Dinamic of the dissolved organic matter in the Amazone basin: sorption onto mineral surfaces

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4 th Scientific Meeting of the ORE-HYBAM Lima Perou 6 to 11 september 2011 Dinamic of the dissolved organic matter in the Amazone basin: sorption onto mineral surfaces

1 4 th Scientific Meeting of the ORE-HYBAM Lima Perou 6 to 11 september 2011 Dinamic of the dissolved organic matter in the Amazone basin: sorption onto mineral surfaces Marcela Andrea Pérez Pérez (GEO/UFAM Brazil) Marc Benedetti (LGE/IPGP France) Patricia Moreira Turcq (GET/IRD France) M.A.P. Pérez et al. / Chemical Geology 286 (2011)

2 Introduction CO2 CO2 Production Primaire (vegétation aquatique phyto) MO Réspiration (bacteries) N P N P Substances humiques/fulviques

3 Introduction

4 Field sites and sampling

5 Methodology Field operations Água preta Osmose reversa Recuperação fração > 0,22 μm Água branca / fitoplâncton Material dissolvido concentrado Filtração (filtro GF/F) MPS e MOP (> 0,7 μm) MOD (< 0,7 μm)

$fractionation$ and chemical

6 Methodology dissolved organic matter fractionation and chemical analysis - SEC (size exclusion chromatography) - Isotopes (δ 13 C, δ 15 N) - Elemental analysis (C, N)

7 Discussion fate of the dissolved organic matter: processes at work white waters dilution black waters Amazone podzol Negro

8 Discussion fate of the dissolved organic matter: processes at work

9 Adsorption experiments MOP < 63μm Remoção da fase orgânica MOD frações HPO e TPH Matriz mineral BET IV SUVA COD e NT Titulação 13 C e 15 N Protocolo de adsorção sobrenadante SUVA COD e NT

10 Discussion adsorption experiments

11 Discussion selective sorption of organic nitrogen Selective sorption on a peat-humic acid chemical composition (Feng et al., 2005): aromatic and CH 3 signals on the organo-clay complex and CH 2 groups bind preferentially to montmorillonite while carbohydrates and amino acids remain in the supernatant. These explain the difference between our results (absence of nitrogen enrichment after sorption) and the results of Aufdenkampe et al. (2001), that reported preferential sorption of nitrogen rich fractions. This nitrogen enrichment on suspended particles is a dominant characteristic of organic matter in the Amazon River (Williams, 1968; Hedges et al., 1994, 2000), and in other rivers around the world (Lewis et al., 1995). However, our results suggest that the nitrogen enrichment takes place only for a minor part of the total pool of the organic matter since HPO and TPH fractions account for more than 75% of the [DOC].

12 Conclusion This study have shown that in the Amazon watershed, changes in DOC along the river can be accounted by taking into consideration several complementary processes: the mixing between carbon rich and carbon poor waters preferential degradation and fractionation of the organic matter during sorption on sediment or soil material. Lab-scale sorption experiments that utilized field purified organic matter show that: (i) the high molecular weight and aromatic rich compounds will be sorbed preferential by minerals like goethite while (ii) the lower molecular weight and less aromatic compounds will migrate deeper in the soils and reach the higher order streams where later they can interact with suspended clay mineral inducing a second fractionation between dissolved and sorbed organic matter in the lower part of the Amazon basin and in floodplain lakes. The residual negative charge of the dissolved organic matter is a key property of the organic macromolecules that will determine the fate of organic matter issued from pedogenic processes or from in situ production.

13 Recent and future projects Post-PhD DCR-CNPq/FAPEAM ( ) Friendships CARBAMA - ANR ( ) CAPES-COFECUB ( ) Universal MCT-CNPq ( )

14 Rio Uatuma Rio Amazonas Rio Manacapuru Rio Negro Rio Amazonas Rio Urubu Rio Tapajós Rio Solimões Rio Madeira permanent waters open temporary waters flooded forests Martinez and Le Toan 2007.

15 References Aufdenkampe et al., Limnology and Oceanography 46 (8), Feng et al., Organic Geochemistry 36 (11), Hedges et al., Limnology and Oceanography 45 (7), Hedges et al., Limnology and Oceanography 39, Lewis et al., River and Stream Ecosystems. Elsevier, pp Williams, Nature 218,

16 Thank you for your attention

Procedia Earth and Planetary Science 10 ( 2014 ) Geochemistry of the Earth s Surface meeting, GES-10

Available online at www.sciencedirect.com ScienceDirect Procedia Earth and Planetary Science 10 ( 2014 ) 287 291 Geochemistry of the Earth s Surface meeting, GES-10 Hydrological changes in west Amazonia