Effect of mini-greenhouse on the transportation of heavy metals

Plastic mulching is widely used for the vegetables growing all over the world. However, plastic mulching might change the soil physic-chemical properties due to its mini-greenhouse effect. The purpose of this study is to probe the possible transportation …     

Experimental modeling of the origin of the Moon’s metallic core at partial melting

Geochemical criteria of the Moon’s composition as deficient in Fe and depleted in volatile components and the distribution of siderophile elements in the planet offer the possibility of correlating, under certain conditions, the origin of the Moon and its core from an initial material of composition close to CI carbonaceous chondrites. In order to verify the model of the percolation of liquid metallic Fe through a silicate matrix of chondritic composition at low degrees of melting, we have experimentally modeled Fe movement and deposition in the course of high-temperature centrifugation. The starting experimental mixture had the composition 85% Ol, 10% ferropicrite, and 5% Fe-S (95% Fe and 5% S); the experimental conditions were 4000 g “gravity”, T = 1440°C, Δ log fO₂(IW) ～ ?5.5. In our experiments, Fe was segregated in systems with Fe sulfide and silicate melts at partial melting under reduced conditions and the deformation of the silicate framework. Our results indicate that the Moon could be produced from a material of composition close to CI carbonaceous chondrite.     

Aqueous heavy metals removal by adsorption on β-diketone-functionalized styrene–divinylbenzene copolymeric resin

An investigation was undertaken regarding the adsorption of different heavy metal ions from aqueous solutions using ??-diketone-functionalized styrene divinylbenzene resin under different experimental conditions such as initial concentration of metal ions, contact time, pH, and chelating capacity. The functionalization of resin was carried out by the condensation reaction of sodium salt of ??-diketones (pentane-1,3-dione) and chloromethylated styrene?Cdivinylbenzene resin in dichloromethane. Functionalized resin beads were characterized by Fourier transform infrared spectroscopy. The batch method was employed using different metal ions solution from 5 to 15?mg/L at different contact times. The adsorption kinetics was tested for the pseudo-first order, pseudo-second order reaction at different experimental conditions. The rate constant of adsorption kinetic models were also calculated and good correlation coefficient (R ²?>?0.9941) was obtained for pseudo-second order kinetic model. The maximum adsorption value obtain for lead (0.725728?mg/g), chromium (0.9199?mg/g), nickel (0.4974?mg/g), cobalt (0.6196?mg/g) and cadmium (0.6519?mg/g) at equilibrium condition, which shows that ??-diketone-functionalized styrene divinylbenzene resin is an effective adsorbent for toxic metal ions.     

Grain size and geochemical partitioning of heavy metals in sediments of the Damodar River – a tributary of the lower Ganga, India

 The distribution of Si, Al, Fe, Mn, Cu, Zn, Ni and Cr in different grain-size fractions and geochemical association of Fe, Mn, Cu and Zn with <63-μm size fraction of bed sediments of Damodar River has been studied. In general, concentrations of heavy metals tend to increase as the size fractions get finer. However at two sites, near mining areas, the coarser particles show similar or even higher heavy metal concentrations than finer ones. The higher residence time and/or presence of coarser particles from mining wastes are possibly responsible for higher metal content in the coarser size fractions. The chemical fractionation study shows that lithogenic is the major chemical phase for heavy metals. Fe and Mn are the major elements of the lithogenic lattice, constituting 34–63% and 22–59%, respectively, of total concentrations. Fe-Mn oxide and organic bound fractions are significant phases in the non-lithogenic fraction. The carbonate fraction is less significant for heavy metal scavenging in the present environment and shows the following order of abundance Zn>Cu>Mn>Fe. The exchangeable fraction of the Damodar sediments contains very low amounts of heavy metals suggesting poor bioavailability of metals. Received: 18 August 1998 · Accepted: 1 December 1998     

Geochemical modeling of leaching behavior of heavy metals in municipal solid waste incinerator fly ashes

Municipal solid waste incinerator (MSWI) fly ash is world-widely defined as hazardous waste because of its high concentration of heavy metals and high toxic equivalents of dioxin-like compounds. Therefore, if not properly disposed, it would pose a risk of…     

Modeling on adsorption–desorption of trace metals to suspended particle matter in the Changjiang Estuary

The uptake and release of trace metals (Cu, Ni, Zn, Cd, and Co) in estuaries are studied using river and sea end-member waters and suspended particulate matter (SPM) collected from the Changjiang Estuary, China. The kinetics of adsorption and desorption were studied in terms of environmental factors (pH, SPM loading, and salinity) and metal concentrations. The uptake of the metals studied onto SPM occurred mostly within 10 h and reached an asymptotic value within 40 h in the Changjiang Estuary. As low pH river water flows into the high pH seawater and the water become more alkaline as it approaches to the seaside of estuary, metals adsorb more on SPM in higher pH water, thus, particulate phase transport of metal become increasingly important in the seaward side of the estuary. The percentage of adsorption recovery and the distribution coefficients for trace metals remained to be relatively invariable and a significant reduction only occurred in very high concentrations of metals (>0.1 mg L⁻¹). The general effect of salinity on metal behavior was to decrease the degree of adsorption of Cu, Zn, Cd, Co, and Ni onto SPM but to increase their adsorption equilibrium pH. The adsorption–desorption kinetics of trace metals were further investigated using Kurbatov adsorption model. The model appears to be most useful for the metals showing the conservative behavior during mixing of river and seawater in the estuary. Our work demonstrates that dissolved concentration of trace metals in estuary can be modeled based on the metal concentration in SPM, pH and salinity using a Kurbatov adsorption model assuming the natural SPM as a simple surfaced molecule.     

Peridotite–eclogite–carbonatite systems at 7.0–8.5 GPa: concentration barrier of diamond nucleation and syngenesis of its silicate and carbonate inclusions

Diamond crystallization in multicomponent melts of variable composition is studied. The melt carbonates are K₂CO₃, CaCO₃?MgCO₃, and K-Na-Ca-Mg-Fe-carbonatites, and the melt silicates are model peridotite (60 wt.% olivine, 16 wt.% orthopyroxene, 12 wt.% clinopyroxene, and 12 wt.% garnet) and eclogite (50 wt.% garnet and 50 wt.% clinopyroxene). In the experiments carried out under the PT-conditions of diamond stability, the carbonate-silicate melts behave like completely miscible liquid phases. The concentration barriers of diamond nucleation (CBDN) in the melts with variable proportions of silicates and carbonates have been determined at 8.5 GPa. In the system peridotite–K₂CO₃–CaCO₃?MgCO₃–carbonatite they correspond to 30, 25, and 30 wt.% silicates, respectively, and in the analogous eclogite–carbonate system, 45, 30, and 35 wt.%. In the silicate-carbonate melts with higher silicate contents seed diamond growth occurs, which is accompanied by the crystallization of thermodynamically unstable graphite phase. In the experiments with melts compositionally corresponding to the CBDN at 7.0 GPa and 1200–1700 °C, a full set of silicate minerals of peridotite (olivine, orthopyroxene, clinopyroxene, garnet) and eclogite (garnet, clinopyroxene) parageneses was obtained. The minerals occur as syngenetic inclusions in natural diamonds; moreover, the garnets contain an impurity of Na, and the pyroxenes, K. The experimental data indicate that peridotite-carbonate and eclogite-carbonate melts are highly effective for the formation of diamond (or unstable graphite) together with syngenetic minerals and melts, which agrees with the carbonate-silicate (carbonatite) model for the mantle diamond formation.     

Relationship between heavy metals and clay mineralogy of the modern sediment of salt marsh at the east coast of Wadden Sea, Denmark

Salt marshes play a significant roll in the marine and coast ecological systems. They can function as a sink for pollutants that would otherwise be harmful to the environment. Our investigation is mainly focused on clay mineralogy of the salt marsh sediment, metal associations in the environment of the modern （centennial） salt marsh sediment and possible relation between these metal associations and clay minerals involved. The studied salt marsh is located in the Skalingen Peninsula, West Denmark. About 85 percent of the deposited materials, including the heavy metals, was imported from the North Sea while only a small quantity of the materials was transported through the Varde River whose mouth is located about 10 km from the salt marsh, at the opposite side of the lagoon. A 25 cm high monolithic profile of the salt marsh sediment was collected and was cut into 1-cm slices. The rate of sediment accumulation, detailed grain size distribution, clay mineralogy, dating of the profile （^210Pb and ^137Cs）, content of organic matter as well as 17 metals： K, Ca, Ti, Mn, Fe, V, Cr, Co, Ni, Cu, Zn, Br, Rb, Sr, Y, Zr, Nb were investigated. Principal components and factor analyses demonstrated strong positive loadings for most of the studied metals, fine grain fractions as well as organic matter, indicating a close relation among these components. Mn, Fe, Ni, Cu, Zn, Rb were found best correlated to the clay fraction （〈2 microns）, which comprises primarily illite, kaolinite, minor chlorite and lesser smectite/illite mixed layer.     

The results of measurements of heavy metals in atmospheric aerosols in the open areas of the Arctic Seas in 2009–2010

By experimental data on the concentration of toxic microelements (Pb, Cd, Cu, Zn, Ni, Co, and Cr) in atmospheric aerosols over the White and Norwegian Seas in winter-spring period of 2009–2010, the contamination of air environment over two sea basins, significantly different by geographical conditions but being heavily impacted by North-European industrial centres, including the impact of the largest in the European Arctic Kola industrial centre, has been analyzed. It has been indicated and described that the air basin over the White Sea water area, when compared to the Norwegian Sea, is under a significantly greater impact of the emission sources of heavy metals, located on the Kola Peninsula.     

Enrichment and mobility of cadmium and other heavy metals in the area of the Three-Gorges Reservoir

This study focused on the geochemical distribution patterns and ecological effects of Cd and other heavy metals such as As, Hg, Cr, Cu, Ni, Pb, and Zn in rock, soil, water, sediment and crops in the area of the Three-Gorges Reservoir within Chongqing, and aimed at the protection of ecological environment and rational application of the local lands. This study found that the metals of Cd, Hg and Pb presented pollution in the surface environment along the Yangtze River, that is Cd〉Hg〉Pb （Cu）〉Zn〉As〉Ni〉Cr. The pollution of Cd in sediment was mainly attributable to the regional black shales, and partly to the urban sewage and garbage. The geochemical modes of metals in the sediment varied. Cr, Hg, Ni, and Pb mainly existed as residues, and Cd as carbonate. Cd exited as a high proportion in the modes of ion-exchange, carbonate, and iron-manganese oxidation, up to 63 percent. The contents of heavy metals in soiland sediment were correlated to the host clay minerals, such as illite, montmorillonite, kaolinite and chlorite. It is shown that Cd was transported with clay minerals in the Yangtze River over long distance and formed the regional anomaly. In the abnormal area of Jianping in Wushan County, higher Cd contents are reported in the local crops and local villagers＇ hairs than from the background areas.     

Isotope–geochemical characterization and geothermometrical modeling of Uttarakhand geothermal field,India

Uttarakhand geothermal area, located in the central belt of the Himalayan geothermal province, is one of the important high temperature geothermal fields in India. In this study, the chemical characteristics of the thermal waters are investigated to identify the main geochemical processes affecting the composition of thermal waters during its ascent toward the surface as well as to determine the subsurface temperature of the feeding reservoir. The thermal waters are mainly Ca–Mg–HCO₃ type with moderate silica and TDS concentrations. Mineral saturation states calculated from PHREEQC geochemical code indicate that thermal waters are supersaturated with respect to calcite, dolomite, aragonite, chalcedony, quartz (SI > 0), and undersaturated with respect to gypsum, anhydrite, and amorphous silica (SI < 0). XRD study of the spring deposit samples fairly corroborates the predicted mineral saturation state of the thermal waters. Stable isotopes (δ¹⁸O, δ²H) data confirm the meteoric origin of the thermal waters with no oxygen-18 shift. The mixing phenomenon between thermal water with shallow ground water is substantiated using tritium (³H) and chemical data. The extent of dilution is quantified using tritium content of thermal springs and non-thermal waters. Classical geothermometers, mixing model, and multicomponent fluid geothermometry modeling (GeoT) have been applied to estimate the subsurface reservoir temperature. Among different classical geothermometers, only quartz geothermometer provide somewhat reliable estimation (96–140 °C) of the reservoir temperature. GeoT modeling results suggest that thermal waters have attained simultaneous equilibrium with respect to minerals like calcite, quartz, chalcedony, brucite, tridymite, cristobalite, talc, at the temperature 130 ± 5 °C which is in good agreement with the result obtained from the mixing model.     

Discrete element modeling of shear wave propagation in carbonate precipitate–cemented particles

Bioremediation is widely used to improve ground soil by introducing calcium carbonate (CaCO₃). Shear wave velocity (Vs) is usually adopted to evaluate effect but the microscopic mechanism is unclear. The discrete element method (DEM), a promising tool for simulating the behaviors of cohesive and noncohesive materials, was used in this study to simulate Vs evolution and wave propagation path of sand reinforced by calcite precipitates. Two basic calcite precipitate forms are proposed for representing individual calcite precipitation (CaCO₃-P) and calcite aggregation (CaCO₃-C). Contact cementation between adjacent sand grain pairs was the primary association pattern for calcite precipitates at a low calcite content. At a higher calcite content, the preferential shear wave propagation pathway is the clusters cemented by CaCO₃-C. With calcite content increasing from 0 to 9%, the coordination number and average contact force increased. Vs increased from 169.73 to 2132.64 m/s but had high variability due to the spatial distribution. The results suggest that the calibrated DEM model can elucidate the microscopic mechanisms and evaluate the enhancement effect of microorganism-reinforced soil.

     

Experimental simulation of magma–carbonate interaction beneath Mt. Vesuvius, Italy

We simulated the process of magma–carbonate interaction beneath Mt. Vesuvius in short duration piston-cylinder experiments under controlled magmatic conditions (from 0 to 300 s at 0.5 GPa and 1,200 °C), using a Vesuvius shoshonite composition and upper crustal limestone and dolostone as starting materials. Backscattered electron images and chemical analysis (major and trace elements and Sr isotopes) of sequential experimental products allow us to identify the textural and chemical evolution of carbonated products during the assimilation process. We demonstrate that melt–carbonate interaction can be extremely fast (minutes), and results in dynamic contamination of the host melt with respect to Ca, Mg and ⁸⁷Sr/⁸⁶Sr, coupled with intense CO₂ vesiculation at the melt–carbonate interface. Binary mixing between carbonate and uncontaminated melt cannot explain the geochemical variations of the experimental charges in full and convection and diffusion likely also operated in the charges. Physical mixing and mingling driven by exsolving volatiles seems to be a key process to promote melt homogenisation. Our results reinforce hypotheses that magma–carbonate interaction is a relevant and ongoing process at Mt. Vesuvius and one that may operate not only on a geological, but on a human timescale.     

Study on the mechanism of transport of heavy metals in soil in western suburb of Beijing

1 IntroductionIncorporation of potentially toxic metals ( e.g.Cd, Cu, Cr, Pb, Hg, As, Se, Zn, Ni) into soils ei-ther through sewage-sludge irrigation or some othersources of pollution (e.g. atmospheric deposition, ap-plication of agri-chemicals) has posed…     

Chemostratigraphy of the Vendian–Cambrian carbonate sedimentary cover of the Tuva-Mongolian microcontinent

The carbonate sediments from the Vendian–Cambrian shelf of the Tuva-Mongolian microcontinent were dated by Sr and C isotope chemostratigraphy. Analysis of the Sr-isotopic characteristics (0.70725–0.70873) and δ¹³C variations (+ 10.5 to –3.5‰), as well as their comparison with the data on the key sections of Siberia, Africa, Central Asia, Australia, South America, and Spitsbergen, showed that the carbonate sedimentary cover of the Tuva-Mongolian microcontinent accumulated at 600–520 Ma and the carbonate sediments of the Muren Formation and the basal beds of the Bokson Group near the Ukha-Gol River are the oldest. Their sedimentation followed the Marinoan global glaciation.     

Speciation and potential remobilization of heavy metals in sediments of the Taihu Lake, China

The species of Cu, Pb, Zn, Cd and Cr in sediments of the Taihu Lake, China, have been analyzed using the sequential chemical extraction method. Variations in the chemical fractions of these metals and their geographic distributions have also been studied. For all five metals, the residual fraction is highest but the exchangeable fraction is lowest among all the fractions. Compared to other metals, Cd has the highest percentage in the exchangeable fraction, and Cr is associated mainly with the residual fraction. Cu in the organic fraction and Pb in the Fe-Mn fraction are the important species, whereas the lowest percentages are found for Cd in the organic fraction, Cu in the Fe-Mn oxide fraction and Pb in the carbonate fraction. With respect to spatial differences, the total contents in the non-residual fractions of the metals in bay sediments are found to be higher than those in other sediments. The fractions of Cd, Cu and Cr showed significant variations in different regions. The fractions of Pb and Zn, however, did not show significant variations in spatial distribution, suggesting different amounts and different paths of anthropogenic input for the metals. Comparisons of the metal speciation indicated that Cd might be the most bioavailable metal, followed by Pb.     

Experimental study of the apatite–carbonate–H2O system at P = 0.5 GPa and T = 1200°C: Efficiency of fluid transport in carbonatite

Partitioning of more than 35 elements between coexisting phases in the apatite (Apt)–carbonate (Carb)–H₂O system was studied experimentally at P = 0.5 GPa and T = 1200°C for estimation of the efficiency of fluid transport during the formation of carbonatite in platform alkaline intrusions. The interphase partition coefficients of elements (D) range from n × 10^–2 to 100 and higher, which provides evidence for their effective fractionation in the system. The following elements were distinguished: (1) Apt-compatible (REE, Y, Th, Cu, and W), which are concentrated in apatite; (2) hydrophile (Na, K, Mg, Ba, S, Mn, Pb, U, W, and Re), which are preferably distributed into fluid or the carbonate melt. The high hydrophilicity of alkali metals controls the alkaline character of postmagmatic fluids and related metasomatic rocks, whereas the high D(Fl/Apt) and D(Fl/L_Carb) for S, Zr, W, Re, and U show their high potential in relation to U–W–Re mineralization.

     

Characteristics and numerical runout modeling of the heavy rainfall-induced catastrophic landslide–debris flow at Sanxicun,Dujiangyan, China,following the Wenchuan Ms 8.0 earthquake

The 2008 Ms 8.0 Wenchuan earthquake triggered a large number of extensive landslides. It also affected geologic properties of the mountains such that large-scale landslides followed the earthquake, resulting in the formation of a disaster chain. On 10 July 2013, a catastrophic landslide–debris flow suddenly occurred in the Dujiangyan area of Sichuan Province in southeast China. This caused the deaths of 166 people and the burying or damage of 11 buildings along the runout path. The landslide involved the failure of ≈1.47 million m³, and the displaced material from the source area was ≈0.3 million m³. This landslide displayed shear failure at a high level under the effects of a rainstorm, which impacted and scraped an accumulated layer underneath and a heavily weathered rock layer during the release of potential and kinetic energies. The landslide body entrained a large volume of surface residual diluvial soil, and then moved downstream along a gully to produce a debris flow disaster. This was determined to be a typical landslide–debris flow disaster type. The runout of displaced material had a horizontal extent of 1200 m and a vertical extent of 400 m. This was equivalent to the angle of reach (fahrböschung angle) of 19° and covered an area of 0.2 km². The background and motion of the landslide are described in this study. On the basis of the above analysis, dynamic simulation software (DAN3D) and rheological models were used to simulate the runout behavior of the displaced landslide materials in order to provide information for the hazard zonation of similar types of potential landslide–debris flows in southeast China following the Wenchuan earthquake. The simulation results of the Sanxicun landslide revealed that the frictional model had the best performance for the source area, while the Voellmy model was most suitable for the scraping and accumulation areas. The simulations estimated that the motion could last for ≈70 s, with a maximum speed of 47.7 m/s.