Spatiotemporal distribution, trend, forecast, and influencing factors of transboundary and local air pollutants in Nagasaki Prefecture, Japan

Abstract

The study of PM2.5 and NO2 has been emphasized in recent years due to their adverse effects on public health. To better understand these pollutants, many studies have researched the spatiotemporal distribution, trend, forecast, or influencing factors of these pollutants. However, rarely studies have combined these to generate a more holistic understanding that can be used to assess air pollution and implement more effective strategies. In this study, we analyze the spatiotemporal distribution, trend, forecast, and factors influencing PM2.5 and NO2 in Nagasaki Prefecture by using ordinary kriging, pearson's correlation, random forest, mann–kendall, auto-regressive integrated moving average and error trend and seasonal models. The results indicated that PM2.5, due to its long-range transport properties, has a more substantial spatiotemporal variation and affects larger areas in comparison to NO2, which is a local pollutant. Despite tri-national efforts, local regulations and legislation have been effective in reducing NO2 concentration but less effective in reducing PM2.5. This multi-method approach provides a holistic understanding of PM2.5 and NO2 pollution in Nagasaki prefecture, which can aid in implementing more effective pollution management strategies. It can also be implemented in other regions where studies have only focused on one of the aspects of air pollution and where a holistic understanding of air pollution is lacking.

Temporal coherence in particulate matters in East Asian outflow regions: fingerprints of ENSO, Asian dust and COVID-19

“…While Sokhi et al [31] comprehensively analyzed the global data and reported a decrease of approximately 30% to 40% in mean PM2.5 concentrations during the 2020 full lockdown compared to the same period in 2015-2019, several studies conducted in East Asia showed more complex PM2.5 signals [27,28,29,30,32,52,53]. Literature also reports reductions in PM2.5 levels over outflow regions during the COVID-19 period [9,24,28,29,31,32]. Some studies have observed a rebound in PM2.5 levels in South Korea and the Pearl River Delta following the easing of COVID-19 restrictions [28,32], while other has reported continued reductions in PM2.5 levels in Japan in 2021 [9].…”

“…Transboundary air pollution resulting from winter monsoon-driven continental outflows has 35 raised significant environmental concerns in downwind areas such as South Korea [4,5,6,7], Japan [3,7,8,9,10,11], Taiwan [12,13,14,15,16], and Hong Kong [14,17,18,19]. In eastern China, satellite-based estimates of PM2.5 show consistent long-term trends with some variations in interannual patterns among subregions (Fig.…”

“…The spatiotemporal variability of PM is shaped by multiple factors, including emission sources, meteorological conditions, atmospheric chemistry, and transport processes. Effective measures aimed at improving air quality can be achieved through emission control policies, and collaborative cross-national efforts are crucial to mitigate air pollution issues across East Asia [9,22]. In recent decades, Japan, South Korea, and Taiwan have experienced a long-term decrease in ambient PM levels, which can be primarily attributed to a significant reduction in domestic anthropogenic emissions; however, transboundary pollutants still play a significant role in the PM concentrations [9,22,23,24,25,26].…”

“…In recent decades, Japan, South Korea, and Taiwan have experienced a long-term decrease in ambient PM levels, which can be primarily attributed to a significant reduction in domestic anthropogenic emissions; however, transboundary pollutants still play a significant role in the PM concentrations [9,22,23,24,25,26]. The contribution of meteorological conditions, particularly the weakening of regional wind speeds leading to atmospheric stagnation, can also offset the declining trends in response to the reduction in domestic emissions [9,23,25,26]. In addition to the air quality improvement policies implemented by these nations, unplanned interventions such as the COVID-19 pandemic-related restrictions have also left an impact on the temporal variations of PM concentrations across the regions.…”

“…In addition to the air quality improvement policies implemented by these nations, unplanned interventions such as the COVID-19 pandemic-related restrictions have also left an impact on the temporal variations of PM concentrations across the regions. These restrictions resulted in the shutdown or standstill of socioeconomic activities, leading to temporary reductions in ambient PM levels [9,24,27,28,29,30,31,32].…”