Researchers at Duke University in North Carolina (United States) have developed a test for distinguishing lead isotopes found in coal fly ash from lead isotopes found in other lead-containing sources, such as paint. Fly ash is a fine particulate by-product from the burning of coal in electric power plants. Fly ash is one component of coal ash, which is stored onsite at such facilities in piles or lagoons (ponds) before being sent to landfills for disposal or for use in construction materials, such as cement. Fly ash contains numerous toxic substances, such as arsenic, mercury, cadmium, lead, and other heavy metals, which can cause heart disease, cancer, or damage to the nervous system if inhaled or ingested. Fly ash can enter the air during transport to or at disposal sites, as well as after accidental spills of coal ash. In addition, fly ash can leach into groundwater from storage ponds. See also: Air pollution; Arsenic; Cadmium; Cement; Coal; Electric power generation; Groundwater hydrology; Hazardous waste; Lead; Mercury (element); Toxicology; Water pollution
Reporting in the journal Environmental Science & Technology Letters, the researchers found that fly-ash samples resulting from coal combustion obtained from different regions of the United States produced unique lead isotope ratios, and that these ratios differed from naturally occurring or other anthropogenic lead-containing sources. Isotopes are chemical elements that have the same atomic number but different relative atomic mass; that is, isotopes of an element have different numbers of neutrons. Lead (Pb) has 11 known isotopes, and their ratios vary depending on the source material and geologic history. The isotope ratios analyzed in this study were 206Pb/207Pb. See also: Atomic number; Chemical element; Isotope; Lead isotopes (geochemistry); Neutron; Relative atomic mass
To validate the test as a method for detecting fly ash in the environment, the researchers analyzed sediment samples from Sutton Lake in North Carolina—a known site of coal-ash spills from a nearby coal-fired power plant that has since closed—and compared them to sediment samples from an uncontaminated lake. The results showed that the Sutton Lake sediments contained a lead isotope ratio corresponding to fly ash, while sediments from the uncontaminated lake did not. This new test for detecting fly ash could be particularly important for the United States following the November 4, 2019, publication of pending rules weakening regulations for the disposal and storage of coal ash by the U.S. Environmental Protection Agency (EPA), under the direction of former coal industry lobbyist and current EPA administrator Andrew Wheeler. According to the researchers, the toxicological risks of fly-ash exposure are predicted to increase under the pending rules. See also: Environmental toxicology; Risk assessment and management
