title: Heterogeneity of platinum group metals in airborne particles.
abstract: The emission of three of the platinum group metals (PGMs), Pd, Pt, and Rh, from automobile catalysts and into the urban environment is a potential concern for human health. The analysis of low concentrations of PGMs in air particles is an analytical challenge, and it is demonstrated that interferences in inductively coupled plasma-mass spectrometry (ICP-MS) can be corrected mathematically for Pt and Rh and, at higher concentrations, for Pd. The PM10 concentrations of PGMs in urban air collected in Göteborg are 0.1-10 pg m-3 (Pd), 0.9-19 pg m-3 (Pt), and 0.3-4 pg m-3 (Rh), with higher values for greater traffic intensity. These concentrations provide a general background for the urban atmospheric environment, and the Pt:Rh ratio (4.2:1) agrees with known automobile catalyst composition. The analysis of filters from 10 parallel samplers indicated the significant heterogeneity of PGMs in samples of urban air particles. Scanning laser ablation ICP-MS provided the micron spatial resolution required to identify individual particles. Ablation across the filter surface demonstrated the presence of relatively few particles with a high concentration of PGMs. These occasional high concentration particles, which might be overlooked in conventional air sampling with total analysis, have a high Pt:Rh ratio (12.3:1), which can be attributed to catalyst aging during vehicle operation.
authors.affiliation: Water Environment Transport, Chalmers University of Technology, SE-412 96 Göteborg, Sweden. sebastien.rauch@wet.chalmers.se
authors.forename: S
authors.initials: S
authors.lastname: Rauch
authors.forename: M
authors.initials: M
authors.lastname: Lu
authors.forename: G M
authors.initials: GM
authors.lastname: Morrison
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D007854:Lead / Q000032:analysis*; D013058:Mass Spectrometry; D010316:Particle Size; D010984:Platinum / Q000032:analysis*; D012238:Rhodium / Q000032:analysis*; D014505:Urban Population; D001335:Vehicle Emissions
chemical_list: D000393:Air Pollutants; D001335:Vehicle Emissions; D007854:Lead; D010984:Platinum; D012238:Rhodium