Is PM_2.5 Trans-boundary Environmental Problem in Japan dramatically improving?

Abstract

The PM_2.5 concentration decreases between 2013 and 2016 over Japan were analyzed by observation and a chemical transport model. During this period, the annual mean PM_2.5 decreased in Japan and the number of PM_2.5 sub-standard days underwent a dramatic reduction. Our analysis confirmed that the PM_2.5 in northern China, SO₂ and NO₂ vertical column density over Central East China by satellite showed about a 10%/y reduction and this happened due to the anthropogenic emission reductions (almost 10%/y reduction). A Source-receptor analysis by a chemical transport model showed that a 20% reduction of the Chinese PM_2.5 concentration will decrease the annual mean PM_2.5 in Fukuoka by 12%. Our analysis indicated that if the current emission reduction rate continues over China, the high concentration of transboundary PM_2.5 problem in Japan will very quickly improve.