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An acid assisted closed vessel microwave digestion procedure was developed for the treatment of fine airborne particulate matter that allows elemental iodine to be solubilised simultaneously with other metallic elements. This procedure is an improvement over existing methods as it allows the iodine to be safely digested from the filter media (polypropylene or cellulose) in less than one hour in up to 70–100% recoveries, without requiring an overnight predigestion step or the addition of reducing agents, with a microwave temperature of 185 °C and the use of 65% HNO3. A range of filters were investigated to determine the material that has the best properties for microwave digestion that also enabled the deposited iodine present in total suspended particles (TSP) to be rapidly fully digested and quantitatively analyzed using inductively coupled plasma-mass spectrometry (ICP-MS).

Burning of joss paper and incense is still a very common traditional custom in countries with a majority Chinese population. The Hungry Ghost Festival which is celebrated in the 7 month of the Chinese calendar is one of the events where joss paper and incense are burned as offerings. This study investigates the impact of the Ghost Month Festival (open burning event) on air quality by analysis of the chemical composition of particulate matter (PM) and rainwater samples collected during this event, compared with data collected throughout the year, as well as bottom ash samples from burning the original joss paper and incense. The results showed that the change in the chemical composition of the rainwater and PM2.5 (PM ≤ 2.5 μm) atmospheric samples could be correlated directly with burning events during this festival, with many elements increasing between 18% and 60% during August and September compared to the yearly mean concentrations. The order of percentage increase in elemental composition (in rain water and PM2.5) during the Hungry Ghost Festival is as follows: Zn > Ca > K > Mg > Fe > Al > Na ∼ Mn ∼ Ti ∼ V > Cu > As > Ni > Co > Cd > Cr > Pb. The chemical composition of the original source materials (joss paper and incense for combustion) and their associated bottom ash were analysed to explain the impact of burning on air quality. MOE (Min. of Education, S’pore) Published version