ISSN = 1980-993X – doi:10.4136/1980-993X www.ambi-agua.net E-mail:
[email protected] Tel.: (12) 3625-4212 Carbon and Nitrogen in the Lower Basin of the Paraíba do Sul River, Southeastern Brazil: Element fluxes and biogeochemical processes (http://dx.doi.org/10.4136/ambi-agua.183) Ricardo de Oliveira Figueiredo1; Álvaro Ramon Coelho Ovalle2; Carlos Eduardo de Rezende2; Luiz Antonio Martinelli3 1Embrapa Meio Ambiente; e-mail:
[email protected] 2Universidade Estadual do Norte Fluminense, Centro de Biociências e Biotecnologia, Laboratório de Ciências Ambientais; e-mails:
[email protected] ;
[email protected] 3Centro de Energia Nuclear na Agricultura, Universidade de São Paulo; e-mail:
[email protected] ABSTRACT The study was conducted in the lower basin of the Paraíba do Sul River (PSR), in which 57,000 km2 of the basin is located in the Brazilian states of São Paulo, Minas Gerais and Rio de Janeiro. We proposed to identify the main sources of C and N fluxes in the PSR waters, to evaluate biogeochemical processes in the watershed, and to estimate C and N riverine loads to the Atlantic Ocean in the context of the sugarcane plantation expansion for ethanol production. Riverine water samples were collected at seven stations along 12 months. Physicochemical and limnological parameters, as well as discharge, were measured together with organic and inorganic C and N species in the dissolved and suspended particulate material. C and N concentrations in bed fluvial sediments, and suspended particulate material were measured, and their elemental ([C:N]a) and isotopic (δ13C) compositions were compared with the [C:N]a and δ13C of the following sources: riparian soils, insular flooded soils, aquatic macrophytes, phytoplankton, pasture grass, sugarcane, sugarcane byproducts, and forest litterfall.