Groundwater contamination with arsenic in Sherajdikhan,Bangladesh: geochemical and hydrological implications     

M. A. Halim  R. K. Majumder  S. A. Nessa  K. Oda  Y. Hiroshiro  B. B. Saha  S. M. Hassain  Sk. A. Latif  M. A. Islam  K. Jinno 《Environmental Geology》2009,58(1):73-84

An integrated study has been carried out to elucidate the distribution and occurrence of arsenic in selected groundwater samples in the area of Sherajdikhan, Bangladesh. Arsenic and other parameters (T, pH, EC, Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl⁻, NO₃ ⁻, SO₄ ²⁻, HCO₃ ⁻, PO₄ ³⁻, Fe, Mn and DOC) have been measured in groundwater samples collected from shallow/deep tube wells at different depths. Hydrogeochemical data suggest that the groundwaters are generally Ca–Mg–HCO₃ and Mg–Ca–HCO₃ types with bicarbonate (HCO₃ ⁻) as the dominant anion, though the other type of water has also been observed. Dissolved arsenic in groundwater ranged from 0.006 to 0.461 mg/l, with 69% groundwater samples exceeded the Bangladesh limit for safe drinking water (0.05 mg/l). Correlation and principal component analysis have been performed to find out possible relationships among the examined parameters in groundwater. Low concentrations of NO₃ ⁻ and SO₄ ²⁻, and high concentrations of DOC, HCO₃ ⁻ and PO₄ ³⁻ indicate the reducing condition of subsurface aquifer where sediments are deposited with abundant organic matter. Distinct relationship of As with Fe and Mn, and strong correlation with DOC suggests that the biodegradation of organic matter along with reductive dissolution of Fe–Mn oxyhydroxides has being considered the dominant process to release As in the aquifers studied herein.  相似文献   

A sensitive and rapid method for analysis of dissolved mono- and polysaccharides in seawater   总被引：4，自引：0，他引：4  

Sverre M. Myklestad  Elin Skny  Solveig Hestmann 《Marine Chemistry》1997,56(3-4)

A spectrophotometric method is described for the determination of dissolved mono- and polysaccharides in seawater. It is based upon the well known alkaline ferricyanide reaction, but uses the reagent 2,4,6-tripyridyl-s-triazine (TPTZ) to give a strongly colored complex with the reduced iron. The method has been tested on model carbohydrates and other compounds, and also on natural samples of coastal and oceanic waters. Total carbohydrate content of the natural samples ranged from 5.2 to 25.1 μmol glucose-Cl⁻¹. The coefficient of variation was typically below 6% for values near 17 μmol Cl⁻¹ and approximately 10% for values near 3.5 μmol Cl⁻¹.  相似文献   

Detection Capability of Selected Seismic Stations in Central Europe     

Kristeková  Miriam  Skáčiková  Iveta 《Studia Geophysica et Geodaetica》1997,41(2):149-163

The 50% and 90% P-wave detection thresholds of 3 Austrian, 2 Czech, 5 German, 1 Hungarian and 3 Slovak seismic stations have been determined for four intervals of epicentral distances by a direct method using the maximum-likelihood technique. The USGS-NEIC Earthquake Data Reports covering the period from January 1990 to November 1994 were used as the reference system. The seismic stations Kaperské Hory (KHC, Czech Republic) and Collmberg (CLL, Germany) are the stations with the best detection capabilities for all investigated intervals of epicentral distances.  相似文献   

Spatial and Temporal Variability of Benthic Respiration in a Scottish Sea Loch Impacted by Fish Farming: A Combination of In Situ Techniques     

Cécile Cathalot  Bruno Lansard  Per O. J. Hall  Anders Tengberg  Elin Almroth-Rosell  Anna Apler  Lois Calder  Elanor Bell  Christophe Rabouille 《Aquatic Geochemistry》2012,18(6):515-541

The effects of fish farm activities on sediment biogeochemistry were investigated in Loch Creran (Western Scotland) from March to October 2006. Sediment oxygen uptake rates (SOU) were estimated along an organic matter gradient generated from an Atlantic salmon farm using a combination of in situ techniques: microelectrodes, planar optode and benthic chamber incubations. Sulphide (H₂S) and pH distributions in sediment porewater were also measured using in situ microelectrodes, and dissolved inorganic carbon (DIC) fluxes were measured in situ using benthic chambers. Relationships between benthic fluxes, vertical distribution of oxidants and reduced compounds in the sediment were examined as well as bacterial abundance and biomass. Seasonal variations in SOU were relatively low and mainly driven by seasonal temperature variations. The effect of the fish farm on sediment oxygen uptake rate was clearly identified by higher total and diffusive oxygen uptake rates (TOU and DOU, respectively) on impacted stations (TOU: 70 ± 25 mmol O₂ m^?2 day^?1; DOU: 70 ± 32 mmol O₂ m^?2 day^?1 recalculated at the summer temperature), compared with the reference station (TOU: 28.3 ± 5.5 mmol O₂ m^?2 day^?1; DOU: 21.5 ± 4.5 mmol O₂ m^?2 day^?1). At the impacted stations, planar optode images displayed high centimetre scale heterogeneity in oxygen distribution underlining the control of oxygen dynamics by small-scale processes. The organic carbon enrichment led to enhanced sulphate reduction as demonstrated by large vertical H₂S concentration gradients in the porewater (from 0 to 1,000 μM in the top 3 cm) at the most impacted site. The impact on ecosystem functions such as bioirrigation was evidenced by a decreasing TOU/DOU ratio, from 1.7 in the non-impacted sediments to 1 in the impacted zone. This trend was related to a shift in the macrofaunal assemblage and an increase in sediment bacterial population. The turnover time of the organic load of the sediment was estimated to be over 6 years.  相似文献   

Agricolaite, a new mineral of uranium from J��chymov, Czech Republic     

Roman Sk��la  Petr Ondru?  Franti?ek Veselovsky  Ivana C��sa?ov��  Jan Hlou?ek 《Mineralogy and Petrology》2011,103(1-4):169-175

The new mineral agricolaite, a potassium uranyl carbonate with ideal formula K₄(UO₂)(CO₃)₃, occurs in vugs of ankerite gangue in gneisses in the abandoned Giftkiesstollen adit at Jáchymov, Czech Republic. The name is after Georgius Agricola (1494?C1555), German scholar and scientist. Agricolaite occurs as isolated equant irregular translucent grains to 0.3?mm with yellow color, pale yellow streak, and vitreous luster. It is brittle with uneven fracture and displays neither cleavage nor parting. Agricolaite is non-fluorescent. Mohs hardness is ~4. It is associated with aragonite, brochantite, posnjakite, malachite, rutherfordine, and ??pseudo-voglite??. Experimental density is higher than 3.3?g.cm^?3, Dcalc is 3.531?g.?cm^?3. The mineral is monoclinic, space group C2/c, with a 10.2380(2), b 9.1930(2), c 12.2110(3) ?, ?? 95.108(2)°, V 1144.71(4) ?³, Z?=?4. The strongest lines in the powder X-ray diffraction pattern are d(I)(hkl): 6.061(55)(002), 5.087(57)(200), 3.740(100)(202), 3.393(43)(113), 2.281(52)(402). Average composition based on ten electron microprobe analyses corresponds to (in wt.%) UO₃ 48.53, K₂O 31.49, CO₂(calc) 22.04 which gives the empirical formula K_3.98(UO₂)_1.01(CO₃)_3.00. The crystal structure was solved from single-crystal X-ray diffraction data and refined to R ₁?=?0.0184 on the basis of the 1,308 unique reflections with F _o?>?4??F _o. The structure of agricolaite is identical to that of synthetic K₄(UO₂)(CO₃)₃ and consists of separate UO₂(CO₃)₃ groups organized into layers parallel to (100) and two crystallographically non-equivalent sites occupied by K⁺ cations. Both the mineral and its name were approved by the IMA-CNMNC.  相似文献   

Modelling Hydrological Consequences of Climate Change—— Progress and Challenges   总被引：8，自引：1，他引：7  

Chong-yu XU  Elin WID 《大气科学进展》2005,22(6):789-797

The simulation of hydrological consequences of climate change has received increasing attention from the hydrology and land-surface modelling communities. There have been many studies of climate-change effects on hydrology and water resources which usually consist of three steps： （1） use of general circulation models （GCMs） to provide future global climate scenarios under the effect of increasing greenhouse gases, （2） use of downscaling techniques （both nested regional climate models, RCMs, and statistical methods） for ＂downscaling＂ the GCM output to the scales compatible with hydrological models, and （3） use of hydrologic models to simulate the effects of climate change on hydrological regimes at various scales. Great progress has been achieved in all three steps during the past few years, however, large uncertainties still exist in every stage of such study. This paper first reviews the present achievements in this field and then discusses the challenges for future studies of the hydrological impacts of climate change.  相似文献   

Toxinogenicity and cytotoxicity of <Emphasis Type="Italic">Alternaria,Aspergillus</Emphasis> and <Emphasis Type="Italic">Penicillium</Emphasis> moulds isolated from working environments     

J. Skóra  M. Sulyok  A. Nowak  A. Otlewska  B. Gutarowska 《International Journal of Environmental Science and Technology》2017,14(3):595-608

There is currently limited research available on the secondary metabolites of moulds in workplaces. The aim of this study was to determine the mould contamination in museums (N = 4), composting plants (N = 4) and tanneries (N = 4) and the secondary metabolite profiles of Alternaria, Aspergillus and Penicillium isolates from these workplaces. Alternaria, Aspergillus and Penicillium species were identified using the ITS1/2 sequence of the rDNA region. Mould metabolites were quantitatively analysed on standard laboratory medium and mineral medium containing materials specific to each workplace using liquid chromatography-mass spectrometry. We also examined the cytotoxicity of the moulds using MTT (3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide) assays. Air microbiological contamination analyses showed a number of microorganisms, ranging from 2.4 × 10³ CFU m^?3 (composting plants) to 6.8 × 10⁴ CFU m^?3 (tanneries). We identified high percentages of Alternaria, Aspergillus and Penicillium moulds (air 57–59%, surfaces 10–65%) in all workplaces. The following moulds were the most cytotoxic (>90%): Alternaria alternata, A. limoniasperae, Aspergillus flavus, Penicillium biourgeianum, P. commune and P. spinulosum. The same mould species isolated from different working environments exhibited varying toxigenic and cytotoxic properties. Modifying the culture medium to simulate environmental conditions most often resulted in the inhibition of secondary metabolite production. Moulds isolated from the working environments produced the following mycotoxins (ng g^?1): chanoclavines (0.28–204), cyclopiazonic acid (27.1–1045), fumigaclavines (0.33–10,640,000), meleagrin (0.57–13,393), roquefortins (0.01–16,660), rugulovasines (112–220), viridicatin (0.12–957), viridicatol (4.23–2753) and quinocitrinines (0.07–1104), which may have a negative impact on human health.  相似文献   

Beryllium Geochemistry in the Lesni Potok Catchment (Czech Republic), 7 Years of Systematic Study     

T. Navrátil  P. Skřivan  L. Minařík  A. ŽIgová 《Aquatic Geochemistry》2002,8(2):121-133

The biogeochemical study was carried out at the Lesni potok (LP)catchment, Central Bohemia, Czech Republic. The ecosystem was impacted by heavy acid depositionduring the industrial development in 1980–1990. The catchment is forested mostly by two tree species, Norwayspruce and European beech. The Be concentration in the granite bedrock is 12.6 mg kg^-1. Theplagioclase contains the highest Be concentrations out of the rock-forming minerals. Elevatedconcentration of Be (5.4 mu;g L^-1) in surface waters is a result of its mobilization from the soils(3.9 mg kg^-1) and weathered rock by acid precipitation. As the pH of the precipitation and consecutivelypH of the surface waters is increasing in the Czech Republic, the Be concentrations in the surface watersgradually decrease. Groundwater with high pH values contains lower concentrations of Be (0.17 g L^-1)than surface waters. The soils at prone area of the catchment are depleted in Be compared to thesoils in the riparian zones. The vegetation located on the prone area contains lower concentrations of theBe than vegetation at riparian zones. The monitoring of Be in the environment is important with respectto its possible harmful effects on aquatic biota and root systems of the plants.  相似文献   

Delineation and classification of rural–urban fringe using geospatial technique and onboard DMSP–Operational Linescan System     

Sk. Mustak  Naresh Kumar Baghmar  Sudhir Kumar Singh  Ramesh Binolakar 《国际地球制图》2018,33(4):375-396

This study aims to analyse the processes and patterns of peri-urbanization using diurnal earth observation data-sets from onboard DMSP–Operational Linescan System. In this study, multiple correlation, simple and conditional linear regression are used to find out the degree of relationship and spatial behavioural pattern of the factors responsible for the urbanization. All the factors are standardized using the Analytical Hierarchy Process (AHP) coupled fuzzy membership functions. AHP is used to derive the weighting of the factors to produce the urbanity index. In total three functional zones – urban, rural and urban shadow are generated based on factor standardization and spatial contiguity index. Urban fringe is sharing ≥ 60% of Urbanity Index followed by rural fringe (39.50–60% of urbanity index) and urban shadow <39.50% of urbanity index. Shape index indicates that the city is going through unplanned development following cross to star shape growth.  相似文献   

GIS-based landslide susceptibility modeling: A comparison between fuzzy multi-criteria and machine learning algorithms     

Sk Ajim Ali  Farhana Parvin  Jana Vojteková  Romulus Costache  Nguyen Thi Thuy Linh  Quoc Bao Pham  Matej Vojtek  Ljubomir Gigović  Ateeque Ahmad  Mohammad Ali Ghorbani 《地学前缘(英文版)》2021,12(2):857-876

Hazards and disasters have always negative impacts on the way of life.Landslide is an overwhelming natural as well as man-made disaster that causes loss of natural resources and human properties throughout theworld.The present study aimed to assess and compare the prediction efficiency of different models in landslide susceptibility in the Kysuca river basin,Slovakia.In this regard,the fuzzy decision-making trial and evaluation laboratory combining with the analytic network process(FDEMATEL-ANP),Na?ve Bayes(NB)classifier,and random forest(RF)classifier were considered.Initially,a landslide inventory map was produced with 2000 landslide and nonlandslide points by randomly dividedwith a ratio of 70%:30%for training and testing,respectively.The geospatial database for assessing the landslide susceptibility was generated with the help of 16 landslide conditioning factors by allowing for topographical,hydrological,lithological,and land cover factors.The ReliefF methodwas considered for determining the significance of selected conditioning factors and inclusion in the model building.Consequently,the landslide susceptibility maps(LSMs)were generated using the FDEMATEL-ANP,Na?ve Bayes(NB)classifier,and random forest(RF)classifier models.Finally,the area under curve(AUC)and different arithmetic evaluation were used for validating and comparing the results and models.The results revealed that random forest(RF)classifier is a promising and optimum model for landslide susceptibility in the study area with a very high value of area under curve(AUC=0.954),lower value of mean absolute error(MAE=0.1238)and root mean square error(RMSE=0.2555),and higher value of Kappa index(K=0.8435)and overall accuracy(OAC=92.2%).  相似文献