Caracterização hidroquímica dos aquíferos freáticos costeiros na cidade de Salinópolis-PA.

Abstract

The city of Salinópolis is located in northeast Pará, Bragantina region, on Pará State. The geology of the area is characterized by a sedimentary cover Tertiary represented by Pirabas Formation , Barreiras Group and overlying these rocks may occur sandy-clay sediments to clay-sand the quaternary called Pós -Barreiras sediments. The main hydrogeological systems Salinópolis, in general, are: a) upper aquifer system developed in the Pós-Barreiras, unconfined aquifers; b) aquifer system Barreiras, unconfined aquifers and semi-confined; c) aquifer system Pirabas, deeper confined aquifers, which is an outcropping aquifer in the region. For the study were registered 22 wells of which 17 shallow wells with depths up to 30 m (PT), two dug wells (AM) and 3 sources (FT). The collection of samples was performed at intervals of two months for a full hydrological cycle, May 2014 to March 2015. The main quality parameters investigated were water temperature, pH, electrical conductivity, alkalinity, total dissolved solids and main ions : cations (Na+, K+, NH4+, Ca2+, Mg2+) and anions (F-, Cl-, NO3- and SO42-). Hydrochemical four groups were identified in the Piper diagram: group 1 (SO4-, Cl- and Na+) that resembles the aquifer Barreiras. In the waters of group 3 rich in calcium and bicarbonate is identified with the Pirabas water aquifer (HCO3- and Ca2+) since the water in groups 2 and 4 showed characteristics of group 1 and 3. From Piper diagrams, it was observed that with increasing water recharge the group 2 and 4 water had a water connection behavior, migrating to another group hydrochemical. In Scholler diagram, even identifying the main ions was possible to see that there are mixtures in water of the same hydrochemical group, visualized by the provision in fan. In Diagram Van Wirdum was identified climate and rocks actions on the aquifers hydrochemistry. Range distribution has been observed that with the beginning of the drought wells located in car washes and near gas stations as well as near the beach and estuarine rivers showed an increase of ions dissolved in the water. As well as in natural sources or springs there was a large increase in number of ions, especially the sulfate Climate Influence, rock, ocean waters, estuarine rivers, as well as the contribution of the aquifer Barreiras and Pirabas showed a peculiar hydrochemical composition in the waters of aquifers shallow coastal city in Salinópolis.