Μg Mn Research Articles

Advances in making Mn oxide‐coated sands

AbstractManganese (Mn) oxide‐coated sand has been suggested as an amendment for scrubbing metals in water filtration beds and also as a less concentrated medium for uniformly amending soils with Mn oxides in mesocosm scale studies. Earlier work at the lab bench scale, using potassium permanganate (KMnO4) solutions that were reduced with sodium (Na) lactate, resulted in sands coated with about 0.13% Mn. The goal of this project was to increase the amount of Mn oxide that could be coated on sand to make it a more useful amendment and also to attempt to scale up the procedure to produce larger (kg) quantities of coated sand. Titration experiments examined the effects of (1) varying the molar ratio of Na lactate to KMnO4, (2) varying the rate at which the titration was accomplished, and (3) varying the concentration (molarity) of the original KMnO4 solution. The results of this work led to an optimal approach utilizing 0.32 M KMnO4 solution that was titrated to a final lactate:permanganate ratio of ∼1.1 with 10% of the lactate being added every 10 min while the suspension was being stirred. The proportion of sand to an initial solution was also increased 5–20 fold to between 50 and 200 g per 100 mL of solution. Applying this method and using a large 20‐ to 30‐L reaction vessel yields sands coated with up to 0.7% Mn in batches 5–10 kg is size, which could be useful as an amendment in mesocosm scale studies, or as a component of treatment filter beds. The examination of various size fractions of the coated sands demonstrated that more Mn was coated on finer sand fractions, which appears to be a function of the particle surface area available for the coating of Mn oxides, and at a rate of 0.3–0.5 µg Mn mm−2 of the particle surface.

Polarity Dependence of Transport of Pharmaceuticals and Personal Care Products Through Birnessite-Coated Porous Media

Pharmaceuticals and personal care products (PPCPs) have drawn increasing concern of environmental health as they are continuously released into the environment. This study examined the effects of birnessite (δ-MnO2) on the transport and retention of five PPCPs in porous media under steady saturated flow conditions. Considering that natural birnessite occurs as discrete particles and small nodules, birnessite-coated sand was used to mimic the natural regime of birnessite in the environment. Batch isotherm experiments were conducted using uncoated and birnessite-coated sand; results showed that the difference in the affinity of the five PPCPs was correlated to their polarity characteristics. Column experiments were conducted by mixing 0, 10, and 20% birnessite-coated sands with the uncoated sands. These three percentages are equivalent to three contents of manganese (Mn) in the experimental columns (0, 55, and 109 μg Mn g−1 sand). Results suggested that polar compounds (such as bisphenol-A, tetracycline, and ciprofloxacin) had a higher affinity to birnessite-coated sands than the weak polar compounds (such as ibuprofen and carbamazepine) because the polarity was favorable to electrostatic attraction and oxidative reaction. Overall, birnessite decreased the mobility of polar PPCPs but exerted no significant effect on the mobility of weak polar PPCPs under continuous flow conditions. The polarity-based correlation extended traditional electrostatic theory while well interpreting the complicated effects of birnessite on the adsorption and transport of PPCPs, especially neutral or non-dissociated compounds like carbamazepine.

Manganese accumulation and tissue-level distribution in Australian Macadamia (Proteaceae) species

Background and aimsAustralian Macadamia species are known for their edible nuts as well as their ability to take up high concentrations of manganese (Mn) into their leaves. However, little is known about the ecophysiology of Mn in species of Macadamia. MethodsThis study investigated (i) Mn accumulation in wild Macadamia using handheld X-ray fluorescence spectroscopy (XRF) of herbarium collections, and (ii) Mn uptake in three out of four known Macadamia species (M. tetraphylla, M. integrifolia and M. ternifolia) in a pot experiment that delivered Mn treatments in both solid (as natural Mn-minerals mixed with quartz sand) and liquid form (as MnSO4 solution added to soil). Tissue samples were analysed for bulk elemental concentrations and for in vivo distribution of Mn and other elements using laboratory μXRF analysis. Key resultsThe results revealed that wild M. ternifolia and M. integrifolia are strong Mn accumulators with up to 9600 μg Mn g−1 and 8500 μg Mn g-1, respectively, followed by M. jansenii (6400 μg Mn g-1) and M. tetraphylla (5100 μg Mn g-1). Under the controlled conditions, high Mn accumulation was demonstrated for M. integrifolia and M. tetraphylla with greater than 7500 μg Mn g−1 in mature leaves in the highest Mn treatment level. Our results further showed that Mn was efficiently translocated from the roots to the shoots with translocation factor >1 in the studied species. The laboratory μXRF analysis revealed that Mn was absent from the vascular bundles and concentrated in the areas between veins. ConclusionsAll the four Macadamia species have high foliar Mn concentrations qualifying them as strong Mn accumulators in nature as determined by handheld XRF analysis of herbarium specimens. Under experimental conditions, M. integrifolia and M. tetraphylla were confirmed to be strong Mn accumulators. Manganese was shown by laboratory μXRF analysis to be concentrated in the inter-veinal areas of the leaf lamina.

In vivo neutron activation assembly design for quantification of trace elements using MCNP

Background: Trace and essential elements both play a crucial role in maintaining normal cellular and organ functions in human, while abnormal exposure to some of them is also potentially related to diseases, e.g. manganism. To study the association between elemental intake and health outcomes, accurate assessment of elemental uptake and storage in the human body is essential. Objective: Technology based on neutron activation analysis can be used for in vivo measurement of the trace elements given that the measurement system guarantees a low detection limit with an acceptable dose. This study aims to design and optimize a customized and portable deuterium–deuterium neutron generator-based irradiation assembly for the NAA of trace elements in vivo, using Monte Carlo simulations. Approach: The irradiation assembly includes a moderator, a fast neutron filter, a reflector, and shielding. The human hand phantoms doped with manganese (Mn) and potassium (K) are used to determine the respective elements’ system sensitivity and detection limit. Main results: The calculated detection limit is 0.16 μg Mn per gram dry bone (ppm) for Mn and 17 ppm for K, with an equivalent dose of 36 mSv to the hand for 10 min irradiation. Significance: This more sensitive in vivo neutron activation analysis system will detect trace elements in vivo.

Particulate trace metal fluxes in the center of an oceanic desert: Northeast Atlantic subtropical gyre

For this study particle flux material collected over 13 years period starting in February 2002 until summer 2015 with the long-term mooring Kiel 276 (33°N, 22°W) in the subtropical Northeast Atlantic was analyzed. Our focus was set on the elemental composition and trace element fluxes which we analyzed with the help of ICP-OES and ICP-MS. The particle flux has a mean of 60 mg m −2 d −1 (range: 1–365 mg m −2 d −1 ) with peak fluxes during February and April shortly after the winter bloom. Especially in 2004 high fluxes occurred through the year when the Azores Front was located south of the mooring. In this year enhanced nutrient supply and high dust concentration in the atmosphere were measured. The analyzed trace elements of Cd, Co, Cr, Cu, Ni, V, Zn, Zr, and Mn have mean fluxes of 43.4 μg Cd m −2 d −1 , 205.7 μg Co m −2 d −1 , 1.4 μg Cr m −2 d −1 , 3.2 μg Cu m −2 d −1 , 1.6 μg Ni m −2 d −1 , 1.0 μg V m −2 d −1 , 5.1 μg Zn m −2 d −1 , 1.3 μg Zr m −2 d −1 , and 7.8 μg Mn m −2 d −1 . Biogenic trace elements (Cd, Zn, Ni) show maximum fluxes in winter and spring while no seasonality was present for refractory (Zr) and redox-sensitive elements (V, Mn, Co). Fe, Ti, Co, Mn, V, Mn, and Zr are only little enriched towards the upper continental crust (EF < 2) as these elements originate from a lithogenic source and are little prone to dissolution or scavenging while Cd, Cu, Cr, Ni, and Zn are more enriched with EF of 3.0, 9.6, 2.4, 6.2, and 5.0, respectively. • 13 years long particle flux time series from the subtropical NE Atlantic • Atmospheric pathways and Azores Front modulate particle and trace elemental fluxes. • Deep ocean particulate trace elemental fluxes depend on the biogenic matter cycle.

Ammonium‐driven nitrification plays a key role in increasing Mn availability in calcareous soils

Abstract Background: Manganese deficiency often becomes a yield limiting factor, particularly on calcareous soils, even though the total soil manganese content is usually sufficient. Although it is known that acidifying N fertilizers can improve Mn availability, the reason of this effect is still unknown. Aim: Our aim was to investigate the effect of stabilized ammonium fertilizers as a tool to distinguish between physiological‐ and nitrification‐induced acidification. Method: Two pot experiments with Triticum aestivum L. and one soil incubation experiment using different nitrogen forms (CN = calcium nitrate, AN = ammonium nitrate, AS = ammonium sulfate, ATS = ammonium thiosulfate) with and without addition of nitrification inhibitors (DCD, Nitrapyrin, Piadin, DMPP) were conducted to examine the effect on Mn availability in the soil and Mn uptake by the plants at different development stages (EC 31 und 39). Results: With increasing fertilizer content a higher Mn concentration was detected: CN: 32 µg Mn g−1 DM, AN: 39 µg Mn g−1 DW, AS: 55 µg Mn g−1 DM, ATS: 109 µg Mn g−1 DM. The addition of a nitrification inhibitor resulted in a significantly lower rhizosphere pH compared to the non‐stabilized fertilizer. Surprisingly, the use of different nitrification inhibitors led to unchanged (CN, AN) or lower Mn concentrations of wheat. Especially in the treatments (AS and ATS), this negative effect was very evident (AS+DCD: 42 µg Mn g−1 DM; ATS+DCD: 55 µg Mn g−1 DM). Conclusions: Mn availability was enhanced by ongoing nitrification process rather than physiological acidification. Compared to other N forms, ammonium thiosulfate led to the highest Mn availability in bulk soil.

The net iron, manganese, copper, and zinc requirements for maintenance and growth of Dorper × Hu ewe lambs

A comparative slaughter trial was conducted to estimate the net trace element requirements of Dorper × Hu ewe lambs. Thirty-five ewe lambs with an initial body weight of 33.52 ± 0.56 kg, were used. Seven ewe lambs were randomly chosen and slaughtered at 34.85 ± 0.37 kg body weight as the baseline group for measuring initial body composition. Another seven lambs were also randomly chosen and offered a pelleted mixed diet for ad libitum intake and slaughtered at 41.47 ± 0.53 kg body weight. The remaining ewe lambs (n = 21) were allocated randomly on d 0–3 treatment intake levels within seven slaughter groups. A slaughter group contained 1 lamb from each treatment, and lambs were slaughtered when the ad libitum treatment lamb reached approximately 50 kg body weight. The daily net trace element requirements for maintenance were 310.4 µg Fe, 4.4 µg Mn, 35.7 µg Cu, and 110.3μg Zn/kg of empty body weight. The net trace element requirements for growth decreased from 41.02 to 37.05 mg Fe, 0.52–0.49 mg Mn, and 3.39–3.10 mg Cu and increased from 34.21 to 35.80 mg Zn/kg empty body weight gain (EBWG) from 35 to 50 kg body weight. The net Fe, Mn, Cu and Zn requirements of Dorper × Hu ewe lambs for maintenance were greater than the recommendations of the NRC, and the net Fe and Mn requirements of Dorper × Hu ewe lambs for growth were lower than the recommendations of the NRC, except that the net Cu and Zn growth requirements were greater than the recommendations of the NRC.

Rates and processes affecting As speciation and mobility in lake sediments during aging

Sediments from an arsenic (As) contaminated groundwater vent site were used to investigate As(III) binding, transformation and redistribution in native and iron oxide amended lake sediments using aging spiked batch reactions and a sequential extraction procedure that maintains As(V) and As(III) speciation. In the native sediments, fractionation analysis revealed that 10% of the spiked As(III) remained intact after a 32-day aging experiment and was predominantly adsorbed to the strongly sorbed (NH4H2PO4 extractable) and amorphous Fe oxide bound (H3PO4 extractable) fractions. Kinetic modelling of the experimental results allowed identifying the dominant reaction path for depletion of dissolved As(III) to As(III) absorbed on to the solid phase, followed by oxidation in the solid phase. Arsenite was initially adsorbed primarily to the easily exchangeable fraction ((NH4)2SO4 extractable), then rapidly transformed into As(V) and redistributed to the strongly sorbed and amorphous Fe oxide bound fractions. Oxidation of As(III) in recalcitrant fractions was less efficient. The iron oxide amendments illustrated the controls that iron oxides can have on As(III) binding and transformation rates. In goethite amended samples As(III) oxidation was faster and primarily occurred in the strongly sorbed and amorphous Fe oxide bound fractions. In these samples, 19.3μg Mn was redistributed (compared to the native sediment) from the easily exchangeable and crystalline Fe oxide bound fractions to the strongly sorbed and amorphous Fe oxide bound fractions, indicating that goethite may act as a catalyst for Mn(II) oxidation, thereby producing sorbed Mn(III/IV), which then appears to be involved in rapidly oxidizing As(III).

Thinning effects on foliar elements in eastern hemlock: implications for managing the spread of the hemlock woolly adelgid

Stand thinning is being tested as a means to limit the impacts of the invasive hemlock woolly adelgid (HWA; Adelges tsugae Annand) on eastern hemlock (Tsuga canadensis (L.) Carriere). The efficacy of this strategy may be reduced if thinning increases hemlock foliar nutrients because HWA densities are correlated with foliar concentrations of N, P, K, Ca, and Mn. We determined foliar N, P, K, Ca, and Mn concentrations in 1-year-old and all other (older) needles prior to and for 4 years after thinning in northwestern Pennsylvania stands of eastern hemlock without HWA. Average foliar concentrations in 1-year-old needles were 1.30–1.80 g N·100 g−1, 1300–1700 mg P·kg−1, 4200–6300 mg K·kg−1, 2500–5200 mg Ca·kg−1, and 2393 μg Mn·g−1. N, P, and K decreased, Ca increased, and Mn first increased and then stabilized. Thinning by itself did not affect the tested foliar nutrients. The interaction between treatment and year was significant and evident in temporal trajectories of foliar N and K. However, the differences between thinned and unthinned plots within years averaged only 0.03 g N·100 g−1 and 340 mg K·kg−1. We concluded that even though thinning changed the temporal trajectories of foliar N and K, the nutritional shifts were minimal, brief, and unlikely to affect the efficacy of thinning in limiting the impacts of HWA.

Time and temperature dependency of carbon dioxide triggered metal(loid) mobilization in soil

Assessing the influence of CO2 on soil and aquifer geochemistry is a task of increasing interest when considering risk assessment for geologic carbon sequestration. Leakage and CO2 ascent can lead to soil acidification and mobilization of potentially toxic metals and metalloids due to desorption or dissolution reactions. We studied the CO2 influence on an Fe(III) (oxyhydr)oxide rich, gleyic Fluvisol sampled in close vicinity to a Czech mofette site and compared the short-term CO2 influence in laboratory experiments with observations on long-term influence at the natural site. Six week batch experiments with/without CO2 gas flow at 3 different temperatures and monitoring of liquid phase metal(loid) concentrations revealed two main short-term mobilization processes. Within 1 h to 1 d after CO2 addition, mobilization of weakly adsorbed metal cations occurred due to surface protonation, most pronounced for Mn (2.5–3.3 fold concentration increase, mobilization rates up to 278 ± 18 μg Mn kgsoil−1 d−1) and strongest at low temperatures. However, total metal(loid) mobilization by abiotic desorption was low. After 1–3 d significant Fe mobilization due to microbially-triggered Fe(III) (oxyhydr)oxide dissolution began and continued throughout the experiment (up to 111 ± 24 fold increase or up to 1.9 ± 0.6 mg Fe kgsoil−1 d−1). Rates increased at higher temperature and with a higher content of organic matter. The Fe(III) mineral dissolution was coupled to co-release of incorporated metal(loid)s, shown for As (up to 16 ± 7 fold, 11 ± 8 μg As kgsoil−1 d−1). At high organic matter content, re-immobilization due to resorption reactions could be observed for Cu. The already low pH (4.5–5.0) did not change significantly during Fe(III) reduction due to buffering from sorption and dissolution reactions, but a drop in redox potential (from > +500 mV to minimum +340 ± 20 mV) occurred due to oxygen depletion. We conclude that microbial processes following CO2 induction into a soil can contribute significantly to metal(loid) mobilization, especially at optimal microbial growth conditions (moderate temperature, high organic carbon content) and should be considered for carbon sequestration monitoring and risk assessment.

English

Salinity reduces the uptake of manganese (Mn) and induces its deficiency, which adversely affects photosynthesis-related photosystem-II activity, hence growth is hampered. The objective of the study was to investigate the effects of Mn application on the photosystem-II activity on the isolated thylakoid membranes of the rice. A hydroponic study was carried out in the glasshouse of National Agriculture Research Centre, Islamabad, Pakistan on two rice varieties, Pakhal and KS-282, using three replicates. Three salt concentrations, namely 0, 25, 50 mM NaCl were used. Manganese sulphate was used for foliar and root application with four concentrations (0, 2, 4, 8 µg Mn mL -1 ). Salinity decreased the concentration of Mn, while the application of Mn, increased the contents of Mn in shoot and root. Increased salt concentration caused a decrease in the chlorophyll contents while Mn application increased chlorophyll contents across all the salinity levels, with maximum increase at 2 µg Mn mL -1 . Photosystem-II activity was inhibited by increasing salt concentration, while Mn treatment rescued this inhibitory affect, with maximum photosystem-II activity recovery at 2 µg Mn mL -1 level in both varieties. Quite high concentration of Mn was observed in root application methods as compared to foliar but it failed to recover salinity impact on photosystem-II and photosynthesis. Applying Mn as foliar increased tolerance to salinity at 50 mM NaCl level while root application was found better at 25 mM NaCl concentration in culture solution. © 2016 Friends Science Publishers

Assessment of toxic metals in groundwater and saliva in an arsenic affected area of West Bengal, India: A pilot scale study

Communities in many parts of the world are unintentionally exposed to arsenic (As) and other toxic metals through ingestion of local drinking water and foods. The concentrations of individual toxic metals often exceed their guidelines in drinking water but the health risks associated with such multiple-metal exposures have yet to receive much attention. This study examines the co-occurrence of toxic metals in groundwater samples collected from As-rich areas of Nadia district, West Bengal, India. Arsenic in groundwater (range: 12–1064µgL−1; mean ± S.D: 329±294µgL−1) was the most important contaminant with concentrations well above the WHO guideline of 10µgL−1. Another important toxic metal in the study area was manganese (Mn) with average concentration of 202±153µgL−1, range of 18–604µgL−1. The average concentrations (µgL−1) of other elements in groundwater were: Cr (5.6±5.9), Mo (3.5±2.1), Ni (8.3±8.7), Pb (2.9±1.3), Ba (119±43), Zn (56±40), Se (0.60±0.33), U (0.50±0.74). Saliva collected from the male participants of the area had mean concentrations of 6.3±7.0µg As L−1 (0.70–29µgL−1), 5.4±5.5µg Mn L−1 (0.69–22µgL−1), 2.6±3.1µg Ni L−1 (0.15–13µgL−1), 0.78±1.0µg Cr L−1 (<DL–5.9µgL−1), 0.94±0.90µg Pb L−1 (<DL–4.2µgL−1), 0.56±0.37µg Se L−1 (0.11–1.5µgL−1) and 194±54µg Zn L−1 (112–369µgL−1). The high concentrations of salivary As and Mn are believed to be indicative of intake from the groundwater. The clustering of salivary As and Mn in principal component analysis further indicated influence of the common exposure source. Zinc and selenium comprised a separate component presumably reflecting the local deficiencies in intakes of these essential elements from drinking water and foodstuff. Thus the study reveals that the concentration of other metals beside As must be monitored in drinking water before implementation of any policies to provide safe water to the affected communities.

Toxicity of naturally-contaminated manganese soil to selected crops.

The impact of manganese excess using naturally contaminated soil (Mn-soil, pseudototal Mn 6494 vs 675 μg g(-1) DW in control soil) in the shoots of four crops was studied. Mn content decreased in the order Brassica napus > Hordeum vulgare > Zea mays > Triticum aestivum. Growth was strongly depressed just in Brassica (containing 13696 μg Mn g(-1) DW). Some essential metals (Zn, Fe) increased in Mn-cultured Brassica and Zea, while macronutrients (K, Ca, Mg) decreased in almost all species. Toxic metals (Ni and Cd) were rather elevated in Mn-soil. Microscopy of ROS, NO, lipid peroxidation, and thiols revealed stimulation in all Mn-cultured crops, but changes were less visible in Triticum, a species with low shoot Mn (2363 μg g(-1) DW). Antioxidative enzyme activities were typically enhanced in Mn-cultured plants. Soluble phenols increased in Brassica only while proteins rather decreased in response to Mn excess. Inorganic anions (chloride, sulfate, and phosphate) were less accumulated in almost all Mn-cultured crops, while the nitrate level rather increased. Organic anions (malate, citrate, oxalate, acetate, and formate) decreased or remained unaffected in response to Mn-soil culture in Brassica, Hordeum, and Triticum but not in Zea. However, the role of organic acids in Mn uptake in these species is not assumed. Because control and Mn-soil differed in pH (6.5 and 3.7), we further studied its impact on Mn uptake in solution culture (using Mn concentration ∼5 mM deducted from water-soluble fraction of Mn-soil). Shoot Mn contents in Mn-treated plants were similar to those observed in soil culture (high in Brassica and low in Triticum) and pH had negligible impact. Fluorescence indicator of "general ROS" revealed no extensive or pH-dependent impact either in control or Mn-cultured roots. Observed toxicity of Mn excess to common crops urges for selection of cultivars with higher tolerance.

Nutritional and Mineral Variability in 52 Accessions of Common Bean Varieties (&amp;lt;i&amp;gt;Phaseolus vulgaris&amp;lt;/i&amp;gt; L.) from Madeira Island

The Phaseolus vulgaris L. is one of the traditional and most important leguminous crops in the Island of Madeira. The island’s bioclimatic tiers, agro-ecological environment and traditional farming practices had a great influence on the evolution of regional bean landraces. The variability of the nutritional and mineral seeds composition of 59 accessions of the Madeiran landraces, standard and commercial varieties was evaluated. Wide ranges of variability in biochemical parameters were reported among the Madeiran landraces, being the best sources of protein and mineral nutrition, according to the statistical results and literature comparative evaluation. Specifically, the content (g per 100 g DW) of ash ranged from 3.64-5.67, lipids from 0.57-2.86, protein from 18.55-29.69, starch from 23.40-52.65, soluble sugars from 2.97-6.84, while content of dry matter was from 83.35-93.55. The seeds also contained (per 100 g DW) between 2.55-4.83 g N, 0.30-7.50 g P, 1.30-2.49 g K, 0.10-0.18 g Mg, 4.10-10.00 mg Fe, 50.0-1.40 mg Cu, 2.20-5.00 mg Zn, 0.90-3.80 μg Mn and 0.20-2.40 μg B. This variability implies that the screened germplasm could serve as a source for breeding new varieties with improved biochemical and nutritional traits or could be highly recommended to meet specific dietary requirements. The cultivar Vaginha Grossa (ISOP 713) revealed low carbohydrate content that could be a good food choice for diabetics, while cultivar Vermelho (ISOP 724) bean should be offered as a valuable alternative source of protein and minerals in the local diet.

Boron and manganese fractions in dystrophic lake waters (Wigry National Park, NE Poland)

Abstract Physicochemical studies in four dystrophic lakes (Suchar Wielki, Suchar II, Suchar IV, and Wądołek) were carried out in Wigry National Park, NE Poland. Total manganese concentrations oscillated within the range of 386.6-647.5 μg Mn dm-3, while those of soluble reactive manganese, 112.5-328.2 μg Mn dm-3. Fairly high boron contents were recorded in the studied lakes, which amounted to 0.09-2.20 mg B dm-3. The increase in dissolved reactive manganese (DRMn) and decrease in dissolved boron concentration with the lake depth were observed. Almost half (47%) of the total manganese pool was composed of dissolved reactive soluble fraction (DRMn), then dissolved organic form (DOMn, 41%), whereas the particulate fraction (PMn) made up the smallest share (12%). Microbial decomposition of lake organic matter disappears and requirements of authotrophic plankton for Mn2+ decreases when the water temperature drops, thus the fraction prevails. The following regularity was recorded in all analysed dystrophic lakes: iron concentration decreases along with the depth, hence boron content can also be observed due to precipitated borates to bottom sediments, where they are accumulated.

X-ray fluorescence imaging of the hippocampal formation after manganese exposure

Manganese (Mn) intoxication results in neurological conditions similar, but not identical, to idiopathic Parkinson's disease. While the mechanism(s) by which Mn exposure leads to neurotoxic effects remains unclear, studies by magnetic resonance imaging demonstrate a high Mn accumulation in the hippocampal formation (HPCf) of the brain. Metal quantification using this method is not possible. Using X-ray fluorescence imaging, we measured the distribution of Mn in the HPCf for a rodent model of chronic Mn exposure and quantitatively compared it with distributions of other biologically relevant metals. We found considerable increases in average Mn concentrations in all analyzed areas and we identified the dentate gyrus (DG) and the cornus ammonis 3 (CA3) layer as areas accumulating the highest Mn content (∼1.2 μg Mn per g tissue). The DG is significantly enriched with iron (Fe), while the CA3 layer has high zinc (Zn) content. Additionally, significant spatial correlations were found for Mn-Zn concentrations across the HPCf substructures and for Mn-Fe concentrations in the DG. Combined results support that at least two mechanisms may be responsible for Mn transport and/or storage in the brain, associated with either Fe or Zn. Subcellular resolution images of metal distribution in cells of the CA3 show diffuse Mn distributions consistent with Mn localization in both the cytoplasm and nucleus. Mn was not increased in localized intracellular Fe or copper accumulations. A consistent Mn-Zn correlation both at the tissue (40 μm × 40 μm) and cellular (0.3 μm × 0.3 μm) levels suggests that a Zn transport/storage mechanism in the HPCf is likely associated with Mn accumulation.

Characterization of a portable method for the collection of exhaled breath condensate and subsequent analysis of metal content

Using exhaled breath condensate (EBC) as a biological media for analysis of biomarkers of exposure may facilitate the understanding of inhalation exposures. In this study, we present method validation for the collection of EBC and analysis of metals in EBC. The collection method was designed for use in a small scale longitudinal study with the goal of improving reproducibility while maintaining economic feasibility. We incorporated the use of an Rtube with additional components as an assembly, and trained subjects to breathe into the apparatus. EBC was collected from 8 healthy adult subjects with no known elevated exposures to Mn, Cr, Ni, and Cd repeatedly (10 times) within 7 days and analyzed for these metals via ICP-MS. Method detection limits were obtained by mimicking the process of EBC collection with ultrapure water, and resulted in 46-62% of samples falling in a range less than the method detection limit. EBC metal concentrations were found to be statistically significantly associated (p < 0.05) with room temperature and relative humidity during collection, as well as with the gender of the subject. The geometric mean EBC metal concentrations in our unexposed subjects were 0.57 μg Mn per L, 0.25 μg Cr per L, 0.87 μg Ni per L, and 0.14 μg Cd per L. The overall standard deviation was greater than the mean estimate, and the major source in EBC metals concentrations was due to fluctuations in subjects' measurements over time rather than to the differences between separate subjects. These results suggest that measurement and control of EBC collection and analytical parameters are critical to the interpretation of EBC metals measurements. In particular, rigorous estimation of method detection limits of metals in EBC provides a more thorough evaluation of accuracy.

Lead, Chromium and Manganese Removal by in Vitro Root Cultures of Two Aquatic Macrophytes Species: Typha Latifolia L. and Scirpus Americanus Pers.

The ability of in vitro roots cultures of Typha latifolia and Scirpus americanus to remove metals was studied. Roots were cultivated on Murashige-Skoog medium with 15 μg L−1 Cr III, 60 μg L−1 Pb II or 1.8 mg L−1 Mn II. Adsorbed metal to root surface was removed by washing with 0.042% HNO3. T. latifolia roots were able to uptake 68.8 μg Pb g−1, 22.1 μg Cr g−1 and 1680 μg Mn g−1, while the S. americanus roots removed 148.3 μg Pb g−1, 40.7 μg Cr g−1 and 4037 μg Mn g−1. About 80–90% of Pb and Cr were absorbed in both cultures. On the contrary, the Mn removal was due mainly to an adsorption process (82–86%). In comparison to the T. latifolia cultures, S. americanus cultures were two fold more efficient to remove Pb and Cr, and three fold more efficient to remove Mn. Both plant species capture metals in the following order: Cr >Pb >Mn. This investigation confirms that in vitro roots cultures could be an alternative as a phytoremediation approach for contaminated water with heavy metals.

Spatial Variability of Micronutrients in Rice Grain and Paddy Soil

Consumption of rice is the main source of micronutrients to human in Asia. A paddy field with unknown anthropogenic contamination in Deqing County, Zhejiang Province, China was selected to characterize the spatial variability and distribution of micronutrients in rice grain and soil. A total of 96 paired soil and rice grain samples were collected at harvest. The micronutrients in the soil samples were extracted by diethylenetriamine pentaacetic acid (DTPA). The mean micronutrient concentrations in rice grain were 3.85 μg Cu g −1, 11.6 μg Fe g −1, 39.7 μg Mn g −1, and 26.0 μg Zn g −1. The mean concentrations were 2.54 μg g −1 for DTPA-Cu, 133.5 μg g −1 for DTPA-Fe, 30.6 μg g −1 for DTPA-Mn, and 0.84 μg g −1 for DTPA-Zn. Semivariograms showed that measured micronutrients in rice grain were moderately dependent, with a range distance of about 110 m. The concentrations of the DTPA-extractable micronutrients all displayed strong spatial dependency, with a range distance of about 60 m. There was some resemblance of spatial structure between soil pH and the grain Cu, Fe, Mn, and Zn. By analogy, similar spatial variation was observed between soil organic matter (SOM) and DTPA-extractable micronutrients in the soil. Kriging estimated maps of the attributes showed the spatial distributions of the variables in the field, which is beneficial for better understanding the spatial variation of micronutrients and for potentially refining agricultural management practices at a field scale.

Manganese Hyperaccumulation inPhytolacca americanaL. from the Southeastern United States

Most plants that hyperaccumulate metals are restricted to soils with elevated concentrations of those metals. Recent reports have suggested that some Phytolacca species in China can hyperaccumulate manganese (Mn). Phytolacca americana L. (Pokeweed) is a ubiquitous weed of roadsides and waste areas in its native range in the southeastern United States, and has no known association with high-Mn soils. We investigated whether Mn hyperaccumulation also occurs among such plants. Field-collected samples contained approximately 2000 µg Mn g-1 dry weight, whereas other species from the same site ranged from 50 to 450 µg g-1. Seedlings of P. americana were transplanted to the laboratory and grown in nutrient solutions ranging up to 8 mM Mn. After three weeks, Mn concentration in leaves exceeded 32,000 µg/g or 3.2%. This result suggests that P. americana possesses a latent physiological ability to hyperaccumulate Mn, even if this trait is rarely, if ever, expressed within its native range.