Resumo O município de Caçapava do Sul é responsável por 80% da produção de pó de rocha do estado, e seu 1° distrito se localiza no entorno de quatro mineradoras de mármore. O aumento significativo da extração mineral no Brasil implica em sérios problemas ambientais. Um desses fatores é o desenvolvimento e a proliferação de patologias diretamente relacionadas aos recursos hídricos. A proposta desse estudo foi investigar a composição da água na área do 1º distrito. A investigação geoquímica das águas revelou águas classificadas como mole e duras, com pH neutro e alcalino. A condutividade elétrica varia de 95,7 a 548 μs cm-1, e a alcalinidade total varia de 57 a 241 mg L-1. Os teores de Ca e Mg variam entre 6,01 a 54,1 e 4,6 a 32,75, respectivamente. Todos os valores medidos atendem os padrões de potabilidade para consumo humano estabelecido pelas Portarias nº 2.914 de 2011 e nº 36/GM de 1990 e nº 1469 de 2000.

Abstract Caçapava do Sul, RS, Brazil produces 80% of the State’s rock-dust, and its 1st district is located near four marble quarries. A significant increase in Brazilian mineral extraction has caused serious environmental problems, such as the development and proliferation of diseases directly related to water resources. This study sought to investigate the water composition in the 1st district area. Geochemical investigation revealed waters classified as soft and hard, neutral and alkaline pH. Electric conductivity ranged from 95.7 to 548 μs cm-1, and total alkalinity ranged from 57 to 241 mg L-1. Ca and Mg ranged from 6.01 to 54.1 and from 4.6 to 32.75, respectively. All measured values met the potability standards for human consumption established by Ordinance Nos. 2914 (2011), 36-GM/1990, and1469/2000.

The effect of fluoride ions concentration on the electrochemical behavior of Ti grade 2 and Ti6Al4V in citrate buffers was studied. Open circuit potential (OCP) measurements and voltammetric studies of the samples in the fluoride containing citrate buffers revealed a dissolution process when the pH falls below 5.0 and the NaF content is higher than 0.01 M. However, in citrate pH 7.6 the materials showed a passive behavior even in 0.1 M NaF. Some micrographs of Ti grade 2 obtained after longer immersion times in citrate pH 5.0 with 0.01 M NaF showed a surface attack. EIS (Electrochemical Impedance Sprectroscopy) data obtained at the OCP revealed that the film resistance decreases when the immersion time is increased in pH 5.0 containing 0.1 M NaF. In the citrate pH 7.6 the EIS data indicated a two-layer model of an oxide film consisting of a more compact inner layer and a porous outer layer. On the other hand, the EIS results in citrate pH 4.0 change significantly when the fluoride ions concentration increases from 0.01 to 0.05 M. The electrochemical data revealed that the corrosion behavior of Ti grade 2 and Ti6Al4V in the citrate buffers depends on the pH, the fluoride content and the exposure time.

This paper reports on an investigation of the electrochemical behavior of Ti grade 2 and Ti6Al4V alloy in aqueous citric acid solutions with pH 2.0 containing halide ions. Voltammetric studies of Ti and the alloy in citric acid, with and without chloride ions, indicate that the Ti and Ti alloy presented a passive behavior in the test solutions used. Pitting was observed at 3.0 and 2.5 V/SCE for Ti and Ti6Al4V, respectively, when bromide ions were added to the solution. In solutions containing fluoride ions, dissolution of the film occurred at potentials close to - 1.0 V/SCE in both electrodes. The iodide ions oxidized on the passive oxide film at potentials close to 1.0 V/SCE. EIS results of the materials in citric acid solutions containing chloride ions revealed that the film's resistance increased as the applied potential rose from 0 to 1.0 V. In bromide-containing solutions, breakdown of the film was confirmed at potentials above 2.0 V/SCE in both electrodes. These results suggest film reformation for Ti and the alloy in solutions containing fluoride at potentials within the passive region.