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World Oceans Day 2018: Regulating Lead and Mercury Releases has Decreased Marine Pollution, IAEA Research Shows


Scientists at the IAEA Environment Laboratories in Monaco analyse sediment, biota and water samples to determine the levels of contaminants. (Photo: T. Misra/IAEA)

The levels of lead and mercury in the sea reduce noticeably following concrete actions to limit their release, recent research at the IAEA using nuclear techniques has shown. The banning of leaded petrol and the closure of a mercury discharging plant have led to decreases in pollution levels over 10-15 years.

Human activities including industry and agriculture can have a significant impact on the marine environment due to the release of pollutants into the sea. The new research has demonstrated that after government regulation put an end to certain environmentally unfriendly practices, pollution trends in the sea can be reversed.

This is the case for lead, which when consumed by fish which is in turn eaten by people, can cause damage to the human nervous system and internal organs. Many different activities such as mining or smelting in metallurgy and the burning of coal as well as lead’s use in batteries, paint, ceramics and other everyday items can release it into the environment. The biggest source of lead pollution in the last century was related to the use of leaded petrol.

As part of efforts to develop new methods to determine the source and levels of lead pollution, researchers at the IAEA Environment Laboratories analysed sediments from the Baltic Sea and the Caribbean Sea. In mapping the pollution history in a sediment core from the Baltic coast of Germany, researchers could clearly observe that within 10 to 15 years of phasing out lead in petrol by 1996, lead pollution levels in the sea had decreased. IAEA scientists acknowledge that the levels of all pollutants may not decrease so quickly, but the results of taking concrete actions such as mandating the use of unleaded petrol are apparent.

In addition, IAEA researchers have successfully developed methods to use lead isotope ratios to determine the source of lead pollution and assess whether it is naturally present or the result of anthropogenic activities, since natural and anthropogenic lead sources will show different isotopic fingerprints and isotope compositions, said Emiliya Vasileva-Veleva, a research scientist at the IAEA’s Marine Environmental Studies Laboratory. “This information can then be used by governments to inform policy decisions to limit or stop its emission,” she said.

Mercury levels

IAEA scientists' analysis of a dated sediment core in a Caribbean bay shows total mercury (Hg) levels rapidly decreased after the closure of a discharging plant. The numbers 1964 - 2010 represent years of sediment formation and are a proxy for the contaminant’s concentration in the water at that time.

As part of the analysis of sediment cores from around the world, IAEA researchers also analysed mercury and methylmercury levels in sediment from Cartagena Bay in Colombia.

Mercury was used in an alkali plant there as a catalyser, and in the 1970s, high concentrations were found in water, sediments and marine organisms as a result of discharges from the plant.

Years later, after the plant had been closed, IAEA researchers showed, by analysing sediment core taken from the bay, that levels of total mercury had started to decrease.

While remnants of this pollution are still buried in the sediment, acute toxicity has been greatly reduced.  

IAEA support to Member States

To support and build capacity for countries to monitor and assess contaminants in the ocean, the IAEA Environment Laboratories organise training sessions, including as part of the United Nations Environment Regional Seas Mediterranean Action Plan. These courses combine both theoretical and practical, hands-on training and include sessions on sampling and analytical techniques to improve the accuracy of detecting contaminants like mercury and lead as well as organic contaminants like petroleum hydrocarbons from oil spills, and persistent organic pollutants like PCBs, a component in materials like plastics.

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