Schwertmannite stability in wetland soils

Research summary

Schwertmannite is a ferric-oxyhydroxysulfate mineral that forms in acidic, iron- and sulfate-rich waters. As a consequence, it is a very common secondary mineral resulting from sulfide oxidation in rocks, soils and sediments. It has been widely recognized in environments impacted by acid-mine drainage and acid-sulfate soils, where schwertmannite plays a key role in determining water quality trends.

Schwertmannite


Schwertmannite is a common feature of acid-sulfate soil landscapes.

A research stream within Southern Cross GeoScience aims at understanding the stability of schwertmannite in acid-sulfate soil environments. Work completed so far has discovered that the production of ferrous iron by ferric iron-reducing bacteria can catalyse fast transformation of schwertmannite to goethite - a common iron(III) (hydr)oxide. This process has been documented in drain sediment profiles and in re-flooded wetlands, and its rate has been quantified in laboratory-based experiments.

Research activities include in-situ studies on an array of schwertmannite-bearing systems. For example, we have described the in-situ transformation of schwertmannite to goethite in the benthic sediments of acidified coastal waterways. In addition, a range of controlled laboratory-based experiments have been completed, which range from simple closed-system to more complex column-type studies.

Field Studies


Geoscience research integrates field studies with controlled experiments to unravel the controls on schwertmannite stability.

Publications

Burton, E. D., Bush, R. T., Sullivan, L. A., Mitchell, D. R. G. (2008) Schwertmannite transformation to goethite via the Fe(II) pathway: Reaction rates and implications for iron-sulfide formation. Geochimica et Cosmochimica Acta 72, 4551 - 4564.

Burton, E. D., Bush, R. T., Sullivan, L. A., Mitchell, D. R. G. (2007) Reductive transformation of iron and sulfur in schwertmannite-rich accumulations associated with acidified coastal lowlands. Geochimica et Cosmochimica Acta 71, 4456 - 4473.

Burton, E. D., Bush, R. T., Sullivan, L. A. (2006) Sedimentary iron geochemistry in acidic waterways associated with coastal lowland acid sulfate soils. Geochimica et Cosmochimica Acta 70, 5455 - 5468.