Heavy metals- new toxic danger to urban beaches                                                                 


A study on the health of urbanized tourist beaches along the southeastern coastline of India has revealed that many of these popular beaches are now facing the threat of different environmental pollutions of which heavy metal pollution from both natural and anthropogenic sources is emerging as one of the potential threats.

A team of researchers led by the National Center for Polar and Ocean Research (NCPOR) conducted a study around three popular urban beaches in TamilNadu, namely the Marina Beach, Edward Elliott Beach and, Silver Beach, where they analyzed sediment samples for concentrations of heavy metals like iron (Fe), zinc (Zn), copper (Cu), manganese (Mn), nickel (Ni) and, lead (Pb). Though the concentration level of these heavy metals was found to be under the safe limit defined by the Bureau of Indian Standards, the researchers expressed their concern that long term exposure to these heavy metals would have an adverse effect on the marine biota. The research team suggested governmental intervention to strengthen and enforce stricter environmental laws to stop illegal anthropological activities to stop heavy metal intrusion into these beaches through a different type of wastewater seepage.

The term "heavy metals" usually refers to naturally occurring elements with a density greater than 5.0 g cm-3. Toxic heavy metals such as nickel (Ni), cadmium (Cd), mercury (Hg), lead (Pb), copper (Cu), manganese (Mn), arsenic (As), chromium (Cr), iron (Fe), and zinc (Zn) have the potential to cause serious marine ecosystem problems due to their persistent nature in the environment, toxicity and ability to enter the food chain. Even the presence of excessive amounts of essential metals/elements beyond their acceptable limit can have a toxic effect interfering with the aquatic ecosystems.

Though the concentration level of these heavy metals was found to be under the safe limit defined by the Bureau of Indian Standards, the researchers expressed their concern that long term exposure to these heavy metals would have an adverse effect on the marine biota.

When the heavy metals in water enter aquatic organisms, they are not easily decomposed and not eliminated from the bodies of the aquatic animals. They accumulate in the different organs of the aquatic animals like the liver, spleen, kidney, and viscera, etc. Heavy metal pollution of aquatic environment can be detrimental to human health also as people consuming contaminated seafoods would be suffering from the same ill effects of toxic heavy metals. This can lead to the damage of the multiple organs causing diseases or even death.

Sediments in an aquatic environment provide foodstuff to the living organisms. The aquatic sediments with toxic heavy metal persistence result in absorbing these heavy metals by the sediments, to levels many fold higher than their concentration in the aquatic environment, and thus the sediments become a secondary source of marine water pollution. When the benthic organisms come in contact with them, these toxic elements intrude on the entire benthic food chain. Therefore, eco-health of the aquatic sediments has always been considered as one of the precursors to understand pollution in aquatic ecosystem.

In the study conducted by Indian scientists at the southeastern coastline of India covering three prominent urban beaches, it was found that Ni, Co, Zn, Mn, Cu, and Cd posed a lower ecological risk than Pb (Lead) at all the three locations. Pb was found to be present in the sediments with a moderate level of ecological risk.

Besides, scientists found that the trace amounts of metals are not sufficiently toxic to harm someone walking along the seashore, but the "accumulative stress" on the marine ecosystem cannot be ignored just because they are not in higher quantity. Their persistent presence may be an indication of industrial effluents, domestic sewage, and agricultural run-offs going into these beaches. For example, the results of the present study confirmed that arsenic (As), cadmium (Cd), copper (Cu), mercury (Hg) and zinc (Zn) are the five metals that entered the marine environment of these beaches from agricultural activity. However, other heavy metals such as nickel (Ni), chromium (Cr), and lead (Pb) found in the sediments of these beaches are primarily from industrial wastes through river mouths. Iron (Fe), manganese (Mn), and cobalt (Co) found in the beach sediments are however believed to be from natural weathering processes with mild anthropogenic influence. The use of leaded petrol and chromic anti-biofilling paints in beach environments is believed to be mildly influencing the increase in lead (Pb). The research authors emphasized the necessity of regular pollutant monitoring in the marine environment.

Led by Magesh N.S of National Centre for Polar and Ocean Research, Ministry of Earth Science and Krishnakumar S., the research team comprised of Kasilingam K., Pradhap D., Saravanan P., and Rajkumar A. of Department of Geology, University of Madras, Vidyasakar A. of Department of Geology, Periyar University, Anbalagan S., & Neelavannan K. of Institute for Ocean Management, Anna University, Prince S. Godson of Department of Environmental Sciences, University of Kerala, P. Parthasarathy P. of Department of Geology, A.V.S College of Arts and Science, Salem, and Hariharan S. of Department of Geology, Central University of Karnataka.

India Science Wire


Latest Tweets @Indiasciencewire