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91.
Sergio Martínez-Trinidad Gilberto Hernández Silva Juventino Martínez Reyes Gregorio Solorio Munguía Sara Solís Valdez Martha Elena Ramírez Islas Rocío García Martínez 《Geofísica Internacional》2013,52(1):43-58
Deficient management of cinnabar mining left the San Joaquín region with high concentrations of mercury in its soils (2.4 – 4164 mg kg-1). Numerous cinnabar mines have contributed to the dispersion of mercury into agricultural (0.5 –314 mg kg-1) and forest (0.2 – 69 mg kg-1) soils. Sediments are a natural means of transportation for mercury, causing its spreading, especially in areas near mine entrances (0.6 – 687 mg kg-1). The nearness of maize crops to mines favors mercury accumulation in the different plant structures, such as roots, stems, leaves, and grain (0.04 – 8.2 mg kg-1); these being related to mercury volatilization and accumulation in soils. Mercury vapor present in the settlements could indicate a constant volatilization from lands and soils (22 – 153 ng m-3). The mercury levels found in the soils, in maize grain, and in the air resulted greater than the standards reported by the Official Mexican Norm (NOM) and the World Health Organization (WHO). Mercury in rainwater is due mainly to the presence of suspended atmospheric particles, later deposited on the surface (1.5 – 339 μg |-1). Mercury dissolution was found in the drinking water (10 – 170 ng |-1), with concentrations below those established by the NOM and the WHO. The contamination existing in the San Joaquín region does not reach the levels of the world’s greatest mercury producers: Almaden (Spain) and Idrija (Slovenia). It is, however, like that found in other important second degree world producers such as Guizhou (China). The population of San Joaquín, as well as its surrounding environment, are constantly exposed to mercury contamination, thus making a long term monitoring necessary to determine its effects, especially to people. 相似文献
92.
Sara Beth Keough 《Urban geography》2013,34(8):1169-1196
Between 2000 and 2010, the population of the city of Fort McMurray, Alberta increased by 80%, mainly due to the expansion of oil extraction projects and subsidiary industries. Population growth of this magnitude has significant consequences for city planning. While Fort McMurray struggles to keep up with enormous numbers of in-migrants, the cost of living in the city has skyrocketed. Using interviews with city planners and field experience in the city, in this paper I examine the current challenges faced by urban planners in Fort McMurray against the backdrop of global economic decision-making, corporate influence, and commodity dynamics. While the recession of 2008 gave city planners some breathing room, they still struggle with gathering accurate census information and predicting population growth, providing affordable housing, and balancing short-range planning with their long-term goals. Attempts by city planners to address these challenges could provide a contemporary model for urban planning in rapidly growing, resource-dependent communities. 相似文献
93.
Fatima Martin-Hernandez Sara Guerrero-Suárez 《International Journal of Earth Sciences》2012,101(3):637-647
Hematite is one of the most important carriers of remanent magnetization in natural samples. Its strong magnetocrystalline
anisotropy makes it difficult to determine one single value for the magnetic anisotropy constant and other magnetic properties.
In particular, the anisotropy of hematite within its basal plane is controversial because an assumed triaxial anisotropy compatible
with the crystallographic structure has not always been detected. This study presents a comparative analysis of rock magnetic
properties, compositional analysis and determination of the magnetic anisotropy constant. Different models with anisotropy
constant within the basal plane ranging from 0 to 13 (J m−3) are considered in the evaluation of the factors that control the presence or absence of a triaxial anisotropy. A linear
relationship between saturation magnetization (M
s
) and coercitivity (B
c
) in measurements at increasing temperatures is observed in samples where anisotropy is either uniaxial or biaxial while those
with significant triaxial anisotropies have a power–law relationship between M
s
and B
c
. 相似文献
94.
Duncan A. Christie Jos�� A. Boninsegna Malcolm K. Cleaveland Antonio Lara Carlos Le Quesne Mariano S. Morales Manfred Mudelsee David W. Stahle Ricardo Villalba 《Climate Dynamics》2011,36(7-8):1505-1521
The Andes Cordillera acts as regional ??Water Towers?? for several countries and encompasses a wide range of ecosystems and climates. Several hydroclimatic changes have been described for portions of the Andes during recent years, including glacier retreat, negative precipitation trends, an elevation rise in the 0° isotherm, and changes in regional streamflow regimes. The Temperate-Mediterranean transition (TMT) zone of the Andes (35.5°?C39.5°S) is particularly at risk to climate change because it is a biodiversity hotspot with heavy human population pressure on water resources. In this paper we utilize a new tree-ring network of Austrocedrus chilensis to reconstruct past variations in regional moisture in the TMT of the Andes by means of the Palmer Drought Severity Index (PDSI). The reconstruction covers the past 657?years and captures interannual to decadal scales of variability in late spring?Cearly summer PDSI. These changes are related to the north?Csouth oscillations in moisture conditions between the Mediterranean and Temperate climates of the Andes as a consequence of the latitudinal position of the storm tracks forced by large-scale circulation modes. Kernel estimation of occurrence rates reveals an unprecedented increment of severe and extreme drought events during the last century in the context of the previous six centuries. Moisture conditions in our study region are linked to tropical and high-latitude ocean-atmospheric forcing, with PDSI positively related to Ni?o-3.4 SST during spring and strongly negatively correlated with the Antarctic Oscillation (AAO) during summer. Geopotential anomaly maps at 500-hPa show that extreme dry years are tightly associated with negative height anomalies in the Ross?CAmundsen Seas, in concordance with the strong negative relationship between PDSI and AAO. The twentieth century increase in extreme drought events in the TMT may not be related to ENSO but to the positive AAO trend during late-spring and summer resulting from a gradual poleward shift of the mid-latitude storm tracks. This first PDSI reconstruction for South America demonstrates the highly significant hindcast skill of A. chilensis as an aridity proxy. 相似文献
95.
Gustavo M. Cruz-Bello Hallie Eakin Helda Morales Juan F. Barrera 《Natural Hazards》2011,58(1):103-116
This paper analyses the responses related to land use of coffee growers in Chiapas, Mexico to the impact of Hurricane Stan
(October 2005). A multi-temporal analysis of the effect on land cover was performed through the combination of unsupervised
classification of SPOT multispectral images and visual interpretation of panchromatic images (8 months previous to the hurricane,
and 2, 14, and 40 months after the hurricane). The information provided by this geographic analysis was interpreted in light
of information gathered though household surveys. Although the hurricane wrecked havoc across the region, the main impact
in the study area was in the riparian zones where the extent of the loss experienced in terms of coffee harvest and soil was
such that, even 14 months after the event, households with land in those areas were struggling to recover. Nevertheless, after
40 months, the zones that had suffered total soil loss began to support soil and vegetation, indicating the possibility of
replanting coffee in those areas. Although the hurricane occurred when the coffee sector was particularly fragile as a result
of the preceding several years of poor prices, the impact did not trigger extensive land use change. The surveys showed, however,
that people are now more informed of the risk of living and farming on the river margins and are now performing soil conservation
practices and planting trees to reduce risk. 相似文献
96.
Sandro Conticelli Riccardo Avanzinelli Sara Marchionni Simone Tommasini Leone Melluso 《Mineralogy and Petrology》2011,103(1-4):123-148
The Radicofani Volcano is characterised by few lava flows, a cinder cone and a denudated neck, and is part of the Tuscan Magmatic Province, the northernmost volcanic region of the Italian peninsula. In spite of the short time span of activity, a large time-dependant chemical and isotopic variability is observed. Most of the rocks of the Radicofani volcano are ultrapotassic shoshonites associated to younger basaltic andesites, found at the bottom of the neck. K2O contents are positively correlated with trace element and isotopic variations. Shoshonitic and high-K calc-alkaline rocks of the Radicofani volcano are significantly different from shoshonites occurring in association with leucite-bearing ultrapotassic rocks in the southernmost portion of the Roman Magmatic Province. The studied rocks are characterised by high, but variable, levels of incompatible trace elements with a subduction-related signature, with troughs at Ba, Ta, Nb, and Ti, and peaks at Cs, K, Th, U, and Pb. Initial values of 87Sr/86Sr range from 0.71333 to 0.71588, 143Nd/144Nd ranges from 0.512050 to 0.512183, while the lead isotope ratios vary between 18.672 and 18.716 for 206Pb/204Pb, 15.665 to 15.696 for 207Pb/204Pb, and 39.981 to 39.081 for 208Pb/204Pb. Ultrapotassic shoshonites show the highest incompatible trace element contents coupled with the highest 87Sr/86Sr and the lowest 143Nd/144Nd. On the basis of geochemical and isotopic signatures it is argued that magmas were generated in a modified lithospheric peridotitic source containing metasomatic veins generated by K-rich melts from recycled sediments within the mantle via subduction. A further metasomatic event generated by slab-derived fluids pervasively enriched the peridotitic source. Partial melting of the veins produced leucite-free ultrapotassic magmas (i.e. lamproite), and was triggered by rising of the isotherms after the orogenic front migrated eastward in the Italian Peninsula. Further rise of the isotherms induced larger degrees of partial melting inducing melting of the surrounding wall peridotite. The variation of the degree of partial melting of such a heterogeneous peridotitic source produced a wide spectrum of magma compositions, which mimic a mixing line between two components: ultrapotassic magma from partial melting of the metasomatic vein and a basaltic andesitic magma from partial melting of the surrounding peridotite. 相似文献
97.
Black dimensional stones: geology, technical properties and deposit characterization of the dolerites from Uruguay 总被引:1,自引:1,他引:0
Manuela Morales Demarco Pedro Oyhantçabal Karl-Jochen Stein Siegfried Siegesmund 《Environmental Earth Sciences》2011,63(7-8):1879-1909
Dimensional stones with a black color occupy a prominent place on the international market. Uruguayan dolerite dikes of andesitic and andesitic–basaltic composition are mined for commercial blocks of black dimensional stones. A total of 16 dikes of both compositions were studied and samples collected for geochemical and petrographical analysis. Color measurements were performed on different black dimensional stones in order to compare them with the Uruguayan dolerites. Samples of the two commercial varieties (Absolute Black and Moderate Black) were obtained for petrophysical analysis (e.g. density, porosity, uniaxial compressive strength, tensile strength, etc.). Detailed structural analyses were performed in several quarries. Geochemistry and petrography determines the intensity of the black color. The Uruguayan dolerite Absolute Black is the darkest black dimensional stone analyzed in this study. The petrophysical properties of Uruguayan dolerites make them one of the highest quality black dimensional stones. Structural analyses show that five joint sets have been recognized: two sub-vertical joints, one horizontal and two diagonal. These joint sets are one of the most important factors that control the deposits, since they control the block size distribution and the amount of waste material. 相似文献
98.
A DNA tracer used in column tests for hydrogeology applications 总被引:1,自引:1,他引:0
Lucia Aquilanti Francesca Clementi Sara Landolfo Torquato Nanni Stefano Palpacelli Alberto Tazioli 《Environmental Earth Sciences》2013,70(7):3143-3154
Tracing techniques are commonly used to investigate groundwater quality and dynamics, as well as to measure the hydrogeological parameters of aquifers. The last decade has seen a growing interest in environmentally friendly tracers, including single-stranded DNA molecules. In this study, an electrolytic tracer and a synthetic DNA tracer are comparatively evaluated in laboratory scale tests to assess their potential application in field studies aimed at investigating groundwater environments. A real-time quantitative Polymerase Chain Reaction assay was developed and optimized to detect and quantify the DNA tracer, while tracer column tests were performed to investigate the DNA tracer behavior and to compare it to the electrolytic tracer. The results show that the DNA tracer has an almost pure convective flow, while the KCl tracer experiences dispersive behavior. The tracing method proposed can be applied in hydrogeological field studies involving calcareous fractured rock systems, with the DNA tracer particularly suitable in tracing karst systems, which are often characterized by several conduits of flow. To test the DNA tracer in operation, a preliminary test was conducted in the field. 相似文献
99.
J. Cuxart C. Yagüe G. Morales E. Terradellas J. Orbe J. Calvo A. Fernández M. R. Soler C. Infante P. Buenestado A. Espinalt H. E. Joergensen J. M. Rees J. Vilá J. M. Redondo I. R. Cantalapiedra L. Conangla 《Boundary-Layer Meteorology》2000,96(3):337-370
This paper describes the Stable AtmosphericBoundary Layer Experiment in Spain (SABLES 98),which took place over the northern Spanish plateaucomprising relatively flat grassland,in September 1998. The main objectives of the campaign were to study the properties of themid-latitude stable boundary layer (SBL).Instrumentation deployed on two meteorologicalmasts (of heights 10 m and 100 m)included five sonic anemometers, 15 thermocouples,five cup anemometers and three propeller anemometers,humidity sensors and radiometers.A Sensitron mini-sodar and a tetheredballoon were also operated continuously. Atriangular array of cup anemometers wasinstalled to allow the detection ofwave events. Two nocturnal periods analysedon 14–15 and 20–21 September are used toillustrate the wide-ranging characteristics of the SBL. 相似文献
100.
Rio Tinto estuary (Spain): 5000 years of pollution 总被引:6,自引:0,他引:6
R.A. Davis Jr. A. T. Welty J. Borrego J. A. Morales J. G. Pendon J. G. Ryan 《Environmental Geology》2000,39(10):1107-1116
Mining of massive sulfide deposits in southwestern Spain extending back to the Copper and Bronze Ages has resulted in the
pollution of the Rio Tinto fluvial-estuarine complex, the site of Columbus' departure for the New World in 1492. Additional
sources of potential pollution include the large industrial complex at Huelva near the lower portion of the estuary. Extensive
analysis of surface sediment samples and cores has established that there are no geographic trends in the distribution of
the pollutants, which include Cu, Fe, Pb, Zn, Ti, Ba, Cr, V and Co. These data have, however, demonstrated that tidal flux
within the estuary carries phosphorus and perhaps other elements from the industrial complex at Huelva to the tidal limit
of the system, several kilometers upstream from the discharge site. Radiometric analysis of short cores shows that sedimentation
rates over at least the past couple of centuries have been about 0.3 cm/year. These data and that from a single deep core
demonstrate that the estuary was polluted from mining activity long before the large-scale operations began in the late nineteenth
century.
Received: 3 May 1999 · Accepted: 18 October 1999 相似文献