Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0432222 (SEM)
 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Volcanic soils affected by different numbers of polluted river flooding events were investigated. Chromium and Cu were the major soil contaminants. Nickel, Fe, Zn and Mn total content never exceeded the Italian mandatory limits. The distribution of Cr and Cu total contents among studied soils indicated that only Cr contamination was related to overflowing events. In polluted soils, sequential chemical extractions revealed a preferential association of Cr and Cu with organic forms. A progressive Cr insolubilization with ageing was observed. Significant amounts of Cr and Cu were extracted by NH(4)-oxalate, suggesting metals association with short-range-order aluminosilicates and organo-mineral complexes. Possible methodological drawbacks in the use of the EU-BCR chemical speciation protocol on volcanic soils are discussed. Micromorphology and SEM/WDS analyses revealed Cr and Cu enriched silt and clay coatings in surface and subsurface soil horizons, suggesting a transfer of metal-rich sediments along the soil pore network with water movement.
 ...
PMID:Impact of river overflowing on trace element contamination of volcanic soils in south Italy: part I. Trace element speciation in relation to soil properties. 1677 4

In this work, a novel sol-gel coating of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (AAPTS)-silica was prepared for capillary microextraction (CME) of trace Cu, Zn, Ni, Hg and Cd followed by on-line ICP-MS detection. This organic-inorganic hybrid coating was in situ created on the inner walls of fused silica capillary using a sol solution containing tetramethoxysilane (TMOS) as a precursor, AAPTS as a co-precursor, ethanol as the solvent and cetyltrimethylammonium bromide (CTAB) as the template. The structure of the capillary coating was characterized by IR, SEM and TEM. Various experimental parameters affecting capillary microextraction of the target analytes have been investigated carefully, and the optimized extraction conditions were established. It was found that the AAPTS-silica coating with a terminal functional group of -NH-CH2-CH2-NH2 exhibited a high selectivity towards the selected metal ions. With a consumption of 1.0 mL sample solution and 80 microL eluent, the detection limits (3sigma) were found to be 1.8, 11.8, 1.1, 3.3 and 1.4 pg mL(-1) for Cu, Zn, Ni, Hg and Cd, respectively. A sampling frequency of 14 h(-1) and an enrichment factor of 12.5 were obtained under the optimized experimental conditions. The relative standard deviations (RSDs) for the target analytes were less than 3.6% (C = 1 ng mL(-1), n = 7, sample volume = 1 mL). Two certified reference materials of NIES No.10-c rice flour and BCR-CRM 278 mussel flesh were analyzed to validate the proposed method, and the determined values were in good agreement with the certified values. The developed method had also been applied to the determination of trace target elements in human hair, serum and urine, and the recoveries for the spiked samples were in the range of 89.2-101.8%. The AAPTS-silica coated capillary showed an excellent pH resistance and could be used for more than 120 times without decreasing adsorption efficiency.
 ...
PMID:Preparation of a high pH-resistant AAPTS-silica coating and its application to capillary microextraction (CME) of Cu, Zn, Ni, Hg and Cd from biological samples followed by on-line ICP-MS detection. 1802 4

Sequential extraction procedures and the high-pressure digestion method were selected to determine the element constituents of fly ash samples. Sequential extraction is one of the most useful methods used to measure the various elements from municipal solid waste incineration ash and contaminated soils. The extract from each step is analyzed using various techniques and equipment, and the results are then evaluated. In this work, a six-step extraction procedure modified from that of Tessier et al. and Wang et al. was performed and applied to the certified reference material BCR 176 (city waste incineration ash). Analyses were carried out by various techniques such as inductively coupled plasma atomic emission spectrometry (ICP-AES), inductively coupled plasma-mass spectrometry (ICP-MS), scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX), and X-ray powder diffraction (XRPD) to evaluate the characteristics of fly ash. The extraction efficiency of many elements was higher than 80%, and the relative standard deviations (RSD) for recovery of most elements were within 10%. In addition, an H(2)O(2)+HNO(3)+HF mixed acid digestion solution processed using a low-temperature evaporation procedure was selected as the optimal process for fly ash digestion. The results of this work provide information on the chemical composition, distribution, and potential mobility of the investigated elements.
 ...
PMID:Application of methods (sequential extraction procedures and high-pressure digestion method) to fly ash particles to determine the element constituents: a case study for BCR 176. 1870 61

Three additives were evaluated for their effectiveness in the attenuation of Pb2+, Zn2+, Cu2+, Cd2+, Ni2+ in contaminated sediments. Apatite, ferrihydrite and their composite were applied to the sediments. For the remediation, BCR, SEM/AVS and TCLP were adopted as the evaluating method and comparison of their results were used for the first time to test in-situ stabilization effect. The results showed that after 5 months composite treatment, more than 70% Pb2+, 40% Zn2+, 90% Cu2+, 50% Cd2+ and 80% Ni2+ was immobilized in oxidizable and residual phases, respectively. Compared to untreated sediment, Pb2+, Zn2+, Cu2+, Cd2+ in residual fraction increased 20%, 10%, 10%, 10% with composite treatment after 5 months, respectively. SigmaSEM/AVS ratio declined from 12.6 to 9.3, in addition, composite treatments reduced the leaching of Pb2+ and Zn2+ from 10.6 mg L(-1) and 42.5 mg L(-1) to 5.4 mg L(-1) and 24.1 mg L(-1) in the sediment by TCLP evaluation. Meanwhile, apatite and ferrihydrite composite additives lowered the bioavailability and toxicity of sediments as well. Ferrihydrite had a positive effect in controlling the bioavailability and toxicity of heavy metals because it effectively retarded the oxidation of AVS in sediment.
 ...
PMID:In-situ stabilization of Pb, Zn, Cu, Cd and Ni in the multi-contaminated sediments with ferrihydrite and apatite composite additives. 1956 75

Over the last few years a great deal of research has been carried out in order to develop remediation methods for reducing environmental risks due to polluting metals. Zeolite formation in contaminated soils mixed with coal fly ash could be a useful method to reduce both the availability and the mobility of metals in contaminated areas. In this study a soil sample--treated with coal fly ash and artificially contaminated with a high concentration of Ni--was used for synthesizing zeolite at low temperatures. The role played by this mineral in the immobilization of heavy metal was investigated. The materials were analysed chemically (sequential extraction) and by XRD and SEM-EDS analyses. The synthesis was carried out both in the laboratory and on a bench-scale for 1 year. Zeolite crystallization readily occurred after a month. The presence of Ni does not exert any influence on zeolite formation. On the other hand newly-formed zeolites reduce the toxicity of the element in the polluted soil. A reduction in heavy metal availability was observed after ammonium acetate extraction. The use of the modified BCR three-step sequential extraction (sequential extraction protocol developed by Community Bureau of Reference of the Commission of the European Communities) suggests that Ni mobilization takes place when zeolite structure collapses after the BCR second step. The Ni thus available was mobilized in the third step.
 ...
PMID:Immobilization of Ni by synthesising zeolite at low temperatures in a polluted soil. 2007 18

In this study, we used the diffusive gradients in thin films (DGT) and conventional methods (including SEM-AVS models, BCR sequential extraction and total metal concentrations) to assess sediment Cr, Ni, Cu, Zn, Cd and Pb bioavailability to field inhabitant freshwater snails (Bellamya aeruginosa) from Chinese eutrophic lakes. The performance of these methods and the relationship between DGT measurements and conventional methods were evaluated. The results showed that DGT-measured metal concentrations have weak correlations with results from tests using SEM-AVS models as well as sequentially extracted European Community Bureau of Reference (BCR) metal fractions. Among the methods used, Cr, Ni, Cu, and Pb measured by DGT were significantly correlated with metal concentrations in the tissue of snails, while SEM-AVS could predict Cr, Ni and Pb bioavailability well, but not SEM-AVS/fOC. Finally, BCR sequential extraction and total metal concentrations only correlated well with Pb bioavailability to snails. Overall, the results of this study indicated that DGT performed best in predicting metal accumulation in snails and which could be used to predict sediment metal bioavailability to field inhabitant snails from freshwater lake sediments due to their simple manipulation and validity.
...
PMID:Use of DGT and conventional methods to predict sediment metal bioavailability to a field inhabitant freshwater snail (Bellamya aeruginosa) from Chinese eutrophic lakes. 2429 70

Long-term wastewater irrigation or solid waste disposal has resulted in the heavy metal contamination in both soil and groundwater. It is often separately implemented for remediation of contaminated soil or groundwater at a specific site. The main objective of this study was to demonstrate the hypothesis of simultaneous remediation of both heavy metal contaminated soil and groundwater by integrating the chemical immobilization and pump-and-treat methods. To accomplish the objective, three experiments were conducted, i.e., an incubation experiment was first conducted to determine how dairy-manure-derived biochar and phosphate rock tailing induced immobilization of Cd in the Cd-contaminated soils; second, a batch sorption experiment was carried out to determine whether the pre-amended contaminated soil still had the ability to retain Pb, Zn and Cd from aqueous solution. BCR sequential extraction as well as XRD and SEM analysis were conducted to explore the possible retention mechanism; and last, a laboratory-scale model test was undertaken by leaching the Pb, Zn, and Cd contaminated groundwater through the pre-amended contaminated soils to demonstrate how the heavy metals in both contaminated soil and groundwater were simultaneously retained and immobilized. The incubation experiment showed that the phosphate biochar were effective in immobilizing soil Cd with Cd concentration in TCLP (toxicity characteristics leaching procedure) extract reduced by 19.6 % and 13.7 %, respectively. The batch sorption experiment revealed that the pre-amended soil still had ability to retain Pb, Zn, and Cd from aqueous solution. The phosphate-induced metal retention was mainly due to the metal-phosphate precipitation, while both sorption and precipitation were responsible for the metal stabilization in the biochar amendment. The laboratory-scale test demonstrated that the soil amended with phosphate removed groundwater Pb, Zn, and Cd by 96.4 %, 44.6 %, and 49.2 %, respectively, and the soil amended with biochar removed groundwater Pb, Zn, and Cd by 97.4 %, 53.4 %, and 54.5 %, respectively. Meanwhile, the metals from both groundwater and soil itself were immobilized with the amendments, with the leachability of the three metals in the CaCl2 and TCLP extracts being reduced by up to 98.1 % and 62.7 %, respectively. Our results indicate that the integrated chemical immobilization and pump-and-treat method developed in this study provides a novel way for simultaneous remediation of both metal-contaminated soil and groundwater.
 ...
PMID:Biochar- and phosphate-induced immobilization of heavy metals in contaminated soil and water: implication on simultaneous remediation of contaminated soil and groundwater. 2435 48

A new polymeric material (Patent: P201400535) highly specific for mercury is presented. Its great capability to pre-concentrate and selectively elute inorganic mercury and methylmercury are the main figures of merit. The polymer can be reused several times. To our knowledge, this is the only polymer proposed in the literature for direct inorganic mercury and methylmercury speciation without need of chromatography or quantification by difference. The polymer formation is based on the reaction of a vinyl derivative of 8-hydroxiquinoline as monomer, and 2-(Methacryloylamino) ethyl 2-Methyl Acrylate (NOBE) as co-monomer. Random radical polymerization by the precipitation method was carried out using Azobisisobutyronitrile (AIBN) as initiator. The polymer was characterized by SEM and FTIR. Adsorption binding isotherms were evaluated using Langmuir and Freundlich models, showing high adsorption capacity for both inorganic and organic mercury species. The polymer was employed to sequentially determine inorganic mercury and methylmercury, using a solid phase extraction (SPE) scheme. Cross reactivity of several ions, as well as matrix effects from a high saline matrix like seawater was irrelevant as the retained fractions mostly eluted during the washing step. The procedure was first validated by analyzing a certified reference material (BCR 464) and finally applied to commercial fish samples. The speciation proposed procedure is cheap, fast, and easy to use and minimizes reagents waste.
...
PMID:A new specific polymeric material for mercury speciation: Application to environmental and food samples. 2651 12

A new method in which Pb/Zn smelter waste containing arsenic and heavy metals (arsenic sludge), red mud and lime are utilized to prepare red mud-based cementitious material (RCM) is proposed in this study. XRD, SEM, FTIR and unconfined compressive strength (UCS) tests were employed to assess the physicochemical properties of RCM. In addition, ettringite and iron oxide-containing ettringite were used to study the hydration mechanism of RCM. The results show that the UCS of the RCM (red mud+arsenic sludge+lime) was higher than that of the binder (red mud+arsenic sludge). When the mass ratio of m (binder): m (lime) was 94:6 and then maintained 28days at ambient temperature, the UCS reached 12.05MPa. The red mud has potential cementitious characteristics, and the major source of those characteristics was the aluminium oxide. In the red mud-arsenic sludge-lime system, aluminium oxide was effectively activated by lime and gypsum to form complex hydration products. Some of the aluminium in ettringite was replaced by iron to form calcium sulfoferrite hydrate. The BCR and leaching toxicity results show that the leaching concentration was strongly dependent on the chemical speciation of arsenic and the hydration products. Therefore, the investigated red mud and arsenic sludge can be successfully utilized in cement composites to create a red mud-based cementitious material.
 ...
PMID:Utilization of red mud and Pb/Zn smelter waste for the synthesis of a red mud-based cementitious material. 2908 Apr 87

In this study, three kinds of amendments including superphosphate, humic acid, and fly ash and their complex combination were adopted to passivate the artificially simulated Pb-and Cd-containing soils. The passivation efficiency evaluation was performed via the CaCl2 and triethylenetriaminepentaacetic acid (DTPA) extraction method as well as a BCR morphological classification experiment. The microstructures and structures of the soil were explored further via X-ray diffraction (XRD) and scanning electron microscopy with X-ray energy dispersive spectroscopy (SEM-EDS) to elaborate the passivation mechanism. The results demonstrated that all passivation processes, excluding single humic acid addition, could reduce the CaCl2 and DTPA extraction contents of Pb and Cd in soils, where the optimal efficiency could be achieved by the sequential addition of superphosphate and humic acid, followed by fly ash. There was a weakly positive correlation between soil pH and CaCl2/DTPA extraction content of Pb, a negative correlation between soil pH and CaCl2/DTPA extraction content of Cd, and a significantly negative correlation between available phosphorous content and CaCl2/DTPA extraction contents of Pb and Cd, suggesting the crucial role of available phosphorous contents to control the activities of Pb and Cd. In the presence of phosphate, humic acid, and fly ash, the Pb and Cd could convert from active weak acid extraction to low-activity residual speciation, resulting in effectively reducing Pb and Cd transferability. Throughout the XRD and SEM-EDS analyses, it was found that ion exchange was the predominant mechanism in heavy metal passivation by single superphosphate, wherein the heavy metals were transformed into an insoluble Ca-containing phosphate mixture. The dissolving/precipitation or surface adsorption could be concluded as the main mechanism in the combination of the three passivation agents that converted heavy metals to lead phosphate precipitate[(Pb3(PO4)2] or mixed heavy metal mineral[PbFe3(SO4)(PO4)(OH)6], so as to obtain superior heavy metal passivation achievement.
 ...
PMID:[Passivation of Simulated Pb-and Cd-Contaminated Soil by Applying Combined Treatment of Phosphate, Humic Acid, and Fly Ash]. 2996 6


1 2 Next >>