面向对象的河口滩涂冲淤变化遥感分析

河口滩涂位于江河入海口前沿,其岸线受江河上游来水来沙、海水潮汐动力和人为因素影响处于不断变化中。针对遥感人工目视解译判读出岸线进行冲淤变化分析方法的不足,提出了面向对象的岸线遥感识别提取方法,阐述了整个遥感迭代识别提取过程。以长江河口崇明东滩为实验区,选取长江口1990年12月4日、1995年4月6日、2000年6月14日和2005年11月27日4个时相的陆地卫星TM/ETM+遥感影像,对其进行基于面向对象的识别处理,直接提取相应年份的岸线和滩涂陆域多边形,对4个年份的陆域多边形进行空间叠加分析,得到了崇明东滩自1990年以来15年间的冲淤空间变化。应用表明面向对象的遥感分析识别技术在河口滩涂冲淤变化分析中具有准确、快速、简便的特点。     

Forecasting the Spread of Invasive Rainbow Smelt in the Laurentian Great Lakes Region of North America

Abstract:  Rainbow smelt ( Osmerus mordax ) have invaded many North American lakes, often resulting in the extirpation of native fish populations. Yet, their invasion is incipient and provides the rationale for identifying ecosystems likely to be invaded and where management and prevention efforts should be focused. To predict smelt presence and absence, we constructed a classification-tree model based on habitat data from 354 lakes in the native range for smelt in southern Maine. Maximum lake depth, lake area, and Secchi depth (surrogate measure of lake productivity) were the most important predictors. We then used our model to identify lakes vulnerable to invasion in three regions outside the smelt's native range: northern Maine (52 of 244 lakes in the non-native range), Ontario (4447 of 8110), and Wisconsin (553 of 5164). We further identified a subset of lakes with a strong potential for impact (potential–impact lakes) based on the presence of fish species that are affected by rainbow smelt. Ninety-four percent of vulnerable lakes in the non-native range in Maine are also potential–impact lakes, as are 94% and 58% of Ontario and Wisconsin's vulnerable lakes, respectively. Our modeling approach can be applied to other invaders and regions to identify invasion-prone ecosystems, thus aiding in the management of invasive species and the efficient allocation of invasive species mitigation and prevention resources.     

WATERSHED CLASSIFICATION USING CANONICAL CORRESPONDENCE ANALYSIS AND CLUSTERING TECHNIQUES: A CAUTIONARY NOTE1

ABSTRACT: Watershed classification using multivariate techniques requires the incorporation of continuous datasets representing controlling environmental variables. Often, out of convenience and availability rather than importance to the structure of the system being modeled, the environmental data used originate from a variety of sources and scales. To demonstrate the importance of appropriate environmental data selection, classifications of six‐digit hydrologic units (1:24,000) across selected geographic areas within the Interior Columbia River Basin were produced. Canonical correspondence analysis was used to select and test environmental variables important in predicting Rosgen stream types and valley bottom classes. Then, hierarchical agglomerative clustering was used to group (classify) watersheds based on these variables. Statistically significant results were derived from the use of organized classification data with presumed predictive relationships to watershed properties, and a random distribution of environmental variables from the same datasets provided similar results. The results contained herein demonstrate that these analysis techniques do not necessarily select meaningful variables from a broad spectrum of data and that significant results are easily generated from randomly associated data. It is suggested that classifications produced using these multivariate techniques, especially when using multi‐scale data or data of unknown significance, are subject to invalid inferences and should be used with caution.     

CLIMATE CHANGE AND EXTRATROPICAL STORMINESS IN THE UNITED STATES: AN ASSESSMENT1

ABSTRACT: Climate change due to enrichment of the atmosphere with carbon dioxide is projected to change the circulation of the atmosphere, increase its moisture content, warm the surface layers, and increase precipitation. Extratropical storms are the intermediate agent in mid-latitudes between changes in the circulation of the atmosphere and surface water resources. The climatology of extratropical storms for the period 1885–1996 is presented, and major changes in storminess are detected across much of North America. General Circulation Model (GCM) projections of storm frequency and storm track are found to have little in common with the observed pattern of storms and evidence no systematic changes in response to an enrichment of the atmosphere with carbon dioxide.     

Critical Evaluation of How the Rosgen Classification and Associated “Natural Channel Design” Methods Fail to Integrate and Quantify Fluvial Processes and Channel Response1

Abstract: Over the past 10 years the Rosgen classification system and its associated methods of “natural channel design” have become synonymous to some with the term “stream restoration” and the science of fluvial geomorphology. Since the mid 1990s, this classification approach has become widely adopted by governmental agencies, particularly those funding restoration projects. The purposes of this article are to present a critical review, highlight inconsistencies and identify technical problems of Rosgen’s “natural channel design” approach to stream restoration. This paper’s primary thesis is that alluvial streams are open systems that adjust to altered inputs of energy and materials, and that a form‐based system largely ignores this critical component. Problems with the use of the classification are encountered with identifying bankfull dimensions, particularly in incising channels and with the mixing of bed and bank sediment into a single population. Its use for engineering design and restoration may be flawed by ignoring some processes governed by force and resistance, and the imbalance between sediment supply and transporting power in unstable systems. An example of how C5 channels composed of different bank sediments adjust differently and to different equilibrium morphologies in response to an identical disturbance is shown. This contradicts the fundamental underpinning of “natural channel design” and the “reference‐reach approach.” The Rosgen classification is probably best applied as a communication tool to describe channel form but, in combination with “natural channel design” techniques, are not diagnostic of how to mitigate channel instability or predict equilibrium morphologies. For this, physically based, mechanistic approaches that rely on quantifying the driving and resisting forces that control active processes and ultimate channel morphology are better suited as the physics of erosion, transport, and deposition are the same regardless of the hydro‐physiographic province or stream type because of the uniformity of physical laws.     

Quality of groundwater contaminated by leachates from seven Polish landfills – chemical and ecotoxicological classifications

The article presents the results of screening research on acute toxicity of groundwater contaminated by leachates to the bacterium Vibrio fischeri (ToxAlert 100® test) and crustacean Daphnia magna (Daphtoxkit F? magna test according to PN-EN ISO 6341), as well as on chronic toxicity to D. magna (test according to ISO 10706). The groundwater samples were taken from seven large city landfills in the Pomeranian province (Poland), which were open before 1990 and designed without proper attention to being leak-tight. Due to the lack of either European or Polish classification of ecotoxicological qualities of surface and underground waters, an attempt was made to evaluate the ecotoxicological quality of the examined waters on the basis of the Helsinki Committee's recommendations for industrial effluents, the classification of sediment according to Krebs (Krebs F. The pT-value as a classification index in aquatic toxicology. GIT Edition Umweltanalytik-Umweltschutz 1988;1:57–63) and the classification system of toxicity levels for natural waters and sewers, recently proposed by Persoone et al. (Persoone G, Marsalek B, Blinova, I, Törökne A, Zarina D, Manusadzianas L, Nalecz-Jawecki G, Tofan L, Stepanova N, Tothova L, Kolar B. A practical and user-friendly toxicity classification system with microbiotests for natural waters and wastewaters. Environ. Toxicol. 2003;18 (6):395-402).     

气升循环分体式膜生物反应器污水处理与回用技术

介绍了一种新型膜生物反应器———气升循环分体式膜生物反应器污水处理和再生回用技术。该技术膜单元和生物单元分置 ,生物单元和膜单元间的水力循环利用气升动力 ,无需循环水泵 ,系统具有维护方便、运行能耗低和建设投资省等特点。采用该技术处理生活污水和厕所污水 ,处理水质可达到建设部颁布的《生活杂用水水质标准》(CJ2 5 1 89)。给出了该技术处理生活污水和厕所污水的工程建设投资指标、水处理成本和水处理能耗指标 ,处理能耗 0 6～ 0 8kWh/m3 。该新型膜生物反应器污水再生回用技术具有良好的市场应用前景 ,技术经济可行。     

用于普通小球藻固碳的气升式内环流平板光生物反应器设计参数优化

为构建适宜普通小球藻快速生长及生物固碳的内环流气升式平板光生物反应器,通过正交实验方法考察了表观气速(SGV)、高径比(H/D)、降流区与升流区的面积比(Ad/Ar)等设计参数对传递特性变量(气含率、液相循环流速、体积传质系数)和微藻固碳速率的影响。结果表明,SGV对微藻固碳速率影响最为显著,Ad/Ar次之,H/D最小。最适设计参数为SGV=0.3 vvm,Ad/Ar=3:1,H/D=6:1。SGV主要通过提高了藻液的气含率而对微藻固碳起到积极作用;微藻生长受多重因素影响,仅仅考察体积传质系数对反应器性能的提升并不全面,气含率的提高对微藻高效固碳更为有利。     

气体循环条件下等离子体催化氧化吸附态的苯和甲苯

在气体循环条件下,以MnOx-AgOx/γ-Al2O3、CoOx-CeOx/γ-Al2O3为吸附剂兼催化剂,研究了低温等离子体催化氧化吸附态的苯和甲苯,并对催化剂进行了BET和XRD表征。结果表明：气体循环条件下等离子体催化氧化技术同样适用于吸附态的双组分苯与甲苯的降解,并且COx产率和CO2选择性不比降解单组分苯或甲苯时的低。气体循环放电90 min后,与γ-Al2O3相比,引入MnOx-AgOx/γ-Al2O3、CoOx-CeOx/γ-Al2O3后,COx产率分别提高了9%、12%;CO2选择性也得到了提高并都接近100%;臭氧浓度分别减少了51%、39%;N2O浓度相应也降低了26%和38%。最后结合实验结果讨论了引入催化剂后反应机理的变化。     

A mesoscale vortex in a small stratified lake

A mesoscale vortex structure in the small stratified Lake Stechlin has been revealed by field experiments with satellite-tracked quasi-lagrangian drifters. The vortex with a radius of about 200 m drifted at 300 m/day along the western bight of the lake with nearly constant rotation speed of 3 cpd. Analysis of kinematical properties of the vortex motion demonstrates solid body character of rotation. Extrapolation of the vortex drift trajectory over the period preceding the observations combined with data on local winds and seiche dynamics has allowed tracing the vortex fate from its generation point. The normal modes analysis of the internal seiching in the lake reveals the vortex generation mechanism to be the interaction of certain seiche modes with local bottom topography and suggests generation of the mesoscale vortices to be the a regular feature of the lake circulation. Analysis of vorticity suggests additional energy supply to rotational flow, possibly from inverse cascading of small-scale turbulent motions—a feature typical for quasi-2D turbulence. The vortices can play an important role in the energy transport from basin-scale motions to small-scale boundary mixing. They can also contribute significantly to the horizontal heterogeneity of phyto- and zooplankton distribution as well as to the transport of dissolved matter such as nutrients between littoral and profundal areas. The topographically generated traveling vortices represent an analog of the synoptic eddies in the Ocean and in the Atmosphere, whereas their role in the lake hydrodynamics is practically unknown.