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Research: Isotope ratios are used as fingerprints on the impact of ash on organisms –

A Duke University study shows that trace elements in fish ear bones can be used to identify and track contamination of coal ash in the waters of its residence.

"Calcified structures – or otoliths – found in the ears in fish are known to store a lot of life history information, including chemical and physical records of fish age, christmas habitat and migration patterns," said Jessica Brandt, lead author of this paper. and a 2018 PhD graduate from the Duke of Nicholas School of the Environment. "We have shown that otolith also captures contaminant signatures that have affected fish ecosystems."

Brant and his team found that the ratio of strontium isotopes in fish otolites from two North Carolina lakes – both of which received waste from coal ash pools at the nearest power plant – matched the ratio of strontium isotopes in samples collected from sediments at the bottom of the lake. Lake.

"This shows otolith can be used as a biogenic tracker to assess the potential ecological impact of coal ash waste flow in affected waters," said Brandt, who is now a postdoctoral researcher with the U.S. Geological Survey. "While strontium behaves differently from the toxic elements in coal ash waste, it helps us connect high-level elements back to the source of contamination."

Strontium is a trace element that occurs naturally in coal which maintains a unique isotope ratio even after coal burns and coal ash comes into contact with the water environment.

Previous studies have used the ratio of strontium isotopes to track the effects of coal ash on water quality, "but this is the first time we can prove that they can also be used as fingerprints to track the impact of coal ash on living organisms," said Avner Vengosh, professor of geochemistry and water quality at Duke & # 39; s Nicholas School, who co-authored this study.

"This clearly shows strontium in fish must be from coal ash contamination," Vengosh said.

The Duke Team published November 21 peer-reviewed findings in the journal Environmental Science & Technology Letters.

The researchers collected surface water and sediment-based pore water samples from two North Carolina lakes – Lake Mayo and Lake Sutton – that were historically detained to provide cooling water to the nearest power plant and to receive their waste. Lake Sutton is the site of a large coal ash leak to the adjacent Cape Fear River after Hurricane Florence caused flooding this fall.

The researchers also collected surface and pore water samples from two locations located upstream from the lake, and from two other lakes – Lake Tillery and Lake Waccamaw – which were not related to the flow of coal ash waste. Samples are then analyzed in the laboratory, along with largemouth bass otitites from each lake.

"Strontium's isotope ratio in largemouth bass otolith overlaps with the ratio in suitable sedimentary pore waters in all lakes and reservoirs, which is strong evidence that otolith can function as a biogenic tracer from coal ash waste," said Richard Di Giulio, professor Sally Kleberg. Environmental Toxicology at Duke, who co-authored the study.

The ratio of strontium isotopes in surface water samples from lakes does not always match fish samples and pore water samples, Di Giulio explained, but this could be because the surface water ratio varies more over time.

"The findings of this study indicate that otolith studies can add to our existing research efforts," Brandt said. "Water-based strontium isotope tracer only gives us information about the impact of coal ash at a certain point in time, but because the otolite continues to grow during the life span of the fish, we can use time series analysis to determine the waste disposal time or spill back several years. This represents a new and emerging direction in environmental toxicology and water quality research. "

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