1. Conceptualization of the recent change in groundwater quality of the shallow aquifer of the hydrocarbon-rich Barmer sedimentary basin, Rajasthan, India.
- Author
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Kumar, Ashok
- Subjects
GROUNDWATER quality ,SEDIMENTARY basins ,AQUIFERS ,GAS migration ,HYDROGEN sulfide ,LIGNITE ,GEOLOGICAL carbon sequestration - Abstract
This paper conceptualises the factors responsible for water quality change in the aquifer on the basis of a study of flow dynamics, hydro-chemical, and bacteriological processes in a gypsum, lignite, oil, and gas-rich Barmer sedimentary basin in India. The change in colouration, odour, and presence of gases in flowing wells has been analysed. The study revealed that such a change in the quality of the water is mainly occurring in those wells that are located in the transition zone between unconfined and confined parts of the same aquifer. The field and lab analyses have further revealed the presence of pyrites, other iron-rich minerals, hydrogen sulphide (H
2 S), carbon dioxide (CO2 ), and methane (CH4 ) gases in the aquifer. The study suggests that changes in flow dynamics, hydro-chemical equilibrium, and microbiological processes like sulphate reduction, methanogenesis, and reverse methanogenesis are responsible for such changes in groundwater quality. The change in water quality in the unconfined parts of the aquifer is mainly due to in situ pyrite dissolution, bacteria-mediated sulphate reduction, or reverse methanogenesis taking place in the nearby confined parts of the aquifer. The presence of CH4 in non-flowing wells or while drilling new wells appears to be biogenic in nature and has migrated from deeper, confined parts of the same aquifer. The overexploitation of the aquifer has changed the flow dynamics and hydro-chemical equilibrium within the aquifer, and it has prompted the migration of gases from deeper, confined parts of the same aquifer. The water quality change is more prominent in the transitional zone between unconfined and confined parts of the aquifer. [ABSTRACT FROM AUTHOR]- Published
- 2023
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