Elsevier

Environment International

Volume 91, May 2016, Pages 230-242
Environment International

Characterisation of the impact of open biomass burning on urban air quality in Brisbane, Australia

https://doi.org/10.1016/j.envint.2016.02.030Get rights and content

Highlights

  • A comprehensive, multi-pollutant, air quality study was conducted in Brisbane.

  • Pollutant concentrations were compared between burning and non-burning events.

  • Source attribution tested using biomass burning tracers, AMS and back trajectories

  • Open biomass burning emissions significantly reduced air quality in Brisbane.

  • This is the first quantitative study in south hemisphere to report on the impact of open biomass burning on urban air quality.

Abstract

Open biomass burning from wildfires and the prescribed burning of forests and farmland is a frequent occurrence in South-East Queensland (SEQ), Australia. This work reports on data collected from 10 to 30 September 2011, which covers the days before (10–14 September), during (15–20 September) and after (21–30 September) a period of biomass burning in SEQ. The aim of this project was to comprehensively quantify the impact of the biomass burning on air quality in Brisbane, the capital city of Queensland. A multi-parameter field measurement campaign was conducted and ambient air quality data from 13 monitoring stations across SEQ were analysed. During the burning period, the average concentrations of all measured pollutants increased (from 20% to 430%) compared to the non-burning period (both before and after burning), except for total xylenes. The average concentration of O3, NO2, SO2, benzene, formaldehyde, PM10, PM2.5 and visibility-reducing particles reached their highest levels for the year, which were up to 10 times higher than annual average levels, while PM10, PM2.5 and SO2 concentrations exceeded the WHO 24-hour guidelines and O3 concentration exceeded the WHO maximum 8-hour average threshold during the burning period. Overall spatial variations showed that all measured pollutants, with the exception of O3, were closer to spatial homogeneity during the burning compared to the non-burning period. In addition to the above, elevated concentrations of three biomass burning organic tracers (levoglucosan, mannosan and galactosan), together with the amount of non-refractory organic particles (PM1) and the average value of f60 (attributed to levoglucosan), reinforce that elevated pollutant concentration levels were due to emissions from open biomass burning events, 70% of which were prescribed burning events. This study, which is the first and most comprehensive of its kind in Australia, provides quantitative evidence of the significant impact of open biomass burning events, especially prescribed burning, on urban air quality. The current results provide a solid platform for more detailed health and modelling investigations in the future.

Introduction

There are two types of biomass burning events: open biomass burning (such as prescribed burning, agricultural waste burning, field burning, land clearing, savannah and grassland fires, forest fires, bushfires and wildfire) and enclosed biomass burning (such as domestic biofuel burning for cooking and heating, charcoal production etc). Open biomass burning is receiving increased scientific attention at present, since it results in the emission of a substantial amount of gaseous and particulate matter (PM) into the atmosphere, which not only has the potential to degrade local and regional air quality, but it also contributes significantly to regional and global atmospheric dynamics (Ward and Hardy, 1991, Ramanathan et al., 2001, Gonzalez-Perez et al., 2004, Reid et al., 2005, Naeher et al., 2007, de Oliveira et al., 2011, Portin et al., 2012, Cisneros et al., 2012, Keywood et al., 2013). One of the main differences between the two types of burning is that soil heating will occur during open biomass burning. When the soil temperature is sufficiently elevated, a greater number of particles and chemicals, such as NOx, N2O, Al2O3, SiO, CaO, FeO, Fe2O3, TiO2, polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD and PCDF), as well as deposited radioactive materials will be released from the soil into the air (Williams et al., 1992, Jimenez et al., 2006, Black et al., 2012, Evangeliou et al., 2014). In addition, combustion efficiency would be lower for open biomass burning, because there is no way to control the fire, and incomplete combustion would result in a wider variety of combustion products. Open biomass burning consumes 65% of all biomass fuel and it is responsible for 65–70% of the carbon emissions from biomass burning globally (Andreae and Merlet, 2001). It also emits a greater amount, and a wider distribution of chemical compounds and particles than enclosed biomass burning. Van der Werf et al. (2010) estimates that global open biomass burning accounts for about 20% of fossil fuel carbon emissions released into the atmosphere each year.

A large number of open biomass burning events occur around the world each year, however reports of their impact on urban air quality are scarce in the literature. Phuleria et al. (2005) examined the impact of the 2003 Southern California wildfires on air quality in urban Los Angeles and found that wildfires caused the greatest increase in PM10 levels (by a factor of 3–4) and lesser increases in CO, NO and particle number (PN) (by a factor of 2). NO2 levels remained essentially unchanged, and O3 concentrations dropped during the fire episode. The impact of the 2009 Attica wildfires on air quality in urban Athens was investigated by Amiridis et al. (2012). The results showed that PM10, PM2.5 and NOx concentrations increased from 30 μg m 3 to 62 μg m 3, 24 μg m 3 to 59 μg m 3 and 10 μg m 3 to 30 μg m 3, respectively, while O3 concentrations decreased slightly during the wildfire period. However, Pfister et al. (2008) and Wonaschutz et al. (2011) reported that O3 concentrations increased during the 2007 California wildfires and during the 2009 Station Fire in Los Angeles County, respectively. Targino et al. (2013) reported that during an agricultural fire, PM10, PM2.5, CO and O3 concentrations in Stockholm increased, exceeding the European Union PM10 daily limit value of 50 μg m 3. The impact of agricultural waste burning on urban air quality in China was studied by Tao et al. (2013) and Cheng et al. (2014), in which overall PM2.5 concentration was found to increase from 116 μg m 3 to 157 μg m 3 in Chengdu and from 82 μg m 3 to 144 μg m 3 in Shanghai, respectively. Recently, Kang et al. (2014) investigated the impact of a series of wildfires in Quebec on downwind urban air quality in Boston and found that the temporal trend in PM2.5 concentration showed a peak of 106 μg m 3 in 2002 and 151 μg m 3 in 2010.

The potential health impacts of exposure to open biomass burning emissions is a growing concern, due to increased evidence linking it with a variety of human health effects (Naeher et al., 2007, Dennekamp and Abramson, 2011, Price et al., 2012). For example, Holstius et al. (2012) recently reported that during the 2003 Southern California wildfires, exposure to wildfire PM in utero was associated with a slightly reduced average birth weight among infants, and the extent and increasing frequency of wildfire events may have ongoing implications for infant health and development. Wegesser et al. (2009) found that wildfire PM contained chemical components which were toxic to the lung, especially to alveolar macrophages, and more toxic than equal doses of PM collected from ambient air in the same region during a comparable season. On an equal mass basis, coarse PM from wildfires is about four times more toxic to macrophages than PM (with the same size) collected from ambient air (without the influence of wildfires) from the same region and season (Franzi et al., 2011). This is due to the wildfire PM, which rapidly killed macrophages in the cell culture, at relatively low doses.

Wildfires and prescribed burning are a frequent occurrence in Australia, with prescribed burns conducted each year across the country, for fuel management and/or ecological purposes (Reisen and Brown, 2009). About forty thousand fires of various sizes are observed per year in Australia (Bryant, 2008) and their emissions are a major source of air pollution in urban environments, during periods of intensive burning (Radhi et al., 2012). For example, in the city of Sydney, of the 256 days on which PM10 reached or exceeded the 95th percentile, a cause was identified for 172 days (67%), and for 162 (94%) of them it was attributed to bushfire smoke (Johnston et al., 2011). A number of studies on the effect of open biomass burning smoke on health have been conducted for the major cities in Australia, including Melbourne, Sydney, Brisbane and Darwin (Dennekamp and Abramson, 2011), as well as for firefighters (Reisen et al., 2011a). The results indicate that the association between respiratory morbidity and exposure to bushfire smoke is consistent with the associations found with urban air pollution (Chen et al., 2006, Tham et al., 2009, Morgan et al., 2010, Dennekamp and Abramson, 2011). Cardiovascular admissions had the strongest association with exposure to bushfire particles, especially for fine particles (PM2) (Crabbe, 2012). Recently, Johnston et al. (2014) reported that open biomass burning smoke events were associated with an immediate increase in presentations for respiratory conditions and a lagged increase in attendance for ischaemic heart disease and heart failure. However, studies on the impact of open biomass burning on urban air quality and the analysis of open biomass burning smoke are very scarce (De Vos et al., 2009). So far, only three studies have characterised the impact of open biomass burning on air quality in Australia. Reisen et al. (2011b; 2013) reported the impacts in a rural area in southern Australia and in a small town in Tasmania, respectively, while the study by Williamson et al. (2013) was limited to documenting higher PM2.5 concentrations when smoke plumes reached urban areas in Melbourne and Sydney. None of the three studies provided and/or generated a more comprehensive characterisation of the impact of open biomass burning on air quality in a larger urban area within Australia.

Due to its associated temperature increases, climate change may also increase wildfire activity (Moritz et al., 2012, Oris et al., 2014). Given the scale of open biomass burning that occurs annually, as well as the population density in urban areas, it is necessary to gain an understanding and quantify the impacts of open biomass burning on urban air quality, which was the aim of the current study. The objectives of this study were to: (1) collect data from before, during and after a period of open biomass burning in Brisbane; (2) quantify the impact of biomass burning on urban air quality; (3) analyse the absolute and relative increase of pollutants during the burning period; (4) determine whether pollutant concentrations were spatially homogeneous during the burning period; and (5) compare the results with data available in the literature.

Section snippets

Material and methods

September is typically a period when prescribed burning is conducted. Following significantly reduced visibility in Brisbane city, we confirmed that several open biomass burning events were occurring within SEQ at the time. This gave a signal to commence comprehensive field measurements of particle number concentration, chemical composition, elemental carbon (EC), organic carbon (OC), biomass burning organic tracers and volatile organic compounds (VOCs), in order to characterise and quantify

Results and discussion

In terms of meteorological conditions, the weather was warmer (on average by about 2 °C) and drier (on average by about 8%) during the burning period, and average wind speed was lower in comparison to the non-burning period. The dominant wind directions were between SSW and WSW in the morning and between NNE and ENE in the afternoon (see Supplementary Table S2). Estimated daytime (at 9:00 am and 3:00 pm) atmospheric mixing layer heights before, during and after biomass burning events are presented

Conclusions

A number of air pollution indicators were analysed to quantify the impact of open biomass burning on air quality in and around Brisbane during 15–20 September 2011. The results showed that during the open biomass burning period, Brisbane's air quality deteriorated significantly, especially in terms of particle mass, O3 and SO2 concentrations, which exceeded air quality WHO guidelines. The average diurnal variation of pollutant concentrations, together with particle OC and EC data, particle

Acknowledgement

We would like to thank Mr Don Neale from the Queensland Department of Science, Information Technology, Innovation and the Arts (DSITIA) for supplying the air quality data and for useful discussions. We also would like to thank the members of the ILAQH, QUT, in particular, Ms Rachael Appleby and Ms Chantal Labbé, for their assistance in numerous ways. The authors gratefully acknowledge the NOAA Air Resources Laboratory (ARL) (Draxler and Rolph, 2003) for the provision of the HYSPLIT transport

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