2012 NGWA Ground Water Summit: Innovate and Integrate

Geomicrobiological Aspects of Gachsaran FORMATION AFFECTED the Hydrochemistry of Garo SPRINGS and Tembi RIVER

Monday, May 7, 2012
Moslem Papizadeh, Academic Center for Education, Culture and Research (ACECR);

Tembi River, the most saline water stream of Khuzestan province is in the class C4-S4. Sulfide springs of Garo are introduced into the River at Golgir region. At Golgir, Asmari oil reservoir is very near to the surface and many natural oil seepages are detected at this region that resulted in hydrocarbon pollution of Tembi River as chromatography analysis showed. Gachsaran formation is the evaporite and gypsum based cap rock of Asmari reservoir and Garo springs are located on Gachsaran formation that is rich in gypsum. As XRF analysis showed Gachsaran formation is rich in As, V, Fe, Ni, and concentrations of these elements were detected in Garo springs and Tembi water samples (ICP-OES and atomic absorption analysis). Vanadium, arsenic and nickel are between the metals are present in crude oil and they may be released by microbial biodegradation of crude oil into the ground water. Investigation of ferric and arsenate reducing bacteria showed that sulfate reducing bacteria are active in such metabolic pathways. Also, most probable number counting of water and sediment samples of Garo springs and a control spring at Golgir region showed a high activity of Arsenate, ferric and sulfate reducing bacteria, but a very low activity of nitrate and nitrite reducing bacteria is present in the Garo springs water and sediment samples. It is concluded that the oil seepages, sulfate availability, no detectable nitrate caused a natural enrichment of sulfate reducing bacteria and caused high sulfide production  and a very reducing condition (Eh: -1.9). It could be the main cause of high hydrogen sulfide level of Asmari reservoir and the deviation of microbial community to the sulfate reducing metabolism at Garo springs, a phenomenon that is not significantly detectable anywhere else along Tembi River.