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GEOREF RECORD

CO (sub 2) outgassing in a combined fracture and conduit karst aquifer near Lititz Spring, Pennsylvania

Laura Toran and Eric Roman
CO (sub 2) outgassing in a combined fracture and conduit karst aquifer near Lititz Spring, Pennsylvania (in Perspectives on karst geomorphology, hydrology, and geochemistry; a tribute volume to Derek C. Ford and William B. White, Russell S. Harmon (editor) and Carol M. Wicks (editor))
Special Paper - Geological Society of America (2006) 404: 275-282

Abstract

Lititz Spring in southeastern Pennsylvania and a nearby domestic well were sampled for 9 months. Although both locations are connected to conduits (as evidenced by a tracer test), most of the year they were saturated with respect to calcite, which is more typical of matrix flow. Geochemical modeling (PHREEQC) was used to explain this apparent paradox and to infer changes in matrix and conduit contribution to flow. The saturation index varied from 0.5 to 0 most of the year, with a few samples in springtime dropping below saturation. The log P (sub CO2) value varied from -2.5 to -1.7. Lower log P (sub CO2) values (closer to the atmospheric value of -3.5) were observed when the solutions were at or above saturation with respect to calcite. In contrast, samples collected in the springtime had high P (sub CO2) , low saturation indices, and high water levels. Geochemical modeling showed that when outgassing occurs from a water with initially high P (sub CO2) , the saturation index of calcite increases. In the Lititz Spring area, the recharge water travels through the soil zone, where it picks up CO (sub 2) from soil gas, and excess CO (sub 2) subsequently is outgassed when this recharge water reaches the conduit. At times of high water level (pipe full), recharge with excess CO (sub 2) enters the system but the outgassing does not occur. Instead the recharge causes dilution, reducing the calcite saturation index. Understanding the temporal and spatial variation in matrix and conduit flow in karst aquifers benefited here by geochemical modeling and calculation of P (sub CO2) values.


ISSN: 0072-1077
EISSN: 2331-219X
Coden: GSAPAZ
Serial Title: Special Paper - Geological Society of America
Serial Volume: 404
Title: CO (sub 2) outgassing in a combined fracture and conduit karst aquifer near Lititz Spring, Pennsylvania
Title: Perspectives on karst geomorphology, hydrology, and geochemistry; a tribute volume to Derek C. Ford and William B. White
Author(s): Toran, LauraRoman, Eric
Author(s): Harmon, Russell S.editor
Author(s): Wicks, Carol M.editor
Affiliation: Temple University, Department of Geology, Philadelphia, PA, United States
Affiliation: U. S. Army Research Office, Environmental Sciences Division, Research Triangle Park, NC, United States
Pages: 275-282
Published: 2006
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
ISBN: 978-0-8137-2404-1
ISBN: 0-8137-2404-7
References: 25
Accession Number: 2006-075423
Categories: Hydrogeology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sketch maps
N40°08'05" - N40°11'27", W76°22'30" - W76°16'15"
Secondary Affiliation: University of Missouri-Columbia, USA, United StatesNew Jersey Geological Survey, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 200643
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