Smoke Keeps Changing Even After the Wildfire: Tracking Chemical Reactions in Ultrafine Dust [Reading Science]

KBSI and Kyungpook National University Analyze Ultrafine Dust from Hamji Mountain Wildfire at the Molecular Level
Nitrogen-Containing Pollutants Increase 3.4-Fold
Potentially Harmful Substances Also Identified

A new study has found that the impact of air pollution caused by wildfire smoke does not disappear immediately after the flames subside. Researchers observed that substances emitted from wildfires continue to react with other components in the atmosphere, leading to the formation of new compounds through a process known as "chemical aging." The research team also identified potential candidates among these new substances that may be harmful to living organisms.

The Korea Basic Science Institute (KBSI) announced on September 28 that Dr. Younghwan Kim's research team from the Materials Research Division, in collaboration with Professor Sunghwan Kim's team at Kyungpook National University, analyzed ultrafine dust affected by wildfires and traced its chemical changes in the atmosphere.

A schematic diagram showing the composition and toxicity assessment study of ultrafine particulate matter from wildfires. Provided by the research team (Image generated by ChatGPT)

The research team compared ultrafine dust samples collected during the wildfire on Hamji Mountain in Daegu in April 2025 with samples taken approximately two weeks after the fire ended. Analysis of nine types of nitrogen-containing organic pollutants—known to be generated during combustion processes such as wildfires—revealed that the average concentration during the fire was about 3.4 times higher than after the event.

The team then used an ultra-high-resolution mass spectrometer (FT-ICR MS) to analyze the molecular formulas of thousands of components present in the ultrafine dust. They found that the molecular composition of organic compounds containing oxygen and nitrogen changed noticeably in the samples affected by the wildfire.

The researchers described the process wherein substances emitted by wildfires undergo continuous chemical reactions in the atmosphere, resulting in changes to their molecular composition, as "atmospheric aging." This means that even after a wildfire ends, the substances already released can alter their properties while traveling through the air by reacting with other compounds.

Combining Real-World Analysis with Computer Predictions to Track Harmful Candidates

However, the precise structures of these compounds cannot be determined solely from the molecular formulas obtained through mass spectrometry, since different compounds can share the same molecular formula but have distinct structures.

To address this, the team used computer simulations to predict possible chemical reactions. They selected 12 substances related to wildfires and urban air pollution, then calculated what new compounds might form when these substances react in the atmosphere. The molecular formulas of the predicted products were then compared with those actually detected in the ultrafine dust.

The results revealed that, among the substances studied, the products predicted to be generated from limonene matched most frequently with the actual analysis results during the wildfire period.

Photo of co-researchers. (From left) Geondo Park, PhD candidate at Kyungpook National University (co-first author), Yoonkyung An, senior researcher at the Capital Area Center of Korea Basic Science Institute (co-first author), Younghwan Kim, senior researcher at the Materials Research Division of Korea Basic Science Institute (co-corresponding author), Sunghwan Kim, professor at Kyungpook National University (co-corresponding author). Provided by Korea Basic Science Institute

Based on the predicted molecular structures, the research team also analyzed the potential toxicity of these candidates in aquatic organisms. Certain nitrogen-containing compounds derived from 'beta-pinene' and 'alpha-pinene,' which are naturally emitted volatile substances from pine trees and other sources, were predicted to have relatively high toxicity.

However, this prediction was not confirmed through actual biological testing. Further experiments are needed to determine if these candidate compounds truly exist in ultrafine dust in their predicted structures and to assess their toxicity levels. The fact that the study focused on a specific wildfire and a single observation site is also a limitation.

Dr. Younghwan Kim of KBSI stated, "To fully understand the impact of wildfires, it is important to examine not only the pollutants emitted during the fire, but also the secondary pollutants newly formed as these substances travel and change in the atmosphere. The significance of this study lies in combining ultra-high-resolution mass spectrometry with computer simulations to trace these changes at the molecular level and assess their potential risks."

The results of this research were published online on September 5 in 'Environmental Research,' an international journal in the field of environmental health.

This content was produced with the assistance of AI translation services.