[en] On May 2019, the members of the Anthropocene Working Group completed a binding vote to affirm some of the key questions that have been agreed in 2016: the Anthropocene should be considered as a formal chronostratigraphic unit, defined by a Global Boundary Stratotype Section and Point (GSSP), using one of the stratigraphic signals around the mid-twentieth century of the Common Era. The fallout from nuclear weapons testing appears as the most suitable GSSP. In this article, the main anthropogenic markers are discussed as well as the sources or human-made radiation and the signature of nuclear weapons testing. The appearance of ^239+240Pu in the early 1950s and the clear peak, in 1963, makes a good marker. High resolution archives include layers of sedimentary rocks, lacustrine and marine sediments and corals and polar ice cores. A coupled application of other radioactive isotopes, as ¹³⁷Cs, ¹⁴C and ²⁴¹Am, may be useful to categorize distinct fallout signatures. A site to define the Anthropocene (golden spike) would ideally be located between 30° and 60° north of the equator. Nevertheless, results obtained in sediments on the Brazilian coast showed that both ^239+240Pu and ¹³⁷Cs signatures could be detected and quantified as markers of this 'atomic age'. (author)

[en] This study investigates the potential factors that contribute to frequent high levels of ozone in Bangu, one of the most critical areas in the city of Rio de Janeiro, regarding ozone levels and air quality. Speciated non-oxygenated volatile organic compounds (VOCs) were measured using method TO-15 (US EPA). The measured concentrations and kinetic and mechanistic analysis of VOC reactivity showed that alkanes were the most important compounds. Ozone concentrations were simulated for a base case representing a day with high ozone levels. Simulated results and statistical multivariate analysis showed that the high ozone concentrations did not seem to be closely related to local emissions but rather were related to pollutant transport and low measured NO_x levels and were triggered by photochemical activity. The differences between weekdays and weekends were also investigated, showing that ozone concentrations were also higher during weekends, mainly on Sunday, when the diesel heavy vehicle fleet was reduced and lower NO emissions were observed. The VOC/NO_x ratios correspond to a VOC-limited process, which leads to higher ozone concentrations under low NO_x conditions.

No abstract available