Back to Search
Start Over
Schwertmannite stability in acidified coastal environments
- Source :
-
Geochimica et Cosmochimica Acta . Jan2010, Vol. 74 Issue 2, p482-496. 15p. - Publication Year :
- 2010
-
Abstract
- Abstract: A combination of analytical and field measurements has been used to probe the speciation and cycling of iron in coastal lowland acid sulfate soils. Iron K-edge EXAFS spectroscopy demonstrated that schwertmannite dominated (43–77%) secondary iron mineralization throughout the oxidized and acidified soil profile, while pyrite and illite were the major iron-bearing minerals in the reduced potential acid sulfate soil layers. Analyses of contemporary precipitates from shallow acid sulfate soil groundwaters indicated that 2-line ferrihydrite, in addition to schwertmannite, is presently controlling secondary Fe(III) mineralization. Although aqueous pH values and concentrations of Fe(II) were seasonally high, no evidence was obtained for the Fe(II)-catalyzed crystallization of either mineral to goethite. The results of this study indicate that: (a) schwertmannite is likely to persist in coastal lowland acid sulfate soils on a much longer time-scale than predicted by laboratory experiments; (b) this mineral is less reactive in these types of soils due to surface-site coverage by components such as silicate and possibly, to a lesser extent, natural organic matter and phosphate and; (c) active water table management to promote oxic/anoxic cycles around the Fe(II)–Fe(III) redox couple, or reflooding of these soils, will be ineffective in promoting the Fe(II)-catalyzed transformation of either schwertmannite or 2-line ferrihydrite to crystalline iron oxyhydroxides. [Copyright &y& Elsevier]
Details
- Language :
- English
- ISSN :
- 00167037
- Volume :
- 74
- Issue :
- 2
- Database :
- Academic Search Index
- Journal :
- Geochimica et Cosmochimica Acta
- Publication Type :
- Academic Journal
- Accession number :
- 45642107
- Full Text :
- https://doi.org/10.1016/j.gca.2009.10.014