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Environmental cycling of the toxic metal mercury (Hg) is ubiquitous, and still not completely understood. Volatilisation and emission of mercury from vegetation, litter and soil during burning represents a significant return pathway for previously-deposited atmospheric mercury. Rates of such emission vary widely across ecosystems as they are dependent on species-specific uptake of atmospheric mercury as well as fire return frequencies. Wildfire burning in Australia is currently thought to contribute between 1 and 5% of the global total of mercury emissions, yet no modelling efforts to date have utilised local mercury emission factors (mass of emitted mercury per mass of dry fuel) or local mercury emission ratios (ratio of emitted mercury to another emitted species, typically carbon monoxide). Here we present laboratory and field investigations into mercury emission from burning of surface fuels in dry sclerophyll forests, native to the temperate south-eastern region of Australia. From laboratory data we found that fire behaviour — in particular combustion phase — has a large influence on mercury emission and hence emission ratios. Further, emission of mercury was predominantly in gaseous form with particulate-bound mercury representing

Air quality standards for settleable particulate matter (SPM) are found in many countries around the world. As well known, annoyance caused by SPM can be considered a community problem even if only a small proportion of the population is bothered at rather infrequent occasions. Many authors have shown that SPM cause soiling in residential and urban environments and degradation of materials (eg, objects and surface painting) that can impair the use and enjoyment of property and alter the normal activities of society. In this context, this paper has as main contribution to propose a guidance to establish air quality standards for annoyance caused by SPM in metropolitan industrial areas. To attain this objective, a new methodology is proposed which is based on the nonlinear correlation between the perceived annoyance (qualitative variable) and particles deposition rate (quantitative variable). Since the response variable is binary (annoyed and not annoyed), the logistic regression model is used to estimate the probability of people being annoyed at different levels of particles deposition rate and to compute the odds ratio function which gives, under a specific level of particles deposition rate, the estimated expected value of the population perceived annoyance. The proposed methodology is verified in a data set measured in the metropolitan area of Great Vitoria, Espirito Santo, Brazil. As a general conclusion, the estimated probability function of perceived annoyance as a function of SPM has shown that 17% of inhabitants report annoyance to very low particles deposition levels of 5 g/(m2∙30 days). In addition, for an increasing of 1 g/(m2∙30 days) of SPM, the smallest estimated odds ratio of perceived annoyance by a factor of 1.5, implying that the probability of occurrence is almost 2 times as large as the probability of no occurrence of annoyance.

On 9 February 2014, embers from a nearby grass/shrub fire spotted into an unused part of the Hazelwood open-cut brown coal mine located in the Latrobe Valley of Victoria, Australia and started a fire that spread rapidly and extensively throughout the mine under strong south-westerly winds and burned over a period of 45 days. The close proximity of the town to the coal mine and the low buoyancy of the smoke plume led to the accumulation of dense smoke levels in the township of Morwell (population of 14,000) particularly under south-westerly winds. A maximum daily PM2.5 concentration of 731 μg m−3 and 8-h CO concentration of 33 ppm were measured at Morwell South, the closest residential area located approximately 500 m from the mine. These concentrations were significantly higher than national air quality standards. Air quality monitoring undertaken in the Latrobe Valley showed that smoke from the Hazelwood mine fire affected a wide area, with particle air quality standards also exceeded in Traralgon (population of 25,000) located approximately 13 km from the mine. Pollutant levels were significantly elevated in February, decreased in March once the fire abated and then returned to background levels once the fire was declared safe at the end of March. While the smoke extent was of a similar order of magnitude to other major air pollution events worldwide, a closer look at emissions ratios showed that the open combustion of lignite brown coal in the Hazelwood mine was different to open combustion of biomass, including peat. It suggested that the dominant combustion process was char combustion. While particle and carbon monoxide monitoring started approximately 4 days after the fire commenced when smoke levels were very high, targeted monitoring of air toxics only began on 26 February (17 days after the fire) when smoke levels had subsided. Limited research on emission factors from open-cut coal mine fires make it difficult to assess the likely concentrations of air toxics emitted during the initial more intense period of the fire.

The 2014 fire in the Hazelwood open-cut mine of brown coal, located in the State of Victoria (Australia), burned for 45 days. The fire sent dense smoke over the nearby town of Morwell and beyond, resulting in one of the worst air quality incidents in Victoria. Precision air monitoring of PM2.5 (particulate matter 2.5 μm or less in diameter) and carbon monoxide (CO), which has been reported previously, started a few days after the fire at two locations in Morwell and measured PM2.5 levels up to 19 times higher than the 24-h Australian air quality standard. Because of the sparseness of the monitors and the fact that the fire was most intense prior to the start of the air monitoring, it is likely that the smoke concentrations in Morwell were even greater than measured. Thus, the concentration measurements are insufficient in time and space for a comprehensive study of exposure and health impacts due to the smoke. We reconstruct the hourly spatial distributions of smoke (as represented by PM2.5 and CO) in and around Morwell by first developing a rigorous methodology for estimating the fire emissions, and then using them in a high-resolution prognostic meteorological and dispersion model with local wind data assimilation and an appropriate plume rise mechanism. Larger-scale modelling is also conducted to estimate the background concentrations without the mine fire. The model simulates the number of observed exceedances and the observed maximum concentrations exceeding the air quality standards for both PM2.5 and CO within a factor of 2. At the monitor south of Morwell near the fire, the model predicts hourly PM2.5 and CO concentrations as high as 3730 μg m−3 and 58.6 ppm, respectively, in the early phase of the fire; these levels are much higher than those recorded by the subsequent air monitoring. The modelled PM2.5 fields are being used by other researchers to estimate the impact of smoke exposure on health outcomes in the local community.

In the Huon Valley, Tasmania, current public perception is that smoke from regeneration burning is the principal cause of pollution events in autumn. These events lead to exceedences of national air quality standards and to significant health impacts on the rural population. To date there is little data on the significance of the impact. The aim of the study was to quantitatively assess the seasonal atmospheric particle loadings in the Huon Valley and determine the impact of smoke pollution. The study monitored fine (PM 2.5 ) and coarse (PM 10 ) particle concentrations and their chemical composition at two locations in the Huon Valley, Geeveston, an urban site and Grove, a rural site, between March 2009 and November 2010. The monitoring program clearly showed that biomass burning was a significant source of PM 2.5 in the Huon Valley, leading to exceedences of the 24 h PM 2.5 Ambient Air Quality National Environment Protection Measures advisory standard on a number of occasions. Significant increases of PM 2.5 concentrations above background occurred during periods of prescribed burning as well as during the winter season. Although the intensity of emissions from prescribed burns (PB) and residential woodheaters (WH) was similar, emissions from WH were the largest source of PM 2.5 , with a contribution of 77% to the ambient PM 2.5 load compared to an 11% contribution from PB. The results have also shown a greater impact on air quality at the urban site than at the rural site, indicating that PM 2.5 concentrations are primarily influenced by localised sources rather than by regional pollution. The potential impact on local residents of the high PM concentrations during the PB and WH season was assessed. WH pollution is largely a persistent night-time issue in contrast to PB events which generally occur during the day and are of short duration. Due to the long persistence of high PM concentrations in winter, indoor PM concentrations are unlikely to be substantially lower than outdoor ones. However plume strikes are usually of shorter duration and therefore it may be possible to avoid exposure to PB events by remaining indoors.

In rural towns of southern Australia, smoke from biomass burning such as prescribed burning of forests, wildfires and stubble burning is often claimed to be the major source of air pollution. To investigate the validity of this claim, ambient measurements of PM 2.5 and ozone were made in two rural locations in southern Australia between 2006 and 2008. In order to distinguish PM 2.5 associated with smoke from other sources of particulate pollution, PM 2.5 samples were analysed for specific smoke tracers, levoglucosan, non sea-salt potassium (nssK + ) and oxalate. Monitoring was also undertaken in four homes to determine the extent to which ambient pollutants from prescribed burning penetrate indoors into houses. Monitoring clearly showed that, on occasions, air quality in rural areas is significantly affected by smoke from biomass combustion with PM 2.5 showing the greatest impact. Concentrations of PM 2.5 increased significantly above background levels at both sites during periods of wildfire and prescribed fire leading to exceedences of the 24-h PM 2.5 Air National Environment Protection Measure (NEPM) Advisory standard. The 1-h and 4-h ozone NEPM standards were exceeded only during protracted forest wildfires. The impact of prescribed burning on the indoor air quality of residences depended on the duration of the smoke event and the ventilation rate of the houses. During short-duration events indoor air quality was determined by household activities. During events that persisted for several days, indoor air quality was determined by external conditions coupled with management of household ventilation rate.

Naphthalene and alkylnaphthalenes are abundant semi-volatile polycyclic aromatic hydrocarbons (PAHs) present in ambient air as a result of emissions from combustion sources. At ambient temperatures, these PAHs can undergo atmospheric gas-phase reactions with hydroxyl (OH) radicals. We report here on environmental chamber reactions simulating ambient photooxidation of volatilized diesel fuel PAHs and demonstrate for the first time that dimethylnitronaphthalenes and/or ethylnitronaphthalenes identified as formed from the OH radical-initiated reactions of alkyl-PAHs present in diesel fuel are also present in ambient air samples collected in Southern California.