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Rapid determination of ultra-trace plutonium isotopes (239Pu, 240Pu and 241Pu) in small-volume human urine bioassay using sector-field inductively coupled plasma mass spectrometry

Date: 2018-02-13

Authors: Ni, Y;Zheng, J;Guo, Q;Men, W;Tagami, K;Uchida, S;
Journal: Anal. Chim. Acta
Volume: 1000  -  Pages: 85-92
DOI: 10.1016/j.aca.2017.10.012

A rapid method with enhanced 238U decontamination was developed for ultra-trace Pu analysis in small-volume urine bioassays. This method consists of acid digestion, co-precipitation, extraction chromatography and sector-field inductively coupled plasma mass spectrometry (SF-ICP-MS) measurement. Parameters that may influence the analytical performance were studied systematically. This method achieved a high 238U decontamination factor (3.8 x 106) and the 242Pu recovery was stable for 20 mL and 100 mL urine bioassays with an average value of 72.7 ± 5.5%. The limits of detection for 239Pu, 240Pu and 241Pu by the method were 0.016 fg mL-1, 0.016 fg mL-1 and 0.019 fg mL-1 for 20 mL urine samples and 0.003 fg mL-1, 0.002 fg mL-1 and 0.003 fg mL-1 for 100 mL urine samples, respectively. Considering the small volume of urine employed in this study, the absolute detection limits of the method were comparable or even better than those measured with thermal ionization mass spectrometry and accelerator mass spectrometry. All procedures for 20 mL and 100 mL urine bioassays were completed in 9.5 h and 11 h, respectively, and analysis of 10 samples could be finished within one day. With the considerably low detection limits of Pu isotopes and high sample throughput, this method would be a promising tool for the quick response to radiological emergencies and for rapid screening of unexpected occupational exposures of workers involved in the future FDNPP reactor decommissioning operations.

Mono-acyl arsenosugar phospholipids in the edible brown alga Kombu (Saccharina japonica)

Date: 2018-02-01

Authors: Yu, X;Xiong, C;Jensen, KB;Glabonjat, RA;Stiboller, M;Raber, G;Francesconi, KA;
Journal: Food Chem
Volume: 240  -  Pages: 817-821
DOI: 10.1016/j.foodchem.2017.08.024

Twenty one arsenolipids, including eight new compounds (AsSugPL 692, AsSugPL 706, AsSugPL 720, AsSugPL 734, AsSugPL 742, AsSugPL 746, AsSugPL 748, and AsSugPL 776) were identified in the edible brown alga Kombu, Saccharina japonica, by means of HPLC coupled with elemental and molecular mass spectrometry. The hitherto undescribed compounds are all mono-acyl arsenosugar phospholipids, differing from previously reported natural arsenic-containing phospholipids by containing only one fatty acid on the glycerol group. Collectively, this new group of mono-acyl compounds constituted about 30% of total lipid arsenic; other significant groups were the di-acyl arsenosugar phospholipids (50%) and arsenic hydrocarbons (20%). The origin and relevance of the mono-acyl arsenosugar phospholipids in Kombu, a commercial seafood product, is briefly discussed.

A new procedure for high precision isotope ratio determinations of U, Cu and Zn at nanogram levels in cultured human cells: What are the limiting factors?

Date: 2018-02-01

Authors: Paredes, E;Avazeri, E;Malard, V;Vidaud, C;Ortega, R;Nonell, A;Isnard, H;Chartier, F;Bresson, C;
Journal: Talanta
Volume: 178  -  Pages: 894-904
DOI: 10.1016/j.talanta.2017.10.046

The monitoring of isotopic fractionations in in vitro cultured human cell samples is a very promising and under-exploited tool to help identify the metabolic processes leading to disease-induced isotopic fractionations or decipher metabolic pathways of toxic metals in these samples. One of the limitations is that the analytes are often present at small amounts, ranging from tens to hundreds of ng, thus making challenging low-uncertainty isotope ratio determinations. Here we present a new procedure for U, Cu and Zn purification and isotope ratio determinations in cultured human neuron-like cells exposed to natural U. A thorough study of the influence of the limiting factors impacting the uncertainty of δ239U, δ66Zn and δ65Cu is also carried out. These factors include the signal intensity, which determines the within-day measurement reproducibility, the procedural blank correction and the matrix effects, which determine the accuracy of the mass bias correction models. Given the small Cu and U amounts in the cell samples, 15-30 and 20 ng respectively, a highly efficient sample introduction system was employed in order to improve the analyte transport to the plasma and, hence, the signal intensity. With this device, the procedural blanks became the main uncertainty source of δ239U and δ65Cu values, accounting over 65% of the overall uncertainty. The matrix effects gave rise to inaccuracies in the mass bias correction models for samples finally dissolved in the minimal volumes required for the analysis, 100-150 µL, leading to biases for U and Cu. We will show how these biases can be cancelled out by dissolving the samples in volumes of at least 300 µL for Cu and 450 µL for U. Using our procedure, expanded uncertainties (k = 2) of around 0.35‰ for δ239U and 0.15‰ for δ66Zn and δ65Cu could be obtained. The analytical approach presented in this work is also applicable to other biological microsamples and can be extended to other elements and applications.

High-precision determination of lithium and magnesium isotopes utilising single column separation and multi-collector inductively coupled plasma mass spectrometry

Date: 2018-01-30

Authors: Bohlin, MS;Misra, S;Lloyd, N;Elderfield, H;Bickle, MJ;
Journal: Rapid Commun. Mass Spectrom.
Volume: 32  -  Pages: 93-104
DOI: 10.1002/rcm.8020

Rationale: Li and Mg isotopes are increasingly used as a combined tool within the geosciences. However, established methods require separate sample purification protocols utilising several column separation procedures. This study presents a single-step cation-exchange method for quantitative separation of trace levels of Li and Mg from multiple sample matrices. Methods: The column method utilises the macro-porous AGMP-50 resin and a high-aspect ratio column, allowing quantitative separation of Li and Mg from natural waters, sediments, rocks and carbonate matrices following the same elution protocol. High-precision isotope determination was conducted by multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS) on the Thermo ScientificTM NEPTUNE PlusTM fitted with 1013 Ω amplifiers which allow accurate and precise measurements at ion beams ≤0.51 V. Results: Sub-nanogram Li samples (0.3-0.5 ng) were regularly separated (yielding Mg masses of 1-70 µg) using the presented column method. The total sample consumption during isotopic analysis is <0.5 ng Li and <115 ng Mg with long-term external 2σ precisions of ±0.39‰ for σ7 Li and ±0.07‰ for σ26 Mg. The results for geological reference standards and seawater analysed by our method are in excellent agreement with published values despite the order of magnitude lower sample consumption. Conclusions: The possibility of eluting small sample masses and the low analytical sample consumption make this method ideal for samples of limited mass or low Li concentration, such as foraminifera, mineral separates or dilute river waters.

Lithium, magnesium and sulfur purification from seawater using an ion chromatograph with a fraction collector system for stable isotope measurements

Date: 2018-01-05

Authors: Yoshimura, T;Araoka, D;Tamenori, Y;Kuroda, J;Kawahata, H;Ohkouchi, N;
Journal: J Chromatogr A
Volume: 1531  -  Pages: 157-162
DOI: 10.1016/j.chroma.2017.11.052

We describe the mass descrimination and validation of an offline method for purification of Li, Mg and S with an ion chromatograph coupled to an automated fraction collector for use prior to stable isotope measurements. Significant sub-fraction mass fractionation was observed for both the Li and the Mg stable isotope ratios. The lighter Li and heavier Mg isotopes were preferentially retained by the column, resulting in 7Li/6Li and 26Mg/24Mg biases up to 85.8‰ and 0.95‰, respectively. The isotopic compositions of Li, Mg, and S separated from seawater were δ7LiL-SVEC = +30.9‰, δ26MgDSM3 = -0.83 ± 0.10‰, and δ34SVCDT = +19.4 ± 0.6‰; each chromatographic peak was completely recovered, and the results were in good agreement with the published values regardless of whether or not chemical suppressor was used. The purification method enables multi-isotope analysis of a sample using various mass spectrometry techniques, such as multiple-collector inductively coupled plasma and thermal ionization mass spectrometry.

Excess Lead-210 and Plutonium-239+240: Two suitable radiogenic soil erosion tracers for mountain grassland sites

Date: 2018-01-01

Authors: Meusburger, K;Porto, P;Mabit, L;La Spada, C;Arata, L;Alewell, C;
Journal: Environ. Res.
Volume: 160  -  Pages: 195-202
DOI: 10.1016/j.envres.2017.09.020

The expected growing population and challenges associated with globalisation will increase local food and feed demands and enhance the pressure on local and regional upland soil resources. In light of these potential future developments it is necessary to define sustainable land use and tolerable soil loss rates with methods applicable and adapted to mountainous areas. Fallout-radionuclides (FRNs) are proven techniques to increase our knowledge about the status and resilience of agro-ecosystems. However, the use of the Caesium-137 (137Cs) method is complicated in the European Alps due to its heterogeneous input and the timing of the Chernobyl fallout, which occurred during a few single rain events on partly snow covered ground. Other radioisotopic techniques have been proposed to overcome these limitations. The objective of this study is to evaluate the suitability of excess Lead-210 (210Pbex) and Plutonium-239+240 (239+240Pu) as soil erosion tracers for three different grassland management types at the steep slopes (slope angles between 35 and 38°) located in the Central Swiss Alps. All three FRNs identified pastures as having the highest mean (± standard deviation) net soil loss of -6.7 ± 1.1, -9.8 ± 6.8 and -7.0 ± 5.2 Mg ha-1 yr-1 for 137Cs, 210Pbex and 239+240Pu, respectively. A mean soil loss of -5.7 ± 1.5, -5.2 ± 1.5 and -5.6 ± 2.1 was assessed for hayfields and the lowest rates were established for pastures with dwarf-shrubs (-5.2 ± 2.5, -4.5 ± 2.5 and -3.3 ± 2.4 Mg ha-1 yr-1 for 137Cs, 210Pbex and 239+240Pu, respectively). These rates, evaluated at sites with an elevated soil erosion risk exceed the respective soil production rates. Among the three FRN methods used, 239+240Pu appears as the most promising tracer in terms of measurement uncertainty and reduced small scale variability (CV of 13%). Despite a higher level of uncertainty, 210Pbex produced comparable results, with a wide range of erosion rates sensitive to changes in grassland management. 210Pbex can then be as well considered as a suitable soil tracer to investigate alpine agroecosystems.

Vertical distributions and source identification of the radionuclides 239Pu and 240Pu in the sediments of the Liao River estuary, China.

Date: 2018-01-01

Authors: Zhang, K;Pan, S;Liu, Z;Li, G;Xu, Y;Hao, Y;
Journal: J Environ Radioact
Volume: 181  -  Pages: 78-84
DOI: 10.1016/j.jenvrad.2017.10.016

Activity concentration of plutonium (Pu) and its isotopic compositions are extensively used for measuring transport processes of Pu and identifying its source. We investigated the spatial distribution characteristics of 239+240Pu activity concentrations and 240Pu/239Pu atom ratio in several sediment cores collected from the Liao River coastal zone. Additionally, we calculated the 239+240Pu inventories and based on the 240Pu/239Pu atom ratio to trace Pu source. The activity concentrations of 239+240Pu in surface sediments of the Liao River estuary ranged between 0.103±0.008 and 0.978±0.035 mBq/g, with an average of 0.294±0.024 mBq/g. The 240Pu/239Pu atom ratios, ranging from 0.173±0.047 to 0.215±0.061 (mean: 0.188±0.049 (1σ)), were consistent with global fallout value, which indicates the global atmospheric fallout is the main source of Pu in sediment cores from the both sides of Liao River estuary. As for the tidal flat core LT-2, the mean 240Pu/239Pu atom ratio, slightly higher than that of the global fallout value, was 0.217±0.050. Such pattern of Pu isotopic compositions indicated that Pu on the tidal flat in the Liao River estuary is sourced from a combination of global fallout and close-in fallout from the PPG by ocean currents transporting. And by using a two end-member mixing model, the results indicate the relative contribution of the PPG close-in fallout to core LT-2 is round 27% and 73% can be attributed to global fallout and river input. Therefore, these results clearly indicate that the direct global fallout is the main source of Pu in the Liao River estuary.

Spatially resolved quantification of gadolinium deposited in the brain of a patient treated with gadolinium-based contrast agents

Date: 2018-01-01

Authors: Fingerhut, S;Niehoff, AC;Sperling, M;Jeibmann, A;Paulus, W;Niederstadt, T;Allkemper, T;Heindel, W;Holling, M;Karst, U;
Journal: J Trace Elem Med Biol
Volume: 45  -  Pages: 125-130
DOI: 10.1016/j.jtemb.2017.10.004

Due to its paramagnetic properties resulting from seven unpaired f-electrons, Gd is frequently applied in magnetic resonance imaging examinations. Due to the acute toxicity of free Gd3+, ligand ions based on polyaminocarboxylic acids are used to create thermodynamically stable linear or macrocyclic complexes. The highly water soluble Gd-based contrast agents (GBCAs) are known to be excreted fast and unmetabolized, mostly via the kidneys. Nevertheless, recent studies showed that Gd traces persists not only in animal but also in human brain. Aim of this study was the development and application of an analytical method for the spatially resolved quantification of gadolinium traces in human brain thin sections of a patient treated with GBCAs. For this retrospective study different human brain regions were selected to analyze the distribution of gadolinium. An additional patient served as control sample, as no GBCA was administered. Deep-frozen brain thin sections were analyzed by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) and matrix-matched gelatin standards were prepared to quantify the gadolinium deposits via an external calibration. LA-ICP-MS analyses with high spatial resolution showed gadolinium deposits in different brain regions with highest concentrations above 800 ng g-1 more than two years after the last application of a GBCA. An excellent limit of quantification of 7 ng g-1, which is far below the limits of detection of MRI methods, could be achieved. The found concentrations confirm recent reports on gadolinium depositions in human brain, which were obtained without high spatial resolution. LA-ICP-MS provides limits of quantification, which are well suited to detect ultratrace amounts of gadolinium in human brain. Therefore, it provides valuable information on the distribution of gadolinium traces in the human brain even after single administration of GBCAs.

Inclusion of Solar Elevation Angle in Land Surface Albedo Parameterization Over Bare Soil Surface

Date: 2017-12-29

Authors: Zheng, Z;Wei, Z;Wen, Z;Dong, W;Li, Z;Wen, X;Zhu, X;Ji, D;Chen, C;Yan, D;
Journal: Journal of Advances in Modeling Earth Systems
Volume: 9  -  Pages: 3069-3081
DOI: 10.1002/2017MS001109

Land surface albedo is a significant parameter for maintaining a balance in surface energy. It is also an important parameter of bare soil surface albedo for developing land surface process models that accurately reflect diurnal variation characteristics and the mechanism behind the solar spectral radiation albedo on bare soil surfaces and for understanding the relationships between climate factors and spectral radiation albedo. Using a data set of field observations, we conducted experiments to analyze the variation characteristics of land surface solar spectral radiation and the corresponding albedo over a typical Gobi bare soil underlying surface and to investigate the relationships between the land surface solar spectral radiation albedo, solar elevation angle, and soil moisture. Based on both solar elevation angle and soil moisture measurements simultaneously, we propose a new two-factor parameterization scheme for spectral radiation albedo over bare soil underlying surfaces. The results of numerical simulation experiments show that the new parameterization scheme can more accurately depict the diurnal variation characteristics of bare soil surface albedo than the previous schemes. Solar elevation angle is one of the most important factors for parameterizing bare soil surface albedo and must be considered in the parameterization scheme, especially in arid and semiarid areas with low soil moisture content. This study reveals the characteristics and mechanism of the diurnal variation of bare soil surface solar spectral radiation albedo and is helpful in developing land surface process models, weather models, and climate models.

Diagnostic potential of major and trace elements in the serum of bladder cancer patients

Date: 2017-12-28

Authors: Wach, S;Weigelt, K;Michalke, B;Lieb, V;Stoehr, R;Keck, B;Hartmann, A;Wullich, B;Taubert, H;Chaudhri, A;
Journal: Journal of Trace Elements in Medicine and Biology
Volume: 46  -  Pages: 150-155
DOI: 10.1016/j.jtemb.2017.12.010

Major and trace elements may play a role in the diagnosis of diseases. In this study, we investigated the concentration of 26 major and trace elements in the serum by inductively coupled plasma (ICP)-optical emission spectrometry (OES) and ICP-sector field-mass spectrometry (sf-MS). We analyzed the serum from a discovery cohort of 6 bladder cancer (BCa) patients and 12 healthy controls as well as from a validation cohort of 21 BCa patients, 29 non-tumor bladder patients (with acute and chronic inflammation) and 18 healthy controls. Patients were recruited after written consent was obtained at one medical center. Serum was prepared from peripheral blood prior to surgical treatment. Differences in the levels of major and trace elements were determined by a nonparametric Mann-Whitney test and Kruskal-Wallis statistics. In the discovery cohort, we measured significantly increased levels of calcium, mercury, potassium, lithium, nickel, phosphorus and strontium and a significantly decreased level of sodium in BCa patients compared with healthy controls. These findings were reassessed in our validation cohort. We measured significantly increased levels of boron, calcium, cadmium, copper, chromium, lead, lithium, potassium, magnesium, nickel, sulfur, strontium, titan, vanadium and zinc and significantly decreased levels of iron and molybdenum. When we studied the concordance for the discovery and validation cohorts, concentrations of five elements were detected as significantly increased in BCa patients compared with healthy controls: calcium, lithium, potassium, nickel, and strontium. Interestingly, the levels of three elements (calcium, potassium and strontium) were also significantly increased in non-tumor bladder patients compared with healthy controls. But no element was significantly altered between non-tumor bladder patients and BCa patients. In summary, we suggest that determination of the elements calcium, lithium, nickel and strontium in the serum could be a new and promising tool for the early diagnosis of BCa.

The distribution of dissolved cadmium in the Canadian Arctic Ocean

Date: 2017-12-22

Authors: Jackson, S;
Journal: Thesis
Volume: 1  -  Pages: 1-109

The biogeochemical cycling of oceanic dissolved cadmium (dCd) has been an active area of research for the past ~40 years, due in part to the close correlation with phosphate (PO4). The global Cd:PO4 relationship has led to the use of microfossil Cd/Ca as a paleoproxy for oceancirculation and nutrient utilization; however considerable spatial and temporal variability in the relationship - particularly in surface waters - limits the utility of the proxy. Understanding the global biogeochemical cycling of Cd is an active area of research; however the Arctic Ocean is largely omitted from global models due to lack of data. This work presents depth profiles of dCd and Cd/PO4 ratios from 18 individual stations in the Canadian Arctic, collected during the Canadian GEOTRACES cruises GN02 and GN03, which connect the Arctic Ocean to the North Atlantic through the Canadian Arctic Archipelago (CAA). Salinity-driven water mass stratification exerts a primary control on the spatial distribution of Cd in the region, with elevated dCd and high Cd/PO4 ratios (~0.37 pM/µM) associated with waters of Pacific-origin. The elevated dCd and Cd/PO4 ratios are used as a tracer of Pacific-origin waters, identifying the presence of Pacific-origin water through the CAA and into Baffin Bay. High surface Cd/PO4 ratios were observed across the transect, consistent with a general global increase in surface water Cd/PO4 with increasing latitude. The analysis of Cd and other bioactive trace metals (Mn, Fe, Ni, Cu, Zn and Pb) still presents considerable analytical challenges due to the high-risks of contamination, low concentrations and complex matrices. I present a novel multi-element analytical method, which combines the commercially-available seaFAST pico preconcentration system with ICP-MS/MS analysis. In this work, we demonstrate that ICP-MS/MS, which combines two mass-selecting quadrupoles separated by an octopole collision/reaction cell, effectively removes common interferences (ArO+ on 56Fe and MoO+ on Cd) when pressurized with O2 gas. Accurate and precise measurements of the consensus references standards SAFe S and SAFe D and the certified reference material NASS-6 are presented as validation of the method. This thesis presents a novel method for the analysis of trace elements in seawater and discusses the biogeochemical cycling of Cd in the Arctic Ocean.

Conical Torch: The Next-Generation Inductively Coupled Plasma Source for Spectrochemical Analysis

Date: 2017-12-21

Authors: Alavi, S;Khayamian, T;Mostaghimi, J;
Journal: Anal. Chem.
Volume:   -  Pages:
DOI: 10.1021/acs.analchem.7b04356

A completely new ICP torch for optical/mass spectrometry is introduced with a conical geometry leading to significant reduction in gas and power consumption. As a new holistic methodology, the torch has been designed based on fluid flow patterns, heat transfer, plasma physics, and analytical performance. Computer simulations, capable of accounting for magneto-hydrodynamic effects, have been used to optimize torch geometry. The result is a "conical" torch with up to 70% reduction in argon flow and more than 4 times power density compared with traditional "cylindrical" torches. Based on experimental measurements, these features lead to a stable plasma with 1000-1700K higher excitation/rotational temperature and a 5-fold increase in electron number density compared to common torches. Interferences from easily-ionizable elements (e.g., Na) are also observed to be minimized due to 3 times higher robustness (Mg II/Mg I ratio). Eventually, analytical parameters including detection limits for multi-element analysis indicate comparable/better performance of the new torch in comparison with conventional torches.

Water quality assessment based on the water quality index method in Lake Poyang: The largest freshwater lake in China

Date: 2017-12-21

Authors: Wu, Z;Zhang, D;Cai, Y;Wang, X;Zhang, L;Chen, Y;
Journal: Sci Rep
Volume: 7  -  Pages: 17999
DOI: 10.1038/s41598-017-18285-y

Twenty-four samplings were conducted every 3 months at 15 sites from January 2009 to October 2014 in Lake Poyang, and 20 parameters were analyzed and classified into three groups (toxic metals, easily treated parameters, and others). The assessment results based on water quality index (WQI) showed that the water quality in Lake Poyang was generally "moderate", according to the classification of the surface water quality standard (GB3838-2002) in China, but a deteriorating trend was observed at the interannual scale. Seasonally, the water quality was best in summer and worst in winter. Easily treated parameters generally determined the WQI value in the assessment, especially total nitrogen (TN) and total phosphorus (TP), while toxic metals and other parameters in Lake Poyang were generally at low and safe levels for drinking water. Water level (WL) has a net positive effect on water quality in Lake Poyang through dilution of environmental parameters, which in practice means TN. Consequently, local management agencies should pay more attention to nutrient concentrations during the monitoring schedule, as well as during the low-water periods which manifest a relatively bad water quality state, especially with the prevailing low WL observed recently in Lake Poyang.

High latitude Southern Hemisphere fire history during the Mid-Late Holocene (750-6000 yr BP)

Date: 2017-12-21

Authors: Battistel, D;Kehrwald, NM;Zennaro, P;Pellegrino, G;Barbaro, E;Zangrando, R;Pedeli, XX;Varin, C;Spolaor, A;Vallelonga, PT;Gambaro, A;Barbante, C;
Journal: Climate of the Past Discussions
Volume: 1  -  Pages: 1-28
DOI: 10.5194/cp-2017-158

High latitude Southern Hemisphere fire history was reconstructed by determining the specific biomarker levoglucosan in ice cores from the TALos Dome Ice CorE drilling project (TALDICE) during the Mid-Late Holocene (750- 6000 yr BP). Potassium was also analyzed in order to provide a comparison with another fire proxy to create a more robust biomass burning record. The levoglucosan record is characterized by a long-term increase with higher rates starting at~4000 yr BP and higher peaks between 1500 and 2500 yr BP. Comparisons with charcoal syntheses help evaluate fire sources, showing a possible higher contribution from Patagonian fires rather than Australian biomass burning. We interpret the anomalous increase in levoglucosan centred at ~2000 yr BP as a combination of the atmospheric transport pathway and the interplay between climatic factors.

Seasonal progression of the deposition of black carbon by snowfall at Ny-Ålesund, Spitsbergen

Date: 2017-12-21

Authors: Sinha, PR;Kondo, Y;Goto-Azuma, K;Tsukagawa, Y;Fukuda, K;Koike, M;Ohata, S;Moteki, N;Mori, T;Oshima, N;Førland, EJ;Irwin, M;Gallet, J;Pedersen, CA;
Journal: Journal of Geophysical Research
Volume:   -  Pages:
DOI: 10.1002/2017JD028027

Deposition of black carbon (BC) aerosol in the Arctic lowers snow albedo, thus contributing to warming in the region. However, the processes and impacts associated with BC deposition are poorly understood because of the scarcity and uncertainties of measurements of BC in snow with adequate spatiotemporal resolution. We sampled snowpack at two sites (11 m and 300 m above sea level) at Ny-Ålesund, Spitsbergen, in April 2013. We also collected falling snow near the surface with a windsock from September 2012 to April 2013. The size distribution of BC in snowpack and falling snow was measured using a single-particle soot photometer combined with a characterized nebulizer. The BC size distributions did not show significant variations with depth in the snowpack, suggesting stable size distributions in falling snow. The BC number and mass concentrations (CNBC and CMBC) at the two sites agreed to within 19% and 10%, respectively, despite the sites' different snow water equivalent (SWE) loadings. This indicates the small influence of the amount of SWE (or precipitation) on these quantities. Average CNBC and CMBC in snowpack and falling snow at nearly the same locations agreed to within 5% and 16%, after small corrections for artifacts associated with the sampling of the falling snow. This comparison shows that the dry deposition was a small contributor to the total BC deposition. CMBC were highest (2.4 ± 3.0 µg L-1) in December-February and lowest (1.2 ± 1.2 µg L-1) in September-November.

Vertical distribution of major, minor and trace elements in sediments from mud volcanoes of the Gulf of Cadiz: evidence of Cd, As and Ba fronts in upper layers

Date: 2017-12-20

Authors: Carvalho, L;Monteiro, R;Figueira, P;Mieiro, C;Almeida, J;Pereira, E;Magalhães, V;Pinheiro, L;Vale, C;
Journal: Deep Sea Research Part I: Oceanographic Research Papers
Volume:   -  Pages:
DOI: 10.1016/j.dsr.2017.12.003

Mud volcanoes are feature of the coastal margins where anaerobic oxidation of methane triggers geochemical signals. Elemental composition, percentage of fine particles and loss on ignition were determined in sediment layers of eleven gravity cores retrieved from four mud volcanoes (Sagres, Bonjardim, Soloviev and Porto) and three undefined structures located on the deep Portuguese margin of the Gulf of Cadiz. Calcium was positively correlated to Sr and inversely to Al as well as to most of the trace elements. Vertical profiles of Ba, Cd and As concentrations, and their ratios to Al, in Porto and Soloviev showed pronounced enhancements in the top 50-cm depth. Sub-surface enhancements were less pronounced in other mud volcanoes and were absent in sediments from the structures. These profiles were interpreted as diagenetic enrichments related to the anaerobic oxidation of methane originated from upward methane-rich fluxes. The observed barium fronts were most likely caused by the presence of barite which precipitated at the sulphate-methane transition zone. Cd and As enrichments have probably resulted from successive dissolution/precipitation of sulphides in response to vertical shifts of redox boundaries.

Spontaneous and mass-conserved formation of continuous Si frameworks

Date: 2017-12-19

Authors: Kogata, ;D-SKo, ;Jung, C;Lee, J;Sul, S;H-GKim, ;Seo, J;JJang, ;Koh, M;Kim, K;JHKim, ;Jung, I;Park, MS;KTakei, ;KIto, ;Kubo, Y;Uosaki, K;Doo, S;SHan, ;Shin, J;SJeon, ;
Journal: arXiv
Volume:   -  Pages: 1-38

Controlled formation of porous silicon has been of primary importance for numerous landmark applications such as light emitting sources, sensors, actuators, drug delivery systems, and energy storage applications. Frequently explored methods to form the structures have long relied on selective etching of silicon, which still stands as the most controllable and reliable methods to highlight essence of the applications. Here, we demonstrate an unprecedented approach to form silicon framework, which is spontaneously formed with atomistic arrangement of silicon without gravimetric loss via single electrochemical (de)alloying with lithium. Carefully controlling bare crystallinity of Si and composite/electrode designs, we reveal that the key prerequisite to forming the structure lies in using unique dealloying dynamics of crystalline-amorphous phase transformations at room temperature. Using the feature, we clearly highlight that commercially available nano-structured silicon particles can abruptly yet uniformly transform into continuous sub-2 nm spherical silicon frameworks with size-tunable pores.

Straw Application Strategy to Optimize Nutrient Release in a Southeastern China Rice Cropland

Date: 2017-12-15

Authors: Wang, W;Sardans, J;Wang, C;Pan, T;Zeng, C;Lai, DY;Bartrons, M;Penuelas, J;
Journal: Agronomy
Volume: 7  -  Pages: 84
DOI: 10.3390/agronomy7040084

The management and improvement of paddy soils fertility are key factors for the future capacity of rice production. The return of rice straw to paddy soils is the best alternative to the application of industrial fertilizers for rice production sustainability. The best strategy for applying rice straw to improve soil nutritional capacity during rice growth has not yet been investigated. We compared straw decomposition in the ditches and ridges in paddy fields subjected to a typical crop management in southeastern China. Straw spread on the ridges provided lower residual straw carbon (C) concentration and mass, lower nitrogen:phosphorus ratio N:P, C:N, and C:P ratios, and lower soil salinity, as well as higher temperature, and higher N- and P-release capacity during the rice crop in comparison to the straw spread in the ditches. Therefore, applying rice straw to the ridges is better strategy than applying it to ditches to enhance rice production.

The Rv2633c protein of Mycobacterium tuberculosis is a non-heme di-iron catalase with a possible role in defenses against oxidative stress

Date: 2017-12-14

Authors: Ma, Z;Strickland, KT;Cherne, MD;Sehanobish, E;Rohde, KH;Self, WT;Davidson, VL;
Journal: J. Biol. Chem.
Volume:   -  Pages:
DOI: 10.1074/jbc.RA117.000421

The Rv2633c gene in Mycobacterium tuberculosis is rapidly upregulated after macrophage infection, suggesting that Rv2633c is involved in M. tuberculosis pathogenesis. However, the activity and role of the Rv2633c protein in host colonization is unknown. Here, we analyzed the Rv2633c protein sequence, which revealed the presence of an HHE cation-binding domain common in hemerythrin-like proteins. Phylogenetic analysis indicated that Rv2633c is a member of a distinct subset of hemerythrin-like proteins exclusive to mycobacteria. The Rv2633c sequence was significantly similar to protein sequences from other pathogenic strains within that subset, suggesting that these proteins are involved in mycobacteria virulence. We expressed and purified the Rv2633c protein in E. coli and found that it contains two iron atoms, but does not behave like a hemerythrin. It migrated as a dimeric protein during size-exclusion chromatography. It was not possible to reduce the protein nor observe any evidence for its interaction with O2 However, Rv2633c did exhibit catalase activity with a kcat of 1475 s-1 and Km of 10.1 ± 1.7 mM. Cyanide and azide inhibited the catalase activity with Ki values of 3.8 µM and 37.7 µM, respectively. Rv2633c's activity was consistent with a role in defenses against oxidative stress generated during host immune responses after M. tuberculosis infection of macrophages. We note that Rv2633c is the first example of a non-heme di-iron catalase, and conclude that it is a member of a subset of hemerythrin-like proteins exclusive to mycobacteria, with likely roles in protection against host defenses.

Ultra-trace Determination of Bromine and Iodine in Rice by ICP-MS after Microwave-Induced Combustion

Date: 2017-12-13

Authors: Rondan, FS;Hartwig, CA;Novo, DL;Moraes, DP;Cruz, SM;Mello, PA;Mesko, MF;
Journal: Journal of Food Composition and Analysis
Volume: 66  -  Pages: 199-204
DOI: 10.1016/j.jfca.2017.12.023

In this study, a method for bromine and iodine determination in rice by inductively coupled plasma spectrometry (ICP-MS) after digestion by microwave-induced combustion (MIC) was developed.Samples (up to 1000 mg) were digested in closed system pressurized with oxygen. Ultrapure water and NH4OH solutions were evaluated as absorbing solution. Recoveries from 98 to 108% were obtained for Br and I using 50 mmol L-1 NH4)H, and the relative standard deviation (RSDs) were up to 9 to 11% for Br and I, respectively. Limits of detection (LODs) of 0.004 and 0.0008 mg kg-1 for Br and I, resectively, were obtained. These LODs were lower than those reported in the literature, and it was possilbe due to high sample mass digested by MIC associated with the detection capability of ICP-MS. The proposed method was applied to 23 samples of rice from different countries and types. The results showed a waide variation for Br concentration (0.304 to 55.7 mg kg-1), whereas for I it was not observed (<0.003 to 0.031 mg kg-1). In this way, the proposed method presents several advantages for the routine analysis and indicated it is an excellent alternative for BR and I determintaion in rice.

Arsenolipid biosynthesis by the unicellular alga Dunaliella tertiolecta is influenced by As/P ratio in culture experiments

Date: 2017-12-12

Authors: Glabonjat, RA;Ehgartner, J;Duncan, EG;Raber, G;Jensen, KB;Krikowa, F;Maher, WA;Francesconi, KA;
Journal: Metallomics
Volume:   -  Pages:
DOI: 10.1039/C7MT00249A

The influence of arsenate and phosphate levels in water on the formation of arsenic-containing lipids (arsenolipids) and water-soluble arsenicals by a unicellular marine alga was investigated by exposing Dunaliella tertiolecta to five regimes of arsenic and phosphate, and determining the biosynthesized organoarsenicals with HPLC/mass spectrometry. Under all conditions, the major arsenolipid produced by D. tertiolecta was the novel phytyl 5-dimethylarsinoyl-2-O-methyl-ribofuranoside (AsSugPhytol546) representing ca. 35-65% of total arsenolipids. The new compound contains a phytol aglycone and a methoxy group replacing a sugar hydroxyl - two structural features not previously observed for arsenolipids. Minor arsenolipids were several previously reported arsenosugar phospholipids (AsSugPLs, in particular AsSugPL958 and the previously unknown AsSugPL978), the relative quantities of which increased with increasing phosphate exposure, and an arsenic-containing hydrocarbon (AsHC360), which remained unaffected by the different treatments. The relative amount of total arsenolipids produced by D. tertiolecta remained remarkably constant (ca. 45% of total As) and independent of the culture conditions. In contrast, with rising As-concentrations we observed an increase of hydrophilic arsenicals, which were dominated by arsenate and arsenosugars. The results highlight a possible major difference in arsenic biochemistry between macroalgae and unicellular algae with potential implications for how various algae handle their natural arsenic exposure in the world's oceans.

Molybdenum isotope fractionation in plants measured by MC-ICPMS

Date: 2017-12-12

Authors: Malinovsky, D;Kashulin, NA;
Journal: Analytical Methods
Volume: 10  -  Pages: 131-137
DOI: 10.1039/C7AY02316B

A new method was developed for precise and accurate Mo isotope ratio measurements in plant materials by multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS). It is based on the use of anion-exchange chromatography to isolate Mo from concomitant matrix elements in sample digests, a desolvating Apex-Q sample inlet system as a means of Mo signal enhancement and on-line normalisation to an admixed internal standard (Pd) to correct for instrumental mass bias. Mo isotope ratios were determined in sample solutions with Mo concentrations as low as 10 ng g-1. The developed method was successfully applied to the determination of natural variations in the isotopic composition of Mo in different anatomical parts of plants. We show for the first time that Mo isotope fractionation can occur during long-distance transport of Mo in plants. Our data also show that the magnitude of Mo isotope fractionation during translocation of Mo is different for different plant species. Mo isotope ratio data obtained by MC-ICPMS can therefore be used as a sensitive probe of processes controlling transport and distribution of molybdenum in plants.

Advanced source apportionment of carbonaceous aerosols by coupling offline AMS and radiocarbon size segregated measurements over a nearly two-year period.

Date: 2017-12-12

Authors: Vlachou, A;Daellenbach, KR;Bozzetti, C;Chazeau, B;Salazar, GA;Szidat, S;Jaffrezo, J;Hueglin, C;Baltensperger, U;Haddad, IE;Prévôt, AS;
Journal: Atmospheric Chemistry and Physics Discussions
Volume: 1  -  Pages: 1-25
DOI: 10.5194/acp-2017-1102

Carbonaceous aerosols are related to adverse human health effects. Therefore, identification of their sources and analysis of their chemical composition is important. The offline AMS technique offers quantitative separation of organic aerosol (OA) factors that can be related to major OA sources either primary or secondary. 20 While primary OA can be more clearly separated into sources, secondary (SOA) source apportionment is more challenging because different sources - anthropogenic or natural, fossil or non-fossil - can yield similar highly oxygenated mass spectra. Radiocarbon measurements provide unequivocal separation between fossil and nonfossil sources of carbon. Here we coupled these two offline methods and analysed the OA and organic carbon (OC) of different size fractions (particulate matter below 10 and 2.5µm - PM10 and PM2.5, respectively) from the 25 Alpine valley of Magadino (Switzerland) during the years 2013 and 2014 (219 samples). The combination of the techniques gave further insights into the characteristics of secondary OC (SOC) which was rather based on the type of SOC precursor and not on the volatility or the oxidation state of OC, as typically considered. Out of the primary sources separated in this study, biomass burning OC was the dominant one in winter with average concentrations of 5.36±2.64 µg m-3 for PM10 and 3.83±1.81 µg m-3 for PM2.5, indicating that wood combustion 30 particles were predominantly generated in the fine mode. The additional information from the size segregated measurements revealed a primary sulphur containing factor, mainly fossil, detected in the coarse size fraction and related to non-exhaust traffic emissions with average yearly PM10 (PM2.5) concentration of 0.20±0.24 µg m-3
(0.05±0.04 µg m-3 ). A primary biological OC was also detected in the coarse mode peaking in spring and summer with yearly average concentrations for PM10 (PM2.5) 0.79±0.31 µg m-3 (0.24±0.20 µg m-3 ). The 35 secondary OC was separated into two oxygenated, non-fossil OC factors which were identified based on their seasonal variability (i.e. summer and winter OOC) and a third fossil OOC factor which correlated with fossil OC mainly peaking in winter and spring with PM10 (PM2.5) contributing on average 13%±7% (10%±9%) to the total OC. The winter OOC was connected to anthropogenic sources, with PM10 (PM2.5) contributing on average 13%±13% (6%±6%) to the total OC. The summer OOC, stemming from oxidation of biogenic emissions was 40 more pronounced in the fine mode with PM10 (PM2.5) contributing on average 43%±12% (75%±44%) to the total OC. In total the non-fossil OC far dominated the fossil OC throughout all seasons, by contributing on average 75%±24% to the total OC. The results also suggested that during the cold period the prevailing source was residential biomass burning while during the warm period primary biological sources and secondary organic aerosol from the oxidation of biogenic emissions became important. However, SOC was also formed by aged fossil fuel combustion emissions not only in summer but also during the rest of the year.

Preliminary Survey of Matrix effects in the Microwave-sustained, Inductively Coupled Atmospheric-pressure Plasma (MICAP)

Date: 2017-12-11

Authors: Thaler, KM;Schwartz, AJ;Haisch, C;Niessner, R;Hieftje, GM;
Journal: Talanta
Volume: 180  -  Pages: 25-31
DOI: 10.1016/j.talanta.2017.12.021

Matrix effects caused by Na and Al in the nitrogen Microwave-sustained, Inductively Coupled, Atmospheric-pressure Plasma (MICAP) were investigated. Easily ionizable elements, such as Na, can suppress or enhance the analyte signal; Al is shown here to produce a similar effect. The influence of these matrices was examined for 18 emission lines of 8 analyte atoms and ions having a wide range of excitation and ionization energies. The plasma operating conditions were fixed during all experiments at a total nitrogen flow of 19.4 L min -1 and a microwave power of 1.5 kW. An Fe solution was used to determine the excitation temperature of the plasma by the Boltzmann plot method at selected matrix concentrations. In addition, vertical emission profiles of the plasma were measured. The matrix effect becomes worse at higher concentrations of an easily ionizable element. The effect is caused not only by a shift in ionization equilibrium but also by a possible change in plasma ionization temperature. Correction methods to reduce the matrix effects were tested and are discussed.

The Level of Toxic Elements in Edible Crops from Seleniferous Area (Punjab, India)

Date: 2017-12-08

Authors: Skalnaya, MG;Jaiswal, SK;Prakash, R;Prakash, NT;Grabeklis, AR;Zhegalova, IV;Zhang, F;Guo, X;Tinkov, AA;Skalny, AV;
Journal: Biol Trace Elem Res
Volume:   -  Pages: 1-6
DOI: 10.1007/s12011-017-1216-7

The primary objective of the present study was to assess the level of selenium and toxic trace elements in wheat, rice, maize, and mustard from seleniferous areas of Punjab, India. The content of selenium (Se) and toxic trace elements, including aluminum (Al), arsenic (As), cadmium (Cd), mercury (Hg), nickel (Ni), lead (Pb), and tin (Sn), in crop samples was assessed using inductively coupled plasma mass-spectrometry after microwave digestion of the samples. The obtained data demonstrate that cultivation of crops on seleniferous soils significantly increased Se level in wheat, mustard, rice, and maize by a factor of more than 590, 111, 85, and 64, respectively. The study also showed that Se exposure affected toxic metal content in crops. In particular, Se-rich wheat was characterized by a significant decrease in Al, As, Ni, Pb, and Sn levels. The level of As, Cd, Ni, Pb, and Sn was significantly decreased in Se-rich rice, whereas As content was increased. In turn, the decrease in Al, As, Cd, Ni, Pb, and Sn levels in Se-rich maize was associated with a significant elevation of Hg content. Finally, Se-rich mustard was characterized by a significant increase in Al, As, and Hg levels, while the content of Ni, Pb, and Sn was significantly lower than the control levels. These findings should be taken into account while developing the nutritional strategies for correction of Se status. At the same time, the exact mechanisms underlying the observed differences are to be estimated.

Arsenic, cadmium and lead concentrations in Yerba mate commercialized in Southern Brazil by inductively coupled plasma mass spectrometry

Date: 2017-12-07

Authors: Santos, LM;Neto, SA;Iozzi, G;Jacob, Sd;
Journal: Ciência Rural
Volume: 47  -  Pages:
DOI: 10.1590/0103-8478cr20170202

"Mate" or "Yerba Mate"(Ilex paraguariensis) is a native South American plant, commonly consumed in Argentina, Paraguay, Uruguay and southern Brazil. Recent research has detected the presence of many vitamins and metals in this plant. Theses metals are also part of yerba mate's mineral composition, due to soil and water contamination by pesticides and fertilizers, coal and oil combustion, vehicle emissions, mining, smelting, refining and the incineration of urban and industrial waste. Regardless of their origin, some inorganic elements, such as arsenic, cadmium and lead, are considered toxic, since they accumulate in all plant tissues and are, thus, introduced into the food chain. In this context, the aim of the present study was to determine and compare arsenic, cadmium, lead concentrations in 104 samples of yerba mate (Ilex paraguariensis) marketed, and consumed in three southern Brazilian States, namely Paraná (PR), Santa Catarina (SC) and Rio Grande do Sul (RS). Each element was determined by inductively coupled plasma mass spectrometry (ICP-MS), on a Nexion 300D equipment (Perkin Elmer). As, Cd and Pb concentrations in yerba mate leaves ranged from 0.015 to 0.15mg kg-1, 0.18 to 1.25mg kg-1 and 0.1 to 1.20 mg kg-1, respectively. Regarding Cd, 84% of the samples from RS, 63% from PR and 75% from SC showed higher concentrations than the maximum permissible limit of 0.4 mg kg-1 established by the Brazilian National Sanitary Surveillance Agency (ANVISA), while 7% of the samples from RS and 5% from PR were unsatisfactory for Pb. Concentrations were below the established ANVISA limit of 0.6mg kg-1 for all samples.

TSC1 enables plastid development under dark conditions, contributing to rice adaptation to transplantation shock

Date: 2017-12-06

Authors: Shi, X;Chen, S;Peng, Y;Wang, Y;Chen, J;Hu, Z;Wang, B;Li, A;Chao, D;Li, Y;Teng, S;
Journal: J Integr Plant Biol
Volume:   -  Pages:
DOI: 10.1111/jipb.12621

Since its domestication from wild rice thousands of years ago, rice has been cultivated largely through transplantation. During transplantation from the nursery to the paddy field, rice seedlings experience transplantation shock which affects their physiology and production. However, the mechanisms underlying transplantation shock and rice adaptation to this shock are largely unknown. Here, we isolated a transplant-sensitive chloroplast-deficient (tsc1) rice mutant that produces albino leaves after transplantation. Blocking light from reaching the juvenile leaves and leaf primordia caused chloroplast deficiencies in transplanted tsc1 seedlings. TSC1 encodes a noncanonical ATP-binding cassette (ABC) transporter homologous to AtNAP14 and of cyanobacterial origin. We found that TSC1 controls plastid development in rice under dark conditions, and functions independently of light signaling. However, light rescued the tsc1 mutant phenotype in a spectrum-independent manner. TSC1 was upregulated following transplantation, and modulated the iron and copper levels, thereby regulating prolamellar body formation during the early P4 stage of leaf development. Therefore, TSC1 is indispensable for plastid development in the absence of light, and contributes to adaptation to transplantation shock. Our study provides insight into the regulation of plastid development and establishes a framework for improving recovery from transplantation shock in rice.

The distribution of dissolved and particulate Mo and V along the U.S. GEOTRACES East Pacific Zonal Transect (GP16): The roles of oxides and biogenic particles in their distributions in the oxygen deficient zone and the hydrothermal plume

Date: 2017-12-06

Authors: Ho, P;Lee, J;Heller, MI;Lam, PJ;Shiller, AM;
Journal: Marine Chemistry
Volume:   -  Pages:
DOI: 10.1016/j.marchem.2017.12.003

Molybdenum and vanadium are under-studied elements in the ocean due to their largely conservative natures. Thus, no detailed ocean sections of these elements exist although previous reports do suggest possible anomalies in their distributions due to biological, redox, or sorptive processes. Here we present the first detailed ocean sections of dissolved and particulate Mo and V, obtained as part of the 2013 US GEOTRACES East Pacific Zonal Transect (GP16) from Peru to Tahiti. Similar to previous work, the distribution of dissolved Mo was largely conservative, while dissolved V showed a ~ 5% depletion in the upper waters. For dissolved Mo, a small number of samples showed significantly depleted concentrations which, in most cases, gradually increased with time after samples were acidified. This implies the original sample had experienced a partial change in speciation of dissolved Mo from the predominant molybdate to another, as yet, unknown form. In the oxygen deficient zone (ODZ) off the Peru margin, depleted dissolved Mo and V in a few samples corresponded with the nitrite maximum, suggesting the possible involvement of both elements in the nitrogen cycle. Particulate Mo and V enrichments in the ODZ are likely indicative of scavenging by Fe oxyhydroxides and/or biogenic particles. In near surface waters close to the Peru margin, dissolved Mo and V concentrations slightly decreased with increasing total chlorophyll a, suggesting the removal of both elements by biological uptake and/or adsorption onto biogenic particles. In contrast to previous reports that removal to reducing coastal/estuarine sediments resulted in surface water depletion of dissolved V, there is no evidence from the EPZT section that this process plays a strong role in the development of the ~ 5% dissolved V depletion in the surface ocean. Additionally, dissolved V and Mo depletions were seen in some hydrothermal plume waters above the ridge crest, likely due to adsorption onto Fe/Mn oxides and suggesting that these plume waters are a net sink for these two elements. Associations of ridge crest particulate Mo and V with the particulate Mn and Fe carrier phases suggests V was largely scavenged by Fe oxyhydroxides while Mo was likely scavenged by both Fe oxyhydroxides and Mn oxides. Away from the ridge crest, depletions of dissolved V and Mo are seen along the boundaries of the far field hydrothermal plume, though the reasons for this remain obscure. Future studies of these elements could benefit from determination of speciation as well as increased focus on margin areas.

Chemical extraction of rare earth elements from coal ash

Date: 2017-12-06

Authors: Peiravi, M;Ackah, L;Guru, R;Mohanty, M;Li, J;Xu, B;Zhu, X;Chen, L;
Journal: Minerals & Metallurgical Processing
Volume: 34  -  Pages: 170-177
DOI: 10.19150/mmp.7856

The overall goal of this study is to develop a suitable flow sheet to extract rare earth elements (REEs) from coal ash. A total of 14 coal samples of different ranks were examined for REE concentration, and an anthracite coal sample with the highest REE concentration of more than 700 ppm in the coal ash was selected for REE extraction tests. This paper reports on the results of the experimental program completed in the first part of the study, which included hightemperature leaching with nitric acid followed by solvent extraction tests using various organic extractants, namely, tributyl phosphate, Cyanex 572, di-(2-ethylhexyl)phosphoric acid (D2EHPA) and their combinations. A 4x2x2 experimental design was used to conduct a total of 32 high-temperature leaching tests by varying acid molarity at four levels, solids content at two levels and leaching time at two levels. The highest recovery rates of 90 percent for light rare earth elements (LREEs) and 94 percent for heavy rare earth elements (HREEs) were obtained from the optimum leaching test conditions while maintaining impurity recovery to the leachate at less than 40 percent. D2EHPA was found to be the best extractant in this solvent extraction test series, providing an REE recovery rate of nearly 99 percent.

Metabolism and disposition of arsenic species from controlled oral dosing with sodium arsenite in adult female CD-1 mice. I. Pilot study to determine dosing, analytical measurements, and sampling strategies

Date: 2017-12-05

Authors: Twaddle, NC;Vanlandingham, M;Churchwell, MI;Doerge, DR;
Journal: Food Chem. Toxicol.
Volume: 111  -  Pages: 482-493
DOI: 10.1016/j.fct.2017.12.005

Arsenic (As) is ubiquitous in the earth's crust, with typical dietary intake in developed countries <1 µg/kg bw/d, and atypical groundwater exposures in developing countries approaching 50 µg/kg bw/d. Arsenic exposures are linked with human diseases and doses of toxicological concern are similar to typical dietary intake estimates. The methylation of arsenite by arsenite-3-methyltransferase (As3MT) promotes the clearance of arsenic as pentavalent species, but also generates reactive trivalent intermediates. This study measured inorganic arsenic and its metabolites in pentavalent and trivalent states in blood, tissues, and excreta after oral administration of arsenite (50-200 µg/kg bw). While liver was a major site for clearance of arsenite and formation of methylated species, it also had extensive binding of trivalent intermediates; however, thiol exchange and oxidation reactions of trivalent arsenic were facile since dimethylarsinic acid (DMAV) was the predominant species in blood and urine. Consistent evidence was observed for a non-linear relationship between doses above 50 µg/kg bw and levels of bound trivalent As metabolites. The abundance of protein-bound trivalent arsenic within target tissues should correlate with disruption of critical cellular processes, which rely on defined interactions of thiol functional groups, and could provide dose-response relationships from animal models for human risk assessment.


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