Métodos de amostragens de sedimentos em suspensão no Rio Solimões: Estudo de caso na estação de Manacapuru

Abstract

The Amazon basin is an important source of sediments to the Atlantic Ocean, most of this are produced by the Andes mountains, as well as by the local processes of erosion and resuspension. Sediments play an important role in the aquatic richness and biodiversity of the region. In this regard, the starting point for analysis that involves the theme, require the quantification of the Suspended Sediment Concentration (SSC, dry weight of sediment from a known volume of water-sediment mixture, mg l-1). In the Amazon, the Point and Integrated methods are methodologies currently used, however, the data published are inconsistent, presenting significant differences in sampling at the same station. We asked: Which of twice methodologies is more feasible to obtain SCC. We compared these methodologies through the analysis of uncertainties, we focused on the main sources of contribution: sampling, filtration and laboratory. Samples were achieved at the Manacapuru station (Solimões River), resulting in a combined standard uncertainty of 15% for the Point method and 9% for the Integrated method, with sampling being the main source of contribution in both methods. The average concentration of the section obtained with Point method was 29% higher in relation to the Integrated method, nevertheless, observing the concentrations by verticals this difference is greater, reaching 51%. We observed that the Integrated method presented a 64% error, consequence of no sampling sand during the take the samples, being reaffirmed by the absence of sand particles during the granulometric tests. Considering all environmental conditions, operational logistics, and sample quality, we concluded that the Point method is the most adapted to quantification of sediments in larges rivers in the Amazonas region such as Solimões and Amazonas rivers.