Qualidade das águas subterrâneas rasas do bairro Centro do município de Marituba - PA e sua relação com as principais fontes potenciais de poluição

Abstract

The water crisis is one of the most important social problems of the current decade. Surface water sources are increasingly polluted and groundwater is assuming an important role in human supply. The objective of this work is to analyze the shallow groundwater quality and the geometry of the flows of these waters in the central area of the Marituba district to show their relation with the potential sources of pollution. For this purpose, nineteen groundwater samples were collected from shallow wells in the central district of the municipality of Marituba. Thirty physico-chemical parameters including fifteen heavy metals were analyzed. From the results, tables, graphs and maps of isovalores distributed in the studied area were elaborated. The analyzed waters showed physical and chemical qualities that are not recommended for human consumption. Two parameters are particularly important in this context. The pH values show that, in the rainy season, about 95% of the samples showed pH values outside the drinking water range of Ordinance 2914/11 / MS. While, for the less rainy period, 79% of the samples showed pH values outside the limits of the Ordinance. Fieldwork has shown a great lack of basic sanitation in the area and the discharge of open sewage that can interact through surface runoff with underground springs. Acidic pH values can lead to corrosion in pipes and gastric diseases in humans and are therefore not suitable for human consumption. The other parameter with content above the recommendations of Ordinance 2914/11 / MS is nitrate, with 63.15% of the analyzed samples showing values above 10mg/L. This characterizes these waters as unfit for human consumption and is interpreted as evidence of contamination by liquid effluents (mainly domestic sewage) in the surface waters that interact with the groundwater, added to the presence of septic tank and lack of basic sanitation. All this is added to a shallow static level in these areas, often less than 5 meters and sometimes sub-outcropping. The Piper diagram was constructed and it showed that these waters are characterized as calcium bicarbonated. The study of groundwater flows allowed to identify the influence of potential sources of pollution of the area, with emphasis on a chemical industry existing in the southwest sector of the area. For public supply it is suggested to construct deeper wells that exploit water from confined aquifer units. For this, an alternative water supply proposal for the population of Marituba is presented at the final cost of m³ or 1000 liters of groundwater of R $ 0.124.