Stray showers of mercury getting into food chain

Study shows over time mercury is oxidised and gets deposited back on Earth, through rain or snow. Bacteria then transform the oxidised mercury into methyl mercury, which easily enters the food chain.

The Guardian:

Poisonous metal released as a vapour by burning fuel, then falls back to Earth and gets absorbed by the aquatic ecosystem

Earth is being showered with mercury that can land anywhere and enter the food chain, a study has shown. The poisonous metal is released as a vapour by burning fuel then falls back to Earth and is easily absorbed by the aquatic ecosystem. Thousands of tonnes of mercury vapour are pumped into the air each year. Scientists discovered that in time mercury is oxidised it can then be deposited back on Earth, either in rain or snow. Bacteria transform the oxidised mercury into methyl mercury, which easily enters the food chain. US scientist Dr Seth Lyman, who led the research while at the University of Washington Bothell, said: "Much of the emitted mercury is deposited far from its original sources.

"Mercury emitted on the other side of the globe could be deposited right at our back door, depending on where and how it is transported, chemically transformed and deposited."

Mercury from coal burning in Asia, for example, could circle the globe several times before being oxidised and carried back to the Earth's surface.

Some areas, including the south-west US, had specific climate conditions that allowed them to receive more oxidised mercury from the upper atmosphere than others.

The findings are reported today in the journal Nature.

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