Contamination and Ecological Risk Assessment of Metal(loid)s in Sediments of Two Major Seaports along Bay of Bengal Coast

Abstract

Pollution from shipping, industrial, and municipal wastewater discharges is a major source of heavy-metal contamination at seaports located near estuaries or along the coast. In this study, for the first time, nine metal(loid)s (Pb, Cd, Cr, Cu, Mn, Zn, Ni, Fe, and As) were analyzed from the surface sediment of two major seaports on the Bay of Bengal coast to evaluate the degree of pollution and ecological risk. The average concentrations of metal(loid)s followed the decreasing order of Fe (53,800 ± 4002 mg/kg) > Mn (590 ± 116.8 mg/kg) > Zn (67.59 ± 13.5 mg/kg) > Ni (62.8 ± 22.5 mg/kg) > Cr (36.59 ± 7.22 mg/kg) > Cu (32.63 ± 6.78 mg/kg) > Pb (16.78 ± 3.93 mg/kg) > As (6.33 ± 1.9 mg/kg) > Cd (0.71 ± 0.16 mg/kg). Both sites had much greater Fe concentrations (compared to other metals) than the levels that had been previously recorded at nearby localities. Furthermore, elements such as Fe and Ni surpassed the recommended NOAA and EPA limits for maximum samples from both ports. However, with the exception of one sampling point in Chattogram Port, the pollution-load-index (PLI) values were <1, indicating no heavy-metal contamination. For all metals except Cd, the enrichment factor (EF) values were also <1, indicating that the metals came from natural sources. Besides, the contamination factor (CF) was 1 < CF < 3 for Cd and <1 for other metals, therefore, the study area was under moderate risk for Cd contamination. The geo-accumulation index (Igeo) values indicated that the study area is moderately polluted with Cd (Igeo > 0). In addition, the potential ecological-risk index (PERI) revealed that the both areas are under considerable (PERI > 80) to moderate (PERI > 40) risk due to Cd pollution. Correlation and Principal Component Analyses (PCA), demonstrated the anthropogenic sources of some metals, especially Fe, Ni, and Cd. As a result, it is suggested that the study area should be followed up on, to track changes and design a pollution-control strategy to reduce future pollution hazards.