HR: 16:00h
AN: H14D-01 INVITED    [Abstracts]
TI: Redox Processes and Water Quality of Selected Principal Aquifer Systems
AU: * McMahon, P B
EM: pmcmahon@usgs.gov
AF: U.S. Geological Survey, Denver Federal Center Mail Stop 415, Lakewood, CO 80225, United States
AU: Chapelle, F H
EM: chapelle@usgs.gov
AF: U.S. Geological Survey, 720 Gracern Rd. Suite 129, Columbia, SC 29210, United States
AB: Redox conditions in 15 Principal Aquifer systems across the United States, and their impact on several water- quality issues, were assessed from a large data base collected by the National Water-Quality Assessment (NAWQA) Program of the U.S. Geological Survey. The logic of these assessments was based on the observed ecological succession of electron acceptors such as dissolved oxygen, nitrate, and sulfate and threshold concentrations of these substrates needed to support active microbial metabolism. Similarly, the utilization of solid-phase electron acceptors such as Mn(IV) and Fe(III) are indicated by the production of dissolved manganese and iron. Applying this framework to a number of Principal Aquifers in the United States suggests that the occurrence and distribution of redox processes were controlled largely by climate, geology, hydrology, and anthropogenic factors that, in combination, influenced ground-water residence time and the availability of electron acceptors and donors. For the natural and anthropogenic contaminants assessed in this study, it appears that considering redox conditions as defined by the framework explained many of the observed water- quality trends at the regional scale of this analysis. An important finding of this study is that samples indicating mixed redox processes provide information on redox heterogeneity that affects the observed fate and transport of natural and anthropogenic contaminants and therefore are useful for assessing common water-quality issues.
DE: 1831 Groundwater quality
SC: Hydrology [H]
MN: 2007 Fall Meeting