Risk evaluation and remedial measures for heavy metal contamination in lagoonal sediments of the Negombo Lagoon, Sri Lanka after the X-Press Pearl maritime disaster

Abstract

Negombo Lagoon is a vital ecological and socio-economic resource in Sri Lanka that has become susceptible to anthropogenic heavy metal contamination. Therefore, short-core sediment samples from the Negombo Lagoon were analyzed to quantify heavy metal contaminants including both metals (Cr, Ni, Co, Cu, Cd, and Pb) and metalloid As; assess their ecological risk; identify critically polluted regions; and to investigate temporal variation in heavy metal concentration. According to the results, Ni is the most abundant heavy metal in lagoonal sediments. Ni, As, and Cr have severely contaminated the sediments as confirmed by their higher geo-accumulation indices (Igeo) and contamination factors (CF). The degree of contamination (Cdeg) indicated an exceedingly high overall heavy metal contamination, and the pollution load index (PLI) exhibited a prominent site quality decline. Individual potential ecological risk factor (Er) values revealed that Ni, As, and Cd pose a substantial ecological risk. Similarly, the potential ecological risk index (PERI) displayed that heavy metal contamination is a significant peril to this ecosystem. Spatial distributions of the heavy metals are governed mainly by the sediment grain size and freshwater influx. Ni concentration in lagoonal sediments has remarkably increased during the last six years (2016–2022) predominantly due to anthropogenic Ni sources, including the recent X-Press Pearl ship accident. In light of the severe heavy metal contamination in lagoonal sediments, the current study recommends a phytoremediation approach for the Negombo Lagoon.