Topographic predictors of susceptibility to alluvial fan flooding,Southern Apennines   总被引：2，自引：0，他引：2  

N. Santangelo  J. Daunis‐i‐Estadella  G. Di Crescenzo  V. Di Donato  P. I. Faillace  J. A. Martín‐Fernández  P. Romano  A. Santo  V. Scorpio 《地球表面变化过程与地形》2012,37(8):803-817

The flooding susceptibility of alluvial fans in the Southern Apennines has long been neglected. To partly address this oversight, we focus on the region of Campania which contains highly urbanized piedmont areas particularly vulnerable to flooding. Our findings are based on stratigraphic analysis of the fans and morphometric analysis of the basin‐fan systems. Using geomorphological analysis we recognized active alluvial fans while stratigraphic analysis together with statistical analysis of the morphometric variables was used to classify the fans in terms of the transport process involved. The results indicate that in the geological context examined, the best discrimination between debris flow (Df) and water flood (Wf) processes is achieved by means of two related variables, one for the basin (feeder channel inclination, Cg) and one for the fan (fan length, Fl). The probability that an unclassified fan belongs to group Wf is computed by applying a logistic function in which a P value exceeding 0.5 indicates that a basin/fan system belongs to group Wf. This important result led to the classification of the entire basin/fan system data. As regards process intensity, debris flow‐dominated fans are susceptible to the occurrence of flows with high viscosity and hence subject to more severe events than water flood‐dominated fans. Bearing this in mind, the data gathered in this study allow us to detect where alluvial fan flooding might occur and give information on the different degrees of susceptibility at a regional scale. Regrettably, urban development in recent decades has failed to take the presence of such alluvial fans into account due to the long recurrence time (50–100 years) between floods. This paper outlines the distribution of such susceptibility scenarios throughout the region, thereby constituting an initial step to implementing alluvial fan flooding control and mitigation. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Environmental change,hydromorphological reference conditions and the restoration of Polish Carpathian rivers   总被引：1，自引：0，他引：1  

Bartłomiej Wyżga  Joanna Zawiejska  Artur Radecki‐Pawlik  Hanna Hajdukiewicz 《地球表面变化过程与地形》2012,37(11):1213-1226

In the twentieth century Polish Carpathian rivers were considerably modified by channelization and gravel mining, with significant detrimental effects to their ecological integrity, vertical stability of the streambeds and flood hazard to downstream river reaches. Restoration of the rivers is thus necessary to improve their ecological status and re‐establish geomorphic dynamic equilibrium conditions. Various approaches to defining hydromorphological reference conditions, proposed to date in river restoration literature, have serious deficiencies. In particular, environmental changes that took place in the catchments of Carpathian rivers during the twentieth century invalidate the historical state of the rivers as reference for their restoration. This is illustrated by a change from bar‐braided to island‐braided channel pattern that occurred in the past century in unmanaged sections of the Czarny Dunajec in response to a reduction in flow and sediment dynamics of the river. We indicate that reference conditions should be defined as those which exist or would exist under present environmental conditions in the catchment but without human influence on the channel, riparian zone and floodplain of the river which is to be restored. This assumption was tested through the evaluation of hydromorphological river quality of the Czarny Dunajec according to the European Standard EN‐14614. The evaluation confirmed a high‐status hydromorphological quality in an unmanaged channel section, which can thus be used as a reference for restoration of impacted river sections. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

The response of saltation to wind speed fluctuations   总被引：2，自引：0，他引：2  

Sascha Pfeifer  Hans‐Jürgen Schönfeldt 《地球表面变化过程与地形》2012,37(10):1056-1064

The response time of saltation to spatial or temporal wind speed fluctuations constitutes an important control parameter for aeolian sediment transport and deposition. In this paper, we present direct measurements of the response time obtained from several field experiments. The sand transport was studied using six small microphones arranged in a vertical profile and collocated with a sonic anemometer, a webcam and a cup anemometer tower. The webcam was coupled with the sonic anemometer via a personal computer and provides information on creeping and saltating grains with a sampling rate of 10 Hz. Sediment transport measurements were obtained over four periods. The Wiener filter, a signal processing technique, is used to obtain a discrete transfer function that relates the horizontal wind speed and the non‐intermittent sand transport. The transfer function can be established using an exponential function with a time constant or characteristic response time τ without time shift. The response time fluctuated between zero and 1·5 seconds depending on the turbulence intensity, the saltation activity, the measuring height and sampling rates. The Wiener filter coefficients suggest that the response of saltation to wind speed alterations is determined by more than one process. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Assessment on variability of extreme climate events for the Upper Thames River basin in Canada   总被引：1，自引：0，他引：1  

Hyung‐Il Eum  Slobodan P. Simonovic 《水文研究》2012,26(4):485-499

Climate change may affect magnitude and frequency of regional extreme events with possibility of serious impacts on the existing infrastructure systems. This study investigates how the current spatial and temporal variations of extreme events are affected by climate change in the Upper Thames River basin, Ontario, Canada. A weather generator model is implemented to obtain daily time series of three climate variables for two future climate scenarios. The daily time series are disaggregated into hourly to capture characteristics of intense and rapidly changing storms. The maximum annual precipitation events for five short durations, 6‐, 12‐, 24‐, 48‐, and 72‐h durations, at each station are extracted from the generated hourly data. The frequency and seasonality analyses are conducted to investigate the temporal and spatial variability of extreme precipitation events corresponding to each duration. In addition, this study investigates the impacts of increase in temperature using reliability, resilience, and vulnerability. The results indicate that the extreme precipitation events under climate change will occur earlier than in the past. In addition, episodes of extremely high temperature may last longer up to 19·7% than under the no‐change climate scenario. This study points out that the revision of the design storms (e.g. 100‐ or 250‐year return period) is warranted for the west and the south east region of the basin. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Binary Mixtures of Permanganate and Chlorinated Volatile Organic Compounds in Groundwater Samples: Sample Preservation and Analysis     

Karen T. Johnson  Margie Wickham‐St. Germain  Saebom Ko  Scott G. Huling 《Ground Water Monitoring & Remediation》2012,32(3):84-92

Groundwater samples collected at sites where in situ chemical oxidation (ISCO) has been deployed may contain binary mixtures of groundwater contaminants and permanganate (MnO₄^–), an oxidant injected into the subsurface to destroy the contaminant. Commingling of the oxidant and contaminant in aqueous samples may negatively impact the quality of the sample as well as the analytical instruments used to quantify contaminant concentrations. In this study, binary mixtures comprised of (1) a multicomponent standard with permanganate and (2) groundwater samples collected at two ISCO field sites were preserved with ascorbic acid. Ascorbic acid reacts rapidly with the MnO₄^– and limits the reaction between MnO₄^– and the organic compounds in the mixture. Consequently, most of the compounds in the multicomponent standard were within the control limit for quality assurance. However, despite timely efforts to preserve the samples, the rapid reaction between permanganate and contaminant caused the concentration of several sensitive compounds to fall significantly below the lower control limit. Concentrations of volatile organic compounds in the field‐preserved binary mixture groundwater samples were greater than in samples refrigerated in the field and preserved upon arrival at the laboratory, indicating the time‐dependency and benefit of field preservation. The molar ratio of ascorbic acid required to neutralize KMnO₄ was 1.64 (mol ascorbic acid/mol KMnO₄); this provided a baseline to estimate the volume of ascorbic acid stock solution and/or the weight of crystalline ascorbic acid required to neutralize MnO₄^–. Excess ascorbic acid did not negatively impact the quality of the aqueous samples, or analytical instruments, used in the analyses.  相似文献   

Hazardous Heavy Metal Distribution in Dahuofang Catchment,Fushun, Liaoning,an Important Industry City in China: A Case Study     

Gang Wu  Ji‐You Wu  Hong‐Bo Shao 《洁净——土壤、空气、水》2012,40(12):1372-1375

Located in Liaoning Province, one of the traditional heavy industrial areas in China, Dahuofang Reservoir provides drinking water for nearly 30 000 000 citizens, as well as industrial and agricultural water for dozens of several cities and rural areas. The distribution of hazardous heavy metals is described in several types of soil, crops, and in different industrial or mining areas and main sewage irrigation areas. Five possible reasons that may cause the pollution are analyzed and listed. Also we provide some pragmatic suggestions for the remediation of heavy metals in contaminated soils.  相似文献   

Removal of Pyridine from Aqueous Solution by Adsorption on an Activated Carbon Cloth     

Pedro Alonso‐Davila  Oliva L. Torres‐Rivera  Roberto Leyva‐Ramos  Raul Ocampo‐Perez 《洁净——土壤、空气、水》2012,40(1):45-53

Pyridine is a very toxic pollutant that has to be removed from wastewater. In this work, adsorption of pyridine on activated carbon cloth (ACC) is studied as a possible alternative for eliminating pyridine from aqueous solution. The ACC was produced from polyacrylonitrile. The adsorption equilibrium data of pyridine on ACC was obtained in a batch adsorber. The experimental data was interpreted with the isotherms of Langmuir, Freundlich, and Prausnitz‐Radke (PR), and the PR isotherm better represented the experimental data. The capacity of ACC for adsorbing pyridine was favored increasing the solution pH from 3 to 6, and this effect was due to the π–π dispersive and electrostatic interactions between the pyridine species in solution and the surface complexes of ACC. The modified Langmuir model fitted reasonably well the influence of pH on the adsorption capacity. In this model was assumed that both neutral pyridine and pyridinium were simultaneously adsorbed on ACC accordingly to the experimental results. The adsorption capacity was almost independent of temperature. The reversibility study revealed that 75% of the pyridine can be desorbed from ACC indicating that part of the pyridine was irreversibly adsorbed, and possibly chemisorbed.  相似文献   

Sensitive Ion‐Flotation Separation of Ag(I) Traces Using 2‐(2‐Methoxyphenyl)benzimidazole before Flame Atomic Absorption Spectrometric Determination in Water     

Hossein Tavallali  Shahram Lalehparvar  Abdo‐Reza Nekoei  Maryam Ghane Jahromi  Khodabakhsh Niknam 《洁净——土壤、空气、水》2012,40(6):640-647

A sensitive, reliable, and environmentally friendly method for simple separation and preconcentration of Ag(I) traces in aqueous samples is presented prior to their flame atomic absorption spectrometric determinations. At pH 7.0, Ag(I) was separated with 2‐(2‐methoxyphenyl)benzimidazole (MPBI) as a new complexing agent and floated after adding sodium dodecyl sulfate (SDS) as a foaming reagent. The floated layer was then dissolved in proper amount of concentrated nitric acid in methanol and introduced to the flame atomic absorption spectrometer (FAAS). The effects of pH, concentration of MPBI, type and amount of surfactant as the floating agent, type and amount of eluting agent, and influence of foreign ions on the recovery of the analyte ion were investigated. Also, using a nonlinear curve fitting method, the formation constant of 1.62 × 10⁶ was obtained for Ag(I)–MPBI complex. The analytical curve was linear in the range of 1.8 × 10^?7–1.7 × 10^?6 mol/L for determination of Ag(I). The relative standard deviation (RSD; N = 10) corresponding to 0.7 × 10^?6 mol/L of Ag(I), the limit of detection (10 blanks), and the enrichment factor were obtained as 1.7%, 2.9 × 10^?8 mol/L, and 43.0, respectively. The proposed procedure was then applied successfully for determination of silver ions in different water samples.  相似文献   

东北地区地质空间信息网格结点建设     

康庄  张楠  王永立  陈婷玉  毛朝霞 《地质与资源》2012,21(4):414-416

利用空间信息网格技术,建立面向社会公众服务的地质空间信息共享与应用服务体系,实现东北地学数据的一体化空间数据资源组织、海量空间信息共享、高性能的协同分析处理、跨地域的空间数据服务与处理服务集成,为地质调查提供广泛有效的无障碍应用,实现多元主体形成的分布式基础数据真正共享.  相似文献   

水母伞径和饵料密度对海月水母(Aurelia sp.1)捕食率的影响     

王楠  李超伦 《海洋与湖沼》2012,43(3):480-485

海月水母在全球范围内大量暴发,严重危害海洋生态系统的健康以及鱼类资源的可持续利用。本文以卤虫无节幼体为饵料,初步研究了水母伞径和饵料密度对海月水母个体捕食率的影响以及海月水母的昼夜捕食节律。研究结果表明,海月水母的伞径对其捕食率的影响极显著(P<0.01),在1—8cm范围内,随着伞径的增加个体捕食率线性增加,两者之间的关系式为y=0.044x+0.125(R2=0.9036)。饵料密度对海月水母捕食率的影响显著(P<0.05),在0.25—26.11mgC/L范围内,随饵料密度的增加个体捕食率呈线性增加趋势,关系式为y=0.508x(R2=0.958)。在饵料充足时,海月水母没有昼夜捕食节律。在高饵料密度下海月水母出现过剩捕食,但是捕食行为依然活跃。上述结果既为量化评估海月水母对浮游动物群体的捕食压力提供了基础参数,同时水母过剩捕食行为说明依据生物量和代谢率的推算结果可能低估自然海域水母队浮游动物的捕食压力。  相似文献