Title: Origin of water masses in Floridan Aquifer System revealed by ⁸¹Kr

Abstract

Groundwater in coastal aquifers serves as an essential resource in densely populated areas throughout the world. However, hydrological connection to the ocean leaves it at risk of salinization via changes in climate and hydrological cycles. Therefore, an accurate hydrological characterization of coastal aquifers is of the utmost importance. Although localized salinization of shallow aquifers has commonly been studied, geochemical constraints on the time scale of regional freshwater and seawater in coastal aquifers are limited especially in carbonate aquifers. Such information is not only crucial for water resource management, but also for understanding solute flux over the land-ocean boundary and for interpreting the geochemical signatures that each water mass carries. Toward this goal, we report tracer-based, subsurface residence times of groundwater in the Floridan Aquifer System in southern Florida, which is one of the most productive aquifers on Earth. The first application of ^Kr81-an emerging tracer of old groundwater-to this aquifer has identified freshwater recharge during the last glacial period as anticipated from previous studies using other geochemical tools including radiocarbon, stable isotopes and noble gas concentrations. Moreover, freshwater of Holocene age was also detected at 100 km-distance from the recharge area, suggesting the possibility of an active flow system inmore » the upgradient region. A contribution of fossil seawater that predates the last glacial maximum was locally identified, suggesting slow seawater circulation and limited but significant solute flux from the ocean into the aquifer for dolomitization. This also implies that the deep saline coastal groundwater can potentially serve as a paleo-seawater archive.« less

Authors:

Yokochi, Reika  ^[1];

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Zappala, Jake C. ^[2]; Purtschert, Roland ^[3]; Mueller, Peter ^[2]

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+ Show Author Affiliations

1. Univ. of Chicago, IL (United States). Dept. of the Geophysical Sciences
2. Argonne National Lab. (ANL), Argonne, IL (United States). Physics Division
3. Univ. of Bern (Switzerland). Climate and Environmental Physics, Physics Institute and the Oeschger Centre for Climate Change Research

Publication Date:

Thu Jul 01 00:00:00 EDT 2021

Research Org.:

Argonne National Lab. (ANL), Argonne, IL (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Nuclear Physics (NP); Ben Gurion University -Argonne National Laboratory - University of Chicago Collaborative Water Research Initiative

OSTI Identifier:

1813110

Grant/Contract Number:  

AC02-06CH11357

Resource Type:

Accepted Manuscript

Journal Name:

Earth and Planetary Science Letters

Additional Journal Information:

Journal Volume: 569; Journal ID: ISSN 0012-821X

Publisher:

Elsevier

Country of Publication:

United States

Language:

English

Subject:

58 GEOSCIENCES; 73 NUCLEAR PHYSICS AND RADIATION PHYSICS; Floridan Aquifer System; fossil seawater; groundwater dating; radiokrypton isotopes