Influência da Mineração no Incremento e na Disponibilidade Geoquímica de Cobre em Sedimentos Fluviais - O Caso das Minas do Camaquã, RS, Brasil.

This work presents an analysis of copper contamination levels and copper availability in stream sediments of the João Dias Creek in the Minas do Camaquã region, caused by mineral exploitation. Fluvial sediments are predominantly sandy with less than 1% fine fraction (< 63µm), which leads to negligible amounts of environment available metals. The mean copper content in the CH3COONH4 (1M) exchangeable fraction of stream sediments showed an average availability around 7% in the region affected by mining operations. In background area this ratio is less than 2% and up to 13% in the sample point situaded downstream the sludge dam. The mean copper content in the HNO3 (0,1N) extractable fraction of stream sediments showed an average availability around 55% in the region affected by mining operations. In background area this availability is around 10% and reached 90% in the sludge dam. The pollution levels stablished by USEPA for sediments, the contamination factor (CF) and the geoaccumulation index (Igeo) determined in the fine fraction indicated a high copper contamination in the drainage segments affected by mining effluents

Distribuição de metais pesados na bacia hidrográfica do Arroio João Dias, Minas do Camaquã, RS

06

Characterisation of bottom sediment texture of Guaíba Lake, southern Brazil, and its importance to environmental studies

This work detaches the importance of understanding the sedimentary dynamics in environmental researches. One hundred eighty seven bottom sediment samples from Guaíba Lake were collected in 1998. These samples were analyzed for texture and organic matter content. Those physical parameters associated to the lake’s morfodynamics show preferential sites to accumulate fine sediments and organic matter; those are potential geochemical carriers of pollutants. Four textural fields (A: 0-10%, B: 10-50%, C: 50-90% and D: 90-100%) based on the mud percentage (fraction <63µm) of the sediments were defined. They indicate a growing potential of pollutant sorption. Environmental assessment should prioritize sampling of fields C, and especially D, to the detriment of fields A and B. the textural map based on this approach, shows the division of Guaíba Lake in three great cells of fine sediments called, North cell, Central cell and South cell. Future environmental researches carry on the Guaíba Lake can use this tool to orient sediment sampling