1Inst. of Environmental Assessment & Water Research (IDǼA-CSIC), Jordi Girona 18, 08034 Barcelona, Spain
2Dept. of Earth & Environmental Sciences, Kumamoto University, Kurokami, Kumamoto 860-8555, Japan
3TNO Climate, Air and Sustainability, Princetonlaan 6, P.O. Box 80015, 3508 TA Utrecht, The Netherlands
4Dept. of Physics and Astronomy, University of Florence, and INFN, Sesto Fiorentino, Florence 50019, Italy
5Center for Research in Sustainable Chemistry (CIQSO), University of Huelva, Campus de El Carmen, s/n, 21071 Huelva, Spain
6AP 23075, Barcelona 08080, Spain
Abstract. The regular eastward drift of transboundary aerosol intrusions from the Asian mainland into the NW Pacific region has a pervasive impact on air quality in Japan, especially during springtime. Analysis of 24-h filter samples with Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) and Mass Spectrometry (ICP-MS), and hourly Streaker with Particle Induced X-ray Emission (PIXE) samples collected continuously for six weeks reveal the chemistry of successive waves of natural mineral desert dust ("Kosa") and metalliferous sulphatic pollutants arriving in western Japan during spring 2011. The main aerosol sources recognised by Positive Matrix Factorization (PMF) analysis of Streaker data are mineral dust and fresh sea salt (both mostly in the coarser fraction PM2.5–10), As-bearing sulphatic aerosol (PM0.1–2.5), metalliferous sodic particulate matter (PM) interpreted as aged, industrially contaminated marine aerosol, and ZnCu-bearing aerosols. Whereas mineral dust arrivals are typically highly transient, peaking over a few hours, sulphatic intrusions build up and decline more slowly, and are accompanied by notable rises in ambient concentrations of metallic trace elements such as Pb, As, Zn, Sn and Cd. The magnitude of the loss in regional air quality due to the spread and persistence of pollution from mainland Asia is especially clear when cleansing oceanic air advects westward across Japan, removing the continental influence and reducing concentrations of the undesirable metalliferous pollutants by over 90%. Our new chemical database, especially the Streaker data, demonstrates the rapidly changing complexity of ambient air inhaled during these transboundary events, and implicates Chinese coal combustion as the main source of the anthropogenic aerosol component.