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Chemical speciation

Xiao-Zhang Yu, Qin-Long Ling, Yan-Hong Li, Yu-Juan Lin
Transcriptional changes of genes encoded with phytochelatins synthase (PCS) was investigated in rice seedlings exposed to potassium chromate Cr(VI) or chromium nitrate Cr(III) using qRT-PCR. Our study demonstrates that both Cr variants initiated different responses of phytochelatin content and PCS activities in rice tissues. Six putative PCS genes were expressed differentially in response to both Cr species. Comparing gene expression between root/shoots, only LOC_Os05g34290.1 and LOC_Os06g01260.1 genes were expressed in similar patterns in Cr(VI) treatment, while none of them were expressed equally in Cr(III) treatments...
May 21, 2018: Bulletin of Environmental Contamination and Toxicology
William Holden, Gerald T Seidler, Singfoong Cheah
The analytical chemistry of sulfur-containing materials poses substantial technical challenges, especially due to the limitations of 33S NMR and the time-intensive preparations required for wet-chemistry analyses. A number of prior studies have found that synchrotron-based x-ray absorption near edge structure (XANES) measurements can give detailed speciation of sulfur chemistry in such cases. However, due to the obvious access limitations, synchrotron XANES of sulfur cannot be part of routine analytical practice across the chemical sciences community...
May 21, 2018: Journal of Physical Chemistry. A
Agnese Carino, Christian Ludwig, Antonio Cervellino, Elisabeth Müller, Andrea Testino
The experimental data on calcium phosphates formation were collected in dilute solution at constant pH (7.40) and temperature (37.0 °C) at different levels of ionic strength (IS). The evolution of the solid phase formation is described in detail using a thermodynamic-kinetic model. The thermodynamic model takes into account all relevant chemical species as well as Posner's clusters; the kinetic model, based on the discretized population balance approach, accounts for the solid formation from solution. The experimental data are consistent with an initial formation of dicalcium phosphate dihydrate (DCPD, brushite), which dominates the nucleation rate, and its rapid transformation into octacalcium phosphate (OCP) or hydroxyapatite (HA), which dominates the growth rate...
May 17, 2018: Acta Biomaterialia
Prasanna Kumarathilaka, Saman Seneweera, Andrew Meharg, Jochen Bundschuh
Rice is the main staple carbohydrate source for billions of people worldwide. Natural geogenic and anthropogenic sources has led to high arsenic (As) concentrations in rice grains. This is because As is highly bioavailable to rice roots under conditions in which rice is cultivated. A multifaceted and interdisciplinary understanding, both of short-term and long-term effects, are required to identify spatial and temporal changes in As contamination levels in paddy soil-water systems. During flooding, soil pore waters are elevated in inorganic As compared to dryland cultivation systems, as anaerobism results in poorly mobile As(V), being reduced to highly mobile As(III)...
April 21, 2018: Water Research
Tyler Sowers, Dinesh Adhikari, Jian Wang, Yu Yang, Donald L Sparks
Organo-mineral associations of organic carbon (OC) with iron (Fe) oxides play a major role in environmental OC sequestration, a process crucial to mitigating climate change. Calcium has been found to have high co-association with OC in soils containing high Fe content, increase OC sorption extent to poorly-crystalline Fe oxides, and has long been suspected to form bridging complexes with Fe and OC. Due to the growing realization that Ca may be an important component of C cycling, we launched a scanning transmission X-ray microscopy (STXM) investigation, paired with near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, in order to spatially resolve Fe, Ca, and OC relationships and probe the effect of Ca on sorbed OC speciation...
May 17, 2018: Environmental Science & Technology
Isabelle Rohn, Talke Anu Marschall, Nina Kroepfl, Kenneth Bendix Jensen, Michael Aschner, Simon Tuck, Doris Kuehnelt, Tanja Schwerdtle, Julia Bornhorst
The essential micronutrient selenium (Se) is required for various systemic functions, but its beneficial range is narrow and overexposure may result in adverse health effects. Additionally, the chemical form of the ingested selenium contributes crucially to its health effects. While small Se species play a major role in Se metabolism, their toxicological effects, bioavailability and metabolic transformations following elevated uptake are poorly understood. Utilizing the tractable invertebrate Caenorhabditis elegans allowed for an alternative approach to study species-specific characteristics of organic and inorganic Se forms in vivo, revealing remarkable species-dependent differences in the toxicity and bioavailability of selenite, selenomethionine (SeMet) and Se-methylselenocysteine (MeSeCys)...
May 17, 2018: Metallomics: Integrated Biometal Science
Nicholas Gysel, Poornima Dixit, Debra A Schmitz, Guenter Engling, Arthur K Cho, David R Cocker, Georgios Karavalakis
We assessed the chemical properties and oxidative stress of particulate matter (PM) emissions from underfired charbroiled meat operations with and without the use of aftertreatment control technologies. Cooking emissions concentrations showed a strong dependence on the control technology utilized, with all emission rates showing decreases with the control technologies compared to the baseline testing. The organic acids profile was dominated by the saturated nonanoic, myristic, palmitic, and stearic acids, and the unsaturated oleic, elaidic, and palmitoleic acids...
August 15, 2018: Science of the Total Environment
Peter F DeCarlo, Anita M Avery, Michael S Waring
Aerosol composition measurements made in an indoor classroom indicate the uptake of thirdhand smoke (THS) species to indoor particles, a novel exposure route for THS to humans indoors. Chemical speciation of the organic aerosol fraction using mass spectrometric data and factor analysis identified a reduced nitrogen component, predominantly found in the indoor environment, contributing 29% of the indoor submicron aerosol mass. We identify this factor as THS compounds partitioning from interior surfaces to gas phase and then aerosol phase...
May 2018: Science Advances
Gautier Landrot, Saengdao Khaokaew
Lead (Pb) stabilization in polluted soils treated by a Pb immobilization technique may be dependent on the speciation of Pb present in specific particle-size fractions of the soil. However, the scale-dependency of Pb speciation in contaminated soils is still not clearly understood. In this study, the natures and amounts of Pb chemical forms were determined in five Pb-polluted soil samples from Klity Village, Thailand, and their particle-size fractions. This was achieved using multiple analytical tools, including bulk Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy at the Pb LIII edge...
May 11, 2018: Environmental Science & Technology
Scott Hume, François Caron, Stefan Siemann
Aqueous natural organic matter (NOM) contains different types of functional groups (carboxylic, phenolic, sulfidic, etc.), and hence could change the speciation of metals in environmental systems. This work is a proof-of-concept study on the interaction of three metals (Cu, Co, and Cs) with NOM using fluorescence spectroscopy. The specific aim was to determine the conditional stability constants for these three metals with NOM optical components, obtained from the quenching of fluorescence signals. Three contrasting water types were sampled in Northern Ontario: a pristine source (Cross Rd...
May 10, 2018: Environmental Science and Pollution Research International
A Masalaite, R Holzinger, D Ceburnis, V Remeikis, V Ulevičius, T Röckmann, U Dusek
Size-segregated aerosol particles were collected during winter sampling campaigns at a coastal (55°37' N, 21°03'E) and an urban (54°64' N, 25°18' E) site. Organic compounds were thermally desorbed from the samples at different temperature steps ranging from 100 °C to 350 °C. The organic matter (OM) desorbed at each temperature step is analysed for stable carbon isotopes using an isotope ratio mass spectrometer (IRMS) and for individual organic compounds using a Proton Transfer Reaction Time-of-Flight Mass Spectrometer (PTR-MS)...
May 7, 2018: Environmental Pollution
Indika Herath, Meththika Vithanage, Saman Seneweera, Jochen Bundschuh
Thiolated arsenic compounds are the sulfur analogous substructures of oxo-arsenicals as the arsinoyl (As = O) is substituted by an arsinothioyl (As = S) group. Relatively brief history of thioarsenic research, mostly in the current decade has endeavored to understand their consequences in the natural environment. However, thioarsenic related aspects have by far not attached much research concern on global scale compared to other arsenic species. This review attempts to provide a critical overview for the first time on formation mechanisms of thioarsenicals, their chemistry, speciation and analytical methodologies in order to provide a rational assessment of what is new, what is current, what needs to be known or what should be done in future research...
April 26, 2018: Environment International
Meric Selbes, Wilson Beita-Sandí, Daekyun Kim, Tanju Karanfil
N-nitrosodimethylamine (NDMA), a probable human carcinogen disinfection by-product, has been detected in chloraminated drinking water systems. Understanding its formation over time is important to control NDMA levels in distribution systems. The main objectives of this study were to investigate the role of chloramine species (i.e., monochloramine and dichloramine); and the factors such as pH, sulfate, and natural organic matter (NOM) influencing the formation of NDMA. Five NDMA precursors (i.e., dimethylamine (DMA), trimethylamine (TMA), N,N-dimethylisopropylamine (DMiPA), N,N-dimethylbenzylamine (DMBzA), and ranitidine (RNTD)) were carefully selected based on their chemical structures and exposed to varying ratios of monochloramine and dichloramine...
April 16, 2018: Water Research
Eva Oburger, Carolina Vergara Cid, Julian Preiner, Junjian Hu, Stephan Hann, Wolfgang Wanek, Andreas Richter
Increasing use of tungsten (W) based products opened new pathways of W into environmental systems. Due to its chemical alikeness with molybdenum (Mo), W is expected to behave similarly to its 'twin element' Mo; however, our knowledge of the behaviour of W in the plant-soil environment still remains sketchy. The aim of this study was to investigate plant growth as well as W and nutrient uptake depending on soil chemical properties like soil pH and texture. Soybean (Glycine max cv Primus) was grown on two acidic soils differing in soil texture, that were either kept at their natural soil pH (pH 4...
April 27, 2018: Environmental Science & Technology
P Blanco Rodríguez, J C Lozano, F Vera Tomé, C Prieto, A Medeiros
In order to clarify some of the assumptions and approximations about the use of the distribution coefficient Kd for 226 Ra in soils, a systematic study has been performed using centrifugation to extract the soil solution. The separated fractions of the soil solution have different kinetics with respect to the sorption process in the soil, which may in turn condition the final chemical composition and even the speciation of the radionuclides in solution. In the experimental design of this study three factors were considered: the moisture level in the incubation process, incubation time and the speed of centrifugation...
April 17, 2018: Chemosphere
James Everett, Joanna F Collingwood, Vindy Tjendana-Tjhin, Jake Brooks, Frederik Lermyte, Germán Plascencia-Villa, Ian Hands-Portman, Jon Dobson, George Perry, Neil D Telling
Altered metabolism of biometals in the brain is a key feature of Alzheimer's disease, and biometal interactions with amyloid-β are linked to amyloid plaque formation. Iron-rich aggregates, including evidence for the mixed-valence iron oxide magnetite, are associated with amyloid plaques. To test the hypothesis that increased chemical reduction of iron, as observed in vitro in the presence of aggregating amyloid-β, may occur at sites of amyloid plaque formation in the human brain, the nanoscale distribution and physicochemical states of biometals, particularly iron, were characterised in isolated amyloid plaque cores from human Alzheimer's disease cases using synchrotron X-ray spectromicroscopy...
April 24, 2018: Nanoscale
Han Su, Rujun Yang, Yan Li, Xuchen Wang
The influence of humic substances (specifically humic and fulvic acids, referred to as HS-HA and HS-FA) as well as other factors, such as major nutrient concentrations of total dissolved nitrogen (TDN), total dissolved phosphate (TDP) and hydrologic factors, on the distribution of total dissolved iron (DFe) and the chemical speciation of DFe was studied in the East China Sea (ECS) during a summer cruise in 2013. As the wide rage fraction of nature organic matter, the HS-HA, HS-FA in ESC contains most part of the organic ligand (Lt) of DFe...
April 9, 2018: Chemosphere
Leo J D Moreira, Evandro B da Silva, Maurício P F Fontes, Xue Liu, Lena Q Ma
Even though the Amazon region is widely studied, there is still a gap regarding Cr exposure and its risk to human health. The objectives of this study were to 1) determine Cr concentrations in seven chemical fractions and 6 particle sizes in Amazon soils, 2) quantify hexavalent Cr (CrVI) concentrations using an alkaline extraction, 3) determine the oral and lung bioaccessible Cr, and 4) assess Cr exposure risks based on total and bioaccessible Cr in soils. The total Cr in both A (0-20 cm) and B (80-100 cm) horizons was high at 2346 and 1864 mg kg-1 ...
April 16, 2018: Environmental Pollution
P Montoro Leal, E Vereda Alonso, M M López Guerrero, M T Siles Cordero, J M Cano Pavón, A García de Torres
Arsenic, one of the main environmental pollutants and potent natural poison, is a chemical element that is spread throughout the Earth's crust. It is well known that the toxicity of arsenic is highly dependent on its chemical forms. Generally, the inorganic species are more toxic than its organics forms, and As(III) is 60 times more toxic than As(V). In environmental waters, arsenic exists predominantly in two chemical forms: As(III) and As(V). In view of these facts, fast, sensitive, accurate and simple analytical methods for the speciation of inorganic arsenic in environmental waters are required...
July 1, 2018: Talanta
Derek R McLain, Jennifer L Steeb, Nicholas A Smith
The safeguards community currently lacks a method to rapidly determine the chemical form of radioactive and non-radioactive compounds in real time during inspection activities. Chemical speciation identification can provide important information on both the types of materials that are collected during environmental sampling and can inform inspectors as to where to focus efforts during inspections or complementary access visits. Ion Mobility Spectrometry (IMS) is an established field technique for the detection of explosives, narcotics, and other organic compounds...
July 1, 2018: Talanta
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