Sea area Naama Avrahamov 1,2 Orit Sivan 1 , Yoseph Yechieli 2 , Boaz - - PowerPoint PPT Presentation
Characterization and dating of saline groundwater in the Dead Sea area Naama Avrahamov 1,2 Orit Sivan 1 , Yoseph Yechieli 2 , Boaz Lazar 3 1 Department of Geological & Environmental Sciences, Ben Gurion University of the Negev 2 Geological
Characterization and dating of saline groundwater in the Dead Sea area
Naama Avrahamov1,2
Orit Sivan1, Yoseph Yechieli2, Boaz Lazar3
1 Department of Geological & Environmental Sciences, Ben Gurion University
2 Geological Survey of Israel, Jerusalem 3 The Institute of Earth Sciences, The Hebrew University, Jerusalem
Yechieli et al., 2004
Research motivation
Dead Sea level-1960
Groundwater level-1960
2000
2000
Calculating flow rate of the different water bodies in this dynamic system
Research goals
Characterization of these processes for correcting 14C dating and estimating flow rates Using isotopes and chemical water composition for understanding the biochemical processes and carbon system at the fresh and saline groundwater at the Dead Sea area.
Research area
D E A D S E A
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
fresh - saline water interface Rift border faults
W E
... . . ..
gravel sand clay limestone dolomite marl
LEGEND
fresh - saline water interface Upper Cretaceous J udea Group Quaternary sediments
salt
? ?
Hydrological section
Methods
Water sampling
water to a bottle
bailer and submersible pump Analytical methods
electrical conductivity, density
chemistry, alkalinity, δ13CDIC
,14CDIC , CH4, δ13CCH4
Results
100 200 300 400 500 600 2000 4000 6000 8000
Ca (mmol/KgH2O) Cl (mmol/KgH2O)
Groundwater 1980 DS Ein Gedi spring 2007 DS
1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8
TA (meql/KgH2O) DIC (mmol/KgH2O)
a=1 TA=CA+BA
5 2000 4000 6000 8000
δ13CDIC ‰ (PDB) Cl (mmol/KgH2O)
Methane δ13C=(-45) ‰ (This work) Organic matter δ13C≈-23 ‰
(stiller et al 1988)
Carbonate dissolution δ13C≈ (-1) ‰
(This work)
Mixing with other water bodies Carbonate precipitation
(Mook 1968)
SOURCE SINK
Diffusion Advection
Small ε
Isotopic exchange DIC ~ δ13C↑
1 2 3 4 5 6 7 8 2000 4000 6000 8000 Cl (mmol/KgH2O) DIC (mmol/KgH2O) Groundwater Fresh springs 1999 DSW 2003 DS
5 2000 4000 6000 8000
δ13CDIC ‰ (PDB) Cl (mmol/KgH2O)
20‰
0.9mm * 2.75‰ + 0.5mm * X‰ = 1.4mm * (-10.5)‰ 0.9DIC * 2.75‰ + 0.5DIC * -45‰ = 1.4DIC *( -10)‰ Low DIC value with especially light δ13C value Just methane oxidation enables this low δ13C value
Indeed, methane was found in most of the groundwater samples with δ13C of -50‰!!
DSW Saline GW
14C
0.9DIC X 82pMC + 0.5DIC * XpMC = 1.4DIC * pMC
For groundwater samples with low DIC values, methane 14C values have a significant effect on 14CDIC values
0.9DIC X 82pMC + 0.5DIC * 0pMC = 1.4DIC * 52.7pMC 0.9DIC X 82pMC + 0.5DIC * 100pMC = 1.4DIC * 88.4pMC
DSW Saline GW
10 20 30 40 50 60 70 80 90 100 2000 4000 6000 8000
Cl (mmol/KgH2O)
14CDIC (pMC)
Cl (mmol·KgH2O-1)
14CDIC (pMC)
2 1 3
14C values of groundwater at the shore line area can
indicate hydrological connection between the groundwater to the 80’s DS As much as the groundwater become less salty, their 14C values decrease due to mixing processes with fresh groundwater with relativity low 14C values The lower sub-aquifer groundwater are characterized with low 14C values, indicate ancient water presence
methane source and age will be detected
Hyper saline groundwater
14C dating
Isotopic exchange Methane age and source
Dissolved Methane extraction for radiocarbon dating
14C of methane- PreCon scheme
CO2+H2O TRAP
COMBATION 1000oC
CO2 TRAP ←SAMELE ENTER GC→ δ13C ANALASIS →MS AMPOULA He purge
Isotopic exchange in different salinity solutions