摘要
The study was undertaken for understanding the potential of deep aquifers as a source of safe drinking water and for assessing the status of groundwater aquifer near Madunaghat area, Chattogram. The specific issues are salinity, interconnectivity of the shallow and deep aquifers, mixing of groundwater with the adjacent Halda river water, recharge condition and groundwater age. The isotopic data suggest that most of the groundwater results from a mixture between recent recharge and an older component recharge under climatic conditions cooler than at present. The interconnectivity between shallow aquifers and river waters are mostly found in the line wells installed particularly in shallow depth (16 m) close to Halda river as evidenced from the similar tritium values of sampled line well water with that of the Halda river water. The groundwater in Madunaghat well field area is not affected by salinity, as it is evidenced by higher values of Na/Cl ratio of the groundwater samples compared to the sea water fresh water mixing line. The geochemistry of intermediate and deep groundwater is dominated by Na-Mg-HCO<sub>3</sub> and Na-HCO<sub>3</sub> type waters. Even the relationship between chloride and oxygen-18 (Cl-<em>δ</em><sup>18</sup>O) depicts that the waters from the deep, intermediate and shallow wells do not fall on the seawater mixing line. The Carbon-14 contents of intermediate to deep groundwater samples vary from 16.2 to 59.3 pMC indicating the residence time in the range of 4300 to 15,000 years BP, <em>i.e.</em>, the sourced water recharged the aquifers a long time ago. The intermediate and deep wells have water with arsenic concentrations less than the detection limit of 3.0 μg/L. Only a few shallow wells have arsenic concentrations greater than the detection limit varying from 13.7 - 47.4 μg/L, which is less than the DoE permissible limit (50 μg/L) implying that the groundwater at Madunaghat area is not affected by Arsenic contamination.
The study was undertaken for understanding the potential of deep aquifers as a source of safe drinking water and for assessing the status of groundwater aquifer near Madunaghat area, Chattogram. The specific issues are salinity, interconnectivity of the shallow and deep aquifers, mixing of groundwater with the adjacent Halda river water, recharge condition and groundwater age. The isotopic data suggest that most of the groundwater results from a mixture between recent recharge and an older component recharge under climatic conditions cooler than at present. The interconnectivity between shallow aquifers and river waters are mostly found in the line wells installed particularly in shallow depth (16 m) close to Halda river as evidenced from the similar tritium values of sampled line well water with that of the Halda river water. The groundwater in Madunaghat well field area is not affected by salinity, as it is evidenced by higher values of Na/Cl ratio of the groundwater samples compared to the sea water fresh water mixing line. The geochemistry of intermediate and deep groundwater is dominated by Na-Mg-HCO<sub>3</sub> and Na-HCO<sub>3</sub> type waters. Even the relationship between chloride and oxygen-18 (Cl-<em>δ</em><sup>18</sup>O) depicts that the waters from the deep, intermediate and shallow wells do not fall on the seawater mixing line. The Carbon-14 contents of intermediate to deep groundwater samples vary from 16.2 to 59.3 pMC indicating the residence time in the range of 4300 to 15,000 years BP, <em>i.e.</em>, the sourced water recharged the aquifers a long time ago. The intermediate and deep wells have water with arsenic concentrations less than the detection limit of 3.0 μg/L. Only a few shallow wells have arsenic concentrations greater than the detection limit varying from 13.7 - 47.4 μg/L, which is less than the DoE permissible limit (50 μg/L) implying that the groundwater at Madunaghat area is not affected by Arsenic contamination.
作者
Nasir Ahmed
Manzoor Ahamad Choudhry
Mohammed Khaliquzzaman
Arif Ahamed
Mohammad Abdul Quaiyum Bhuiyan
Nipa Deb
Tasrina Rabia Choudhury
Mohammad Masud Karim
Sheikh Mohammad Mahbubur Rahman
Mohammad Murshed Alam
Abul Khair Mohammed Fazlullah
Mohammed Ariful Islam
Nasir Ahmed;Manzoor Ahamad Choudhry;Mohammed Khaliquzzaman;Arif Ahamed;Mohammad Abdul Quaiyum Bhuiyan;Nipa Deb;Tasrina Rabia Choudhury;Mohammad Masud Karim;Sheikh Mohammad Mahbubur Rahman;Mohammad Murshed Alam;Abul Khair Mohammed Fazlullah;Mohammed Ariful Islam(Isotope Hydrology Division, Institute of Nuclear Science and Technology, Bangladesh Atomic Energy Commission, Dhaka, Bangladesh;Isotope Hydrology Section, International Atomic Energy Agency, Vienna, Austria;The World Bank, Dhaka, Bangladesh;Chemistry Division, Atomic Energy Centre, Dhaka, Bangladesh;Institute of Water Modelling, Dhaka, Bangladesh;Chattogram Water Supply and Sewerage Authority, Chattogram, Bangladesh)
