Machine learning approach for heavy metal source identification and spatial distribution in coastal sediments of
Jesuraja Kamaraj1, Selvam Sekar2, Priyadarsi D Roy3
1National Centre for Earth Science Studies, Thiruvananthapuram, 695011, Kerala, India.
Abstract:
This research focuses on the global issue of heavy metal (HM) contamination in coastal systems and provides the first baseline investigation of the surface sediments in Tiruchendur Taluk, southern Thoothukudi, while evaluating potential sources and associated ecological risks. A total of 25 sediment samples were analyzed for particle size distribution, organic matter content, and the concentrations of heavy metals such as zinc (Zn), copper (Cu), chromium (Cr), lead (Pb), iron (Fe), manganese (Mn), nickel (Ni), and cadmium (Cd). The average concentrations (mg/kg) of the metals were as follows: Zn (76), Cu (36), Cr (9), Pb (17), Fe (1486), Mn (159), Ni (10), and Cd (2.4). The overall median concentrations were in the descending order: Fe > Mn > Zn > Cu > Cd > Pb > Ni > Cr. Fe, Mn, and Zn are mainly associated with natural geogenic inputs (Source 2), whereas Cu, Cd, Pb, and Ni are predominantly linked to anthropogenic activities (Source 1). The measured pollution indices reveal little to no enrichment of most heavy metals in the sediments. However, cadmium (Cd) represents a notable exception, showing considerable enrichment and emerging as the primary contributor to potential ecological risk in the area. To identify potential contamination sources and relative contribution patterns, advanced AI/ML-based statistical models were employed including Non-negative Matrix Factorisation (NMF), Hierarchical Cluster Analysis (HCA), K-means clustering, and Self-Organizing Maps (SOM). The analysis indicates that the metal contaminants are primarily associated with anthropogenic activities such as agricultural runoff (fertilizers and pesticides), industrial effluent discharge from major industrial settings and maritime activities, rather than natural geological processes. Despite the concerning levels of Cd, the overall findings confirm that the Tiruchendur Taluk coastline remains largely pristine with respect to contamination from other heavy metals.
