Avaliação das Características Químicas, Físicas e Físico-Químicas das Águas Superficiais do Rio Curuá, Caxiuanã, Pará

Abstract

The Caxiuanã region is an area of environmental preservation that has some of the most representative natural ecosystems of the Amazon region. The research aims to characterize the surface waters, through chemical constituents (major and minor dissolved). Field activities started in January 2006 (rainy season) along the Curuá River (RCU) and Caxiuanã Bay (BC) and collections are being performed every month. Eight sampling points were established, seven from surface water and one from the station's supply well. The temperature (0C), pH, electrical conductivity (EC) and dissolved oxygen (DO) were measured in situ. In the laboratory, chemical analyses were performed according to Standard Methods. The temperature ranged from 24.2 to 29.6° C, reflecting the climatic conditions of the period sampled. The pH values were within the range observed for black water rivers. The EC reached a mean value of 16.62 pS/cm in the RCU, 16.43 pS/cm, in the BC and 28.1 pS/cm in the well water. Sulfate had an average value in the RCU of 3.85 mg/L in the BC of 3.97 mg/L and in the well water of 2.29 mg/L. Straight rut values were between 1.99 and 4.99 mg/L in RC; 1.99 and 3.66 mg/L in BC and between 2.59 and 7.59 mg/L in well water. Alkalinity showed low values that are in agreement with pH values. The concentrations found for DO are in agreement with those found for surface waters by Matthes apud Cordeiro (1987). Among the analyzed cations, sodium was the most representative and the ammonium ion was not detected in the samples. The chemical composition of the studied rivers evidences the interaction between the aqueous environment and the geology of the region and the values found for the well water is in accordance with the standards established by Resolution 357 of CONAMA for human consumption.