Distribution Of Selenium Research Articles

Distribution and enrichment patterns of selenium in the Ediacaran and early Cambrian strata in the Yangtze Gorges area, South China

The distribution and enrichment patterns of selenium (Se) in the E-Є1 strata in the Yangtze Gorges area of South China were obtained. The geochemical characteristics of the significantly and non-significantly enriched strata of Se were analyzed.The observed enrichment factor (EF, relative to the upper continental crust) and concentration coefficient (CC, relative to the similar lithology in Eastern China) both suggest that Se is the most enriched/concentrated (SeEF=26.97, SeCC=48.04) among the analyzed 23 trace elements the E-Є1 strata. The normalized enrichment factor (EF′, EF after Al or Th normalized) shows Se is secondly enriched (SeEF′=218.73), which is slightly lower than cadmium (CdEF′=288.46) but significantly higher than the third enriched trace element arsenic (AsEF′=97.49). Se concentrations in the E-Є1 strata vary from Yanjiahe (54.45)>Doushantuo (24.72)>Dengying (2.48)>Shipai (1.95)>lower Tianheban (1.24) Formations. Se concentrations in the E-Є1 strata are best displayed on natural logarithm normal quantile-quantile (Q-Q) plots and shown as a positive-skewed distribution pattern. The Se significantly enriched (EF>10) strata sequences mainly include the lower and upper Doushantuo member II (DST-II), top DST-III, DST-IV, the basal and upper Yanjiahe Formation, and lower and upper Shuijingtuo Formation. Geochemical characteristics indicate that Se concentrations in the significantly enriched strata were generally influenced by terrigenous detrital as well as the combined action of single or multiple factors, such as hydrotherm, volcanic debris and deep source. Moreover, pyrite and organic matter promoted the enrichment of Se in the upper DST-II, DST-IV, upper Shuijingtuo Formation and lower DST-II, upper Shuijingtuo Formation, respectively. The Se concentrations in the not significantly enriched strata (except for DST-I, middle Shuijingtuo Formation, Shipai Formation and lower Tianheban Formation) were also influenced by terrigenous detrital, but other enrichment activities (e.g., hydrothermal, volcanic debris, and deep source) were generally insignificant.

Uptake and Utilization of Selenium from Selenoprotein P

Selenoprotein P (SELENOP) is a serum glycoprotein that is required for proper selenium distribution in mammals, particularly in supplying selenium to the brain and testes. As the sole mechanism for providing essential selenium to developing spermatozoa, SELENOP metabolism is central to male fertility in all mammals. In addition, this process is important for proper brain function, especially under conditions of limited dietary selenium. Several specific and nonspecific mechanisms for SELENOP uptake in target tissues have been described, but the utilization of SELENOP as a source of selenium for intracellular selenoprotein production has not been systematically characterized. In this report, we examine the process of SELENOP uptake using a robust selenium uptake assay that measures selenium utilization in cells fed 75Se-SELENOP. Using a series of inhibitors and modulators we have identified specific regulators of the process and found that SELENOP must be in an oxidized state for uptake. This assay also demonstrates that SELENOP uptake is not highly sequence specific as thezebrafish protein is recognized and processed by mammalian cells.

The APOE ε4 Allele Is Associated with Lower Selenium Levels in the Brain: Implications for Alzheimer's Disease.

The antioxidant activity of selenium, which is mainly conferred by its incorporation into dedicated selenoproteins, has been suggested as a possible neuroprotective approach for mitigating neuronal loss in Alzheimer's disease. However, there is inconsistent information with respect to selenium levels in the Alzheimer's disease brain. We examined the concentration and cellular compartmentalization of selenium in the temporal cortex of Alzheimer's disease and control brain tissue. We found that Alzheimer's disease was associated with decreased selenium concentration in both soluble (i.e., cytosolic) and insoluble (i.e., plaques and tangles) fractions of brain homogenates. The presence of the APOE ε4 allele correlated with lower total selenium levels in the temporal cortex and a higher concentration of soluble selenium. Additionally, we found that age significantly contributed to lower selenium concentrations in the peripheral membrane-bound and vesicular fractions. Our findings suggest a relevant interaction between APOE ε4 and selenium delivery into brain, and show changes in cellular selenium distribution in the Alzheimer's disease brain.

English

English

Cadmium-induced testicular damage is associated with mineral imbalance, increased antioxidant enzymes activity and protein oxidation in rats

AimsCurrently, the spectrum of pathological manifestations associated with cadmium-induced testicular toxicity is poorly understood. Thus, we investigated the impact of cadmium (Cd) exposure on testicular mineral bioavailability, activity of antioxidant enzymes, testicular structure and germ cells ultrastructure Main methodsCadmium chloride was administered in a single dose to thirty rats equally randomized into five groups: Saline, 0.9% NaCl; Cd1 – Cd4, 0.67, 0.74, 0.86 and 1.1mgCd/kg. Seven days after Cd exposure, animals were euthanized and testes were collected for biochemical analysis, as well as light, scanning and transmission electron microscopy. Key findingsCadmium exposure induced dose-dependent testicular toxicity. Tubular and intertubular compartments were targets of Cd and calcium (Ca) deposits, marked structural and ultrastructural pathologic remodeling, and a reduced distribution of iron, selenium, magnesium, copper, zinc and total protein. Despite upregulation in antioxidant enzyme activities (i.e. catalase [CAT] and superoxide dismutase [SOD]), morphologic and molecular testis damage such as protein oxidation was not prevented, especially with higher doses of Cd. As non-degenerated tissue areas also presented Ca deposits, Ca imbalance was not only a consequence but also a cause of Cd-induced testis toxicity and germ cell death SignificanceTaken together, our findings indicated that Cd exposition induced dose-dependent testicular dystrophic calcification, which was associated with increased antioxidant enzymes activity and protein oxidation, mineral imbalance, germ cell calcification and death in rats. Although increased CAT and SOD activity represents a counter-regulatory reaction to cadmium-induced toxicity, this reaction is insufficient to prevent testicular pathological remodeling.

Occurrence and Distribution of Arsenic, Antimony and Selenium in Shallow Groundwater Systems of Ibadan Metropolis, Southwestern Nigerian.

Background.Arsenic, antimony and selenium contamination of groundwater is of great concern due to the potential detrimental effects to human health.Objectives.This study investigates the occurrence and distribution of arsenic, antimony and selenium in the shallow groundwater system of Ibadan metropolis, southwestern Nigeria.Methods.A total of 210 groundwater samples were collected from 35 shallow wells (3.15–7.86 m) within the residential, commercial, industrial and agricultural areas of the metropolis during the dry and wet seasons. The average daily dose intake (ADD), hazard quotient (HQ) and hazard index (HI) of arsenic, antimony and selenium exposure in groundwater were calculated from these four studied areas for children and adults.Results.Average concentrations of arsenic, antimony and selenium in groundwater ranged between 2.17±3.49 to 33.8±37.2 μg/L, 13.5±15.0 to 33.2±36.8 μg/L and 7.33±6.22 to 46.3±22.4 μg/L, respectively. A corresponding analysis relay plot showed the order of occurrence of these trace metals in groundwater to be antimony>selenium>arsenic. The principal component analysis biplot showed that arsenic, antimony and selenium were fairly distributed in all of the study areas, suggesting the influence of geogenic factors. A total of 74.3% of sampling locations had antimony levels slightly above the World Health Organization (WHO) safe limit of 20 μg/L. Statistical t testing (0.05 confidence limit) showed a significant difference in seasonal levels of groundwater antimony concentration, with the dry season recording significantly higher levels with 100% of samples exceeding WHO safe limits. The chemical of highest potential human health concern is antimony, with a non-carcinogenic HQ risk factor >2 for both age groups. The overall non-carcinogenic HI was highest in the commercial area, 4.1989 for adults and 5.2487 for children.Conclusions.Antimony in groundwater within the Ibadan metropolis raises health concerns and a concerted effort is needed to identify its sources to avoid the risk of antimony toxicity.

Distribution of selenium in the plume of the Gediz River, Izmir Bay, Aegean Sea

Distribution of selenium in the plume of the Gediz River, Izmir Bay, Aegean Sea

Secondary ion mass spectrometry as a tool to study selenium gradient in Cu2ZnSn(S,Se)4

Secondary ion mass spectrometry (SIMS) has been utilized to study compositional gradients in compound‐sputtered and annealed Cu2ZnSn(S,Se)4(CZTSSe). SIMS image depth profiling shows a non‐uniform spatial distribution of selenium and supports a mechanism where selenization is accompanied by grain growth rather than substitution of selenium for sulfur. Furthermore, SIMS depth profiles of S and Se using O2+primary ions and detecting molecular ions of the MCs+type using Cs+primary ions have been compared, where a linear relationship between the sulfur and selenium concentration suitable for compositional analysis is observed for concentrations with an Se/(S+Se) ratio in the range from 0.25 to 0.65.3D image of the spatial Se distribution in a 20 × 20 μm2grid measured with SIMS image depth profiling.

Selenium deficiency risk predicted to increase under future climate change

Deficiencies of micronutrients, including essential trace elements, affect up to 3 billion people worldwide. The dietary availability of trace elements is determined largely by their soil concentrations. Until now, the mechanisms governing soil concentrations have been evaluated in small-scale studies, which identify soil physicochemical properties as governing variables. However, global concentrations of trace elements and the factors controlling their distributions are virtually unknown. We used 33,241 soil data points to model recent (1980-1999) global distributions of Selenium (Se), an essential trace element that is required for humans. Worldwide, up to one in seven people have been estimated to have low dietary Se intake. Contrary to small-scale studies, soil Se concentrations were dominated by climate-soil interactions. Using moderate climate-change scenarios for 2080-2099, we predicted that changes in climate and soil organic carbon content will lead to overall decreased soil Se concentrations, particularly in agricultural areas; these decreases could increase the prevalence of Se deficiency. The importance of climate-soil interactions to Se distributions suggests that other trace elements with similar retention mechanisms will be similarly affected by climate change.

Effects of Nitrogen Application on Selenium Uptake, Translocation and Distribution in Winter Wheat

In order to better understand the effects of nitrogen application on accumulation, translocation and distribution of selenium in winter wheat and to provide theoretical reference for reasonable nitrogen application and increasing selenium content of grains. A pot experiment was carried out under greenhouse conditions with Se1 (0.74 mg·kg-1) or Se2 (2.60 mg·kg-1) levels of selenium, and each Se treatment was supplied with N1 (100 mg·kg-1) or N2 (200 mg·kg-1) levels of nitrogen, respectively. Selenium concentrations and biomass amounts of different parts of wheat were determined at jointing and maturity stage. The results showed that grain yield increased with increasing nitrogen levels by 13.2% and 24.0% in Se1 and Se2 treatment, respectively. Regardless of N rate, Se concentration of wheat increased with raising Se amended rate (P<0.01). Increasing nitrogen application could promote Se uptake of root and thus increase the selenium concentration of wheat grains and leaves, which was greater in Se1 treatment than in Se2 treatments. Se concentrations in wheat grain increased by 22.6% and 12.1% with the increasing N application rate in low and high Se treatment, respectively. The distribution ratios of Se in each organ ranked the same as BCFs, following the order of leaf > grain > glume > root. Increasing N fertilization increased the distribution ratio of Se in grains by 11.1% and 25.9% in low and high selenate treatments, respectively. High nitrogen fertilization could promote uptake and translocation of Se in wheat under low Se conditions, and improve Se use efficiency as well in the agricultural production.

Effects of boiling treatment upon the distributions of selenium and mercury in short-necked clam

Effects of boiling treatment upon the distributions of selenium and mercury in short-necked clam

Occurrence and Distribution of Arsenic, Antimony and Selenium in Shallow Groundwater Systems of Ibadan Metropolis, Southwestern Nigerian

Occurrence and Distribution of Arsenic, Antimony and Selenium in Shallow Groundwater Systems of Ibadan Metropolis, Southwestern Nigerian

Bioaccumulation and distribution of selenium in Enterococcus durans

Selenium is an essential nutrient for all living organisms. Under appropriate conditions lactic acid bacteria (LAB) are capable for accumulating large amounts of trace elements, such as selenium, and incorporating them into organic compounds. In this study, the capacity of selenium bioaccumulation by Enterococcus durans LAB18s was evaluated. The distribution of organic selenium in selenium-enriched E. durans LAB18s biomass was analyzed, and the highest percentage of organic selenium was found in the fraction of total protein, followed by the fractions of polysaccharides and nucleic acids. When the protein fraction was obtained by different extractions (water, NaCl, ethanol and NaOH) it was demonstrated that alkali-soluble protein showed the higher Selenium content. Analysis of protein fractions by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) revealed that selenium was present in the proteins ranging from 23 to 100kDa. The cells were analyzed by scanning electron microscopy (SEM); scanning electron microscopy/energy dispersive spectrometry (SEM/EDS) and transmission electron microscopy (TEM). SEM, TEM and SEM/EDS showed the morphology, the selenium particles bioaccumulated into and on the cells and the amounts of selenium present into the cells, respectively. Thus, the isolate E. durans LAB18s can be a promising probiotic to be used as selenium-enriched biomass in feed trials.

Geochemical Assessments and Distribution of Arsenic, Selenium, Tin and Antimony in the Surfacial Bottom Sediments of Brullus Lagoon and its Effects on Human Health

Geochemical Assessments and Distribution of Arsenic, Selenium, Tin and Antimony in the Surfacial Bottom Sediments of Brullus Lagoon and its Effects on Human Health

Distribution and Potential Health Risks of Arsenic, Selenium, and Fluorine in Natural Waters in Tibet, China

The contents of major and trace elements were analyzed in 204 different types of water samples in 138 villages across 51 counties and cities of Tibet. The average concentrations of arsenic (As), selenium, and fluorine for each water category decreased in the following order: arsenic (in μg/L: hot spring 241.37 &gt; lake 27.46 &gt; stream 22.11 &gt; shallow well 11.57 &gt; deep well 6.22), selenium (in μg/L: deep well 0.85 &gt; shallow well 0.68 &gt; stream 0.62 &gt; hot spring 0.39 &gt; lake 0.36), and fluorine (in mg/L: hot spring 2.10 &gt; lake 1.06 &gt; deep well 0.45 &gt; stream 0.20 &gt; shallow well 0.15). The distribution of arsenic in Tibetan waters ranged between 77.35 μg/L in Ali prefecture and 1.17 μg/L in Chamdo prefecture, with intermediate values of 4.39, 2.52, 2.10, 1.68, and 1.51 μg/L in the prefectures of Shigatse, Nagchu, Lhasa, Lhoka, and Nyingchi, respectively. Carbonatite is a major source of elements in these waters. The non-carcinogenic risk in Tibet caused by heavy metals in drinking water is low overall, except in Ali prefecture’s surface and shallow ground waters, which contain high levels of As. Thus, deep well water in Tibet is safe to drink.

Prediction on spatial distribution of soil selenium in typical karst area of southwest China

Prediction on spatial distribution of soil selenium in typical karst area of southwest China

Features of distribution of selenium in the food chain “soil-plant” (in winter wheat example)

Features of distribution of selenium in the food chain “soil-plant” (in winter wheat example)

Distribution and Speciation of Selenium, Antimony, and Arsenic in Soils and Sediments Around the Area of Xikuangshan (China)

Selenium (Se), antimony (Sb), and arsenic (As) throughout the world naturally or anthropogenically in the environment are of great concern. In this study, the distribution and speciation of Se, Sb, and As in four types of environmental matrices (paddy soils, dry‐land soils, soil profiles, and sediments) from an antimony mine area were investigated. Significant correlations between the total Se and Sb and As contents were observed, which, in association with the geochemical fractions and species, may help predict the distribution and availability of these metalloids in mining/smelting‐impacted soils and sediments. The maximum Se, Sb, and As concentrations were found in the sediments, where a significant decrease in the soluble and exchangeable fractions and an increase in the residual fraction were observed with an increasing distance from the river's headstream. In the environment, Se, Sb, and As are commonly present as either Se(IV), Se(VI), Sb(III), Sb(V), As(III), or As(V). These inorganic forms of Se, Sb, and As, as well as methylated forms, are subject to various biogeochemical processes with natural components, such as organic matter and mineral phases. Because of the toxicity and persistency of metalloids, a better understanding of Se, Sb, and As speciation is crucial for predicting and protecting environmental health.

Selenium partitioning between slag and matte during smelting

Copper concentrates usually contain a number of minor as well as precious elements, the control of which in copper smelting processes is often a key to the quality of the anode copper produced and may also have a bearing on the overall economics of the process. During copper smelting, the copper concentrates are partially oxidized to form slag and matte. The molten slag and matte are separated from each other in the settler. The matte being heavier in density settles at the bottom of the furnace and slag being lighter in density floats over the matte and is eventually discarded off. During the separation, selenium is distributed between slag and matte. Selenium is a value added by-product of copper process. The lower recovery of selenium from the copper process is attributed to the high loss of selenium to the discarded slag. Knowledge of the distribution and form of selenium in slag and matte is very important in the control of the selenium loss, although to date very little is known regarding their distribution. The samples of slag and matte were collected from the smelter exit before their separation. Selenium was added in different proportions in the sample. The experiments involving slag-matte separation were performed at 1250°C for 4 hours of soaking time under inert atmosphere in a vertical tubular furnace. The distribution of selenium and the mechanism by which selenium is dissolved in matte and slag have been established by this study.

Controls on selenium distribution and mobilization in an irrigated shallow groundwater system underlain by Mancos Shale, Uncompahgre River Basin, Colorado, USA

Elevated selenium (Se) concentrations in surface water and groundwater have become a concern in areas of the Western United States due to the deleterious effects of Se on aquatic ecosystems. Elevated Se concentrations are most prevalent in irrigated alluvial valleys underlain by Se-bearing marine shales where Se can be leached from geologic materials into the shallow groundwater and surface water systems. This study presents groundwater chemistry and solid-phase geochemical data from the Uncompahgre River Basin in Western Colorado, an irrigated alluvial landscape underlain by Se-rich Cretaceous marine shale. We analyzed Se species, major and trace elements, and stable nitrogen and oxygen isotopes of nitrate in groundwater and aquifer sediments to examine processes governing selenium release and transport in the shallow groundwater system. Groundwater Se concentrations ranged from below detection limit (<0.5μgL−1) to 4070μgL−1, and primarily are controlled by high groundwater nitrate concentrations that maintain oxidizing conditions in the aquifer despite low dissolved oxygen concentrations. High nitrate concentrations in non-irrigated soils and nitrate isotopes indicate nitrate is largely derived from natural sources in the Mancos Shale and alluvial material. Thus, in contrast to areas that receive substantial NO3 inputs through inorganic fertilizer application, Se mitigation efforts that involve limiting NO3 application might have little impact on groundwater Se concentrations in the study area. Soluble salts are the primary source of Se to the groundwater system in the study area at-present, but they constitute a small percentage of the total Se content of core material. Sequential extraction results indicate insoluble Se is likely composed of reduced Se in recalcitrant organic matter or discrete selenide phases. Oxidation of reduced Se species that constitute the majority of the Se pool in the study area could be a potential source of Se in the future as soluble salts are progressively depleted.