Conditions redox hétérogènes, mobilité de l’arsenic et écoulement souterrain dans un aquifère de roches fracturées près d’un site de décharge du New Hampshire, USA Condiciones redox heterogéneas, movilidad del arsénico y flujo de agua subterránea en un acuífero de roca fracturada cerca de un sitio repositorio de residuos en New Hampshire, EEUU 美国新罕布什尔州一废弃处置场附近的裂隙含水层中非均质氧化还原条件,砷的迁移性和地下水流 Condições de redox heterogéneas, mobilidade de arsénio e fluxo subterrâneo num aquífero fraturado nas vizinhanças de um aterro de resíduos em New Hampshire, EUA

Harte, Philip T.; Ayotte, Joseph D.; Hoffman, Andrew J.; Revesz, Kinga M.; Belaval, Marcel; Lamb, Steven; Bohlke, J. K.

Conditions redox hétérogènes, mobilité de l’arsenic et écoulement souterrain dans un aquifère de roches fracturées près d’un site de décharge du New Hampshire, USA Condiciones redox heterogéneas, movilidad del arsénico y flujo de agua subterránea en un acuífero de roca fracturada cerca de un sitio repositorio de residuos en New Hampshire, EEUU 美国新罕布什尔州一废弃处置场附近的裂隙含水层中非均质氧化还原条件,砷的迁移性和地下水流 Condições de redox heterogéneas, mobilidade de arsénio e fluxo subterrâneo num aquífero fraturado nas vizinhanças de um aterro de resíduos em New Hampshire, EUA | Heterogeneous redox conditions, arsenic mobility, and groundwater flow in a fractured-rock aquifer near a waste repository site in New Hampshire, USA

2012

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 (NO 3 – ), iron (Fe2+), manganese (Mn2+), and sulfate (SO 4 2– ). 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.

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