Análise da vulnerabilidade das águas subterrâneas à contaminação na região metropolitana de Maceió

Abstract

The determination of susceptibility to contamination of coastal aquifers provides subsidies for the use and occupation of land. The study made use of concepts derived from DRASTIC methods (ALLER; BENNET; LEHR; PETTY, and HACKETT, 1987), GOD (Foster, 1987) and IS (FRANCÉS; PARALTA; FERNANDES; and RIBEIRO, 2001), to determine the aquifer vulnerability of the metropolitan area of Maceió (RMM). These first two methods to address the inherent vulnerability aquifer, while the IS method checks the degree of human influence on the analyzed area. This latter method is derived from the DRASTIC method, plus the parameter Use and Occupation. On the determination of aquifer vulnerability, DRASTIC method identified two classes of vulnerability, which occupied the Low around 96% of the study area, while the remaining 4% belong to the class of vulnerability faced. The method GOD stands out for using a few parameters and easy to obtain. Being representative for the scale of analysis proposal, obtained four classes of vulnerability, Low vulnerability with in about 91% of its area, 7% Moderate vulnerability, 1.5% Despicable vulnerability and 0.4% of High vulnerability. The IS method has two classes of vulnerability, but one Intermediate occupying about 57.5% of the study area and the remaining 42.5% of High vulnerability. This class occupied mainly urban areas. The validation of vulnerability maps was carried by verifying the quality of groundwater, nitrate via parameter, which accused drinking índices acceptable for human consumption, which is up to 10 mg/L N in 52.12% of cataloged samples or 86 of 165 analyzes. Areas with groundwater use restriction identified, after the crossing of the polluting load and vulnerability maps, are located predominantly in the neighborhoods of Jatiuca until Pontal da Barra, in addition to all the neighborhoods that border the lagoon shore, until reaching the Rio Novo neighborhood. The neighborhoods of Jacintinho, Farol, Feitosa and Pinheiro in Uptown also deserve attention, since it showed high concentrations of nitrate and vulnerability ranging from medium to high. It was verified a strong correlation between the values of nitrates cataloged and areas most vulnerable to contamination, determined by the index IS, which assigns greater weight to areas with high risk of contamination. Both high values are located in urban areas, thus validating not only the vulnerability map IS, but the DRASTIC and GOD who also obtained similar results, but with a lesser degree of vulnerability.