Seasonal Patterns, and Ambient PM0.1 Emission Sources in the Hokuriku Region in Japan

Size fractionated airborne particulates including PM0.1 were simultaneously monitored at three different sites in the Hokuriku region of Japan. These were Kanazawa, Suzu and Toyama. Research was conducted over a three-year period between 2014 and 2016 in order to collect information concerning the PM status and related seasonal patterns. Possible local emission sources of PM0.1 and the influence of long-range transportation are discussed in relation to mass concentration and diagnostic parameters defined by particle-bound carbonaceous components such as organic and elemental carbon, and their ratios. The influence of trans-boundary air mass transport from outside Japan is also discussed based on PM0.1 characteristics and air mass trajectory analyses. The seasonal behavior for PM concentrations were similar between sites reflecting similar meteorological characteristics. Due to larger numbers of emission sources, the PM at the Toyama site was the largest between the three sites while at the Kanazawa site, precipitation in the spring and the summer was higher than in the autumn and winter seasons and this may have resulted in a decrease in PM levels. The concentration and influence of secondary organic carbon on the PM0.1 carbon content were largest at the Toyama site. The Py-OC/O4 ratio was consistent with increases in the number of hotspots in the spring and autumn. Carbonaceous components in the PM0.1 fraction could be largely explained by local emission sources. However, explaining the influence of the trans-boundary transportation of air pollutants only by the behavior of carbonaceous components in PM0.1 may not be sufficient, and a more detailed discussion of various chemicals in different sizes of particles is needed.