Mercury leaves first footprint in soil

INDIANA U. (US) — Mercury’s first step toward contaminating watersheds and the fish that swim in them can be found in the soil surrounding coal-fired power plants in industrialized cities.

Previous research on the spread of environmental mercury has focused on waterways, but a new study, published in the journal Water, Air & Soil Pollution, tested soil samples, detecting hot spots of mercury contamination in central Indiana specifically tied to local coal-fired power plants by chemical signatures.

Winds blew the mercury contaminated soil to the northeast and the natural flow of waterways brought the mercury back to the southwest, far into bucolic appearing areas frequented by anglers.

Wind patterns in this area of Indiana blow dominantly to the northeast. The high soil mercury values are seen downwind of the largest mercury emitter in central Indiana. The pattern suggests local sources of mercury also affect local deposition of mercury, which in turn causes high levels of mercury in waterways and fish. (Credit: Indiana U.)

While wind patterns vary by cities, the process in various urban areas is similar with mercury emitted from coal-fired power plants contaminating soil that is then transported downstream. Since cities have a high percentage of impervious surfaces like roads and parking lots, the mercury enters waterways rapidly.

“Mercury from coal-fired power plants has been found in the ice at the North and the South Poles, so the fact that these noxious emissions are swept far away to other areas or even continents, with global environmental impact, is well known,” says Gabriel Filippelli, professor of earth sciences at Indiana University/Purdue University Indianapolis.

“What had not been previously shown is the impact of the mercury on the environments in cities, suburbs, and rural areas near specific coal-burning power plants.”

Coal-fired power plants produce electricity at a relatively low cost, but that’s a false economy, Filippelli says, because the cost figures don’t factor in the impact of these plants on human health.

Mercury poisoning can cause permanent neurological damage in humans. Pregnant women and their fetuses are especially susceptible to mercury, much of which enters the body through consumption of contaminated fish.

“We are fouling our local as well as global environment and little has been done to stop it. It all comes down to the choices we make to produce energy,” Filippelli says.

“As we gain a better understanding of the deposition and risk patterns of mercury from using dirty coal as our primary energy source in the Midwest, we hopefully will be better able to stop or decrease the emission of this neurotoxin and halt the damage it is causing humans.”

Carrie Lynn Hatcher, a former graduate student working with Filippelli, and now at the University of Toronto, is co-author of the study.

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