Nazim-Ud Doulah, M Rezaul Karim, Shahadat Hossain, Nipa Deb and Bijoy Sonker Barua
Concentrations of selected heavy metals (Zn, Cu, Pb, Cd, Fe, Mn, and Ni) in surface and sub-surface sediments were studied with an attempt to establish a base-line data of their concentration in the sediments of the coastal area of Kutubdia Island, Cox’s Bazar, Bangladesh. Sediment sample of twelve different sites were collected and taken for open plate digestion technique (HNO3). The concentration of heavy metals was analyzed using Flame Atomic Absorption Spectrophotometer (FAAS). The concentration of Cu, Fe, Mn, Pb and Ni in the sediment samples was higher than the proposed Threshold Effect Level (TEL). The observed concentrations of the metals varied in different sampling sites and also in surface to sub-surface. The decreasing trend of metals were observed in surface and sub-surface sediments as Fe>Mn>Ni>Cu>Pb>Zn>Cd. Geoaccumulation Index (I-geo) indicates that the sediment in the studied stations were unpolluted (grade 0) with respect to Cu, Pb, Fe, Zn and Cd whereas concentration of Mn indicated slight pollution in three stations. Contamination Factor (CF) values showed low to moderately pollution in studied stations. The values of Pollution Load Index (PLI) for the samples collected from all the stations were found less than one, indicating perfection except one study area was the hot spot. The Enrichment Factor (EF) indicates that the metal in the sediment of studied stations were entirely from crustal minerals whereas the sources of Mn are may be anthropogenic. However, the elevated level of some toxic elements was found in this investigation alarming about the natural balance of the area. Constant monitoring of the coastal area of Kutubdia Island, Cox’s Bazar, Bangladesh is needed with a view to minimize the health risk of the population as well as the detrimental impacts on the aquatic ecosystem.
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