Abstract
Abstract—Sampling techniques with centimeter-scale spatial resolution were applied to investigate biogeochemical processes
controlling groundwater arsenic fate across the groundwater–surface water interface at a site characterized by fine sediments (40%
sand, 46% silt, 14% clay). Freeze-core sediment collection gave more detailed and depth-accurate arsenic and iron contaminant
and microbial distributions than could be obtained with the use of a hand auger. Selective chemical extractions indicated that greater
than 90% of the arsenic was strongly sorbed to very amorphous iron oxyhydroxides. These solids accounted for more than 80%
of the total iron in the sediments. Microbial enrichments indicated that iron-oxidizing bacteria (IOB) were up to 1% of the total
bacterial abundance, whereas iron-reducing bacteria (IRB) were about two orders of magnitude less abundant than IOB. The
abundance of IRB mirrored the IOB depth profile. Push-point pore-water sampling captured large amounts of sediment fines, even
with controlled (20 ml/min) water withdrawal, thereby necessitating filtration before water quality analysis. Bead columns containing
glass media enabled short-term (29 d) characterization of pore water–to–sediment transfer of arsenic and iron. Bead columns
indicated quantitative capture of groundwater arsenic and iron during 2003, suggesting that freeze-core inventories corresponded
to 2 to 20 years of accumulation, depending on location.
Keyword: Sediment pore water,Arsenic,Hyporheos,Landfill,Groundwater
Keyword: Sediment pore water,Arsenic,Hyporheos,Landfill,Groundwater
Original language | English |
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Journal | Environmental Toxicology and Chemistry |
Volume | 25 |
Issue number | 6 |
Pages (from-to) | 1487-1495 |
ISSN | 0730-7268 |
Publication status | Published - 2006 |
Externally published | Yes |