The levels, 137 micrograms per square meter of soil each year, were higher than in any forest tested near coal-fired power plants in Europe and North America, the authors reported in the British journal Nature Communication.
They behaved on a par with industrial cities in China such as coal-dependent Chongqing, they described, adding that the findings suggest a sponge-like behavior of rainforest trees.
The leaves, which are coated with contaminated dust, also absorb gaseous mercury as they take in air, they noted in the article.
The metal eventually finds its way to the ground as leaves fall or rain washes away dust and after capturing the dripping water, they discovered more than twice as much rain washout compared to any other site.
The results indicated that forests can buffer some of the harmful effects of mercury by hiding it in leaves and soil, the study participants noted.
People and wildlife are generally not at risk from this locked-up mercury, explained Luis Fernandez, a tropical ecologist and executive director of Wake Forest University’s Amazon Science Innovation Center.
You could walk, swim in the water, bury yourself in the leaves and you’re not going to get toxicity doing that, reason to keep tropical forests standing, the expert emphasized.
Still, the airborne form of mercury can become very dangerous when it seeps into water and sediment and is converted to something else, methylmercury, by bacteria in the liquid, he warned.
The team involved found sobering signs that methylmercury is reaching forest creatures, and by testing three species of songbirds they had levels two to 12 times higher than similar species caught in a forest far from a mine.
This shows that it is entering the food web, said Emily Bernhardt, a subject supervisor for biogeochemistry and analysis at Duke University in North Carolina.
Research data shows that gold mining recently overtook coal burning as the world’s largest source of airborne mercury pollution, annually releasing up to 1,000 tons of the potent brain poison into the atmosphere.
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