Copper and cadmium complexation by Cylindrospermopsis raciborskii exudates

Autor(es)

Tonietto, Alessandra Emanuele ^[1] ; Oliveira, Natalia L. ^[2] ; Lombardi, Ana Teresa ^[1] ; Polpo, Adriano ^[2]

Afiliação do(s) autor(es)

^[1] Univ Fed Sao Carlos, Dept Bot, Via Washington Luis Km 235, POB 676, BR-13565905 Sao Paulo - Brazil

^[2] Univ Fed Sao Carlos, Dept Stat, Via Washington Luis Km 235, BR-13565905 Sao Paulo - Brazil

• Tipo de documento: Artigo Científico
• Fonte: WATER SCIENCE AND TECHNOLOGY; v. 73, n. 10, p. 2544-2551, MAY 2016.
• Citações Web of Science: 3

Resumo

Cylindrospermopsis raciborskii is a potentially toxic cyanobacterium that excretes organic materials which act as ligands for metals. Metal ligands may be characterized for their strength of association, e.g., stability constants, which can be either thermodynamic (K) or conditional (K'). In this research we examined K and K' for Cu and Cd complexes with three molecular weight fractions (>30 kDa; 30-10 kDa; 10-3 kDa) of the cyanobacteria EOM. Complexation capacities of the excreted organic materials (EOM) for metals were determined at several ionic strengths (1.0 x 10(-2), 5.0 x 10(-2), 1.0 x 10(-1), and 5.0 x 10(-1) mol L-1) at pH 6.6 +/- 0.1, with ligands for which no data for their acidity constants are available; these constants are thus conditional for this specific pH. Bayesian statistics showed that with a probability of 95-100% the EOM have two different ligands for Cu but only one for Cd, that ligands for Cu were stronger than for Cd (94-100% probability), and that the smallest EOM fraction had the highest strength of association for Cu (logK(CuL) 13.5). The lowest affinity was obtained for Cd (logK(CdL) 8.6) complexed to any molecular weight fraction. The present findings have important ecological implications, since the metal-ligand association is dynamic, and together with a diversity of ligands it can act as an environmental metal buffer. As a result, higher metal loads may be necessary for the detection of toxicity. (AU)

• Processo FAPESP: 10/11985-0 - Interação dos metais cobre e zinco com ligantes produzidos por Cylindrospermopsis raciborskii através da determinação da constante de estabilidade termodinâmica
• Beneficiário: Alessandra Emanuele Tonietto
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado