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| Author(s): |
Andréa Cristina Tomazelli
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Ribeirão Preto. |
| Institution: | Universidade de São Paulo (USP). Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto (PCARP/BC) |
| Defense date: | 2003-12-16 |
| Examining board members: |
Luiz Antonio Martinelli;
Jose Roberto Ferreira;
Anne Hélène Fostier;
Wilson de Figueiredo Jardim;
Antonio Aparecido Mozeto
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| Advisor: | Luiz Antonio Martinelli |
| Abstract | |
Concentrations of cadmium (Cd), lead (Pb), and mercury (Hg) were determined in water (dissolved and particulate), bottom sediment, fish, and bivalves sampled in six watersheds located in the State of São Paulo (Southeast, Brazil): the Alto Paranapanema, the Peixe, the Aguapeí, the São José dos Dourados, the Mogi-Guaçu, and the Piracicaba. These watersheds show different levels of land-use. Among these basins, the Piracicaba and the Mogi-Guaçu River Basins show highest population and industrialization rates. Such features lead, consequently, to a higher degradation of water, thus decreasing its quality. These facts emphasize the need of new and frequent studies in those systems. Water and sediment samplings were carried out bimonthly during 2001. Fish and bivalves samples were collected twice a year: at the end of the rainy and dry season. Cd and Pb concentrations were determined through electrotermal atomic absorption spectrometry, whereas Hg through atomic fluorescence spectrometry. In addition, exchangeable Cd and Pb were determined in sediment. The results showed low concentrations of Cd and Pb in water (dissolved and particulate). However, these concentrations were higher in the Piracicaba and the Mogi-Guaçu River Basins. Pb concentrations in sediment and bivalves were the highest in the Mogi-Guaçu River, even so this element occurred in low levels in the exchangeable fraction of sediment (< 1%). The highest Cd concentrations in sediment and particulate suspended matter were related to the Piracicaba River, although the highest levels for bivalves occurred in the Mogi-Guaçu River. High Cd concentrations in the exchangeable fraction of sediment (up to 76%) were observed, mainly in the Itapetininga (the Alto Paranapanema Basin), the Piracicaba, and the Mogi-Guaçu River. High concentrations of Hg were detected in some water and sediment samples, whereas in bivalves Hg was always in low levels. However, no significant tendency of temporal and/or spatial distribution was observed for Hg, so it is belived that the high levels reported for some samples were a result from diffuse non-point source pollution, such as atmospheric deposition and residues from agricultural practices. Cd and Pb concentrations in fish were always lower than the detection limit (0.005 and 0.08 µg/g dry wt, respectively). On the other hand, high concentrations of Hg (1.14 +/- 0,54 µg/g wet wt) and methylmercury (1.04 +/- 0.51 µg/g wet wt), which represented 92% of the total mercury, were found in carnivorous fish samples from the Jurumirim Reservoir (the Alto Paranapanema Basin). These concentrations were higher than the maximum limit permitted by Brazillian legislation for predatory fish (1 µg/g wet wt) and, probably, were a result from high methylmercury levels produced and released in the reservoir supported by inundated soil and vegetation. Hence, we concluded that carnivorous fish from the Jurumirim Reservoir were contamined with Hg, therefore new research sould be carried out in that area in order to identify the sources and processes responsible for high levels of mercury. The Peixe, the Aguapeí, the Alto Paranapanema, and the São José dos Dourados River Basins showed relatively low concentrations of all elements studied. Conversely, high Cd concentrations were determined in the Piracicaba River, and Pb and Cd in the Mogi-Guaçu River, pointing out that these areas should be frequently monitored. (AU) | |