José do Patrocínio Hora Alves

Metal fractionation in sediments of the Sergipe River, northeast, Brazil

The sequential extraction procedure proposed by the European Community Bureau of Reference (BCR) was applied for the fractionation of Cd, Cr, Cu, Ni, Pb and Zn in sediments from the Sergipe Estuary, Brazil. The method showed satisfactory recoveries, detection limits and standard deviations for trace metals determinations in sediment samples. Cd was the metal with the greatest percentage in the exchangeable fraction. Pb and Ni were present mainly in the reducible and oxidizable fractions. Cr, Cu and Zn were predominantly associated with the residual fraction. The order of mobility of metals extracted was Pb > Cd > Ni > Cu > Cr > Zn. According to the risk assessment code (RAC), the sediments showed low to medium risk for all metals.

Metals and acid volatile sulfide in sediment cores from the Sergipe River Estuary, Northeast, Brazil

Acid volatile sulfide (AVS), simultaneously extracted metals (SEM) and metals were studied in sediment cores from the Sergipe River Estuary, Brazil. AVS and SEM concentrations were, in general, higher in the core sediments from areas which receive a higher anthropic contribution due to urban pollution. In these cores, the sulfide seemed to be the main connection for the metals. In the core obtained from the area of major marine influence, the most important binding phases for the metals seemed to be associated with organic matter and carbonates. The AVS profiles allow identification of two types of sedimentation processes in the estuary. In all cores SEM/AVS ratios were much lower than 1.

Regional geochemical baselines and controlling factors for trace metals in sediments from the Poxim River, Northeast Brazil

The Poxim river hydrographic sub-basin comprises four freshwater rivers, Poxim-Acu, Poxim-Mirim, Poxim and Pitanga, and is located in the East of Sergipe State, Northeast of Brazil. The present work investigates the distribution, the factors controlling concentrations, and toxicity risks of the metals Co, Cr, Cu, Li, Mn, Ni, Pb, Zn, Al and Fe, in surface sediments of the four rivers. Toxicity was evaluated using the Consensus-based Sediment Quality Guidelines for freshwater ecosystems. Spearman correlation analysis did not indicate any association of the metals with organic matter, however strong, moderate and weak correlations with aluminium, iron, and manganese, respectively, suggested that clay minerals were the main carrier of metals to sediments. Concentrations of metals in all samples were below the TEC (threshold effect concentration), indicating that for these trace metals adverse effects on aquatic biota should rarely occur. A geochemical baseline for the region was defined using lithium as reference element. Metal enrichments due to anthropogenic influence were only observed at three sites. At other sites, enrichment factors were indicative of a large predominance of naturally occurring metals in the sediments.

Electroreduction of the antifouling agent TCMTB and its electroanalytical determination in tannery wastewaters

The electrochemical reduction of antifouling agent 2-thiocyanomethylthiobenzothiazole (TCMTB) was investigated by cyclic and pulse differential voltammetry. The irreversible electrode reduction of TCMTB proceeded by ECEC reaction mechanism by two electrons transfer with one irreversible wave. Upon the basis of electrochemical evidence, the electrodic reaction mechanism was suggested to formation of mercaptobenzothiazole (MTB) in solution. Subsequently, a pulse differential method is described for the formation of TCMTB based on this electroreduction. Having been obtained a detection limit of 1.0 x 10(-7)mol L(-1) and recovery to 98% to concentration of 2.0 x 10(-6)mol L(-1). Therefore, the proposed method in this study is practical, sensitive and accurate for the analysis of TCMTB in tannery wastewater samples.

Assessment of trace metals pollution in estuarine sediments using SEM-AVS and ERM-ERL predictions.

This paper presents the distributions of the investigation of trace metals geochemistry in surface sediments of the Sergipe river estuary, northeast Brazil. Analyses were carried out by Flame or electrothermal atomic absorption spectrometry (FAAS or ETAAS). Principal component analysis was applied to results to identify any groupings among the different sampling sites. In order to determine the extent of contamination, taking into account natural variability within the region, metal concentrations were normalized relative to aluminium. Cr, Cu, Ni and Zn contamination was observed in sediments from the area receiving highest inputs of domestic wastes, while cadmium contamination occurred in sediments from the region affected by highest inflows of industrial effluents. Possible toxicity related to these metals was examined using the relationship simultaneously extracted metals/acid volatile sulfide and by comparing sediment chemical data with sediment quality guidelines ERL-ERM values. Results obtained using the two methods were in agreement and indicated that adverse effects on aquatic biota should rarely occur.

Concentrações e associações geoquímicas de Pb e Zn em sedimentos do rio São Francisco impactados por rejeitos da produção industrial de zinco

Surface sediments from the River Sao Francisco were analyzed to investigate the impact, due to the presence of metals (Cd, Cu, Pb, Zn) in wastes from a metallurgical industry in the city of Tres Marias/MG, Brazil. The concentrations and geochemical associations of Pb, Zn and trace metals associated with the minerals employed in zinc production were measured. Sediments close to discharge locations were highly contaminated with Pb (332-512 μg g-1) and Zn (7872-10780 μg g-1), with values decreasing rapidly due to dilution and hydraulic sorting. Evaluation of toxicity according to the Consensus-based Sediment Quality Guidelines indicated for Cd, Pb and Zn a high probability of adverse effects on aquatic biota at these sites.

Evaluation of the physico-chemical properties of chitosan as a potential carrier for rifampicin, using voltammetric and spectrophotometric techniques.

Rifampicin is an antibiotic which, on a carbon paste electrode, shows an oxidation response of 0.492 V (vs. Ag/AgCl) at pH 7.0, due to the electroactivity of the hydroquinone group. Interaction of rifampicin with chitosan is strongly dependent on pH, species concentrations and contact time between the latter. Compared to the carbon paste electrode, electrodes modified with chitosan showed greater sensitivity, with optimum voltammetric profile obtained at pH 8.0. Spectrophotometric measurements indicate that rifampicin is strongly absorbed by chitosan at pH less than the pKa of the pharmaceutical, such behaviour being favourable for the use of chitosan as a carrier for the controlled release of rifampicin in the intestinal tract.

Characterization of dissolved organic matter in the Piauí river estuary, Northeast Brazil

Fluorescence spectroscopy and dissolved organic carbon (DOC) measurements were used to characterize the dissolved organic matter (DOM) in the Piaui River estuary, a tropical estuary situated in the State of Sergipe, Northeast Brazil. Fluorescence intensities were greater during the rainy period than the dry period, demonstrating that variability in the fluorescence properties of the DOM was determined mainly by the fluvial discharge and the dilution processes occurring in the estuary. During the rainy period, tryptophan-like and humic substances were the main components of the DOM, while during the dry period there was a significant increase of protein-like constituents. Relationships identified between fluorescence intensities and salinity were indicative of non-conservative behavior of the fluorescent DOM. DOC showed behavior that was conservative during the dry period, and non-conservative during the rainy period, with production of DOC in the upper reaches of the estuary. The complexation of DOM with Cu(II), studied using the fluorescence suppression technique, showed the complexation potentials of protein, tryptophan and humic type fluorophores.

Simultaneous Determination of Thorium and Uranium in Mineral Fertilizers by Inductively Coupled Plasma Optical Emission Spectrometry

The simultaneous determination of thorium and uranium in mineral fertilizers by inductively coupled plasma optical emission spectrometry (ICP OES) was optimized. The three-level factorial design was applied to optimize the operating conditions of radiofrequency power and nebulizer gas flow rate. The analytical method was specific and selective for both elements.

Electrochemical and theoretical evaluation of the interaction between dna and amodiaquine: evidence of the guanine adduct formation

The electrochemical behavior of the interaction of amodiaquine with DNA on a carbon paste electrode was studied using voltametric techniques. In an acid medium, an electroactive adduct is formed when amodiaquine interacts with DNA. The anodic peak is dependent on pH, scan rate and the concentration of the pharmaceutical. Adduct formation is irreversible in nature, and preferentially occurs by interaction of the amodiaquine with the guanine group. Theoretical calculations for optimization of geometry, and DFT analyses and on the electrostatic potential map (EPM), were used in the investigation of adduct formation between amodiaquine and DNA.