Assessing Heavy Metal Contamination in the Bottom Sediments of Shitalakhya River, Bangladesh; Using Pollution Evaluation Indices and Geo-spatial Analysis

The contamination of riverbed sediments by heavy metals has assumed serious problems due to their toxicity and accumulative behavior. The present study investigated the concentrations of heavy metals from the bottom sediments of Shitalakhya River to understand the level of contamination and their distribution. The average concentrations of heavy metals Al, K, Ca, Mg, Fe, As, Cu, Co, Cr, and Zn are 30432.41, 10929.21, 391139.13, 23148.14, 38697.37, 14.02, 143.69, 13.37, 74.82, and 200.59 mg/ kg respectively in river sediments, and their abundance decreased in the following order: Ca (79.05%)>Fe (7.82%)>Al (6.15%)>Mg (4.68%)>K (2.21%)>Zn (0.04%)>Cu (0.03%)>Cr (0.015%)>As (0.0028%)>Co (0.0027%). In most cases, the mean concentrations of the heavy metals exceed the permissible limit. Significantly higher concentrations of Ca, Mg, Zn, and Cu were found in sediment samples. The heavy metals contaminations in the sediments were also evaluated by applying index of geo-accumulation (I-geo), contamination factor (C-f), degree of contamination (C-d), and pollution load index (PLI) etc. These indices indicated that most of the samples were moderate to strongly pollute by heavy metals and the spatial distribution showed that the northern and southern parts of the study area are more contaminant than middle portion.