Title: Evaluation of quantitative synchrotron radiation micro-X-ray fluorescence in rice grain
Concentrations of nutrients and contaminants in rice grain affect human health, specifically through the localization and chemical form of elements. Methods to spatially quantify the concentration and speciation of elements are needed to protect human health and characterize elemental homeostasis in plants. Here, an evaluation was carried out using quantitative synchrotron radiation microprobe X-ray fluorescence (SR-µXRF) imaging by comparing average rice grain concentrations of As, Cu, K, Mn, P, S and Zn measured with rice grain concentrations from acid digestion and ICP-MS analysis for 50 grain samples. Better agreement was found between the two methods for high-Zelements. Regression fits between the two methods allowed quantitative concentration maps of the measured elements. These maps revealed that most elements were concentrated in the bran, although S and Zn permeated into the endosperm. Arsenic was highest in the ovular vascular trace (OVT), with concentrations approaching 100 mg kg−1in the OVT of a grain from a rice plant grown in As-contaminated soil. Quantitative SR-µXRF is a useful approach for comparison across multiple studies but requires careful consideration of sample preparation and beamline characteristics.
Hu, Ruifang; Limmer, Matthew A.; Seyfferth, Angelia L.(
, Plant and Soil)
AbstractBackground and aims
Rice is prone to Cd uptake under aerobic soil conditions primarily due to the OsNramp5 Mn transport pathway. Unlike Cd, Mn availability in rice paddies decreases as redox potential increases. We tested whether increasing Mn concentrations in solution would decrease Cd accumulation in rice through competition between Mn and Cd for uptake and/or suppression ofOsNramp5expression.
Methods
Rice was grown to maturity under Mn concentrations that spanned three orders of magnitude (0.30 to 37 μM) that corresponded to free Mn2+activities of 10–7.9to 10–5.0 M while free Cd2+activity was held as constant as achievable (10–10.2to 10–10.4 M). Plant biomass and elemental concentrations were measured in roots and shoots at each stage. Fold changes in the expression ofOsNramp5,OsCd1,OsHMA3,OsCCX2, andOsYSL6genes in vegetative and grain-filling stages of rice plants were determined.
Results
Competition between Mn and Cd for root uptake and accumulation in shoots was observed at the highest concentration of Mn tested.OsNramp5expression was significantly higher in rice plants at the vegetative stage compared to the grain-filling stage, whileOsCd1andOsHMA3showed the opposite. Solution Mn concentrations previously thought to be tolerable by rice grown to the vegetative stage led to Mn toxicity as plants matured.
Conclusions
Mn competes with Cd during uptake into rice withOsNramp5expression unaffected. Different translocation paths may occur for Mn and Cd within the rice plant and over the rice life cycle, withOsCCX2correlated with shoot Cd concentration.
Background and Aims
Rice accounts for around 20% of the calories consumed by humans. Essential nutrients like zinc (Zn) are crucial for rice growth and for populations relying on rice as a staple food. No well-established study method exists. As a result, we a lack a clear picture of the chemical forms of zinc in rice grain. Furthermore, we do not understand the effects of widespread and variable zinc deficiency in soils on the Zn speciation, and to a lesser extent, its concentration, in grain.
Methods
The composition and Zn speciation of Cambodian rice grain is analyzed using synchrotron-based microprobe X-ray fluorescence (µ-XRF) and extended X-ray absorption fine-structure spectroscopy (EXAFS). We developed a method to quantify Zn species in different complexes based on the coordination numbers of Zn to oxygen and sulfur at characteristic bond lengths.
Results
Zn levels in brown rice grain ranged between 15-30 mg kg-1 and were not correlated to Zn availability in soils. 72%-90% of Zn in rice grains is present as Zn-phytate, generally not bioavailable, while smaller quantities of Zn are bound as labile nicotianamine complexes, Zn minerals like ZnCO3¬ or thiols.
Conclusion
Zn speciation in rice grain is affected by Zn deficiency more than previously recognized. A majority of Zn was bound in phytate complexes in rice grain. Zinc phytate complexes were found in higher concentrations and also in higher proportions, in Zn-deficient soils, consistent with increased phytate production under Zn deficiency. Phytates are generally not bioavailable to humans, so low soil Zn fertility may not only impact grain yields, but also decrease the fraction of grain Zn bioavailable to human consumers. The potential impact of abundant Zn-phytate in environments deficient in Zn on human bioavailability and Zn deficiency requires additional research.
Eklöf, Daniel; Fischer, Andreas; Grins, Jekabs; Scherer, Wolfgang; Häussermann, Ulrich(
, Zeitschrift für anorganische und allgemeine Chemie)
The intermetallic compound ZnSb is a (II‐V) narrow gap semiconductor with interesting thermoelectric properties. Electrical resistivity, Hall coefficient, thermopower and thermal conductivity were measured up to 400 K on Ag‐doped samples with concentrations 0.2, 0.5, 1, 2, and 3 at.%, which were consolidated to densities in excess of 99.5 % by spark plasma sintering. The work confirms a huge improvement of the thermoelectric Figure‐of‐merit,ZT, upon Ag doping. The optimum doping level is near 0.5 at.% Ag and results inZTvalues around 1.05 at 390 K. The improvement stems from a largely decreased resistivity, which in turn relates to an increase of the hole charge carrier concentration by two orders of magnitude. It is argued that Ag can replace minute concentrations of Zn (on the order of 0.2 at.%) in the crystal structure which enhances the intrinsic impurity band of ZnSb. Excess Ag was found to segregate in grain boundaries. So the best performing material may be considered as a composite Zn~0.998Ag~0.002Sb/Ag~0.003.
Zepeda, Joseph; Rasmussen, Kaitlin C.; Beers, Timothy C.; Placco, Vinicius M.; Huang, Yang; Depagne, Éric(
, The Astrophysical Journal)
Abstract
We present results from high-resolution (R∼ 40,000) spectroscopic observations of over 200 metal-poor stars, mostly selected from the RAVE survey, using the Southern African Large Telescope. We were able to derive stellar parameters for a total of 108 stars; an additional sample of 50 stars from this same effort was previously reported on by Rasmussen et al. Among our newly reported observations, we identify 84 very metal-poor (VMP; [Fe/H] < −2.0, 53 newly identified) stars and three extremely metal-poor (EMP; [Fe/H] < −3.0, one newly identified) stars. The elemental abundances were measured for carbon, as well as several otherα-elements (Mg, Ca, Sc, and Ti), iron-peak elements (Mn, Co, Ni, and Zn), and neutron-capture elements (Sr, Ba, and Eu). Based on these measurements, the stars are classified by their carbon and neutron-capture abundances into carbon-enhanced metal-poor (CEMP; [C/Fe] > +0.70), CEMP subclasses, and by the level of theirr-process abundances. A total of 17 are classified as CEMP stars. There are 11 CEMP-rstars (eight newly identified), one CEMP-sstar (newly identified), two possible CEMP-istars (one newly identified), and three CEMP-no stars (all newly identified) in this work. We found 11 stars (eight newly identified) that are strongly enhanced inr-process elements (r-II; [Eu/Fe] > +0.70), 38 stars (31 newly identified) that are moderately enhanced inr-process elements (r-I; +0.30 < [Eu/Fe] ≤ + 0.70), and one newly identified limited-rstar.
Marsay, Chris M.; Kadko, David; Landing, William M.; Buck, Clifton S.(
, Global Biogeochemical Cycles)
Abstract
Atmospheric deposition of aerosols transported from the continents is an important source of nutrient and pollutant trace elements (TEs) to the surface ocean. During the U.S. GEOTRACES GP15 Pacific Meridional Transect between Alaska and Tahiti (September–November 2018), aerosol samples were collected over the North Pacific and equatorial Pacific and analyzed for a suite of TEs, including Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, and Pb. Sampling coincided with the annual minimum in dust transport from Asia, providing an opportunity to quantify aerosol TE concentrations and deposition during the low dust season. Nevertheless, peak concentrations of “crustal” TEs measured at ∼40–50°N (∼145 pmol/m3Fe) were associated with transport from northern Asia, with lower concentrations (36 ± 14 pmol/m3Fe) over the equatorial Pacific. Relative to crustal abundances, equatorial Pacific aerosols typically had higher TE enrichment factors than North Pacific aerosols. In contrast, aerosol V was more enriched over the North Pacific, presumably due to greater supply to this region from oil combustion products. Bulk deposition velocity (Vbulk) was calculated along the transect using the surface ocean decay inventory of the naturally occurring radionuclide,7Be, and aerosol7Be activity. Deposition velocities were significantly higher (4,570 ± 1,146 m/d) within the Intertropical Convergence Zone than elsewhere (1,764 ± 261 m/d) due to aerosol scavenging by intense rainfall. Daily deposition fluxes to the central Pacific during the low dust season were calculated using Vbulkand aerosol TE concentration data, with Fe fluxes ranging from 19 to 258 nmol/m2/d.
Limmer, Matt A., Webb, Samuel M., and Seyfferth, Angelia L. Evaluation of quantitative synchrotron radiation micro-X-ray fluorescence in rice grain. Retrieved from https://par.nsf.gov/biblio/10468426. Journal of Synchrotron Radiation 30.2 Web. doi:10.1107/S1600577523000747.
Limmer, Matt A., Webb, Samuel M., & Seyfferth, Angelia L. Evaluation of quantitative synchrotron radiation micro-X-ray fluorescence in rice grain. Journal of Synchrotron Radiation, 30 (2). Retrieved from https://par.nsf.gov/biblio/10468426. https://doi.org/10.1107/S1600577523000747
Limmer, Matt A., Webb, Samuel M., and Seyfferth, Angelia L.
"Evaluation of quantitative synchrotron radiation micro-X-ray fluorescence in rice grain". Journal of Synchrotron Radiation 30 (2). Country unknown/Code not available: Wiley-Blackwell. https://doi.org/10.1107/S1600577523000747.https://par.nsf.gov/biblio/10468426.
@article{osti_10468426,
place = {Country unknown/Code not available},
title = {Evaluation of quantitative synchrotron radiation micro-X-ray fluorescence in rice grain},
url = {https://par.nsf.gov/biblio/10468426},
DOI = {10.1107/S1600577523000747},
abstractNote = {Concentrations of nutrients and contaminants in rice grain affect human health, specifically through the localization and chemical form of elements. Methods to spatially quantify the concentration and speciation of elements are needed to protect human health and characterize elemental homeostasis in plants. Here, an evaluation was carried out using quantitative synchrotron radiation microprobe X-ray fluorescence (SR-µXRF) imaging by comparing average rice grain concentrations of As, Cu, K, Mn, P, S and Zn measured with rice grain concentrations from acid digestion and ICP-MS analysis for 50 grain samples. Better agreement was found between the two methods for high-Zelements. Regression fits between the two methods allowed quantitative concentration maps of the measured elements. These maps revealed that most elements were concentrated in the bran, although S and Zn permeated into the endosperm. Arsenic was highest in the ovular vascular trace (OVT), with concentrations approaching 100 mg kg−1in the OVT of a grain from a rice plant grown in As-contaminated soil. Quantitative SR-µXRF is a useful approach for comparison across multiple studies but requires careful consideration of sample preparation and beamline characteristics.},
journal = {Journal of Synchrotron Radiation},
volume = {30},
number = {2},
publisher = {Wiley-Blackwell},
author = {Limmer, Matt A. and Webb, Samuel M. and Seyfferth, Angelia L.},
}
Warning: Leaving National Science Foundation Website
You are now leaving the National Science Foundation website to go to a non-government website.
Website:
NSF takes no responsibility for and exercises no control over the views expressed or the accuracy of
the information contained on this site. Also be aware that NSF's privacy policy does not apply to this site.
