Groundwater quality in the Cambrian-Ordovician aquifer system, midwestern United States

Stackelberg, Paul E.

doi:10.3133/fs20173056

Cited by 3 publications

(2 citation statements)

References 4 publications

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“…The MCOAS underlies a large portion of the Midwestern United States, including parts of Minnesota, Iowa, Missouri, Illinois, Indiana, and Wisconsin. More than 630 million gallons per day of groundwater is withdrawn for public and domestic water supply . The Cambrian and Ordovician sedimentary bedrock is largely composed of permeable marine sandstones and carbonate rock; the clastic rocks are typically cemented by calcite (CaCO 3 ) and dolomite ((Ca,Mg)CO 3 ).…”

Section: Materials and Methodsmentioning

confidence: 99%

“…More than 630 million gallons per day of groundwater is withdrawn for public and domestic water supply. 53 The Cambrian and Ordovician sedimentary bedrock is largely composed of permeable marine sandstones and carbonate rock; the clastic rocks are typically cemented by calcite (CaCO 3 ) and dolomite ((Ca,Mg)CO 3 ). In some locations, these permeable and prolific aquifers are separated by locally or regionally confining shale aquitards.…”

Section: Midwestern Cambrian−ordovician Aquifer Systemmentioning

confidence: 99%

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Association of Radionuclide Isotopes with Aquifer Solids in the Midwestern Cambrian–Ordovician Aquifer System

Mathews

Scott²,

Gotkowitz

et al. 2021

ACS Earth Space Chem.

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Groundwater, an important source of drinking water globally, is susceptible to contamination by naturally occurring metals and radionuclides. Regional trends in groundwater quality are useful in predicting the occurrence of contaminants but are difficult to translate to local scales due to complex contaminant–solid phase associations. Here, the aqueous phase of sequential extractions is analyzed using multicollector inductively coupled plasma mass spectrometry techniques to quantify ultratrace radium (Ra) levels in operationally defined fractions of the aquifer solids. Results demonstrate that local-scale geochemistry drives Ra partitioning to groundwater in the U.S. Midwestern Cambrian–Ordovician aquifer system. Analysis of whole-rock extractions indicates that parent and daughter isotope activity ratios indicate that Ra remains close to the site of 238U decay in most stratigraphic units, where the 238U/226Ra ratio is similar to the equilibrium value; however, other stratigraphic units display isotope ratios indicative of Ra leaching. Additionally, Ra varies in prevalence across examined stratigraphy, in both whole-rock and sequential extractions; the average whole-rock 226Ra activity is 70 ± 10 mBq/cm3 in the Maquoketa shale in comparison to 6 ± 1 mBq/cm3 in the St Peter sandstone. This suggests that Ra mobilization depends on both the reactive solid phases present in the stratigraphy and the influence of local geochemical conditions on solid phase–contaminant interactions. Variation in geochemical conditions, such as redox or competitive ion exchange, affects Ra partitioning to groundwater differently across stratigraphy, depending on initial solid-phase associations.

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Section: Materials and Methodsmentioning

confidence: 99%

Section: Midwestern Cambrian−ordovician Aquifer Systemmentioning

confidence: 99%

Association of Radionuclide Isotopes with Aquifer Solids in the Midwestern Cambrian–Ordovician Aquifer System

Mathews

Scott²,

Gotkowitz

et al. 2021

ACS Earth Space Chem.

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Synthesizing multifaceted characterization techniques to refine a conceptual model of groundwater sources to springs in valley settings (Minnesota, USA)

2023

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Springs are commonly used as low-cost monitoring locations to assess groundwater quality and long-term trends. However, spring waters in many settings are a mixture of groundwater sources that range in physical properties and water chemistry. The objective of this work was to determine water sources of springs emerging from the North American midcontinent Cambrian-Ordovician aquifer system at a fish hatchery near Lanesboro, Minnesota (USA), and compare and contrast the sources to shallower and deeper sources. The hydrology of the Lanesboro State Fish Hatchery has been studied for decades using a combination of dye tracing, thermal monitoring, geochemical sampling, and nearby borehole and outcrop observations. Previous studies are integrated with recently collected dye tracing results and geochemical data to develop a comprehensive conceptual model of groundwater flow. Dye trace findings and geochemistry indicate well-developed karst and bedrock fractures in shallowly buried unconfined carbonate formations are important transport pathways to convey anthropogenically influenced waters from the land surface to the hatchery springs. However, borehole dye traces, thermal monitoring, continuous nitrate monitoring, and mixing calculations show that a deeper confined siliciclastic aquifer is responsible for delivering relatively pristine water that accounts for about half of hatchery spring flux. Characterization of the hatchery’s groundwater systems provides fishery managers with information to protect this vital resource and improved context to interpret water-quality-monitoring data that track agricultural contaminants. The methods and results of this study may be widely applicable across a large extent of the Cambrian-Ordovician aquifer system, and to multiaquifer sedimentary bedrock systems elsewhere.

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Strontium and radium occurrence at the boundary of a confined aquifer system

Plechacek

Scott²,

Gotkowitz

et al. 2022

Applied Geochemistry

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Groundwater quality in the Cambrian-Ordovician aquifer system, midwestern United States

Abstract: Area not buried by younger rocks Area buried by younger rocks Low, less than 2.5 pCi/L Moderate, greater than 2.5 pCi/L High, greater than MCL of 5 pCi/L

Cited by 3 publications

References 4 publications

Association of Radionuclide Isotopes with Aquifer Solids in the Midwestern Cambrian–Ordovician Aquifer System

Association of Radionuclide Isotopes with Aquifer Solids in the Midwestern Cambrian–Ordovician Aquifer System

Synthesizing multifaceted characterization techniques to refine a conceptual model of groundwater sources to springs in valley settings (Minnesota, USA)

Strontium and radium occurrence at the boundary of a confined aquifer system

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