Monitoring of metal phytofiltration performance by micro-XRF methodology.

In this work, micro-XRF was considered as a possible technique for monitoring the rate of incorporation of Cu and Zn into aquatic plants of a laboratory-scale phytofiltration system. This system employed Salvinia biloba Raddi under controlled conditions of light and nutrients. This aquatic plant is being considered as an efficient hyperaccumulator of Cu and Zn and is widely spread in South American lakes and rivers. One set of plants was exposed to 40 ppm w/w of Cu and another to 40 ppm w/w of Zn. The analytical procedure was based on the periodic in vivo quantitative analysis of Cu and Zn at selected points in the plants using micro-XRF. The accuracy of this quantification was effectively improved with the assistance of the Monte Carlo XMI-MSIM simulation code. In order to establish the input parameters of this software, careful measurements of the experimental parameters necessary for the correct modeling of the micro-XRF spectrometer were performed. After that, specially manufactured standards made of tissue equivalent material were employed to validate the configuration of the simulation code and input parameters. It was fulfilled by the comparison of measured and simulated micro-XRF spectra of these standards. Once the configuration code and input parameters were verified, two strategies were considered for the application of Monte Carlo simulation for elemental quantification in plants: an iterative process and inverse method established with external virtual standards. Benefits and drawbacks of both approaches to improve the monitoring of phytofiltration systems were carefully discussed.

Analysis of occurrence, bioaccumulation and molecular targets of arsenic and other selected volcanic elements in Argentinean Patagonia and Antarctic ecosystems.

In Latin America, the high proportion of arsenic (As) in many groundwaters and phreatic aquifers is related to the volcanism of the Andean Range. Nevertheless, there is still very little published research on As and other elements occurrence, and/or transference to biota in Southern regions such as Argentinean Patagonia and the South Shetland Islands in Antarctica, where there are active volcanoes and geothermal processes. Therefore, this study was aimed to describe water quality from the main rivers of Argentinean Northern Patagonia through physicochemical analysis. The Patagonian and Antarctic biota (including samples of animal, plants, algae and bacteria) was characterized through the analysis of their As and other elemental concentrations (P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Se, Br, Rb and Sr), by synchrotron radiation x-ray fluorescence spectroscopy (SRXRF). Finally, the analysis of metal and As-proteins associations in As-accumulating organisms was performed by SRXRF after sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). A wide range of metal concentration including As (up to 950 µg/L As) was found in water samples from Patagonian rivers. A hierarchical cluster analysis revealed that the elemental concentration of analysed biological samples was related to volcanic environments and their place in the trophic chain. Moreover, the results suggest that Se, Co, Cu, Br, and Cl are strong predictors of As in biota. On the other hand, As was not detected in proteins from the studied samples, suggesting biotransformation into soluble As-organic compounds. This is the first study to describe environmental pollution as a consequence of active volcanism, and its influence on water quality and elemental composition of biota in Argentinean Northern Patagonia and Antarctica.

Comprehensive analysis of renal arsenic accumulation using images based on X-ray fluorescence at the tissue, cellular, and subcellular levels.

Exposure to arsenic (As) through drinking water results in accumulation of As and its methylated metabolites in several organs, promoting adverse health effects, particularly potential development of cancer. Arsenic toxicity is a serious global health concern since over 200 million people are chronically exposed worldwide. Abundant biochemical and epidemiological evidence indicates that the kidney is an important site of uptake and accumulation of As, and mitochondrial damage plays a crucial role in arsenic toxicity. However, non-destructive analyses and in situ images revealing As fate in renal cells and tissue are scarce or almost non-existent. In this work, kidney tissue from exposed rats was analyzed by EDXRF (Energy dispersive X-ray fluorescence), micro-SRXRF (micro X-ray Fluorescence using Synchrotron Radiation), SRTXRF (SRXRF in total reflection condition), SEM-EDX (Scanning Electron Microscope in combination with EDXRF) and SRXRF-XANES (SRXRF in combination with X-ray Absorption Near Edge Spectroscopy). Our results provide evidence of renal cortex distribution of As with periglomerular localization, co-localization of S, Cu and As in subcellular compartment of proximal tubule cells, mono-methylarsonous acid accumulation in renal cortex mitochondria, and altered subcellular concentration and distribution of other elements.

Effect of the Aqueous Extract of Lantana grisebachii Stuck Against Bioaccumulated Arsenic-Induced Oxidative and Lipid Dysfunction in Rat Splenocytes.

Arsenic (As) is a worldwide immunotoxic agent that is in contaminated waters and consumed by mammals. Phytotherapy may counteract its harmful effects. Lantana grisebachii Stuck (LG, Verbenaceae) and its extract are proposed as protective, given vvits in vitro bioactivity. The aim was to determine the protective capacity of the aqueous LG extract on splenocytes exposed in vivo to arsenic. Splenocytes were obtained from an arsenicosis model (Wistar rats consuming orally 0 [control; C] or 5 mg/Kg/d of As) that received 0-100 mg/Kg/d of LG extract for 30 days. As content (total reflection X-ray fluorescence), fatty acid profile (gas chromatography), γ-glutamyl transpeptidase activity (Szasz method), peroxides (xylenol orange-based assay), and nitrites (Griess reaction) were then assayed in viable splenocytes. Data were analyzed with ANOVA and the Tukey's test (p < .05). It was observed that the splenocytes contained 2.2 mg/Kg of this elemental arsenic. With γ-glutamyl transpeptidase inhibition and consequent triggering of hydroperoxides (p < .05), it was observed to increase saturated fatty acids and alter lipid profiles. LG treatment avoided damaging effects with values similar to unexposed C (p < .05), and cellular arsenic concentration (p < .0001). In conclusion, the aqueous extract of L. grisebachii counteracted arsenic toxicity in rat splenocytes by preventing its cellular accumulation and induction of lipid and redox disturbances, which may impair immune function.

Immunotoxicological effects of arsenic bioaccumulation on spatial metallomics and cellular enzyme response in the spleen of male Wistar rats after oral intake.

Arsenic (As) is a worldwide environmental contaminant, which compromises immunity and causes various associated disorders. To further investigate its immunotoxicity, male Wistar rats were exposed to 100ppm of sodium arsenite (inorganic AsIII) in drinking water for 2 months. Given that metals are significant immune regulators, their content and distribution were analysed in spleen tissues, to then evaluate subsequent changes of redox enzyme responses in spleen parenchyma cells (splenocytes). X-ray fluorescence spectrometry demonstrated As accumulation in both white and red pulps (p<0.005), and As-related pulp-dependent modifications of the content of Cu, Ca, Zn and Fe (p<0.01). Correlational path analysis revealed direct effects of As on their spatial distribution (Cu: -0.76, Ca: -0.61, Zn: 0.38; p<0.02). As-exposed splenocytes showed ɣ-glutamyltranspeptidase inhibition, peroxidase induction, and variable responses of nitric oxide synthase (p<0.05). Concanavalin A-treated splenocytes (T cell mitogen) were more susceptible in vitro to these As-related enzymatic changes than those treated with lipopolysaccharide (B cell mitogen) (p<0.05). The study thus established the impact of As bioaccumulation on metallic spatial homeostasis in the spleen, and then identified enzymatic dysfunctions in splenocytes. This suggested that arsenic disrupts biometal-dependent immune pathways and redox homeostasis, with mitogen exposure modifying the toxicological response.

Depth profiling nano-analysis of chemical environments using resonant Raman spectroscopy at grazing incidence conditions.

Both X-ray total reflection and X-ray Raman scattering techniques were combined to discriminate chemical environments in depth-profiling studies using an energy dispersive system. This allowed, for the first time, to resolve oxidation state on surface nanolayers with a low-resolution system. Samples of pure Cu and Fe oxidized in tap water and salty water, respectively, were studied in the Brazilian synchrotron facility using monochromatic radiation and an EDS setup. The measurements were carried out in total reflection geometry with incident energy lower and close to the K absorption edge of both elements. The results allowed observing the presence of very thin oxide layers, usually not observable with conventional geometries of irradiation. They also permit the identification of the compound present in a particular depth of the sample with nanometric, or even subnanometric, resolution using a low-resolution system.

Association between As and Cu renal cortex accumulation and physiological and histological alterations after chronic arsenic intake.

Arsenic (As) is one of the most abundant hazards in the environment and it is a human carcinogen. Related to excretory functions, the kidneys in humans, animal models or naturally exposed fauna, are target organs for As accumulation and deleterious effects. Previous studies carried out using X-ray fluorescence spectrometry by synchrotron radiation (SR-microXRF) showed a high concentration of As in the renal cortex of chronically exposed rats, suggesting that this is a suitable model for studies on renal As accumulation. This accumulation was accompanied by a significant increase in copper (Cu) concentration. The present study focused on the localization of these elements in the renal cortex and their correlation with physiological and histological As-related renal effects. Experiments were performed on nine male Wistar rats, divided into three experimental groups. Two groups received 100 microg/ml sodium arsenite in drinking water for 60 and 120 consecutive days, respectively. The control group received water without sodium arsenite (< 50 ppb As). For histological analysis, 5-mum-thick sections of kidneys were stained with hematoxylin and eosin. Biochemical analyses were used to determine concentrations of plasma urea and creatinine. The As and Cu mapping were carried out by SR-microXRF using a collimated white synchrotron spectrum (300 microm x 300 microm) on kidney slices (2 mm thick) showing As and Cu co-distribution in the renal cortex. Then, renal cortical slices (100 microm thick) were scanned with a focused white synchrotron spectrum (30 microm x 30 microm). Peri-glomerular accumulation of As and Cu at 60 and 120 days was found. The effects of 60 days of arsenic consumption were seen in a decreased Bowman's space as well as a decreased plasma blood urea nitrogen (BUN)/creatinine ratio. Major deleterious effects; however, were seen on tubules at 120 days of exposition. This study supports the hypothesis that tubular accumulation of As-Cu may have some bearing on the arsenic-associated nephrotoxicological process.