Latrobe and Hunter areas both have coal stations, but one has much worse mercury pollution
We know that coal-fired power plants can generate high levels of carbon dioxide, but did you know that they can also be a major source of mercury emissions?
Our new research compared the level of mercury pollution in the Hunter Valley in NSW and the Latrobe Valley in Victoria.
And we found that Latrobe Valley power plants emit about 10 times more mercury than Hunter Valley power plants. Indeed, the level of mercury in the environment of Latrobe Valley is 14 times higher than what is typically natural for the region.
So why is there such a difference between states? Well, it has a lot to do with regulation.
Following a requirement by NSW for power plants to install pollution control technology, levels of mercury in the environment have plummeted. In Victoria, by contrast, coal-fired power plants continue to operate without some of the air pollution controls imposed by New South Wales and other developed countries.
To minimize the safety risks associated with excessive mercury pollution, coal-fired power plants in all Australian jurisdictions should adopt the best available technologies to reduce mercury emissions.
A dangerous neurotoxin
Mercury is a neurotoxin, which means it can damage the nervous system, brain, and other organs when a person or animal is exposed to dangerous levels.
Coal naturally contains mercury. So when power plants burn coal, mercury is released into the atmosphere and then deposited on the Earth’s surface. When a high level of mercury is found in bodies of water, such as lakes and rivers, it can be transferred to fish and other aquatic organisms, thus exposing people and large animals to the mercury which is collected. feeds on these fish.
Mercury does not easily degrade or leave aquatic environments such as lakes and rivers. It is a persistent toxic element – once in the water, it stays there.
The amount of mercury emitted depends on the type of coal burned (black or brown) and the type of pollution control devices used by the plants.
Stations in Latrobe Valley in Victoria burn lignite, which contains more mercury than the black coal typically found in New South Wales. Despite this, Victorian regulations historically did not impose specific limits on mercury emissions.
In contrast, power plants in NSW are required to use “bag filters,” a technology used to trap mercury particles (and others) before they enter the atmosphere.
Although bag filters alone do not meet global best practices, they can still be effective. In fact, after baghouse filters were upgraded at the Liddell Power Plant in Hunter Valley in the early 1990s, deposition of mercury to the environment was halved.
The best available technology for controlling mercury emissions from coal-fired power plants is a combination of “wet flue gas desulfurization” (which removes mercury in its gaseous form) and bag filters (which removes particulate-bound mercury. ).
This is what has been adopted in North America and parts of Europe. It not only filters mercury, but also removes sulfur dioxide, nitrogen oxides and other toxic compounds from the air.
Using lake sediments to see into the past
Lake sediments can trap mercury deposited in the atmosphere and in surrounding areas. Sediments that contain this mercury build up on the bottom of lakes over time – the deeper the sediment, the further back in time we can.
We took sediment samples from the lakes in the Latrobe and Hunter valleys and dated them to 1940 to obtain a historical record of mercury deposition.
This information can help us understand the amount of mercury naturally present before the construction of coal-fired power plants, and therefore show us the impact of burning coal.
From these records, we found that the adoption of bag filters in the Hunter Valley correlated with the decline in mercury deposition in NSW from the 1990s.
In contrast, in Victoria, where such a requirement does not exist, emissions and deposition of mercury have continued to increase since the completion of the Hazelwood power plant in 1971.
What do we do about it?
In March, the state government of Victoria announced changes to regulatory license conditions for lignite-fired power plants. Although mercury emission quotas were included for the first time, they are arguably still too high and there is no need to install specific pollution control technologies.
There is a risk that this approach will not reduce mercury emissions from existing levels. Instead, Victoria should consider more ambitious regulations that encourage adoption of best technological practices to help protect local communities and the environment.
Another essential step towards protecting human health and the environment from mercury is for the federal government to ratify the Minamata Convention on Mercury, an international treaty designed to protect human health and the environment from mercury.
Despite signing the convention in 2013, the Australian government has yet to ratify it, which is necessary to make it legally binding in Australia.
Ratification of the convention will require state and federal governments to develop and implement a strategy to reduce mercury emissions, including from coal-fired power plants across Australia. And this strategy should include the deployment of efficient technologies. Our research shows that it can make a big difference.
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