Microscopic Morphology and Size Distribution of Residential Indoor PM10 in Beijing City

To investigate characteristics of airborne PM10 in residences in Beijing City the indoor PM10 concentrations, morphology and size distribution were measured using a scanning electron microscope coupled with an energy dispersive X-ray micro-analyser and image analysis. PM10 samples were collected in four homes and from the nearby outdoor environment during the winter season. The results showed that the mean 12-h indoor PM10 concentration was 109.9 g/m3 and the corresponding outdoor level was 179.8 g/m3. Indoor PM10 single particles were subdivided into 5 microscopic types according to their microscopic characteristics and morphologies and included soot aggregates, coal fly ash, mineral, biological and unresolved particles. Each particle type had a different contribution to the PM10 composition which were dominated by soot aggregates in both indoor and outdoor air. Numbersize distribution of PM10 in the residences displayed a bimodal pattern with peaks in 0.1 0.7 m and 1 2.5 m ranges. Coal fly ash exhibited a unimodal pattern in indoor and outdoor air with a peak in 0.1 0.5 m range. Mineral particles showed a bimodal number-size distribution in homes but in the outdoor air they exhibited a unimodal pattern perhaps because of the air temperature.