Assessment of heavy metal contamination and ecological risk of core sediments in a coastal wetland of India

ABSTRACT

Wetlands are one of the most important ecosystems on earth, which help sustain life, yet they are reported to be at the receiving end of the high rate of pollution. The state of Kerala on the southwest coast of India is bestowed with several wetlands including Ramsar sites. Although the larger wetlands have been extensively studied, smaller or local wetlands have often been neglected; however, the environmental problems will be first reflected in the small wetlands. In this study, the ecological risk assessment of core sediments of one such site, the Biyyam wetland, a wetland of national importance, is reported for the first time. Sediment core samples were collected from four different stations of Biyyam wetland, and concentrations of heavy metals such as Ni, Zn, Mn, Cu, Cd, and Pb were determined. Statistical analysis indicated that correlation among different metals differed with respect to stations, but the percentage of organic matter showed a positive correlation with the concentration of the metals. The mean concentrations of Ni, Pb, and Cd exceeded the global average shale value. The quality of the sediments was assessed based on numeric Sediment Quality Guidelines. The degree of Contamination, Pollution Load Index, Enrichment Factor, Geoaccumulation Index, Ecological Risk Index, Toxic Unit, and Toxic Risk Index were used to evaluate the ecotoxicity of the heavy metals in the sediment core samples. The results inferred serious anthropogenic pollution in the wetland, and Cd was reported as the prominent metal contributing to heavy metal toxicity and ecological risk in the study area, which may in long run be toxic to the aquatic ecosystem.

KEYWORDS:

• Biyyam wetland
• sediment core
• sediment quality guidelines
• degree of contamination
• ecological risk index
• toxic risk index

Acknowledgments

The research described in this paper was financially supported by the Department of Science and Technology (DST/INSPIRE Fellowship).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Department of Science and Technology (DST/INSPIRE Fellowship) [IF170960].