Cristina Vázquez

Combining TXRF, FT-IR and GC–MS information for identification of inorganic and organic components in black pigments of rock art from Alero Hornillos 2 (Jujuy, Argentina)

AbstractArchaeological samples are complex in composition since they generally comprise a mixture of materials submitted to deterioration factors largely dependent on the environmental conditions. Therefore, the integration of analytical tools such as TXRF, FT-IR and GC–MS can maximize the amount of information provided by the sample. Recently, two black rock art samples of camelid figures at Alero Hornillos 2, an archaeological site located near the town of Susques (Jujuy Province, Argentina), were investigated. TXRF, selected for inorganic information, showed the presence of manganese and iron among other elements, consistent with an iron and manganese oxide as the black pigment. Aiming at the detection of any residual organic compounds, the samples were extracted with a chloroform–methanol mixture and the extracts were analyzed by FT-IR, showing the presence of bands attributable to lipids. Analysis by GC–MS of the carboxylic acid methyl esters prepared from the sample extracts, indicated that the main organic constituents were saturated (C16:0 and C18:0) fatty acids in relative abundance characteristic of degraded animal fat. The presence of minor C15:0 and C17:0 fatty acids and branched-chain iso-C16:0 pointed to a ruminant animal source. FigureRock art painting at Hornillos 2 Cave, Susques, Argentina

Total reflection X-ray fluorescence polymer spectra: classification by taxonomy statistic tools.

The aim of this work is to explore the use of chemometric tools for the classification of synthetic and natural polymers with a mean molecular weight greater than 10(6). Total Reflection X-Ray Fluorescence (TXRF) spectra were obtained and analyzed in order to retrieve matrix information and to illustrate the calibration procedure. The intensities of the coherent and incoherent scattered peaks were specially selected for this purpose. The polymers studied were aqueous solutions of scleroglucan, polyacrilamide, polyoxyethylene oxide, glucomannan, 2,3,6-tri-o-ethylamylose and xhantan, in concentrations upto 1% (m/m). matlab software was used for numerical calculations. Using a combination of principal component analysis and cluster analysis, the differences in composition of various analyzed polymers can be visualized.

Eutrophication decrease: Phosphate adsorption processes in presence of nitrates

Eutrophication causes aquatic environment degradation as well as serious problems for different purposes of water uses. Phosphorus and nitrogen, mainly as phosphate and nitrate respectively, are considered responsible for eutrophication degradation. The focus of this work was the study of adsorption processes for decreasing phosphate and nitrate concentrations in bi-component aqueous systems. Dolomite and hydroxyapatite were selected as low-cost adsorbents. Obtained results showed that both adsorbents have high capacity for phosphate adsorption which the presence of nitrate does not modify. Hydroxyapatite proved to be the most efficient adsorbent, however, it showed a low percentage of desorption and few possibilities of reuse. Dolomite, on the other hand, allows a desorption of the adsorbed material that favours its reuse.

Provenance study of obsidian samples by using portable and conventional X ray fluorescence spectrometers. Performance comparison of both instrumentations

The potentiality of portable instrumentation lies on the possibility of the in situ determinations. Sampling, packaging and transport of samples from the site to the laboratory are avoided and the analysis becomes non destructive at all. However, detection limits for light elements are, in most cases, a limitation for quantification purposes. In this work a comparison between the results obtained with an X ray fluorescence spectrometer laboratory based and a portable instrument is performed. A set of 76 obsidian archaeological specimens from northwest Patagonia, Argentina was used to carry out the study. Samples were collected in the area of the middle and high basin of the Limay River. The analytical information obtained with both instrumentations was complemented with Principal Component Analysis in order to define groups and identify provenance sources. The information from both instruments allows arriving to the same conclusion about sample provenance and mobility of hunter-gatherer groups. Three groups of sources were identified in both cases matching with the geographical information. Also, same sets of outlier samples or not associated to these sources were found. Artifact samples were associated mainly to the closest sources, but some of them are related to sources located more than three hundred kilometers, evidencing the large mobility of the hunter-gatherers by the obsidian interchange. No significant differences between concentrations values obtained by laboratory based instrument and portable one were found.

Low impurities in scleroglucan aqueous systems: Removal processes control by total reflection X-ray fluorescence analysis

ABSTRACT The aim of this work was to use the determination of trace elements by total reflection X-ray fluorescence (TXRF) for the performance study of three final purification methods of polysaccharide systems. TXRF shows two indispensable advantages to accomplish this study: the small quantities of sample required for the analysis and the avoidance of digesting the organic material. Aqueous scleroglucan systems with only impurity traces were studied, from diluted solutions to gels. The most efficient purification process was selected for each range of concentration.

Characterization of trace elements in high viscosity materials by total reflection X-ray spectrometry ☆

Abstract This paper proposes the use of radiation scattered by the sample instead of the internal standard method for quantifying impurities in high viscosity materials using X-ray fluorescence with total reflection geometry. The method has been performed for checking trace elements in gels of polymers. Advantages include no sample preparation and a minimum amount of sample (10 μl). The method is also insensitive to instrumental variations, sample amount and particle size of the sample. The ratio of coherent to incoherent scattering intensities of X-ray was also investigated to estimate the content of C plus O in these polymers.

Compositional study of prehistoric pigments (Carriqueo rock shelter, Argentina) by synchrotron radiation X-ray diffraction

In this work synchrotron radiation X-ray diffraction technique was successfully applied for the analysis of pigments found in excavation at Carriqueo rock shelter, Neuquen, Argentina. The pigment samples of orange, red, and brown shades were collected from different levels of this archaeological site and compared with a suspected source of provenance La Oficina creek. X-ray diffraction patterns of several yellowish, reddish, and red pigments showed the presence of haematite, goethite, kaolinite, and quartz. The majority of Carriqueo collected samples belonged to the same group of the suspected source, having haematite and quartz as main crystalline phases. The results indicate that the raw material from La Oficina is the source of most of the pigments found at Carriqueo. The present work helps us to understand the strategy of supplying raw materials by human groups in the North Patagonia region.

HEMATITA VS. ARCILLAS: SU POTENCIAL COMO PIGMENTOS ROJOS Y SU USO EN TRES SITIOS DE LA PUNA JUJEÑA (ARGENTINA)

El analisis de pinturas rojas en pictografias de tres sitios de la Puna jujena puso de manifiesto el uso exclusivo de hematita en su realizacion. Este pigmento rojo fue utilizado en la region desde inicios de la ocupacion humana y su reiterada presencia en representaciones pictoricas diacronicas revela la especificidad de esa materia prima en Hornillos 2, Cueva Quispe y Tres Pozos. Los pigmentos rojizos recuperados de los niveles estratigraficos en dos de los sitios estan constituidos por hematita y por arcillas rojas. El uso de uno u otro tipo de pigmento estaria relacionado con las propiedades intrinsecas de ambas especies minerales, por tal motivo, planteamos que fueron utilizadas con fines diferentes. Palabras clave: pinturas rupestres, hematita, arcillas rojas, usos, Puna jujena

Use of earthworms (Eisenia fetida) and vermicompost in the processing and safe management of hazardous solid and liquid wastes with high metal contents

Two feasibility studies using the earthworm (Eisenia fetida) and vermicompost in the processing and remediation of solid and liquid wastes with high metal content are presented: vermicompost as adsorbent substrate for remediation of wastewaters contaminated with metals; earthworms for remediation of arsenic (As) and mercury (Hg) in landfill soils. The feasibility of vermicompost for the remediation of nickel (Ni), chromium (Cr), vanadium (V) and lead (Pb) in wastewater is demonstrated. The earthworm (Eisenia fetida) allows the removal of As and Hg from landfill soils with an efficiency of 42-72% in 15 days for As and 7.5-30.2% for Hg.