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.
"The research significantly expanded the previous observations," said aerosol chemist and coauthor Alexander Laskin.
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. Plants often use alkaloids for protection, because they can poison other plants and animals, including humans. Alkaloids also have medicinal value (caffeine and nicotine, for example, are well-known alkaloids that aren't found in pine trees).
A large percentage of the alkaloids were those that carry biologically useful nitrogen through atmospheric, terrestrial and aquatic environments. Because of this, the results suggest smoke might be an important step in this transport. Also, the nitrogen-containing alkaloids have a basic pH, which can make cloud-forming particles less acidic, and in turn impact cloud formation that is critical to global agriculture and water supplies.
The researchers also found that the abundance of alkaloids depends on how vigorously the fire burns. Smoldering fires such as those in controlled burns produce more of the compounds than blazing fires such as those fanned by high winds. Because some plant alkaloids might be harmful, the result could affect planned fires upwind of human populations.
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.
|Contact: Mary Beckman|
DOE/Pacific Northwest National Laboratory