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Heterogeneous redox conditions, arsenic mobility, and groundwater flow in a fractured-rock aquifer near a waste repository site in New Hampshire, USA

Hydrogeology Journal

By:
, , , , , ,
DOI: 10.1007/s10040-012-0844-4

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Abstract

Anthropogenic sources of carbon from landfill or waste leachate can promote reductive dissolution of in situ arsenic (As) and enhance the mobility of As in groundwater. Groundwater from residential-supply wells in a fractured crystalline-rock aquifer adjacent to a Superfund site in Raymond, New Hampshire, USA, showed evidence of locally enhanced As mobilization in relatively reducing (mixed oxic-anoxic to anoxic) conditions as determined by redox classification and other lines of evidence. Redox classification was determined from geochemical indicators based on threshold concentrations of dissolved oxygen (DO), nitrate (NO3-), iron (Fe2+), manganese (Mn2+), and sulfate (SO42-). Redox conditions were evaluated also based on methane (CH4), excess nitrogen gas (N2) from denitrification, the oxidation state of dissolved As speciation (As(III) and As(V)), and several stable isotope ratios. Samples from the residential-supply wells primarily exhibit mixed redox conditions, as most have long open boreholes (typically 50–100 m) that receive water from multiple discrete fractures with contrasting groundwater chemistry and redox conditions. The methods employed in this study can be used at other sites to gauge redox conditions and the potential for As mobilization in complex fractured crystalline-rock aquifers where multiple lines of evidence are likely needed to understand As occurrence, mobility, and transport.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Heterogeneous redox conditions, arsenic mobility, and groundwater flow in a fractured-rock aquifer near a waste repository site in New Hampshire, USA
Series title:
Hydrogeology Journal
DOI:
10.1007/s10040-012-0844-4
Volume
20
Issue:
6
Year Published:
2012
Language:
English
Publisher:
Springer
Publisher location:
Amsterdam, Netherlands
Contributing office(s):
New Hampshire-Vermont Water Science Center
Description:
13 p.
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
First page:
1189
Last page:
1201
Number of Pages:
13
Country:
United States
State:
New Hampshire