Evaluation of water quality of six rivers of São Gonçalo and the risk of contamination to Guanabara Bay, RJ, Brazil

Abstract

Located in the state of Rio de Janeiro, Guanabara Bay holds the second largest industrial center and second largest population of the country, being considered one of the most polluted enviroments of the Brazilian coast; pollution caused mainly by domestic and industrial effluents. The environmental impact due to water pollution can produce as result an imbalanceas of an entire ecosystem, including to the health of people who come into contact with that water contaminated by micro-organisms. This study aimed to evaluate the influence of the rivers of São Gonçalo on the quality of the waters of Guanabara Bay identifying the possible risk of contamination by the users of these waters. Waters of six rivers in São Gonçalo city that flow into the bay were collected monthly during six months. Analysis of termtolerant coliforms showed values above 1.000MPN/100mL in all collections. The analysis of physical-chemical parameters showed values of dissolved oxygen below 5 mg/L in all sampled areas and for total dissolved solids values above 0.5g/L in three of these areas. According to CONAMA resolutions 274/2000 and 357/2005 the water analyzed of the six rivers are not proper for bathing or other purposes and negatively contribute to the quality of Guanabara Bay waters and to the health of bathers and fishermen who use them for recreation and livelihood.