CHLOROFLUOROCARBONS (CCL3F AND CCL2F2) AS DATING TOOLS AND HYDROLOGICTRACERS IN SHALLOW GROUNDWATER OF THE DELMARVA PENINSULA, ATLANTIC COASTAL-PLAIN, UNITED-STATES
Sa. Dunkle et al., CHLOROFLUOROCARBONS (CCL3F AND CCL2F2) AS DATING TOOLS AND HYDROLOGICTRACERS IN SHALLOW GROUNDWATER OF THE DELMARVA PENINSULA, ATLANTIC COASTAL-PLAIN, UNITED-STATES, Water resources research, 29(12), 1993, pp. 3837-3860
Concentrations of the chlorofluorocarbons (CFCs) CFC-11 and CFC-12 wer
e determined in groundwater from coastal plain sediments of the Delmar
va Peninsula. CFC-modeled ages were calculated independently for CFC-1
1 and CFC-12, and agreed to within 2-3 years in the majority of the wa
ters. Recharge temperatures, determined from dissolved nitrogen and ar
gon concentrations, varied from 9 +/- 2-degrees-C over most of the pen
insula to 14 +/- 2-degrees-C at the southernmost tip of the peninsula
in Virginia. The CFC-modeled ages were examined in relation to the kno
wn hydrogeologic environment, both on regional scales and in more inte
nsively sampled local scale networks. The CFC-modeled recharge years a
nd measured tritium concentrations were used to reconstruct a tritium
input function that was compared to the modeled tritiUM plus He-3 dist
ribution. Most of the present distribution of tritium in Delmarva grou
ndwater is consistent with low dispersivities. The results of the stud
y strongly support the use of CFCs for dating shallow, aerobic groundw
ater.