Chemical extraction results of aquifer sediments for concentrations of iron and arsenic in different redox zones at the crude-oil spill site near Bemidji, Minnesota
Description
In a crude-oil-contaminated sandy aquifer at the Bemidji site in northern Minnesota, biodegradation of petroleum hydrocarbons has resulted in release of naturally occurring As to groundwater under Fe-reducing conditions. This data set was collected for a study that used chemical extractions of aquifer sediments collected in 1993 and 2011-2014 to evaluate the relationship between Fe and As in different redox zones (oxic, methanogenic, Fe-reducing, anoxic-sub-oxic transition) of the contaminated aquifer over a twenty year period. The data presented showed that 1) the aquifer has the capacity to naturally attenuate the plume of dissolved As, primarily through sorption; 2) Fe and As are linearly correlated in sediment across all redox zones, and a regression analysis between Fe and As reasonably predicted As concentrations in sediment from 1993 using only Fe concentrations; 3) an As-rich “iron curtain,” associated with the anoxic-sub-oxic transition zone, migrated 30 m downgradient between 1993 and 2013 as a result of the hydrocarbon plume evolution; and 4) silt lenses in the aquifer preferentially sequester dissolved As, though As is remobilized into groundwater from sediment after reducing conditions are established.
Resources
| Name |
Format |
Description |
Link |
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55 |
The metadata original format |
https://data.usgs.gov/datacatalog/metadata/USGS.5909fc1be4b0fc4e44916002.xml |
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55 |
Landing page for access to the data |
https://doi.org/10.5066/F7K35RWK |
Tags
- arsenic
- water-chemistry
- sediment-geochemistry
- water-quality
- usgs-5909fc1be4b0fc4e44916002
- biogeochemical-cycling
- biodegradation