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1.
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   

2.
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   

3.
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   

4.
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   

5.
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   

6.
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   

7.
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   

8.
The present work reports on the isotopic characterization of rainfall and groundwater at Mt. Vesuvius. Values of δ 18O, monthly measured on rain samples collected during the period 2002–2004 in a rain-gauge network composed of 10 stations, were compared with meteorological and DEM data. Air temperature, controlled by the local orographic structure, was identified as the main factor influencing rain isotopic composition. Another important role is played by orographic clouds, whose condensation over the top of Mt. Vesuvius is responsible for anomalously high δ 18O values recorded in rain samples from the summit area of the volcanic edifice. A spatial model of rain isotopic composition, based on a 3D distribution of temperature derived by a 1 × 1 km DEM, was implemented and used for calculating the theoretical isotopic signature of seepage, further compared with data measured in the groundwater monitoring network. The analysis evidenced the role of local meteoric recharge as the main source feeding Mt. Vesuvius aquifers. The unique exception is the Olivella drainage gallery, located on the north-eastern flank of the volcanic edifice, whose isotopic composition is slightly more positive than the one expected for its altitude, likely caused by both evaporation processes and mixing with condensed hydrothermal vapor.  相似文献   

9.
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   

10.
Uranium mineralization in Madyalabodu area, Cuddapah district, Andhra Pradesh, is spatially related to chloritized and brecciated quartzite of the Gulcheru Formation in the immediate vicinity of E-W to ESE-WNW trending basic dyke. Chloritization transgresses the lithological boundaries. Whole-rock geochemical data indicate enrichment of MgO and Al2O3 coupled with depletion of SiO2, Na2O, K2O, CaO and TiO2 in the chlorite-rich zone. Fe2O3 and FeO do not vary significantly in the altered and the unaltered zones. Electron Probe Microanalysis (EPMA) data reveal that the chlorites in contact with uranium minerals are enriched in MgO and depleted in FeO than in the others. Considering the petrological evidence, geochemical signature and structural constraints, it appears that chlorite acted more as an adsorbent rather than as a reductant in facilitating uranium mineralization. Uraninite crystallized later from the uranium originally adsorbed on chlorites. Chloritization might also have facilitated mineralization through the generation of nascent hydrogen, H2S and lowering pH of uranium-bearing solution.  相似文献   

11.
Methods for external estimation of the accuracy of geodetic parameters (the coordinates of radio telescopes) based on VLBI observations are discussed. Time series of the distances between radio telescopes (baselines) provide the observational material for the analysis. It is shown that the generally accepted model for estimating the accuracy of geodetic results is based on unjustified assumptions, and does not adequately describe the results of geodetic observations. A more flexible parametrical model is proposed, which takes into account the non-uniformity in the accuracies with which geodetic parameters for different stations can be estimated, and more adequately describes the observational data. The evolution of the Svetloe-Badary and Zelenchuk-Badary baselines in 2007–2012 is analyzed in detail. The Badary VLBI station located near Irkutsk is moving away from the other two stations, located in the European part of Russia, at a rate of 3–4 mm/year.  相似文献   

12.
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   

13.
An investigation was carried out to compare the ability of two bacteria Pseudomonas aeruginosa PSA5 and Rhodococcus sp. NJ2 isolated from petroleum sludge for degradation of benzo(a)pyrene [B(a)P], a HMW PAH compound in MSM. During 25 days of incubation, 50 ppm B(a)P was degraded by 88 and 47 % by P. aeruginosa PSA5 and Rhodococcus sp. NJ2, respectively. Besides, involvement of different catabolic enzymes, that is, salicylate hydroxylase, 2-carboxybenzaldehyde dehydrogenase, catechol 1,2-dioxygenase and catechol 2,3-dioxygenase, was also examined to identify their differential role in B(a)P degradation. Among these enzymes, the highest induction of 2-carboxybenzaldehyde dehydrogenase (773.5 nmol mg?1 protein) was recorded in P. aeruginosa PSA5, while salicylate hydroxylase was highly expressed (839.6 nmol mg?1 protein) in Rhodococcus sp. NJ2. Both the bacteria were found biosurfactant (glycolipid) producing, and role of biosurfactant in PAH degradation was also ascertained by reduced surface tension, higher emulsification index and increased cell surface hydrophobicity.  相似文献   

14.
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   

15.
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16.
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   

17.
This paper uses results from the National Oceanic and Atmospheric Administration’s National Status and Trends Program (NS&T) to place the environmental quality of Long Island Sound in a broader perspective. It compares levels of contaminants in blue mussels from ten Long Island Sound sites and in sediments from seven Long Island Sound sites with concentrations in the same media at 87 and 221 other sites, respectively, where comparable samples were obtained. In sediments, the levels of both trace metals and organic contaminants tend to be relatively high for Long Island Sound sites. This is especially true for five of the twelve metals (silver, cadmium, copper, lead, and zinc) and for five of six categories of organic contaminants (total chlordane, low molecular weight polycyclic aromatic hydrocarbons (PAHs), high molecular weight PAHs, total polychlorinated biphenyls, and total dichlorodiphenyltrichloroethanes). In mussels, the organic contaminant categories exhibit relatively high levels, but this is not true for most of the metals. In fact, four of the metals—arsenic, mercury, selenium, and zinc—show evidence of relatively low levels in mussels from Long Island Sound compared to other NS&T locations.  相似文献   

18.
The BASINS model, developed by the United States EPA, is a popular simulation tool for predicting watershed responses, such as runoff, pollution exports, and water quality. It requires large amounts of data to set parameters. Many studies state that model input is a major source of model uncertainty. Thus, improvements to the quality and completeness of the data will improve the certainty of the model. The objective of this study is to discuss the effects of spatial data, including digital elevation models (DEMs) and spatial rainfall records, on predictions of runoff from the BASINS model. The result shows that both DEMs and rainfall data can significantly influence peak flow and runoff volume. Rainfall input has more influence on the curve shape of hydrograph than DEM resolution. DEM resolution can have more impact on peak flow predictions than rainfall input. Because the model uncertainties from DEMs and rainfall records influence each other, the prediction error does not always decrease when DEM resolution increases. The present results show that the BASINS model produces reliable answers in the case area when the grid size is less than 100 m × 100 m and the precipitation records from the Bihu Rainfall Station are correct and complete.  相似文献   

19.
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   

20.
Effects of land use changes on soil erosion in a fast developing area   总被引：1，自引：0，他引：1  
Land use changes extensively affect soil erosion, which is a great environmental concern. To evaluate the effect of land use change on soil erosion in fast economic developing areas, we studied land use changes of Guangdong, China, from 2002 to 2009 using remote sensing and estimated soil erosion using the Universal Soil Loss Equation. We calculated the areas and percentage of each land use type under different erosion intensity and analyzed soil erosion changes caused by transitions of land use types. In addition, the impact of land use change on soil erosion in different river catchments was studied. Our results show that forest and wasteland land conversions induce substantial soil erosion, while transition from wasteland to forest retards soil loss. This suggests that vegetation cover changes significantly influence soil erosion. Any conversion to wasteland causes soil erosion, whereas expansion of forests and orchards mitigates it. The most significant increase in soil erosion from 2002 to 2009 was found in the Beijiang catchment corresponding to the transition from forest/orchard to built-up and wasteland. Soil erosion in the Xijiang catchment accelerated in this period due to the enormous reduction in orchard land. In Hanjiang catchment, erosion was alleviated and vegetation coverage greatly expanded owing to considerable transitions from wasteland and cropland to orchards. Field investigations validated our estimations and proved the applicability of this method. Measures including protecting vegetation, strict control of mining as well as reasonable urban planning should be taken to prevent successive soil erosion.  相似文献   

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