Search Results
You are looking at 1 - 10 of 10 items for
- Author or Editor: P. Avila-Perez x
- Refine by Access: All Content x
Abstract
José Antonio Alzate
dam mud sediment samples were collected from six sampling sites. The samples were analyzed by combining multielemental studies with structural details, including heating to very high temperatures. Characterization of mud sediment samples have been shown to have low concentrations of metals (Cr, Mn, Ni, Cu, Zn, Pb). No systematic trend was observed as a function of the sampling points.
Abstract
A study was undertaken to determine experimentally the uptake of pollutants into of the different parts of the water hyacinth (Eichhornia crassipes) found in “José Antonio Alzate” dam in the State of México, México. There is evidence for efficient and significant root accumulation of Ti, Mn, Fe, and Ba; but in the upper parts concentrations was consistently determined by the degree of watering. However, a significant input could by derived from a common generic source, such as the atmospheric deposition. The experimental study would, therefore, indicate that water hyacinth species can be highly effective in providing a control and treatment buffer for toxic discharges to the dam.
Abstract
The effects of tobacco on human health have been widely investigated and documented However, there are not too many specific reports on the potential risk associated to the presence of metals in the paper employed for cigarettes fabrication Even more, there is a lack of national and international norms in this respect. Otherwise, in the literature INAA appears as the unique method for wrapping paper analysis. Therefore, without a nuclear reactor available at the National University of Mexico (UNAM), EDXRF was selected with the aim to explore the possibility to apply this method, instead of INAA, to the analysis of wrapping paper assuming this task, at the beginning, as a supplement to a previous research which was recently presented (2005).1 The analytical work was developed on the wrapping paper of eight of the most known marks of cigarettes in Mexico, in two non-destructive stages: a first survey, by the classical technique of energy dispersive X-ray fluorescence (EDXRF), used a 1 11 GB qradiation source of 238Pu and a SiLi detector. In the absence of standard reference materials for cigarette’s paper, the SRM-1832 and 1833 were required for calibration, a fiberglass air filter was used as a secondary standard. The second stage was performed in a spectrometer TX-2000, anode of Mo, quantification software EDXRF32 (fundamental parameters). This paper presents a comparison of the obtained values with those found in the literature. The results show that the EDXRF method, in the Mo tube version, has the adequate precision and detection limits for the analysis of wrapping paper.
Abstract
The S, K, Ca, Ti, V, Cr, Mn, Fe, Cu, Zn and Pb concentration and the elemental composition of particles in suspended matter from principal discharges to Lerma River, have been evaluated. The elemental concentration in suspended matter has been obtained by Energy Dispersive X-Ray Fluorescence Spectrometry. The elemental composition of particles has been obtained by means of Energy Dispersive X-Ray Spectrometry (EDS). The results show that K, Ca, Ti, Mn and Fe are mainly from natural origin in the Upper Course of the Lerma River (UCLR), where the principal contributions probably come from dragging of soils and sediments in the rainy season and Cr, Cu, Zn and Pb are mainly from anthropogenic origin where the principal contributions come from urban and industrial untreated discharge. The application of Energy Dispersive X-Ray Spectrometry plus Scanning Electron Microscopy is useful in the characterization of suspended matter in natural, anthropogenic and mixed water discharges.
Abstract
Trace elements were determined by TXRF in whole blood samples in a randomly non-occupational exposed population living in the Metropolitan Zone of the Mexico Valley (MZMV). Arithmetic and geometric means of S, Ca, Cu, Zn, Rb and Pb concentrations, were on the reported range values for non-occupational population in other countries, while those of K and Br were higher, possibly due to dietary habits and geographical or environmental factors. The noticeable decline in blood lead level (91%) should be positively perceived. As a part of the Quality Control Program, a certified IAEA-A13 was tested.
Abstract
206Pb/207Pb isotope ratios of dry deposit samples in the Metropolitan Zone of Mexico Valley (MZMV) were determined and correlated with some contemporary environmental material such as gasoline, urban dust, etc., as possibile pollution sources, the latter presenting different signatures 206Pb/207Pb ratios were determined in samples “as is” by ICP-MS, using an Elan-6100. A standard material NIST-981 was used to monitor accuracy and to correct mass fractionation. The calculated enrichment factors of lead (taking rubidium as a conservative endogenous element) show its anthropogenic origin with percentages higher than 97.65%. 206Pb/207Pb ratio in dry deposit samples ranges from 0.816 to a maximum of 1.154, following a normal distribution. Arithmetic mean was 0.9967±0.0864 lower than those of possible pollution sources: 1.1395±0.0165 for gasoline, 1.071±0.008 for industrially derived lead and, for the more radiogenic natural soil and urban dust values ranging from 1.2082±0.022 to 1.211±0.108. The possible origin of lead in gasoline used prior to 1960 is discussed.
Abstract
The metal distribution of Cr, Mn, Fe, Cu, Zn, and Pb, and the elemental composition, morphology and relative abundance of particles have been evaluated in suspended matter of the Upper Course of the Lerma River in Mexico. The metal concentrations in the suspended matter decrease in the sequence: Fe > Mn > Zn > Cu = Cr > Pb. The Fe and Mn concentrations in the suspended matter are produced principally by natural contributions whereas the Cu, Zn, Cr, and Pb concentrations are produced principally by anthropogenic contributions. In general, the particle groups decrease in the following sequence: aluminosilicate > silica > sulphur > metals > calcium > manganese > iron > calcium carbonate.
Abstract
An analytical exercise between two laboratories was performed in order to compare the elemental composition of a water sample. The metal concentration of Cr, Cu, Fe, Mn, Ni, Pb, and Zn in the water sample was analyzed by Total Reflection X-Ray Fluorescence and Atomic Absorption Spectrometry. The analysis by Total Reflection X-Ray Spectrometry was realized by an Ital Structures TX-2000 and the analysis by Atomic Absorption Spectrometry was made by a Perkin Elmer Spectrophotometer Model 3110. Results show a good agreement in the metal concentrations obtained by both techniques. The variation coefficient between the results with both techniques was less than 14%. Therefore, it is possible to conclude that both techniques are reliable and adequate for the determination of these elements in environmental water samples.
Summary
The Lerma is one of the most important rivers of Mexico, where it drains highly populated and industrialized regions. The concentration of six major and trace elements: titanium, manganese, iron, zinc, copper and lead in the surface sediments of the upper course of Lerma river was investigated, in order to identify its distribution along the river and to recognize the principal sites of pollution. The surface sediment samples were collected at 8 sites distributed following the stream flow direction of the river. Major and trace elements concentrations were determined by energy dispersive X-ray spectrometry. The results show that the metal concentrations in the sediments decrease in the sequence: Fe > Ti > Mn > Zn > Cu > Pb. Concentration of Fe, Mn and Ti were significantly higher than the other metals in site 8,200 meters downstream the Alzate Dam. The high concentrations and spatial variations of Zn, Cu and Pb in the middle sites of the upper course of the Lerma River indicate that the river pollution is probably associated with urban and industrial discharges.
Abstract
Samples of total suspended particles (TSP) and PM10 respirable particles from five monitoring stations from the network system of the Metropolitan Zone of the Valley of Mexico (MZVM) were analyzed by scanning electron microscopy (SEM) and energy-dispersive X-ray microanalysis (EDX). Morphology and chemical composition allowed to identify six groups. The analysis shows that the most abundant groups are Al-Si-O, Fe, and metals, the first one in the TSP fraction. Trace metal, commonly associated to PM10 at a receptor location, will depend on the relative influences of local anthropogenic sources. Metal group was observed in all samples, mainly in Tlalnepantla and CES zones (28–46%).
