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Chemical Form (chemical + form)

Distribution by Scientific Domains

Chemistry	39%
Earth and Environmental Science	26%
Life Sciences	21%

Selected Abstracts

Chemical form of dietary l -Carnitine affects plasma but not tissue Carnitine concentrations in male Sprague,Dawley rats

JOURNAL OF ANIMAL PHYSIOLOGY AND NUTRITION, Issue 2 2009
B. D. Lambert
Summary In Experiment 1, rats (n = 54) were randomly assigned to control or one of the four sources of l -Carnitine supplemented at either 100 or 200 ,mol/kg/day and were allowed to acclimate for 14 days. Following a 12-h fast, plasma samples were obtained at 0, 5, 10, 15, 30, 60, 120, 240, 480 and 720 min after l -Carnitine feeding and assayed for free l -Carnitine concentration. Plasma-free l -Carnitine levels were affected by time after treatment intake (p < 0.0001) and l -Carnitine source (p < 0.0001). The time × source interaction was not statistically significant (p = 0.99). In Experiment 2, rats (n = 54) were randomly assigned to control or one of the four sources of l -Carnitine at either 100 or 200 ,mol/kg/day and were acclimated as in experiment 1. Rats were sacrificed 120 min after feeding. Samples of liver and skeletal muscle were obtained and assayed for free l -Carnitine concentration. Neither skeletal muscle (p = 0.44) or liver (p = 0.59) tissue concentrations of l -Carnitine were affected by any l -Carnitine source as compared with the control. We conclude that some differences exist in plasma concentrations of free l -Carnitine following ingestion of different chemical forms of l -Carnitine. It is unclear if these differences in the circulating concentration of free l -Carnitine translate into any physiological differences for the animal. In this study, chemical form of l -Carnitine had no effect on skeletal muscle or liver tissue concentrations of l -Carnitine in young male Wistar rats. [source]

A review of nitrogen enrichment effects on three biogenic GHGs: the CO2 sink may be largely offset by stimulated N2O and CH4 emission

ECOLOGY LETTERS, Issue 10 2009
Lingli Liu
Abstract Anthropogenic nitrogen (N) enrichment of ecosystems, mainly from fuel combustion and fertilizer application, alters biogeochemical cycling of ecosystems in a way that leads to altered flux of biogenic greenhouse gases (GHGs). Our meta-analysis of 313 observations across 109 studies evaluated the effect of N addition on the flux of three major GHGs: CO2, CH4 and N2O. The objective was to quantitatively synthesize data from agricultural and non-agricultural terrestrial ecosystems across the globe and examine whether factors, such as ecosystem type, N addition level and chemical form of N addition influence the direction and magnitude of GHG fluxes. Results indicate that N addition increased ecosystem carbon content of forests by 6%, marginally increased soil organic carbon of agricultural systems by 2%, but had no significant effect on net ecosystem CO2 exchange for non-forest natural ecosystems. Across all ecosystems, N addition increased CH4 emission by 97%, reduced CH4 uptake by 38% and increased N2O emission by 216%. The net effect of N on the global GHG budget is calculated and this topic is reviewed. Most often N addition is considered to increase forest C sequestration without consideration of N stimulation of GHG production in other ecosystems. However, our study indicated that although N addition increased the global terrestrial C sink, the CO2 reduction could be largely offset (53,76%) by N stimulation of global CH4 and N2O emission from multiple ecosystems. [source]

Voltammetric Assay of Naproxen in Pharmaceutical Formulations Using Boron-Doped Diamond Electrode

ELECTROANALYSIS, Issue 11 2005
V. Suryanarayanan
Abstract The electrooxidation of naproxen was studied, for the first time, using boron-doped diamond (BDD) electrode by cyclic and differential pulse voltammetry (CV and DPV) in nonaqueous solvent supporting electrolyte system. The results were also compared with glassy carbon electrode (GC) under the same conditions. Naproxen undergoes one electron transfer resulting in the formation of cation radical for the first electrooxidation step, which follows other chemical and electrochemical steps such as deprotonation, removal of another electron and the attack of nucleophile (ECEC mechanism). BDD electrode provided higher signal to background ratio, well resolved and highly reproducible cyclic voltammograms than the GC electrode. With a scan rate of 50,mV s,1 and pulse height of 50,ms, respectively, the DPV technique was able to determine the naproxen concentrations in the range of 0.5 to 50,,M with a detection limit of 30,nM. The influence of interference compounds namely 2-acetyl-6-methoxy naphthalene (AMN) on naproxen oxidation can also be followed successfully. Moreover, the percentage of AMN present in the standard chemical form of a mixture containing naproxen can be found accurately. Rapidity, precise and good selectivity were also found for the determination of naproxen in pharmaceutical formulations. [source]

A nonlethal microsampling technique to monitor the effects of mercury on wild bird eggs

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 3 2009
Katherine R. Stebbins
Abstract Methylmercury is the predominant chemical form of mercury reported in the eggs of wild birds, and the embryo is the most sensitive life stage to methylmercury toxicity. Protective guidelines have been based mainly on captive-breeding studies with chickens (Gallus gallus), mallards (Anas platyrhynchos), and ring-necked pheasants (Phasianus colchicus) or on field studies where whole eggs were collected and analyzed and the effects of the mercury were measured based on the reproductive success of the remaining eggs. However, both of these methods have limitations. As an alternative, we developed a technique that involves extracting a small sample of albumen from a live egg, sealing the egg, returning the egg to its nest to be naturally incubated by the parents, and then relating the hatching success of this microsampled egg to its mercury concentration. After first developing this technique in the laboratory using chicken and mallard eggs, we selected the laughing gull (Larus atricilla) and black-necked stilt (Himantopus mexicanus) as test subjects in the field. We found that 92% of the microsampled laughing gull eggs met our reproductive endpoint of survival to the beginning of hatching compared to 100% for the paired control eggs within the same nests. Microsampled black-necked stilt eggs exhibited 100% hatching success compared to 93% for the paired control eggs. Our results indicate that microsampling is an effective tool for nonlethally sampling mercury concentrations in eggs and, as such, can be used for monitoring sensitive species, as well as for improving studies that examine the effects of mercury on avian reproduction. [source]

Simultaneous analyses and applications of multiple fluorobenzoate and halide tracers in hydrologic studies

HYDROLOGICAL PROCESSES, Issue 14 2005
Qinhong Hu
Abstract An analytical method that employs ion chromatography has been developed to exploit the use of fluorobenzoic acids (FBAs) and halides more fully as hydrologic tracers. In a single run, this reliable, sensitive, and robust method can simultaneously separate and quantify halides (fluoride, chloride, bromide, and iodide) and up to seven FBAs from other common groundwater constituents (e.g. nitrate and sulphate). The usefulness of this analytical method is demonstrated in both field and laboratory tracer experiments. The field study examines the hydrologic response of fractures and the matrix to different flow rates and the contribution of matrix diffusion in chemical transport. Laboratory tracer experiments with eight geologic media from across the USA,mostly from Department of Energy facilities where groundwater contamination is prevalent and where subsurface characterization employing tracers has been ongoing or is in need,reveal several insights about tracer transport behaviour: (1) bromide and FBAs are not always transported conservatively; (2) the delayed transport of these anionic tracers is likely related to geologic media characteristics, such as organic matter, pH, iron oxide content, and clay mineralogy; (3) use of iodine as a hydrologic tracer should take into account the different sorption behaviours of iodide and iodate and the possible conversion of iodine's initial chemical form; (4) the transport behaviour of potential FBA and halide tracers under relevant geochemical conditions should be evaluated before beginning ambitious, large-scale field tracer experiments. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Chemical form of dietary l -Carnitine affects plasma but not tissue Carnitine concentrations in male Sprague,Dawley rats

Fully automated high yield synthesis of (R)- and (S)-[11C]verapamil for measuring P-glycoprotein function with positron emission tomography

JOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 14 2002
Gert Luurtsema
Abstract Racemic (±) verapamil is a well characterized substrate for P-glycoprotein (P-gp). However, the in vivo pharmacokinetics and pharmacodynamics of both enantiomers are reported to be different. In the preparation of evaluation studies of both enantiomers in animals and humans, the purpose of the present study was to optimize and automate the synthesis of (R)- and (S)-[11C]verapamil. (R)- and (S)-[11C]verapamil were prepared from (R)- and (S)-desmethyl-verapamil, respectively, by methylation with no-carrier added [11C]methyliodide or [11C]methyltriflate. Different conditions of the methylation reaction were studied: reaction time, temperature, base and solvent, and chemical form of the precursor using either the hydrochloric acid salt or the free base of the starting material. After optimization, the synthesis was fully automated using home-made modules and performed according to GMP guidelines. Optimal yields of 60,70% for the methylation reaction were obtained using 1.5 mg of the free base of (R)- or (S)-desmethyl-verapamil in 0.5 ml of acetonitrile at 50°C for 5 min with [11C]methyltriflate as methylating agent. Under the same reaction conditions, but with a reaction temperature of 100°C, the radiochemical yield starting with [11C]methyliodide as methylation reagent was 40%. The specific activity of (R)- and (S)-[11C]verapamil was >20 GBq/,mol and the radiochemical purity was >99% for both methods. The total synthesis time was 45 min. The automated high yield synthesis of (R)- and (S)-[11C]verapamil provides the means for evaluating both enantiomers as in vivo tracers of P-gp function. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Effects of chromium stress on the subcellular distribution and chemical form of Ca, Mg, Fe, and Zn in two rice genotypes

JOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 1 2010
Fanrong Zeng
Abstract A hydroponic experiment was carried out to study effects of chromium (Cr) stress on the subcellular distribution and chemical form of Ca, Mg, Fe, and Zn in two rice genotypes differing in Cr accumulation. The results showed that Ca, Mg, Fe, and Zn ions were mainly located in cell walls and vacuoles in roots. However, large amounts of metal ions were transferred from the vacuole to the nucleus and to other functional organelles in shoots. Chromium concentrations in the nutrient solution of 50 ,M and above significantly decreased Ca concentrations in the chloroplast/trophoplast, the nucleus, and in mitochondria. It further increased Mg concentrations in the nucleus and in mitochondria, as well as Zn and Fe concentrations in the chloroplast/trophoplast. These Cr-induced changes in ion concentrations were associated with a significant reduction in plant biomass. It is suggested that Cr stress interferes with the functions of mineral nutrients in rice plants, thus causing a serious inhibition of plant growth. The chemical forms of the four nutrients were determined by successive extraction. Except for Ca, which was mainly chelated with insoluble phosphate and oxalic acid, Mg, Zn, and Fe were extractable by 80% ethanol, d-H2O, and 1,M NaCl. The results indicated that these low,molecular weight compounds, such as organic acids and amino acids, may play an important role in deposition and translocation of Mg, Zn, and Fe in the xylem system of rice plants. [source]

Migration of mercury from dental amalgam through human teeth

JOURNAL OF SYNCHROTRON RADIATION, Issue 2 2008
Hugh H. Harris
Exposure to mercury from dental amalgams, with possible negative health effects, has generally been considered to occur via either erosion or evaporation directly from the surface of fillings, followed by ingestion. The aim of this study was to determine the relative importance of the direct migration of mercury through the tooth as an alternative exposure pathway. X-ray fluorescence imaging has been used to determine quantitatively the spatial distribution of Hg, Ca, Zn and Cu in sections of human teeth that had been filled with amalgam for more than 20 years. X-ray absorption near-edge spectroscopy (XANES) was also employed to gain chemical information on the mercury present in the teeth. Hg (up to ,10,mg,g,1) and Zn (>100,mg,g,1) were detected in the teeth several millimetres from the location of the amalgams. At high resolution, Hg showed higher concentrations in dentinal tubules while Zn was generally evenly distributed. XANES showed that the chemical form of Hg that had migrated into the tooth had been altered from that present in the amalgam. The differing spatial distributions of Hg and Zn suggest distinct transport mechanisms for the two metals, presumably chemical for Zn and initially physical for Hg. Subsequent oxidation of Hg may lead to a loss of mobility or the development of a secondary transport mechanism. Most importantly the detection of Hg in areas of the tooth that once contained an active bloodstream and in calculus indicates that both exposure pathways should be considered as significant. [source]

EFFECT OF LACTIC ACID AND LACTIC ACID BACTERIA TREATMENT ON MYOFIBRILLAR PROTEIN DEGRADATION AND DYNAMIC RHEOLOGY OF BEEF

JOURNAL OF TEXTURE STUDIES, Issue 3 2007
M. SIGNORINI
ABSTRACT Lactic acid has been used as an efficient decontaminant in meats aimed for direct consumption or product fabrication. However, reports on the functionality of proteins extracted from lactic acid-treated meat are scattered. The objective of this work was to study the degradation and gelling ability of myofibrillar protein extracts obtained from beef treated with lactic acid of chemical and microbial origins, stored at 4 and 20C. The gelling ability was considerably reduced by lactic acid treatment as a result of protein denaturation in acid conditions at both storage temperatures. Scanning electron microscopy showed loose structures resulting in low penetration resistance and storage modulus. Treatments with lactic acid or lactic acid bacteria (LAB) had similar effect on tan,, affecting gel rigidity but not elasticity. Penetration in gels obtained from LAB-treated meat was highly correlated with myosin degradation. Lactobacillus carnis -treated meat produced compact gels with high penetration resistance and storage modulus, although the structure became looser with storage time. LAB treatment, although not as efficient as lactic acid as a meat preservative, is a milder process causing less severe changes in meat structure rheology. PRACTICAL APPLICATIONS The potential of lactic fermentation by selected strains is somewhat limited as compared to lactic acid preservation of meat substrates, regarding pH reduction and its consequence on pathogens and spoilage microorganism population reduction. However, lactic acid bacteria (LAB) treatments are milder; therefore, changes in protein structure and rheology are less severe. Lactic acid in its chemical form promotes protein changes, whereas LAB does not. As myofibrillar protein configuration is responsible for most meat functional properties, such as gel and emulsion formation, it is important that protein structure remains unchanged as much as possible. Using nonproteolytic strains, protein degradation can only be altered by endogenous or bacteria-produced enzymes, which can be inhibited by several means. Meat preservation by lactic fermentation with selected strains can be an alternative when keeping meat protein functional properties unaltered. [source]

Increased intakes of selenium-enriched foods may benefit human health

JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 9 2007
John Weldon Finley
Abstract Selenium is an essential nutrient and deficient intakes compromise health in domestic animals and humans. A recommended dietary allowance (RDA) of 55 µg d,1 has been set for adult males and females in the United States; most North Americans consume more than this amount, but many residents of Europe, Asia and Africa consume less. While there are very few reports of outright Se deficiency in people consuming mixed Western diets that have Se intakes below the RDA, there is evidence that dietary intakes of selenium greater than the requirement may help reduce the risk of cancer, especially prostate cancer, to men. Selenium metabolism depends on the chemical form of Se in the diet, and some forms are better for some actions (e.g., cancer reduction) than other forms. Foods may contain different amounts and chemical forms of Se; consequently the benefits of Se may depend on the particular foods consumed. There are many reports of the chemistry and health benefits of Se from plant foods; animal foods also contain Se, but there are fewer reported studies. Fully understanding the health benefits of Se that may be gained by consumption of Se-enriched foods will require multidisciplinary approaches by teams of medical researchers, chemists, nutritionists, and agricultural scientists. Copyright © 2007 Society of Chemical Industry [source]

Selenium Accumulation in Plant Foods

NUTRITION REVIEWS, Issue 6 2005
John W. Finley PhD
Selenium (Se) is an essential nutrient, and Se deficiency is associated with disease conditions and general impairment of the immune system. Supplementation of Se to humans already consuming the RDA may help to prevent certain cancers. A convincing argument can be made for augmenting the food supply with Se, and Se-enhanced plants may be the best means of accomplishing this. Plants accumulate varying amounts of Se in different chemical forms; some plants accumulate Se in direct relationship to the amount available from the soil, whereas others (Se-accumulators) may accumulate Se in concentrations many orders of magnitude above that in the soil. There are many different chemical forms of Se in plants, and the form partially dictates the metabolism of Se by the animal that consumes the plant. The Se content and the chemical form of Se withinplants may be altered by manipulation of plant genetics or by agricultural production conditions. However, attempts to maximize Se in plants may have unintended consequences and must be carefully monitored. [source]

Chemical form of dietary l -Carnitine affects plasma but not tissue Carnitine concentrations in male Sprague,Dawley rats

Speciation of oxidation states of elements by capillary electrophoresis

JOURNAL OF SEPARATION SCIENCE, JSS, Issue 11 2003
Marek Trojanowicz
Abstract Progress made in the last five years in the application of capillary electrophoresis methods to chemical speciation of elements is reported on the basis of over 100 literature references. The main trends observed include development of new on- and off-capillary derivatization methods, application of new detection methods, and especially coupling of CE separation systems to powerful atomic spectroscopy and mass spectrometry instruments with various ionization techniques, providing either a sensitive element-specific detection method or a third dimension for high performance separation. Besides numerous CZE and MEKC capillary electrophoresis methods only very few examples of CE speciation with capillary electrochromatography can be found. Concerning the chemical forms of elements determined, the new procedures developed are mostly focused on redox speciation of various oxidation states of elements, metal-bound high molecular compounds, and organometallic species. [source]

Increased intakes of selenium-enriched foods may benefit human health

Pharmacokinetics of Dietary 13C-labeled Icosapentaenoic Acid in Japanese Flounder Paralichthys olivaceus

JOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 2 2002
Akio Tago
The objectives of this study were to investigate: 1) the pharmacokinetics of dietary icosapentaenoic acid (EPA) in the plasma using 13C-labeled EPA ([13C]EPA); 2) the bioavailability of [13C]EPA with different chemical forms; and 3) an effective plasma EPA level for normal growth of the Japanese flounder Parachthys olivaceus. [13C]EPA was biosynthesized using the Chlorella Nannochloropsis oculate, and 1-myristoyl 2-[13C]icosapentaenoyl phasphatidyl-choline ([13C]EPA-PC) and [13C]EPA ethyl ester ([13C]EPA-EE) were chemically synthesized from [13C]EPA. Free [13C]EPA ([13C]EPA-FREE) dissolved in 0.5% tragacanth gum-polye-thyleneglycol (3:1, V/V) was administered to the Japanese flounder at dosages of 2.8, 5.6, and 16.8 mg/kg by a single oral administration. [13C]EPA-PC (44.8 mg/kg) and [13C]EPA-EE (18.3 mg/kg), equimolar to 3.0 mg [13C]EPA-FREE (16.8 mg/kg), were administered to the fish in a similar manner. In [13C]EPA-FREE dosed fish, the kinetics of the mean plasma [13C]EPA were linear with respect to dose. [13C]EPA-FREE and [13C]EPA-PC were more efecient in maintaining high plasma EPA levels than [13C]EPA-EE in the Japanese flounder. [13C]EPA was distributed in plasma, blood cell, eyeball containing the orbital fat, liver, stomach, intestine, skin, brain, heart and muscle in three [13C]EPA derivatives studies. The effective plasma EPA level for normal growth of the Japanese flounder is estimated to be 307 to 937 ,g/mL for EPA-FREE administration, and from 286 to 815 ,g/mL 6.3 to 38 mg/mL for the EPA-PC administration. [source]

Selenium Accumulation in Plant Foods

The determination of N- nitrosamines in food

QUALITY ASSURANCE & SAFETY OF CROPS & FOOD, Issue 1 2010
Colin Crews
Abstract Introduction N -nitrosamines are formed in food as a result of natural chemical interactions, but mainly through food processing activity. Most are potent carcinogens and their determination is therefore of considerable importance. They exist in various chemical forms and have been measured by colorimetric and spectroscopic methods following gas or liquid chromatography or as a total N -nitroso group by measurement of chemically released nitric oxide. Objectives To provide an overview of the available methods for the analysis of N -nitrosamines in food that includes recently developments. Methods The literature was reviewed from the discovery of the N -nitrosamine problem and the introduction on the N -nitroso-specific detector. Results The evaluation shows that analytical detection methods for volatile N -nitrosamines in food have changed little since the introduction on the N -nitroso-specific detector and that research into the occurrence and formation of both non-volatile N -nitrosamines and the apparent total N -nitroso content (ATNC) have declined. Methods for measuring the apparent total N -nitroso content have not been improved significantly in recent years. Conclusion Modern sample extraction techniques and mass spectrometric methods for the volatile N -nitrosamines have been applied more extensively to water analysis and offer a good opportunity to improve the determination of these carcinogens in food and make the analysis more widely available. Developments in liquid chromatography-mass spectrometry should provide an avenue for renewed interest in non-volatile N -nitrosamines, and could help with the identification of novel compounds whose presence is suggested by the high apparent total N -nitroso content of some foods. [source]

Analytical sensitivity of arsenobetaine on atomic spectrometric analysis and the purity of synthetic arsenobetaine,

APPLIED ORGANOMETALLIC CHEMISTRY, Issue 9 2006
T. Narukawa
Abstract Arsenobetaine is one of the main organoarsenic compounds that exist in living organisms. Determination errors in total arsenic analyses for organoarsenic compounds occur because analytical sensitivities depend upon the chemical forms of the compounds. However, information on the analytical sensitivity of arsenobetaine by ICP-MS and ICP-AES and the purity of commercially available arsenobetaine standards is lacking. BCR CRM 626 (arsenobetaine solution) is a certified reference material from IRMM with a certified concentration of arsenobetaine. The sensitivity and behavior of arsenobetaine on ICP-MS and ICP-AES were investigated using the BCR arsenobetaine. The analytical sensitivity and behavior of arsenobetaine using ICP-MS and ICP-AES were also investigated using a commercially available synthetic arsenobetaine, and were compared with results for BCR-AB based on a Japan calibration service system (JCSS) arsenic standard solution. In the results, arsenic determined directly in arsenobetaine showed about 15% greater sensitivity in analysis by ICP-MS and ICP-AES than did inorganic (JCSS) arsenic. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Distribution of arsenic species in the freshwater crustacean Procambarus clarkii

APPLIED ORGANOMETALLIC CHEMISTRY, Issue 12 2002
V. Devesa
Abstract The concentrations of total arsenic and arsenic species in the complete organism of the crayfish Procambarus clarkii and its various parts (hepatopancreas, tail, and remaining parts) were analyzed in order to discover the distribution of arsenic and its species. With this information it will be possible to establish where the chemical forms of this metalloid tend to accumulate and what risks may derive from the contents and species present in the edible parts of this crustacean. The total arsenic content in the complete organism and in the various parts analyzed ranged from 2.5 to 12,µg g,1 dry mass (DM), with inorganic arsenic representing 18 to 34% of total arsenic. The arsenical composition varied according to the part of the crayfish considered. The hepatopancreas had the highest levels of total arsenic (9.2,12,µg g,1 DM) and inorganic arsenic (2.7,3.2,µg g,1 DM). The tail (edible part) had the lowest levels of both total arsenic (2.5,2.6,µg g,1 DM) and inorganic arsenic (0.46,0.64,µg g,1 DM). The predominant organoarsenical species were the dimethylarsinoylribosides: glycerol riboside in the hepatopancreas, sulfate riboside in the tail, and sulfonate and phosphate ribosides in the remaining parts. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Heavy Metal Distribution in Soils near the Almalyk Mining and Smelting Industrial Area, Uzbekistan

ACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 5 2009
Obidjon KODIROV
Abstract: The present study demonstrates distribution and chemical forms of heavy metals in soils of the Almalyk mining and smelting industrial area along five transects. The study area is located in Almalyk, Uzbekistan, where the intensification of industrial enterprises negatively impacts the environment. The distribution of 17 heavy metals (Cu, Zn, Pb, Sc, V, Cr, Co, Ni, Ga, Rb, Sr, Y, Zr, Nb, Ba, Th, and U) were studied in 21 sampling locations (21×3=63 soil samples) along five radial transects with a total length of 60 km downwind deposition gradient. Soil samples were collected from the upper layer (0,10 cm) at 4,6 km intervals. As a result of X-ray fluorescence spectrometry analyses by using X-ray fluorescence spectroscopy (XRF, Philips Analytical Ink, USA), a significant decrease in heavy metal (Cu, Zn, Pb) deposition was found going from the source in a downwind direction. Soil samples taken from the first location (near the pollution sources) showed higher concentrations of Cu, Zn and Pb, and lower concentrations with increasing distance from the source. Obtained data showed different impact of pollution sources to heavy metal deposition and distribution in soils. The Almalyk mining and smelting complex is the major source of Pb, Zn and Cu enrichment in soils. Distribution of other trace elements does not exceed background content and suggests lithogenic background. This allowed us to divide these elements into two groups: (1) technogenic (Cu, Zn and Pb); and (2) lithogenic (Sc, V, Cr, Co, Ni, Ga, Rb, Sr, Y, Zr, Nb, Ba, Th and U) origins. [source]

Selection and Basic Properties of the Buffer Material for High-Level Radioactive Waste Repository in China

ACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 5 2008
WEN Zhijian
Abstract Radioactive wastes arising from a wide range of human activities are in many different physical and chemical forms, contaminated with varying radioactivity. Their common features are the potential hazard associated with their radioactivity and the need to manage them in such a way as to protect the human environment. The geological disposal is regarded as the most reasonable and effective way to safely disposing high-level radioactive wastes in the world. The conceptual model of geological disposal in China is based on a multi-barrier system that combines an isolating geological environment with an engineered barrier system. The buffer is one of the main engineered barriers for HLW repository. It is expected to maintain its low water permeability, self-sealing property, radio nuclides adsorption and retardation properties, thermal conductivity, chemical buffering property, canister supporting property, and stress buffering property over a long period of time. Bentonite is selected as the main content of buffer material that can satisfy the above requirements. The Gaomiaozi deposit is selected as the candidate supplier for China's buffer material of high level radioactive waste repository. This paper presents the geological features of the GMZ deposit and basic properties of the GMZ Na-bentonite. It is a super-large deposit with a high content of montmorillonite (about 75%), and GMZ-1, which is Na-bentonite produced from GMZ deposit is selected as the reference material for China's buffer material study. [source]