The transport of dissolved organic carbon and nitrogen nutrients in the main channel of the Amazon River, in the Óbidos Strait

Abstract

The present work had done in Amazon River mainstream, at Óbidos Narrow, from January 2012 to December 2016. The samples were carried out monthly with the objective of investigating the seasonal and interannual variations in load of dissolved carbon and nitrogened nutrients in the river. It was observed that the hydrograph phases have an important influence over transport of dissolved constituents in the water of river. At high water phase, dissolved organic carbon (DOC), total dissolved nitrogen (TDN) and dissolved organic nitrogen (DON) increased their transport (being on average 0.096, 0.006 e 0.004  Tg.day^-1 respectively) when compared with low water phase (0.036, 0.003 e 0.001  Tg.day^-1, respectively). Just nitrate (NO₃) did not change through the phases of hydrograph (0.003  Tg.dia^-1). The load of NH₄ was on average 0.0003 Tg.dia^-1 and differences in load were neglected. The results found in present work are close of those one found in literature for Amazon River mainstream. The results show that cover and land use changes can not be observed in large scale yet. Only continuous and uninterrupted monitoring is capable of making a robust assessment of the effect of extreme climate events, as well a possible future changes in climate and cover and use land. Facing increasing changes in the Amazon Basin, studies with a temporal frequency and a wide spatial distribution are necessary.