Integrated assessment of chemical quality and genotoxicity of the water of the Luiz Rau Stream in the lower stretch of the Sinos River Basin, in South Brazil

This study assessed the chemical quality and genotoxicity of the water of the Luiz Rau Stream in Novo Hamburgo (Rio Grande do Sul, Brazil) and investigated the relationship between the genetic damage observed in Tradescantia pallida var. purpurea and the chemical parameters analyzed. Water samplings were collected bimonthly from September 2012 to March 2013 from two sites, near the headspring (S1) and near the mouth (S2). Cuttings with flower buds were exposed to water from the sites and distilled water (negative control). Micronuclei (MCN) frequencies were determined in pollen mother cells. The chemical parameters analyzed were pH, total dissolved solids, biochemical oxygen demand (DBO5), dissolved oxygen, total phosphorus (TP) and the trace elements cadmium, lead, copper, total chromium and zinc. In all samplings, the MCN frequencies observed in buds exposed to water from both sites were significantly higher (S1: 2.48 to 3.38, S2: 3.24 to 5.19) than those observed in the respective negative controls (1.33 to 1.62). The TP was above the legal limit throughout the monitored period and DBO5 presented concentrations higher than those established by legislation in two months at S1 and three months at S2. The principal component analysis showed a relationship between MCN frequency, DBO5 and TP, pointing to the negative influence of pollutants present in water on the bioindicator species and reinforcing the importance of considering the environmental factors in an integrated way in water-body monitoring programs.