Determination of trace metals in water from Mangueira Lagoon – RS, Brazil Filipe Sousa dos Santos a , Eduarda Medran Rangel b, * and Pedro José Sanches Filho a a Federal Institute of Education, Science and Technology Sul-rio-grandense, Pelotas-RS – CEP 96015-360, Brazil b Federal University of Pelotas, Pelotas-RS – CEP 96010-610, Brazil *Corresponding author. E-mail: eduardamrangel@gmail.com Abstract Determination of trace metals was carried out in Mangueira Lagoon, in the southern zone of Rio Grande do Sul. Samples were collected at five points to evaluate the concentrations of the following trace metals: copper, zinc, lead, chromium, nickel and iron. Metals were determined by digestion with concentrated nitric acid and pre-concentrated in Chelex 100 resin analyzed by atomic absorption spectrophotometry. In parallel, the phys- ical-chemical parameters pH, chlorides, alkalinity, hardness and organic matter in the water were determined. Potassium and sodium metals were analyzed by atomic emission spectrometry. The analyzes of pH and conduc- tance were analyzed in the field while the others were done in the laboratory of the research group of environmental contaminants (GPCA). Through the results of physical-chemical parameters of the water, the Man- gueira Lagoon exhibits a low degree of contamination, but in the future may compromise the biota of the lagoon. Regarding the focus of this work, of Cu, Cr, Fe, Ni, Pb, and Zn (heavy metals), only lead and iron obtained the values above that are established in CONAMA 357/2005. Key words: Chelex, lagoon, metals, water INTRODUCTION The coastal region of the Rio Grande do Sul state is characterised by a large number of rivers and lagoons, with the Laguna dos Patos, Mirim and Mangueira Lagoons standing out in volume. Mangueira Lagoon (Figure 1), an integral part of the Mirim Lagoon Basin, is located in the eastern portion of the southernmost part of Brazil. Because it is an area with unique geographical features, a diverse biological population, a particular water regime and very characteristic human population dynamics, it was recognized by UNESCO as a biosphere reserve ( Jica 2000). This lagoon consists of a large shallow lake with surface area of approximately 820 km 2 , and an average depth of 2.49 m and maximum depth of 6.5 m. The shape of the lagoon is elongated in the north-south direc- tion, with a length of 90 km and width of approximately 10 km. The basin of contribution to Mangueira Lagoon has an area of 417 km 2 (Tejadas et al. 2016). The fishing activity of the region is developed artisanally and is the main source of income of numerous families of fishermen (Caldasso et al. 2006). Most of the region is also used for the pro- duction of rice and livestock and the groundwater of the region is intensely used for the domestic supply of the rural population (Silva et al. 2009). According to Silva et al. (2009) the territory around Mangueira Lagoon is primarily characterised by rice crop irrigation since the 1930’s, with a significant water resources consumption and evidence of environmental changes. © IWA Publishing 2018 Water Practice & Technology Vol 13 No 3 612 doi: 10.2166/wpt.2018.077 Downloaded from http://iwaponline.com/wpt/article-pdf/13/3/612/479343/wpt0130612.pdf by guest on 01 March 2022