Allard et al.(2004)による

Allard et al.(2004)による〔『Revealing forms of iron in river-borne material from major tropical rivers of the Amazon Basin (Brazil)』（3079p）から〕

『アマゾン盆地（ブラジル）の主要な熱帯河川からの河川成物質中の鉄の形態を明らかにする』

『Abstract
　The present study deals with the direct determination of colloidal forms of iron in river-borne solids from main rivers of the Amazon Basin. The contribution of different forms of colloidal iron have been assessed using ultrafiltration associated with various techniques including electron paramagnetic resonance spectroscopy (EPR), high resolution transmission electron microscopy (HRTEM), and micro proton-induced X ray emission analysis (μPIXE). EPR shows the presence of Fe³⁺ bound to organic matter (Fe³⁺-OM) and colloidal iron oxides. Quantitative estimate of Fe³⁺-OM content in colloidal matter ranges from 0.1 to 1.6 weight ％ of dried solids and decreases as the pH of the river increases in the range 4 to 6.8. The modeling of the field data with the Equilibrium Calculation of Speciation and Transport (ECOSAT) code demonstrates that this trend is indicative of a geochemical control resulting from the solubility equilibrium of Fe oxyhydroxide phase and Fe binding to organic matter. Combining EPR and μPIXE data quantitatively confirms the presence of colloidal iron phase (min. 35 to 65％ of iron content), assuming no divalent Fe is present. In the Rio Negro, HRTEM specifies the nature of colloidal iron phase mainly as ferrihydrite particles of circa 20 to 50Å associated with organic matter. The geochemical forms of colloidal iron differentiate the pedoclimatic regions drained by the different rivers, corresponding to different major weathering/erosion processes. Modeling allows the calculation of the speciation of iron as mineral, organic and dissolved phases in the studied rivers.』

1. Introduction
2. Geochemical background
3. Samples
4. Material and methods
5. Results
　5.1. Composition of suspended solids
　5.2. EPR of suspended solids: Forms of trivalent iron
　　5.2.1. Identified species
　　5.2.2. Trivalent iron bound to organic matter
　5.3. Quantitative evidence of nano Fe-oxyhydroxides
　5.4. TEM analysis of nano Fe-oxyhydroxides
　5.5. Geochemical modeling of Fe partition
6. Discussion
　6.1. Geochemical significance of colloidal iron in rivers from the Amazon Basin
　6.2. Implications for the stability of ferrihydrite in rivers
7. Conclusions
Acknowledgments
References

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