Simulation Comparisons of Particulate Emissions from Fires under Marginal and Critical Conditions

Alexander J Josephson,Daniel Castaño,Marlin J Holmes,Rodman R Linn

doi:10.3390/atmos10110704

Alexander J Josephson, Daniel Castaño + Show 2 more

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https://doi.org/10.3390/atmos10110704

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Journal: Atmosphere	Publication Date: Nov 13, 2019
Citations: 3	License type: CC BY 4.0

Affiliation: Los Alamos National Laboratory

Abstract

Using a particulate emissions model developed for FIRETEC, we explore differences in particle emission profiles between high-intensity fires under critical conditions and low-intensity fires under marginal conditions. Simulations were performed in a chaparral shrubland and a coniferous pine forest representative of the southeast United States. In each case, simulations were carried out under marginal and critical fire conditions. Marginal fire conditions include high moisture levels and low winds, often desired for prescribed fires as these conditions produce a low-intensity burn with slower spread rates. Critical fire conditions include low moisture levels and high winds, which easily lead to uncontrollable wildfires which produce a high-intensity burn with faster spread rates. These simulations’ resultant particle emission profiles show critical fire conditions generate larger particle emission factors, higher total mass emissions, and a higher lofting potential of particles into the atmosphere when compared against marginal fire conditions but similar particle size distrubtions. In addition, a sensitivity analysis of the emissions model was performed to evaluate key parameters which govern particle emission factor and particle size.

Highlights

Smoke emissions from fires are governed by both processes in the source regime, which is the generation and immediate emission of species local to the flames, and in the plume regime, which is the subsequent evolution and transport of emissions
Perhaps the most helpful work done with regard to smoke processes in the source regime comes from the development of a continually expanding emission factor inventory [6,7,8]
If there is a disadvantage of a prescribed fire it is that emitted particles from ground fires will tend to be slightly smaller than particles emitted from canopy fires which frequently occur in uncontrolled wildfires

Summary

Introduction

Smoke emissions from fires are governed by both processes in the source regime, which is the generation and immediate emission of species local to the flames, and in the plume regime, which is the subsequent evolution and transport of emissions. The inventory, which has been expanded with an extensive effort in the last few decades, contains experimental and field measurements of emission factors classified in a variety of ways These classifications may come in the form of: the source fuel (i.e., biomass species [9]), ecosystem (i.e., grassland vs conifer forest vs boreal forest [10]), environment (i.e., laboratory vs open-field vs closed-forest [6]), or landscape (i.e., cityscape vs wildlands [11]), just to name a few. Inventories can differ greatly in their predictions and can be difficult to effectively use In part, this comes from the extensive complications in measuring speciation of smoke effectively [12] and the variation in techniques or methods, used to obtain species identities and concentrations [6]. It can be difficult to inventory a fire by its characteristics: is it more important that a particular fire was predominately

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