Total hardness of surface waters in São Paulo State (Brazil)

ARAGÃO¹, M.A.; BURATINI¹, S . V. & BERTOLETTI¹, E.

¹ Companhia de Tecnologia de Saneamento Ambiental (Cetesb) - Setor de Ecotoxicologia Aquática. Av. Prof. Frederico Hermann Jr. 345 - Pinheiros – São Paulo, Brasil. CEP:05459-900. e-mail: marciaaa@cetesb.sp.gov.br

ABSTRACT: The aim of this study was to determine the total hardness of surface waters from 112 sampling sites in São Paulo State, using the EDTA Titrimetric Method, in order to assess the appropriate water conditions for toxicity tests with aquatic organisms. Freshwaters from São Paulo were classified as soft waters (mean total hardness of 31 mg/L CaCO₃) and it allows the use of soft water with total hardness between 40-48 mg/L CaCO₃ in aquatic organism culturing and toxicity testing in São Paulo State.

Key-words: hardness, surface waters, toxicity tests, Daphnia, Ceriodaphnia.