Study: Large thunderstorms spread mercury pollution

TALLAHASSEE, Fla., Aug. 31 (UPI) -- Mercury pollution gets around. Though much of it is released into the atmosphere, a significant portion is returned to ground by rain. New research suggests it's thunderstorms that play the biggest role in moving mercury.

In an effort organized by Christopher Holmes, a meteorology professor at Florida State University, scientists collected rainwater in Florida, Georgia, Vermont and Wisconsin. The samples were tested for mercury levels and matched with weather data to determine whether the rain had been delivered by a thunderstorm or rainstorm. Radar offered further details on the nature of each storm.

"The highest concentrations occurred during thunderstorms and the lowest during a regular rainstorm," Holmes said in a news release.

The higher the storm clouds reached, the more mercury the storm delivered to the ground. Thunderstorm clouds often reach twice as high as rainstorm clouds.

"The mercury is being transported into our region by winds, and tall thunderstorms are bringing it down to Earth," Holmes added.

For the last two decades, states bordering the Gulf of Mexico have topped the charts for mercury concentrations on the East Coast. The frequency of large thunderstorms during the region's hot and humid summer months may explain why.

Because exposure to high levels of mercury can be dangerous to human health, researchers say they must continue working to understand the chemical's movements.

"We're trying to understand how mercury enters ecosystems in the U.S. and how it can affect people and wildlife," Holmes said.

The results of the latest study were published this week in the journal Environmental Science & Technology.