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1.
We implement a hierarchical Bayesian spatiotemporal (HBST) model to forecast the daily trapped particle flux distribution over the South Atlantic Anomaly (SAA) region. The National Oceanic and Atmospheric Administration (NOAA)-15 data from 1–30 March 2008 with particle energies as >30 keV (mep0e1) and >300 keV (mep0e3) for electrons and 80–240 keV (mep0p2) and > 6900 keV (mep0p6) for protons were used as the model input to forecast the flux values on 31 March 2008. Data were transformed into logarithmic values and gridded in a 5°×5° longitude and latitude size to fulfill the modelling precondition. A Monte Carlo Markov chain (MCMC) was then performed to solve the HBST Gaussian Process (GP) model by using the Gibbs sampling method. The result for this model was interpolated by a Kriging technique to achieve the whole distribution figure over the SAA region. Statistical results of the root mean square error (RMSE), mean absolute percentage error (MAPE), and bias (BIAS) showed a good indicator of the HBST method. The statistical validation also indicated the high variability of particle flux values in the SAA core area. The visual validation showed a powerful combination of HBST-GP model with Kriging interpolation technique. The Kriging also produced a good quality of the distribution map of particle flux over the SAA region as indicated by its small variance value. This suggests that the model can be applied in the development of a Low Earth Orbit (LEO)-Equatorial satellite for monitoring trapped particle radiation hazard.  相似文献   

2.
Phanerochaete chrysosporium, a white rot basidiomycete, was immobilized over Luffa cylindrica sponge discs, treated with 0.1 N HCl and its potentiality for the removal of hexavalent chromium [Cr(VI)] from water was investigated in both batch and in up-flow fixed-bed bioreactor. The acid treatment of biomass increased the uptake capacity and percentage removal of Cr(VI) from 33.5 to 46.5 mg g?1 and 67 to 92 %, respectively. Maximum uptake of Cr(VI) was achieved at pH 2, temperature 40 °C after 100 min of contact time. The Cr(VI) sorption on the biomass was better explained by Langmuir isotherm. Thermodynamic studies indicated that the process was spontaneous and endothermic. Sorption kinetic study showed that pseudo-second-order model best correlates the Cr(VI) sorption on the biomass as compare to pseudo-first-order kinetic model. The performance of fixed-bed bioreactor was evaluated at different bed heights (5, 15 and 25 cm) and flow rates (1.66, 4.98 and 8.33 mL min?1) by using bed depth service time model. Response surface methodology statistical method was applied for optimizing the process parameters. FTIR analysis showed that amino groups were mainly involved in adsorption of Cr(VI).  相似文献   

3.
In many applications in flows through porous media, one needs to determine the properties of subsurface to detect, monitor, or predict the actions of natural or induced forces. Here, we focus on two important subsurface properties: rock permeability and porosity. A Bayesian approach using a Markov Chain Monte Carlo (MCMC) algorithm is well suited for reconstructing the spatial distribution of permeability and porosity, and quantifying associated uncertainty in these properties. A crucial step in this approach is the computation of a likelihood function, which involves solving a possibly nonlinear system of partial differential equations. The computation time for the likelihood function limits the number of MCMC iterations that can be performed in a practical period of time. This affects the consistency of the posterior distribution of permeability and porosity obtained by MCMC exploration. To speed-up the posterior exploration, we can use a prefetching technique, which relies on the fact that multiple likelihoods of possible states into the future in an MCMC chain can be computed ahead of time. In this paper, we show that the prefetching technique implemented on multiple processors can make the Bayesian approach computationally tractable for subsurface characterization and prediction of porous media flows.  相似文献   

4.
Assemblages of ichthyofauna of shallow inshore habitats along Californía’s central coast are described in terms of species composition, abundance, and life-style categories. A total of 22,334 fishes from 65 species and 27 families was collected with otter trawls at six sites in the main channel and tidal creeks of Elkhorn Slough, a tidal embayment and seasonal estuary, and two nearshore ocean stations in Monterey Bay during 44 months between August 1974 and June 1980. Greater than 90% of the catch comprised 10 species. The four dominant species,Cymatogaster aggregata, Leptocottus armatus, Phanerodon furcatus, andEmbiotoca jacksoni, occurred during most or all seasons and were classified as residents or partial residents. Several abundant species were marine immigrants that seasonally use the slough as spawning and nursery grounds; this resulted in higher abundance and species richness during summer. Species collected during winter largely were slough residents. Species compsosition and richness varied with distance from the slough entrance. The ocean assemblage was most different, and its similarity to other stations decreased progressively with distance inland and into the tidal creeks. During our study, 5,074 fishes were collected by beach seine in Bennett Slough, a remote shallow marsh basin adjacent to the entrance of Elkhorn Slough. Species richness was relatively low and three euryhaline species accounted for >80% of the total catch. The species assemblage was most similar to those at the tidal creek and most shallow stations of Elkhorn Slough. Resident species numerically dominated assemblages in Bennett Slough and the most inland areas of Elkhorn Slough. The high relative abundance of marine-related fishes (classified as marine, marine immigrant, and partial resident), entering Elkhorn Slough early in life or as spawning adults indicates the importance of this habitat to nearshore fish assemblages.  相似文献   

5.
Besshi-type volcanogenic Cu-Zn deposits in the Scandinavian Caledonides are hosted by Ordovician metabasalts and clastic sediments of the Storen, Fundsjo and Sulitjelma groups. The basalts are transitional between T-MORB and marginal basin tholeiites in composition and are characterised by Nd and Pb isotopic compositions which overlap the more radiogenic values of Lower Palaeozoic MORB. These features, along with the intercalation of the basalts with tuffs and continentally derived sediments, indicate an epicontinental rift or marginal basin origin, possibly analogous to the present Red Sea and Gulf of Aden rifts. This implies the development of a restricted ocean basin in the north of Iapetus between the Laurentian and Baltoscandian microcontinents during the Cambrian and Early Ordovician.  相似文献   

6.
The maintenance of harbor waterways generates large amounts of dredged sediments which are often rich in coexisting organic and inorganic contaminants. Electrokinetic remediation treatments have recently been developed for the simultaneous removal of heavy metals and polycyclic aromatic hydrocarbons (PAHs), using various enhancing agents generally tested sequentially. In this study, different processing fluids were tested, alone or mixed, to improve the decontamination of aged model sediment contaminated with cadmium, lead, chromium, copper, zinc, and five PAHs. Nitric acid (NA) and citric acid (CA) were tested to avoid the formation of an alkaline front into the sediment and favor the metals removal, while an anionic surfactant [sodium dodecyl sulfate (SDS)] and a nonionic surfactant (Tween 20) were tested to solubilize and mobilize PAHs. Processing fluids were circulated under a constant voltage gradient of 1 V cm?1 for 10–14 days. NA showed an excellent potential to remove metals (76.8–99.9 % removal) and PAHs (70.3–89.7 % removal) in a single run. Besides, the mixture of Tween 20 and CA, more environmental friendly, could be considered as a relatively good processing fluid for the simultaneous removal of metals (10.3–90.8 % removal) and PAHs (53.6–61.6 % removal) from the fine-grained sediment, while SDS mixed to CA was not a good candidate for this purpose (0.1–65 % removal for metals and 34.1–41.0 % removal for PAHs).  相似文献   

7.
Nanohybrid of graphene oxide (GO) and azide-modified Fe3O4 nanoparticles (NPs) were fabricated using click reaction. First, Fe3O4 NPs were modified by 3-azidopropionic acid. Then, click-coupling of azide-modified Fe3O4 NPs with alkyne-functionalized GO was carried out in the presence of CuSO4·5H2O and sodium l-ascorbate at room temperature. The attachment of Fe3O4 NPs onto the graphene nanosheets was confirmed by Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy, thermogravimetric analysis, energy dispersive X-ray spectrometry and X-ray diffraction spectrometry. As the FTIR spectroscopy and energy dispersive X-ray spectrometry analysis showed, the final magnetic graphene nanosheets were also reduced by sodium ascorbate which is a merit for click-coupling reactions. The specific saturation magnetization of the Fe3O4-clicked GO was 44.3 emu g?1. The synthesized hybrid was used in the adsorption of methylene blue and congo red (CR). The adsorption capacities in the studied concentration range were 109.5 and 98.8 mg g?1 for methylene blue and CR, respectively.  相似文献   

8.
A mathematical model was developed to describe the reduction of Cr(VI) by Escherichia coli (E. coli) 33456 in a fixed biofilm reactor. A laboratory-scale column reactor was conducted to verify the model system. The batch kinetic tests were independently conducted to determine the biokinetic parameters used in the model simulation. With the assumed values of initial biofilm thickness (L f0), the mathematical model simulated well the experimental results for Cr(VI) effluent concentration, effluent concentration of suspended E. coli cells, and Cr(III) production. The concentration of suspended E. coli cells reached up to 1.2 mg cell/L while the thickness of attached E. coli cells was estimated to be 32.6 μm at a steady-state condition. At the steady state, the removal efficiency of Cr(VI) was about 92 % and the effluent concentration of Cr(III) was approximately 1.6 mg/L. The approaches presented in this study can be employed for the design of a pilot-scale or full-scale fixed biofilm reactor to treat Cr(VI)-containing wastewater.  相似文献   

9.
The last major eruption of La Soufrière volcano in Guadeloupe (Lesser Antilles) in 1976–1977 caused the mass evacuation of part of the population, whereby a total of 76,000 people were displaced for a period of 3–6 months. This evacuation has left a bitter memory among the inhabitants who believed that the political authorities of the time had not anticipated the possibility of an eruption crisis and that decisions were taken in haste. La Soufrière remains active, and future eruptions could once again lead to partial or even total evacuation of the population if there were a major Plinian eruption. This article offers an investigation of future evacuation procedures, questioning different aspects of Guadeloupe’s current territorial and social challenges (the multi-risk context, the reporting to the scientists and to the authorities, the importance of local solidarity). In order to do so, we used the Focus Group Discussion method, making it possible to identify resources and gaps in crisis management on the basis of previous event history.  相似文献   

10.
The first results of study of stability of diverse polycyclic aromatic hydrocarbons at around 7 GPa and 773–1073 K are reported. Experiments were carried out in hydraulic multi-anvil presses. The run products after quenching were analyzed using a method of matrix-assisted laser desorption-ionization (MALDI). The formation of polymers of starting matters was determined at 7 GPa and 773–883 K. The polymers are characterized by atomic masses up to 5000 Da, that are multiple by masses of starting matters. At higher temperatures (873–1073 K), the selected PAHs and their polymers become unstable. The decomposition temperature of PAHs and their polymers exclude their stability under Earth’s mantle conditions. The studies could be of great significance for the low-temperature near-surface geodynamics of small and large planetary bodies, which supposedly contain hydrocarbon compounds.  相似文献   

11.
Abundance, sources, and historical records of polycyclic aromatic hydrocarbons (PAHs) in sediment cores of three lakes located in northeast China were evaluated. One lake was located in a rural oil field area, one in an industrial urban oil field area, and the third in an urban industrialized area without oil field influence. Cores from each lake were divided into 1-cm sections, dated using 137Cs techniques, and 16 priority PAH compounds were measured. Total PAH concentrations were greater in industrial areas than in rural area, regardless of associated oil production. Only petroleum sources of PAHs were identified in lakes near oil fields between 1950s and 1980s, while sources of liquid fossil fuel combustion were persistently identified in the industrial urban lake. From 1990s to 2000s, PAH concentrations, especially high molecular weight PAHs, significantly increased in all lakes, which were consistent with the economic development in China, suggesting a change in energy use from wood burning and petroleum (oil) to liquid fossil fuel combustion. Environmental risk was low to moderate in sediments of the three lakes studied, and increases in high molecular weight PAHs during 1900s–2000s is a concern.  相似文献   

12.
Marine bacteria, Vibrio alginolyticus and Vibrio parahemolyticus isolated from sediments were evaluated for their ability as a consortia, to degrade polyvinyl alcohol-low linear density polyethylene (PVA-LLDPE)-blended plastic films in shake flask conditions at 120 rpm at 37 °C over 15 weeks. Results indicated that relatively 20 % decrease in tensile strength of the film could be achieved with 25 and 30 % blend of PVA in the PVA-LLDPE plastic film compared to other ratios. Micrographs obtained with scanning electron microscope showed visible cracks and grooves on the surface of the PVA-LLDPE blend film after 15 weeks of incubation with bacterial consortium. The decrease in tensile strength of the PVA-blended plastic films after treatment and the results of the scanning electron microscopic analysis evidence that the consortium could cause degradation of PVA-LLDPE plastic blends compared to suitable controls. This is the first report on polyvinyl alcohol degrading Vibrio sp. from marine sediments and its application in microbial degradation of polyvinyl alcohol-low linear density polyethylene plastic blends. The study indicated potential of marine benthic vibrios that have novel enzymes and unique characteristics for application in bioremediation and solid waste management particularly in handling synthetic polymers such as PVA-blended plastic films.  相似文献   

13.
Today, ground-based optical remote sensing (ORS) has become an intensively used method for quantifying pollutant or greenhouse gas emissions from point or area sources, and for the validation of airborne or satellite remote sensing data. In this study, we present the results of a release experiment using acetylene (C2H2) as a tracer gas, where three ORS techniques were simultaneously tested for two main purposes: (1) the detection of emission sources and (2) the quantification of release rates. Therefore, passive and active open-path Fourier transform infrared spectroscopy (OP-FTIR) and open-path tunable diode laser absorption spectroscopy (TDLAS) were applied and evaluated. The concentration results of the active ORS methods are compared to those estimated by a Lagrangian stochastic atmospheric dispersion model. Our results reveal that passive OP-FTIR is a valuable tool for the rapid detection and imaging of emission sources and the spatial tracer gas distribution; while with active OP-FTIR and TDLAS, C2H2 concentrations in the sub-ppm range could be quantified that correlated well with the concentration data obtained by our modeling approach.  相似文献   

14.
As a basis for eventual control of the vicious anthropophilic and ornithophilic simuliid females of the Marquesas Islands, a taxonomic revision of Polynesian Simuliidae is in progress. Cytotaxonomic studies reveal two simuliid species in Rarotonga, Cook Islands; nine species in Tahiti, Society Islands, and two in the Marquesas Islands. A cytophylogeny is now available. Polynesian Simuliidae are unique in possessing heterogametic females. A reconstructed phylogeny, based mainly on morphological character states of larvae and pupae, agrees well with the cytophylogeny. One of the new species which is closely related to Simulium oviceps Edwards has larvae with highly reduced, non-functional cephalic fans. Ages of the Polynesian islands are discussed in relation to possible dispersal of Simuliidae into Polynesia.  相似文献   

15.
The Khetri Copper Belt is well known because of its economically viable Cu deposits. In this region, there is a linear narrow zone following a major crustal fracture. Along this zone, due to hydrothermal activity and subsequent alteration, a new rock, albitite has formed. The study presents an account of the spectral analysis of Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) dataset for albitite mapping in the Khetri Copper Belt. Spectral angle mapper algorithm is applied on the ASTER data taking the ground sample reflectance spectra (VNIR–SWIR) and image derived spectra (TIR) as reference spectra. The albitite-classified areas are analyzed spatially and statistically to determine the extent of albitite zone in the study area. This research is to contribute to the better understanding of the spatial extent of the albitite zone which will assist in determining the potential for the mineralization in the area. The remote sensing approach of utilizing multichannel data offers the capability to resolve the key geological features of this geologically dynamic area.  相似文献   

16.
An exploration strategy for groundwater was established and followed in the northern Namibian Cuvelai-Etosha Basin (CEB). The data derived from transient electromagnetics, rotary-drilling, coring and sample investigation were used to refine stratigraphy and hydrostratigraphy, and to develop a 3D map of aquifers within the Cubango Megafan. The results have delineated three major aquifers. The newly found, deep-seated Ohangwena II Aquifer (KOH-2) has the potential of providing significant additional water to the water supply of northern Namibia and Angola. While near-surface aquifers carry predominantly brackish water, freshwater in the deep-seated aquifer is further extended and features good hydraulic properties. To date, only a small part of the hydrogeological potential of arid CEB has been explored and an extension of exploration is needed, including southern Angola. The combination of structural, sedimentological and hydrogeological approaches greatly advanced both the geological and hydrogeological understanding. With regard to the deep-seated aquifer, strict measures need to be applied to ensure that the water in the KOH-2 reservoir is exploited sustainably. Water control areas need to be established to ensure long-term preservation of this newly explored aquifer.  相似文献   

17.
Breaking tests on homogeneous earth-rock-fill dams destroyed by overtopping flow are presented. Two types of shear erosion are found: wetting shear erosion and quick shear erosion; the water level-discharge process is divided into “sharp rise and drop of flow” and “slow change of flow” types. Furthermore, overtopping break modes are divided into head-cut erosion and scour breaching mode (Mode 1), shear erosion and collapse breaching mode (Mode 2), and wetting shear erosion mode (Mode 3) based on the main failure types and their coupled mode during dam break. In Mode 1, the downstream slope encounters head-cut erosion at the onset of the breach and expands and undercuts gradually at the development stage; in Mode 2, the dam slope encounters rapid shear erosion and the downstream edge of the crest erodes quickly towards the upstream face at the onset of breach: the breach expands suddenly due to instability and collapse at both sides of the breach in its development stage; in Mode 3, the strength of the dam’s materials continuously decreases by wetting and erosion happens is localised at positions where wetting caused the most strength loss, no obvious breach was developed. Dam breaking time, dam-break flow process, and the maximum discharge flow varied for each breaking mode. Overtopping flow size, materials, height, and initial breach size of dam are important factors influencing breaking mode, by virtue of their changing the relative strength of the relationship between the critical shear stress of dam materials at the edge of the dam crest and the lower parts of its slope, and the given flow’s destruction capacity. Overtopping will cause different manifestations of damage to be exhibited, so modal classification is favourable for safety assessment and preparation of relevant protective measures for protection of earth-rock-fill dam against overtopping.  相似文献   

18.
Wetland delineation is commonly based on terrain unit, soil form, soil wetness and vegetation indicators which along with the shallow groundwater or proximate surface water are often absent in many ephemeral inland South African areas due to, for instance, prolonged dry periods (seasons to years) which mask these indicators, as well as disruption of surface materials due to construction, agricultural activities and field fires. Furthermore, many “wetlands” in South Africa comply with the four indicators, but the notable absent requirement for wetlands is missing, namely the shallow groundwater table, as many of these systems form in hillslope seeps, catenas or from perched water tables. A 200-m-long excavation through one such a system is being studied in Midrand (Gauteng, South Africa). The site is underlain by Lanseria Gneiss and is waterlogged after long and intense periods of intense rainfall. Frequent downslope soil profiling, horizon-specific laboratory analyses for grading and Atterberg Limits, X-Ray Diffraction and X-Ray Fluorescence Spectroscopy data are interpreted together with soil percolation tests to generate a conceptual model of the system. The results are discussed in terms of the need to consider these temporary systems that do not have a shallow groundwater table and that are not in direct contact with surface drainage features as a possible special type of wetlands, notably in arid regions where they play a very important role in biodiversity and should, therefore, be protected.  相似文献   

19.
Subsolidus phase relations on the join CaMgSi2O6-CaFe3+ AlSiO6-CaTiAl2O6 were studied by the ordinary quenching method at \(f_{O_2 } = 10^{ - 11} \) atm and 1,100°C. Crystalline phases encountered are clinopyroxeness (ss:solid solution) (Cpxss), melilite (Mel), perovskite (Pv), spinelss (Spss), magnetitess (Mtss) and anorthite (An). There is no Cpxss single phase field, and the following assemblages were found; Cpxss+Mel, Cpxss+Mel+Spss, Cpxss+Mel+Pv, Cpxss+Mel+Spss+Pv, Cpxss+Pv+Spss+An, Spss+Pv+Mel+An+Cpxss, Mel+Mtss+An+Spss+Cpxss+liquid and Mel+Mtss+An+Spss+Cpxss+Pv. Mössbauer spectral study revealed that Cpxss contains both Fe2+ and Fe3+ in the octahedral site, and it was confirmed that the CaFe3+ AlSiO6 content in the Cpxss at low \(f_{O_2 } \) is considerably less than that in the Cpxss crystallized in air, whereas the CaFe2+Si2O6 component increases. The maximum solubility of CaTlAl2O6 component in the Cpxss at low \(f_{O_2 } \) is higher than that in air. The decrease of CaFe3+ AlSiO6 in the Cpxss at low \(f_{O_2 } \) may cause increase of CaTial2O6 in the Cpxss.  相似文献   

20.
Augustine Tanle 《GeoJournal》2014,79(5):577-590
In Ghana, studies on migration and livelihoods are mostly limited to migrants’ places of origin. This paper therefore assesses livelihood status of permanent migrants resident in the Obuasi Municipality who hail from the northern parts of Ghana. The instrument used was a survey questionnaire and the respondents were both migrants and indigenes aged 18 years and above. The findings showed no significant differences between migrants and indigenes in ownership of assets and consumer durable goods and housing quality. However, the indigenes earned relatively higher than the migrants due to access to various forms of capital and the influence of institutional structures and processes. But to the migrants, their livelihood status has improved since they have built houses, educated their children, remitted relations at home and have acquired some consumer durable goods. Improvement in the livelihood status of migrants could induce further north–south migration. There is therefore the need for government and other stakeholders to bridge the gap of unequal socio-economic development between the northern and southern parts of the country.  相似文献   

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