Arsenic Sequestration by Ferric Iron Plaque on Cattail Roots

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• 作者：Nicole Keon Blute ; Daniel J. Brabander ; Harold F. Hemond ; Stephen R. Sutton ; Matthew G. Newville ; and Mark L. Rivers
• 刊名：Environmental Science & Technology
• 出版年：2004
• 出版时间：November 15, 2004
• 年：2004
• 卷：38
• 期：22
• 页码：6074 - 6077
• 全文大小：277K
• 年卷期：v.38,no.22(November 15, 2004)
• ISSN：1520-5851

文摘

Typha latifolia (cattail) sequesters arsenic within predominantly ferric iron root coatings, thus decreasing mobilityof this toxic element in wetland sediments. Element-specific XRF microtomographic imaging illustrated a highspatial correlation between iron and arsenic in root plaques,with little arsenic in the interior of the roots. XANESanalyses demonstrated that the plaque was predominantlyferric iron and contained approximately 20% As(III) and80% As(V), which is significant because the two oxidationstates form species that differ in toxicity and mobility.For the first time, spatial distribution maps of As oxidationstates were developed, indicating that As(III) and As(V)are both fairly heterogeneous throughout the plaque. Chemicalextractions showed that As was strongly adsorbed inthe plaque rather than coprecipitated. Iron and arsenicconcentrations ranged from 0.03 to 0.8 g Fe g^-1 wet plaqueand 30 to 1200 g As g^-1 wet plaque, consistent with amechanism of As adsorption onto Fe(III) oxyhydroxide plaque.Because this mechanism decreases the concentrationsof both As(III) and As(V) in groundwater, we propose thatdisruption of vegetation could increase the concentrationsof mobile arsenic.