Analysis of water control in an underground mine under strong karst media influence (Vazante mine,Brazil)     

Hugo Ninanya  Nilson Guiguer  Eurípedes A. VargasJr  Gustavo Nascimento  Edmar Araujo  Caroline L. Cazarin 《Hydrogeology Journal》2018,26(7):2257-2282

This work presents analysis of groundwater flow conditions and groundwater control measures for Vazante underground mine located in the state of Minas Gerais, Brazil. According to field observations, groundwater flow processes in this mine are highly influenced by the presence of karst features located in the near-surface terrain next to Santa Catarina River. The karstic features, such as caves, sinkholes, dolines and conduits, have direct contact with the aquifer and tend to increase water flow into the mine. These effects are more acute in areas under the influence of groundwater-level drawdown by pumping. Numerical analyses of this condition were carried out using the computer program FEFLOW. This program represents karstic features as one-dimensional discrete flow conduits inside a three-dimensional finite element structure representing the geologic medium following a combined discrete-continuum approach for representing the karst system. These features create preferential flow paths between the river and mine; their incorporation into the model is able to more realistically represent the hydrogeological environment of the mine surroundings. In order to mitigate the water-inflow problems, impermeabilization of the river through construction of a reinforced concrete channel was incorporated in the developed hydrogeological model. Different scenarios for channelization lengths for the most critical zones along the river were studied. Obtained results were able to compare effectiveness of different river channelization scenarios. It was also possible to determine whether the use of these impermeabilization measures would be able to reduce, in large part, the elevated costs of pumping inside the mine.  相似文献   

Biomass allometric equation and expansion factor for a mountain moist evergreen forest in Mozambique     

Sá Nogueira Lisboa  Benard Soares Guedes  Natasha Ribeiro  Almeida Sitoe 《Carbon balance and management》2018,13(1):23

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Rapid tidal marsh development in anthropogenic backwaters     

Brian Yellen  Jonathan Woodruff  Caroline Ladlow  David K. Ralston  Sarah Fernald  Waverly Lau 《地球表面变化过程与地形》2021,46(3):554-572

Tidal marsh restoration and creation is growing in popularity due to the many and diverse sets of services these important ecosystems provide. However, it is unclear what conditions within constructed settings will lead to the successful establishment of tidal marsh. Here we provide documentation for widespread and rapid development of tidal freshwater wetlands for a major urban estuary as an unintended result of early industrial development. Anthropogenic backwater areas established behind railroad berms, jetties, and dredge spoil islands resulted in the rapid accumulation of clastic material and the subsequent initiation of emergent marshes. In one case, historical aerial photos document this transition occurring in less than 18 years, offering a timeframe for marsh development. Accretion rates for anthropogenic tidal marshes and mudflats average 0.8–1.1 and 0.6–0.7 cm year⁻¹, respectively, equivalent to two to three times the rate of relative sea level rise as well as the observed accretion rate at a 6000+ year-old reference marsh in the study area. Paired historical and geospatial analysis revealed that more than half of all the tidal wetlands on the Hudson River were likely triggered by anthropogenic development since the onset of the industrial era, including two-thirds of the emergent cattail marsh. These inadvertently constructed tidal wetlands currently trap roughly 6% of the Hudson River's sediment load. Results indicate that when sediment is readily available, freshwater tidal wetlands can develop relatively rapidly in sheltered settings. The study sites serve as useful examples to help guide future tidal marsh creation and restoration efforts.  相似文献   

Methodology and Application of Hafnium Isotopes in Ilmenite and Rutile by MC‐ICP‐MS     

Caroline‐Emmanuelle Morisset  James S. Scoates  Dominique Weis  André Rahier 《Geostandards and Geoanalytical Research》2014,38(2):159-176

The high abundances of the high field‐strength elements in ilmenite and rutile make these minerals particularly suitable for hafnium isotopic investigations. We present a technique for separating Hf by ion exchange chemistry from high‐TiO₂ (> 40% m/m) minerals to achieve precise Hf isotopic composition analyses by MC (multiple collector)‐ICP‐MS. Following digestion and conversion to chlorides, the first elution column is used to separate iron and the rare earth elements, the second column is designed to separate most of the titanium from Hf, an evaporation step using HClO₄ is then performed to remove any trace of HF in preparation for the third column, which is needed to eliminate any remaining trace of titanium. The modified chemistry helped to improve the yields from < 10 to > 78% as well as the analytical precision of the processed samples (e.g., sample 2033‐A1, ¹⁷⁶Hf/¹⁷⁷Hf = 0.282251 ± 25 before vs. 0.282225 ± 6 after). The technique was tested on a case study in which the Hf isotopic ratios of ilmenite and rutile (analysed prior to the chemistry improvement) were determined and permitted to evaluate that the origin of rutile‐bearing ilmenite deposits is from the same or similar magma than their, respectively, associated Proterozoic anorthosite massifs (Saint‐Urbain and Lac Allard) of the Grenville Province in Québec, Canada.  相似文献   

Spatial Variability of Stable Isotope Ratios in Oysters (Crassostrea gigas) and Primary Producers Along an Estuarine Gradient (Bay of Brest, France)     

Violette Marchais  Gauthier Schaal  Jacques Grall  Anne Lorrain  Caroline Nerot  Pierre Richard  Laurent Chauvaud 《Estuaries and Coasts》2013,36(4):808-819

This study aimed at characterizing the diet of the oyster Crassostrea gigas along an estuarine gradient in the Bay of Brest (France), through stable isotope (δ¹³C and δ¹⁵N) measurements in primary producers and wild oysters. The contribution of different potential food sources to the diet of C. gigas was estimated at high spatial resolution (over a gradient of 40 km with samplings every 2 km) to identify ecological transition zones and highlighted the dominance of resuspended biofilm in oysters diet. Although the different primary producers did not display any obvious pattern along the estuarine gradient, the stable isotope signatures of C. gigas differed among estuarine, inner Bay, and open sea sites. In particular, a striking ¹⁵N depletion pattern was found along the gradient which allowed to identify seven homogeneous groups. Moreover, some unexpected values found at two stations within the estuary revealed localized anthropogenic disturbances. Overall, our results suggest that suspension feeders might be better indicators of ecosystem functioning than primary producers and reflect the different ecological processes occurring along estuarine gradients, including localized anthropogenic inputs. We suggest that the usefulness of suspension feeders as indicators of ecosystem functional typology lies in the dominance of benthic material in their diet, which results in locally occurring processes being reflected in oysters’ stable isotope ratios.  相似文献   

Stochastic Simulation Model for the Spatial Characterization of Lung Cancer Mortality Risk and Study of Environmental Factors     

Ana Rita Oliveira  Cristina Branquinho  Maria Pereira  Amílcar Soares 《Mathematical Geosciences》2013,45(4):437-452

This paper presents a study in which the lung cancer risk in males was characterized based on a simulation model of mortality rates. Block sequential simulation of mortality rates, measured in counties of different sizes, was implemented and applied to a normal grid of continental Portugal with high spatial resolution. The uncertainty in the mortality rate measurements, directly related to differences in the population size of each county, was integrated in a block direct sequential simulation through Poisson kriging of local means and variances. Three age groups were examined: 50–59, 60–69, and 70–79 years. After the continuous geographic patterns of lung cancer risk were obtained, factors potentially associated with the main areas of risk were analyzed for southern Portugal. Thus, a defined class of land use and dry weather events, related to airborne particulate matter, were found to be associated with high-risk areas, resulting in high local spatial correlation patterns in all three age groups.  相似文献   

Steepness and asymmetry of the largest waves in storm sea states   总被引：1，自引：0，他引：1  

C. Guedes Soares  Z. Cherneva  E. M. Anto 《Ocean Engineering》2004,31(8-9):1147-1167

Several steepness coefficients are proposed to describe the steepness and asymmetry of the largest individual waves in measured records of storm sea states. These coefficients are calculated for data collected in the North Sea and the Atlantic Ocean. Several statistical relationships between the new parameters are identified.  相似文献   

Southern Exceptionalism and the Perils of Region     

Caroline Rose Nagel 《The Professional geographer》2013,65(4):678-686

Contemporary political trends associated with the rise of Donald Trump seem to confound traditional regional designations in the United States. Yet the concept of region remains salient in popular discourse. This is especially true with respect to “the South,” which appears in several recent nonacademic works as the source of troubling social and political currents. More surprising, given decades of critique of “Southern exceptionalism,” has been the reappearance of the South as a focus of analysis in the scholarly literature on immigration. This scholarly literature works to deessentialize the South by highlighting the vagaries and instabilities of Southern identities, institutions, and landscapes. It can, however, subtly and inadvertently reinforce Southern exceptionalism by identifying the South as a place marked by uniquely fraught histories of racial exclusion. This article critically assesses how the South as a regional concept has located the problem of race in the United States in a specific time and place. This leads to a broader discussion of the persistence of regional imaginaries in the discipline of geography and the need for more deliberate consideration of the geographical concepts that guide our analyses of societal change.  相似文献   

Long-Term Changes in Population Dynamics of the Shrimp Palaemon longirostris in the Gironde Estuary     

Mélanie Béguer  Julien Bergé  Caroline Gardia-Parège  Laurent Beaulaton  Gérard Castelnaud  Michel Girardin  Philippe Bo?t 《Estuaries and Coasts》2012,35(4):1082-1099

Spanning 20?years (1979?C2007), this study is the longest time series pertaining to the resident shrimp species Palaemon longirostris in a European estuary. Data from monthly faunal surveys undertaken across the middle part of the Gironde estuary from April 1979 along with data from a statistical analysis of the commercial catches throughout the entire estuary and river were considered in order to explore their inter and intra-annual variability and long-term trends. Long-term densities series as well as environmental series (salinity, discharge, temperature and NAO) were decomposed and the effects of environmental variables were also examined using statistical models (GAMs). This revealed important spatio-temporal variability and a significant overall decrease in abundance of this species in the Gironde estuary since the beginning of the 1980s. This long-term decrease in abundance corresponded significantly to long-term decreases in both discharge and the NAO index, as well a long-term increase in temperature and salinity in the middle part of the estuary. However, models showed that environmental factors explained only a small part of the variability. The upstream shift of the population highlighted in this study, probably due to the intrusion of marine waters into the middle section of the estuary, may also have contributed to its decrease in abundance. Inter-annual variability of densities was also significantly linked with inter-annual fecundity fluctuations, and a significant decrease in both mean female size and fecundity was shown for preserved samples from 1992. Moreover, the breeding period has been temporally stretched out and began earlier in more recent years, potentially due to the increase in spring temperature.  相似文献   

Retrieval of Large-Scale Hydrological Signals in Africa from GRACE Time-Variable Gravity Fields     

Jean-Paul Boy  Jacques Hinderer  Caroline de Linage 《Pure and Applied Geophysics》2012,169(8):1373-1390

Since its launch in April 2002, the Gravity Recovery and Climate Experiment (GRACE) mission is recording the Earth’s time-variable gravity field with temporal and spatial resolutions of typically 7–30?days and a few hundreds of kilometers, allowing the monitoring of continental water storage variations from both continental and river-basin scales. We investigate here large scale hydrological variations in Africa using different GRACE spherical harmonic solutions, using different processing strategies (constrained and unconstrained solutions). We compare our GRACE estimates to different global hydrology models, with different land-surface schemes and also precipitation forcing. We validate GRACE observations through two different techniques: first by studying desert areas, providing an estimate of the precision. Then we compare GRACE recovered mass variations of main lakes to volume changes derived from radar altimetry measurements. We also study the differences between different publicly available precipitation datasets from both space measurements and ground rain gauges, and their impact on soil-moisture estimates.  相似文献