Source apportionment and analysis on ambient and personal exposure samples with a combined receptor model and an adaptive blank estimation strategy

The objective of this study is to characterize the airborne particle sources that are common to four different environments (personal, residential indoor, residential outdoor and ambient) and to study the relationships between PM _2.5 exposure and emission sources. Twenty-four hour integrated filter samples were collected on 7 days in each of 4 seasons from June 2000 to May 2001 for 38 individuals in four different type of environments in Raleigh and Chapel Hill, NC. An expanded receptor model (since different environments were analyzed simultaneously, it was also called combined model) was established for this study. The organic carbon (OC) and the first component of OC (OC1) measurements were not blank corrected in this study, so an adaptive blank estimation process was integrated into the combined receptor model and the best OC and OC1 blank values were estimated while the source profiles were being extracted. Four external sources (motor vehicle emission, soil, secondary sulfate, and secondary nitrate) and four internal sources (environmental tobacco smoking and its mixture, personal care/activity, Cu-factor mixed with indoor soil, and cooking) were resolved. The contributions of each source to the different environments were estimated. The contribution of external sources to the composition of personal and indoor samples, and various infiltration factors were also discussed. This study also provided a novel method for blank value estimation.