Historical Records of Combustion Practices Using Molecular and Isotopic Markers in Sediment Profiles Around Rio de Janeiro, Brazil

Abstract:

The field of combustion processes has transformed lives of mankind throughout history such as the use of wood, initially to produce light and heat; charcoal for using of blast furnaces from the fourteenth century, the coal and petroleum since the time of the Industrial Revolution contribute to the economic growth of many countries. Currently, one of the biggest problems related to combustion processes is connected to the combustion of fossil fuels, due to an increasingly growing of number of vehicles in big cities. The goal of this work is to evaluate the interaction between coastal areas and the Southeast continental shelf of Brazil focusing the exportation of combustion residues from land to ocean and its historical variability. Investigations on the exportation of contaminants such as polycyclic aromatic hydrocarbons (PAHs) and black carbon (BC) from the continent to the ocean; geochronology of the changes in the past through the different uses of combustions and accumulation of contaminants around Southeast of Brazil; advancement in the use of proxies of material transfer in a tropical coastal zone. Three sediment cores were collected, one in highly impacted Guanabara Bay (GB) and other two on the Southeast continental shelf (SB1 and SB2). The sedimentation rate (²¹⁰Pb) for GB is 3.0 cm year^-1 and for SB is 0.17 cm year^-1 up to 5 cm and 0.4 cm year^-1 up to 15 cm of the cores. Preliminaries results for GB are TOC (3.62±0.28%), BC (0.31±0.04%), TN (0.41±0.04%) and Total PAH (4,519±1,245 ng g^-1). For SB1 are TOC (0.72±0.31%), CaCO₃ (18.98±2.84%), TN (0.07±0.051%) and Total PAH (10.4±5.4 ng g^-1). For SB2 are TOC (0.78±0.1%), CaCO₃ (13.9±2.3%), TN (0.08±0.01%) and Total PAH (7.9±3.4 ng g^-1). Further analysis such as aliphatic hydrocarbons to identify the source of the OM and ¹⁴C will be done to calculate the flux of the compounds through the years.