Mobility of environmentally significant elements in actual acid sulfate soils, East Trinity, Cairns

Broughton, John , and Lottermoser, Bernd (2006) Mobility of environmentally significant elements in actual acid sulfate soils, East Trinity, Cairns. In: Papers from the Australian Marine Sciences Association 44th Annual Conference and The Society of Wetland Scientists 27th International Conference. p. 18. From: Auslralian Marine Sciences Association 44th Annual Conference and The Society of Wetland Scientists 27th International Conference, 9-14 July 2006, Cairns, QLD, Australia.

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Abstract

Tidal exchange is used to rehabilitate actual acid sulfate soils at East Trinity, Cairns, Queensland. This study reports on the mobility of environmentally significant elements (AI, As, Ba, Co, Cu, Fe, Mn, Ni, Pb,Zn) in actual acid sulfate soils during reflooding. Variations in element concentrations with soil depth were assessed by sampling acrual, reflooded actual and potential acid sulfate soils (AASS, RAASS and PASS, respectively). Samples were geochemically characterised by XRF methods. Laboratory experiments were conducted to establish mobility of elements during PASS oxidation. The isocon technique used mathematical methods to ascertain element losses arid gains during mass transfer processes. Laboratory experiments identified AI, Ba, Ti and Zr as relatively immobile during PASS oxidation. Using Al and Ti as the most suitable immobile element pair, isocon analysis confirmed Ba and Zr immobility in both ASS profiles. In stark contrast, Mn, Co, N i and Zn were lost in significant quantities from the upper parts of the AASS and RAASS profiles, reflecting their pronounced mobility during PASS oxidation. Arsenic, Cu and Pb were enriched in upper parts of both profiles, likely due to limited mobility and subsequent fixation of these elements in topsoils during AASS formation. Iron displayed marked enrichment in the upper part of the AASS profile, but 110 enrichment was observed in the RAASS profile, suggesting a complex pattern of Fe enrichment during AASS formation and remobilization during reflooding. The results demonstrate that individual elements are largely immobile (AI, Ba, Ti, Zr) or mobile (Co, Cu, Mn, Ni, Pb, Zn) during PASS oxidation and that tidal exchange is associated with limited remobilisation of Fe from AASS. Thus, the applied remediation technique at East Trinity inhibits the release of environmentally significant elements; yet the process partly mobilises Fe in AASS by reductive dissolution of ferric oxides upon tidal flooding.

Item ID: 8161
Item Type: Conference Item (Abstract / Summary)
ISBN: 0-9587185-2-0
Date Deposited: 12 Feb 2010 01:09
FoR Codes: 04 EARTH SCIENCES > 0402 Geochemistry > 040202 Inorganic Geochemistry @ 100%
SEO Codes: 96 ENVIRONMENT > 9612 Rehabilitation of Degraded Environments > 961201 Rehabilitation of Degraded Coastal and Estuarine Environments @ 100%
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