Team of scientists finds zinc, lead and mercury in river A group of scientists has found that the level of heavy metals such as zinc, lead and mercury is on the rise in river Hooghly due to the impact of climate change. The rise in presence of heavy metals in the river water, the scientists say, lead to accumulation of such metals in the endemic fishes and could enter the human body through food chain. The researchers were surprised after they noticed a rise in heavy metals in the surface water of lower Ganges despite less industrial activities in the coastal zone. "Our present research confirms the role of acidification in regulating the level of heavy metals in the Hooghly estuarine system," said Professor Abhijit Mitra, former head of the marine science department of Calcutta University. “The human-induced increase of carbon-dioxide which causes climate change has in turn caused a substantial decrease of pH in coastal waters," he said. The study has been done on the basis of 30 years of real-time data i.e. between 1984 and 2013. “We have observed a decrease of .002 unit per year of pH level in the 30 years. If the pH of water goes down at this rate, the effect would be disastrous,” said Mr Mitra. He said another study by a fellow researcher found that shell of snails are becoming thinner in the lower Gangetic area because of the acidification. “As the body of snails and molasses are formed of calcium carbonate, they start to dissolve with increase in level of acid in water,” he added. Dr Prosenjit Pramanick, a scientist with the department of oceanography at Techno India University, attributed the higher levels of heavy metals to the release of such metals from river sediments where they had remained locked for hundreds of years. He said: “The rise of carbon-dioxide level means more complex reactions in nature. It is because of complex reactions the acid level in water shoot up which actually releases the heavy metals confined in the sediments.” Sufia Zaman, another researcher observed that carbon-dioxide in the air is dissolving in the water to form carbonic acid, which is increasing the acid level in the river and sea water, said Mr Mitra. Mr Mitra said there is another reason behind the increase of heavy metals in the surface water. “The trollies and boats which are made of metal use anti-fouling paints. Due to salinity and increased level of acidity, the paints get dissolved into water very fast. This is another factor behind the increase of heavy metals in the river water.” Mr Mitra and his team examined fishes and prawns from lower Ganges and found the presence of heavy metals. “We have found heavy metals in fish tissue and prawn tissue. No doubt they entered the human body. But we are yet to confirm the presence of such metals in human body,” said Professor Mitra.