Mobilidade dos metais Fe, Mn, Cr e Ni nas águas subterrâneas e sedimentos do arroio João Correa, proveniente de área de disposição irregular de resíduos sólidos

Abstract

Although the investments in basic sanitation have increased in Brazil as a whole in the last decades, it is still common to find areas where urban solid waste is irregularly disposed of in the urban perimeter of several Brazilian cities. These areas, after deactivated, are frequently occupied by low income citizens, consequently urbanized by the public power, posing risk to the integrity of the local population. In this sense, this research aimed to evaluate the mobility of Fe, Mn, Cr and Ni in groundwaters of an old area of irregular disposal of solid urban waste in São Leopoldo, which is now inhabited. The place had already been object of an environmental diagnosis done by Gomes et al. (2016), in which it was proven the groundwater was contaminated by Fe, Mn, Cr and Ni. Taking the discovery raised by the diagnosis, the current study evaluated the evolution of the aforementioned metals presence in the evaluated groundwaters, surface waters and sediments in the bottom of surface bodies of water. In addition to the monitoring of waters and sediments, a sample of soil was collected and analyzed as to cations exchange capacity, with the intention of verifying the sorption of the contaminants by the soil. Concentrations up to 210.161,00 µg/L of Fe, 34.349,00µg/L of Mn, 3.486,00 µg/L of Cr and 164,00 µg/L of Ni in the groundwaters, in conjunction to the negative correlations between the metals and the pH, to the positive correlations between the metals and the infiltration of rain waters and dissolved oxygen, to the flow of groundwaters towards surface waters, to the low contaminants sorption capacity of soil and to concentrations up to 255.841,00 mg/kg of Fe, 3.017,00 mg/kg of Mn, 433,00 mg/kg of Cr and 208,00 of Ni in sediments of João Correa Stream, which limits with the studed area, poited out the metal mobility and their migration through groundwaters to the sediments in the surface bodies of water. It was possible to conclude that the former irregular waste disposal site is polluting of groundwaters with metals and consequently the sediments of João Correa Stream.