2023-03-242023-03-242009-11-262009-11-26PARANHOS, Patrícia França. Caracterização hidroquímica do sistema aqüífero Pirabas em Icoaraci, Região Metropolitana de Belém – estado do Pará. Orientador: José Augusto Martins Corrêa. 2009. 94 f. Dissertação (Mestrado em Geoquímica e Petrologia) - Programa de Pós-Graduação em Geologia e Geoquímica. Instituto de Geociências, Universidade Federal do Pará, Belém, 22009. Disponível em:http://repositorio.ufpa.br:8080/jspui/handle/2011/15435 . Acesso em:.https://repositorio.ufpa.br/handle/2011/15435Belém city in northern from Brazil, is located in Pará river mouth. The geology of the area is characterized by a Miocenic sedimentary sequence represented by Pirabas (mainly carbonate) and Barreiras (clastic) Formations. Hydrogeologic system in Belém region is composed of an upper aquifer developed in the Pos-Barreiras sediments and Barreiras rocks with semi-confined character, low hydraulic head aquifers and a lower aquifer system at the deeper parts related to Pirabas rocks. The public water supply from Belém has two services: 1) uses superficial water from Guamá river and 2) groundwater from water bearing Pirabas Formation. The Pirabas aquifer system in Icoaraci district is heavly exploited for public water supply and support several wells with discharge between 150 to 300 m3/h. Hydrochemical investigations of groundwater have been carried out on objectives of evaluating groundwater quality and the possibility of mixtures of waters between the two hydrogeologic systems (Barreiras - upper and more vulnerable and Pirabas – lower vulnerability, best quality). Ten wells were investigated during one hydrological cycle, with monthly samples. The major water quality parameters like temperature, pH, electric conductivity, alkalinity, total dissolved solids, and the major ions were investigated using classical methods. Two main water types (hydrochemical facies) are identified, hydrofacies 1 - Cl—Na dominated with pH ~ 4,0, TDS= 89 mg/L and hydrofacies 2 - HCO3-Ca with pH ~ 7.6 e TDS= 165 mg/L. The mixing of the two water types was confirmed with fingerprint diagrams and composition diagrams. The mixing percentages were calculated with the code AquaChem vs 3.7 (Waterloo Hydrogeologic Inc.) and the results suggest a mixture of 10% of Hydrofacies 1 and 90% Hydrofacies 2. The hydrochemical maps had shown a decrease in the concentration of major elements in the Eduardo Angelim well. It suggests that in this place the mixture of the two waters can be better observed and coincidentally the well is near a normal fault (Costa, 2004). Therefore, the mixture of the two waters systems occurs because the faults cause discontinuities in rock sequences and thus control the water flow. The hypothesis of Costa (2004) was confirmed with the hydrochemical data that help the future development of water public supply.Acesso AbertoAttribution-NonCommercial-NoDerivs 3.0 Brazilhttp://creativecommons.org/licenses/by-nc-nd/3.0/br/Aquífero PirabasFácies hidroquímicasHidrogeoquímicaDissertaçãoCNPQ::CIENCIAS EXATAS E DA TERRA::GEOCIENCIAS::GEOLOGIAMINERALOGIA E GEOQUÍMICAGEOQUÍMICA E PETROLOGIA