Release Of Trace Elements Research Articles

Behavior of Li, Rb and Cs during basalt glass and olivine dissolution and chlorite, smectite and zeolite precipitation from seawater: Experimental investigations and modelization between 50° and 300°C

This study investigates experimentally the behavior of Li, Rb and Cs during the hydrothermal alteration of a basalt glass and of forsterite. The behavior of trace alkalis during the dissolution of a basalt glass and forsterite has been followed between 150° and 300°C: Rb and Cs are preferentially leached from the glass while Li exhibits a stoichiometric release with respect to silica. On the other hand, incongruent loss of Li relative to Si during forsterite dissolution reflects a crystallographic (site energy) control of the release of trace elements from crystalline silicates. The partitioning of Li, Rb and Cs between hydrothermal solutions and chlorites, smectites and zeolites has been experimentally investigated between 50° and 260°C. The alteration phases were synthesized by altering silicate glasses in solutions containing the trace alkalis. The lower the temperature, the higher the exchange capacity of the mineral or the lower the ionic hydration energy, then the more the element is incorporated into the solid phases. Computer simulations generated with the EQ3/6 software package and our experimental data on distribution coefficients account for the behavior of alkali trace elements during the alteration of basalt glasses by seawater at mid-ocean ridges.

Future directions for research on materials and design of dental implants

Previous reviews underscore the uncertainties in our knowledge of the influence of material characteristics, design-shape, and surface texture on the implant material-tissue interface. Current implant designs are based on intuitive approaches and there are no general principles for prediction of success of implant systems. Data on implant surfaces prepared by customary preparative techniques show that they are highly variable and dependent on processing. The long-term (years) effects of trace element release from implants is little understood because of past errors in analytical techniques and paucity of relevant data. To place the development of future implant systems on a more rational basis, scientific studies are needed (1) to identify and characterize new and modified materials and surfaces, (2) to validate surface characterization procedures and evaluate tissue responses to standardized surfaces, and (3) to measure trace and subtrace element levels in animal and human tissues over time in order to establish normal and pathologic limits.

The release of trace elements and volatiles from crinoidal limestone during thermal decrepitation

AbstractA suite of coarsely crystalline samples of crinoidal limestone adjacent to a PbS-CaF2-CaCO3 vein in the North Pennine orefield (Greenhow Rake) was analysed by three independent methods [Inductively Coupled Plasma emission spectroscopy (ICP), Mass Spectrometry (MS) and Gas Chromatography (GC)], in order to determine the nature and origin of trace elements and volatiles released on heating and thermal decrepitation, to establish whether fluid inclusions from the host limestone differed in composition from those within the vein, and to assess the value of the results obtained for mineral exploration. The ICP method gave reproducible results for Ca, Na and K, and significant values for Pb and Zn. Na and K correlate with H2O levels determined by MS/volumetric analysis, suggesting their coexistence within fluid inclusions. No such correlation was found for Pb and Zn, suggesting that these elements were derived by volatilisation, perhaps from traces of galena and sphalerite. Methane showed no correlation with H2O and a source other than aqueous fluid inclusions is thought probable for this volatile.The vein calcite showed much lower K/Na fluid ratios (0.05 cf 0.1–0.2), than the limestones. The limestone-hosted fluids occur predominantly in crinoid ossicles and are believed to represent early pre-mineralisation fluids, unrelated to those associated with veining. Combined ICP and MS techniques may be of value in investigating samples where fluid inclusions are too small for microthermometric and optical analysis.

Suspended sediment transport, sedimentation, and resuspension in Lake Houston, Texas: Implications for water quality

Lake Houston is a man-made reservoir located northeast of Houston, Texas. The purpose of this investigation was to document suspended sediment transport, sedimentation, and resuspension in the lake with a view towards estimating the influence of sedimentation on water quality. Sediment traps were placed in strategic locations in the lake to collect suspended sediments. Samples were analyzed for bulk density, grain size, organic carbon, and a number of trace elements. These data were analyzed along with meteorological data to examine those factors which regulate suspended sediment input and dispersal, and the role of suspended sediments in controlling water quality within the lake. Sediment input to the lake depends primarily on the intensity of rainfall in the watershed. Sediment movement within the lake is strongly influenced by wave activity, which resuspends sediments from shallow areas, and by wind-driven circulation. The increased residence time of suspended sediments due to resuspension allows greater decomposition of organic matter and the release of several trace elements from sediments to the water column. Virtually all samples from sediment traps suspended between 1 and 5 m above the lake bottom contain medium to coarse silt, and even some very fine sand-sized material. This implies that circulation in Lake Houston is periodically intense enough to transport this size material in suspension. During winter, northerly winds with sustained velocities of greater than 5 m/sec provide the most suitable condition for rapid (<1 d) transport of suspended sediment down the length of the lake. Fluctuations in current velocities and the subsequent suspension/deposition of particles may explain variations in the abundance of coliform bacteria in Lake Houston.

Submicroscopic model of fly ash particles

Alkaline fly ash produced from the combustion of western coal was chemically weathered and then examined for submicroscopic features and changes in bulk and trace element chemistry in order to develop a physical and chemical model of this waste material. Results of the study showed that elemental partitioning was heterogeneous and that solid glassy ash particles contained a reactive surface glass with accumulations of Ca, B, As, and other trace elements. Weathering of ash involved the dissolution of the surface glass coating and the concurrent release of minor and trace elements contained in the surface layer. Characteristics of the reactive surface layer are presented and submicroscopic features of thick-walled ash particles containing a network of mullite are included in the development of the model of ash particles.

Disposal of fly ash—an environmental problem

This report intends to summarize impacts of fly‐ash disposal on soil‐water environment with special reference to the behaviour of trace elements. Physico‐chemical properties of fly‐ash and trace elements release in environment are dependent on the geological origin of coal, form of the element in coal, combustion products, type of coal burning process, nature of emission control devices, methods of disposal and climatic conditions. Physical and biological transport of trace element, their bioaccumulation, transformation as well as interaction with ecosystem are discussed in terms of their importance in availability, mobility, persistence and ultimate toxicity. Needed research in the areas is identified.

The development of acid-base reaction cements as formulations for the controlled release of trace elements

Novel acid-base reaction cements have been developed for use as controlled release formulations. Many new ones have been discovered and assessed; these include those which are capable of releasing copper, cobalt or selenium singly or in combination. A selection was made of the most suitable formulations for this purpose and these were subjected to field trials.

Reaction cements as materials for the sustained release of trace elements into the digestive tract of cattle and sheep. II. Release of cobalt and selenium.

Acid-base reaction cements, containing salts of copper, cobalt and selenium, were placed in the reticulum of sheep and cattle, and the rate of release of cobalt and selenium from them was measured. The rate of release of cobalt decreased with time but was sufficient to provide adequate supplementation for at least 6 months. After an initial rate of release of 4 mg Se/day for 1-2 weeks, the mean subsequent rate of release of selenium over a period of 4 months was 0.1 mg Se/day (identical to 5 micrograms Se/day/cm2 surface area). Field trials in lambs and growing steers showed that the cement increased the selenium concentration of their blood throughout a summer grazing period.

Reaction cements as materials for the sustained release of trace elements into the digestive tract of cattle and sheep. I. Copper release.

Acid-base reaction cements were produced by reacting copper oxide with phosphoric acid. When placed in the reticulo-rumen of cattle and sheep these cements released copper into the digestive tract for at least 3 months at a rate sufficient to provide the animals' requirements for copper. Lambs given a pellet of cement at 3 months of age had significantly greater concentrations of copper in their livers than similar untreated animals when slaughtered 3-4 months later. It was shown that salts of cobalt and selenium could be incorporated into the cement to provide additional supplementation with these two elements.

Effect of soluble-glass boluses on the copper, cobalt and selenium status of sheep

A soluble glass which has the trace elements copper, cobalt and selenium as part of its structure has been devised by Telfer et al. (1983). This soluble glass is manufactured by Pilkington Brothers and marketed by the Wellcome Foundation under the registered tradename of COSECURE. The COSECURE soluble glass is designed so that it can be given orally to ruminant animals such that when swallowed by the animal, the glass bolus will lodge within the reticulo-rumen of the animal and dissolve in a controlled fashion, thus making the trace elements copper, cobalt and selenium available to the animal. These glasses have been designed for use in both sheep and cattle. The cattle and adult sheep glasses will be effective for I year while the bolus for lambs is designed to be effective for up to 6 months. The trial reported here was carried out on Swaledale lambs, each lamb being given a single lamb-sized bolus of COSECURE at 7-8 weeks after birth. The effect of the COSECURE treatment was monitored by measuring several biochemical variables in the blood of the lambs and comparing these values with a group of untreated lambs. The liveweight gain of the lambs was also measured. The results of this experiment are given in Table 1 and show the response in the lambs blood on the copper status (plasma copper, plasma caeruloplasmin, and erythrocyte superoxide dismutase activity, cobalt status (serum vitamin B, ?) and selenium status (erythrocyte glutathione peroxidase activity). The differences between the treated and control lambs were significant at up to 150 days after treatment except for erythrocyte superoxide dismutase at 150 days. The liveweight gains of the treated lambs were also significantly greater than those of the controls ( 1 2.4 kg in treated as against 8.6kg in control, P<O.OOI). The use of soluble glasses containing trace elements as implants in animals has been reported by Allen et al. (1979) to be an example of a controlled-release system with a possible biological use. Work by Telfer & Zervas ( 1 982) and Telfer et al. (1984) has shown that soluble glasses in the form of rumen boluses can also be used in ruminant animals. The development of a suitable glass for the administration of several trace elements in one bolus by Telfer et al. (1983) has produced a product which will prevent or cure deficiencies of trace elements in cattle and sheep. The results reported here have shown that in the control lambs produced on one farm there were indications of marginal copper status, marginal selenium status and vitamin B , * deficiency at the various times of sampling. The effect of the treatment with the soluble-glass COSECURE was such as to elevate the blood status of the treated lambs in respect of copper, cobalt and selenium such that at 57 and 150 days after treatment these lambs could be taken as having a normal copper, cobalt and selenium status. Therefore soluble glass in the form of a rumen bolus will provide a controlled release of trace elements over a long period of time.

Mobility and bioavailability of uranium mill tailings contaminants

An evaluation of environmental transport and contamination resulting from the release of trace elements and radionuclides from uranium mill tailings was performed by utilizing both laboratory and field studies. The composition of tailings showed the enrichment of a suite of uranium analogue elements (As, Mo, Se, and V) as well as the frequent occurrence of heavy metals generally associated with sulfide minerals (Co, Cu, Ni, and Pb). Aqueous leaching of alkaline tailings mobilized base labile (anionic) species As, Mo, Se, and U, wheras acid tailings leachates contained appreciable Co and Ni. The assimilation of mobile constituents by the roots of native plant species was most evident for Mo and Se in alkaline tailings; levels of these contaminants reported to be toxic to grazing animals were found. The laboratory studies on contaminant mobility and bioavailability are compared with contamination of water, soil, and biota by Mo and U in the vicinity of an alkaline-leach uranium mill. 6 tables.

X-ray Absorption Spectroscopic Investigation of Trace Vanadium Sites in Coal

X-ray absorption spectroscopy was used to probe the chemical and structural environment of vanadium in coal. It was found that vanadium exists in at least two environments, in both of which it was coordinated to oxygens. There was no evidence of vanadium in nitrogen (porphyrin) or sulfide environments. It was also found that the vanadium environments in the raw coal did not survive unchanged in a liquefaction process. These findings have implications for coal cleaning processes and for trace element release into the liquefaction process stream.

Trace element release from estuarine sediments of South Mosquito Lagoon near Kennedy Space Center

Analytical partitioning of four trace metals in estuarine sediments collected from eight sites in South Mosquito Lagoon near Kennedy Space Center, in terms of four different categories was accomplished using four different extraction techniques. The concentrations of the four trace metals, Zn, Mn, Cd, and Cu, released in interstitial water extract, 1 N ammonium acetate extract, conc. HCl extract and fusion extract of sediments as well as their concentrations in water samples collected from the same location were determined using flame atomic absorption technique. From the analytical results the percentages of total amount of each metal distributed among four different categories, interstitial water phase, acetate extractable, acid extractable and detrital crystalline material, were determined. Our results suggest that analytical partitioning of trace metals in estuarine sediments may be used to study the mechanism of incorporation of trace metals with sediments from natural waters. A correlation between the seasonal variation in the concentration of acetate extractable trace metals in the sediment and similar variation in their concentration in water was observed. A mechanism for the release of trace metals from estuarine sediments to natural water is also suggested.

What's new in high temperature sulfur removal systems for fluidized-bed coal gasification

High temperature sulfur removal can be achieved with calcium-based sor-bents (e.g. dolomite) in fluidized-bed çoal gasification systems now being developed for power generation. The use of dolomite offers the opportunity to meet environmental emission standards, to minimize energy losses, and to reduce electrical energy costs. In addition to removing sulfur from the low-Btu gas, the complete sulfur removal system must be integrated with the total power plant and environment to assure compatibility. Critical requirements for achieving commercial system include establishing criteria for ‘acceptable’ sorbents, establishing integrated sulfur removal/gasification process design parameters, predicting trace element release, predicting sorbent attrition, developing an economic regeneration and/or once through process option, developing a spent sorbent processing system, and establishing safe and reliable disposition options for spent sorbent. Design and operating parameters are being developed and potential process limitations are identified.

MAIN ASPECTS OF THE EPIGENESIS PROBLEM

SUMMARY This paper presents the main trends in epigenetic research in the U.S.S.R. in the last years: 1 Study of epigenetic zonality in thick series of sedimentary rocks of various ages and tectonic regions, (zones of unaltered clay matrix, of altered clay matrix, of quartzitic structures and hydromica-chloritic cement, and of prick-like structures and phyllite-like schists). 2 Principles of stadial analysis and mineral indicators of different epigenetic stages (clay minerals, organic matter, zeolites, feldspars, sulfides). 3 Facies of regional epigenesis connecting the main petrographic families of unaltered terrigenic rocks (quartz sandstones with kaolinitic matrix and the same composition of associated clays, acidic arkoses with hydromicaceous clays, lithoclastic sands with several matrix components and associated clays, and volcanogenic greywackes) with “related” facies of regional metamorphism. 4 Some practical aspects of epigenesis are: for petroleum geology: maximum depth of burial according to porosity, interruption of quartz, feldspar, sphene, epidote, carbonate, biotite, and clay mineral epigenesis by oil migration; and for ore geology: (a) initial epigenesis: ore impregnation (e.g., volkonskoite in wood remains) due to intrastratal solution of heavy minerals and leaching of rock fragments; (b) deep epigenesis: e.g., galena impregnations due to release of trace elements during dissolution of rock forming minerals e.g., feldspars; and (c) metagenesis: “Alpine” veins across and along bedding, filled, e.g., with copper ores.

Composition-volume relationships of metasomatism

The actual gains and losses that take place in metasomatic alterations cannot be obtained without a knowledge of the relationship between composition changes and volume changes that accompany the process. A general set of equations is derived that allows calculations of gains and losses in terms of the chemical analyses and the specific gravities of the unaltered and metasomatized rocks or minerals. When comparing two rocks, it is necessary to know or assume knowledge of either the volume change or the geochemical behavior of one component in order to solve the problem. When N minerals are compared in a single alteration equation, N-1 additional facts or assumptions with respect to volume change or geochemical behavior are necessary. It is not necessary to calculate the structural formulas for the minerals. Examples are given of various techniques for solving composition-volume relationships. Trace elements should be evaluated in terms of composition-volume relationships because released trace elements are potential ore sources. Trace element data from individual minerals involved in a suspected reaction may be utilized quantitatively as supporting evidence for the reaction.