Radionuclide and heavy metal contamination in the paleobeach groundwater, Cox’s Bazar, Bangladesh: potential impact on environment

Abstract

During the pre-monsoon season (June, 2013), 115 groundwater samples were collected randomly at different depths in Cox’s Bazar paleobeach and its vicinity. The collected samples were analyzed by inductively coupled plasma mass spectrometry (ICP–MS). Studies showed that the higher values of radionuclides (i.e., U, and Th) were observed in the shallow depth of tubewells (5–50-m depth) with ranges of 0.01–9.70 and 0.01–127.10 μg/l, a mean of 0.47 and 1.38 μg/l, and a median of 0.13 and 0.01 μg/l, respectively. Uranium concentration in all drinking water samples was found to below the safe limit of 30 μg/l (WHO, Guidelines for drinking-water quality, 2011). When we compare our measured U contents in the drinking water to the WHO (WHO, Health Criteria and Other Supporting Information – Addendum, 1998) and Japanese drinking water recommendation level of 2 μg/l, we found about 5 % shallow exceeded this limit, although WHO health-based drinking water guidelines were not determined so far for Th. High concentrations of Mn (0.01 to 28.64 mg/l), Fetotal (0.01 to 88.89 mg/l), and B (13 to 969.50 μg/l) were also observed for 87, 60, and 7 % of tubewell water, respectively, some of which exceeded their WHO (WHO, Guidelines for drinking water quality, 2004) drinking water guidelines. Based on the spatial distribution of the tubewells with elevated concentrations of Mn, Fe, B, U, and Th, about 85 % of the study area has been contaminated with at least one of these elements. No direct correlation was found, but a weak positive correlation was observed between the concentrations of radionuclides (i.e., U and Th) belonging to total dissolved solid (TDS), alkalinity as HCO3, and the heavy metals, i.e., Mn, Fetotal, and B. However, the high concentrations of radionuclides along with heavy metals observed particularly in certain areas can be attributed due to interaction of groundwater with the local subsurface geology of the area. Since the radionuclides and heavy metals can have toxic effect and also the levels were considerable to those compared to the WHO drinking water guideline values, the results will serve to arouse public interest and lead to much research on a potential health hazard in the area studied.