Controls on arsenic mobility in contaminated wetland and riverbed streams
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2002.
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| Format: | Thesis |
| Language: | eng |
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Massachusetts Institute of Technology
2005
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| Online Access: | http://hdl.handle.net/1721.1/8144 |
| _version_ | 1826210988638076928 |
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| author | Keon, Nicole E. (Nicole Elise), 1974- |
| author2 | Harold F. Hemond. |
| author_facet | Harold F. Hemond. Keon, Nicole E. (Nicole Elise), 1974- |
| author_sort | Keon, Nicole E. (Nicole Elise), 1974- |
| collection | MIT |
| description | Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2002. |
| first_indexed | 2024-09-23T14:58:37Z |
| format | Thesis |
| id | mit-1721.1/8144 |
| institution | Massachusetts Institute of Technology |
| language | eng |
| last_indexed | 2024-09-23T14:58:37Z |
| publishDate | 2005 |
| publisher | Massachusetts Institute of Technology |
| record_format | dspace |
| spelling | mit-1721.1/81442019-04-12T21:47:47Z Controls on arsenic mobility in contaminated wetland and riverbed streams Keon, Nicole E. (Nicole Elise), 1974- Harold F. Hemond. Massachusetts Institute of Technology. Dept. of Civil and Environmental Engineering. Massachusetts Institute of Technology. Dept. of Civil and Environmental Engineering. Civil and Environmental Engineering. Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2002. Includes bibliographical references. Arsenic mobility and transport in the environment are strongly influenced by associations with solid phases. This dissertation investigates the mechanisms affecting arsenic retention in contaminated wetland and riverbed sediments. A sequential extraction procedure was designed and tested to differentiate solid phase arsenic speciation, including adsorbed As and As coprecipitated with amorphous and crystalline oxides and sulfides. The sequential extraction was performed on Wells G & H wetland (Woburn, MA) sediments, and the inferred As associations were compared to XANES analyses. Geochemical modeling was used to predict redox conditions and As associations. We found that most As in the wetland was adsorbed onto amorphous Fe (hydr)oxide phases. Riverbed sediments differed from wetland sediments in that redox conditions were more reducing, and As was associated with more reducing and crystalline phases, including sulfides. As(lll) and As(V) oxidation states coexist in the wetland and riverbed sediments, with more oxidized As in the wetland. We tested the hypothesis that As associations with more oxidized phases in the wetland may result from wetland plant activities, including root oxygenation in anoxic sediments. We investigated the extent of Fe plaque formation on Typha latifolia roots (cattail), and the mechanism of As sequestration in plaques and (near-root) rhizosphere sediment. The plaque was approximately 30 gm thick, with a strong correlation between As and Fe, as determined by XRF microtomography. Most As was adsorbed, likely to Fe hydroxides in the plaque. (cont.) Root plaque oxidation state maps showed that both As(ll) and As(V) were retained in the plaque, suggesting that the plaque sequesters even the more mobile As(lll) species. Mass balance analysis of As revealed that the plaque was a significant sink of aqueous As. We concluded that the As retained in the Wells G & H wetland is susceptible to redox changes (particularly reduction of Fe hydroxides onto which most As is adsorbed) and displacement by competitive anions. Iron plaque formation on T. latifolia roots was shown to affect As cycling within root zone contaminated sediments by providing a substrate onto which aqueous As can adsorb. by Nicole E. Keon. Ph.D. 2005-08-24T20:42:38Z 2005-08-24T20:42:38Z 2002 2002 Thesis http://hdl.handle.net/1721.1/8144 51850697 eng M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission. http://dspace.mit.edu/handle/1721.1/7582 157 leaves 12061938 bytes 12061688 bytes application/pdf application/pdf application/pdf Massachusetts Institute of Technology |
| spellingShingle | Civil and Environmental Engineering. Keon, Nicole E. (Nicole Elise), 1974- Controls on arsenic mobility in contaminated wetland and riverbed streams |
| title | Controls on arsenic mobility in contaminated wetland and riverbed streams |
| title_full | Controls on arsenic mobility in contaminated wetland and riverbed streams |
| title_fullStr | Controls on arsenic mobility in contaminated wetland and riverbed streams |
| title_full_unstemmed | Controls on arsenic mobility in contaminated wetland and riverbed streams |
| title_short | Controls on arsenic mobility in contaminated wetland and riverbed streams |
| title_sort | controls on arsenic mobility in contaminated wetland and riverbed streams |
| topic | Civil and Environmental Engineering. |
| url | http://hdl.handle.net/1721.1/8144 |
| work_keys_str_mv | AT keonnicoleenicoleelise1974 controlsonarsenicmobilityincontaminatedwetlandandriverbedstreams |