Concentrations Of Various Elements Research Articles

The Mobility of Major and Trace Elements in EOC Minerals on Parent Chondrite Bodies

The combined EPMA and SIMS study of the geochemical features of olivine, low-Ca pyroxene and plagioclase in equilibrated ordinary chondrites (EOCs) has revealed the effect of thermal metamorphism on trace element concentrations in EOC silicate minerals. In ordinary chondrites of petrological type 6, trace element composition is homogenized in olivine (Zr, Al, Ti, Ca, Cr, Sr and Ba) and low-Ca pyroxene (Zr, Hf, Y, Ti, Ca, Cr, Sr, Ba and Rb). Trace element concentrations in silicate minerals of petrological types 4 and 5 remain unequilibrated. Although variations in trace element concentrations have decreased, their concentrations in EOC minerals remain unchanged with an increase in the grade of thermal metamorphism. Plagioclase in equilibrated ordinary chondrites displays a consecutive decrease in trace element concentrations with a rise in the peak temperature of thermal metamorphism measured with an olivine-Cr spinel geothermometer. Chondrites of petrological type 4 show a metamorphic temperature of 670–682 °C, and meteorites of petrological type 5 reached equilibrium at a temperature of 687–700 °C. Chondrites of petrological type 6 show the highest metamorphic temperature of 734 °C. The temperatures are generally consistent with the concentric model of parent chondrite bodies.

Determination of Minor and Trace Elements in Breast Milk of Lactating Mothers in Early Lactation from Tehran, Iran Using Neutron Activation Analysis Method.

This study aimed to evaluate the concentrations of both essential and non-essential elements in the breast milk of lactating mothers from Tehran, Iran, during the colostrum period. Neutron activation analysis (NAA) was used to measure the element concentrations. Additionally, the study assessed how these element concentrations were influenced by maternal factors such as age and economic status. Breast milk samples were collected from 95 lactating mothers, aged 18 to 41, during the early lactation phase, specifically within the colostrum period (2-7 days postpartum). The colostrum milk samples were freeze-dried, powdered, and irradiated at the Tehran Research Reactor for neutron activation analysis (NAA). This method was used to measure the concentrations of essential elements-calcium (Ca), potassium (K), sodium (Na), chlorine (Cl), and iodine (I)-as well as non-essential elements-aluminum (Al), bromine (Br), and rubidium (Rb). Descriptive statistics, including mean, median, maximum, minimum, and standard deviation, were calculated for each element. Statistical analyses, such as Pearson's correlation, were performed to assess relationships between the concentrations of various elements. Additionally, t-tests and p-values were employed to evaluate differences in element levels across maternal age groups (17-34 years vs. 35-45 years) and economic status (high/middle vs. low). The mean concentrations of the elements in dry breast milk powder samples were: Al = 6.9mg/kg, Br = 11.9mg/kg, Ca = 2.757mg/g, Cl = 7.836mg/g, I = 1.22mg/kg, K = 5.853mg/g, Na = 4.932mg/g, and Rb = 3.69mg/kg. Significant correlations were found between element pairs, such as Na-Cl, Br-Cl, Na-Br, Rb-K, and I-Cl. Maternal age significantly influenced bromine concentrations, with older mothers showing 22% higher Br levels (p = 0.038), while calcium levels were 15% lower but not statistically significant (p = 0.20). Maternal economic status significantly impacted calcium and potassium concentrations, with higher levels observed in mothers from better economic conditions (p = 0.02 and p = 0.025, respectively). This study highlights the elemental composition of breast milk samples of lactating mothers in Tehran and shows that maternal factors, such as age and economic status, can significantly influence the concentrations of specific elements in breast milk.

Seasonal dynamics of chemistry in an Arctic glacier-fed river

Arctic rivers, intricately linked to fjord systems, wield significant influence over the geochemical and biological dynamics of the upper Arctic Ocean, providing it with freshwater, nutrients, suspended particles, and potentially harmful pollutants. To comprehend the full picture of the Arctic ecosystem, it is crucial to understand how these rivers vary across regions and seasons, especially considering ongoing climate changes. However, comprehensive studies that address long-term observations and seasonal variations in Arctic rivers' geochemical composition remain scarce. In this study, we present comprehensive long-term investigations of the seasonal variations in elemental concentrations in Bayelva, a high Arctic glacier-fed river. By analyzing 224 surface water samples, collected during different seasons between 2011 and 2020, we elucidate the diverse influences of marine, geological and atmospheric factors on the river chemistry. Our findings underscore the importance of marine-influenced snowmelt in the early flow season, which leads to elevated concentrations of marine and trace elements in the runoff water at the onset of melting, with concentrations subsequently decreasing as the snow melting continues. Glacial meltwater dominates the river chemistry during the peak flow season, during which elemental concentrations are at their lowest. Late flow season exhibits high elemental concentrations, primarily driven by weathering processes. Additionally, heavy rain and freezing events play a crucial role in sudden alterations in river chemistry. We highlight the dynamic response of Arctic river systems to such environmental drivers as key players in transporting essential micro- and macro-nutrients, as well as potentially harmful pollutants to adjacent fjord systems. Given their susceptibility to climate change, continuous monitoring is essential for understanding future changes. This study provides data for a better foundation for accurate climate modeling of biogeochemical systems in the Arctic environment.

ВЫНОС МИКРОЭЛЕМЕНТОВ ФУМАРОЛАМИ АВАЧИНСКОГО ВУЛКАНА (КАМЧАТКА)

The trace element composition of high-temperature gases of Avachinsky volcano was investigated. For that purpose 25 samples of gas condensates and sublimates deposited in four quartz tubes were analyzed. The total average concentration of trace elements (excluding S, Cl, F, Si) in the condensates was 87 mg/l, the maximum 210 mg/l, among which B, K, Na, Br, As predominated. A large number of samples taken over a period 2013–2023 allowed us to evaluate the variations of element concentrations, their dependence on fumarole temperature and the season of sampling. The enrichment factors normalized for magnesium, made it possible to determine the elements transported in the plume in the form of volatile compounds (S, Cl, Te, I, B, Br, Cd, As, F, Re, Se, Bi, Tl, Hg, Sn, Sb, Pb, etc.) and in the form of silicate aerosol (Ti, Fe, Ga, Al, Ca, Mn, REE et al.). The ore element emission by Avachinsky volcano is comparable to that of Mutnovsky volcano (Kamchatka) and significantly lower than the emission by volcanoes in the stage of stationary degassing, such as Kudryavy and Pallas Peak (Kuril Islands), which can be explained by higher concentrations of HCl in the gases of the latter.

Universally Applicable Methods for Comprehensive Risk Assessment of Elemental Impurities in Vitamin A and D Preparations

Background: Vitamin A and D deficiency in children is a common public health problem. In China, almost all children are administered vitamin A and D preparations daily and over the long term. Children are sensitive to elemental impurities, including heavy metals. However, there are no regulatory requirements or reports on the risk assessment of elemental impurities in marketed vitamin A and D preparations. Objective: The aim of this study was to propose an accurate and efficient method suitable for samples from different manufacturers to detect elemental impurities and conduct risk assessments according to the ICH Q3D guidelines. Methods: We developed a universally applicable digestion method for capsules and an ICP–MS method for quantitative analysis of 28 elemental impurities in vitamin A and D formulations. These methods were validated according to the USP 233 guidelines. Elemental impurities in 15 batches of vitamin A and D products from 10 manufacturers and their capsule shells were determined, and risk assessment was conducted according to the International Council for Harmonization Q3D guidelines. Results: All elemental impurities of toxicological concern met the Q3D requirements. However, the concentrations of various elements, including those of lead (not detected to 4.1 µg/g), arsenic (not detected to 7 µg/g), aluminum (not detected to 888 µg/g), and palladium (not detected to 36 µg/g), varied markedly. Moreover, the lead content in one batch from one manufacturer exceeded the control threshold. Conclusion: In this study, we successfully developed an effective digestion method for processing capsules containing samples from different sources and a sensitive ICP–MS method for quantitative determination of 28 elemental impurities in vitamin A and D preparations. ICP–MS should be implemented for the evaluation and control of elemental impurities in vitamin A and D preparations. This will ensure safe long-term vitamin A and D supplementation in children

Determination and safety evaluation of metal element contents of Oviductus Ranae produced from <i>Rana dybowskii</i> by pond culture–forest grazing relay model in Heilongjiang Province, China

The aquatic products of grazing ecological culture exhibit a strong reliance on the production environment system, which may result in heavy metal contamination. In this study, 24 elements (Ag, Al, As, Ba, Cd, Co, Cr, Cs, Cu, Fe, Ga, K, Mg, Mn, Na, Ni, Pb, Rb, Se, Sr, Tl, U, V, Zn) were determined for Oviductus Ranae (OR) from more than 1,000 individuals of Rana dybowskii produced by pond culture–forest grazing relay mode from six major production areas in Heilongjiang Province, China. Furthermore, we assessed the associated health risks. Our findings indicate that most of these 24 metal elements were detected in OR at a detection rate of 100%, with the exceptions being As (98.0%), Ga (98.0%), Co (98.0%), V (94.0%), Cd (89.0%), Pb (76.0%), Cs (74.0%), Tl (35.0%), and U (not detectable). Variations in element concentrations were significant across the six sampling sites, with characteristic elements identified to account for spatial differences. The total target hazard quotient was determined to be 0.152 in Heilongjiang Province, thereby suggesting a relatively low health risk associated with consuming OR from this region’s production systems according to existing standards and guidelines. Nevertheless, special attention is needed for monitoring the habitat environments of R. dybowskii from two sampling locations showing heightened pollution levels.

Elemental Profiling with Reference to Metal Index to Study Pollutant Load in Northern River of India

Present light was to determine elemental load in Sirsa river ecosystem to know the concentration of toxicants in this Sutlej river’s tributary that act as a gutter for industrial effluents of Baddi region. The inductively coupled plasma mass spectroscopy was used to detect concentration of elements in the department of biochemical engineering and biotechnology at IIT Delhi and the collected data was further analyzed statistically using one way ANOVA at (p≤0.05) followed by post hoc Duncan’s test to predict degree of variations and comparative profile in Table 1. The application of metal index was also performed to estimate water quality and co-related it with health hazards. Variations in concentration of elements was reported near common effluent treatment plant on pollutant Nallah (S2) in deceasing order read as Mg>Na>Ca>B>Zn>Cu>Mn>Fe>Mo>Al>Tl>Se in ppb. The concentration of elements reported at S1, S2, S3 were within permissible limit of WHO and Bureau of Indian Standards, except the value of Boron, Magnesium and Thallium were exceeded these guidelines constantly at site S2 of study area.The metal index values at S1, S2 and S3 were 1.55, 5.80 and 2.57 respectively. The site S2 was affected strongly due to presence of elemental dust and un-treated waste water discharged by chemical industrial units of Baddi region. This site (S2) was nearer to common effluent treatment plant on the bank of Sirsa river and found to be unsuitable at all with more value of metal index. It was also viewed to adopt such scale indices to estimate drinking water quality with respect to concentration of elements after equal interval of time; as there may be seasonal change in the load of debris due to rate of pollutants dumping in the riverine ecosystem which is directly proportional to the content of elements. The load of pollutants in water system was underlined to know the impact of inorganic waste discharges on water quality of river in this region of Himachal Pradesh along industrial belt.

Multiple approaches for heavy metal contamination characterization and source identification of farmland soils in a metal mine impacted area

Heavy metal and metalloid contamination of farmland soils are closely related to human health. Soil contamination caused by small-scale mining activities has been largely neglected, especially in developing countries. This research studies the characteristics and the source of heavy metals and metalloids in farmland soils in the Bailing Cu–Zn deposit area in Northeastern China through multiple approaches. Geochemical mapping conducted by portable X-ray fluorescence (pXRF) spectrometry and elemental fractionation analysis (sequential extraction) revealed the spatial variations in elemental concentration and fractionation of the farmland soils. The elemental variations in the sediment and water samples in a stream passing by the farmland were determined by inductively coupled plasma mass spectroscopy (ICP-MS) and inductively coupled plasma atomic emission spectroscopy (ICP-AES) analysis. Results indicate elevated As, Zn, Fe, and Mn concentrations in the west bank of the farmland and the associated environmental risks caused by extremely high As concentrations (>500 mg kg−1). The upstream mining activities are identified as a dominated source of contamination in the studied farmland based on the variations of elemental concentrations and fractionations, as well as multivariate analysis results. This study revealed potential ecological risks caused by heavy metal and metalloid contamination in farmland soils in the metal mine impacted area and the stream as a primary pathway for the migration of pollutants associated with mining activities.

Impact of Environmental Conditions on Soil Geochemistry in Southern Kazakhstan

This study investigated the elemental composition of soils in Kyzylorda and Turkestan (southern Kazakhstan), an area rich in natural resources but facing potential environmental threats from industry and agriculture. The goal was to establish baseline geochemical values and assess soil contamination risks. Soil samples were collected from across the region and analyzed using ICP-MS and INAA techniques, providing a comprehensive profile of 72 elements. Statistical analysis revealed significant variations in elemental concentrations, with enrichments observed for specific elements when compared with reference values. Notably, both regions shared a core set of elements including rare earth elements (yttrium series: holmium, erbium, thulium), noble metals (gold, platinum, ruthenium, palladium), and tungsten. Enrichment patterns, however, provided distinct insights. Rare earth element enrichments likely reflect the region’s geology, while elevated radioactive elements necessitate further investigation to understand potential environmental and health risks. Enrichment of iron group elements might be linked to a combination of geological factors and anthropogenic activities like mining or industrial processes. A significantly higher number of elements exceeded background levels in Kyzylorda compared with Turkestan, suggesting greater element accumulation in Kyzylorda’s soil. This difference could be attributed to variations in regional geology or historical anthropogenic activities. The established geochemical baseline for 72 elements and the identified areas of potential contamination will inform land management practices, guide future environmental monitoring efforts, and ultimately contribute to the safeguarding of public health in southern Kazakhstan.

Levels of Potentially Toxic and Essential Elements in Water and Estimation of Human Health Risks in a River Located at the Interface of Brazilian Savanna and Amazon Biomes (Tocantins River).

The Tocantins-Araguaia basin is one of South America's largest river systems, across three Brazilian states (Maranhão, Tocantins, and Pará), within the Legal Amazon region. Despite draining extensive Cerrado savanna and rainforest ecosystems, it has suffered significant degradation, notably in the past 40 years. Human activities, including agricultural expansion, deforestation, and the introduction of non-native species, have worsened the environmental damage, which is alarming since many residents and villages along the middle Tocantins River rely on it for water supply, recreation, and fishing. This study assessed the concentration of potentially toxic and essential elements in water samples from four sampling sites distributed along the middle Tocantins River. The monitoring occurred throughout 2023, involving the measurement of parameters both on-site and in the laboratory. Water quality and its health implications were evaluated using the Weighted Arithmetic Water Quality Index (WAWQI), the Water Quality Index (WQI), and the health risk assessment index. The levels of aluminum, copper, iron, magnesium, and selenium exceeded legal standards. Seasonal fluctuations indicate a complex dynamic influenced by climatic or seasonal factors, with February showing the highest values. Site P1, located in urban areas, exhibited elevated mean concentrations for conductivity, total dissolved solids (TDS), and chlorophyll, indicating the need for continuous monitoring. The nitrogen concentrations at P1 raise concerns regarding drinking water quality, which is a concern for the region's residents who use untreated river water. Despite seasonal variations in element concentrations, the overall WAWQI categorized all sections as "Excellent," and the WQI rated as "Good." Human health risk assessments detected no risks, but continuous monitoring and interventions are crucial for sustained water quality improvement.

Critical differences between typical arc magmas and giant porphyry Cu ± Au systems: Implications for exploration

Abstract Porphyry Cu, and porphyry Cu-Au deposits, are associated with arc magmatism and their ore-forming systems generally follow the magmatic evolution of typical arcs. However, most arc magmas are barren and giant economic porphyry Cu ± Au deposits are rare. In this study, we model variations in rare earth element concentrations in the evolving arc magmas and giant porphyry Cu ± Au systems to quantify the percentage of the fractionating minerals required to produce the observed changes. We find that, during the andesitic stage of fractionation, ore-forming systems in thick crusts fractionate ~35% more amphibole than an average of thick arc magma systems (the thick-crust reference suite) and that ore-forming systems in thin crusts fractionate twice as much amphibole as their equivalent thin-arc magma reference suite. Thick-crust ore-forming suites also fractionate ~50% less plagioclase, and thin-crust ore systems ~40% less plagioclase, than their associated reference suites during the same andesitic stage of fractionation. Taken together, these observations imply that ore-producing magmas are appreciably wetter than their associated barren reference suites. Our modelling also shows that 80% more amphibole is required to reproduce the andesite stage of fractionation in the thick-crust reference suite than in its thin-crust equivalent, suggesting that magmas produced under thick crusts are wetter than those produced under thin crusts. On the other hand, the chalcophile element contents of the thick- and thin-crust ore-forming systems are similar to and higher than those of the thick- and thin-crust reference suites, respectively. Therefore, we suggest that the high water content plays a critical role in the formation of giant porphyry Cu ore in thick crusts, whereas both high chalcophile contents and high water contents are required to form giant porphyry Cu-Au deposits in thin crusts. The high fraction of amphibole fractionation in giant economic porphyry suites, compared with their relevant reference suites, results in lower Y in the ore-associated suites and this difference increases with fractionation. As a consequence, plots of Y against MgO can be used to identify porphyries that have economic potential and are preferred to Sr/Y plots because they are less affected by the intense alteration associated with giant porphyry Cu ± Au deposits.

Assessment of the impact of irrigating with treated wastewater on soil and crop trace metal accumulation

ABSTRACT Water scarcity is growing quickly, especially in the arid and semi-arid regions along with the growing population. So, using treated wastewater in agricultural irrigation presents a sustainable approach, enhancing soil quality, increasing organic carbon levels, and improving crop productivity are achieved through this approach, concurrently reducing the need for chemical fertilizers. Yet, escalating industrial effluent discharge raises concerns regarding trace metals in wastewater and associated health risks. Our study in the Tenth of Ramadan City focused on employing secondary treated mixed industrial and municipal wastewater for olives, mandarins, and guavas. Sampling wastewater, soil, and plant parts, we analyzed their properties and trace element concentrations, employing Visual MINTEQ for geochemical speciation. Adhering to the international guidelines, the wastewater exhibited acceptable pH and alkalinity but showed concerning trace element levels for irrigation. Differences in soil composition and trace element concentrations suggest potential contamination in soils irrigated with wastewater, raising concerns about health risks associated with elevated metal levels in plants. Variations in trace element concentrations in guavas, olives, and mandarins’ leaves and fruits were observed, with efficient translocation in olives, while mandarin and guava displayed reduced efficiency. Bioaccumulation Factor trends indicated species-specific metal uptake differences. Waste “Minimization Prioritization Tool categorized” trace element levels as of low concern. Daily Intake of Trace Metals and Health Risk Index highlighted the need for health risk assessment, especially for elevated Ni in mandarins and guavas. Regression findings emphasized soil factors influencing metal uptake in plants, highlighting the need for vigilant soil management to curb trace element contamination in agriculture, ensuring both food safety and environmental health. Therefore, water reuse adds contributes to sustainable development, which is three dimensions; Economic, Social and Environmental. It improves economics to utilize water that would be otherwise wasted, and by making water more productive. It improves the social dimension by addressing water scarcity and satisfying the increasing water demand for sustainable livelihoods. It also improves the environment by increasing wastewater treatment levels and reducing pollution.

Sources and distribution of trace elements in surface snow from coastal Zhongshan Station to Dome A (East Antarctica)

The spatial distribution and possible sources of Al, As, Cd, Fe, Mn, Pb, Sb, Ti, V, and Zn were investigated in 120 samples of surface snow collected along a ∼1260 km long traverse from coastal Zhongshan Station to the Antarctic ice sheet summit (Dome A or Dome Argus, at 4093 m a.s.l.). The chemical composition of snow samples was analyzed using microwave-assisted acid treatment with HNO3/HF to determine element concentrations, reflecting their abundance in the Earth's crust. The observed relative concentration pattern of elements in snow suggests a predominant contribution from soil and rock dust particles. The spatial distribution of total element concentrations along the traverse revealed higher values in inland areas compared to coastal areas. The annual deposition flux of elements in each sampling site indicates a significant decreasing trend in Al, Ti, Zn, Fe, Cd, As, and Pb from the coast to inland areas. Significant variations in element concentrations and fluxes observed along the Antarctic traverse suggest a notable influence of distance from the coast on snow deposition patterns. Soil dust from coastal ice-free areas and human activities in scientific stations are the primary sources of analyzed elements in coastal snow, with marine biogenic emissions playing a marginal role, likely contributing to As and Cd. The contribution of sea salt spray to surface snow element concentrations in the East Antarctic traverse is negligible. An analysis of backward trajectories confirmed that long-distance transport from the South American continent and local Antarctic research stations potentially contributes to Antarctic snow elements.

The Role of Fe, S, P, Ca, and Sr in Porous Skeletal Lesions: A Study on Non-adult Individuals Using pXRF.

Portable X-ray fluorescence is a new tool in the study of human bone. This research aims to investigate if variations in bone elemental concentrations are related with porous skeletal lesions (PSLs). One hundred well-preserved non-adult skeletons aged 0-11years were selected from the archaeological site Convent of São Domingos, Lisbon (18th-19th century). Measuring a standard reference material and calculating the technical error of measurement assured elemental data reliability. Moreover, measuring soil samples excluded possible contamination of bones with elements from the soil, except for Pb. Additionally, the Ca/P ratio indicates maintenance of bone integrity. Cribra cranii, orbitalia, humeralis, and femoralis were recorded as present/absent, and the estimated intra-/inter-observer errors were low. The multivariate analysis found higher odds of having cribra orbitalia (OR = 1.76; CI = 0.97-3.20) and cribra femoralis (OR = 1.42; CI = 0.73-2.74) in individuals with lower Fe and higher S. Furthermore, higher levels of P, Ca, and Sr increased the odds of individuals developing cribra femoralis (OR = 2.30; CI = 1.23-4.29). Age also correlated with increased odds of exhibiting cribra orbitalia (OR = 1.86; CI = 0.94-3.68), cribra femoralis (OR = 6.97; CI = 2.78-17.45), and cribra humeralis (OR = 8.32; CI = 2.71-25.60). These findings suggest a shared etiology for these three cribras, contrasting with the higher Fe levels in individuals with cribra cranii. Lower Fe and higher S levels in individuals with cribra suggest a complex etiology, possibly involving conditions like megaloblastic or chronic disease anemia(s). Age-related elemental changes support the hypothesis that age influences cribra frequencies. This study highlights PSL complexity and opens new avenues for research.

Characterization of cross-continental PM2.5: Insights into emissions and chemical composition

Atmospheric fine particulate matter (PM2.5) is a critical indicator of air quality, with substantial implications for human health. Understanding the emission sources and chemical composition of PM2.5 is crucial for mitigating possible adverse health effects. This study spans five diverse cities on three continents from north and south hemisphere: Stockholm (Sweden), Kyoto (Japan), Limeira, Ribeirão Preto, and Cáceres (Brazil). Our objective was to assess PM2.5 chemical composition and regional and long-range transport influences to identify the main sources of particulate air pollution at these cities during the winter/dry seasons. All studied cities but Kyoto exhibited PM2.5 levels above World Health Organization (WHO) guidelines, with the Brazilian cities experiencing the highest fine particle pollution levels, implying increased adverse health risks. We observed significant variations in concentrations of polycyclic aromatic compounds (PACs), monosaccharide anhydrides (MAs), and inorganic elements. Limeira exhibited the highest levels of total PACs (median level of 12.4 ng m−3), while Cáceres displayed high variability of PACs, most likely due to episodic regional wildfire events. MA concentrations were significantly higher in Limeira and Ribeirão Preto and together with elevated levels of retene and potassium (K) they suggested a substantial influence of biomass burning. Backward air mass trajectory analysis suggested widespread Amazon and Savanna wildfires along with local fires as main contributors for these sites. All source identification approaches highlighted differences among the cities, with Stockholm and Kyoto showing influence of sources related to traffic emissions, waste burning, and long-range transport, and Brazilian cities traffic, industrial, biogenic, and more evident biomass burning. This cross-continental study provides valuable insights into PM2.5 composition and emission sources, emphasizing the impact of different emissions on air quality. Our findings underscore the importance of local strategies to mitigate air pollution and protect public health, especially in regions where PM2.5 levels consistently exceed recommended guidelines.

Diagenetic development of rhizoliths in the Ironshore Formation (Pleistocene) of the Cayman Islands

Rhizoliths in the Ironshore Formation on the Cayman Islands, up to 12 cm in diameter and 1 m long, developed in skeletal grainstones that accumulated on sand flats above high tide level. Internally, these well-preserved rhizoliths are characterized by well-defined concentric zones, centered around the central root opening, that reflect radial variations in calcite–aragonite content, decreases in micrite content, increases in porosity, and radial variations in trace element (e.g., Ca, Ni, S, Si, and Sr) concentrations. The stable isotopes, δ13C and δ18O, which vary in accord with the internal zones are more variable than the δ13C and δ18O of the host sediments. For the rhizoliths there is a high correlation between the δ13C and δ18O values and the calcite content. The contrast between the rhizoliths and their host sediments is largely a reflection of the more intense diagenetic processes that were largely mediated by the microbial populations that were concentrated in the rhizosphere that developed around each plant root. Microbial activity, which mediated micritization of the skeletal sands and micrite precipitation in the intergranular pores, was largely responsible for development of the internal zonation in the rhizoliths. Use of the δ13C values to determine if the rhizoliths developed in association with C3 or C4 vegetation failed because the δ13C values correlate with the calcite content that developed largely as diagenetic products.

Mathematical Model of Closed Microecosystem “Algae – Heterotrophic Bacteria”

Model of closed microecosystem “algae - heterotrophic bacteria” is proposed in this paper. Mathematical model is the Cauchy problem for system of nonlinear ordinary differential equations. To develop the model the Liebig’s law of the minimum is consistently used for both specific rate of biomass growth and specific death rate of algae and bacteria cells. To describe the specific rate of substrate utilization by algae and bacteria the Andrew’s model (substrate inhibition) is used. It is assumed that specific death rate of algae and bacteria cells increases with decreasing substrate concentration. It is also assumed that carbon and nitrogen are main biogenic elements, and in the system they are in the form of mineral substrate (CO2, NO2, NO3, NH4) and biological substrate (proteins, lipids and carbohydrates). Mathematical model describing time variations in concentration of elements of microecosystem is formulated under the following assumptions: 1) stoichiometric coefficients of algae and bacteria cells are constant in the development of microecosystem; 2) utilization of carbon and nitrogen by algae and bacteria occurs independently; 3) oxygen produced by algae cells during photosynthesis completely covers the demand for oxygen for algae and bacteria cells. To verify the proposed model experimental data for microecosystems «Clorella vulgaris – Pseudomonas sp.» и «Scenedesmus obliquus – Pseudomonas sp.» are used. These systems were studied in laboratory conditions, and concentrations of elements of microecosystems in stationary state were obtained. Parameters of functions describing specific rate of utilization of biogenic elements were derived from experimental data for growth kinetics of algae and bacteria. Concentration of the biomass in stationary state obtained with the use of the proposed model is in reasonable agreement with experimental data.

Spatial Variations in Element Concentrations in Saudi Arabian Red Sea Mangrove and Seagrass Ecosystems: A Comparative Analysis for Bioindicator Selection

Spatial Variations in Element Concentrations in Saudi Arabian Red Sea Mangrove and Seagrass Ecosystems: A Comparative Analysis for Bioindicator Selection

Compositional zoning of the Otowi Member of the Bandelier Tuff, Valles caldera, New Mexico, USA

Abstract The Otowi Member of the Bandelier Tuff erupted at ca. 1.60 Ma from the Valles caldera (New Mexico, USA). It consists of as much as 400 km3 (dense rock equivalent) of strongly differentiated high-silica rhyolite and shows systematic upward variations in crystallinity, mineral chemistry, and trace element concentrations through its thickness, but the major element composition is almost constant and is near the low-pressure granite minimum. Incompatible trace elements in whole pumice fragments and glasses show well-correlated linear covariations. Upward zoning to lower abundances of incompatible trace elements is accompanied by development of overgrowths on quartz and alkali feldspar, although earlier-formed interiors of quartz and feldspar have near-constant compositions throughout the tuff, modified by cation diffusion in the case of feldspar. Melt inclusions in remnant quartz cores show diverse Pb isotope ratios, pointing to a wide range of distinct protoliths that contributed rhyolitic melt to the Otowi magma. Mineral thermometers suggest a modest temperature gradient through the melt body, perhaps of 40 °C, at the time of eruption. Chemical, textural, and mineralogical variations and volume-composition relations through the tuff are consistent with an origin for zoning by melting of a high-crystallinity cumulate layer beneath cognate supernatant liquid to produce denser, remobilized liquid of accumulative composition (i.e., the “modified mush model”). Melting may have occurred in several episodes. The latest of these episodes, probably thousands of years prior to eruption, introduced new rhyolitic liquid into the system and was associated with a thermal excursion, recorded in core compositions of pyroxene, during which much of the earlier crystal mass was dissolved. This left inherited cores and interiors of accumulated quartz and feldspar mantled with new growth having less-evolved compositions (higher Ti, Sr, and Ba). Changing solubility of zircon during cumulate melting produced a reversal of Zr concentrations. There is no clear petrologic evidence of a recharge eruption trigger; nonetheless, compositional zoning resulted mainly from repeated recharge-induced remobilization of quartz-feldspar cumulate. The Otowi system was built, evolved, and modified by several events over the course of a few hundred thousand years.

Neutronic Activation of Amazon Technogenic Deposit Soil Used as Raw Material in Brick Manufacture

Considering the extraction of soil from Technogenic Deposits, may result in the risk, this article investigated whether in the brick making process, there is a possibility that chemical elements, considered linked to human illness, may have evidence of release to the environment. The adopted strategy was to subject both the soil, as well as the brick manufactured with this soil, to the Neutronic Activation test, later, through the mass balance, to verify the variations in the global concentrations of chemical elements. The results show that of the 27 elements analyzed, 25 showed a reduction in their concentrations after the burning of the soil. As the systematic literature review points out, the release of these chemical elements to the environment, is intrinsically linked to the decrease in the environmental quality of the built environment, therefore, it is an indication of possible risks for human health.