Assessment of Trace Metal Pollution in Surface Sediments from Southwestern Part of Bay of Bengal, India

Abstract

Twenty-nine shelf sediment samples have been collected from the Southwestern part of the Bay of Bengal in 5 transects lying offshore between the coasts of Cuddalore and Nagapattinam district, Tamil Nadu, India. Collected samples were analyzed for sediment texture, organic matter (OM), and trace metals (Fe, Cu, Co, Mn, Pb, Zn, Cr, and Ni). Sandy fractions were found to be abundant in all transects except transect 3, because of the existence of the Pichavaram estuary fed by river Vellar in the north and Coleroon in the south. Among all the trace metals, Fe is the most abundant in the sediment samples. And metals such as Co, Pb, Cr and Ni are higher than the average background values, suggesting adverse effects of human activities in polluting the marine environment. The pollution indices viz. Enrichment Factor (EF), Geoaccumulation Index (Igeo), and Contamination Factor (CF) were calculated to assess trace metal pollution. The results imply that Cu, Co, Mn, Pb, Zn, Cr, and Ni in most of the sampling sites are highly contaminated in terms of Geoaccumulation Index (Igeo). Pb, Zn and Cr are heavily contaminated, while Cu, Mn, Ni, and Co showed moderate contamination, as demonstrated by the CF values. Pearson correlation and principal component analysis (PCA), explain the combination of geogenic and anthropogenic sources contributing trace metals to the marine system.

Seagrass Ecosystems of Tropical Islands As Bioindicator of Anthropogenic Trace Metal Contamination

“…Similarly, low pH (7.9-7.5) leading to increase in concentration of Pb in sediment and seagrass tissues has been observed for other seagrass species like Posidonia oceanica and Cymodocea nodosa meadows in the Mediterranean Sea Vizzini et al, 2013). Furthermore, this inverse relationship between low pH and sediment OM and trace metals (like As, Pb and Co) have been observed in the Bay of Bengal region and southeast coast of India (Jayaprakash et al, 2016;Naik et al, 2023;Sadanandan et al, 2023).…”

“…The anthropogenic source of trace metals to coastal marine ecosystems is mostly through riverine input of land derived contaminants and direct disposal of industrial or domestic waste water into the coastal ecosystems that accumulates in the sediment of seagrass ecosystems (H. Lee et al, 2023;Naik et al, 2023;Nazneen et al, 2022). This riverine input also contributes significant amount of land derived OM, silt and clay fractions into the seagrass sediment that plays an important role in trace metal adsorption onto the fine fraction of the sediment (Sahu et al, 2023;Nishitha et al, 2022;Sadanandan et al, 2023). However, in our study locations of ANI, there are no direct riverine input as ANI is an island ecosystem and lacks any well-developed riverine system, but our study locations like Burmanallah has a small mangrove creek, whereas Havelock Island and Haddo Bay has permanent waste water drains that provide a continuous input of land derived OM and industrial and domestic waste water rich in OM and silt into these coastal seagrass ecosystems (Sahu et al, 2023;VishnuRadhan et al, 2015).…”