Mercury study on major saltwater lake

·2-min read

Scientists are working to assess the impact of high mercury levels found in Australia's largest coastal saltwater lake, due to the presence of coal-fired power plants.

Researchers from Monash and Australian National universities say their work confirms power plant emissions have contributed to contamination in sediments in Lake Macquarie.

Their studies have involved reconstructing the deposition of mercury in the bed of the lake, south of Newcastle, over the past 100 years.

From there, they examined geological records and applied modelling around the impact of fluid motion and atmospheric forces.

The next step will involve determining mitigation strategies and providing evidence for retrofitting power plants with emission-control tools such as bag filters and wet scrubbers.

While coal-fired electricity powers 60 per cent of Australian homes, there is little understanding of how it contributes to mercury accumulation in aquatic sediments, despite estuaries across the country facing increasing risk of metal contamination.

With major coal deposits mostly on the coast and close to population centres, power plants and their ash dams are often found near estuaries because they act as a water source for cooling processes.

The Lake Macquarie area accommodates Eraring power station, which is Australia's largest and supplies 25 per cent of NSW's electricity.

The lake itself is twice the size of Sydney Harbour and home to significant numbers of endangered bird species.

Lead researchers Anna Lintern and Larissa Schneider say the key challenge in managing waterway contamination is identifying the source of contaminants.

"It is important to identify whether Hg (mercury) in aquatic systems is coming from atmospheric emissions or from the ash dams associated with coal-fired power plants," Dr Lintern said.

"Targeted Hg management strategies can (then) be designed and money isn't being wasted on strategies that don't address the biggest source of Hg."

It's hoped the findings can be used to better understand the impact of coal combustion on mercury accumulation Australia-wide, thereby filling the knowledge gap identified internationally.

"Australia is currently at odds with many of its traditional international partners, such as Japan, the US, Canada, the UK, which have extensive information on Hg emissions and accumulation trends in aquatic sediments dating back to approximately the 1850s," Dr Schneider said.

"The data indicate that in these countries, current Hg accumulation is 3.6 times greater than what it was prior to industrialisation."

More comprehensive studies are required in Australia on how Hg accumulation and deposition have changed water bodies from prior to the construction of power plants to the modern era, she said.

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