Smoke from forest fires can be harmful to human health and ecosystems due to plant toxins present in them, say scientists who detected these toxins in a new study.
The study, which was of Ponderosa pines, was done by scientists at the Department of Energy's Pacific Northwest National Laboratory (PNNL).
The results from the new study also suggest that smoldering fires may produce more toxins than wildfires, which is a reason to keep human exposures to a minimum during controlled burns.
Finding these toxins, known as alkaloids, helps researchers understand how they cycle through earth and air.
Smoke-related alkaloids in the environment can change aquatic and terrestrial ecosystems, as well as where and when clouds form.
"Ponderosa pines are widespread in areas that are prone to forest fires," said PNNL physical chemist Julia Laskin, one of the coauthors of the study. "This study shows us which molecules are in smoke so we can better understand smoke's environmental impact," she added.
As trees and underbrush burn, billowing smoke made up of tiny particles drifts away. The tiny particles contain a variety of natural compounds released from the plant matter.
Researchers have long suspected the presence of alkaloids in smoke or detected them in air during fire season, but no one had directly measured them coming off a fire.
The PNNL researchers had recently developed the technology to pick out alkaloids from the background of similar molecules.
To investigate chemicals given off by fires, the team captured some smoke from test fires organized by Colorado State University researchers.
The scientists collected smoke samples in a device that corrals small particles.
Using high-resolution spectrometry instruments in EMSL, DOE's Environmental Molecular Sciences Laboratory on the PNNL campus, they then determined which molecules the smoke contained.
At EMSL, the researchers used the new methods to glean highly detailed information about the smoke's composition.
The team found a wide variety of molecules.
When they compared their results to other studies, they found that 70 percent of these molecules had not been previously reported in smoke.
In addition, 10 to 30 percent of these were alkaloids, common plant molecules that proved to be quite resistant to the high temperatures of fire.
For future studies, the researchers are developing a method to quantify the alkaloids and related compounds in smoke to better understand their chemical composition and prevalence.