Date of Award

4-2004

Degree Name

Doctor of Philosophy

Department

Geosciences

First Advisor

Dr. R. V. Krishnamurthy

Second Advisor

Dr. Carla Koretsky

Third Advisor

Dr. Alan Kehew

Fourth Advisor

Dr. Eliot Atekwana

Abstract

UAE is located at the southeast of Arabian Peninsula. Two main aquifers occupy the study area: the Eastern Gravel Plain and Ophiolite aquifer. Increasing salinity of groundwater and depletion of aquifers are a major concern in the UAE. Previous studies suggest that groundwater, particularly in the Eastern Gravel Plain aquifer, is affected by seawater intrusion and evaporation. Isotopes of oxygen, hydrogen, carbon and chlorine, and chemical analyses were used to investigate this problem in detail. Samples of groundwater from the Eastern Gravel Plain aquifer have R36Cl values in the range of 13.3 to 17.4 x10-15 while those from the Ophiolite aquifer have R36Cl values in the range of 20 to 118 x10-15 . These values indicate the presence of bomb-produced 36Cl and are consistent with recent (post 1950) recharge of most of the samples.

SD - S18O relationship plots on a typical evaporation line, which suggests potential primary and secondary evaporation of the recharging waters prior to infiltration. The R36Cl values of the coastally- bound Eastern Gravel Plain aquifer are lower than the Ophiolite aquifer. Seawater intrusion is absent or minimal based on oxygen-hydrogen isotopes, R36Cl and Cl/Br ratio. Measurements of bromide concentrations support the contention that organically bound Cl is being released into . this environment. Agricultural practices, which are extensive in this region, are a possible source.

Samples of groundwater from Eastern Gravel Plain aquifer have S13C and DIC values in the range of- 10 to -17%0 and 12 to 100 mg C/1 respectively. While samples from Ophiolite aquifer have o 13 C and DIC values in the range of -11 to -16.4%0 and 16 to 114 mg C/1 respectively. The calculated S13C of CO2 source ranges from-16.6 to -24.3%0 and -18.4 to -23.2%0 with an average of -20.5 and -20.8%0 for Eastern Gravel Plain and Ophiolite aquifers respectively. This suggests that the control on DIC is via soil cover vegetated by C-3 and C-4 plants.

Access Setting

Dissertation-Open Access

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