Impact of long-range transport of aerosols on the PM2.5 composition at a major metropolitan area in the northern Kyushu area of Japan

https://doi.org/10.1016/j.atmosenv.2014年01月02日9 Get rights and content

Highlights

  • •
    Nss.SO42− were in the same level at a metropolis and an island located 190 km upwind.
  • •
    Cd/Pb and Pb/Zn ratios at Fukuoka coincide with those measured at Beijing, China.
  • •
    Nss.SO42− data at Fukuoka reflect the reported decadal SO2 emission change in China.
  • •
    Long-range transport dominates PM2.5 in Fukuoka throughout the year except in summer.

Abstract

In view of the recent rapid economic growth and accompanying energy consumption in the East Asian region, particularly in China, there is much concern about the effects of emitted particulate pollutants on human health. We have thus investigated the impact of long-range transport of aerosols on urban air quality in the upwind areas of Japan by comparing the PM2.5 composition collected for multiple years in Fukuoka, a representative metropolis in the Kyushu area, and in Fukue Island, located 190 km southwest of Fukuoka. Daily averaged PM2.5 concentrations in Fukuoka and Fukue were almost identical. PM2.5 concentrations at these sites were dominated by sulfate and particulate organics, and their fluctuation patterns were similar except for organics in the warm season. In contrast, those of nitrate and elemental carbon differed substantially between the sites. In addition, the ratios of Pb/Zn and Cd/Pb in Fukuoka were close to the reported values in Beijing. Non-sea-salt sulfate concentration in Fukuoka measured in this study and reported in the past measurements apparently coincided with the decadal SO2 emission change in China reported in a recent emission inventory. Therefore, we conclude that even in a city as large as Fukuoka, the PM2.5 concentration in the northern part of the Kyushu area is primarily dominated by the inflow of long-range transported aerosols throughout the year, except in the summer, rather than local air pollution emitted at each site.

Introduction

In the middle of January 2013, an extremely high concentration of PM2.5 exceeding 800 μg m−3 (hourly data) was observed at the U.S. Embassy in Beijing, China. This raised concerns about the acute health effects of air pollution on the local residents. Severe air pollution in mega cities of China (e.g., Chan and Yao, 2008) has become a sociopolitical issue, and such pollution has been studied to determine its adverse health effects (e.g., Li et al., 2013, Shang et al., 2013). In addition, increasing emissions of aerosols and the precursors of photochemical O3 from the East Asian region have become a focus of research in view of short-lived climate forcers.
Long-range transport of aerosols, presumably from mainland China, has been studied in various locations in neighboring countries in East Asia. For example, long-term monitoring studies on islands such as Oki Island, Japan (Mukai et al., 1990), and Jeju Island, Korea (e.g., Chen et al., 1997, Park et al., 2004), have characterized the aerosols transported from the Asian continent. Samplings of lake sediment core have revealed the historical record of transported metallic elements that are potentially hazardous to human health or may affect aquatic environments (Kusunoki et al., 2012). At Cape Hedo of Okinawa Island, Japan, the detailed size distribution of major aerosol components and the highly time-resolved characteristics of transported aerosols were analyzed using an aerosol mass spectrometer (Takami et al., 2007). These studies have focused mainly on the nature of long-range transport phenomena, or the chemical/microphysical aging procedure of transported pollutants.
However, the effect of long-range transported pollutants on air pollution status or the achievement of the National Ambient Air Quality Standard (NAAQS) in each country has rarely been analyzed except for the trans-Pacific transport of ozone on the air quality of the U.S. west coast (e.g., Cooper et al., 2011, Huang et al., 2010, Parrish et al., 2010). In the countries of East Asia where the continental outflow of air pollutants is observed, the current interest revolves around the question of whether the long-range transport of aerosols is merely an episodic event or a constant supplier of pollutants that substantially affects the achievement of the NAAQS.
To address this problem, we have analyzed the impact of long-range transported aerosols on the PM2.5 concentration in Fukuoka, a representative metropolis in the northern Kyushu area, Japan. The prevailing westerlies first hit the Japanese main islands at Fukuoka, and this region is less influenced by emissions from other parts of Japan. Therefore, the location is preferable for detecting the constant effect of long-range transported aerosols on the state of air quality in an urban area. Major aerosol components in PM2.5 collected in Fukuoka are compared with those collected 190 km upwind of the westerlies at Fukue Island. We further infer the potential emission source area of PM2.5 in Fukuoka by the ratio of metallic elements as an emission source fingerprint.
Another current issue regarding pollutant emission in the East Asian region is the decadal emission change in China. The emission of air pollutants in the East Asian region increased during the 1990s and the early 2000s (e.g., Ohara et al., 2007). However, a recent emission inventory study pointed out that SO2 emission in China peaked in 2006 and started to decrease gradually after that (Lu et al., 2010). Some remote sensing data have confirmed the recent decreasing trend of SO2 (Li et al., 2010) and aerosol optical depth (Itahashi et al., 2012). If this is the case, the in situ aerosol data measured at the lee side of mainland China may have reflected the suggested change in SO2 emission. To acquire insight into this, we compared the present data to those obtained in the 1990s and the 2000s.

Section snippets

Sampling locations and measurements

The locations of Fukue Island and Fukuoka are indicated in Fig. 1. Fukuoka is the largest center of commerce in the Kyushu region of Japan, with a population of 2,400,000 in the greater Fukuoka metropolitan area. Nagasaki is a middle-sized city with a population of 300,000; shipbuilding is the major industry. Fukue Island, with an area of 326 km2 and a population of 37,000, is located 190 km southwest of Fukuoka; the major industries are agriculture and fishery, and the anthropogenic emissions

PM2.5 mass concentrations in Fukue Island, Fukuoka, and Nagasaki

The time series of the daily averaged mass concentration of PM2.5 in Fukue Island, Fukuoka, and Nagasaki measured by TEOM are shown in Fig. 2 for the period from March 2010 to August 2011. The concentrations and the fluctuation patterns in these sites were close to each other throughout the year, although the concentrations in Fukuoka were slightly higher than those in Fukue Island and Nagasaki in the warm season (i.e., from May to September). In some high concentration events, PM2.5

Conclusions

The parallel sampling of PM2.5 aerosol in Fukuoka and Fukue Islands revealed that nss.SO42−, which is the largest contributor of PM2.5 in Fukuoka, is dominated by the inflow of long-range transport but not by local emissions. TOT-OC, the second contributor of PM2.5 mass, is also controlled by the inflow of pollutants, although it is partly affected by local air pollution in Fukuoka during the warm season.
The ratios of Cd/Pb and Pb/Zn in PM2.5 in Fukuoka were compared with those measured in

Acknowledgments

The authors appreciate the support of Dr. S. Hasegawa and Dr. S. Yonemochi (Center for Environmental Science in Saitama) in the weighing of aerosol filters. This research was supported by a Grant-in-Aid for Scientific Research on Innovative Areas "Impacts of Aerosols in East Asia on Plants and Human Health" (Grant No. 20120007) funded by the Ministry of Education, Culture, Sport Science and Technology (MEXT), Japan.

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