Stable Isotopes Studies in the Urucu Oil Province, Amazon Region, Brazil

Abstract

The study area is the Urucu Oil Province, Municipality of Coari, State of Amazonas, Brazil. This research represents a contribution to the hydrogeological knowledge in the northern region of Brazil, particularly in the central part of the Amazon rainforest, where researches on isotopic are still incipient. The primary goal was to determine, by stable isotopes 18 O and 2 H measurements, interrelationships between surface water and groundwater, in order to understand the origin and mechanisms of groundwater recharge and discharge. For this, samples of rainwater, superficial water and groundwater were collected between June 2008 and May 2009 for stable isotopic analyzes. This understanding is important in cases of eventual contaminations of the area, which could degrade the water resources. The results show that the superficial waters are typically light waters and have meteoric origin, and the groundwater recharge is by direct rainfall infiltration with primary evaporation before reaching the groundwater table in the Icá-Solimoes Aquifer System. The isotopic signatures similarities between groundwater and superficial waters indicate both waters’ contributions in the streams and, therefore, in the Urucu river.