210Pb sediment dating: Redeeming the history of environmental pollution in the Anthropocene

Abstract

Considering that environmental awareness only developed since 1950, when the period of great acceleration of anthropogenic environmental changes occurred, reference levels in environments heavily subject to the most diverse environmental impacts, such as bays and estuaries, are unknown. In the absence of an environment that can be taken as a reference, the use of sedimentary records is quite useful. Due to the burial process, layer by layer, sediments are considered a historical record of pollution in this type of environment. But to be able to perform this historical reconstruction, there is a need to convert the depth axis, the sedimentary layers, into a time scale. Taking into account the half-life, the best known tools, such as the 14C dating (t½ = 5730 years), are of little application, for this time scale of about 100 years, requiring another natural radionuclide with a more compatible half-life. In this sense, 210Pb (t½ = 22.2 years) appears as an ideal alternative. The present work presents the scientific bases that guide this application, techniques of measurement of 210Pb and models of interpretation of data. Finally, case studies involving different Brazilian ecosystems are presented.