Trends in PM_2.5 Concentration in Nagoya, Japan, from 2003 to 2018 and Impacts of PM_2.5 Countermeasures

• Main Authors: Makiko Yamagami, Fumikazu Ikemori, Hironori Nakashima, Kunihiro Hisatsune, Kayo Ueda, Shinji Wakamatsu, Kazuo Osada
• Format: Article
• Language: English
• Published: MDPI AG 2021-05-01
• Series: Atmosphere
• Subjects: PM_2.5; elemental carbon; organic carbon; urban air pollution; long-term trend; pollution countermeasure
• Online Access: https://www.mdpi.com/2073-4433/12/5/590

In Japan, various countermeasures have been undertaken to reduce the atmospheric concentration of fine particulate matter (PM_2.5). We evaluated the extent to which these countermeasures were effective in reducing PM_2.5 concentrations by analyzing the long-term concentration trends of the major components of PM_2.5 and their emissions in Nagoya City. PM_2.5 concentrations decreased by 53% over the 16-year period from fiscal years 2003 to 2018 in Nagoya City. Elemental carbon (EC) was the component of PM_2.5 with the greatest decrease in concentration over the 16 years, decreasing by 4.3 μg/m³, followed by SO₄²⁻ (3.0 μg/m³), organic carbon (OC) (2.0 μg/m³), NH₄⁺ (1.6 μg/m³), and NO₃⁻ (1.3 μg/m³). The decrease in EC concentration was found to be caused largely by the effect of diesel emission control. OC concentrations decreased because of the effects of volatile organic compound (VOC) emission regulations for stationary sources and reductions in VOCs emitted by vehicles and construction machinery. NO₃⁻ concentrations decreased alongside decreased contributions from vehicles, construction machinery, and stationary sources, in descending order of the magnitude of decrease. Although these findings identify some source control measures that have been effective in reducing PM_2.5, they also reveal the ineffectiveness of some recent countermeasures for various components, such as those targeting OC concentrations.