Heavy metal contamination along different tidal zones of a tropical Bay of Bengal coastal environment influenced by various anthropogenic activities

The spatiotemporal variations of five heavy metals (Cd, Cu, Cr, Pb, and Zn) in the beach sediments along the Tamil Nadu coast sourced from various anthropogenic activities were assessed using atomic absorption spectrophotometry (AAS). Various pollution monitoring indices were computed to clearly understand the metal pollution status along the Tamil Nadu coastline. The metal concentrations in sediments were typically higher in the summer season than in the monsoon season. In the monsoon season, metal concentration followed a decreasing order of Zn > Cr > Cu > Pb > Cd, and in the summer season, the order was Cr > Zn > Cu > Pb > Cd. During the monsoon season, freshwater runoff from the rainfall dilutes the sediments and their trace element load. However, due to a lack of freshwater influx during the summer season, the heavy metals in the sediments get concentrated and showed elevated levels. Geo-accumulation index, ecological risk index, pollution load index, and contamination degree clearly depict that Cd and Pb have higher accumulation and pose greater hazard when compared with other metals. The rivers flowing in the region also transport the heavy metals from the mainland to the estuaries and coastal environments. Metal levels along the Tamil Nadu coast are influenced by various anthropogenic activities persistent along the coastline. Some of the activities that cause metal contamination are mining, milling, electroplating, furnishing, pharmaceutical industries, fishing, harbor activities, urban runoff, and agricultural runoff, which release a variety of toxic metals into the coastal environment.

Avian feathers as a biomonitoring tool to assess heavy metal pollution in a wildlife and bird sanctuary from a tropical coastal ecosystem

In this study, we have assessed the concentrations of four heavy metals (Cu, Zn, Cd, and Pb) in the feathers of 11 species of birds from the Point Calimere Wildlife and Bird Sanctuary, a protected environment. Concentrations of copper and zinc were detected in all the bird species, cadmium was observed only in two bird species, and lead was below the detection limits for all birds. The order of concentration of metals in the feathers is Zn > Cu > Cd > Pb. Using the multivariate statistical analysis, principal component analysis (PCA), the metal origins were traced to natural, dietary, and manmade sources. In addition, sediment samples were also collected from the sanctuary, to assess the bioaccumulation factor (BAF). The BAF values follow the order Cd < Cu < Zn < Pb. In comparison with worldwide heavy metal reports in bird feathers, lower concentrations of metals are observed in our study area. The tropical marine ecosystem at Point Calimere Wildlife and Bird Sanctuary can be considered as pristine regarding heavy metal pollution. Continuous monitoring of the ecosystem is crucial to sustain the pristine nature of the sanctuary and to attract many more birds.

Health risk assessment and bioaccumulation of metals in brown and red seaweeds collected from a tropical marine biosphere reserve

In the present study, we have assessed the degree of contamination of heavy metals (Cd, Cu, Pb, and Zn) in ten species of red and brown seaweeds, the seasonal variations in the concentration of metals, and the health risk due to the seaweeds. Overall metal concentrations for red and brown seaweeds followed the order Pb > Zn > Cu > Cd and Pb > Cu > Zn > Cd, respectively. Cd and Pb levels were found to be elevated in both the red and brown seaweeds. Multivariate statistical analysis revealed that the sources of Cd and Pb are mainly anthropogenic. Despite the high concentrations of the non-essential metals (Cd and Pb) in the seaweeds, the health risk assessment revealed that they have a lower hazard index. Hence, consumption of edible red and brown seaweeds from the Tuticorin coast may not pose health hazards in humans for the time being.