The Fossil Record of Freshwater Micro-Algae <Emphasis Type="Italic">Pediastrum</Emphasis> Meyen (Chlorophyceae) in Southern South America     

María del C.?ZamaloaEmail author  Guillermo?Tell 《Journal of Paleolimnology》2005,34(4):433-444

The structure and function of many Korean ecosystems have been rapidly modified since the 1960s when industrialization of the nation began. Ulsan City was the first in Korea to develop into a major industrial complex. To assess anthropogenic impacts on ecosystems surrounding Ulsan, sediment cores were collected from Mujechi-neup (bog) and Sanggae reservoir of Ulsan, and these cores were ²¹⁰Pb dated using the CRS model. Physical and chemical characteristics and pollen were analyzed, and the rates of sediment accumulation were calculated. Unsupported ²¹⁰Pb inventories in Mujechi-neup and the Sanggae reservoir were 18.04 and 16.53 pCi cm^–2, and the corresponding ²¹⁰Pb fluxes were 0.56 and 0.52 pCi cm^–2 yr^–1, respectively. The overall accumulation rate of dry matter was 0.26 kg m^–2 yr^–1 since 1852 (14 cm in depth) in Mujechi-neup. In the Sanggae reservoir, the accumulation rates of dry matter were increased from 2.1 in 1965 to 6.0 kg m^–2 yr^–1 in 1999. Pollen analysis revealed that three pollen zones existed in Mujechi-neup; a Pinus pollen-dominated zone from 0 to 5 cm in depth (1974 year), an Alnus pollen-dominated zone from 5 to 15 cm in depth (1827 year), and a Quercus pollen-dominated zone below 15 cm in depth. The shift from an Alnus dominated zone to a Pinus dominated zone was related to the Korean War between 1951 and 1953 and reforestation activities in the 1970s. In the Sanggae reservoir, there was an increase of Humulus pollen since 1996, an increase of Ambrosia pollen since the 1960s and the decrease of Graminae pollen since 1993 with the expansion of the industrial area. Similar to Mujechi-neup, the Sanggae reservoir also consists of three pollen zones: a Pinus and Typha pollen-dominated zone from 0 to 10 cm in depth (since 1993), a Graminae pollen-dominated zone from 10 to 22 cm in depth (between 1947 and 1993), and a Pinus pollen-dominated zone below 22 cm in depth (before 1947). The increase of Typha and Humulus in the 1990s indicates an increase in the inflow of nutrients into the wetlands. Also, pollen analysis revealed that Ambrosia was introduced in the 1960s during industrialization of the area. The sediment was composed of humic peat in Mujechi-neup and was composed of clay in the Sanggae reservoir. High LOI, P, and low C/N ratio between the depths of 5 to 7 cm in the Sanggae reservoir indicates an increased input of P and N. As a result, the growth of Typha was at its maximum. The total Pb content in Mujechi-neup has been increasing since the 1870s, and its accumulation in the Sanggae reservoir has been increasing since the 1960s. Thus, the history of local-scale disturbances and human activities in the watershed was reconstructed through paleoecological studies in Ulsan.  相似文献   

Nonlinear Evolution of Thermal Structures. Numerical Approach     

María Trevisan  Felipe Cordero  Miguel H. Ibáñez S 《Astrophysics and Space Science》1997,256(1-2):381-386

A numerical algorithm using a two stage, two level difference scheme has been developed to solve the heat transfer equation with nonlinear heat diffusion and bulk energy losses. The algorithm is an extension of the scheme developed by Meek and Norbury (1982). The first stage calculates an intermediate value which is used in a second stage to estimate a new value. The scheme is consistent, second-order convergent in space and almost second order in time. It has been applied to the nonlinear stability and time evolution of thermal structures constituted by optically thin plasmas with solar abundances. The configuration has been assumed to be heated at a rate T^m, cooled at a rate Tⁿ and a thermal conduction coefficient T^k. In particular, the second order analytical approximation considered in previous papers (Ibáñez and Rosenzweig, 1995; Steele and Ibáñez, 1997) has been worked out for arbitrary amplitude of the initial temperature disturbance. Particular cases of interest in Astrophysics are considered.  相似文献   

Rigorous Analysis of Available Data from Cerro Prieto and Las Tres Virgenes Geothermal Fields with Calculations for Expanded Electricity Generation     

Rosa María Prol-Ledesma  Claudia Arango-Galván  Marco-Antonio Torres-Vera 《Natural Resources Research》2016,25(4):445-458

Changes in legislation have opened the Mexican geothermal resources for exploitation to private companies; therefore the evaluation of the known geothermal areas has a high priority to plan further exploitation and possibly the expansion of the well fields. The calculation of the remaining productivity of geothermal fields currently in exploitation can be achieved with less uncertainty using the parameters obtained from production and injection wells, as well as the production efficiency of the installed plants. No information about previous volumetric evaluation is available for the fields presently being exploited, and there is the possibility that they may support an increase in their energy output or extend further their production life. The most widely used calculation technique is the USGS volumetric method that requires the knowledge of parameters that can be measured only after exploitation started. Heat in place-volumetric evaluation was undertaken for two fields in Mexico: Cerro Prieto and the Las Tres Vírgenes geothermal fields, using all information obtained by exploration surveys and exploitation drilling. The obtained values allow planning a possible expansion of the fields based on their estimated mean potential output that is 1397 MWe for Cerro Prieto and 48 MWe for Las Tres Vírgenes compared to the presently installed capacity of 580 MWe.  相似文献   

An Interdisciplinary Methodology for the Characterization and Visualization of the Heritage of Roadway Corridors          下载免费PDF全文

Mar Loren‐Méndez  Rafael Mata‐Olmo  Rita Ruiz  Daniel Pinzón‐Ayala 《Geographical review》2016,106(4):489-515

Roads, particularly since the advent of motorized traffic, have hugely impacted contemporary landscapes. Although their significance was noted in the 1980s, specific roadway‐heritage studies are scarce. Research in different disciplines has identified certain features of roads, but an integrated approach to roadway heritage or a consensus on what this constitutes are lacking. This article proposes an interdisciplinary methodology to assess roadway heritage. Roadways are interpreted within the framework of semantic openness that currently characterizes heritage studies, territory being the basic element of interpretation. Rather than a fragmented approach to conservation, the research defines integrated heritage configurations where natural, cultural, and historical features combine to produce a cohesive form of heritage. GIS (Geographical information systems) technology is used with an online database to assess the complexity of roadway heritage. ICT (Information and communications technology) strategies to raise public awareness are outlined. The methodology is applied to assess the historical N‐340 Mediterranean roadway corridor in Spain.  相似文献   

Urban downburst vulnerability and damage assessment from a case study in Argentina     

Gonzalo L. Pita  María L. A. de Schwarzkopf 《Natural Hazards》2016,80(1):445-469

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The Baza Fault: a major active extensional fault in the central Betic Cordillera (south Spain)   总被引：2，自引：0，他引：2  

P. Alfaro  J. Delgado  C. Sanz de Galdeano  J. Galindo-Zaldívar  F. J. García-Tortosa  A. C. López-Garrido  C. López-Casado  C. Marín-Lechado  A. Gil  M. J. Borque 《International Journal of Earth Sciences》2008,97(6):1353-1365

In the Guadix-Baza Basin (Betic Cordillera) lies the Baza Fault, a structure that will be described for the first time in this paper. Eight gravity profiles and a seismic reflection profile, coupled with surface studies, indicate the existence of a NE-dipping normal fault with a variable strike with N-S and NW-SE segments. This 37-km long fault divides the basin into two sectors: Guadix to the West and Baza to the East. Since the Late Miocene, the activity of this fault has created a half-graben in its hanging wall. The seismic reflection profile shows that the fill of this 2,000–3,000 m thick asymmetric basin is syntectonic. The fault has associated seismicity, the most important of which is the 1531 Baza earthquake. Since the Late Tortonian to the present, i.e. over approximately the last 8 million years, extension rates obtained vary between 0.12 and 0.33 mm/year for the Baza Fault, being one of the major active normal faults to accommodate the current ENE–WSW extension produced in the central Betic Cordillera. The existence of this fault and other normal faults in the central Betic Cordillera enhanced the extension in the upper crust from the Late Miocene to the present in this regional compressive setting.  相似文献   

Water-soluble inorganic ions of size-differentiated atmospheric particles from a suburban site of Mexico City     

Telma Castro  Oscar Peralta  Dara Salcedo  José Santos  María I. Saavedra  María L. Espinoza  Alejandro Salcido  Ana-Teresa Celada-Murillo  Susana Carreón-Sierra  Harry Álvarez-Ospina  Giovanni Carabali  Valter Barrera  Sasha Madronich 《Journal of Atmospheric Chemistry》2018,75(2):155-169

During the MILAGRO campaign, March 2006, eight-stage cut impactors were used to sample atmospheric particles at Tecámac (T1 supersite), towards the northeast edge of the Mexico City Metropolitan Area, collecting fresh local emissions and aged pollutants produced in Mexico City. Particle samples were analyzed to determine total mass concentrations of Ca²⁺, Mg²⁺, NH₄ ⁺, K⁺, Cl^?, SO₄ ^2?, and NO₃ ^?. Average concentrations were 22.1 ± 7.2 μg m^?3 for PM₁₀ and 18.3 ± 6.2 μg m^?3 for PM_1.8. A good correlation between PM₁₀ and PM_1.8, without influence from wind patterns, indicates that local emissions are more important than the city’s pollution transported to the site, despite the fact that Tecámac is just 40 km away from Mexico City. A lack of diurnal patterns in the PM_2.5/PM_1.8 ratio supports this conclusion. The inorganic composition of particles suggests that vehicles, soil resuspension, and industries are the main pollutant sources. Finally, the particles were found to be neutralized, in agreement with observations in the Mexico City Metropolitan Area.  相似文献   

Reconstructing recent environmental changes using non-biting midges (Diptera: Chironomidae) in two high mountain lakes from northern Patagonia,Argentina     

Fernanda Montes de Oca  Luciana Motta  María Sofía Plastani  Cecilia Laprida  Andrea Lami  Julieta Massaferro 《Journal of Paleolimnology》2018,59(2):175-187

Remote lakes of northern Patagonia are ideal sites for examining climate- and non-climate-driven changes in aquatic ecosystems because there is little evidence of human influence and there is no detailed information on recent environmental trends in the region (i.e. the last 200 years). Subfossil chironomids (Diptera: Chironomidae) are useful paleoindicators due to their specific response to numerous environmental factors. Here, we analyze the chironomid subfossil assemblages from two remote lakes located in different environmental settings in Nahuel Huapi National Park of northern Patagonia, Argentina. Chironomids combined with sedimentary pigments (chlorophyll derivatives and total carotenoids) and organic matter provided information on the environmental history of the lakes for the last ca. 200 years. The ²¹⁰Pb chronology and tephra layers are used to establish the chronology of changes in the chironomid assemblages associated to different environmental factors that impacted the area during the period covered by the study. The deposition of volcanic ash affected the abundance and composition of chironomid assemblage throughout the record of both lakes. However, changing climate conditions and human activities are also responsible for chironomid changes in the last 50 years.  相似文献   

Estimation of daily global solar radiation as a function of routine meteorological data in Mediterranean areas     

Francisco Javier Meza  María Lorenzo Yebra 《Theoretical and Applied Climatology》2016,125(3-4):479-488

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Effect of crude petroleum on water repellency in a clayey alluvial soil     

D. C. Marín-García  R. H. Adams  R. Hernández-Barajas 《International Journal of Environmental Science and Technology》2016,13(1):55-64

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