Pollution vulnerability of the Quaternary aquifer near Cairo, Egypt, as indicated by isotopes and hydrochemistry   总被引：2，自引：1，他引：2  

M. Sadek  Abd S. El-Samie 《Hydrogeology Journal》2001,9(3):273-281

The present study was conducted to delineate the pollution vulnerability of the Quaternary aquifer in two areas, Imbaba and Shobra El-Khima, near Cairo, Egypt. Environmental isotopes combined with hydrochemistry were used for this purpose. The groundwater in the Imbaba area (average total dissolved solids about 900 mg/L; sodium/chloride, sulfate, and bicarbonate water types) is more mineralized than groundwater in the Shobra El-Khima area (average total dissolved solids 500 mg/L; calcium and sodium/bicarbonate water type). A high nitrate content and significant mineralization in the groundwater are probably due to contamination of recharge to the aquifer by irrigation drainage, deteriorated sewage networks, and septic tanks. The deuterium and oxygen-18 compositions of the groundwater are depleted compared to Nile River water, which is the main source of aquifer recharge. This less isotopically enriched water probably represents older Nile water recharge that flooded the region before construction of the Aswan High Dam in 1963, or it is a mixture of a young water and originally deposited paleowater that was in deeper horizons at a time of cooler and more humid climate. Intensive pumping has moved the paleowater higher in the aquifer. Groundwater in the Shobra El-Khima area has higher residence time, based on the tritium concentration, than groundwater in the Imbaba area. The percentage of the isotopically depleted water equals 75% in the Shobra El-Khima and 35% in Imbaba, and the thickness of the clay cap above the aquifer is 38 m in Shobra El-Khima and 20 m in Imbaba. These factors are indicative of the rate of recharge to the aquifer and were used to evaluate the pollution vulnerability in the two areas. Electronic Publication  相似文献   

Covariations in oceanic dimethyl sulfide,its oxidation products and rain acidity at Amsterdam Island in the Southern Indian Ocean   总被引：5，自引：0，他引：5  

B. C. Nguyen  N. Mihalopoulos  J. P. Putaud  A. Gaudry  L. Gallet  W. C. Keene  J. N. Galloway 《Journal of Atmospheric Chemistry》1992,15(1):39-53

Simultaneous measurements of rain acidity and dimethyl sulfide (DMS) at the ocean surface and in the atmosphere were performed at Amsterdam Island over a 4 year period. During the last 2 years, measurements of sulfur dioxide (SO₂) in the atmosphere and of methane sulfonic acid (MSA) and non-sea-salt-sulfate (nss-SO₄ ^2-) in rainwater were also performed. Covariations are observed between the oceanic and atmospheric DMS concentrations, atmospheric SO₂ concentrations, wet deposition of MSA, nss-SO₄ ^2-, and rain acidity. A comparable summer to winter ratio of DMS and SO₂ in the atmosphere and MSA in precipitation were also observed. From the chemical composition of precipitation we estimate that DMS oxidation products contribute approximately 40% of the rain acidity. If we consider the acidity in excess, then DMS oxidation products contribute about 55%.  相似文献   

Migration and contamination of major and trace elements in groundwater of Madras city,India     

R. Ramesh  K. Shiv Kumar  S. Eswaramoorthi  G. R. Purvaja 《Environmental Geology》1995,25(2):126-136

Groundwater samples collected from both open and bore wells in an area of about 270 km² from Madras City, India, have been analyzed for major ions (HCO₃, Cl, Si, Na, Ca, and Mg) and trace elements (As, Se, B, V, Cr, Fe, Co, Pb, Cu, Zn, Cd, Mn, Ni, Mo, and Ba). The study reveals that the quality of potable water has deteriorated to a large extent. Seawater intrusion into the aquifer has been observed in nearly 50 percent of the study area. The toxic elements (As and Se) have already exceeded the maximum permissible limits of drinking water in almost the entire city. A positive correlation of As and Se with other toxic metals such as V, Cr, Fe, B, etc., indicates that all these elements are anthropogenic in origin. Applying multivariate analysis, the source for trace elements in groundwater has been grouped into two major factors: pollution and mobilization factors. The groundwater in the study area is largely contaminated by organic effluents and reflects the intensity of pollution caused by the overlying soil sediment and rapid infiltration of the pollutants.  相似文献   

离子色谱法测定五氧化二铌和五氧化二钽中痕量氟氯和硫酸根离子的前处理方法     

刘肖 滕曼蔡亚岐  牟世芬 《岩矿测试》2006,25(4):319-322

采用马弗炉将样品与NaOH混合进行熔融煅烧，热去离子水提取、离心、稀释后过OnGuard Ⅱ H柱和过滤膜进行前处理，抑制型电导离子色谱法检测，测定了Ta2O5和Nb2O5的氟离子、氯离子和硫酸根离子。该方法对三种被测阴离子的检测限（s／N=3）在0．15～0．70μg／g（以固体样品实际浓度计）或0．136～0．623μg／L（以溶液浓度计），标准曲线线性范围均在两个数量级以上，方法的精密度（RSD，n=7）小于5．46％，回收率为88％～106％，具有灵敏度高、选择性好、重现性佳、对环境友好等特点，用于实际样品的检测，结果令人满意。  相似文献   

A stochastic model of surface contaminant releases to support assessment of site contamination at a former industrial site     

R. Mackay  J.A. Morakinyo 《Stochastic Environmental Research and Risk Assessment (SERRA)》2006,20(3):213-222

An industrial site is usually contaminated by accidental (and occasionally intentional) releases of pollutants to the environment from various operations carried out on that site. Consequently, the pattern of contamination created during the life of the site depends in part, at least, on the pattern of operations. Thus, the assessment of the pattern of contamination over the site should be improved: if it is possible to identify the pattern of operations on the site, the duration of the different activities and the perceived likelihood of releases from the different operations. A stochastic model has been developed that can be used to simulate alternative realizations of contaminant releases (duration, extent and timing). The model employs release zones associated with particular activities or groups of activities on the site and the areas of each of the zones may be independent or overlapping. The period of activity in each zone is obtained from the site records, while the likelihood and extent of contamination in each zone is inferred from an analysis of the contamination data obtained by point sampling. The form of the model, the method of inference of the model parameter values from the site data and the application of the model to the study site are presented. The release model has been developed as part of a suite of stochastic models for site ground contamination analysis. The stochastic soil and transport models and the application of the integrated modelling system are described in separate papers.  相似文献   

Sulfate Attack on Concrete in an Inland Salt Lake Environment   总被引：2，自引：0，他引：2  

董荣珍马保国  贺行洋朱洪波 卫军 《中国地质大学学报(英文版)》2006,17(4):342-348

INTRODUCTIONSulfate attack is one of the reasons for concretestructures deteriorating earlier than usual,thusshowing poor durability.The SO42-from the sur-rounding environment such as ocean,saline,groundwater,and even the concrete itself,reacts with thehydration products of cement,whichleads to the de-terioration of the concrete(Li et al.,2000;Kang,1995;Neville,1983;Samarai,1976).The deteriora-tionincludes three processes:the external swelling,cracking,peeling,and disjointing caused by …  相似文献   

Mineralogy and heavy metal content in sediments from Rio Gato,Carelmapu and Cucao,Southern Chile     

I. González  M. M. Jordán  T. Sanfeliu  M. Quiroz  C. de la Fuente 《Environmental Geology》2007,52(7):1243-1251

In southern Chile, with a mild and rainy climate, high levels of heavy metals have been detected in many gold placer deposits. Many of the contaminants pose risks to human life, and consequently damage the trofic chain in this environment. The study zones selected correspond to the handicraft gold-bearing sands of Rio Gato (Los Muermos), Carelmapu and Cucao. These are all located in the X Region of “Los Lagos” in Chile. The type of methodology used in the characterization of the associated mineralization consists of testing each representative sample with a grain size distribution, statistical parameter analysis and a mineralogical analysis, using a binocular magnifying glass, a petrographic microscope, XRD and SEM/EDX. The chemical composition was defined by means of X ray fluorescence and micro-chemical analysis. The results of the study about sediments in southern Chile are presented. The major concentrations of heavy minerals are generally located in areas of dynamic river energy. In the samples, more than 70% of the heavy minerals were distributed among grain sizes corresponding to thin sand with good grain selection (meshes of 0.25–0.06 mm). The main mineral phases present in the analysed samples were gold, zircon, olivine, ilmenite, hornblende, hypersthene, hematite, garnet, chromite, chlorite, augite, amphibolitic-epidote, etc. The main heavy metals found as a result of the study were mercury, lead, cadmium, chrome, tellurium, indium, zinc, cobalt, copper, platinum, gold, etc., and as well some less common elements like cerium, praseodymium, gadolinium, neodymium, samarium and lanthanum. This research work is only a starting point for carrying out a risk probability mapping of heavy metals and the mineralogy of the Cucao, Carelmapu and Rio Gato gold-bearing sands.  相似文献   

Magmatic History of Somma-Vesuvius on the Basis of New Geochemical and Isotopic Data from a Deep Borehole (Camaldoli della Torre)   总被引：3，自引：0，他引：3  

Di Renzo  V.; Di Vito  M. A.; Arienzo  I.; Carandente  A.; Civetta  L.; D'antonio  M.; Giordano  F.; Orsi  G.; Tonarini  S. 《Journal of Petrology》2007,48(4):753-784

A continuous-coring borehole recently drilled at Camaldoli dellaTorre on the southern slopes of Somma–Vesuvius providesconstraints on the volcanic and magmatic history of the Vesuvianvolcanic area since c. 126 ka BP. The cored sequence includesvolcanic units, defined on stratigraphical, sedimentological,petrological and geochemical grounds, emitted from both localand distal vents. Some of these units are of known age, suchas one Phlegraean pre-Campanian Ignimbrite, Campanian Ignimbrite(39 ka), Neapolitan Yellow Tuff (14· 9 ka) and VesuvianPlinian deposits, which helps to constrain the relative ageof the other units. The main rock types encountered are shoshonite,phonotephrite, latite, trachyte and phonolite. The sequenceincludes, from the base upwards: a thick succession of pyroclasticunits emplaced between 126 and 39 ka, most of them attributedto eruptions that occurred in the Phlegraean area; the CampanianIgnimbrite; the products of a local tuff cone formed between39 ka and the deposition of the products of the earliest activityof the Mt. Somma volcano; the products of the Somma–Vesuviusvolcano, which include from the base upwards a thick sequenceof lavas, pyroclastic rocks and the products of a local spattercone dated between 3· 7 ka and AD 79. The data obtainedfrom the study of the borehole show that, before the CampanianIgnimbrite eruption, low-energy explosive volcanism took placein the Vesuvian area, whereas mostly high-energy explosive eruptionscharacterized the Campi Flegrei activity. In the Vesuvian area,Campanian Ignimbrite deposition was followed by the eruptionof a local tuff cone and a long repose time, which predatedthe formation of the Mt. Somma edifice. Since 18· 3 ka(Pomici di Base eruption) the activity of Somma–Vesuviusbecame mostly explosive with rare lava effusions. The shallowestcored deposits belong to the Camaldoli della Torre cone, formedbetween the Pomici di Avellino and Pomici di Pompei eruptions(3· 7 ka–AD 79). New geochemical and Sr–Nd–Pb–B-isotopicdata on samples from the drilled core, together with those availablefrom the literature, allow us to further distinguish the volcanicrocks as a function of both their provenance (i.e. Phlegraeanor Vesuvian areas) and age, and to identify different magmaticprocesses acting through time in the Vesuvian mantle source(s)and during magma ascent towards the surface. Isotopically distinctmagmas, rising from a mantle source variably contaminated byslab-derived components, stagnated at mid-crustal depths (8–10km below sea level) where magmas differentiated and were probablycontaminated. Contamination occurred either with Hercynian continentalcrust, mostly during the oldest stages of Vesuvian activity(from 39 to 16 ka), or with Mesozoic limestone, mostly duringrecent Vesuvian activity. Energy constrained assimilation andfractional crystallization (EC-AFC) modelling results show thatcontamination with Hercynian crust probably occurred duringdifferentiation from shoshonite to latite. Contamination withlimestone, which is not well constrained with the availabledata, might have occurred only during the transition from shoshoniteto tephrite. From the ‘deep’ reservoir, magmas rosetowards a series of shallow reservoirs, in which they differentiatedfurther, mixed, and fed volcanic activity. KEY WORDS: Somma–Vesuvius; crustal contamination; source heterogeneity; radiogenic and stable isotopes; magmatic system  相似文献   

Early-indicator signals of groundwater contamination: the case of seawater encroachment   总被引：4，自引：0，他引：4  

A. J. Melloul  L. C. Goldenberg 《Environmental Geology》1998,33(4):279-288

 An early indication of groundwater contamination occurs when pollutant concentrations start to fluctuate and exceed background values of ambient fresh groundwater. An analysis of a characteristic situation of this type uses data from Israel's coastal phreatic granular aquifer. The pollutant is generally seawater, and the contamination process involves replacement of freshwater by encroaching sea- or other saltwater, a process augmented by human activity. The contamination process involves three stages: (1) groundwater composition remains relatively stable with small salinity content; (2) small salinity changes are perceptible with reversible fluctuations; and (3) salinity concentration increases at a sharply higher rate. The second stage is a useful early-indicator signal of contamination. Early-indicator signals of groundwater pollutant concentrations involve "minor" fluctuations in water chemistry at the advent of the contamination process. The intensity and magnitude of such a salinization/pollution process at any given location depends upon lithologic matrix, aquifer heterogeneity, and resultant flow domain characteristics, as well as contaminant properties. If such "signs" are detected at a sufficiently early stage, appropriate management steps may be taken to rectify further seawater and/or saltwater encroachment. Received: 23 July 1996 · Accepted: 25 June 1997  相似文献   

A Three-Dimensional Global Model Study of Carbonyl Sulfide in the Troposphere and the Lower Stratosphere   总被引：4，自引：0，他引：4  

Erik Kjellström 《Journal of Atmospheric Chemistry》1998,29(2):151-177

Global distributions of carbonyl sulfide and carbon disulfide have been calculated with a three-dimensional global model of the atmospheric general circulation (ECHAM). The model calculates a global sink strength for carbonyl sulfide of 0.3 Tg S yr^-1, with vegetation uptake being the largest sink. With this sink strength, the sources have to be close to the lower limit of the present estimate in the literature. The calculated mixing ratios are higher in the Southern Hemisphere than in the Northern Hemisphere. This interhemispheric gradient is the opposite of what is observed demonstrating that the present knowledge of the distribution of sinks and sources is not fully adequate. The model calculations support the idea that the open oceans could act as a net sink of carbonyl sulfide. The calculated stratospheric photolysis of carbonyl sulfide constitutes about 4% of the total sink of carbonyl sulfide. A stratospheric production of sulfate from carbonyl sulfide of 0.013 Tg S yr^-1 is obtained, which is 3 to 12 times less than what is needed to maintain the stratospheric sulfate aerosol layer. Although these results are associated with uncertainties, due to the low upper boundary and coarse vertical resolution of the model, they support recent findings of a low stratospheric production of sulfate from carbonyl sulfide. Instead, sulfur dioxide transported from the troposphere is calculated to be the most important precursor for the stratospheric sulfate aerosol layer.  相似文献