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Natural and Anthropogenic Geochemical Tracers to Investigate Residence Times and Groundwater–Surface-Water Interactions in an Urban Alluvial Aquifer

U.S. Geological Survey, Colorado Water Science Center, Denver Federal Center, P.O. Box 25046, MS-415, Denver, CO 80225, USA
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Academic Editor: Estanislao Pujades
Water 2021, 13(6), 871; https://doi.org/10.3390/w13060871
Received: 25 February 2021 / Revised: 19 March 2021 / Accepted: 20 March 2021 / Published: 23 March 2021
(This article belongs to the Special Issue Urban Groundwater)
A multi-component geochemical dataset was collected from groundwater and surface-water bodies associated with the urban Fountain Creek alluvial aquifer, Colorado, USA, to facilitate analysis of recharge sources, geochemical interactions, and groundwater-residence times. Results indicate that groundwater can be separated into three distinct geochemical zones based on location within the flow system and proximity to surface water, and these zones can be used to infer sources of recharge and groundwater movement through the aquifer. Rare-earth-element concentrations and detections of wastewater-indicator compounds indicate the presence of effluent from wastewater-treatment plants in both groundwater and surface water. Effluent presence in groundwater indicates that streams in the area lose to groundwater in some seasons and are a source of focused groundwater recharge. Distributions of pharmaceuticals and wastewater-indicator compounds also inform an understanding of groundwater–surface-water interactions. Noble-gas isotopes corroborate rare-earth-element data in indicating geochemical evolution within the aquifer from recharge area to discharge area and qualitatively indicate variable groundwater-residence times and mixing with pre-modern groundwater. Quantitative groundwater-residence times calculated from 3H/3He, SF6, and lumped-parameter modeling generally are less than 20 years, but the presence of mixing with older groundwater of an unknown age is also indicated at selected locations. Future investigations would benefit by including groundwater-age tracers suited to quantification of mixing for both young (years to decades) and old (centuries and millennia) groundwater. This multi-faceted analysis facilitated development of a conceptual model for the investigated groundwater-flow system and illustrates the application of an encompassing suite of analytes in exploring hydrologic and geochemical interactions in complex systems. View Full-Text
Keywords: noble gases; stable isotopes; pharmaceuticals; contaminants of emerging concern; groundwater recharge; groundwater-residence time; rare earth elements; principal components analysis noble gases; stable isotopes; pharmaceuticals; contaminants of emerging concern; groundwater recharge; groundwater-residence time; rare earth elements; principal components analysis
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MDPI and ACS Style

Newman, C.P.; Paschke, S.S.; Keith, G. Natural and Anthropogenic Geochemical Tracers to Investigate Residence Times and Groundwater–Surface-Water Interactions in an Urban Alluvial Aquifer. Water 2021, 13, 871. https://doi.org/10.3390/w13060871

AMA Style

Newman CP, Paschke SS, Keith G. Natural and Anthropogenic Geochemical Tracers to Investigate Residence Times and Groundwater–Surface-Water Interactions in an Urban Alluvial Aquifer. Water. 2021; 13(6):871. https://doi.org/10.3390/w13060871

Chicago/Turabian Style

Newman, Connor P.; Paschke, Suzanne S.; Keith, Gabrielle. 2021. "Natural and Anthropogenic Geochemical Tracers to Investigate Residence Times and Groundwater–Surface-Water Interactions in an Urban Alluvial Aquifer" Water 13, no. 6: 871. https://doi.org/10.3390/w13060871

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