Evaluation on the risk of contamination by mercury and classification of areas at foz of river Tapajós, Pará, Brazil.

Abstract

Geostatistics is a tool that, in the last years, has been emphasizing in the analysis of spatial data in several areas, especially in the environmental sciences, since it is a technique that presents advantages in relation to other methods of spatial interpolation, mainly, by the possibility of analysis of data in small quantity, informing the errors of estimates and consideration of the anisotropy. In this work, mercury maps were elaborated from spatially distributed data, using Geostatistics to infer results for the location and risk of contamination of this metal along the mouth of the Tapajós River, Santarém-PA. Mercury contamination risk or probability maps were also constructed, which enabled the classification and quantification of the areas contaminated by this metal for several levels of confidence in and around the mouth of the Tapajós River. The methodological procedures will include the use of the "R" program to quantify mercury concentrations in the study area and to map the spatial distribution of these concentrations. To determine the total mercury in the samples, they were submitted to acid digestion and determinations of Hg performed by Atomic Absorption Spectrophotometry with cold steam generation at the Central Laboratory of the State of Pará. Two campaigns were carried out: in July and December 2014, with 37 and 45 sampling points in each one. The results point to a possible contamination of the area in some points, presenting indices above the one recommended by resolution n. 357/2005 of CONAMA.