Groundwater provides the largest source of usable water storage in Bangladesh. Groundwater samples have been analyzed for Fe, Mn, Zn, Ni, Cr, Cu, Cd, Pb, and Co using atomic absorption spectrophotometer to evaluate the heavy metal distribution and contamination level at the southeastern coastal area of Bangladesh. Heavy metals in water samples are in the range of Fe (490-4710 µg/L), Mn (13-1970 µg/L), Zn (70-550 µg/L), Ni (42-255 µg/L), Cr (25-133 µg/L), Cu (34-95 µg/L), Cd (7-26 µg/L), Pb (0-20 µg/L), and Co (43-141 µg/L). The mean concentration of Cr, Cd, Fe, Mn, and Ni exceeded the Bangladesh standards for drinking water. Application of Pearson correlation, principal component analysis (PCA), cluster analysis (CA) and hierarchical cluster analysis (HCA) indicate that groundwater of the study area are influenced by both geogenic and anthropogenic sources of the heavy metals. Heavy metal evaluation index (HEI), degree of contamination (C d ) and heavy metal pollution index (HPI) are employed to evaluate the overall pollution level of groundwater estimating 40, 27 and 60% of samples respectively and exhibit the medium degree of pollution.
Beach sands harbor appreciable amount of radioactive elements such as zircon which contains some important and radioactive elements (e.g. uranium, thorium). Very limited quantitative information is available of such elements in the sand of the beaches of Cox's Bazar in Bangladesh. The present study presents application of Neutron Activation Analysis (NAA) to quantify uranium and thorium elemental concentration in zircon assemblages from beach placers of Cox's Bazar. Zircon was separated from beach sands in a mineral processing pilot plant. The separated zircon assemblages were examined by a polarizing petrographic microscope and X-ray diffraction techniques and found that it contained more than 75% pure zircon. Thereafter, uranium and thorium concentrations in zircon were measured by NAA and revealed that zircon contained 94-141 ppm uranium and 127-506 ppm thorium. Therefore, this noticeable amount of uranium and thorium in zircon should be taken in consideration during any mining attempt of the placer minerals present in Cox's Bazar beaches.
Naturally occurring radon-222 was evaluated for its use in estimating annual effective dose exposure in groundwater samples of the southeast coastal area of Bangladesh. On-site radon concentration was measured in groundwater using AlphaGUARD PQ2000 PRO (Saphymo, Germany) radon monitor. The measured values range 0.36–15.70 Bq per l, which lies within the safe limit of 4–40 Bq per l recommended by UNSCEAR. On the contrary, few samples show radon concentration above the safe limit of 11.1 Bq per l recommended by USEPA. The mean annual effective doses due to ingestion and inhalation resulting from radon in groundwater vary from 0.99 to 42.87 μSv per y with an average value of 12.45 μSv per y, which is far below the safe limit 100 μSv per y recommended by WHO and EU. Results reveal that there is no significant public health hazard due to radon ingestion and inhalation from groundwater in the study area.
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