Environmental controls on the development of Mississippian microbial carbonate mounds and platform limestones in southern Montagne Noire (France)     

Pedro Czar  Alain Izart  Ian D. Somerville  Markus Aretz  Ismael Coronado  Daniel Vachard 《Sedimentology》2019,66(6):2392-2424

Late Mississippian carbonates in southern Montagne Noire are dominantly domical to laterally‐accreted microbial mounds in some formations, as well as stratiform microbial limestones occurring in hundreds of olistoliths within a flysch basin, constituting pieces of a giant puzzle that are used to help reconstruct a platform in a region that is no longer preserved. Petrographic data of limestone samples from 14 continuous long sections of olistoliths have been analyzed statistically, using multivariate clustering (Q‐mode) of the components/matrix/cement and canonical correspondence analysis that allow the reconstruction of the environmental parameters of carbonate microbial communities in space and time. Clustering analysis separated microbial and non‐microbial facies. The calculation of indices along the various axes from canonical correspondence analysis allows recognition of the controlling factors of the mounds and microbial growth as being turbidity, light penetration, bathymetry and storms. Turbidity and light penetration are the primary factors controlling the morphology of the microbial limestones. Representation of the light penetration and bathymetry indices on the stratigraphical sections defines two vertical environmental gradients. Light penetration can be subdivided into euphotic, euphotic–dysphotic and dysphotic‐aphotic conditions. The representation of the bathymetry allows the subdivision of samples into a deeper outer ramp, external mid‐ramp and internal mid‐ramp. The curve distance from the section base = f (index) suggests a cyclicity for the platform that cannot be compared with the onlap curve defined from other cratonic areas (Moscow Basin), and thus the cyclic succession of the Montagne Noire is interpreted to have been mostly tectonically‐controlled. Integration of the data allowed the reconstruction of the original Mississippian carbonate platform, where, up to the Mikhailovian, it appears to correspond to a platform morphology, with narrow shallow water facies and wide turbiditic systems, whereas the width of shallow‐water settings expanded during the Venevian to the Protvian, forming a ramp or distally‐steepened ramp with widespread microbial limestones.  相似文献   

Evaluation of the effect of water management interventions on water level of Gaza coastal aquifer     

Mazen Abualtayef  Ghada Abdel Rahman  Ismael Snounu  Khalid Qahman  Hasan Sirhan  Ahmed Khaled Seif 《Arabian Journal of Geosciences》2017,10(24):555

Gaza coastal aquifer (GCA) is the most precious natural source where it is the only source of water for different uses. Groundwater crisis in Gaza includes two major folds: shortage of water supply and contamination. The extraction of groundwater currently exceeds the aquifer recharge rate. As a result, the groundwater level is falling continuously leading severely deterioration of GCA. The main objective of this study is to analyze and evaluate the current and proposed water resources management plans and their effect on the water level of GCA. In this respect, the available quantities of rainfall that could be harvested and infiltrated from different types of land-use based on existing and planned situations are studied using GIS tool and numerical models for GCA using V-MODFLOW environment for simulating four scenarios: (i) existing management practice (no action scenario), (ii) proposed Palestinian Water Authority (PWA) stormwater infiltration plan, (iii) proposed Gaza Emergency Technical Assistance Program (GETAP) interventions, and (iv) combination between second and third scenarios. The management scenarios were tested with the calibrated flow model for the target period between 2016 and 2040. The simulation results of existing management practice scenario show that there are several depression zones in Gaza Strip; in southern part from ??18 to ??24 m MSL in 2020 and 2040, in the northern part from ??7 to ??12 m MSL in 2020 and 2040, and in the middle regions experienced a small decline in groundwater level. The simulation results of proposed PWA scenario indicate similar depression zones as per first scenario but with good enhancement of water level, ??17 to ??18 m MSL in the southern part and ??3 to ??6 m MSL in the northern part in 2020 and 2040, respectively. The simulation results of GETAP intervention scenario show a positive impact on groundwater level. The results of fourth scenario show good enhancement of water level, in which the water level in the northern part ranges from +?3 to +?6 m MSL in 2020 and 2040, while in the south part ranges from ??15 to +?4 MSL in 2020 and 2040.  相似文献   

Particulate matter geochemistry of a highly industrialized region in the Caribbean:Basis for future toxicological studies     

Luis F.O.Silva  Ismael L.Schneider  Paulo Artaxo  Yuleisy Núñez-Blanco  Diana Pinto  Érico M.M.Flores  Leandro Gómez-Plata  Omar Ramírez  Guilherme L.Dotto 《地学前缘(英文版)》2022,(1):376-387

Air pollution has become an important issue,especially in Caribbean urban areas,and,particulate matter(PM)emitted by different natural and anthropogenic sources causes environmental and health issues.In this work,we studied the concentrations of PM₁₀ and PM_2.5 sources in an industrial and port urban area in the Caribbean region of Colombia.PM samples were collected within 48-h periods between April and October 2018 by using a Partisol 2000 i-D sampler.Elemental geochemical characterization was performed by X-ray fluorescence(XRF)analysis.Further,ionic species and black carbon(BC)were quantified by ion chromatography and reflectance spectroscopy,respectively.Using the Positive Matrix Factorization(PMF)receptor model,the contributions of PM sources were quantified.The average concentration of PM₁₀ was 46.6±16.2μg/m³,with high concentrations of Cl and Ca.For PM_2.5,the average concentration was 12.0±3.2μg/m³,and the most abundant components were BC,S,and Cl.The receptor model identified five sources for PM₁₀ and PM_2.5.For both fractions,the contributions of marine sea spray,re-suspended soil,and vehicular traffic were observed.In addition,PM_2.5 included two mixed sources were found to be fuel oil combustion with fertilizer industry emissions,and secondary aerosol sources with building construction emissions.Further,PM₁₀ was found to also include building construction emissions with re-suspended soil,and metallurgical industry emissions.These obtained geochemical atmospheric results are important for the implementation of strategies for the continuous improvement of the air quality of the Caribbean region.  相似文献   

Lead Removal from Aqueous Solution by Natural and Pretreated Zeolites     

Ismael S. Ismael  Ahmed Melegy  Tomas Kratochvíl 《Geotechnical and Geological Engineering》2012,30(1):253-262

Hazardous metal cations enter water through the natural geochemical route or from the industrial wastes. Their separation and removal can be achieved by adsorptive accumulation of the cations on a suitable adsorbent. In the present work, toxic Pb(II) ions are removed from water by accumulating it on the surface of natural zeolite in three different forms; one untreated and two treated samples, one sample treated with 2 M HCI solution and other is treated with 3 M NaOH solution. Natural zeolite is mainly composed of clinoptilolite, and mordenite, with amount of non-zeolite phase (smectite and illite) and C and CT opal. The adsorption experiments are carried out using a batch process in environments of different pH, initial Pb(II) concentration, interaction time and amount of zeolites. Treated zeolite samples show high exchange capacity for Pb(II) compared to untreated sample, however, acid-treated sample shows an exceedingly good exchange capacity. Equilibrium data fitted well with the Langmuir isotherm model with maximum adsorption capacity of 115, 126, and 132 mg g⁻¹ of untreated natural zeolites, alkali-treated zeolites and acid-treated zeolites respectively. The rates of adsorption were found to confirm to pseudo-first order kinetic with good correlation and the overall rate of lead ions uptake.  相似文献   

Manmade Vulnerability of the Cancun Beach System: The Case of Hurricane Wilma   总被引：1，自引：0，他引：1  

Rodolfo Silva Casarin  Gabriel Ruiz Martinez  Ismael Mariño‐Tapia  Gregorio Posada Vanegas  Edgar Mendoza Baldwin  Edgar Escalante Mancera 《洁净——土壤、空气、水》2012,40(9):911-919

Climate change and resultant coastal erosion and flooding have been the focus of many recent analyses. Often these studies overlook the effects of manmade modifications to the coastline which have reduced its resilience to storm events. In this investigation, we integrate previous reports, historical photo analysis, field work, and the application of numerical models to better understand the effects of Wilma, the most destructive hurricane to affect Cancun, Mexico. Huge waves (of significant height, >12 m), long mean wave periods (>12 s), devastating winds (>250 km/h), and powerful currents (>2 m/s) removed >7 million cubic meters of sand from the Cancun beach system, leaving 68% of the sub‐aerial beach as bedrock, and the rest considerably eroded. Numerical simulations show that the modifications to the barrier island imposed by tourist infrastructure have considerably increased the rigidity of the system, increasing the potential erosion of the beach under extreme conditions. If there were no structural barriers, a series of breaches could occur along the beach, allowing exchange of water and alleviating storm surge on other sections of the beach. If the effects caused by anthropogenic changes to Cancun are ignored, the analysis is inaccurate and misleading.  相似文献   

Hazardous elements and amorphous nanoparticles in historical estuary coal mining area     

Ana L.Duarte  Kátia DaBoit  Marcos L.S.Oliveira  Elba C.Teixeira  Ismael L.Schneider  Luis F.O.Silva 《地学前缘(英文版)》2019,10(3):927-939

In Brazil, intense coal exploitation activities have led to environmental deterioration, including soil mortification, water contamination, loss of ecosystem, and atmospheric contamination. In addition,considerable quantities of sulfur-rich residues are left behind in the mining area; these residues pose grave environmental issues as they undergo sulfide oxidation reactions. When sulfur oxides come in contact with water, extreme acid leachate is produced with great proportions of sulfate, and hazardous elements(HEs), which are identified as coal drainage(CMD). CMD is an environmental pollution challenge, particularly in countries with historic or active coal mines. To prevent CMD formation or its migration, the source must be controlled; however, this may not be feasible at many locations. In such scenarios, the mine water should be collected, treated, and discharged. In this study, data from 2005 to2010 was gathered on the geochemistry of 11 CMD discharges from ten different mines. There are several concerns and questions on the formation of nanominerals in mine acid drainage and on their reactions and interfaces. The detailed mineralogical and geochemical data presented in this paper were derived from previous studies on the coal mine areas in Brazil. Oxyhydroxides, sulfates, and nanoparticles in these areas possibly go through structural transformations depending on their size and formation conditions. The geochemistry of Fe-precipitates(such as jarosite, goethite, and hematite) existent in the CMD-generating coal areas and those that could be considered as a potential source of hazardous elements(HEs)(e.g., Cr) were also studied because these precipitates are relatively stable in extremely low pH conditions. To simplify and improve poorly ordered iron, strontium, and aluminum phase characterization, field emission scanning electron microscopy(FE-SEM), high-resolution transmission electron microscopy(HR-TEM), micro-Raman spectroscopy, and X-ray diffraction(XRD) and sequential extraction(SE) studies were executed on a set CMD samples from the Brazilian mines. This study aimed to investigate the role of both nanomineral and amorphous phase distribution throughout the reactive coal cleaning rejects profile and HEs removal from the water mine to provide holistic insights on the ecological risks posed by HEs, nanominerals, amorphous phases, and to assess sediments in complex environments such as estuaries.  相似文献   

Delayed yield. An exact quasi-three dimensional model for free-aquifers     

Ismael Herrera  Benito Chen 《Advances in water resources》1983,6(1):54-58

Quasi-three-dimensional models have been quite successful in the numerical treatment of leaky aquifers. Similar models are not available for free aquifers, except for Boulton's theory which can be properly interpreted as such. In the present paper a quasi-three-dimensional model of free surface flows is developed for free aquifers and waves. The zero-order approximation of this model yields Boulton's theory of delayed yield, elucidating in this manner the nature of the latter theory. The model presented here possesses numerical and theoretical possibilities which will be explored more thoroughly in further work.  相似文献   

Definition of Physical Height Systems for Telluric Planets and Moons     

Robert Tenzer  Ismael Foroughi  Lars E. Sjöberg  Mohammad Bagherbandi  Christian Hirt  Martin Pitoňák 《Surveys in Geophysics》2018,39(3):313-335

In planetary sciences, the geodetic (geometric) heights defined with respect to the reference surface (the sphere or the ellipsoid) or with respect to the center of the planet/moon are typically used for mapping topographic surface, compilation of global topographic models, detailed mapping of potential landing sites, and other space science and engineering purposes. Nevertheless, certain applications, such as studies of gravity-driven mass movements, require the physical heights to be defined with respect to the equipotential surface. Taking the analogy with terrestrial height systems, the realization of height systems for telluric planets and moons could be done by means of defining the orthometric and geoidal heights. In this case, however, the definition of the orthometric heights in principle differs. Whereas the terrestrial geoid is described as an equipotential surface that best approximates the mean sea level, such a definition for planets/moons is irrelevant in the absence of (liquid) global oceans. A more natural choice for planets and moons is to adopt the geoidal equipotential surface that closely approximates the geometric reference surface (the sphere or the ellipsoid). In this study, we address these aspects by proposing a more accurate approach for defining the orthometric heights for telluric planets and moons from available topographic and gravity models, while adopting the average crustal density in the absence of reliable crustal density models. In particular, we discuss a proper treatment of topographic masses in the context of gravimetric geoid determination. In numerical studies, we investigate differences between the geodetic and orthometric heights, represented by the geoidal heights, on Mercury, Venus, Mars, and Moon. Our results reveal that these differences are significant. The geoidal heights on Mercury vary from ? 132 to 166 m. On Venus, the geoidal heights are between ? 51 and 137 m with maxima on this planet at Atla Regio and Beta Regio. The largest geoid undulations between ? 747 and 1685 m were found on Mars, with the extreme positive geoidal heights under Olympus Mons in Tharsis region. Large variations in the geoidal geometry are also confirmed on the Moon, with the geoidal heights ranging from ? 298 to 461 m. For comparison, the terrestrial geoid undulations are mostly within ± 100 m. We also demonstrate that a commonly used method for computing the geoidal heights that disregards the differences between the gravity field outside and inside topographic masses yields relatively large errors. According to our estimates, these errors are ? 0.3/+ 3.4 m for Mercury, 0.0/+ 13.3 m for Venus, ? 1.4/+ 125.6 m for Mars, and ? 5.6/+ 45.2 m for the Moon.  相似文献   

Vertical physicochemical parameter distributions and health risk assessment for trace metals in water columns in eastern Lake Tanganyika,Tanzania     

SHEN Qiushi  ZHANG Lu  Ismael Aaron KIMIREI  WANG Zhaode  GAO Qun  CHEN Shuang  YU Cheng 《海洋湖沼学报（英文）》2019,(1):134-145

The vertical distributions of trace metals and physicochemical parameters in water columns in Kigoma Bay and Kungwe Bay in eastern Lake Tanganyika, Tanzania, were studied. The Al, Ba, Ca, Co,K, Mg, Mn, Mo, Na, Sn, Sr, and V concentrations were low and varied very little with depth. The toxic heavy metal(As, Cr, Cu, Ni, Pb, and Zn) concentrations were relatively high in the surface water, and the Cu, Ni, Pb, and Zn concentrations decreased with depth. Principal component and cluster analyses indicated that the metals in the lake had three main sources. Al, Ba, Ca, Co, Cu, Cr, Mn, Sr, Sn, and V were found to be geogenic; As, Cr, Cu, Mo, Ni, Pb, Sn and Zn anthropogenic; and As, Ca, Co, Mg, and Na biogenic.Human health risk assessments were performed, and it was found that trace metals in the water at most of the sampling sites would cause no potential adverse ef fects or non-carcinogenic health risks through dermal contact or ingestion. However, trace metals in surface water in Kungwe Bay could have certain adverse ef fects on human health through the ingestion pathway(the total hazard quotient for ingestion(ΣHQi ng)was 1.75(a value >1 was de?ned as possibly indicating adverse ef fects). The Pb HQi ng for surface water in Kungwe Bay was 1.50 and contributed >80% of the ΣHQ_(ing_, implying that Pb pollution is a water quality and safety problem that needs to be carefully monitored and the potential sources identi?ed.  相似文献   

Diatomaceous deposits of Fayium, Egypt; characterization and evaluation for industrial application   总被引：1，自引：0，他引：1  

M.S.HASSAN  I.A.IBRAHIM 《中国地球化学学报》1999,18(3):233-241

The Holocene lacustrine diatomaceous earth of Fayium,South West of Cairo,has been studied to define its minerals,chemistry,petrography and physical properties.Minerals were processed by way of calcination at 550℃ ,followed by acid leaching to reduce levels of mineral impurities.The diatomite is of biogenic opal A.with calcite as the main ganue mineral,quartz and clay minerals(smectite followed by kaolinite in abundance and a trace amount of illite).Silica in the diatomaceous earth accounts for about 63% on average.Positive correlation between CaO and CO2 indicates that Ca is present mainly as calcite.Al2O3,Fe2O3,MgO and K2O are attributed mainly to clay minerals.However,the physical properties of the diatomaceous earth as filter-aids and filler for paints and plastics are poor because of general high levels of impurities.The technological performances of the diatomaceous earth have been significantly improved owing to upgrading of diatoms through mineral processing trical.  相似文献