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February 10, 2021

Australia’s gold industry stamped out mercury pollution — now it's coal's turn

Coal-fired power plants are now Australia’s largest controllable source of mercury emissions, releasing between two and four tonnes of mercury every year

Mercury is a nasty toxin that harms and . Most human exposure comes from eating fish and other seafood. But how does mercury enter the Australian environment in the first place?

dug into official data and past research to answer this question.

In some rare good news for the environment, it turns out one Australian industry 鈥� gold production 鈥� has brought mercury emissions down to almost zero. But more can be done about mercury emitted from coal-fired power stations.

Australia is one of the few developed countries yet to ratify the United Nations鈥� , which aims to reduce mercury in the environment. But once we deal with emissions from coal burning, we鈥檒l be closer than ever to addressing the problem.

 

Where does mercury pollution come from?

Mercury is a heavy metal that cycles between the atmosphere, ocean and land. It occurs naturally but can be toxic to humans and wildlife.

Most human-caused mercury emissions come from the burning of and the mining and production of and other metals.

What鈥檚 more, items such as light bulbs and thermometers dumped in landfill can 30-50 years later.

Once in the air, mercury can float around for months, crossing oceans and continents to end up back on the ground, far from where it was emitted.

It鈥檚 eventually by soils, water and plants, then slowly released back to the atmosphere.

 

A success story

Estimates vary on the exact amount of mercury that Australian activities release to the air. Studies we reviewed put the figure at anywhere between 8 and 30 tonnes each year.

Our analysis shows the figure is likely at the low end of that range 鈥� largely due to a single success story.

In 2006, a gold production facility in Kalgoorlie was thought to cause half of Australia鈥檚 industrial mercury emissions. The massive operation includes the Fimiston Open Pit, or 鈥淪uper Pit鈥�, so large it can be seen from space.

Gold ore naturally contains mercury. To extract the gold, the ore is typically roasted at temperatures of up to 600鈩�. During this process, the mercury escapes into the atmosphere. Most mercury pollution from Australia鈥檚 gold industry came from a single roaster at the Kalgoorlie site.

But over one decade, mercury emissions from the operation dropped from more than 8 tonnes to just 250 kilograms. This was largely due to a technology upgrade in 2015, when the roaster was by a grinding process.

This success means coal-fired power plants are now Australia鈥檚 largest controllable source of mercury emissions. They emit between two and four tonnes of mercury every year ().

 

Other sources of mercury emissions

Other natural and human activities release mercury into the air. They include:

Bushfires: Mercury is usually released to the environment . But the process can be much more rapid if the .

Our research found most estimates of bushfire emissions fall between 4 and 40 tonnes each year. But this work relied on measurements from overseas. from Australian ecosystems suggests past estimates are probably too high 鈥� possibly due to lower mercury concentrations in some Australian vegetation.

Soils and unburnt vegtation: Only has calculated the mercury released from Australian soils and unburnt vegetation, which it put at a whopping 74 to 222 tonnes per year.

When that research was published in 2012, there were no Australian data to test the model behind these numbers. We still don鈥檛 have many measurements, but most show Australian soils and vegetation take up about as much mercury as they release.

The one exception is 鈥渆nriched鈥� soils, which contain more mercury than other soils. This is because they are located over natural mineral belts and at former mining sites. At one location in northern New South Wales, enriched soils emitted as much mercury as nearby unenriched soils.

Mercury from elsewhere: Mercury released by other countries can in the air. The levels are tough to quantify, but we are currently using models to produce an estimate.

 

It鈥檚 time to act

Even with our new, lower estimates, Australia鈥檚 per capita mercury emissions remain , likely due to our reliance on coal burning. .

Some mercury emitted by power plants isn鈥檛 in the air for long before it . This can harm .

The federal government recently used in sugar cane farming. With gold production also taken care of, reducing mercury emissions from power plants is the logical next step.

It鈥檚 also time for Australia to formally commit to the Minamata Convention. Once we ratify the deal, we鈥檒l be bound to control under international law 鈥� and that鈥檚 good for humans and wildlife everywhere.

 

This article is republished from under a Creative Commons license. 

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