Robert Frost’s statement, “nothing of the gold can endure,” implies the perpetual presence of mercury.
Due to its remarkable affinity for valuable metals, mercury has been employed for millennia in the extraction of gold and silver. Numerous studies indicate that this small-scale or “artisanal” mercury extraction has become the primary source of mercury contamination in recent times.
Apart from seeping into the soil and rivers through water used in the process and runoff from rain contaminated by mining operations’ remnants, burning during mining to separate gold from rock or mud releases mercury into the air.
Many of these miners operate illegally in developing countries like Peru, where there is little to no regulation, making the practice challenging to eradicate, according to Dave Krabbenhoft, a researcher at the United States Geological Survey in Middleton, Wisconsin.
The heavy metal persists for centuries and is re-released from the soil and water into the atmosphere and vice versa. As a volatile element, mercury can evaporate at relatively low temperatures and then deposit outside the atmosphere through chemical reactions, returning to the soil or water. In fact, a significant portion of the mercury reaching the ocean (after falling from the air or being carried by rivers) is “inherited” mercury already present in the environment, much of it emitted by chimneys or extracted from gold mines centuries ago, Krabbenhoft explained years ago to WordsSideKick.com.
Scientists pay special attention to oceanic mercury because it is where the element transforms into methylmercury, the toxic carbon-containing form that accumulates in fish; Consuming seafood is the primary way humans are exposed to the heavy metal, they say. Most methylmercury is produced by microbes in low-light conditions, according to a study published earlier this year in the journal Nature Geoscience.
However, there is some promising news: delegates from countries around the world will gather in Minamata, Japan, in early October to formalize an agreement to reduce mercury pollution in various ways. Nevertheless, this news is tempered by a review published on Thursday in the journal Science, suggesting that mercury levels in the environment are likely to continue increasing for decades, said Krabbenhoft, co-author of the study.
Worse in the short term
One measure people can take to reduce their exposure to mercury, said Grandjean, is to eat fish that accumulate less mercury, such as small, short-lived fish like sardines; Methylmercury gradually moves up the food chain and is more prevalent in large, carnivorous, and old fish, he added. [Is it safe to eat sushi?]
“We have already introduced so much mercury into ecosystems that it will be decades before we can benefit from the UN treaty,” Grandjean said. “Meanwhile, we must choose our seafood wisely.”
Grandjean hopes that efforts to reduce small-scale mining will succeed. However, the construction of new coal plants, particularly in China, is not encouraging, as fossil fuels are the second-largest source of mercury pollution, said Krabbenhoft. Climate change may also worsen mercury pollution, as a warmer world is expected to cause more intense floods and wildfires, releasing mercury trapped in the soil and vegetation, he said.
The convention is a good first step, but the persistent nature of mercury means that the situation will worsen before it improves, said Grandjean, although he still holds hope that mercury pollution can be curbed.
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