Semi-quantitative characterisation of ambient ultrafine aerosols resulting from emissions of coal fired power stations.

Emissions from coal fired power stations are known to be a significant anthropogenic source of fine atmospheric particles, both through direct primary emissions and secondary formation of sulfate and nitrate from emissions of gaseous precursors. However, there is relatively little information available in the literature regarding the contribution emissions make to the ambient aerosol, particularly in the ultrafine size range. In this study, the contribution of emissions to particles smaller than 0.3 mum in the ambient aerosol was examined at a sampling site 7 km from two large Australian coal fired power stations equipped with fabric filters. A novel approach was employed using conditional sampling based on sulfur dioxide (SO(2)) as an indicator species, and a relatively new sampler, the TSI Nanometer Aerosol Sampler. Samples were collected on transmission electron microscope (TEM) grids and examined using a combination of TEM imaging and energy dispersive X-ray (EDX) analysis for qualitative chemical analysis. The ultrafine aerosol in low SO(2) conditions was dominated by diesel soot from vehicle emissions, while significant quantities of particles, which were unstable under the electron beam, were observed in the high SO(2) samples. The behaviour of these particles was consistent with literature accounts of sulfate and nitrate species, believed to have been derived from precursor emissions from the power stations. A significant carbon peak was noted in the residues from the evaporated particles, suggesting that some secondary organic aerosol formation may also have been catalysed by these acid seed particles. No primary particulate material was observed in the minus 0.3 mum fraction. The results of this study indicate the contribution of species more commonly associated with gas to particle conversion may be more significant than expected, even close to source.

Radiocarbon determination of fossil and contemporary carbon contribution to aerosol in the Pacific Islands.

Combustion emissions are of growing concern across all Pacific Island Countries, which account for >10,000 km2 of the earth's surface area; as for many other small island states globally. Apportioning emissions inputs for Suva, the largest Pacific Island city, will aid in development of emission reduction strategies. Total suspended particulate (TSP) and fine particulate (PM2.5) samples were collected for Suva City, a residential area (Kinoya, TSP) and a mainly ocean-influenced site (Suva Point, TSP) from 2014 to 2015. Percentages of contemporary and fossil carbon were determined by radiocarbon analysis (accelerator mass spectrometry); for non­carbonate carbon (NCC), elemental carbon (EC) and organic carbon (OC). Source contributions to particulate matter were identified and the accuracy of previous emissions inventory and source apportionment studies was evaluated. Suva Point NCC concentrations (2.7 ±â€¯0.4 µg/m3) were four times lower than for City (13 ±â€¯2 µg/m3 in TSP) and Kinoya (13 ±â€¯1 µg/m3 in TSP); demonstrating the contribution of land-based emissions activities in city and residential areas. In Suva City, total NCC in air was 81% (79%-83%) fossil carbon, from vehicles, shipping, power generation and industry; whilst in the residential area, 48% (46%-50%) of total NCC was contemporary carbon; reflecting the higher incidence of biomass and waste burning and of cooking activities. Secondary organic fossil carbon sources contributed >36% of NCC mass at the city and >29% at Kinoya; with biogenic carbon being Kinoya's most significant source (approx. 30% of NCC mass). These results support the previous source apportionment studies for the city area; yet show that, in line with emissions inventory studies, biomass combustion contributes more PM2.5 mass in residential areas. Hence air quality management strategies need to target open burning activities as well as fossil fuel combustion.

Reducing mortality risk by targeting specific air pollution sources: Suva, Fiji.

Health implications of air pollution vary dependent upon pollutant sources. This work determines the value, in terms of reduced mortality, of reducing ambient particulate matter (PM2.5: effective aerodynamic diameter 2.5µm or less) concentration due to different emission sources. Suva, a Pacific Island city with substantial input from combustion sources, is used as a case-study. Elemental concentration was determined, by ion beam analysis, for PM2.5 samples from Suva, spanning one year. Sources of PM2.5 have been quantified by positive matrix factorisation. A review of recent literature has been carried out to delineate the mortality risk associated with these sources. Risk factors have then been applied for Suva, to calculate the possible mortality reduction that may be achieved through reduction in pollutant levels. Higher risk ratios for black carbon and sulphur resulted in mortality predictions for PM2.5 from fossil fuel combustion, road vehicle emissions and waste burning that surpass predictions for these sources based on health risk of PM2.5 mass alone. Predicted mortality for Suva from fossil fuel smoke exceeds the national toll from road accidents in Fiji. The greatest benefit for Suva, in terms of reduced mortality, is likely to be accomplished by reducing emissions from fossil fuel combustion (diesel), vehicles and waste burning.

Airborne ultrafine particles in a Pacific Island country: Characteristics, sources and implications for human exposure.

The Pacific Islands carry a perception of having clean air, yet emissions from transport and burning activities are of concern in regard to air quality and health. Ultrafine particle number concentrations (PNCs), one of the best metrics to demonstrate combustion emissions, have not been measured either in Suva or elsewhere in the Islands. This work provides insight into PNC variation across Suva and its relationship with particle mass (PM) concentration and composition. Measurements over a short monitoring campaign provide a vignette of conditions in Suva. Ambient PNCs were monitored for 8 day at a fixed location, and mobile PNC sampling for two days. These were compared with PM concentration (TSP, PM10, PM2.5, PM1) and are discussed in relation to black carbon (BC) content and PM2.5 sources, determined from elemental concentrations; for the October 2015 period and longer-term data. Whilst Suva City PM levels remained fairly low, PM2.5 = 10-12 µg m-3, mean PNC (1.64 ± 0.02 × 104 cm-3) was high compared to global data. PNCs were greater during mobile sampling, with means of 10.3 ± 1.4 × 104 cm-3 and 3.51 ± 0.07 × 104 cm-3 when travelling by bus and taxi, respectively. Emissions from road vehicles, shipping, diesel and open burning were identified as PM sources for the October 2015 period. Transport related ultrafine particle emissions had a significant impact on microscale ambient concentrations, with PNCs near roads being 1.5 to 2 times higher than nearby outdoor locations and peak PNCs occurring during peak traffic times. Further data, particularly on transport and wet-season exposures, are required to confirm results. Understanding PNC in Suva will assist in formulating effective air emissions control strategies, potentially reducing population exposure across the Islands and in developing countries with similar emission characteristics. Suva's PNC was high in comparison to global data; high exposures were related to transport and combustion emissions, which were also identified as significant PM2.5 sources.

Congenital erosive and vesicular dermatosis healing with reticulated supple scarring.

Three children had an extensive erosive and vesicular dermatosis at birth that healed with supple reticulated scarring. This article discusses the differential diagnosis and pathogenesis of the disorder in these patients, and makes recommendations for medical evaluation and parent counseling.

Formate species in the low-temperature oxidation of dimethyl ether.

The oxidation of dimethyl ether (DME, 340 ppm in 10% O2) has been studied experimentally in an atmospheric pressure laminar flow reactor in the temperature range from 240 degrees C to 700 degrees C for residence times in the range 2-4 s. The influence of nitric oxide additions up to 620 ppm to the feed gases has also been investigated. Products of reaction were determined by FTIR. In the absence of NO, reaction is first detected at about 260 degrees C. The products in the low-temperature region include formaldehyde (HCHO), and formic acid (HCOOH). The addition of NO leads to the appearance of methyl formate (CH3OCHO). While the overall behaviour of the system can be explained qualitatively in terms of typical low-temperature hydrocarbon ignition, recently published chemical kinetic models for DME ignition do not allow for the formation of these formate species. We find no experimental evidence for the formation of hydroperoxymethyl formate (HPMF, HOOCH2OCHO) which is predicted by the models to be a significant stable intermediate at temperatures below 350 degrees C. Since both formic acid and methyl formate have potentially harmful health effects, these observations may have significant implications for use of DME as a diesel fuel.