Fine particle pollution during megafires contains potentially toxic elements.

Area of Science:

• Environmental Science
• Atmospheric Chemistry
• Toxicology

Background:

• The 2019-2020 Australian 'Black Summer' wildfires generated extensive particulate matter (PM) pollution.
• Understanding the toxicological profile of wildfire-derived PM is crucial for assessing environmental and health impacts.
• Building HVAC filters provide a method for capturing urban PM for analysis.

Purpose of the Study:

• To characterize the potentially toxic fingerprint of PM from Australian wildfires.
• To compare wildfire PM composition and properties with ambient urban PM.
• To assess the magnitude and sources of PM exposure during wildfire events.

Main Methods:

• Analysis of PM collected from building HVAC filters in Sydney during wildfire events and a reference period.
• Characterization of PM physical properties (size, shape) and elemental composition.
• Assessment of atmospheric PM and meteorological data to determine exposure levels and sources.

Main Results:

• Wildfire PM significantly exceeded national standards on 19% of days, with finer, more spherical particles.
• Wildfire PM showed higher concentrations of SO42--S and NO3--N, while reference PM had higher PO43--P.
• Elevated levels of F-, Cl-, Mn, Co, and Sb were found in wildfire PM, with enhanced Hg solubility.

Conclusions:

• Wildfire smoke is a major contributor to urban PM pollution with a distinct toxicological profile.
• The findings enhance understanding of human and ecosystem exposure to toxic components in wildfire smoke plumes.
• This research provides critical data for risk assessment in downwind regions affected by wildfires.