Abstract
The present study aims to estimate the residence time of groundwater based on bomb-produced
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Cl.
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Cl/Cl ratios in the water samples are determined by inductively coupled plasma mass spectrometry and liquid scintillation counting.
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Cl/Cl ratios in the groundwater were estimated to be 1.0-2.0 × 10
−12
. Estimates of residence time were obtained by comparing the measured bomb-derived
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Cl concentrations in groundwater with the background reference. Dating based on a
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Cl bomb pulse may be more reliable and sensitive for groundwater recharged before 1975, back as far as the mid-1950s. The above
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Cl background concentration was deduced by determining the background-corrected Dye-3 ice core data from the frozen Arctic data, according to the estimated total
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Cl resources. The residence time of 7.81 × 10
4
y is obtained from extrapolated groundwater flow velocity.
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Cl concentration in groundwater does not reflect the input of bomb pulse
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Cl, and it belongs to the era before 1950.