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11.
12.
Coalbed methane (CBM) is a worldwide exploration target of the petroleum industry. In Brazil, the most important coal-bearing succession is associated with the Permian Rio Bonito Formation of the Paraná Basin. The gas-prone areas are located at the southeastern margin of the Paraná Basin and possibly in the offshore region of the northern part of the Pelotas Basin. Coalfields end abruptly at the present day shoreline, a result of rifting of Gondwana and the evolution of the South Atlantic Ocean. All geologic indicators suggest that in pre-rift times the coal seams extended further eastwards, probably now lying deeply buried below the sedimentary succession of the Pelotas Basin. The present paper discusses structural, stratigraphic, seismic and aeromagenetic data that support the preservation of continental crust beneath ocean sediment. If the coal beds had similar lateral extent to known onshore coals, and coal beds extended across the projected extension of the Parana basin, and there was a conservative 5 m of cumulative coal thickness, then a potential methane volume can be estimated for this newly inferred resource. Average onshore coal gas content is 32 scf/ton (1.00 m3/ton). If this is similar in the offshore coal deposits, then the hypothetical methane volume in the offshore area could be in excess of 1.9 × 1012 scf (56 × 109 m3). Metamorphism from dikes associated with rifting are potential complicating factors in these deposits, and since no borehole reaching the deep-lying strata in the offshore area are available, this is a hypothetical gas resource with a certain level of uncertainty which should be tested in the future by drilling a deep borehole. 相似文献
13.
Excessive terrestrial nutrient loadings adversely impact coral reefs by primarily enhancing growth of macroalgae, potentially leading to a phase‐shift phenomenon. Hydrological processes and other spatial and temporal factors affecting nutrient discharge must be examined to be able to formulate effective measures for reducing nutrient export to adjacent reefs. During storm events and baseflow periods, water samples were obtained from the tropical Todoroki River, which drains an intensively agricultural watershed into Shiraho coral reef. In situ nutrient analyzers were deployed for 6 months to hourly measure dissolved nutrient (NO3−‐N and PO43−‐P) concentrations. Total phosphorus (TP) and suspended solid concentration (TSS) were increased by higher rainfall intensity (r = 0·94, p < 0·01) and river discharge Q (r = 0·88, p < 0·01). In contrast, NO3−‐N concentration tends to decrease drastically (e.g. from 3 to 1 mg l−1) during flood events. When base flow starts to dominate afterwards, NO3−‐N manifested an increasing trend, but decreases when baseflow discharge becomes low. This counter‐clockwise hysteresis for NO3−‐N highlights the significant influence of groundwater discharge. N delivery can therefore be considered a persistent process compared to sediment and P discharge, which are highly episodic in nature. Based on GIS analysis, nutrient concentration along the Todoroki River was largely affected by the percentage of sugarcane/bare areas and bedrock type. The spatial distribution of N concentration in the river reflects the considerable influence of subsurface geology—higher N levels in limestone‐dominated areas. P concentrations were directly related to the total length of artificial drainage, which enhances sediment transport. The use of high‐resolution monitoring data coupled with GIS‐based spatial analysis therefore enabled the clarification of control factors and the difference in the spatio‐temporal discharge characteristics between N and P. Thus, although erosion‐reduction schemes would reduce P discharge, other approaches (e.g. minimize fertilizer) are needed to reduce N discharge. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
14.
Beatriz Levi Luis Aguirre Jan Olov Nyström 《Contributions to Mineralogy and Petrology》1982,80(1):49-58
Partial spilitization of a 9 km thick pile of flood basalts with highly vesicular flow tops gave rise to patterns of secondary mineralogy at different scales: (a) a local pattern of mineralogical variation from the almost unaltered bottom towards the altered top of each flow, and (b) an overall pattern, comparing flow tops throughout the pile, with changes in mineralogical composition within a sequence of metamorphic zones and facies. The local patterns mimic the trend of the overall pattern, but are of opposite direction and telescoped. Thus, a gradual ordering and Andepletion of the secondary albite and increases in the Fe*/Al ratio of epidote and pumpellyite upwards within individual flows are comparable in range to corresponding overall changes downwards throughout several kilometres. The mineralogical changes within the flows diminish in range towards the more altered deeper part of the pile.The local and overall patterns cannot be interpreted in terms of grade. They represent trends from metastable towards stable equilibrium, this latter only approached in the flow tops of the lower part of the pile. The patterns of secondary mineralogy were formed by an interplay of metamorphic gradients at different scales at any given time, and as burial proceeded. The overall pattern was caused by depth-controlled gradients: increasing P
fluid, temperature and temperature-induced increase of reaction rates, and decreasing fO2 (downwards in the pile). The local patterns resulted from permeability-controlled gradients: increasing reaction rates, fO2 and contrast in chemical activity between different domains, and decreasing P
fluid (upwards in each flow). The mineralogical observations reported in this paper fall into line if the overall temperature-induced increase of reaction rates and the local permeability-controlled rate factors played the leading role during burial metamorphism of the pile. 相似文献
15.
Rodriguez V Fernandez-mayoralas G Rojo F 《International journal of population geography : IJPG》1998,4(2):183-200
"This paper studies northern European retired immigrants, using data generated by a questionnaire survey of 300 respondents and in-depth interviews with 20 people in 13 municipalities. Reasons for moving to Spain, the advantages and disadvantages reported of living there, and the perceived impacts on the local region were analysed, paying particular attention to cross-national differences between British, German, Benelux and Nordic retirees. The results show that sociodemographic and economic features of the settlers tend to be quite similar, whilst reasons for moving, stated advantages and disadvantages, and consequences and impacts exhibit some cross-national differentiation." 相似文献
16.
A. Blanco A. Borghesi E. Epifani S. Fonti V. Orofino F. Strafella 《Astrophysics and Space Science》1998,262(1):107-113
The main constituents of the dust, produced around late-type carbon stars, are thought to be carbon and silicon carbide (SiC), although their exact nature is not yet well established. This subject has been addressed by several authors and good fits of a large number of IRAS sources (chosen among the carbon stars exhibiting the SiC feature at about 11.3 m) were obtained. In this work we use the same procedure on a limited number of objects, of the same type, taking into account the variability of such sources and the changes induced in their IR spectra. For this purpose, the chosen stars have been observed with a spectral resolution higher than that available for the IRAS data (/ 50), using the CGS3 instrument of the UKIRT telescope, both in the low ( / 160) and in the high ( / 500) resolution configuration. The results are discussed and some preliminary conclusions are drawn. 相似文献
17.
Echavarri-Erasun B Juanes JA García-Castrillo G Revilla JA 《Marine pollution bulletin》2007,54(7):941-954
An investigation on the effects of deepwater outfall discharges on the status of rocky reef communities was carried out. The sanitation system was found to be an environmentally suitable option for the protection of those habitats situated in high energy coastal environments. Sediments occurring between the predominating rocky substrates showed low values of the fine fraction (<63microm) and organic matter content. In addition, high average concentrations of Cd, Hg and Zn were found in these sediments, though these values were similar to those registered in non-affected sites, far away from the outfall. On the other hand, those assemblages typical of hard substrates that settled near the outfall showed an increase in total richness and abundance of macroinvertebrates. Moreover, the average number of species of each taxonomic group, a good indicator of the maintenance of the previous trophic structure, only varied considerably over time at the rip-rap protection. In a global context, those changes were not directly related to the discharge disturbances, but to the natural variability or the successional processes occurring within those communities. Only communities dwelling in the rip-rap protection area were affected by the proximity of the discharges. 相似文献
18.
Barbara Suski Gilles Brocard Christine Authemayou Beatriz Consenza Muralles Christian Teyssier Klaus Holliger 《Tectonophysics》2010,480(1-4):88-98
The Polochic and Motagua faults define the active plate boundary between the North American and Caribbean plates in central Guatemala. A splay of the Polochic Fault traverses the rapidly growing city of San Miguel Uspantán that is periodically affected by destructive earthquakes. This fault splay was located using a 2D electrical resistivity tomography (ERT) survey that also characterized the fault damage zone and evaluated the thickness and nature of recent deposits upon which most of the city is built. ERT images show the fault as a ~50 m wide, near-vertical low-resistivity anomaly, bounded within a few meters by high resistivity anomalies. Forward modeling reproduces the key aspects of the observed electrical resistivity data with remarkable fidelity thus defining the overall location, geometry, and internal structure of the fault zone as well as the affected lithologies. Our results indicate that the city is constructed on a ~20 m thick surficial layer consisting of poorly consolidated, highly porous, water-logged pumice. This soft layer is likely to amplify seismic waves and to liquefy upon moderate to strong ground shaking. The electrical conductivity as well as the major element chemistry of the groundwater provides evidence to suggest that the local aquifer might, at least in part, be fed by water rising along the fault. Therefore, the potential threat posed by this fault splay may not be limited to its seismic activity per se, but could be compounded its potential propensity to enhance seismic site effects by injecting water into the soft surficial sediments. The results of this study provide the basis for a rigorous analysis of seismic hazard and sustainable development of San Miguel Uspantán and illustrate the potential of ERT surveying for paleoseismic studies. 相似文献
19.
Beatriz Santamaria William H. J. Strosnider Maria R. Apaza Quispe Robert W. Nairn 《Environmental Earth Sciences》2014,72(3):731-741
Vertical flow cells (VFCs) are key components of passive acid mine drainage (AMD) treatment systems and require organic substrates that create anaerobic conditions and encourage bacterial sulfate reduction. In the high elevation desert of Potosí, Bolivia, the low productivity landscape limits the availability of sustainable and economical organic substrates. Locally available brewery waste, llama manure, and cow manure were evaluated as potential VFC substrates in a preliminary laboratory fed-batch study to assist in passive treatment system design. Two abandoned AMD discharges were collected from Cerro Rico de Potosí. Discharge A had an initial pH of 2.96, specific conductance of 3.31 mS/cm, and acidity of 1,350 mg/L as CaCO3 equivalent. Discharge B had an initial pH of 3.85, specific conductance of 1.87 mS/cm, and acidity of 1,000 mg/L as CaCO3 equivalent. Triplicate fed-batch reactors were set up in 1-L cubitainers with each potential substrate exposed to each AMD, yielding a total of 18 reactors exposed for 9 days and sampled two times for anions and dissolved metals. Cow manure reactors exhibited the greatest pH and alkalinity increases. Cd, Co, Fe, Mn, Ni, Pb, and Zn decreased in all reactors. SO4 concentrations only decreased in brewery waste reactors. However, SO4 reducing bacteria was higher for cow manure reactors. Results suggest that llama and cow manure are the more labile substrates, with llama manure being the most affordable. Brewery waste could be a suitable less-labile long-term substrate amendment. However, longer-term studies are needed to determine the optimum VFC substrate mixture in this unique circumstance. 相似文献
20.
We present results obtained for Epinal (H5), an ordinary chondrite meteorite, irradiated with 60 keV Ar++ ions, simulating solar wind heavy particle irradiation. Bidirectional reflectance spectra (0.3-2.67 μm) measured after irradiating Epinal samples with different ion fluences exhibit a progressive reddening that is similar to the spread of spectra observed for S-type near-Earth asteroids. The timescales for inducing the same effects in space as those obtained in laboratory are estimated to be 104-106 yr. These results suggest irradiation by heavy ions may be a very efficient weathering process in near-Earth space. 相似文献