Estimating NH3 and PM2.5 emissions from the Australia mega wildfires and the impact of plume transport on air quality in Australia and New Zealand

Abstract

Due to the highly flammable biota and a shortfall of precipitation in Australia, wildfires (bushfires) are connected with Australia's ecology and culture. These wildfires affect air quality, emitting ammonia (NH₃) and fine particulate matter (PM_2.5), among other pollutants, into the atmosphere. Record breaking temperatures and drought contributed to the unprecedented 2019–2020 Australian wildfire season in Southeastern Australia. The objective of this study is to calculate emissions of PM_2.5 and NH₃ from wildfires from December 29, 2019, to January 4, 2020 and to analyze the air quality impact on Southeast Australia associated with these mega wildfires. Emissions of PM_2.5 and NH₃ were calculated using a combination of satellite data for burn area and land classification and emissions factors from the literature. The impact of PM_2.5 in Southeast Australia, Southwest shore of New Zealand, and the inner part of Australia were estimated by performing a Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) analysis. The results of this work show that fire activity in the study region produced 526 569 125 kg of NH₃ and 41 167 586 kg of PM_2.5 during the period of interest. Between December 29, 2019, and January 4, 2020, hourly concentrations of PM_2.5 reached 2496.1 μg m⁻³ in Australia and 48.8 μg m⁻³ in New Zealand, exceeding the national standard of 25 μg m⁻³ a total of 100 and 2 times, respectively, which suggests the influence the fires have on air quality in the region.