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Summary El Tatio geothermal field is the principal natural source of arsenic for the Loa River, the main surface water resource in the hyper-arid Atacama Desert (Antofagasta Region, Northern Chile). Prior investigations by bulk X-ray absorption spectroscopy have identified hydrous ferric oxides as the principal arsenic-containing phase in sinter material from El Tatio, suggesting sorption as the main mechanism for arsenic scavenging by the solid phases of these hot spring environments. Here we examine siliceous sinter material sampled from a hydrothermal channel using synchrotron based X-ray micro-probe techniques, including As and Fe Kα X-ray fluorescence (μ-XRF), As K-edge X-ray absorption near edge structure (μ-XANES), and X-ray diffraction (μ-XRD). Least-squares linear fitting of μ-XANES spectra shows that arsenic is predominantly present as arsenate sorbed on hydrous ferric oxides (63% molar proportion), but we also identify nodular arsenide micro-mineralizations (37% molar proportion) similar to loellingite (FeAs 2 ), not previously detected during bulk-scale analysis of the sinter material. Presence of arsenide mineralizations indicates development of anoxic environments on the surface of the siliceous sinter, and suggests a more complex biogeochemistry for arsenic than previously observed for circum-neutral pH brine hot spring environments.

An interlaboratory comparison of acid-volatile sulfide (AVS) and simultaneously extracted nickel (SEM_Ni) measurements of sediments was conducted among five independent laboratories. Relative standard deviations for the seven test samples ranged from 5.6 to 71% (mean = 25%) for AVS and from 5.5 to 15% (mean = 10%) for SEM_Ni. These results are in stark contrast to a recently published study that indicated AVS and SEM analyses were highly variable among laboratories. Environ. Toxicol. Chem. 2011; 30:1306–1309. © 2011 SETAC

Submitted by Guilherme Lemeszenski (guilherme@nead.unesp.br) on 2013-08-22T18:48:40Z No. of bitstreams: 1 S0100-40422007000500028.pdf: 374745 bytes, checksum: a9063a55f3da9cef21ac1cf2089e14a1 (MD5) Made available in DSpace on 2013-08-22T18:48:40Z (GMT). No. of bitstreams: 1 S0100-40422007000500028.pdf: 374745 bytes, checksum: a9063a55f3da9cef21ac1cf2089e14a1 (MD5) Previous issue date: 2007-10-01 Made available in DSpace on 2013-09-30T19:38:41Z (GMT). No. of bitstreams: 2 S0100-40422007000500028.pdf: 374745 bytes, checksum: a9063a55f3da9cef21ac1cf2089e14a1 (MD5) S0100-40422007000500028.pdf.txt: 23611 bytes, checksum: 5443ea391531e33f28162a5b020d6105 (MD5) Previous issue date: 2007-10-01 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T15:10:23Z No. of bitstreams: 2 S0100-40422007000500028.pdf: 374745 bytes, checksum: a9063a55f3da9cef21ac1cf2089e14a1 (MD5) S0100-40422007000500028.pdf.txt: 23611 bytes, checksum: 5443ea391531e33f28162a5b020d6105 (MD5) Made available in DSpace on 2014-05-20T15:10:23Z (GMT). No. of bitstreams: 2 S0100-40422007000500028.pdf: 374745 bytes, checksum: a9063a55f3da9cef21ac1cf2089e14a1 (MD5) S0100-40422007000500028.pdf.txt: 23611 bytes, checksum: 5443ea391531e33f28162a5b020d6105 (MD5) Previous issue date: 2007-10-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Characteriza of the inclusion complex ropivacaine: β-cyclodextrin. Ropivacaine (RVC) is a widely used local anesthetic. The complexation of RVC with β-cyclodextrin (β-CD) is of great interest for the development of more efficient local anesthetic formulations. The present work focuses on the characterization of the RVC:β-CD complex by nuclear magnetic resonance (NMR). The stoichiometry of the complex is 1:2 RVC:β-CD. DOSY-NMR shows that the association constant is 55.5 M-1. Longitudinal relaxation time results show that RVC changes its mobility in the presence of β-CD. This study is focused on the physicochemical characterization of inclusion complexes that are potentials options for pain treatment. Universidade Estadual Paulista Júlio de Mesquita Filho Departamento de Engenharia Ambiental Universidade de Sorocaba Universidade Estadual de Campinas Instituto de Biologia Departamento de Bioquímica Universidade de Parma Departamento de Medicina Experimental Universidade Estadual Paulista Júlio de Mesquita Filho Departamento de Engenharia Ambiental

X-ray absorption spectroscopy is often used for assessing the chemical speciation of metals in complex environmental matrices. The approach consists of performing spectral decompositions that rely on the selection of a suite of reference spectra representing the various coordination environments of the metal in the sample. From an experimental perspective, the quality of the data collected (that is the level of noise compared to the number of counts from the selected element) plays an important role in assessing the confidence of the speciation results. We present a method for the selection of an appropriate set of reference spectra based on the quantitative assessment of their interdependency. This method is illustrated in the case of the selection of reference spectra for performing nickel speciation.

The color darkening of selected brushstrokes of the masterpiece A Sunday on La Grande Jatte – 1884 (by Georges Seurat) has been attributed to the alteration of the chromate pigment zinc yellow. The pigment originally displays a bright greenish-yellow color but may undergo, after aging, darkening to a dull, ocher tone. We used XANES to probe the oxidation state of Cr on paint reconstructions, and show that color changes are associated with the reduction of Cr(VI) to Cr(III). Paint mixtures containing the pigment and linseed oil to mimic mixtures used in La Grande Jatte were subjected to artificial aging in the presence of light, SO2, and variable air humidity—50 and 90% relative humidity. High relative humidity led to the largest degree of Cr(VI) reduction whereas low relative humidity promoted light-induced alterations. These results are corroborated by visible reflectance measurements on the same laboratory samples and contribute to a better understanding of the chemical reactivity of chromate pigments, which are present in many historical works of art.