Análise geoestatística da distribuição de mercúrio e matéria orgânica em sedimentos de fundo da orla do Rio Negro (Manaus - Amazonas)

Abstract

The study of the sediments and their correlation with the environment are an important indicator of the level of contamination because they demonstrate the potential of chemical species accumulation. This global aim of this study was to evaluate the geostatistical distribution of Hg and organic matter in bottom sediments bordering the Rio Negro that surrounds the city of Manaus. The sediment samples were collected in November (2010) and March (2011), corresponding to the beginning and end of the period of flooding in the region, including the four main sub-basins of the city The Educandos, São Raimundo, Tarumã and Puraquequara basins). Sampling locations consisted of twenty points, three points for each of the sub-basins and eight points distributed along the shore of the Rio Negro. The total mercury concentrations were determined by atomic absorption spectrometry coupled to cold vapor generator. The determination of organic matter was performed by the method of ignition. For the geostatistical analysis was used the method of interpolation by ordinary kriging, which were adjusted by the semivariogram, the models evaluated based on cross-validation and preparation of maps of levels, where there was a predominance of the exponential model. The results showed an average concentration of Hg 0:2929mgkg􀀀1 in November and 0:6498mgkg􀀀1 in March, while for the organic matter was of 8.53 % in November and 10.32 % for March. The kriging maps for Hg indicated that besides the contribution of natural Hg in the compartment, is also occurring of anthropogenic influence in the Educandos and São Raimundo basins. The kriging maps for MO showed that its dynamics is controlled by the flood period, occurring in greater accumulation basin of the Acu-Tarumã in November, while a greater dispersion occurred in March.