Levels of toxic mercury in the Great Salt Lake rise again

Levels of toxic mercury in the Great Salt Lake rise again

(File Photo)


Save Story
Leer en español

Estimated read time: 3-4 minutes

This archived news story is available only for your personal, non-commercial use. Information in the story may be outdated or superseded by additional information. Reading or replaying the story in its archived form does not constitute a republication of the story.

SALT LAKE CITY — High levels of toxic mercury in the Great Salt Lake are on the rise again after nearly disappearing in years prior.

In 2010, scientists detected high levels of the toxic element, known as methylmercury, in the deep waters of the Great Salt Lake, according to University of Utah geology and geophysics professor William Johnson. The waterfowl in the area also showed exceptionally high levels of the toxin, causing authorities to issue a rare advisory that warned residents to limit their consumption of ducks harvested near the lake.

By 2015, however, 90 percent of the mercury was gone. Now, it’s back on an upward trajectory.

Scientists studying the lake have spent years testing and researching to discover the impetus behind the mercury and now believe they’ve found the answer, Johnson said.

A Union Pacific railway line divides the lake, separating the body of water into a smaller north arm and larger south arm. There isn't a river that flows into the north arm, so the water there becomes much saltier than the south arm. Two culverts allowed water to flow under the railway line from north to south and, because the northern water is so briny, it sinks to the bottom of the southern lake.

The density between the waters was so different, in fact, that the waters almost never mixed, and a deep, briny layer formed, Johnson said. Because the water at the bottom was so salty, decaying organic matter in the deep water quickly sucked out all the oxygen, forcing microorganisms to find that critical element another way.

Most of the bacteria resorted to replacing their need for oxygen with sulfate, which creates sulfide, causing the Great Salt Lake to stink like a rotten egg. The microorganisms also turn mercury in the water to its more toxic form: methylmercury.

“Methylmercury is something very toxic, and the amount in the bottom of the lake when it forms is really high,” Johnson said. “It’s the highest that was ever measured … it was discovered that in most systems with methylmercury, (the element) makes up 1 percent of the amount of mercury in a system. At the bottom of the Great Salt Lake, it’s 50 percent. It’s crazy high.”

It wasn’t until the Union Pacific railway closed the culverts for a time, however, that scientists could confirm the definite cause of the mercury levels in the lake. Once the railroad line closed and water was no longer flowing from north to south, the mercury levels began to drop quickly.

Related:

Now, the line has reopened and there's an even larger breach than before, which officials hope will reestablish water and salinity levels. Though mercury levels have begun to rise again, according to Johnson.

“(It) reopened in December, and (the briny layer) is now just starting to re-form,” Johnson said. “Last month when we sampled … we just saw the first evidence or development of the deep brine layer in the northern basin. … Now we expect in our subsequent sampling (that) it’ll start to spread southward and thicken.”

The real mystery, however, lies with the ducks. Even after mercury levels fell in 2015, the waterfowl continued to show high levels of the toxin and still do. According to Johnson, most researchers assumed the reason for mercury in the ducks was the mercury in the water, but now they’re not so sure.

Residents shouldn't worry about going in the lake, Johnson notes, but his team of researchers hope to continue the study, though funding is running low. The methylmercury in the Great Salt Lake could potentially spread to the ecosystem and eventually to humans.

“I hope people look at this … and understand more attention is needed to really understand the dynamics,” Johnson said. “... There’s potential economic impact … it’s an integrated system that we need to understand better.”

Related stories

Most recent Utah stories

Related topics

Utah
Liesl Nielsen

    STAY IN THE KNOW

    Get informative articles and interesting stories delivered to your inbox weekly. Subscribe to the KSL.com Trending 5.
    By subscribing, you acknowledge and agree to KSL.com's Terms of Use and Privacy Policy.

    KSL Weather Forecast