Event Title

Heterogeneous Distribution of Arsenic Speciation and Mineralogy Controlling Arsenic in Groundwater

Presenter Information

Xianyu Meng

Location

ECC 216

Event Website

http://water.usu.edu/

Start Date

4-3-2012 5:00 PM

End Date

4-3-2012 5:05 PM

Description

The poisoning of millions of people in West Bengal, Bangladesh and Southeastern Asia from arsenic in groundwater used for drinking water has focused research attention on the sources and geochemistry of arsenic in these humid regions. Few studies however have been performed to determine the source and mechanisms of solubilization of As in semi-arid environments, including at our study area in Cache Valley, Northern Utah. Two continuous cores, from the soil surface to 1.5m below the water table, were collected from an area near the Logan Landfill in order to describe the biogeochemistry that control the solubility of naturally occurring arsenic in continuous cores. To date, general soil properties, pore water chemistry, and solid phase characterization of arsenic have been characterized using chemical extraction procedures. Synchrotron-based X-ray adsorption spectroscopy (XAS) analyses were performed on selected samples to provide oxidation state information of arsenic and fingerprinting of arsenic-hosting mineral phases. Geologic arsenic was present throughout the two profiles. The speciation and mineral association of arsenic changed with depth, with arsenic accumulating in the redox transition zone. Arsenic in the surface soils and depletion zone solids was associated with iron oxides and sulfides, while in the redox transition zone, the majority of arsenic was associated with iron oxides and carbonates. As(III) and As(V) were present throughout the profile with the relative proportions changing with depth. The heterogeneity in the distribution of speciation and mineralogies of arsenic has been proved by the utilization of XAS. The geochemistry of As partially explains the controlling processes affecting arsenic retention and solubilization, which have significant impact on As concentration in the groundwater. Arsenic concentrations exceed the USEPA drinking water limit in groundwater throughout much of the semi-arid Western US, where private wells are common. By knowing the mechanisms of retention and solubilization, the risk of humans exposed to As contaminated groundwater will be decreased.

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Apr 3rd, 5:00 PM Apr 3rd, 5:05 PM

Heterogeneous Distribution of Arsenic Speciation and Mineralogy Controlling Arsenic in Groundwater

ECC 216

The poisoning of millions of people in West Bengal, Bangladesh and Southeastern Asia from arsenic in groundwater used for drinking water has focused research attention on the sources and geochemistry of arsenic in these humid regions. Few studies however have been performed to determine the source and mechanisms of solubilization of As in semi-arid environments, including at our study area in Cache Valley, Northern Utah. Two continuous cores, from the soil surface to 1.5m below the water table, were collected from an area near the Logan Landfill in order to describe the biogeochemistry that control the solubility of naturally occurring arsenic in continuous cores. To date, general soil properties, pore water chemistry, and solid phase characterization of arsenic have been characterized using chemical extraction procedures. Synchrotron-based X-ray adsorption spectroscopy (XAS) analyses were performed on selected samples to provide oxidation state information of arsenic and fingerprinting of arsenic-hosting mineral phases. Geologic arsenic was present throughout the two profiles. The speciation and mineral association of arsenic changed with depth, with arsenic accumulating in the redox transition zone. Arsenic in the surface soils and depletion zone solids was associated with iron oxides and sulfides, while in the redox transition zone, the majority of arsenic was associated with iron oxides and carbonates. As(III) and As(V) were present throughout the profile with the relative proportions changing with depth. The heterogeneity in the distribution of speciation and mineralogies of arsenic has been proved by the utilization of XAS. The geochemistry of As partially explains the controlling processes affecting arsenic retention and solubilization, which have significant impact on As concentration in the groundwater. Arsenic concentrations exceed the USEPA drinking water limit in groundwater throughout much of the semi-arid Western US, where private wells are common. By knowing the mechanisms of retention and solubilization, the risk of humans exposed to As contaminated groundwater will be decreased.

https://digitalcommons.usu.edu/runoff/2012/Posters/12