Fraction Of Mn Research Articles

Measurement of Nineteen Chemical Elements in Thyroid Malignant Nodules and Thyroid Tissue Adjacent to Nodules using Neutron Activation Analysis and Inductively Coupled Plasma Atomic Emission Spectrometry

Thyroid malignant nodules (TMNs) are the most common endocrine cancer and the fifth most frequently occurring type of malignancies. The etiology and pathogenesis of TMNs must be considered as multifactorial. The present study was performed to clarify the role of some chemical elements (ChEs) in the etiology of these thyroid disorders. Thyroid tissue levels of nineteen ChEs were prospectively evaluated in malignant tumor and tissue adjacent to tumor of 41 patients with TMNs. Measurements were performed using a combination of non-destructive and destructive methods: instrumental neutron activation analysis with high resolution spectrometry of short-lived radionuclides and inductively coupled plasma atomic emission spectrometry. Results of the study were additionally compared with previously obtained data for the same ChEs in “normal” thyroid tissue. It was observed that in malignant tissue the mass fractions of Al, B, Ca, Cl, Cu, K, Mg, Mn, Na, P, S, and Si were 3.14, 4.64, 1.79, 2.26, 3.55, 1.57, 1.61, 1.57, 1.24, 2.45, 1.14, and 2.81 times, respectively, higher whereas mass fraction of I was 25.6 times lower than in the normal thyroid. In the “adjacent” group mean mass fractions of Cl and I were approximately 1.6 and 1.7 times, respectively, higher, while mean values of Ba, Ca and Sr content were 55%, 45%, and 70%, respectively, lower than in the “normal” group. In tumor Ca, Cl, Cu, K, and Sr contents were approximately 2.8, 1.4, 1.8, 1.7, and 5.4 times, respectively, higher, while I content was 43 times lower than in “adjacent” group of tissue samples. It was concluded that thyroid tissue adjacent to malignant nodules kept the main function of thyroid gland, while malignantly transformed thyroid cells lost its capacity to accumulate I. It was supposed that the excessive accumulation of Cl and I by thyroid tissue probably precede the TMNs origination and development. It was also supposed that elevated levels of Al, B, Ca, Cl, Cu, K, Mg, Mn, Na, P, S, and Si, as well as drastically reduced level of me in cancerous tissue could possibly be explored for differential diagnosis of benign and malignant thyroid nodules.

Immobilization mechanism of antimony by applying zirconium‐manganese oxide in soil

Antimony (Sb) accumulation in soil poses great potential risk to ecological environment, and its mobilization, transformation and bioavailability are controlled by its fractions and species. Hence, it is important to develop functional materials with both adsorption and oxidation that achieve detoxification and control the mobilization of Sb. In this study, the synthesized zirconium‑manganese oxide (ZrMn) could extremely promoted the transformation of antimonite [Sb(III)] to antimonate [Sb(V)], induced the bioavailable Sb shift to well-crystallized (hydr)oxides of Mn and residual fractions, and further reduced mobility and bioavailability Sb in soil. The sorption of ZrMn to Sb(III) and antimonate Sb(V) were affected by interfering ions, and to Sb(III) was a heterogeneous adsorption process. Spectroscopic characterization of XPS and FTIR suggested exchange between the hydroxyl groups and Sb was crucial in its retain and forming an electronegative inner-sphere mononuclear or binuclear bridging compound. The oxidation induced the transformation of Mn species in ZrMn, generated Mn(II) and Mn(III) exposing more reactive sites conducive to oxidation and adsorption, thus Mn oxides has a higher adsorption capacity for Sb(III). However, the Zr oxides of ZrMn presented adsorption rather than oxidation. The application of ZrMn could realize the dual effect of Sb oxidation detoxification and adsorption immobilization in soil, which provided references for Sb contaminated soil remediation.

Molecular mobility, crystallization and melt-memory investigation of molar mass effects on linear and hydroxyl-terminated Poly(ε-caprolactone)

In this work, we synthesized and investigated five linear and –OH terminated poly(ε-caprolactone)s, PCL, prepared by ring opening polymerization. The samples cover the molar mass, Mn, range from ∼4 to ∼70 kg/mol. These biobased polyesters are studied combining a sum of experimental techniques for the structure (infra-red spectroscopy, X-ray diffraction), thermal transitions (calorimetry), semicrystalline morphology (polarized microscopy) and molecular dynamics (broadband dielectric spectroscopy). In particular, upon subjecting the samples to carefully selected thermal conditions, involving extreme cases of crystal memory, namely preserved against erased memory, interesting effects were revealed. The role of Mn in PCL is initially reflected on the crystallization and, indirectly, on molecular mobility via crystallinity. For the lower Mns, the formation of interchain interactions, in particular, between the backbone carbonyls (–CO) and the chain end groups (–OH) seems to dominate, exhibiting larger temperature widths of self-nucleation (SN). On the other hand, for larger Mns the increased chain-chain entanglements (physical crosslinks) govern, resulting in favored nucleation, however suppressed SN width. The preservation of melt memory is documented by various physical processes to arise from increased fraction of bound carbonyls and result to altered crystals structuring. Then, next to presenting the effect of Mn and crystalline fraction on both the static and the dynamic glass transition, we assess in depth the molecular origins of local dynamics. We demonstrate that the expected interchain associations could be directly correlated with changes on the dielectric strength of local γ relaxation, being luckily strong in PCL, due to the involvement of the carbonyl groups, rather than on segmental dynamics (α relaxation). The latter was affected only in terms of strength and fragility, by the tight or loose semicrystalline morphology, within which the crystals may act both as factors that impose constraints to chains diffusion (low Mn) as well as spatial confinement (higher Mn). Overall, our findings demonstrate the ability to tune the final PCL properties related to crystallization (permeability, mechanical performance), which is desired envisaging future applications (e.g., biomedical, packaging).

Raised solubility in SnTe by GeMnTe2 alloying enables converged valence bands, low thermal conductivity, and high thermoelectric performance

SnTe is a promising alternative of the toxic PbTe, but the concepts of band engineering and thermoelectric performance optimization are restricted by the low solid solubility of effective dopants. Here, we demonstrate a raised Mn solubility limit of around 15% in the SnTe-GeMnTe2 medium-entropy system. Density functional theory calculations show that high doping fraction of Mn gives rise to a near-complete valence band convergence that is responsible for the obviously improved Seebeck coefficient. High-content GeMnTe2 alloying also profoundly creates multiscale microstructure for an extreme low lattice thermal conductivity. These effects yield a high ZTmax of 1.4 at 850 K and a record Vickers hardness of 1.65 GPa in (Sn0.96Sb0.04Te)0.7(Ge0.5Mn0.5Te)0.3. Stem from excellent thermoelectric and mechanical properties, the fabricated thermoelectric module comprised of our p-type SnTe exhibits a conversion efficiency of 6.1% and an output power density of 0.43 W cm–2 under a temperature gradient of 350 °C. This study opens the door for the development of SnTe-based modules, which is promising for the low-grade heat harvest at mid-low temperature.

Contents of Nineteen Chemical Elements in Thyroid Benign Nodules and Tissue adjacent to Nodules investigated using X-Ray Fluorescence and Neutron Activation Analysis

Thyroid benign nodules (TBNs) are the most common diseases of this endocrine gland and are common worldwide. The etiology and pathogenesis of TBNs must be considered as multifactorial. The present study was performed to clarify the role of some chemical elements (ChEs) in the etiology of these thyroid disorders. Thyroid tissue levels of Ag, Ca, Cl, Co, Cr, Cu, Fe, Hg, I, K, Mg, Mn, Na, Rb, Sb, Sc, Se, Sr, and Zn were prospectively evaluated in nodular tissue and tissue adjacent to nodules of 79 patients with TBNs. Measurements were performed using X-ray fluorescence and instrumental neutron activation analysis. Results of the study were additionally compared with previously obtained data for the same ChEs in “normal” thyroid tissue. It was observed that mass fractions of Ag, Cl, Co, Cr, Cu, Fe, Hg, Mn, Na, and Sc contents in “nodular” tissue were higher, while Ca and I content was lower in comparison with contents of these ChEs in normal gland. Mass fractions of Ag, Cl, Hg, Na, and Rb in “adjacent” group of samples were approximately 31, 2.7, 32, 1.6, and 1.3 times higher, respectively, than in “normal” thyroid. Contents of Cr, Fe, Sc, and Se were lower, while mass fraction of Hg and I higher in “adjacent” group of samples in comparison with nodular tissue. At that, level of I in “adjacent” group of samples was over 2 times higher than in nodular tissue and almost equals the normal value. This study provides evidence on many ChEs level alteration in nodular and adjacent to nodule tissue and shows the necessity to continue ChEs research of TBNs. The little reduced level of I content in nodular tissue could possibly be explored for differential diagnosis of TBNs and thyroid cancer.

Magnetic Phase Diagram of the MnxFe2-xP1-ySiy System.

The phase diagram of the magnetocaloric MnxFe2−xP1−ySiy quaternary compounds was established by characterising the structure, thermal and magnetic properties in a wide range of compositions (for a Mn fraction of 0.3 ≤ x < 2.0 and a Si fraction of 0.33 ≤ y ≤ 0.60). The highest ferromagnetic transition temperature (Mn0.3Fe1.7P0.6Si0.4, TC = 470 K) is found for low Mn and high Si contents, while the lowest is found for low Fe and Si contents (Mn1.7Fe0.3P0.6Si0.4, TC = 65 K) in the MnxFe2−xP1−ySiy phase diagram. The largest hysteresis (91 K) was observed for a metal ratio close to Fe:Mn = 1:1 (corresponding to x = 0.9, y = 0.33). Both Mn-rich with high Si and Fe-rich samples with low Si concentration were found to show low hysteresis (≤2 K). These compositions with a low hysteresis form promising candidate materials for thermomagnetic applications.

Sequential extraction and risk assessment of pollutants from one major tributary of the Ganga

Abstract The geochemical fractionation of toxic heavy metals Cd, Pb, Cr, Co, Mn, Ni, Cu, Fe and Zn was investigated in 10 different sites of river bed sediments (up, mid and downstream) of Gomti River at Lucknow city. Sequential extraction technique was used to identify the distribution of trace elements binding in different fractions; i.e., exchangeable, carbonate, Fe and Mn oxide, organic matter and residual. Heavy metal concentrations were least at upstream and significantly higher in mid and downstream. Fractionation indicated that dominant metals were bound in residual fraction to the bed sediments except for Cd and Pb, which were bound in an equivalent fraction. Geo-accumulation index factor reveals that the enrichment of heavy metals in the bio-available fraction is contributed anthropogenically. Hierarchical cluster analysis also shows the metal pollution load in the river. Risk assessment code of Cd and Ni showed very high risk (ranged from 54.41 to 85.56 and 20.57 to 44.92 respectively) followed by Pb (high risk), Zn, Co (medium risk), Cr, Mn, Cu, Fe (low risk) in Gomti River water. Further, concentrations of Cd and Pb at mid Lucknow were 31 and 75%, high enough to pose a substantial risk to the environment.

Relationships between microbial activity, enzyme activities and metal(loid) form in Ni[sbnd]Cu tailings area

Here we combined microcalorimetry, enzyme activity measurements, and characterization of metal form in order to evaluate the effect of metal(loid)s on the activity of microbial community inhabiting tailings area with high toxic metal(loid)s concentration. Chromium (Cr), nickel (Ni), copper (Cu) and manganese (Mn) were the main pollutants. The exchangeable fractions (bioavailability) of Cu, Ni and Mn were higher in the tailings sample (Site Z), indicating a higher environmental risk. The total heat Qtotal (17,726.87 J/g), peak power Ppeak (541.42 μW/g) and growth rate constant k (0.11 h−1) of Site Z were higher than that of the polluted soil around tailings (Site Y). Such observation may be explained by physiological changes within the microbial community in response to high levels of heavy metal stress, thereby increasing respiration and improving microbial activity. In contrast, enzyme activities and enzyme activities index (GmeA) of Site Z were lower than the Site Y, which is strongly influenced by changes on physical-chemical properties (TN and TOC) and the presence of Cr, Mn, and Ni. Correlation coefficient and principal component analysis (PCA) indicate that GmeA is significantly correlated (p < 0.05 or p < 0.01) with environmental factors (EC, TOC and TN), Mn and Ni concentration, Ni bioavailability, and peak time (Tpeak). Therefore, GmeA represents a potential biological indicator for reporting the pollution degree in tailings area. Our results provide a theoretical basis for the prevention and control of pollution in non-ferrous metal(loid) tailings area.

Reutilization of manganese enriched biochar derived from Phytolacca acinosa Roxb. residue after phytoremediation for lead and tetracycline removal

This study aimed to evaluate the chemical form variation of Mn in Phytolacca acinosa Roxb. residue under different pyrolysis temperatures and its contribution to decontamination efficacy of lead (Pb(II)) and tetracycline (TC). The results illuminated that pyrolysis temperature is a crucial factor of fraction and bioavailability of Mn and other heavy metals in the resultant biochar and pyrolysis temperature under 450 °C may be most suitable for reutilization without potential risk. The Mn-enriched phytolaccaceae biochar (PSB450) exhibited more preferential sorption toward Pb(II) (279.33 mg/g) and TC (47.51 mg/g) than pristine phytolaccaceae biochar in the single system, mainly due to the formation of MnOx and Mn minerals via pyrolysis. Binary adsorption showed that Pb(II) would serve as a bridge between PSB450 and TC by complexation within a limited concentration range, thus facilitating their joint decontamination. This study provided an efficient alternative approach for reutilization of Mn-contaminated biomass.

Early differentiation of magmatic iron meteorite parent bodies from Mn–Cr chronometry

Magmatic iron meteorite groups such as IIAB, IIIAB and IVA, represent the largest sampling of extraterrestrial core material from the earliest accreted distinct planetary bodies in the solar system. Chromium isotope compositions of chromite/daubreelite from seven samples, translated into 53Cr/52Cr model ages, provide robust time information on planetary core formation. These ages range within 1.5 Ma after formation of calcium-aluminium-rich inclusions (CAIs) and define the time of metal core formation in the respective parent bodies, assuming metal-silicate separation was an instantaneous event that induced strong chemical fractionation of Mn from the more siderophile Cr. The early core formation ages support accretion and differentiation of the magmatic iron meteorite parent bodies to have occurred prior to the chondrule formation interval. The calibration of Mn-Cr ages with established Hf-W ages of samples from the same magmatic iron meteorite groups constrains the initial E53Cr of the solar system to -0.30, and thus lower than previously estimated.

Determination of Multi Elements in Tobacco Plant of Northeast India by Neutron Activation Analysis and Atomic Absorption Spectrometry.

Even when cultivated in uncontaminated soils, tobacco plant has higher propensity to extract and accumulate trace elements. The concentrations (mass fractions) of essential elements (K, Ca, Mg, Na, Cl, Mn, Fe, Cu, and Zn) and 28 non-essential elements in tobacco plant (leaves, stem, and root) of Northeast India and their respective soils were quantitatively measured. Hg mass fraction in all samples analyzed were found to be < 10mg/kg. The heavy element mass fractions of tobacco are weakly correlated to different soil parameters. The bioconcentration factor values indicated that Cd (7) is selectively absorbed and translocated in the tobacco leaves compared to Zn (1.7), Cu (1.5), Ni (0.12), and Pb (0.1). Under acidic soil conditions, tobacco plant efficiently absorbed and translocated Cl- ion with great ease, whereas it may be a very low accumulator of rare-earth elements. The mass fractions of Mn, Cu, Sb, Cs, Rb, and Pb are very similar to the "reference plant," whereas significantly higher mass fractions of Al, Sc, Ti, Zr, Hf, Ta, Th, and U are present in the roots of tobacco plant relative to the "reference plant." Principal component analysis has revealed that Northeast Indian tobacco can be clearly differentiated from other varieties of tobaccos used in different countries because of their element profiles.

Distribution of Geochemical Species of P, Fe and Mn in Surface Sediments in the Eutrophic Estuary, Northern Taiwan

The Danshuei River Estuary (DRE) in northern Taiwan is a seriously eutrophic estuary due to the domestic effluent discharge. Surface sediment samples were collected from the DRE to study the concentrations and spatial distributions of different fractions of phosphorus through the five-step sequential extraction method which chemically divides the sedimentary P into five fractions: PSORB, PCDB, PCFA, PDET, and PORG. The Fe and Mn contents in the extracted solution were also determined. The total organic carbon (TOC) and grain size in sediment samples were analyzed as well. The sedimentary total P (TP) concentrations ranged within 537–1310 mg/kg and mostly exceeded 800 mg/kg, suggesting that the DRE sediments were moderately polluted by phosphorus. The PCDB was the dominant fraction of P, averagely contributing 58% of TP, followed by PDET 31%. The contributions of the PSORB and PCFA fractions to the TP were relatively minor. Two fractions, FeCDB and FeORG, of sedimentary Fe equally shared approximately 70% of total Fe, followed by FeDET with 22%. The contribution of different fractions of sedimentary Mn followed the sequence: MnCDB (36%) &gt; MnCFA (29%) &gt; MnORG (14.7%) &gt; MnDET (14.5%) &gt; MnSORB (5.3%). The sedimentary P, Fe, and Mn within the DRE are easily mobilized because they were mainly present in the reducible fraction. The concentrations of sedimentary TP positively correlated with the TOC contents and inversely negatively correlated with grain size, suggesting that the TOC and grain size play the crucial roles in influencing the distribution of sedimentary P within the DRE. Finally, the Fe(III) (hydro)oxides seems to play an important carriers to adsorb dissolved P because PCDB positively correlated with FeCDB.

Highly Conductive Mn-Co Spinel Powder Prepared by Cu-Doping Used for Interconnect Protection of SOFC

Mn-Co Spinel is considered as one of the most promising materials for the interconnect protection of solid oxide fuel cells; however, its conductivity is too low to maintain a high cell performance as compared with cathode materials. Element doping is an effective method to improve the spinel conductivity. In this work, we proposed doping Mn-Co spinel powder with Cu via a solid phase reaction. CuδMn1.5−xCo1.5−yO4 with δ = 0.1, 0.2, 0.3, and x + y = δ was obtained. X-ray diffraction (XRD) and thermogravimetry-differential scanning calorimetry (TG-DSC) were used to evaluate the Cu-doping effect. After sintering at 1000 °C for 12 h, the yield exhibited the best crystallinity, density, and element distribution, with a phase composition of MnCo2O4/CuxMn3−xO4 (x = 1, 1.2, 1.4 or 1.5). X-ray photoelectron spectroscopy (XPS) was used to semi-quantitatively characterize the content changes in element valence states. The areal fraction of Mn2+ and Co3+ was found to decrease when the sintering duration increased, which was attributed to the decomposition of the MnCo2O4 phase. Finally, coatings were prepared by atmospheric plasma spraying with doped spinel powders and the raw powder Mn1.5Co1.5O4. It was found that Cu doping can effectively increase the conductivity of Mn-Co spinel coatings from 23 S/cm to 51 S/cm. Although the dopant Cu was found to be enriched on the surface of the coatings after the conductivity measurement, which restrained the doping effect, Cu doping remains a convenient method to significantly promote the conductivity of spinel coatings for SOFC applications.

Catalytic oxidation of Hg0 over Mn-doped CeO2-ZrO2 solid solution and MnOx/CeO2-ZrO2 supported catalysts: Characterization, catalytic activity and SO2 resistance

MnOx-based oxides have been recognized as efficient catalysts for elemental mercury (Hg0) oxidation at low temperature from flue gas. CeO2 or CeO2-ZrO2 solid solution can enhance the catalytic activity of MnOx, so combining manganese and CeO2 or CeO2-ZrO2 is a promising way to obtain more highly effective catalysts. Two kinds of combination modes were considered: one was MnOx loaded on the CeO2-ZrO2 to form a supported catalyst (MnOx/CeO2-ZrO2, Mn/CZ), and the other was Mn-doped into the CeO2-ZrO2 solid solution to generate a new MnOx-CeO2-ZrO2 (CZM) solid solution catalyst. However, it was not yet known which catalyst prepared by the two combination modes has the better Hg0 oxidation performance. To compare their catalytic activities, the two kinds of catalysts with varying Mn mass content were synthesized by the similar method, and the Hg0 catalytic oxidation performances and the effects of SO2 were tested under the same conditions. The catalysts were well characterized by ICP, XRD, Raman, XPS, SEM and N2 adsorption test, and the results suggested that with the same mass fraction of Mn in the catalyst, the BET surface area and the active species concentration (Mn4+ and Oad) of the new MnOx-CeO2-ZrO2 solid solution catalyst were higher than those of the supported catalyst. Activity tests results showed that for the MnOx loaded samples, 18%Mn/CZ exhibited the best activity (64.58%)., while for the Mn doped solid solution, Ce0.525Zr0.175Mn0.3O2 exhibited the highest Hg removal efficiency (89.53%). The mass contents of Mn in 18%Mn/CZ and Ce0.525Zr0.175Mn0.3O2 were similar. The results suggested that the new solid solution MnOx-CeO2-ZrO2 was more promising for Hg0 oxidation. For both types of the catalysts, Mn4+ and surface active oxygen (Oad) were the active species in the Hg0 oxidation reactions. SO2 significantly inhibited the activity of MnOx/CeO2-ZrO2, because SO2 prevented the reaction between Hg0 and the active species (Mn4+ and Oad). The MnOx-CeO2-ZrO2 solid solution exhibited better SO2 resistance, because the SO2 just inhibited the reaction between Hg0 and Oad.

Determination of the Elements Composition in Sempervivum tectorum L. from Bulgaria

Sempervivumtectorum L. is an evergreen plant with fleshy blue-green leaves forming a rosette. The plant is well-known in alternative medicine and has been used for thousands of years. Traditionally for medicinal purposes, the plant is used as a juice obtained by simple squeezing of fresh plants leaves. The total content of Ca, K, Na, Mg, Mn, Fe, Zn, Cu, Co, Al, V, Cr, Ni, Mo, Ba, Pb, Cd, Hg, As, and Tl in plant leaves of Sempervivum tectorum L. sampled from different habitats in Bulgaria was determined after microwave digestion and measurements by inductively coupled plasma mass spectrometry and flame atomic absorption spectrometry. Furthermore, the bioavailable fraction of essential elements Ca, Mg, Fe, Mn, and Zn was defined after extraction with a hydrochloric acid solution, mimicking stomach juice. The total element content showed a high bioavailability of essential human health elements, such as Ca, Mg, Fe, and Zn. Additionally, essential and toxic elements concentrations were quantified in a fresh juice, obtained by squeezing from plant leaves, as most frequently used in folk medicine. The results obtained demonstrated high concentrations of K, Mg, Ca, Zn, and Cu, which could be accepted as an explanation and a further confirmation of the anti-inflammatory action of this plant.

Role of Seasonality and Fire in Regulating the Enzymatic Activities in Soils Covered by Different Vegetation in a Mediterranean Area

As they quickly respond to environmental conditions, soil enzymes, involved in nutrient cycles, are considered good indicators of soil quality. The Mediterranean area is a peculiar environment for climatic conditions and for fire frequency. Therefore, the research aimed to evaluate the role of seasonality and fire on enzymatic activities (i.e., hydrolase, dehydrogenase, and β-glucosidase) in soils covered by herbs, black locust, pine, and holm oak. In addition, the main soil abiotic properties that drive the enzymatic activities were also investigated. In order to achieve the aims, surface soils were collected in unburnt and burnt areas and characterized for water and organic matter contents, pH, concentrations of C and N, and available fractions of Al, Ca, Cu, Fe, Mg, Mn, Na, and Pb. The results highlighted that the soil enzymatic activities were mainly affected by seasonality more than by fire; in unburnt soils, their main drivers were nutrient availabilities, whereas, in burnt soils they were pH, water and organic matter contents, C and N concentrations, and both nutrient and metal availabilities. Finally, holm oak, as compared with herbs, pine, and black locust, conferred higher stability to soils that were affected by seasonality and fire.

Manganese fractionation analysis in specific soil and sediment samples

Manganese has been determined in soil- and sediment samples taken from selected regions with high manganese concentrations anthropogenic and/or geogenic. The total content of manganese in chosen sediment- and soil samples has been determined applying FAAS after microwave digestion and the manganese fractions after sequential extraction procedures using galvanostatic stripping chronopotentiometry. The highest content of manganese has been determined in sediment from Hôrka (6243.6 ± 56.2 mg kg-1), while the lowest value has been obtained in the sediment from Kráľová (278.6 ± 3.9 mg kg-1). Using a modified Tessier’s procedure it was found, that manganese in sediments from Kráľová is associated mainly with the carbonate fraction (&gt;50%), while in sediments from Lozorno and Hôrka it is associated primarily with the Mn and Fe oxide fraction (80% and 42% respectively).

Simultaneous Quantification and Speciation of Trace Metals in Paired Serum and CSF Samples by Size Exclusion Chromatography-Inductively Coupled Plasma-Dynamic Reaction Cell-Mass Spectrometry (SEC-DRC-ICP-MS).

Background: Transition metals play a crucial role in brain metabolism: since they exist in different oxidation states they are involved in ROS generation, but they are also co-factors of enzymes in cellular energy metabolism or oxidative defense. Methods: Paired serum and cerebrospinal fluid (CSF) samples were analyzed for iron, zinc, copper and manganese as well as for speciation using SEC-ICP-DRC-MS. Brain extracts from Mn-exposed rats were additionally analyzed with SEC-ICP-DRC-MS. Results: The concentration patterns of transition metal size fractions were correlated between serum and CSF: Total element concentrations were significantly lower in CSF. Fe-ferritin was decreased in CSF whereas a LMW Fe fraction was relatively increased. The 400–600 kDa Zn fraction and the Cu-ceruloplasmin fraction were decreased in CSF, by contrast the 40–80 kDa fraction, containing Cu- and Zn-albumin, relatively increased. For manganese, the α-2-macroglobulin fraction showed significantly lower concentration in CSF, whereas the citrate Mn fraction was enriched. Results from the rat brain extracts supported the findings from human paired serum and CSF samples. Conclusions: Transition metals are strictly controlled at neural barriers (NB) of neurologic healthy patients. High molecular weight species are down-concentrated along NB, however, the Mn-citrate fraction seems to be less controlled, which may be problematic under environmental load.

Fractionation of heavy metals in soils cultivated with tobacco in Pinar del Río, Cuba

Knowledge of the presence of heavy metals in soils of agricultural areas is important to prevent their accumulation in cultivated plants. The objective of the present investigation was to evaluate the total concentrations and fractions of heavy metals Cd, Pb, Zn, Fe, Mn, Ni, Cu, Cr and Co in the tobacco-growing area of Pinar del Río, Cuba and their relationship with the physicochemical properties of soil. For the study, 59 samples of three types of soils were collected at 20 cm depth. The pseudo-total concentrations of metals in the soils are low and lower than the prevention values registered for Cuban soils. In general, the heavy metals studied present a high affinity for the most stable fractions of the soil, which means a low risk of transfer to the tobacco crop or accumulation in groundwater. The pseudo-total concentrations of heavy metals were low, below the alert values established for soils in the region. The heavy metals studied were mainly associated with the residual fraction, the second fraction with the highest association with metals was that linked to manganese and iron oxides. The principal component analysis showed that their main source is pedogenetic and that these elements are closely related to cation exchange capacity and calcium content.

Reforestation Impacted Soil Heavy Metal Fractionation and Related Risk Assessment in the Karst Area, Southwest China

Human agricultural activities have resulted in widespread land degradation and soil contamination in the karst areas. However, the effects of reforestation after agricultural abandonment on the mobility risks and contamination of heavy metals have been rarely reported. In the present study, six soil profiles were selected from cropland and abandoned cropland with reforestation in the Puding karst regions of Southwest China. The Community Bureau of Reference (BCR) sequential extraction method was used to evaluate the compositions of different chemical fractions of soil heavy metals, including Fe, Mn, Cr, Zn, Ni, and Cd. The total contents of Cr, Ni, Zn, Cd, and Mn in the croplands were significantly higher than those in the abandoned croplands. For all soils, Cr, Ni, Zn, and Fe were mainly concentrated in the residual fractions (&gt;85%), whereas Mn and Cd were mostly observed in the non-residual fractions (&gt;65%). The non-residual fractions of Cd, Cr, Ni, and Zn in the croplands were higher than those in the abandoned croplands. These results indicated that the content and mobility of soil heavy metals decreased after reforestation. The individual contamination factor (ICF) and risk assessment code (RAC) showed that Cd contributed to considerable contamination of karst soils. The global contamination factor (GCF) and potential ecological risk index (RI) suggested low contamination and ecological risk of the investigated heavy metals in the croplands, moreover they can be further reduced after reforestation.