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Arsenic speciation in environmental matrices represents a great challenge for developing countries, requiring the use of easily accessible analytical techniques. Speciation is required, since As (III) compounds can be up to 10 times more toxic than As (V) compounds. In the present work the experimental conditions for the quantification by speciation of As (V) and As (III) and phosphates in waters are based, using the spectrophotometric method of ascorbic acid. In this sense, the method was verified, evaluating the parameters of linear performance, precision, detection limit and quantification, verifying that are adequate for the determinations of these analytes. The proposed method was also used for the quantification of As (V) and As (III) in wastewater from a gold extraction [ABSTRACT FROM AUTHOR]

The goals of this work were: i) to identify and quantify the potentially toxic heavy metals and metalloids in sewage sludge generated by "Taxco de Alarcón" wastewater treatment plant; ii) to determine the potentially toxic heavy metals and metalloids speciation through sequential chemical extraction, and iii) to provide a detailed methodological procedure for total digestion and sequential chemical extraction to sewage sludge. The methodology was a total digestion and sequential chemical extraction using sewage sludge. Analysis of potentially toxic heavy metals and metalloids was performed by inductively coupled plasma atomic emission spectroscopy. From total digestion Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Ni, Pb, Sr, V, and Zn were identified and quantified. Seven potentially toxic heavy metals and metalloids analyzed and considered by NOM-004-SEMARNAT-2002 were found in sewage sludge at the following concentrations: 51, 50, 38, 752, 153, 190, and 3,134 mg/kg (dry basis), for As, Cd, Cr, Cu, Pb, Ni, and Zn, respectively. However, the concentration of As, Cd, and Zn exceeds the maximum allowable limit set by the standard to be classified as excellent quality sludge. On the other hand, the analysis of the different fractions obtained by sequential chemical extraction exhibited that the highest concentrations of As, Cd, and Zn are mainly associated with the most geo-available fractions (exchangeable fraction and bound to carbonates). The total concentrations in these fractions were 34, 34, and 1,723 sewage sludge mg/kg (dry basis) for As, Cd, and Zn, respectively. Finally, in function of the seven potentially toxic heavy metals and metalloids analyzed as well as their total concentrations determined in the sewage sludge from the Taxco de Alarcón wastewater treatment plant, the sewage sludge are classified as a good quality sludge. In other words, the sewage sludge have the potential to be used for urban handling without direct contact during its application in forest use or as agricultural soil improvers in the region. [ABSTRACT FROM AUTHOR]

An ontological approach on the species reality is made by exploring different philosophical and scientific stances. Based on the premise that the species concept is intimately tied to the speciation process, the Darwinian and Synthetic Theory, that posit gradual and constant evolutionary change rates, were confront with the Punctuated Equilibrium hypotheses, that states long evolutionary stasis periods punctuated by very short, in geological times, speciation processes. By analyzing Systems Ontology and choosing Inference to the Best Explanation, we can consider species as self-organized natural systems, which can explain the observed phenomena in a more parsimonious way, as well as allowing us to predict, from Scientific Realism, how the speciation process can occur, following the General Systems Theory properties and characteristics. Moreover, the Species Problem can be advanced if considered within the Systems approach. [ABSTRACT FROM AUTHOR]

In this work, different species of arsenic as arsenic (III), arsenic (V), dimethyl arsenic acid (DMA) and monomethyl arsenic acid (MMA) in the bioavailable fraction of arsenic in the sediments of the Bay of Matanzas, Cuba, were identified for the first time. A sequential extraction, in three stages, using as extractants water, buffer phosphate 25 mmol/l (pH 6,8) and HCL (1 mol . L-1), respectively, were used. By the combination High Performance Liquid Chromatography (HPLC) - Hydride Generation (HG) - Atomic Fluorescence Spectroscopy (AFS) the presence of arsenic (V) was detected in the aqueous extract of one of the studied sediments, while in the extracts with buffer phosphate the presence of DMA and arsenic (V) were proved. The content of bioavailable arsenic in the samples, that was determined through Hydride Generation- Atomic Absorption Spectrometry (HG-AAS), varied between 2,6 mg . kg-1 and 1,7 mg . kg-1. Therefore, although the arsenic total content in some sediment was higher than the Threshold Effects Level (7,24 mg . kg-1) and in another higher than the concentration specified in Effects Range Low (8,2 mg . kg-1), it is considered that the arsenic bioavailable fraction is not significant and that its effect over the biota is not relevant. [ABSTRACT FROM AUTHOR]

Copyright of Revista Facultad de Ciencias Basicas is the property of Revista Facultad de Ciencias Basicas and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Revista de la Sociedad Química del Perú is the property of Sociedad Quimica del Peru and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

It is widely known that arsenic is highly toxic to humans, and the chronic exposure to this element produces various damages to the health of people. In Peru have been reported particularly high levels in rivers of the south coast. Objective. Evaluate two analytical techniques of speciation of the two forms of inorganic arsenic in river water of Tacna, in southern Peru. Material and methods. Developed a comparative study of the technique of separation by anion-exchange resin and ion chromatography for the speciation of arsenic (V) and arsenic (III) in water samples from four rivers of the Pacific slope in two districts of the region Tacna. The total amount of arsenic was determined with flow injection system with atomic absorption attended. Results. We obtained a good degree of separation in both procedures, however, the technique of anionic exchange resins have a lower detection limit of ion chromatography, 2.0 mg/L and 32 mg/L, respectively. In four of the six samples were higher than those recommended by the Environmental Protection Agency of the united States, and they succeeded in determining the amounts of arsenic (III) and arsenic (V). Conclusions. Both techniques can be considered applicable for different types of water; nevertheless, the technique of separation by anion-exchange resin has higher detection sensitivity than the technique of separation by arsenic ion chromatography; and allows a high degree of speciation of inorganic arsenic in samples of river water. [ABSTRACT FROM AUTHOR]

This paper reports on the speciation of heavy metals (Cd, Pb, Cr, Cu, Ni, Mn, Fe, and Zn) in the surface water dissolved fraction of the low basin and plume of the Manzanares River, in the state of Sucre, Venezuela, based on data taken at 22 stations from July 1996 to June 1997. The total metal concentrations in the dissolved phase ranged from below detection levels to 0.01, 0.02, 0.02, 0.10, 0.10, 1.03, 2.56, and 5.13 μmol L-1 for Cd, Pb, Cr, Cu, Ni, Mn, Fe, and Zn, respectively. Overall, the metals studied revealed a nonconservative behavior with removal at low salinities, likely due to anthropogenic contributions and to flocculation on account of Fe- and Mn-oxyhydroxide formation resulting from the shifts in pH and ion forces that ensue when the fresh waters of the river meet the marine water mass of the Gulf of Cariaco. The heavy metals in the dissolved fraction, in both free and hydrated form, had a composition in which the largest proportions were associated with humic acids, thus being more readily available to organisms. [ABSTRACT FROM AUTHOR]

Temporal surveys at the Guadalquivir estuary were carried out between May and December 1998 to assess the behaviour of four heavy metals (Zn, Cd, Pb and Cu). These metals presented a non-conservative behaviour, with K[subD] ranging between 10² and 10[sup4]. Losses related to the dissolved phase have been quantified, as well as their metal speciation. The concentration of heavy metals associated with different geochemical fractions in sediments was also determined. Each metal showed a different distribution depending on whether its origin was associated (Zn and Cd) or not (Pb and Cu) to the toxic mud from Aznalcóllar. In general, heavy metal (Zn and Cd) enrichment was found in the estuary (due to the Aznalcóllar mining spill), determined in their concentrations in the most bioavailable fractions of the sediment. [ABSTRACT FROM AUTHOR]