Quality monitoring and assessment of mercury contamination in water and sediments of the Botafogo river, PE, Brazil

Abstract

Since the mid 80's, the riverside population of Rio Botafogo, in the Santa Cruz channel, Itamaracá has undergone critical environmental situations due to poorly planned growth and inadequate soil occupation, and as a consequence, a loss in environmental quality resulted. In 1963, an industry for production of chlorine and caustic soda produced by electrolytic cell of mercury was installed in the Botafogo river. By mid-1987, a discharge of inorganic mercury between 22 and 35 tones of mercury in this river was estimated. In addition to this industry, others of different types were installed in recent years along the sides of this river. Based on previous studies, we conducted a new assessment of contaminated sites, comparing the changes over the years concerning the quality of water and sediment of the Botafogo river, in which the locations of collection, the need to increase the network of environmental monitoring were investigated. The parameters defined for analysis of water were: pH, dissolved oxygen (OD), biochemical oxygen demand (BOD), ammonia and phosphorus concentration, color, turbidity and mercury content. It was monitored the concentration of mercury in the sediments. The values of pH, turbidity, DO, BOD and ammonia usually showed values within the limits established by CONAMA Resolution No 357. Color parameters have remained consistently high, probably caused by continuous withdrawal of sand before the points of collection. The content of phosphorus was high, until the beginning of 2005, and remained within standards required by legislation until the end of this research. In the studied area, it has been installed, since 1963, an industry for chlorine and caustic soda production, which uses in its manufacturing process electrolytic cell of mercury. In this experiment, the impact of mercury has been observed.