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Analysis of indoor aerosol sources from measurements of number size distribution and chemical composition by means of positive matrix factorization

Lazaridis Michalis, Stergios Vratolis , Angeliki Karanasiou, Konstantinos Eleftheriadis

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Indoor exposure of humans to particulate matter depends on a number of key parameters and processes. Occupants and their activities, the outdoor aerosol concentration and the ventilation rate are those parameters considered highly important in indoor air quality (Lazaridis et al., 2008). The objective of the present study is to identify and characterize indoor aerosol sources using both elemental concentrations and number size distribution data. Positive Matrix Factorization analysis (PMF) was employed in this type of indoor aerosol data. Measurements of the indoor aerosol size distribution were carried out in three typical apartments located in the Athens urban area. The size resolved aerosol number concentration was obtained at five minutes intervals using a Scanning mobility particle sizer for the fraction between 10 – 550 nm expressed in mobility diameter (SMPS, DMA model 3071 and CPC 3022A, TSI Inc., USA). The indoor aerosol mass concentration was also determined using a three-stage Dekati impactor. Trace metals and water soluble ions were determined on a 24h basis. Black carbon concentrations (BC) were measured by means of an aethalometer. Only non-smoking residents were considered in this study. Human activity (presence of people, ventilation, vacuuming and cooking) in every flat was recorded in a diary. PMF analysis based on particle size distribution data revealed four sources, Figure 1. The source profiles were identified by relating source contributions with human activity indoors. The first source was assigned to new particle formation mostly associated with cooking (Factor 1). Three outdoor sources were also resolved, related to traffic and other combustion sources (Factor 2, Factor 3), or secondary aerosol in the accumulation mode (Factor 4). High contribution of these outdoor sources to the indoor aerosol number concentrations coincided with periods of increased air exchange between indoors and outdoors. These results suggested that penetration of outdoor particles is the most important parameter significantly affecting the indoor air quality. BC concentrations showed a moderate positive correlation with at least two of those outdoor sources (Factors 3 &4). Elemental, ionic and black carbon concentrations were also subjected to PMF analysis. The chemical profile of the resolved sources was found to be dominated by Fe, Ca, K and Na. Pearson's correlation coefficient between the resolved source contributions and elemental concentrations suggested possible tracers for indoor aerosol sources. Specific metals like Fe may be released during the cooking process (Chao and Cheng, 2002). Figure 1. Number size distribution of the resolved sources Acknowledgements This work was supported by The E.U. contract No (EVK4-CT-2000-0018) under "Urban Aerosol

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