Variabilidade espacial e sazonal da concentração de elementos-traço em sedimentos do sistema estuarino de Santos-Cubatão (SP)

Multi-element analyses of sediment samples from the Santos-Cubatão Estuarine System were carried out to investigate the spatial and seasonal variability of trace-element concentrations. The study area contains a rich mangrove ecosystem that is a habitat for tens of thousands of resident and migratory birds, some of them endangered globally. Enrichments of metals in fine-grained surface sediments are, in decreasing order, Hg, Mn, La, Ca, Sr, Cd, Zn, Pb, Ba, Cu, Cr, Fe, Nb, Y, Ni and Ga, relative to pre-industrial background levels. The maximum enrichment ranged from 49 (Hg) to 3.1 (Ga). Mercury concentrations were greater in the Cubatão river than in other sites, while the other elements showed greater concentrations in the Morrão river. Concentrations of Mn were significantly greater in winter and autumn than in summer and spring. However, other elements (e.g. Cd and Pb) showed the opposite, with greater concentrations in summer and spring. This study suggests that seasonal changes in physical and chemical conditions may affect the degree of sediment enrichment and therefore make the assessment of contamination difficult. Consequently, these processes need to be considered when assessing water quality and the potential contamination of biota.

Distribuição, fracionamento e mobilidade de elementos traço em sedimentos superficiais

The gold and iron mining activities in the Velhas River yield considerable amounts of suspended solids as well as metals to the hydrological system of the region. The risks were assessed by sequential extraction procedures. They were carried out in sediment samples, aiming to evaluate the presence of Co, Cr, Cu, Ni, Zn and As. Although being at high levels in some parts of the river (e.g. As 527 mg g-1 and Cr 475 mg g-1) they are associated with the residual fraction. Mobility factors were also calculated and show that these species are enriched along the river, e.g. for As 0.02 at the spring and 0.33 at the high course of the river.

Avaliação da contaminação por elementos metálicos dos sedimentos do Estuário Santos - São Vicente

Three approaches were applied to evaluate metal contamination in 41 sediment samples from the Santos - São Vicente Estuarine System: normalization to Al, statistical analysis and sediment quality guidelines (SQGs). The results showed increases in the concentrations of Zn, Ni, Pb, Cd, Cr and Hg, which seemed to be associated with human activities. The levels of Al, Fe and Co probably were associated with crustal material or natural weathering processes. About 45% of the samples presented concentrations exceeding TEL-ERL, levels occasionally associated with adverse biological effects. Four of these samples presented concentrations above PEL-ERM, levels frequently associated with adverse biological effects.

Estudo da mobilização de metais e elementos traços em ambientes aquáticos do semi-árido brasileiro aplicando análises de componentes principais

The spatial and temporal retention of metals has been studied in water and sediments of the Gavião River, Anagé and Tremedal Reservoirs, located in the semi-arid region, Bahia - Brazil, in order to identify trends in the fluxes of metals from the sediments to the water column. The determination of metals was made by ICP OES and ET AAS. The application of statistical methods showed that this aquatic system presents suitable conditions to move Cd2+ and Pb2+ from the water column to the sediment.

A tabela periódica dos elementos químicos prevista por redes neurais artificiais de Kohonen

Although several chemical elements were not known by end of the 18th century, Mendeleyev came up with an astonishing achievement: the periodic table of elements. He was not only able to predict the existence of (then) new elements but also to provide accurate estimates of their chemical and physical properties. This is certainly a relevant example of the human intelligence. Here, we intend to shed some light on the following question: Can an artificial intelligence system yield a classification of the elements that resembles, in some sense, the periodic table? To achieve our goal, we have fed a self-organized map (SOM) with information available at Mendeleyev's time. Our results show that similar elements tend to form individual clusters. Thus, SOM generates clusters of halogens, alkaline metals and transition metals that show a similarity with the periodic table of elements.

A espectrometria atômica e a determinação de elementos metálicos em material polimérico

Polymeric materials are widely used in the chemical industry and are part of our daily lives. Inorganic species may be added to them as additives, anti-oxidizing agents, stabilizers, plasticizers, colorants and catalysts and may be present in a wide range of concentrations. Their determination demands the development of analytical methods considering different kinds of polymeric materials, their composition and the final use of the material. Although many different analytical techniques may be used, this review emphasizes those based on atomic absorption and emission spectrometry. Solid sampling techniques and digestion methods are described and discussed and compared considering published results.

Elementos-traço e sódio em suco de uva: aspectos nutricionais e toxicológicos

Eight trace elements were determined in 20 Brazilian brands of grape juice, distributed over the country. Highest measured concentrations (As: 0.016; Cd: 0.010; Cr: 0.060; Cu: 1.28; Ni: 0.032; Pb: 0.016; Sb: 0.0040 and Zn: 1.44 mg L-1) comply with Brazilian maximal tolerance levels for inorganic contaminants (As: 0.5; Cd: 0.5; Cr: 0.1; Cu: 30; Ni: 3; Pb: 0.4; Sb: 1 and Zn: 25 mg L-1). Determination of arsenic species has shown inorganic As(V) as predominant in most samples. Sodium concentrations, nowadays a major public health concern, were also measured, showing an average of 149 mg L-1. Analytical results for this element were much higher than label concentrations, showing the need for better quality control.

Modelagem e simulação da desidratação osmótica em pedaços de abacaxi utilizando o método de elementos finitos

Water loss and sugar gain were modelling during the osmotic dehydration process of pieces of pineaplle. The transfer of solute to the fruit and the water to the solution was based on Fick's 2nd law. The three dimensional model was solved by the finite element method with the usage of the software COMSOL Multiphysics 3.2. The main and cross diffusion coefficients and the Biot number were determined on the simulation and the deviation between the experimental and the simulated data were 4,28% to sucrose and 1,66 to the water.

Estudio preliminar sobre la determinación de elementos traza en cervezas venezolanas por ICP-OES

The levels of several chemical elements were determined simultaneously in ten different beers of the Venezuelan market by ICP-OES. With the exception of chromium, beer does not provide important amounts of nutritional oligoelements. The average chromium content found (33 µg/L) is higher than one reported for USA's beer (10 µg/L) but smaller than another reported for Brazilian beer (66 µg/L). The average percentage of chromium RDA by beer consumption found for Venezuela (6.3%) is similar to that reported for Belgium (5%). Regarding toxic elements, one of the samples contained an elevated amount of aluminium, probably dissolved from the aluminium can.

Caracterização dos níveis de elementos químicos em solo, submetido a diferentes sistemas de uso e manejo, utilizando espectrometria de fluorescência de raios-x por energia dispersiva (EDXRF)

This study aimed to evaluate the chemical elements levels in soil, submitted to different management systems and use by the Energy Dispersive X-Ray Fluorescence Spectrometry - EDXRF. The systems were T1 - agro forestry (SAF), T2 - Native Field (CN), T3 - Native Forest (NM), T4 - Tillage Forest (PF); T5 - conventional tillage system (SPC) and T6 - System tillage (NT). Samples were collected at 0-10 and 10-20 cm, dried and ground for analysis in EDX-720. The soil showed no difference in the average concentrations of chemical elements analyzed in the profiles, but the systems presented different concentrations of metal elements, and T3 had the highest K, Ca and Zn at 0-10 cm and higher contents of K, Ca, Cu, Zn and Mn in the layer of 10-20 cm.

Recuperação de chumbo, mercúrio e elementos dos grupos 4 a 7 da tabela periódica de seus resíduos

This work shows routes to recover some elements from their laboratory wastes and broken apparatus (thermometers and densimeters). Most elements chosen present a chemical behavior in aqueous solution which is not currently studied in the ordinary experimental classes. The routes were based on the previous knowledge of the qualitative composition of the wastes treated. Wastes containing chromium were the most difficult to treat. The elements were recovered in good yields and can be reused in new experiments. This work was a very good experience in chemistry for students and shows the need of managing wastes for a better environment.

Núcleos exóticos e síntese dos elementos químicos

We have around ninety chemical elements available in nature, which were produced mainly by nuclear reactions inside stars. The fusion reactions are the main synthesis process which generates the light and intermediate masses elements. The synthesis begins with the hydrogen burning reaching the region of iron mass nuclei. Heavier elements are synthesized by neutron capture processes, forming exotic nuclei with large neutron excess. These systems present characteristics very different from nuclei inside of stable atoms; they only occur in particular astrophysical environments or are produced artificially in special laboratory conditions. This work discusses some properties of the exotic nuclei and how they participate in the synthesis of elements.

Corais como organismos biomonitores: aplicação, pré-tratamento e determinação de elementos majoritários e minoritários

Corals incorporate major and trace elements in their tissues and skeletons, acting as good proxies for contaminant inputs over time. This incorporation occurs by a variety of mechanisms and depends on the bioavailability of elements. Corals are very susceptible to metal contamination during sample collection. As such, pre-treatment procedures need to include a decontamination step. The high Na and Ca concentrations in the matrix make the determination of trace metals an analytical challenge. The present paper reviews all the information published on coral sample pretreatments, metal determinations in corals, and also discusses the use of coral to monitor metal contamination.

Elementos traço em material particulado atmosférico de uma região agroindustrial do sudeste do Brasil

Trace element concentrations were measured in atmospheric particulate matter collected in 2009 and 2010, in a Brazilian region influenced by pre-harvest burning of sugar cane crops. For coarse particles, high concentrations of Al, Fe, K and Ca suggested that re-suspended soil dust was the main source of aerosol trace elements, subsequently confirmed by XRD analysis. High levels of K, Zn, As, Cd and Pb were found in fine particles, confirming the contribution of biomass burning and vehicle emissions, whereas Na, Al, K, Fe and Zn were the representative elements in ultrafine particles, influenced by a diversity of sources.

Análise exploratória rápida e não destrutiva (screening) da presença de elementos químicos tóxicos em material escolar por fluorescência de raios x

Compulsory in Brazil, toy certification aims to prevent possible risks in toy use. The Brazilian National Institute of Metrology (INMETRO) establishes the maximum concentration of toxic elements (TE) that may be present in toys. This study evaluates the presence of TE in different crayons, gouache and modeling clays using X-ray fluorescence. This technique is fast, has low operating cost and minimum sample pretreatment, resulting in a clean procedure without reagent consumption and waste generation. Bromine (in gouache) and Barium (in crayons) were the only potentially TE identified in the samples studied.