Direct-push profiling of isotopic and hydrochemical vertical gradients

A low-cost and easy to use direct-push method is presented that allows groundwater sampling for isotope and hydrochemical analysis with a depth resolution of 1 m and a final depth in the range of 30 m in unconsolidated sand and gravel aquifers. A trained two-man team can obtain a profile with a dozen different depths within one working day. The technique is demonstrated to provide results for isotope and geochemical studies that are comparable to those from nested multilevel wells, but allow a higher depth resolution and cause smaller hydraulic disturbance of the groundwater system during sampling. The direct-push sampling technique is also shown to give much better results in terms of depth resolution and the identification of geochemical and isotope hydrological gradients than does packer sampling of long-screen wells. Possible applications are the study of geochemical gradients, groundwater age determinations and investigations into recharge processes in unconsolidated aquifers.