Source profiles by unique ratios (SPUR) analysis: Determination of source profiles from receptor-site streaker samples

A streaker total filter particulate sampler was operated for three weeks at an urban site in Milan, Italy. The filters were analysed by Particle Induced X-ray Emission (PIXE), yielding hourly concentrations of 15 elements. The data are used to extract source elemental profiles using a new method, SPUR (Source Profiles by Unique Ratios). The SPUR technique is a combination of event identification using unique elemental ratios in sources, and correction for background events by identifying events of differing time constants in the time domain. The elemental ratios are identified in plots of log([S]/[T])vs[T], referred to as SPUR plots, where T is a (non-unique) tracer and [S] is an element establishing the unique ratio. Using the SPUR technique, eight distinct sources are identified and profiles established. The sources are: two metallurgical smelters, two crustal sources, a potassium-rich source, automotive, regional crustal and regional sulphur. Results are compared with source profiles derived from Absolute Principal Component Scores analysis. SPUR analysis demonstrates powerful capability for deriving source profiles from receptor samples, including having the capability of distinguishing between sources of similar composition without using a unique tracer element. © 1991.