Vulnerabilidade de aquíferos: uso dos métodos DRASTIC e GOD na porção norte do complexo industrial e portuário do Pecém, Estado do Ceará

Abstract

This work was carried out in the northern portion of Industrial and Portuary Complex of Pecém, located in Fortaleza Metropolitan Region, Ceará State, Brazil, and aims to evaluate aquifer vulnerability through DRASTIC and GOD methods, and characterization of aquifer pollution hazard. In 2013, four steps of monitoring were made for 24 wells, from which it was possible to identify three main aquifer systems: Dunas, Barreiras and Fraturado. The monitored parameters were: pH, electrical conductivity, total dissolved solids, temperature, salinity, and water table. The pH results allowed classifying the groundwater as acids.Total dissolved solids concentrations are inside of the potability pattern and allowed classifying the groundwater as fresh water. The major acidity and salt concentrations were found during the dry season. The water table has average depth around 5 meters. The DRASTIC method showed indices between very low and very high, with predominance of high and very high vulnerability associated to the Dunas Aquifer, and moderate vulnerability associated to the Barreiras Aquifer. Areas with low and very low vulnerability occur in portions of the Barreiras Aquifer where the water table is most deep, and in the Fraturado Aquifer. Water table, recharge, and vadose zone were the parameters that most influenced these results. The GOD method showed indices between moderate and high, with high vulnerability associated to the Dunas Aquifer, and moderate vulnerability associated to the Barreiras and Fraturado aquifers. Water table was the parameter that most influenced the results of this method. In both methods, the vulnerability mapping showed contours very close to the ones of the geologic map, suggesting strong influence of the lithology in the evaluating process. Activities developed in the area were classified with subsurface contaminant load potential moderate and high. Aquifer pollution hazard obtained by GOD vulnerability and subsurface contaminant load potential indicates the dominance of areas with moderate pollution hazard. The results suggest that aquifer vulnerability and aquifer pollution hazard were underestimated during the construction of the industrial complex, regarding the area where each activity should be building. Comparing both methods, DRASTIC showed better results for studies that requires greater details, as EIAs and Master Plans. The GOD method showed better results for regional studies, as land zonings. The results also reaffirms the environmental fragility of great part of the area intended to the industrial complex, and reinforce the need for monitoring the industrial activities regarding pollution prevention.