title: Chemical behavior of Cu, Zn, Cd, and Pb in a eutrophic reservoir: speciation and complexation capacity.
abstract: This research aimed at evaluating cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn) speciation in water samples as well as determining water quality parameters (alkalinity, chlorophyll a, chloride, conductivity, dissolved organic carbon, dissolved oxygen, inorganic carbon, nitrate, pH, total suspended solids, and water temperature) in a eutrophic reservoir. This was performed through calculation of free metal ions using the chemical equilibrium software MINEQL+ 4.61, determination of labile, dissolved, and total metal concentrations via differential pulse anodic stripping voltammetry, and determination of complexed metal by the difference between the total concentration of dissolved and labile metal. Additionally, ligand complexation capacities (CC), such as the strength of the association of metals-ligands (logK'ML) and ligand concentrations (C L) were calculated via Ruzic's linearization method. Water samples were taken in winter and summer, and the results showed that for total and dissolved metals, Zn > Cu > Pb > Cd concentration. In general, higher concentrations of Cu and Zn remained complexed with the dissolved fraction, while Pb was mostly complexed with particulate materials. Chemical equilibrium modeling (MINEQL+) showed that Zn(2+) and Cd(2+) dominated the labile species, while Cu and Pb were complexed with carbonates. Zinc was a unique metal for which a direct relation between dissolved species with labile and complexed forms was obtained. The CC for ligands indicated a higher C L for Cu, followed by Pb, Zn, and Cd in decreasing amounts. Nevertheless, the strength of the association of all metals and their respective ligands was similar. Factor analysis with principal component analysis as the extraction procedure confirmed seasonal effects on water quality parameters and metal speciation. Total, dissolved, and complexed Cu and total, dissolved, complexed, and labile Pb species were all higher in winter, whereas in summer, Zn was mostly present in the complexed form. A high degree of deterioration of the reservoir was confirmed by the results of this study.
authors.affiliation: Department of Chemistry, Federal University of São Carlos, Via Washington Luis km 235, PO Box 676, CEP 13565-905, São Carlos, São Paulo, Brazil. aletonietto@gmail.com.|Department of Botany, Federal University of São Carlos, Via Washington Luis km 235, PO Box 676, CEP 13565-905, São Carlos, São Paulo, Brazil. aletonietto@gmail.com.
authors.forename: Alessandra Emanuele
authors.initials: AE
authors.lastname: Tonietto
authors.affiliation: Department of Botany, Federal University of São Carlos, Via Washington Luis km 235, PO Box 676, CEP 13565-905, São Carlos, São Paulo, Brazil.
authors.forename: Ana Teresa
authors.initials: AT
authors.lastname: Lombardi
authors.affiliation: Department of Sea Sciences, Federal University of São Paulo, Baixada Santista Campus, Almirante Saldanha da Gama Avenue, 89, Ponta da Praia, CEP 11030-400, Santos, São Paulo, Brazil.|Post-Graduate Program in Ecology, Santa Cecília University, Oswaldo Cruz Street, 277, Boqueirão, CEP 11045-907, Santos, São Paulo, Brazil.
authors.forename: Rodrigo Brasil
authors.initials: RB
authors.lastname: Choueri
authors.affiliation: Department of Botany, Federal University of São Carlos, Via Washington Luis km 235, PO Box 676, CEP 13565-905, São Carlos, São Paulo, Brazil.
authors.forename: Armando Augusto Henriques
authors.initials: AA
authors.lastname: Vieira
mesh_terms: D002104:Cadmium / Q000737:chemistry; D003300:Copper / Q000737:chemistry; D005068:Eutrophication; D005618:Fresh Water / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007854:Lead / Q000737:chemistry; D019216:Metals, Heavy / Q000737:chemistry*; D013696:Temperature; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D015032:Zinc / Q000737:chemistry
chemical_list: D019216:Metals, Heavy; D014874:Water Pollutants, Chemical; D002104:Cadmium; D007854:Lead; D003300:Copper; D015032:Zinc
keywords: Complexation capacity; Eutrophic reservoir; FA/PCA; Heavy metal; Speciation