Dusts from dry lakebeds： Mineralogical and geochemical characteristics of potential health concern

Dry lakebeds can be important sources of dusts that are potentially deleterious to the health of chronically exposed populations. The lakebeds accumulate and can concentrate natural and anthropogenic contaminants transported in particulate and dissolved form from the surrounding watersheds. The lakebed sediments are commonly enriched in respirable-size, detrital clay particles that can be disturbed to form dust. Evaporative concentration of ephemeral lake waters following intermittent wet periods, and of near-surface ground waters beneath some lakebeds, can enrich the sediments in diverse alkaline sulfate, carbonate, and chloride salts. Chemical reactions between alkaline evaporative waters and detrital silicates in the sediments can produce secondary silicates such as zeolites. Lakebeds with abundant salts and intermingled silicates can be highly susceptible to wind erosion, and repeated regeneration of salts in surface sediments may maintain a sustained source of salt-rich dusts. Potential health concerns arise in part from the large load of respirable particles emanating from some dry lakebeds. These concerns are exacerbated if the dusts have elevated metals, particularly metals enriched in soluble evaporative salts. For example, Owens-a dry lake, California, which was prior to mitigation the largest source of PM10 dust in the continental United States, contains elevated As in its dusts. Chemical leach tests using water and simulated gastric and lung fluids indicate that dry lakebed sediments and dusts can contain bioaccessible As, Mn, Al, Zn, Cu, Pb, U, W, Mo, and other potentially toxic metals. Another possible health issue is the occasional presence in lake sediments of secondary erionite, a fibrous zeolite associated with asbestos-related diseases. The potential presence of pathogens, as well＇as enrichments, bioaccessibility, and toxicity of pesticides and other organic pollutants in the dusts must also be evaluated. Earth scientists can help assess potential health effects of dry lakebed dusts by developing predictive models for dust generation and dust toxicity based on the geology,     

Lead isotope and trace metal characteristics of particulates accumulated on vehicular tunnel ceilings in Hong Kong and Guangzhou, SE China

Ever-increasing accumulation of trace metals in the environment is a serious health concern. This is a valid apprehension particularly in urban settings where the population and the level of trace metal contamination are increasing rapidly. Hong Kong and Guangzhou are the most populated cities in the region of the Pearl River Delta, the fastest growing economic region in the world. In unconfined urban compartments, particulates deposited on the earth surface such as road dusts and gully sediments are good indicators to assess the level of trace metal contamination. In such locations, however, source partitioning of the pollution, which is essential to assess and then reduce the potential environmental risk, is a difficult task. This is mainly due to the complexity and variability of site-specific natural and anthropogenic conditions. This leads us to focus on the particulates accumulated in relatively confined settings, such as vehicular tunnels. Our recent studies demonstrated that particulates accumulated on the ceiling of tunnels are useful to characterize particulates mainly derived from traffic related activities. With this in mind, Pb isotope ratios and trace metal contents of the ceiling dusts from the Cross-Harbor Tunnel （CHT） in Hong Kong and the Pearl River Tunnel （PRT） in Guangzhou were characterized and compared with each other in order to evaluate the environmental impact of traffic derived inorganic pollutants in the region. The ceiling dusts from both tunnels were dominated by silt-sized particles （〈63 μm） which are significantly freer than those of road dusts, usually larger than （〉200 μm）. In general, Cr, Ni, Pb and especially Cu contents of the ceiling dusts from CHT were noticeably higher than those from PRT. This was partly attributed to longer residence time of particulates in CHT, which has been operating since 1976, while the PRT was open to public in 1996. On the other hand, Co, Fe, Mn and Zn contents of the ceiling dusts from CHT were similar to those from PRT, while Ca and Mg contents were noticeably lower.     

Microbial resistance to the heavy metal pollution

It is estimated that the poisonous heavy metals released to the environment come up to million tons. Such great amounts of poisonous heavy metals result in a serious bane to ecosystem and human health. The valid control of spreading and pollution of heavy metals in the environment has hence become an urgent issue of the moment. In this study, through tameness and induction of living creature＇s tolerance from dirty mud, using microbial technology we have cultivated some anti-heavy-metal microbes able to resist the pollutions from poisonous chemical elements such as arsenic, chromium, cadmium, hydrargyrum, and plumbnm, four of which are fungi and five are bacteria. Atomic absorption spectroscopy and atomic fluorescence spectrophotometry analyses showed that, to the same chemical element, fungi have stronger resistance than bacteria by one time or so.     

Spatial analysis of elements in soils from Chengdu City

Three kinds of spatial analysis methods （geostatistics, concentration-area fractal model and the multifractal analysis called the moment method） were used for almost 50 elements, including heavy metals, disperse elements, rare elements and even others, in 6586 top soil （0-20 cm） samples and 1833 deep soil （150-200 cm） samples from Chengdu metropolitan area of 12400 km^2, southwestern China. The ranges of spatial correlation revealed by variograms are quite different for different kinds of elements in the top and deep soils. The most interest is the fact that the multifractal spectra of environmentally important elements such as Pb, Cr, Cd and Ni in top soils in the metropolitan area show systematic change from those in the deep soils, revealing a strong anthropogenic addition, while Hg, Zn, As, Cu and all common elements show no such kind of addition. In terms of multifractal properties based on the multifractal spectrum curves, those disperse and rare elements show great deviation from other major and trace elements, which is also of great interest.     

Trace Element Geochemistry of Cenozoic Volcanic Rocks in Shandong Province

The Cenozoic volcanic rock of Shandong Province are mainly alkalic and strongly alkalic basaltic rocks.The Contents of major and trace elements including transitional,incompatible and rare-earth elements were determined.The chemical characterisitics of major and trace elements indicate that these basaltic rocks were derived from a mantle source and probably represent a primary magma,I,e.,unmodifiecd partical melts of mantle peridotite in terms of Mg values,correlatione between P2O5 and Ce,Sr,Ni and Rb concentrations,mantle xenoliths,etc.The abundances of trace elements vary systematically from west to east.The compatible transition elements such as Co,Ni,and Cr show a remarkable depletion,whereas the incompatible and rare-earth elements are abundant as viewed from the chondrite-nor-malized patterns.The chemical composition and correlation are consistent with the tectonic setting.According to the batch and fractional partial melting theory,the trace element contents of Shandong volcanic rocks can be calculated from the two-component mixing model.     

吐鲁番盆地中生代、新生代沉积岩中微量元素的分布

Distributional characteristics of trace elements (V,Co,Ni, Cu,Pb,Cr,Sr,Ra) have been examined in sedimentary rocks of various ages in Turfan, an intermountainous basin in Sinkiang Uighur Autonomous Region, northwestern China. Two major cycles are generally recognizable with respect to the variation in trace element contents during the geologic history from the Mesozoic through the Cenozoic, Within the first cycle, the concentrations of many trace elements except Sr and Ba were relatively high in the Early and Middle Jurassic (J1 and J2^1-J2^2 ), which were characterized by moist climate and a large amount of organic matter. But an opposite trend was observed as the climate became drier and organic matter depleted in Late Jurassic Period (J3). Within the second cycle, Sr and Ba decreased as opposed to the increase in many other trace elements in the Early Cretaceous while the reverse was true for the Tertiary. The distribution pattern of thrace elements is thought to be the result of the interaction among a variety of factors, such as the mode of migration of the elements,palaeoclimatology, palaeogeography, conditions of the water-medium, and ete.     

Natural siliceous dust and human health： Pathways, toxicity, and impact

Fine atmospheric dust includes mineral particles and aggregates, fibrous minerals and fibrous organic material. Generation, dislodgement and transport （deflation） of natural dust with the finer （〈4 microns） components suspended as silt-size aggregates, is widespread in and adjacent to the world＇s drylands, as well as deriving from volcanic vents. Silica is a highly fibrogenic agent in lung tissue. Long-term inhaling of siliceous dusts can lead to a number of fibrotic lung diseases, including natural （non-occupational） pneumoconioses （notably silicosis, but including asbestosis and others）. Different polymorphs of silica show different levels of toxicity in interaction with lung tissue. Particles with highly active surfaces may release radicals, causing cell damage. Some types of inhaled particulates are degraded by macrophages, but many are highly resistant and persist in the lungs, some stimulating fibroblastic cells to deposit collagen. Silicosis is an inflammation of the lung commonly caused by silicate mineral particles, leading to fibrosis. Three types are recognized： nodular pulmonary fibrosis （simple or chronic silicosis）, acute silicosis, and accelerated silicosis. Generally, finer particulates have greater oxidative capacity than the coarser fractions. They contain more reactive oxygen species, their greater bioreactivity making them more toxic to pulmonary tissue. Nevertheless, inhalation of large dust particles （〉 10μm） may constitute a health risk if the mineralogy is toxic, regardless of where the grains lodge in the respiratory system. Dust may absorb harmful gases, disease-generating bacteria and carcinogenic hydrocarbon compounds. Silica-related respiratory disease may also an exacerbate cardiac problem, and epidemiology suggests a link with tuberculosis. Quantification of dust loading and exposure requires study of spatial and temporal patterns, supported by meteorological analysis, airflow modeling and satellite-borne imagery. Some acute, short-term health impacts have been assessed using atmospheric and health records both before and after a dust storm or by comparison of populations within and outside such events. Analysis of the size, shape, mineralogy and geochemistry of ambient dust particulates provides information on natural dust sources, dust concentrations, and potential particulate toxicity, as well as providing a datum for assessment of human exposure levels.     

Concentrations of heavy metals in fly ash from CAN coal combustion thermal power plant （Canakkale-Turkey）-II

Coal combustion can mobilize trace elements by introducing them to terrestrial, aquatic and atmospheric environments, and if leached, these elements may cause the contamination of soils, surface waters and groundwater. Therefore, these elements may become a hazard to the environment because of their contribution to the formation of toxic compounds, if the ash is not utilized or disposed of properly. This possible contamination could lead to health, environmental and land-use problems. A fluid coal-t-fred thermal power plant （320 MWel） has been in operation since 2005 in Can （Canakkale-Turkey） and currently produces almost half a million tones of fly ash per year. Fly ash is classified based on the nature of constituents present. Fly ashes of Class C contain less than 70% but greater than 50% of silica, alumina, and iron oxide which are typical for the western part of Turkey. When the ash concentrations of these three constituents exceed 70%, fly is classified as F, which is representative of those, produced from Can. Fly ash is enriched in many trace elements particularly metals in this thermal power plant ash. These metals are part of the pyrite structure in the coal and become concentrated in the fly ash during the combustion process. These elements may be surface adsorbed on the glassy spherical fly ash particles. Elements that are surface adsorbed can be quite mobile.     

Application of syringe-driven chelate-minicolumn in determination of trace elements in water samples

The direct determination of most trace elements in natural water samples is still very difficult even if the high-sensitivity atomic analytical instrument, such as ICP-MS, is available. The reasons are (1) the natural concentrations of most trace elements…     

The Discovery and Study of Mantle-Derived Dunite Inclusions in Hornblende-Diorite in the Handan-Xingtai Area,Hebei

Phlogopiie-and diopside-bearing dunite occurs as rounded inclusions in hornblende-diorite. Thepetrofabrics, mineral composition and abundances of the trace elements in the dunite indicate that the inclu-sions were derived from the upper mantle and are the residues of high-degree partial melting of mantlepeirdotite. The study of trace elements in the inclusions and their host rocks shows that the magma was origi-nated from the mantle which was enriched in incompatible elements by mantle metasomatism prior to the par-tial melting.     

Geochemistry of sulfur and hazardous trace elements in coals and its bearing on human health

Hazardous air pollutants, including compounds of sulfur and toxic trace elements, are emitted during coal combustion. Geochemical studies of these constituents in coals provide information about their species, regional distribution and origins. The data are useful in understanding the cause and scope of human health problems related to these hazardous elements and in designing preventive or remedial measures. Sulfur in coal is a problem because sulfur dioxide emitted during coal combustion is a main source of acid rain. The sulfur isotopic evidence shows that sulfur in low-sulfur coal is derived primarily from parent plant materials. Sulfur enrichment in medium- and high-sulfur coals is caused by the sulfate in seawater that flooded the peat swamp during coal formation. The sulfur content of a coal is controlled primarily by the depositional environment of coal seams. Only pyritic sulfur can be removed by physical coal cleaning processes （coal preparation）. Sulfur dioxide emission can be reduced using clean coal technologies, such as flue-gas desulfurization, fluidized-bed combustion, and integrated gasification and combined cycle.     

A Preliminary Study on Dust Grains in the Stratosphere

Collected by means of a high-altitude scientific balloon and a self-made automatic sample collector,a total of 276 dust grains were selected for the study of shape,grain size and optical property.Some of the grains were examined by X-ray diffraction and electrom microprobe techniques,The stratospheric dust grains can be classified as 6 types:cosmic dusts,cosmic dusts(?),microtektite,natural pollutants,artificial pollutants and the unknown substances.The different types of dust grains have different characters and distinguishing symbols.Widespread in the space of the solar system,cosmic dusts are the initial substances of the solar system and ,to some degree,have recorded a great wealth of information on the early history of the solar system.So they have become one of the important objects in the field of cosmochemistry at present time,Since the 1960‘s,scholars of many countries have collected cosmic dusts both in the space near the earth(using rock ets,space probes and space shuttles)and in the stratosphere (using high-altitude balloons or U-2air planes).According to the shape(the scanning electron microimage),element composition(the energy-dispersive X-ray spectrum)and optical properties of dust grains,the substances in the stratosphere can be classified as 5 types:cosmic dusts,alumina spheroids,terrestrial artificial pollutants,terrestrial natural pollutants and unknown substances(CDPET,1982).     

Geochemical Behaviors of REE and Other Trace Elements during the Formation of Strata-bound Skarns and Related Deposits: A Case Study of the Dongguashan Cu (Au) Deposit, Anhui Province, China

REE and other trace elements in the altered marbles, massive skarns and ores, as well as garnet and quartz were determined in order to examine the behaviors of trace elements during hydrothermal alteration. It is demonstrated that the high-field-strength (HFS) elements Zr, Hf, Th and Nb were immobile while other trace elements were mobile during the formation of skarns and related deposits. REE and ore-forming elements such as Cu and Ag in hydrothermally-altered marbles and skarns were provided primarily by hydrothermal fluids. In the direction transverse of the strata, the more deeply the marbles were altered, the higher the total REE abundance and the larger the negative Eu anomalies would be. The chondrite-normalized REE patterns of skarns are similar to those of the marbles, but the former are distinguished by much higher REE contents and more remarkable negative Eu anomalies. Those patterns were apparently not inherited from the marble protolith, but were controlled by garnets, which were determine     

Behaviours of REE and Other Trace Elements During Pedological Weathering-Evidence from Chemical Leaching of Loess and Palaeosol from the Luochuan Section in Central China

The chemical leaching method is used for a systematic analysis of distribution characteristics of acid-soluble and acid-insoluble REE and other trace elements from the Luochuan loess deposits. The study shows that the acid-insoluble phase in loess and palaeosol is a stable component of old aeolian dusts and is characteristic of the provenance; the acid-soluble phase is the unstable component in the weathering pedogenic process and reflects rock-forming features after accumulation of aeolian dusts. The acid-insoluble REE and acid-soluble Sr and Pb can be used as geochemical indicators respectively to trace the provenance characteristics and the weathering pedogenic process.     

http://www.sciencedirect.com/science/article/pii/S1674987114000243

We combine a geological, geochemical and tectonic dataset from 118 ophiolite complexes of the major global Phanerozoic orogenic belts with similar datasets of ophiolites from 111 Precambrian greenstone belts to construct an overview of oceanic crust generation over 4 billion years. Geochemical discrimi- nation systematics built on immobile trace elements reveal that the basaltic units of the Phanerozoic ophiolites are dominantly subduction-related （75%）, linked to backarc processes and characterized by a strong MORB component, similar to ophiolites in Precambrian greenstone sequences （85%）. The remaining 25% Phanerozoic subduction-unrelated ophiolites are mainly （74%） of Mid-Ocean-Ridge type （MORB type）, in contrast to the equal proportion of RiftlContinental Margin, Plume, and MORB type ophiolites in the Precambrian greenstone belts. Throughout the Phanerozoic there are large geochemical variations in major and trace elements, but for average element values calculated in 5 bins of 100 million year intervals there are no obvious secular trends. By contrast, basaltic units in the ophiolites of the Precambrian greenstones （calculated in 12 bins of 250 million years intervals）, starting in late Paleo- to early Mesoproterozoic （ca. 2.0-1.8 Ga）, exhibit an apparent decrease in the average values of incom- patible elements such as Ti, P, Zr, Y and Nb, and an increase in the compatible elements Ni and Cr with deeper time to the end of the Archean and into the Hadean. These changes can be attributed to decreasing degrees of partial melting of the upper mantle from HadeanJArchean to Present. The onset of geochemical changes coincide with the timing of detectible changes in the structural architecture of the ophiolites such as greater volumes of gabbro and more common sheeted dyke complexes, and lesser occurrences of ocelli （varioles） in the pillow lavas in ophiolites younger than 2 Ga. The global data from the Precambrian ophiolites, representative of nearly 50% of all known worldwide greenston     

Heavy metal distributions in the sediments of ＂Cattle Pond＂ on the Dongdao Island of South China Sea： Geochemical and statistical approaches for source tracing

The Dongdao Island of the Xisha atolls is located in the center of the South China Sea. The nearby ambient sea, with thousands of reefs, atolls, submerged reefs and banks, is probably one of the most biologically diverse bodies of water on the planet. Due to the distance from the mainland of China and unaccessibility to this coral island, little research work has been conducted to date. Because only Chinese troops and a few fishermen are allowed to reside in some islands, however, the Xisha region is at a relatively pristine condition and provides an ideal site for investigating geochemical characteristics and processes of trace heavy metals. The levels and depth distributions of As, Cd, Cu, Zn, Pb, Hg and P in two sediment cores DY2 and DY4 collected from the ＂Cattle Pond＂ of the Dongdao Island, South China Sea, were determined and analyzed with the main objective to identify the sources of these elements and evaluate the corresponding sedimentological and geochemical processes. Lithological characters and sedimentary parameters such as LOI 950℃, CaO, LOI 550℃ and TOC indicate that the depths of 96 cm and 87 cm are the critical points for DY2 and DY4 cores, respectively. As, Cd, Cu, Zn, Hg and P are remarkably enriched in the ornithogenic sediments above the critical depth points; their concentration-versus-depth profiles are similar to those of TOC and LOI 550℃; the ratios of As, Cd, Cu, Zn, Hg over Ca are significantly correlated with P/Ca. Statistical and comparative analyses of these elements＇ levels in the ornithogenic sediments of DY2 and DY4 strongly suggest that seabird droppings are the main source of these elements, and these heavy metals are very likely transported into the sediments through sorptive or complexing reactions with humic phosphate compounds leached from guano. Additionally, for the upper sediment layers of DY2 and DY4 cores, Fe oxide sorption mechanism, like organic matter, may also play an important role in the abundance of heavy metals.     

Volcanic emissions and atmospheric pollution:A study of nanoparticles

The influence of emissions of an active volcano on the composition of nanoparticles and ultrafine road dust was identified in an urban area of the Andes.Although many cities are close to active volcanoes,few studies have evaluated their influence in road dust composition.Air quality in urban areas is significantly affected by nonexhaust emissions(e.g.road dust,brake wear,tire wear),however,natural sources such as volcanoes also impact the chemical composition of the particles.In this study,elements from volcanic emissions such as Si>Al>Fe>Ca>K>Mg,and Si-Al with K were identified as complex hydrates.Similarly,As,Hg,Cd,Pb,As,H,Cd,Pb,V,and salammoniac were observed in nanoparticles and ultrafine material.Mineral composition was detected in the order of quartz>mullite>calcite>kaolinite>illite>goethite>magnetite>zircon>monazite,in addition to salammoniac,a tracer of volcanic sources.The foregoing analysis reflects the importance of carrying out more studies relating the influence of volcanic emissions in road dust in order to protect human health.The road dust load(RD₁₀)ranged between 0.8 and 26.8 mg m^?2in the city.     

Geochemistry and petrogenesis of Late Ladinian OIB-like basalts from Tabai, Yunnan Province, China

Major and trace elements analysis has been carried out on the Late Ladinian Tabai basalts from Yunnan Province with the aim of studying their petrogenesis. Their SiO2 contents range from 43.63 wt.% to 48.23 wt.%. The basalts belong to the weakly alkaline(average total alkalis Na2 O+K2O=3.59 wt.%), high-Ti(3.21 wt.% to 4.32 wt.%) magma series. The basalts are characterized by OIB-like trace elements patterns, which are enriched in large ion lithosphile elements(LILE) including Rb and Ba, and display negative K, Zr and Hf anomalies as shown on the spider diagrams. The Tabai basalts display light rare-earth elements(LREE) enrichment and are depleted in heavy rare-earth elements(HREE) on the REE pattern. Those dates indicate that the parental magma of the Tabai basalts was derived from low-degree(1%–5%) partial melting of garnet peridotite. The magma underwent olivine fractional crystallization and minor crustal contamination during their ascent. The Tabai basalts were related to a relaxation event which had triggered the Emeishan fossil plume head re-melting in the Middle Triassic.     

The Petrology and Geochemistry of Listwaenite in the Sartohay Ophiolitic Melange of West Junggar, Xinjiang, China

The west Junggar,located in the eastern part of Balkash-Junggar tectonic province,is a major component of the core of the Central Asian metallogenic region.This area is characterized by occurrences of ophiolitic mélanges,such as the Sartohay ophiolitic mélange in the NE and the Tangbale ophiolitic mélange in the west.As a hydrothermal alteration product of serpentinite in the Sartohay ophiolitic mélange,listwaenite lenses are gold-mineralized and crop out on surface in the ophiolitic mélange via weathering of exhumated hanging wall of fault zone.Listwaenite is mainly composed of magnesite,quartz,dolomite,and trace amounts of mariposite,chromian spinel,talc and sulfide.A vertical thermal gradient model for the hydrothermal alteration shows that serpentinite would first be transformed to talc schist,then into listwaenite as the ophiolite slices continued to rise along shear zone,with XCO2,oxygen and sulfur fugacity increase and temperature decrease.Both serpentine and magnetite were progressively destroyed during the transformation from serpentinite to talc schist,andcompletely vanished in listwaenite,while mariposite generated in weakly deformed to mylonitized listwaenite.Concentrations of most trace elements including high field strength elements and metallogenic elements,increasing from undeformed,through weakly deformed,to mylonitized listwaenite,show a positive correlation with deformation degree and content of apatite,rutile,monazite,zircon and sulfide in listwaenite.The shear zone served as pathways for percolation and accumulation of fluid and trace elements during the metasomatism from serpentinite to listwaenite.Compared to undeformed listwaenite,mylonitized listwaenite will be more favorable to be fractured and brecciated due to more intense shearing,which caused strong metasomatic reaction and then induced trace element-bearing mylonitized listwaenite.     

Cascaded Evolution of Mantle Plumes and Metallogenesis of Core- and Mantle-derived Elements

Mineral deposits are unevenly distributed in the Earth's crust, which is closely related to the formation and evolution of the Earth. In the early history of the Earth, controlled by the gravitational contraction and thermal expansion, lighter elements, such as radioactive, halogen-family, rare and rare earth elements and alkali metals, migrated upwards; whereas heavier elements, such as iron-family and platinum-family elements, base metals and noble metals, had a tendency of sinking to the Earth's core, so that the elements iron, nickel, gold and silver are mainly concentrated in the Earth's core. However, during the formation of the stratified structure of the Earth, the existence of temperature, pressure and viscosity differences inside and outside the Earth resulted in vertical material movement manifested mainly by cascaded evolution of mantle plumes in the Earth. The stratifications and vertical movement of the Earth were interdependent and constituted the motive force of the mantle-core movement.