provided.     

Influence of COM-peptides/proteins on the properties of flocs formed at different shear rates

Coagulation followed by floc separation is a key process for the removal of algal organic matter(AOM) in water treatment. Besides optimizing coagulation parameters,knowledge of the properties of AOM-flocs is essential to maximizing AOM removal.However, the impact of AOM on the floc properties remains unclear. This study investigated how peptides/proteins derived from the cellular organic matter(COM) of the cyanobacterium Microcystis aeruginosa influenced the size, structure, and shape of flocs formed at different shear rates(G). Flocs formed by kaolinite, COM-peptides/proteins and a mixture of the same were studied, and the effect of intermolecular interactions between floc components on floc properties was assessed. The coagulation experiments were performed in a Taylor–Couette reactor, with aluminum(Al) or ferric sulphate(Fe) utilized as coagulants. Image analysis was performed to gauge floc size and obtain data on fractal dimension. It was found that floc properties were affected by the presence of the COM-peptides/proteins and the coagulant used. COM-peptides/proteins increased floc size and porosity and widened floc size distributions. The Fe coagulant produced larger and less compact flocs than Al coagulant. Moreover, the decrease in floc size that occurred in parallel with increase in shear rate was not smooth in progress. A rapid change for the kaolinite-coagulant suspension and two rapid changes for the suspensions containing COM were observed. These were attributed to various intermolecular interactions between floc components participating in coagulation at different G. Based on the results obtained, shear rates suitable for efficient separation of flocs containing COM were suggested.     

基于偏最小二乘的絮体图像信息与水质的相关性

针对污水处理运行过程COD、BOD5、TN和TP实时测量的问题,提出一种基于絮体形态参数的偏最小二乘法模型.采用图像分析技术对污泥絮体形态特征进行提取,基于相关性从提取的形态参数和试验期间的运行参数中选择模型的输入变量,通过偏最小二乘法建立输入变量与4个水质指标的预测关系模型.结果表明,COD、BOD5、TN、TP的交叉有效性系数分别为0.736、0.682、0.839、0.618,絮体形态参数与水质指标有明显的相关性,可用于预测出水水质.     

地震预报与活断层分段

文章回顾分析了地震预报的经验与问题,对地震短期预报需进行新的探索与研讨,才能更快地前进。文章重点论述了地震预报和地震危险性评估方面有关的断层分段性问题。如何在众多的活断层上确定近期可能发生强震的地段,是地震预报中突出的重要问题之一。有关活断层分段性问题是近年来十分引人注目的课题。段是断层的破裂单元,断层的分段就是对断层进行独立的破裂单元的划分。断层分段有4种,当前讨论的主要是活断层破裂分段。