| Abstract
| - Biogeochemical transformation (inclusive of dissolution)of iron (hydr)oxides resulting from dissimilatory reductionhas a pronounced impact on the fate and transport of nutrientsand contaminants in subsurface environments. Despitethe reactivity noted for pristine (unreacted) minerals, iron(hydr)oxides within native environments will likely havea different reactivity owing in part to changes in surfacecomposition. Accordingly, here we explore the impact ofsurface modifications induced by phosphate adsorptionon ferrihydrite reduction by Shewanella putrefaciens understatic and advective flow conditions. Alterations insurface reactivity induced by phosphate changes theextent, decreasing Fe(III) reduction nearly linearly withincreasing P surface coverage, and pathway of ironbiomineralization. Magnetite is the most appreciablemineralization product while minor amounts of vivianiteand green rust-like phases are formed in systems havinghigh aqueous concentrations of phosphate, ferrous iron, andbicarbonate. Goethite and lepidocrocite, characteristicbiomineralization products at low ferrous-iron concentrations,are inhibited in the presence of adsorbed phosphate.Thus, deviations in iron (hydr)oxide reactivity with changesin surface composition, such as those noted here forphosphate, need to be considered within natural environments.
|
