Development of a modified factor analysis/multiple regression model to apportion suspended particulate matter in a complex urban airshed

Abstract

A modified factor analysis/multiple regression (FA/MR) receptor-oriented source apportionment model has been developed which permits application of FA/MR statistical methods when some of the tracers are not unique to an individual source type. The new method uses factor and regression analyses to apportion non-unique tracer ambient concentrations in situations where there are unique tracers for all sources contributing to the non-unique tracer except one, and ascribes the residual concentration to that source. This value is then used as the source tracer in the final FA/MR apportionment model for ambient paniculate matter. In addition, factor analyses results are complemented with examination of regression residuals in order to optimize the number of identifiable sources. The new method has been applied to identify and apportion the sources of inhalable particulate matter (IPM; D 5015 μm), Pb and Fe at a site in Newark, NJ. The model indicated that sulfate/secondary aerosol contributed an average of 25.8 μ −3 (48%) to IPM concentrations, followed by soil resuspension (8.2 μ −3 or 15%), paint spraying/paint pigment (6.7/gmm −3or 13%), fuel oil burning/space heating (4.3 μ −3 or 8 %), industrial emissions (3.6 μm −3 or 7 %) and motor vehicle exhaust (2.7 μ −3 or 15 %). Contributions to ambient Pb concentrations were: motor vehicle exhaust (0.16μm −3or 36%), soil resuspension (0.10μm −3 or 24%), fuel oil burning/space heating (0.08μm −3or 18%), industrial emissions (0.07 μ −3 or 17 %), paint spraying/paint pigment (0.036 μm −3or 9 %) and zinc related sources (0.022 μ −3 or 5 %). Contributions to ambient Fe concentrations were: soil resuspension (0.43μ −3or 51%), paint spraying/paint pigment (0.28 μm −3or 33 %) and industrial emissions (0.15 μ −3or 18 %). The models were validated by comparing partial source profiles calculated from modeling results with the corresponding published source emissions composition.