Effects of Meteorological Conditions on PM2.5 Concentrations in Nagasaki, Japan.

The fine particulate matter (PM2.5) problem has attracted much scientific and public attention, due to its effects on visibility, human health, and global climate. There are three factors that have important effect on PM2.5 mass concentration: domestic pollutant emission sources, external sources outside of the country, and the meteorological conditions. Nagasaki is a coastal prefecture located at the westernmost part of Japan, which is an ideal location to study pollutants from long range transport and correlation between PM2.5 and meteorological conditions. In this paper, PM2.5 concentration data and meteorological data were obtained during 1 January 2013~31 December 2013. The spatial distribution depicts that the western part of the study area has the most serious PM2.5 pollution. The correlation analysis results between PM2.5 concentration and meteorological data showed that temperature had a negative, and precipitation had a positive, correlation with PM2.5. There was a threshold in the correlations between humidity and wind speed and PM2.5. The correlation was positive or negative depending on the meteorological variable values, if these were lower or higher than the threshold. From the relationship with wind direction, it can be depicted that the west wind might bring the most pollutants to Nagasaki.