Evolución geoquímica de las aguas subterráneas en el Valle del Río Piura, subcuenca Chulucanas

Abstract

In the present thesis an approximation was realized to the modeling of the geochemical evolution of the groundwater in the Alto Piura valley, which sought to know the geochemical processes that are given between the underground water and the geological surrounding and like that way to have a better comprehension of the same one and to future to be a tool for the prediction of the chemistry of the underground water in the area of study. Information was compiled and with the analysis of the same one were selected four profiles that were used for the representation of the chemical evolution of the groundwater in the zone of study; and there decided the number and location of the water points of sampling along the mentioned profiles. In the field stage there took fifteen samples of water, of the different wells along hydrogeochemical profiles selected, and they were analyzed by UNI spectrometry laboratory.

From the results interpretation of the chemical analyses of the groundwater, of the geology, of physicochemical principles and calculations of mass balance (geochemical inverse modeling) by means of the program PHREEQC, there proposed an approximate model of the geochemical evolution of the groundwater with the identification of the geochemical dominant processes in the hydrogeological and dynamic context of the area of study.

Between La Peña and Sancor, localities, the formation of quartz, gibbsite, gypsum and the anorthite dissolution, was predicted. In the section of Sancor to Casana, the calculations of modeling predicted the formation of pyrite, goethite and hematite, whereas the minerals that are dissolved are the gypsum, sphalerite, rhodochrosite and Fe(OH)3.

In the section of Casana to Paccha Mn concentration increases above the maximum allowable. In the stretch between the towns of Yapatera and Chulucanas, the found model predicted goethite precipitation and calcite dissolution. The modeling absorption, of heavy metals, in iron oxyhydroxides (FeOOH) showed that there is absorption of Pb and Cd metals. Finally in the section which passes through the city of Chulucanas, the model predicted the dissolution of quartz, anorthite and calcite; and the formation of chlorite and sericite.