Researchers from Duke University have developed four new tests capable of detecting toxic coal ash contamination in soil with high sensitivity. The corresponding research paper was published in Environmental Science and Technology.
The tests can detect fly ash, a part of coal combustion residuals that are produced by power plants burning pulverized coal. Often microscopic in size, these particles can contain high concentrations of toxic elements including arsenic, antimony, and selenium.
While most fly ash is captured and disposed of by power plants themselves, some escapes into the environment where it can accumulate in soil and pose risks to the environment and human health. Inhaling fly ash particles with high levels of toxic metals has been associated with lung and heart disease, cancer, nervous system disorders, and other illnesses.
"Being able to trace the contamination back to its source location is essential for protecting public health and identifying where remediation efforts should be focused," said Zhen Wang, lead author of the study. "These new methods complement tests we've already developed for tracing coal ash in the environment and expand our range of investigation."
The tests developed by the researchers are designed to be used together to detect fly ash particles The first test measures the abundance of various metals known to be more common in coal ash than in normal soil. If they are present at higher-than-normal levels, the researchers test samples with two other geochemical indicators sensitive to trace metals.
They then use a microscope to examine the soil sample to see if they can physically identify any fly ash particles. Taken together, these methods provide estimates on the proportion of soil comprised of fly ash.
To test the new approach, the researchers analyzed 41 surface soil samples downwind from coal-fired plants in Tennessee and North Carolina. From these tests, they confirmed that the four testing methods complemented each other well and could provide a reliable method for detecting soil contamination.
As most of the samples they observed found low levels of fly ash, they also highlighted the importance of regularly monitoring sites in close proximity to coal-fired power plants. They highlighted that health risks could grow with repeated exposure to certain areas as fly ash accumulates over time.
"Low concentrations of toxic metals in soil does not equal to no risk," said Avner Vengosh, one of the authors of the study. "We need to understand how the presence of fly ash in soils near coal plants could affect the health of people who live there. Even if coal plants in the United States are shutting down or replaced by natural gas, the environmental legacy of coal ash in these areas will remain for decades to come."