Evaluating behavior of oxygen, nitrate, and sulfate during recharge and quantifying reduction rates in a contaminated aquifer

Environmental Science & Technology
By: , and 

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Abstract

This study evaluates the biogeochemical changes that occur when recharge water comes in contact with a reduced aquifer. It specifically addresses (1) which reactions occur in situ, (2) the order in which these reactions will occur if terminal electron acceptors (TEAs) are introduced simultaneously, (3) the rates of these reactions, and (4) the roles of the aqueous and solid-phase portions of the aquifer. Recharge events of waters containing various combinations of O2, NO3, and SO4 were simulated at a shallow sandy aquifer contaminated with waste fuels and chlorinated solvents using modified push−pull tests to quantify rates. In situ rate constants for aerobic respiration (14.4 day -1), denitrification (5.04−7.44 day-1), and sulfate reduction (4.32−6.48 day-1) were estimated. Results show that when introduced together, NO3 and SO4can be consumed simultaneously at similar rates. To distinguish the role of aqueous phase from that of the solid phase of the aquifer, groundwater was extracted, amended with NO3 and SO4, and monitored over time. Results indicate that neither NO3 nor SO4 was reduced during the course of the aqueous-phase study, suggesting that NO3 and SO4 can behave conservatively in highly reduced water. It is clear that sediments and their associated microbial communities are important in driving redox reactions.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Evaluating behavior of oxygen, nitrate, and sulfate during recharge and quantifying reduction rates in a contaminated aquifer
Series title Environmental Science & Technology
DOI 10.1021/es015615q
Volume 36
Issue 12
Year Published 2002
Language English
Publisher American Chemical Society
Contributing office(s) Toxic Substances Hydrology Program
Description 8 p.
First page 2993
Last page 2700