Hunt on for main culprit as scientists find coal contamination in Lake Macquarie

A new study has confirmed that coal plants in the New South Wales Hunter Region have contributed to mercury contamination in sediments in Lake Macquarie, and is seeking to narrow down which has been the biggest contributor to this pollution: the coal plants’ ash dams or their atmospheric emissions.

The study led by researchers from Monash University and Australian National University, is assessing the impact of high levels of mercury in the sediments of Lake Macquarie, which hosts on its shores two coal-fired power plants: Delta Electricity’s Vales Point and Origin Energy’s Eraring.

Australia’s largest coastal salt water lake, known as Awaba to the Aboriginal people of the lands of the Awabakal nation, Lake Macquarie is at grave risk of increasing levels of mercury contamination, from both the particulate matter emitted by the coal plants and from their ash dams, which also sit on the Lake’s shores.

As the research notes, coal power generators are often located near estuaries in Australia because they provide a water source for industrial processes in the plants’ operations, including for cooling.

Despite this being a common practice in coal plants around Australia, the researchers from Monash and ANU say there is still little understanding of how coal-fired power plants have contributed to mercury accumulation in aquatic sediments.

This lack of understanding is also exacerbated by a lack of accountability from coal plant operators and a general failure to hold them to account on the part of governments and regulators.

In 2020, Vales Point was called out for an almost three-fold increase in particulate pollution and pinged for 14 water pollution breaches over the course of the 2019/2020 financial year.

In response to the latter offence, the Trevor St Baker-owned Delta sought to blame the poor water quality on dust storms, bushfires and significant rainfall and flooding events in the Lake Macquarie catchment, and said that Vales Point was “actually reducing” pollutants in the water.

In another instance in 2020, when the NSW Environment Protection Authority alleged that the Vales Point ash dams were being used as a dump for toxic waste unrelated to the coal plant, Delta was issued a paltry $30,000 fine for the breach.

Less than a week earlier, Delta secured $8.7 million in taxpayer funds for upgrades to the ageing coal plant from the Morrison government in the federal budget.

And while lawyers at groups like Environmental Justice Australia have sought to bring such breaches to the attention of the public, and hold coal plant owners to account, the research team from Monash and ANU are hoping to use science to pin down the exact sources of dangerous long-term water contamination.

They believe it is critical to understand the Hg emissions from coal-fired power plants and the resulting fate of mercury, or Hg, ending up in nearby estuaries, so that appropriate management strategies can be implemented.

“A key challenge in managing contamination of waterways is identifying the source of contaminants,” said Anna Lintern from the Department of Civil Engineering at Monash University, one of the lead researchers for the study.

“In the context of Hg, it is important to identify whether Hg in aquatic systems is coming from atmospheric emissions, or from the ash dams associated with coal-fired power plants, so that targeted Hg management strategies can be designed and money isn’t being wasted on strategies that don’t address the biggest source of Hg.”

The research hopes to improve of the methods of previous studies that used Hg isotopes to identify sources of mercury and determine whether the key source of deposits in aquatic sediments was from a coal-fired power plant or from soil erosion – a method that is not always accurate.

To do this, the team incorporated a new approach that can be used to support isotopic evidence, in the hope of not only determining if the mercury deposits in Lake Macquarie were coming from coal plants, but also where they were coming from within those coal plants.

“As part of this study we reconstructed the historical deposition of Hg in sediments of the lake for the last 100 years to identify the impact of coal-fired power plants and atmospheric emission management strategies on Hg levels in aquatic sediments,” said Dr Lintern.

“We then used statistical, hydrodynamic, particle density and atmospheric modelling to identify whether Hg in the aquatic sediments were coming from ash dams or from atmospheric emissions from coal-fired power plants.”

The team hopes the findings from Lake Macquarie can be used to better understand the impact of coal combustion on mercury accumulation in Australia, and fill a knowledge gap identified by the United Nations Environment Program.

“Australia is currently at odds with many of its traditional international partners, such as Japan, the United States, Canada, United Kingdom, which have extensive information on Hg emissions and accumulation trends in aquatic sediments dating back to approximately the 1850s,” said Larissa Schneider, another of the lead researchers from ANU.

“The data indicate that in these countries, current Hg accumulation is 3.6 times greater than what it was prior to industrialisation. In Australia, more comprehensive studies are required on how Hg accumulation and deposition have changed water bodies from prior to the construction of power plants to the modern era,” she said.