Open AccessSeasonal dissolved rare earth element dynamics of the Amazon River main stem, its tributaries, and the Curuaí floodplain
Author(s) -
Barroux Gwénaël,
Sonke Jeroen E.,
Boaventura Geraldo,
Viers Jérôme,
Godderis Yves,
Bonnet MariePaule,
Sondag Francis,
Gardoll Sébastien,
Lagane Christelle,
Seyler Patrick
Publication year - 2006
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1029/2006gc001244
Subject(s) - tributary , floodplain , geology , water mass , hydrology (agriculture) , flux (metallurgy) , discharge , rare earth element , environmental science , oceanography , rare earth , drainage basin , mineralogy , chemistry , geography , cartography , geotechnical engineering , organic chemistry
We present a comprehensive dissolved rare earth element (REE) data set for the Amazon River and its main tributaries, Rio Negro, Solimões, and Madeira, as well as the Curuaí floodplain. The two‐year time series show that REE vary seasonally with discharge in each of the tributaries, and indicate a hydrologically dominated control. Upper crust normalized REE patterns are relatively constant throughout the year, with Ce/Ce* anomalies being positively related to discharge. We propose revised annual dissolved REE fluxes to the surface Atlantic Ocean based on an integration of the seasonal data. For Nd (<0.22 μ m) this results in an average flux of 607 ± 43 T/yr, which is at least 1.6 times larger than the previous estimate of 374 T/yr (<0.45 μ m) based on low water stage data. Moreover, during the high water season the maximum Nd flux measures 1277 t.yr −1 , constituting 30% of the required flux to the Atlantic Ocean (Tachikawa et al., 2003). Consequently, a smaller contribution of Nd from atmospheric and river particle desorption is required than was previously suggested. A mass balance of Amazon tributaries and observed fluxes at Óbidos indicates that dissolved LREE behave quasi‐conservatively. Conversely, the HREE mass balance presents a deficit during the high water stages, which could be related to the passage of water through the floodplain system accompanied by solid/dissolved phase transfer.