Sources, spatial distribution and risk assessment of metals in tropical estuarine and coastal sediments

This study was conducted in the Miri coastal region of east Malaysia to understand the spatial distribution of metals in sediments and their controlling mechanisms, coupled with the risk assessment. Thirty-three beach and 11 estuarine sediment samples were collected, and analysed for metal concentrations using portable X-ray Fluorescence (pXRF). From the results, the beach sediments exhibited the metal concentrations in the following order: Fe > Ba > Sn > Sr > Cr > Zn > Cd > Pb > Cu > Ni. Whereas, for the estuarine sediments, the following order was observed: Fe > Ba > Sr > Zn > Sn > Cr > Ni > Pb > Cu > Cd. The higher average concentration of Fe in beach (2856.24 mg/kg) and estuarine (16,214.18 mg/kg) sediments indicates riverine inputs through the weathering of source rocks. The spatial distribution maps identified vulnerable hotspots of metal enrichment with respect to different land-use patterns. Principal component analysis (PCA) inferred that the interplay of geogenic processes and anthropogenic sources controls the metal enrichment. Based on the sediment quality pollution indices, cadmium (Cd) and tin (Sn) are the most vulnerable metals in this region, influencing the contamination levels. Health hazard assessment indicates a low risk but requires continuous monitoring due to the elevated matrix levels of Fe (4.38E-02 for children) and Cd (2.48E-05 for adults). This study highlights the occurrence of metal concentrations, posing a considerable ecotoxicological risk in this tropical aquatic ecosystem, which requires effective management strategies to mitigate the metal pollution.