Scientists may have solved the mystery of why there is so much of the toxic mercury present in some parts of the world, even when the region is upwind from a known source.
A team of researchers demonstrated the key to explaining mercury's strange behavior could be the reactivity of naturally occurring halogen compounds from the ocean," the University of Colorado at Boulder reported. Airborne mercury is emitted by power plants and other sources.
"Atmospheric chemistry involving bromine and iodine is turning out to be much more vigorous than we expected," said CU-Boulder atmospheric chemist Rainer Volkamer, the corresponding author of the new paper published in the Proceedings of the National Academy of Sciences. "These halogen reactions can turn mercury into a form that can rain out of the air onto the ground or into oceans [up to 3.5 times faster than previously estimated]."
The researchers made their findings using the differential optical absorption spectroscopy instruments (DOAS), which the research group built to measure small amounts of atmospheric chemicals such bromine oxide and iodine oxide radicals. These radicals are extremely short-lived, and are hard to detect through air samples alone. DOAS measures the scattering and absorption of sunlight by gases and particles to identify a chemical's unique "fingerprint."
The findings demonstrated how mercury can sweep around the globe until it is pulled back down into the atmosphere and Earthly ecosystems through thunderstorms. This process can contaminate water sources with the toxin, leading to fish that live there to become a cause for public concern. The findings show the oxidation of mercury in the atmosphere by bromine(the first step in the reabsorption process) occurs 3.5 times faster than was previously estimates as a result of halogen in the oceans.
These findings could solve the mystery of how mercury maintains its concentration in rainwater throughout a thunderstorm, even when other chemicals are lost.
"To some extent, because of these halogens, we have a larger pool of oxidized mercury up there," Volkamer said.
