1. The chemistry of two streams draining kaolinitic soils Daniel Markewitz (Univ. of Georgia) Ricardo Figueiredo (EMBRAPA) Eric Davidson (Woods Hole Research Center) Mercedes Bustamante, Lucilia Parron, and Julio Resende (Univ. de Brasilia)

2. Objectives: To develop a biogeochemical understanding of streams draining watersheds comprised of highly weathered soils in the Amazon and Cerrado. Compare seasonal patterns of cation concentrations.

3. Observation of anomalous patterns of increasing streamwater cation concentrations with increasing stream flow.

5. Mortatti and Probst 2003, Chemical Geology

7. Streams (Igarapés): Cq = Igarapé Cinquenta e quatro St = Igarapé do Sete Pj = Igarapé Pajeú Study Area: Fazenda Vitoria, Paragominas, Para

8. Marques et al., 2003 Geoderma Soilscapes in the Cerrado

9. Gleissolo Haplico Plintossolo Argiluvico Plintossolo Haplico Latossolo Amarelo 0-5760 5-20820 20-40840 40-70860 70-120840 0-10360 10-20440 20-40600 40-60660 60-90440 90-120480 Depth cm Clay g/kg 0-10380 10-20480 20-40580 40-60600 60-90620 90-120600 Microbasin weir Groundwater well Soil profile description (Tarcísio Ewerton Rodrigues, EMBRAPA) Soilscapes in the Eastern Amazon

10. Soil chemical components In soils of the Fazenda Vitoria and the IBGE

11. Stream chemical components in the Fazenda Vitoria and the IBGE Reserve

12. Stage Ht x Concentration relationship for Ca

13. Stability diagram

14. Ternary diagram for silicate weathering

16. Conclusion Soil-stream systems in the IBGE do not present anomalous patterns for cation concentrations. Both soilscapes are in equilibrium will kaolinite and continue to desilicate. Stream cation-anion balances in Fazenda Vitoria are unusually and may be receiving important sea salt inputs.