Metais pesados e efeitos genotóxicos em sedimentos de reservatórios (lagos artificiais)

Abstract

Aquatic ecosystems provide many services to humanity, despite this; water pollution is one of the most serious environmental problems worldwide. Reservoirs, including ones used for water supply, receive from tributaries, or directly, several effluents from human activities that contain a pool of pollutants. Reservoir sediments work as sink or source for pollutants depending on environmental conditions. Therefore, pollutants present in these aquatic compartments can return to the water column or transfer through the food chain, where they can be toxic to biota and even to humans. Contaminants in the environment can cause mutagenic effects that can accumulate in DNA and harm a whole population. Then, genotoxicity tests, such as Allium cepa assay, may be used to evaluate the extent of environmental pollution, since synergistic effects might occur and physicochemical analysis just provide the presence of pollutants. Studies focusing on the presence of chemical compounds in reservoirs sediments and their toxicity are crucial. In this context, the study aimed to investigate contamination in sediments by metals in Brazilian reservoirs, as well as potential ecological risk and potential to cause cytogenotoxicity in A. cepa. Copper, chromium, cadmium, lead, zinc and iron were measured in sediment samples from six Brazilian reservoirs. Besides that, the surface layer of sediment was submitted to a resuspension simulation to the water column, and sediment solution was submitted to Allium cepa assay and metals analysis. Our findings showed that these reservoirs seem to be influenced by agricultural, industrial and domestical effluents because of the presence of copper, cadmium, and zinc above threshold effect levels in some samples and a potential ecological risk was observed. More than that decrease mitotic index and increase chromosomal aberrations in all treatments (except Furnas reservoir) showed cytogenotoxic effects. The presence of metals and other possibly inorganic and organic pollutants may be answerable for cytogenotoxic effects observed. In this sense, just chemical analyses were not enough to evaluate the extent of environmental pollution in sediments and its impact. We need to use more tools combined with chemical analysis to provide a better understand of pollution in aquatic ecosystems. It is important to implement law and regulations that are more efficient, intensive monitoring, sewage treatment and reforestation of riparian zones to protect these systems, including preventing public health problems.