Effect of Burn Parameters on PAH Emissions at Conditions Relevant for Prescribed Fires

TL;DR

This study investigates how burn parameters like fuel moisture, heat flux, and oxygen levels influence PAH emissions during prescribed fires, identifying conditions that significantly reduce carcinogenic PAH release and associated health risks.

Contribution

It provides a detailed analysis of how specific burn conditions affect PAH emissions, offering practical guidelines to minimize health hazards from prescribed fires.

Findings

Optimal conditions reduce heavy PAH emissions by up to 77%

Carcinogenic risk can be lowered by more than 50%

Controlled burn parameters can mitigate health hazards

Abstract

Wildfire smoke is a health hazard as it contains a mixture of carcinogenic volatile compounds and fine particulate matter. In particular, exposure to polycyclic aromatic hydrocarbons (PAHs) is a major concern, since these compounds have been recognized as important contributors to the overall carcinogenic risk of smoke exposure. In this work, gas and particle-phase PAH emissions from the combustion of Eastern White Pine (pinus strobus) were quantified using time-of-flight mass spectrometry over a range of burn conditions representative of wildfires and prescribed fires. These experiments allow for controlling conditions of fuel moisture, heat flux, and oxygen concentration to understand their impact on PAH emissions. We find that optimal conditions for fuel moisture content of 20 - 30%, heat load onto the sample of 60 - 70 kW/m$^2$, and oxygen concentrations of the burn environment of 5 - 15% can reduce the emissions of the heavy molar weight PAHs by up to 77%. Our analysis shows that the relative carcinogenic risk can be reduced by more than 50% under optimal conditions, offering a way for reducing emission exposure from forest treatment activities.