Journal article
Iron and arsenic cycling in intertidal surface sediments during wetland remediation
Environmental Science and Technology, Vol.45(6), pp.2179-2185
2011
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Source: InCites
Abstract
<p>The accumulation and behavior of arsenic at the redox interface of Fe-rich sediments is strongly influenced by Fe(III) precipitate mineralogy, As speciation, and pH. In this study, we examined the behavior of Fe and As during aeration of natural groundwater from the intertidal fringe of a wetland being remediated by tidal inundation. The groundwater was initially rich in Fe<sup>2+</sup> (32 mmol L<sup>−1</sup>) and As (1.81 μmol L<sup>−1</sup>) with a circum-neutral pH (6.05). We explore changes in the solid/solution partitioning, speciation and mineralogy of Fe and As during long-term continuous groundwater aeration using a combination of chemical extractions, SEM, XRD, and synchrotron XAS. Initial rapid Fe<sup>2+</sup> oxidation led to the formation of As(III)-bearing ferrihydrite and sorption of >95% of the As(aq) within the first 4 h of aeration. Ferrihydrite transformed to schwertmannite within 23 days, although sorbed/coprecipitated As(III) remained unoxidized during this period. Schwertmannite subsequently transformed to jarosite at low pH (2−3), accompanied by oxidation of remaining Fe<sup>2+</sup>. This coincided with a repartitioning of some sorbed As back into the aqueous phase as well as oxidation of sorbed/coprecipitated As(III) to As(V). Fe(III) precipitates formed via groundwater aeration were highly prone to reductive dissolution, thereby posing a high risk of mobilizing sorbed/coprecipitated As during any future upward migration of redox boundaries. Longer-term investigations are warranted to examine the potential pathways and magnitude of arsenic mobilization into surface waters in tidally reflooded wetlands.</p>
Details
- Title
- Iron and arsenic cycling in intertidal surface sediments during wetland remediation
- Creators
- Scott G Johnston - Southern Cross UniversityAnnabelle F Keene - Southern Cross UniversityEdward D Burton - Southern Cross UniversityRichard T Bush - Southern Cross UniversityLeigh A Sullivan - Southern Cross University
- Publication Details
- Environmental Science and Technology, Vol.45(6), pp.2179-2185
- Identifiers
- 2259; 991012820988902368
- Academic Unit
- Science; School of Environment, Science and Engineering; Southern Cross GeoScience; Faculty of Science and Engineering
- Resource Type
- Journal article