Helena M. V. M. Soares

Sediments as monitors of heavy metal contamination in the Ave river basin (Portugal): multivariate analysis of data.

The concentrations of heavy metals (Cd, Cr, Cu, Ni, Pb, Zn) were determined in river sediments collected at the Ave river basin (Portugal) to obtain a general classification scenery of the pollution in this highly polluted region. Multivariate data analysis techniques of clustering, principal components and eigenvector projections were used in this classification. Five general areas with different polluting characteristics were detected and several individual heavy metal concentration abnormalities were detected in restricted areas. A good correlation between the overall metal contamination determined by multivariate analysis and metal pollution indexes for all sampling stations was obtained. Some preliminary experiments showed that the metal concentrations normalised to the volatile matter content in the sediment fraction with grain size <63 microm seems to be an adequate method for assessing metal pollution.

Simultaneous electrochemical determination of arsenic, copper, lead and mercury in unpolluted fresh waters using a vibrating gold microwire electrode

In this work, a simple, rapid, reliable and low cost method for simultaneous electrochemical determination of As, Cu, Hg and Pb ions, on a vibrating gold microwire electrode combined with stripping voltammetry, is described for the first time. The multi-element detection was performed in the presence of oxygen by differential pulse anodic stripping voltammetry (DPASV) in HCl 0.1 M with NaCl 0.5 M. This media was found optimum in terms of peak resolution, peak shape and sensitivities, and has a composition similar to seawater to which the method could potentially be applied. The gold microwire electrode presented well defined, undistorted, sharp and reproducible peaks for trace concentrations of Cu, Hg and Pb and As presented a reproducible peak with a small shoulder. Using a gold vibrating microwire electrode of 25 μm diameter and 30s deposition time, the detection limits of As, Cu, Hg and Pb were 0.07, 0.4, 0.07 and 0.2 μgL(-1), respectively. Possible effects of Al, Cd, Cr, Fe, Mn, Ni, Sb and Zn were investigated but did not cause any significant interferences. Finally, the method was applied for the simultaneous determination of these four metals in unpolluted river water samples and the results were validated by Atomic Absorption Spectroscopy with Electrothermal Atomization (AAS-EA) or by Inductively Coupled Plasma Mass Spectrometry (ICP-MS).

Seasonal variations of heavy metals in sediments and aquatic mosses from the Cávado river basin (Portugal)

Abstract Concentrations of Cd, Cr, Cu, Ni, Pb and Zn in surface sediments and aquatic mosses from the Cavado river basin were determined in order to evaluate the overall metal contamination and trace the main pollution sources. The natural background levels were calculated for both plants and sediments (fraction μ m) collected at uncontaminated sites and concentrations were normalized to the natural levels. The maximum resulting contamination factors in the aquatic mosses ranged from 6 (Zn) to 101 (Cr). In the sediments the accumulation rates are lower, between 3 (Zn) and 18 (Pb). The degree of contamination was also evaluated by calculating a metal pollution index and the more polluted reaches were identified. Metal concentration variations in plants and sediments in two different surveys (1988 and 1989) were studied by factor analysis. Three factors are sufficient to characterize data variance. Factors corresponding to plants and sediments show different metal composition and provide evidence that industrial effluents and drainage waters from a mining area are the main causes of variations of element concentrations. The seasonal variations of metal concentrations both in plants and sediments are also discussed.

Evaluation of n-substituted aminosulfonic acid pH buffers with a morpholinic ring for cadmium and lead speciation studies by electroanalytical techniques

Abstract The electrochemical behavior of cadmium and lead metal ions was investigated in the presence of different pH buffers [3-(N-morpholino)-2-hydroxypropanesulfonic acid (MOPSO), 2-(N-morpholino)ethanesulfonic acid (MES) and 3-(N-morpholino)propanesulfonic acid (MOPS)] by various methods [differential pulse anodic stripping voltammetry (DPASV), differential pulse polarography (DPP) and cyclic voltammetry (CV)]. The complexation and/or adsorption properties of these pH buffers were also examined. Conclusions about the possible influences of these pH buffers on the speciation studies of cadmium and lead metal ions are drawn. MES, MOPSO and MOPS can be suitable pH buffers for determination of both metals by DPP and DPASV as they do not complex these metals and do not modify to a significant extent the reversibility of the electrochemical processes under the experimental conditions used.

Bioremediation of industrial effluents containing heavy metals using brewing cells of Saccharomyces cerevisiae as a green technology: a review

The release of heavy metals into the environment, mainly as a consequence of anthropogenic activities, constitutes a worldwide environmental pollution problem. Unlike organic pollutants, heavy metals are not degraded and remain indefinitely in the ecosystem, which poses a different kind of challenge for remediation. It seems that the “best treatment technologies” available may not be completely effective for metal removal or can be expensive; therefore, new methodologies have been proposed for the detoxification of metal-bearing wastewaters. The present work reviews and discusses the advantages of using brewing yeast cells of Saccharomyces cerevisiae in the detoxification of effluents containing heavy metals. The current knowledge of the mechanisms of metal removal by yeast biomass is presented. The use of live or dead biomass and the influence of biomass inactivation on the metal accumulation characteristics are outlined. The role of chemical speciation for predicting and optimising the efficiency of metal removal is highlighted. The problem of biomass separation, after treatment of the effluents, and the use of flocculent characteristics, as an alternative process of cell–liquid separation, are also discussed. The use of yeast cells in the treatment of real effluents to bridge the gap between fundamental and applied studies is presented and updated. The convenient management of the contaminated biomass and the advantages of the selective recovery of heavy metals in the development of a closed cycle without residues (green technology) are critically reviewed.

Removal of heavy metals using a brewer’s yeast strain of Saccharomyces cerevisiae: advantages of using dead biomass

Aim:  The capacities of live and heat‐killed cells of Saccharomyces cerevisiae at 45°C for the removal of copper, nickel and zinc from the solution were compared.

(Un)suitability of the use of pH buffers in biological, biochemical and environmental studies and their interaction with metal ions – a review

The use of buffers to maintain the pH within a desired range is a very common practice in chemical, biochemical and biological studies. Among them, zwitterionic N-substituted aminosulfonic acids, usually known as Good’s buffers, although widely used, can complex metals and interact with biological systems. The present work reviews, discusses and updates the metal complexation characteristics of thirty one commercially available buffers. In addition, their impact on biological systems is also presented. The influences of these buffers on the results obtained in biological, biochemical and environmental studies, with special focus on their interaction with metal ions, are highlighted and critically reviewed. Using chemical speciation simulations, based on the current knowledge of the metal–buffer stability constants, a proposal of the most adequate buffer to employ for a given metal ion is presented.

Determination of arsenic and antimony in seawater by voltammetric and chronopotentiometric stripping using a vibrated gold microwire electrode

The oxidation potentials of As(0)/As(III) and Sb(0)/Sb(III) on the gold electrode are very close to each other due to their similar chemistry. Arsenic concentration in seawater is low (10-20 nM), Sb occurring at ~0.1 time that of As. Methods are shown here for the electroanalytical speciation of inorganic arsenic and inorganic antimony in seawater using a solid gold microwire electrode. Anodic stripping voltammetry (ASV) and chronopotentiometry (ASC) are used at pH ≤2 and pH 8, using a vibrating gold microwire electrode. Under vibrations, the diffusion layer size at a 5 μm diameter wire is 0.7 μm. The detection limits for the As(III) and Sb(III) are below 0.1 nM using 2 min and 10 min deposition times respectively. As(III) and Sb(III) can be determined in acidic conditions (after addition of hydrazine) or at neutral pH. In the latter case, oxidation of As(0) to As(III) was found to proceed through a transient As(III) species. Adsorption of this species on the gold electrode at potentials where Sb(III) diffused away is used for selective deposition of As(III). Addition of EDTA removes the interfering effect of manganese when analysing As(III). Imposition of a desorption step for Sb(III) analysis is required. Total inorganic arsenic (iAs=As(V)+As(III)) can be determined without interference from Sb nor mono-methyl arsenious acid (MMA) at 1.6<pH<2 using E(dep)=-1 V. Total inorganic antimony (iSb=Sb(V)+Sb(III)) is determined at pH 1 using E(dep)=-1.8 V without interference by As. The methods were tested in samples from the Irish Sea (Liverpool Bay). As(III) was determined on-board ship immediately after sampling. As(III) concentrations were found to range from 0.44 to 1.56 nM and were higher near the coast. Sb(III) was below the detection limit (<0.1 nM Sb(III)), iAs was comprised between 8 and 25 nM while iSb varied from 0.5 to 1.7 nM.

Removal of heavy metals using a brewer's yeast strain of Saccharomyces cerevisiae: chemical speciation as a tool in the prediction and improving of treatment efficiency of real electroplating effluents.

In the present work, the influence of the competitive effect of inorganic ligands (carbonates, chlorides, fluorides, phosphates, nitrates and sulphates), which can be present in real multi-metal electroplating effluents, on the biosorption of chromium, copper, nickel and zinc ions by yeast cells of Saccharomyces cerevisiae was rationally examined. Additionally, chemical speciation studies allowed optimizing the amount of yeast biomass to be used in the treatment of effluents contaminated with nickel. The applicability of chemical simulation studies was tested using two simulated effluents and validated using one real electroplating effluent, all containing high concentrations of nickel (about 303 micro mol l(-1)). For nickel removal, heat-killed biomass of a brewing flocculent strain of S. cerevisiae was used, in a batch mode. After the implementation of the bioremediation process (12 g dry weight l(-1) of yeast cells), the concentration of nickel in the real effluent (34 micro mol l(-1)) reached the quality criteria for industrial effluents discharge, after the second or third batch according to the U.S.-Environmental Protection Agency and Portuguese law, respectively. This corresponded to a removal of nickel of 89%.

Biodegradable chelating agents for industrial, domestic, and agricultural applications--a review.

Aminopolycarboxylates, like ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA), are chelating agents widely used in several industrial, agricultural, and domestic applications. However, the fact that they are not biodegradable leads to the presence of considerable amounts in aquatic systems, with serious environmental consequences. The replacement of these compounds by biodegradable alternatives has been the object of study in the last three decades. This paper reviews the most relevant studies towards the use of environmentally friendly chelating agents in a large number of applications: oxidative bleaching, detergents and cleaning compositions, scale prevention and reduction, remediation of soils, agriculture, electroplating, waste treatment, and biocides. Nitrilotriacetic acid (NTA), ethylenediaminedisuccinic acid (EDDS), and iminodisuccinic acid (IDS) are the most commonly suggested to replace the nonbiodegradable chelating agents. Depending on the application, the requirements for metal complexation might differ. Metal chelation ability of the most promising compounds [NTA, EDDS, IDS, methylglycinediacetic acid (MGDA), l-glutamic acid N,N-diacetic acid (GLDA), ethylenediamine-N,N′-diglutaric acid (EDDG), ethylenediamine-N,N′-dimalonic acid (EDDM), 3-hydroxy-2,2-iminodisuccinic acid (HIDS), 2-hydroxyethyliminodiacetic acid (HEIDA), pyridine-2,6-dicarboxylic acid (PDA)] with Fe, Mn, Cu, Pb, Cd, Zn, Ca, and Mg was simulated by computer calculations. The advantages or disadvantages of each compound for the most important applications were discussed.