Browsing by Author "Purtschert, R"

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    Application of stable noble gases, 85Kr and 39Ar to investigate the freshwater lens on Rottnest Island, Western Australia
    (Goldschmidt, 2017-08-13) Kersting, A; Aeschbach, W; Deslandes, A; Meredith, KT; Peterson, MA; Purtschert, R; Suckow, A
    We report on a multi-tracer study of a freshwater lens on Rottnest Island west of Perth (Western Australia). The potable water supply of this carbonate island is entirely based on a shallow freshwater lens ‘floating’ on more saline water. Former studies (Bryan 2016) identified rain as the sole source of the fresh groundwater and that this very vulnerable system is threatened by anthropogenic usage and reduced rainfall due to climate change, causing salt water intrusion.Since the freshwater lens only has a thickness of approx. 20m, even the short screens of the observation wells (1-2m length) cause significant mixing of water of different ages. The combination of tritium (3H) and radiocarbon (14C) used earlier cannot resolve details of the age distribution because of the low values for tritium in precipitation on the southern hemisphere and because of mixing corrosion of the carbonate aquifer together with seawater intrusion changing the initial radiocarbon values. Therefore,this study focussed on the applicationof 85Kr(half-life 10,8yr) and 39Ar (half-life 269yr) as well as the stable noble gases. Here 85Kr complements 3H to resolve the component of very young waterin the age distribution,whereas39Ar fillsthe dating gap between 3H and 14C. The heavy noblegases (Ar, Kr, Xe) can give additional information on the infiltration of freshwater or seawater and 4He can identify admixtures of old water.
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    Groundwater and global palaeoclimate signals (G@GPS)
    (International Union of Geological Sciences, 2016-12-01) Haldorsen, S; van der Ploeg, MJ; Cendón, DI; Chen, JY; Ben Jemâa, NC; Gurdak, JJ; Purtschert, R; Tujchneider, O; Vaikmäe, R; Perez, M; Zouari, K
    Groundwater sources supply fresh drinking water to almost half of the World’s population and are a main source of water for irrigation across world. Characterization of groundwater resources, surfacegroundwater interactions and their link to the global water cycle and modern global change are important themes in hydrogeological research, whereas little attention has been given to the relation between groundwater and past climate variations. A groundwater system’s history is vital to assess its vulnerability under future and potentially adverse climatic changes. The scientific initiative Groundwater and Global Palaeoclimate Signals (G@GPS) investigates major recharge periods of large groundwater aquifers worldwide. We describe the findings for a major basin on each permanently inhabited continent and one with coastal influences in Australia. As palaeo-signals in groundwater are inherently low-resolution records, they can only be related to considerable amounts of recharge. Long periods with substantial groundwater recharge ought to be well identifiable in terrestrial records. Correlation with regional and global climate records may give ideas of the conditions under which such large amounts of recharge were initiated. © The Authors - This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial Licence (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.