caa a22 4500 445814411 CHVBK 20180317145221.0 cr unu---uuuuu 170323e20110201xx s 000 0 eng 10.1007/s10040-010-0663-4 doi (NATIONALLICENCE)springer-10.1007/s10040-010-0663-4 Age structure and recharge conditions of a coastal aquifer (northern Germany) investigated with 39Ar, 14C, 3H, He isotopes and Ne [Elektronische Daten] [Jürgen Sültenfuβ, Roland Purtschert, Jens Führböter] Age structurel et conditions de recharge d'un aquifère côtier (Allemagne du Nord) étudié avec 39Ar, 14C, 3H, isotopes de He et Ne A tide-influenced two-layer aquifer system in northern Germany was investigated using environmental dating tracers (3H, 39Ar, 14C), the noble gas isotopes 3He, 4He and Ne. The study area is a marshland at the River Ems estuary, exposed to regular flooding untilAD 1000. The construction of dykes, artificial land drainage and groundwater abstraction define the hydraulic gradient. The aquifer depicts a pronounced age stratification with depth. Tritium concentrations above 0.03 TU are found only in the top 30m. Two tritium-free samples between 20 and 30m depth show 39Ar ages of 130 and 250years. Below a clay layer-about 50m below surface level (mbsl)-all analysed samples are 39Ar free and, thus, older than 900years. The initial 14C activities were about 70 pmC. Resulting 14C ages increase with depth and increase up to 9,000years, in agreement with minimal 39Ar ages. Concentrations of radiogenic 4He correlate with 14C ages. Samples in a mid-depth range (20-70 mbsl) show significant gas loss. The gas loss is assigned to recharge in a methane producing environment. Deduced 4He ages were used to assign this water to a infiltration period of about AD 1000. Springer-Verlag, 2010 Coastal aquifers nationallicence Groundwater age nationallicence Radioactive isotopes nationallicence Tracers nationallicence Germany nationallicence Sültenfuβ Jürgen Institute of Environmental Physics, University of Bremen, Otto-Hahn-Allee, 28359, Bremen, Germany aut Purtschert Roland Climate and Environmental Physics, University of Bern, Sidlerstrasse 5, 3012, Bern, Switzerland aut Führböter Jens Leichtweiβ Institute for Hydraulic Engineering and Water Resources, Technical University of Braunschweig, Beethovenstr. 51a, 38106, Braunschweig, Germany aut Hydrogeology Journal Springer-Verlag 19/1(2011-02-01), 221-236 1431-2174 19:1<221 2011 19 10040 https://doi.org/10.1007/s10040-010-0663-4 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s10040-010-0663-4 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Sültenfuβ Jürgen Institute of Environmental Physics, University of Bremen, Otto-Hahn-Allee, 28359, Bremen, Germany aut NATIONALLICENCE 700 1- Purtschert Roland Climate and Environmental Physics, University of Bern, Sidlerstrasse 5, 3012, Bern, Switzerland aut NATIONALLICENCE 700 1- Führböter Jens Leichtweiβ Institute for Hydraulic Engineering and Water Resources, Technical University of Braunschweig, Beethovenstr. 51a, 38106, Braunschweig, Germany aut NATIONALLICENCE 773 0- Hydrogeology Journal Springer-Verlag 19/1(2011-02-01), 221-236 1431-2174 19:1<221 2011 19 10040 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer