Background nacional de sedimento de fundo obtido nos levantamentos geoquímicos de baixa densidade do SGB-CPRM - 2003 a 2017

Abstract

The Geological Survey of Brazil - SGB-CPRM has covered almost 40% of the national territory with low density geochemical survey, started in 2003. More than 15,000 bottom sediment samples were collected by 2017, allowing a statistical study and the production of geochemical maps from 45 elements for 14 Brazilian states, being 10 of them already fully worked. This work aims to define the background ranges of chemical elements, considering median as the central value of the distribution, the quartiles 1 (25% of distribution) and 3 (75% of distribution), which define the interquartile range and the outlier values. The results of these medians were compared to the world’s average values, national legislation and NOOA reference values, being an excellent national reference for concentrations of bottom sediments from rivers, in the fraction lower than 80#, and analyzed by ICP-MS/OES after chemical digestion by hot aqua regia. Although this methodology does not follow the toxic quality determination, it may serve as a guideline for concentration values to be compared to future works, assessing the possible interference processes over time, mainly caused by anthropogenic activities.