Sources and fluxes of Pt, Ir and REE in the Seoul metropolitan area through wet scavenging processes

Platinum group elements (PGEs: Pt and Ir) and rare earth elements (REEs) were analyzed in rainwater samples collected in Seoul during the summer of 2008 to identify their sources and quantify their wet-deposition fluxes to the Earth’s surface environment. Major (Na, K, Mg, Ca, NH4+, SO42−, NO3−, Cl− and F−) and minor (Fe, Ba, Y and Hf) elements were also measured to facilitate interpretation. Evaluation of elemental correlations, crustal enrichment factors, Ir/Pt ratios and REE patterns indicated meteoric/volcanic sources for Pt and Ir and additional anthropogenic sources for Pt. REEs were predominantly of crustal origin. The relationship between concentrations and rainfall indicated that below-cloud scavenging (wash-out) was the main scavenging mechanism for most elements. The wet-deposition fluxes in Seoul were higher than those recorded in polar ice cores for Pt and Ir and were comparable to those from other rainwater studies of REEs in East Asia.