Platinum group elements in atmospheric PM particles and dry deposition in France.

Platinum group elements (PGEs, i.e. platinum, Pt; palladium, Pd; and rhodium, Rh) catalyse over 90% of carbon monoxide, nitrogen oxides and hydrocarbons from combustion residues into water vapour, carbon dioxide and nitrogen in the vehicle's catalytic converter. But there is a major concern over these metals in the scientific world, since they are emitted by catalytic converters and accumulating in the environment. The distribution of PGEs in PM fraction was studied in an open urban site (Nantes, France) and in a tunnel (Paris, France) using low- and high-volume air samplers. PGEs were also investigated in dry deposition particles and deposited dust sampled in the tunnel. Pd occurred at the highest levels in both PM and dry deposition samples, followed by Rh and Pt. Maximum concentrations in PM fraction were 114 pg m for Pd, 14.3 pg m for Rh and 3.3 pg m for Pt in the urban site (Nantes) and 91 pg m for Pd and 16 pg m for Rh in the tunnel (Paris). The concentrations for dry depositions in the tunnel were 261 μg kg for Pt, 431 μg kg for Pd and 85 μg kg for Rh. The results on PGEs levels in atmospheric particles and dry depositions are the first data of their kind in France and will provide new insights into the contribution of catalytic converters to the environment. We also observed Pd and Rh being 2 times higher PM particles compared to dry depositions, leading us to suggest that particles rich in Pd and Rh are smaller than 10 μm. An overall concentration trend of Pd > Rh > Pt was observed in all samples, showing the replacement of Pt by Pd and Rh in newer catalytic converters.