Groundwater dating and residence time measurements
A mixture can be a natural result of convergence of flow lines to a discharge area such as a spring or stream, or it can be an artifact of sampling a long-screen well.TRACERMODEL1 contains a worksheet that can be used to determine hypothetical concentrations of atmospheric environmental tracers in water samples with several different age distributions.Applicants should supply (a) a curriculum vitae, including a list of publications, (b) a motivation letter including a statement of past achievement and future research interests and goals (maximum 2 pages) and (c) e-mail address of three references to: [email protected] receive full consideration, all materials must be received by . Groundwater research at ANSTO has provided crucial information to support the management of finite groundwater resources appropriately and sustainably—answering questions about groundwater recharge, groundwater age and dynamics, the interaction between surface water and groundwater and salinisation. Solomon (1997) Recent advances in dating young groundwater: chlorofluorocarbons, ) have relatively long residence times in the atmosphere (44 years, 180 years and 85 years, respectively; Cunnold et al., 1994; Ko and Jackman, 1994), and so their atmospheric concentrations are uniform over large areas, and are steadily increasing.(At the Pacific North West, USA, and South Pole stations, regular measurements of CFC-11 and CFC-12 have been made since 1975; Rasmussen and Khalil, 1986.) Atmospheric concentrations show little spatial variation, with only 10% variation observed between average concentrations in Ireland, Oregon, Barbados, Samoa and Tasmania (Cunnold et al., 1994).Determining the source of groundwater replenishment or recharge, to the aquifer, is the subject of many of Meredith’s collaborative investigations.
As a result of various regulations regarding the use of CFCs, production of CFC-11, CFC-12 and CFC-113 is declining.
It is designed to permit plotting of ages and tracer concentrations in a variety of different combinations to facilitate interpretation of measurements.
TRACERMODEL1 includes several different types of graphs that are linked to the calculations.
Excel workbooks for calculation and presentation of environmental tracer data for simple groundwater mixtures. In: IAEA Guidebook on the Use of Chlorofluocarbons in Hydrology. Atmospheric environmental tracers commonly used to date groundwater on time scales of years to decades include CFC-11, CFC-12, CFC-113, SF6, 85Kr, 3H, and 3H/3H(0), where 3H(0) refers to initial tritium (3H tritiogenic 3He) (Cook and Herczeg, 2000).
Interpretation of age from environmental tracer data may be relatively simple for a water sample with a single age, but the interpretation is more complex for a sample that is a mixture of waters of varying ages.