Biogeochemical cycling of urea in the aquatic systems of Pindaré and Turiaçu River basins, a pre-Amazonian floodplain, Baixada Maranhense, Brazil

Osamu Mitamura, Nobutada Nakamoto, Maria do Socorro Rodrigues Ibañez, Paulo Roberto Saraiva Cavalcante, José Policarpo Costa Neto, Ricardo Barbieri