Tiny toxic coal ash particles in soil can be detected by new test, Energy News, ET EnergyWorld

North Carolina [US]July 23 (ANI): A suite of four new tests that can be used to detect coal ash contamination in soil with unprecedented sensitivity has recently been developed by scientists at Duke University.

The peer-reviewed study was published in the journal “Environmental Science and Technology.” The tests are specifically designed to analyze soil for the presence of fly ash particles so small that other tests might miss them.

Fly ash is part of the coal combustion residue (CCR) generated when a power plant burns pulverized coal. The tiny particles of fly ash, which are often microscopic in size, contain high concentrations of arsenic, selenium and other toxic elements, many of which have been enriched by the combustion process.

While the majority of fly ash is captured by traps in the power plant and disposed of in reservoirs and coal ash dumps, some escapes and is emitted into the environment. Over time, these particles can accumulate in the soil downwind of the plant, posing potential risks to the environment and human health.

“Because of the size of these particles, it was difficult to detect them and measure the amount of accumulated fly ash,” said Avner Vengosh, professor emeritus of environmental quality at Duke’s Nicholas School of the Environment. “Our new methods allow us to do this – with a high level of certainty.”

Coal combustion residue is the largest industrial solid waste produced in the United States. When soil contaminated with fly ash is disturbed or dug up, dust containing the ash can be airborne into nearby homes and other indoor environments. Inhalation of dust containing fly ash particles containing high levels of toxic metals has been linked to lung and heart disease, cancer, nervous system disorders and other adverse effects.

“Being able to trace contamination back to its original location is critical to protecting public health and identifying where remediation efforts need to be focused,” said Zhen Wang, a doctoral student in Vengosh’s lab at Duke, who has led the study. “These new methods complement the tests we have already developed to trace coal ash in the environment and expand our field of investigation.”

The new tests are designed to be used together to provide independent corroboration of whether fly ash particles are present in a soil sample and, if so, in what proportion of the total soil.

“First, we measure the abundance of certain metals, such as arsenic, selenium and antimony, which we know are more enriched in coal ash than in normal soil,” said Wang.

Wang added: “If these metals are present at higher than normal levels, we test the sample using two other geochemical indicators, radium nuclides and lead stable isotopes, which are more sensitive than trace metals and can be used to detect a low occurrence of fly ash in soils.We also examine the soil under a microscope to test if we can physically identify fly ash particles and estimate the proportion of the soil they constitute.

Each method has its own strengths and weaknesses, and if used alone could lead to overestimating or underestimating the presence of flies in the soil, Vengosh said. “By using all four together, we are able to verify the forensic investigation of the presence of fly ash in soils.”

To assess the reliability of the new tests, researchers analyzed surface soil from 21 sites downwind of the Tennessee Valley Authority’s Bull Run Fossil Plant in Claxton, Tennessee, and 20 sites downwind of the Duke Energy’s Marshall Steam Station on Lake Norman, North Carolina. The Carolina samples came from Mooresville, a town across the lake from the Marshall plant. Control samples were also taken from sites upstream of each plant.

Testing consistently showed that most samples taken downwind of both mills contained fly ash contamination, but since the proportion of fly ash was low, the concentrations of toxic elements did not exceed human health guidelines for the presence of metals in the soil.

The tests also showed that soil samples near Bull Run Fossil Plant in Tennessee generally contained significantly higher levels of fly ash than those in North Carolina and that the highest concentration was in the soil at Claxton Community Park. , a playground and recreation site located outside the Bull Run Factory.

What does all this say?

“First, it confirms that our new tools work consistently and, when used together, provide a reliable method of detecting contamination that other tests might miss,” Vengosh said.

“Second, it underscores the need for regular monitoring of nearby sites downwind of a coal-fired power plant, even if contamination levels are below current safety thresholds. Fly ash accumulates over time and risks may increase with repeated exposures to playground dust or household dust,” Vengosh added.

“Low concentrations of toxic metals in soil do not mean no risk,” Vengosh noted.

“We need to understand how the presence of fly ash in soils near coal-fired power plants could affect the health of the people who live there. Even if coal-fired power plants in the United States close or are replaced with natural gas, the environmental legacy of coal ash in these areas will remain for decades,” Vengosh concluded. (ANI)

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