Geochemical evidence for groundwater behavior in an unconfined aquifer, south Florida

摘要: Five well sites have been investigated along an east-west transect across the surfical aquifer system (SAS) of south Florida. Differences between rainfall during wet seasons (June–October) and evaporation dry (November–May) give surface waters this region isotopically light (δ18O −22‰ δD −7.6‰) heavy +4.2‰) compositions, respectively. Surface shallow groundwaters are enriched in 18O D to west, which is consistent with westward decrease equal excess rainfall. In portion SAS (less than 20 m, Biscayne sub-aquifer) heterogeneous stable isotopic compositions occur over short spans time 90 days), reflecting seasonal changes composition recharge rapid flushing. Homogeneous below sub-aquifer, marking zone delayed circulation. Surface calculated from a isotope model agrees previously published estimates 75–95% by physical measurements water budget calculations. This contains many parameters that assumed be mean values, but short-term variability some these may make unsuitable for application yearly values. For Everglades, atmospheric vapor season cause yield anomalous results when annual values used. Chloride-enriched (more 280 mg 1−1) form plume emanating bottom central transect. Elevated chloride concentration ≈ −2‰, −8‰) suggest probably caused not salinity residual seawater aquifer, leakage minor artesian water-bearing Floridan system. Stable groundwater plot close meteoric line, same area as Everglades These interpreted originated Florida 25 000–132 000 years ago, indicating conditions peninsula changed little since late Pleistocene time.