226Ra and 210Pb determination in sediment samples of Santos, São Vicente, Bertioga and Cubatão region.

• Grant number: 08/00679-5
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: May 01, 2008
• End date: April 30, 2009
• Field of knowledge: Physical Sciences and Mathematics - Chemistry - Analytical Chemistry
• Principal Investigator: Barbara Paci Mazzilli
• Grantee: João Messias Júnior
• Host Institution: Instituto de Pesquisas Energéticas e Nucleares (IPEN). Secretaria de Desenvolvimento Econômico (São Paulo - Estado). São Paulo , SP, Brazil

Abstract

The use natural radioactivity in environmental studies is a very important tool to determine the dynamics of both natural and antrophogenic processes in environment. The sediments of lacustrines environments contain a repository of valuable historical information on the temporal changes of industrial pollution. The knowledge of the rate at which sediments have been accumulating is of fundamental importance to the understanding of the anthropogenic fluxes of heavy metals into these environments. 210Pb, member of 238U series, can be used to determine recent sedimentation rates. This element is formed by the decay of 222Rn (half-life of 3.8 days), which diffuses out to the earth's crust to the atmosphere, via a series of short-lived intermediate nuclides to 210Pb. 210Pb is removed from the atmosphere by precipitation and is deposited in the sediments. Consequently, the age of a sediment layer at any particular depth is related to 210Pb activity. This method will be used to determine the sedimentation rates and dating in sediment cores collected in four cities from São Paulo coast, Cubatão, São Vicente, Santos and Bertioga. The results obtained accompanied with metals concentrations and mineralogical composition of the samples will permit establish a historical trends in heavy metal input in the study area from urban or industrial sources.