Location-based environmental factors contributing to rainfall-triggered debris flows in the Ba river catchment,northwest Viti Levu island,Fiji     

M. Stephens  J. H. Lowry  A. R. Ram 《Landslides》2018,15(1):145-159

Mass movements in tropical Pacific small island developing states (SIDS) can be devastating although studies are relatively few and contributing environmental factors are not often investigated in detail. On 25 January 2012, following 3 days of heavy monsoonal rainfall (c. 550 mm) during a La Niña episode, more than 150 debris flows were triggered in the western part of the Ba river catchment of northwest Viti Levu island, Fiji. Reconnaissance field survey and geographical information system (GIS) analyses using high-resolution satellite imagery were carried out to investigate factors that may have led to the occurrence of the debris flows in the catchment. We evaluated the correlation between the density of mass movements (number of mass movements/km²) and several continuous variables using data measured within the GIS. There was a weak but significant positive correlation between mass movement density and elevation (r = 0.38, p value < 0.01), cyclonic precipitation (r = 0.37, p value < 0.01) and stream density (r = 0.31, p value < 0.01). Ninety-three percent of the mass movements occur within a plantation of Pinus caribaea (Caribbean pine) on slopes oriented mainly to the northeast and east on (trade) windward slopes and may be significant factors for their development. Although forests generally have a stabilizing effect on slopes, the plantation at Ba was a mature stand on its second plantation cycle and is a species that has a shallow rooting system making it more susceptible to failure.  相似文献   

The digital ‘connected’ earth: open technology for providing location-based services on degraded communication environments     

Ramón Piedrafita  Rubén Béjar  Rubén Blasco  Alvaro Marco  F. Javier Zarazaga-Soria 《International Journal of Digital Earth》2018,11(8):761-782

In the current world, it is easy to listen that everybody and everything is connected. Over this connected world, the concept of location-based services has grown in order to provide digital services in everyplace and at every time. Nevertheless, this is not 100% true because the connection is not guaranteed for many people and in many places. These are the Degraded Communications Environments (DCE), environments where the availability of high-speed communications is not guaranteed in at least the 75% of the time. This paper works over the experience of a previous work in developing light protocols that do not need broadband for communication. This work provides an extension of these protocols for the inclusion of mobile devices as elements of the communication process and a set of libraries to allow the development of applications in DCE. The work done has involved the development of two frameworks: an Android framework that makes the incorporation of Android devices easier and a server-based framework that provides the server side for the development of the referred applications. A use case that uses these two frameworks has been developed. Finally, all technology developed is available throw a public Git repository.  相似文献   

Metal-enriched nanoparticles and black carbon: A perspective from the Brazil railway system air pollution     

Bianca D. Lima  Elba C. Teixeira  James C. Hower  Matheus S. Civeira  Omar Ramírez  Cheng-Xue Yang  Marcos L.S. Oliveira  Luis F.O. Silva 《地学前缘(英文版)》2021,12(3):101129

Having a better understanding of air pollutants in railway systems is crucial to ensure a clean public transport. This study measured, for the first time in Brazil, nanoparticles (NPs) and black carbon (BC) on two ground-level platforms and inside trains of the Metropolitan Area of Porto Alegre (MAPA). An intense sampling campaign during thirteen consecutive months was carried out and the chemical composition of NPs was examined by advanced microscopy techniques. The results showed that highest concentrations of the pollutants occur in colder seasons and influenced by variables such as frequency of the trains and passenger densities. Also, internal and external sources of pollution at the stations were identified. The predominance of NPs enriched with metals that increase oxidative stress like Cd, Fe, Pb, Cr, Zn, Ni, V, Hg, Sn, and Ba both on the platforms and inside trains, including Fe-minerals as hematite and magnetite, represents a critical risk to the health of passengers and employees of the system. This interdisciplinary and multi-analytical study aims to provide an improved understanding of reported adverse health effects induced by railway system aerosols.  相似文献   

Effects of two offshore gas platforms on soft-bottom benthic communities (northwestern Adriatic Sea, Italy)     

Sarine Manoukian  Alessandra Spagnolo  Giuseppe Scarcella  Elisa Punzo  Roberta Angelini  Gianna Fabi   《Marine environmental research》2010,70(5):402-410

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GPS ground deformation patterns at Mount St. Helens (Washington,USA) from 2004 to 2010     

Mimmo Palano  Elisa Guarrera  Mario Mattia 《地学学报》2012,24(2):148-155

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Mangrove ecology,aquatic primary productivity,and fish community dynamics in the Teacapán-Agua Brava Lagoon-Estuarine system (Mexican Pacific)     

F. Flores-Verdugo  F. González-Farías  O. Ramírez-Flores  F. Amezcua-Linares  A. Yáñez-Arancibia  M. Alvarez-Rubio  J. W. Day 《Estuaries and Coasts》1990,13(2):219-230

Aquatic primary productivity, mangrove ecology, and fish community dynamics were investigated in the Teacapán-Agua Brava lagoon-estuarine system, the most extensive mangrove ecosystem on the Pacific coast of Mexico with three species of mangroves distributed heterogeneously (Laguncularia racemosa, Rhizophora mangle, andAvicennia germinans). Tree density was 3,203 trees ha^?1 and basal area was 14.0 m² ha^?1. Litterfall was 1,417 g m^?2 yr^?1, characteristic of a productive riverine forest. The degradation constant forLaguncularia racemosa leaves varied from 1.71 to 4.7 yr^?1 and mean annual net aquatic productivity was 0.41 g C m^?3 d^?1. There were high concentrations of humic substances (up to 150 mg l^?1) early in the wet season. Seasonal variations of the above parameters seemed closely related to the ecology of fish populations. There were 75 fish species distributed in two principal assemblages associated with wet and dry seasons. Diversity and biomass analysis indicated 18 dominant species. Total biomass of the community in this coastal system was estimated at 10 g wet wt m^?2. The highest biomass occurred in the wet season. The most common fish species wereMugil curema, Achirus mazatlanus, Galeichthys caerulescens, Arius liropus, Diapterus peruvianus, Lile stolifera, Centropomus robalito, andEucinostomus sp., all of which have fishery importance. Primary productivity and fish community ecology are controlled by habitat characteristics, river discharge, and climatic seasonality.  相似文献   

Conflicts between wetland conservation and groundwater exploitation: Two case histories in Spain   总被引：2，自引：0，他引：2  

M. Ramón Llamas 《Environmental Geology》1988,11(3):241-251

The problems in two Spanish national parks located on wetlands are analyzed. The hydrogeological and ecological characteristics of the two parks are somewhat different as are their respective degrees of deterioration. The Tablas de Daimiel National Park is located on the Central Plateau of Spain. It used to consist of a marshy area of about 20 km² around the confluence of two relatively small rivers. The area was marshy mainly because it was the natural discharge zone for a Tertiary aquifer system about 100 m thick extending over an area of some 5,000 km², composed of calcareous and detrital material of continental origin. The average annual recharge has been estimated at approximately 350 hm³/yr. Current groundwater withdrawal is around 450 hm³/yr, mainly used to irrigate a surface area of some 1,000 km². This overdevelopment has led to a continuous depletion of the regional water table and eventually to the drying out of the marshy area. Spontaneous combustion or fires caused by man have occurred in about 10 km² of the desiccated areas since the spring of 1986. The Doñana National Park is located on the estuary of the River Guadalquivir. The aquifer system of the Lower Guadalquivir estuary consists essentially of a permeable formation of unconsolidated Plioquaternary materials with an area of some 3,000 km². Under the marshy area (about 1,800 km²) the aquifer system is confined below low-permeability estuary deposits which can be over 100 m thick. Around most of the marshland the aquifer crops out and is recharged by rain. The Doñana National Park is over 700 km² in size, part of which is in the marshland and part in the recharge area where the aquifer is phreatic. In the 1970s Spain's largest irrigation project using groundwater, covering a surface area of 240 km², was planned in an area bordering on the national park. The initial project has been scaled down considerably as a result of protests by conservation groups. However, it seems likely that the water table depletion as a result of pumpage for irrigation could cause a large part of the ecotone situated at the contact-line between the marshland and the phreatic aquifer to disappear. This ecotone exists because it is a natural groundwater dischange area.  相似文献   

Distribution of benthic flora in the lower course of the Valdivia River,Chile     

Carlos Ramírez  Heriberto Figueroa  Enrique Hauenstein  Domingo Contreras 《Estuaries and Coasts》1989,12(2):111-118

The Valdivia River (Lake Region, Chile) originates in Riñihue Lake and flows into the sea at Corral Bay (39°52′S latitude), changing names several times along its course. The aquatic benthic flora (algae and aquatic plants) of the Valdivia River was characterized, based on 22 sites sampled and 124 plant species collected. Four benthic vegetation zones were established using presence-absence data: a freshwater zone and a marine zone were found at the extremes of the transect; an estuarine zone and a discontinuity zone were detected in the middle of this transect. The freshwater zone was characterized by a relatively diverse assemblage of vascular plants, the marine zone was dominated by algae and was rich in species. By contrast the estuarine zone was inhabited by only a few species but in great abundance, while the discontinuity zone was poor, in species and low in cover vegetation.  相似文献   

Static deformation of two welded half-spaces due to very long strike-slip dislocations     

Raj Kumar Sharma  Nat Ram Garg  Kuldip Singh 《Journal of Earth System Science》1991,100(4):379-388

Closed form analytic expressions for displacement and stresses at any point of either of the two homogeneous, isotropic, perfectly elastic half-spaces in welded contact due to very long strike-slip dislocations are obtained. Both cases of vertical and horizontal strike-slip dislocations are discussed in detail. Variation of the displacement with horizontal distance from the fault and with vertical distance from the interface for a vertical strike-slip fault is studied numerically.  相似文献   

Mode I fracture toughness of coal     

Ram B. Bhagat 《Geotechnical and Geological Engineering》1985,3(3):229-236

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