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Tracer test with As(V) under variable redox conditions controlling arsenic transport in the presence of elevated ferrous iron concentrations

Journal of Contaminant Hydrology

By:
, , , , , , , , , and
DOI: 10.1016/j.jconhyd.2006.06.001

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Abstract

To study transport and reactions of arsenic under field conditions, a small-scale tracer test was performed in an anoxic, iron-reducing zone of a sandy aquifer at the USGS research site on Cape Cod, Massachusetts, USA. For four weeks, a stream of groundwater with added As(V) (6.7????M) and bromide (1.6??mM), was injected in order to observe the reduction of As(V) to As(III). Breakthrough of bromide (Br-), As(V), and As(III) as well as additional parameters characterizing the geochemical conditions was observed at various locations downstream of the injection well over a period of 104??days. After a short lag period, nitrate and dissolved oxygen from the injectate oxidized ferrous iron and As(V) became bound to the freshly formed hydrous iron oxides. Approximately one week after terminating the injection, anoxic conditions had been reestablished and increases in As(III) concentrations were observed within 1??m of the injection. During the observation period, As(III) and As(V) were transported to a distance of 4.5??m downgradient indicating significant retardation by sorption processes for both species. Sediment assays as well as elevated concentrations of hydrogen reflected the presence of As(V) reducing microorganisms. Thus, microbial As(V) reduction was thought to be one major process driving the release of As(III) during the tracer test in the Cape Cod aquifer. ?? 2006 Elsevier B.V. All rights reserved.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Tracer test with As(V) under variable redox conditions controlling arsenic transport in the presence of elevated ferrous iron concentrations
Series title:
Journal of Contaminant Hydrology
DOI:
10.1016/j.jconhyd.2006.06.001
Volume
88
Issue:
1-2
Year Published:
2006
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Journal of Contaminant Hydrology
First page:
36
Last page:
54