Assessment of heavy metal contamination in sediment at the newly established tannery industrial Estate in Bangladesh: A case study

Abstract

This research work was focused to evaluate the concentration of heavy metals ( i.e. , Cr, Pb, Mn, Cu and Fe) in sediment samples collected from the Dhaleshwari River near the area of a newly established tannery industrial estate, Savar, Bangladesh. The heavy metals in sediment samples were ascertained by the atomic absorption spectrophotometer (AAS). This study revealed that the metal concentration for chromium (Cr), lead (Pb), manganese (Mn), copper (Cu) and iron (Fe) were found to be 14.8–748 (186 ± 241) mg/kg, 2.38–21.1 (8.78 ± 6.15) mg/kg, 1.59–6.29 (3.12 ± 1.38) mg/kg, 0.36–4.75 (1.76 ± 1.47) mg/kg and 3.87–154 (42.7 ± 49.1) mg/kg (dry wt) respectively. The concentration of heavy metals in sediment samples descends with the following order: Cr > Fe > Pb > Mn > Cu. Sediment contamination was assessed on the basis of geo-accumulation index ( I geo ), contamination factor ( CF ) and pollution load index ( PLI ). The average I geo values for Cr, Pb, Mn, Cu and Fe were found to be (−0.44 ± 1.87), (−2.18 ± 1.20), (−8.80 ± 0.63), (−5.80 ± 1.36) and (1.59 ± 1.87) respectively. The I geo values values of Cr and Fe for some sampling stations were found to be higher. The PLI value for all the sample stations (S1-S8) were 0.58, 0.66, 0.71, 0.69, 0.88, 0.86, 0.83 and 0.83 correspondingly. The CF values for Cr and Fe in some stations was observed at moderate, considerate and high contamination level. The spatial distribution of heavy metals in the study area was presented by interpolation technique. The results of spatial distribution pattern showed that the high concentrated zones of Cr was found at the dumping zone (~S5) of the leather industrial city. On the other hand, the spatial distribution pattern for the studied metals (Pb, Mn, Cu and Fe) showed that the maximum metals concentrations were found in the southeastern part, which was nearby effluent dumping zone. The ecological risk assessment in sediment samples revealed that there is no significant risk observed by the metal( oid )s at this moment. Considering Cr concentration, the modified hazard quotient ( mHQ ) showed that about 75% of the samples were low to severely polluted by Cr, while 25% of the samples were extremely polluted by Cr as well as mHQ ≤ 3.5. Based on PMF analysis, two potential sources of heavy metals were identified in the study region: first, biochemical and leather tanning industries (Cr); second, the mixed effect of geogenic sources and atmospheric deposition and traffic emission (Fe and Pb). • The conc. for Cr, Pb, Mn, Cu and Fe in sediment samples were determined by AAS. • The concentration of heavy metals in sediment descends Cr > Fe > Pb > Mn > Cu • Spatial distribution pattern showed that the high Cr conc was found at the dumping zone • There is no significant ecological risk was observed by the metal( oid )s in the study area. • PMF analysis revealed two potential sources of heavy metals in the study region