Finding Pollutants In Tree Bark

Tree bark is chock full of fats, making it sop up greasy pollutants in the air. Taking advantage of the bark’s sponge-like quality, researchers have developed an easy and inexpensive method to measure concentrations of flame retardants in pine bark (Environ. Sci. Technol., DOI: 10.1021/es303393z). By pinpointing areas containing trees with high levels of flame retardants, the scientists hope to identify sources of the pollutants.

Flame retardants appear in a wide range of consumer products, such as sofa cushions and mattresses. The chemicals can evaporate from the products into the atmosphere, says Amina Salamova, a researcher in the lab of Ronald A. Hites at Indiana University, Bloomington. Toxicity studies have shown that the compounds can disrupt hormone signaling in animals, such as rats, interfering with the animals’ sexual development.

To study air pollution, environmental scientists normally collect flame retardants by sucking high volumes of air through materials that absorb the pollutants. The devices “are pretty expensive,” says Salamova. Plus, the technique requires transporting the samplers to testing sites, which are sometimes in remote areas. Meanwhile, tree bark just “sits at the site and accumulates air contamination,” she says. “It’s cost effective. It doesn’t require power or major supplies.”

To test tree bark as pollutant samplers, the researchers obtained bark from pine trees at 12 locations on five continents. They mixed the bark with organic solvents to extract the flame retardants. The scientists then analyzed the extracts with gas chromatography and mass spectrometry to identify the chemicals, including Dechlorane plus and pentabromoethylbenzene, and determine their concentrations. These concentrations squared well with measurements taken by collaborators at the same 12 sites using the conventional approach. Salamova next plans to use the method to study flame retardant concentrations in remote areas in the developing world.