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| Title: | Carbon dioxide-water-rock interaction and hydrogeochemical evolution of thermal and cold ground waters in Wonchi Crater Lake and Ambo- Woliso area. |
| Authors: | HASSEN, SHUBE |
| Advisors: | Seifu Kebede(Dr.) |
| Keywords: | hydrogeochemical evolution
thermal
gaseous
CO2-water-rock interaction
CO2-water-rock interaction
trace element mobility,
Ambo
Woliso
Wonchi Crater Lake |
| Copyright: | May-2011 |
| Date Added: | 24-Jul-2012 |
| Publisher: | Addis Ababa University |
| Abstract: | Isotopic and geochemical data are used to study the hydrogeochemical evolution of thermal and
hypothermal ground waters and CO2-water-rock interaction of ground waters around Wonchi,
Woliso and Ambo area. Geochemical data are classified by Q-mode hierarchical cluster analysis
in to objective groups in order to identify ground waters that have the same hydrogeological and
chemical nature so that to conduct inverse geochemical modeling. HCA classified the water in
to two major groups of high and low TDS and six sub-groups. The waters in the classified
subgroups are similar in chemical composition, geology and the depth in to shallow and deep
aquifer.
Hydrogeochemical evolution of ground waters of the study area is highly influenced by two
regional structures like YTVL and Ambo-Wonchi-Butajira faults that cut across this region.
Thermal and gaseous ground waters of the study area are particularly aligned along these
structures. The CO2 influx to ground waters of the area is due to the deep seated faults that bring
this gas from deep source of metamorphic decarbonation or mantle gas origin. The source of
CO2 gas is suggested by using δ13C isotope indicates high values are in thermal and gaseous
mineral waters of the region. High TDS thermal and gaseous ground waters are characterized by
NaHCO3 in Wonchi and Woliso area while Ambo area is characterized by NaCaHCO3 type
waters. Low TDS ground waters are suggested as shallow and cold ground waters of recharge
area that undergone less water-rock interaction and characterized by δ18O enrichment and
CaHCO3 and CaMgHCO3 water types except in some mixed ground waters. Stable isotope data
indicates that thermal and gaseous ground waters are depleted in δ18O except in Wonchi area
ground waters that shows δ18O enrichment due to hydraulic connection with Lake Wonchi.
The effect of the influx of CO2 to ground waters of this region plays a major role in CO2-waterrock
interaction to be significant and silicate hydrolysis like dissolution and precipitation of
silicate minerals during ground water chemical evolution. Trace element mobility is observed in
high TDS thermal and gaseous ground waters due to strong CO2-water-rock interaction. Heavy
metals that are harmful to the human and environment like Sr, Ba, Mn,Fe and Al are observed in
some thermal and mineral waters of the study area above the permissible concentration of WHO
drinking water standard. |
| Description: | A Thesis Submitted to the School of Graduate Studies of Addis Ababa
University in Partial Fulfillment of the Requirements for the Degree of
Master of Science in Hydrogeology |
| URI: | http://hdl.handle.net/123456789/3468 |
| Appears in: | Thesis - Earth Sciences
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