Abstract
Abstract The present work is aimed at assessing the aftermath effects of the 2014 flood tragedy on the distribution, pollution status and ecological risks of the heavy metals deposited in the surface river sediment. A series of environmental pollution indexes, specifically the enrichment factor (EF), geo-accumulation index (Igeo), contamination factor (CF), modified degree of contamination (mCd), pollution load index (PLI), potential ecological risk index (PERI) and sediment quality guidelines (SQGs) have been adopted. Results revealed that the freshly deposited sediments collected soon after the flood event were dominated by Cu, Fe, Pb, Ni, Zn, Cr and Cd, with the average concentrations of 38.74, 16,892, 17.71, 4.65, 29.22, 42.36 and 0.29 mg/kg, respectively. According to the heavy metal pollution indexes, Pahang River sediments were moderately to severely contaminated with Pb, Ni, Cu, Zn and Cr, while Cd with the highest risk of 91.09 was the predominant element that illustrated an aesthetic ecological risk to the water body after the tragic flood event. The findings highlighted a critical deterioration of the heavy metals content, driven by the catastrophic flood event, which has drastically altered their geochemical cycles, sedimentary pollution status and biochemical balance of the river's environment.
Highlights
Riverine sediment, which naturally consists of loose sand, clay and soil particles, is a complex mixture of organic and inorganic components, notably silicates, carbonates, sulphide and minerals, deposited at the bottom of the water body by means of precipitation, ion exchange, adsorption, hydrolysis and chelation processes
Field studies along with granulometric analysis of the collected sediment samples showed that the surface sediments of Pahang River were characterized by a high percentage of sand (6–100 wt%, mean 1⁄4 58.9 wt%), and the spatial distribution was more uniform along the river during the ambient condition (Figure 2(a))
The analysis with respect to enrichment factor (EF), Igeo and contamination factor (CF) illustrated that the river sediments were severely accumulated by Pb and Cu, and moderately contaminated by Cr, Cd, Zn and Ni, with the accumulative pollution risks, mCd and pollution load index (PLI) of greater than 1
Summary
Riverine sediment, which naturally consists of loose sand, clay and soil particles, is a complex mixture of organic and inorganic components, notably silicates, carbonates, sulphide and minerals, deposited at the bottom of the water body by means of precipitation, ion exchange, adsorption, hydrolysis and chelation processes. Members of an ill-defined subset of elements, are the main environmental pollutants that are likely to be associated closely with the colloid elements and fine-grained particulates, at the bottom sediment, governed by a complex dynamic set of physical and chemical interactions and equilibria. They originate from the ore formation and weathering of rocks, with toxic, indestructible and non-biodegradable properties, and demonstrate bioaccumulative potential and low self-purification capacity, with high ecological significance to the aquatic environment (Quinn & Dussaillant ). The changing physical–chemical properties of the water sediment have been inferred to be the factor determinant on the heavy metal accumulative behaviour, holding over 90% of the metal content in the aquatic environment, and the presence of Pb, Hg, Zn, Cd and Cu fractions in the polluted sediment were at the magnitude of three times higher than the natural fluxes (Zhang et al )
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