Accumulation of natural SF6 in the sedimentary aquifers of the North China Plain as a restriction on groundwater dating.
We employed environmental tracers ((3)H-(3)He, SF(6)) in a study investigating the groundwater recharge in the North China Plain (NCP), a sedimentary aquifer system consisting of fluvial and alluvial river deposits near the city of Shijiazhuang. The (3)H-(3)He dating method revealed reasonable results for the young groundwater with ages covering the range of recent to ~40 a. SF(6) samples were taken in parallel for independent dating and to compare the applicability of both methods. However, the SF(6)-results are influenced and, in part, dominated by a systematic non-atmospheric component, revealing that the dating with SF(6) is unreliable in this region. A correlation of non-atmospheric SF(6) and (3)H-(3)He ages suggests a continuous accumulation of natural SF(6) in the groundwater of the NCP aquifers. Although terrigenic SF(6) has previously been associated with crystalline or igneous rocks, our results indicate that it can also be accumulated in sandy aquifers on the timescale relevant for SF(6) dating.
von Rohden
Christoph
C
Institute of Environmental Physics, University of Heidelberg, Heidelberg, Germany. christoph.vonrohden@iup.uni-heidelberg.de
Kreuzer
Andreas
A
Chen
Zongyu
Z
Aeschbach-Hertig
Werner
W
D002681:China; D004784:Environmental Monitoring; D019015:Geologic Sediments / Q000032:analysis* / Q000737:chemistry; D006371:Helium / Q000032:analysis; D007554:Isotopes / Q000032:analysis*; D045483:Rivers; D013459:Sulfur Hexafluoride / Q000032:analysis*; D013997:Time Factors; D014316:Tritium / Q000032:analysis; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014881:Water Supply / Q000032:analysis*
D007554:Isotopes; D014874:Water Pollutants, Chemical; D014316:Tritium; D006371:Helium; D013459:Sulfur Hexafluoride