Time-resolved characterization of organic compounds in PM2.5 collected at Oki Island, Japan, affected by transboundary pollution of biomass and non-biomass burning from Northeast China
Graphical abstract
Introduction
Organic components such as organic carbon (OC), water-soluble OC (WSOC), and elemental carbon could contribute from 10% to 70% of the total mass of fine particulate matter (PM) (PM with a diameter smaller than 2.5 μm: PM2.5), which affect air quality, human health, and climate (Pöschl, 2005; IPCC, 2013). Organic compounds possess light absorptivity, toxicity, and hygroscopicity; these strongly affect the chemical and physical properties of PM. Therefore, many studies have been conducted to understand the characterization of organic aerosols (Nozière et al., 2015). Organic aerosols are generally divided into a primary organic aerosol (POA) directly emitted from sources such as biomass and fossil fuel combustions, plant and soil dust, and secondary organic aerosol (SOA) formed by the oxidation of gas-phase precursors in the atmosphere (Hallquist et al., 2009). Because of its complex sources and atmospheric processing, the identification of organic aerosol sources and generation mechanisms are challenging topics.
East and Northeast Asia have severe air pollution because of its rapid industrialization and urbanization. Moreover, biomass burning such as agricultural residue combustion and forest fires from their regions caused severe haze in not only on local and regional scales but also transnational scale. Specifically, aerosols transported from mainland China significantly affect neighboring countries; therefore, several studies have been conducted in various locations at the downwind regions such as Japan and Korea. Kaneyasu et al. (2014) conducted year-round observations of OC concentrations in PM2.5 in Fukue Island and Fukuoka city, which are western remote and urban sites in Japan. They reported that transboundary pollution strongly affected OC even in Fukuoka during the period, except for the warm season. Yoshino et al. (2016) conducted aerosol mass spectrometry observations and revealed that sulfate ions and low volatile organic aerosols were the dominant components during the winter and spring seasons when transboundary pollution was predominant at Fukue Island. In Fukuoka, sulfate and low volatile organic aerosols were dominant at high PM2.5 concentrations. Furthermore, the impact of Siberian forest fires was reported as another important transboundary pollution (Ikemori et al., 2015; Kaneyasu et al., 2007). These reports demonstrate that carbonaceous aerosols such as OC and black carbon, originating from large-scale forest fires in Siberia in 2003, were transported to Japan over long distances. Moreover, Uranishi et al. (2020) reported that PM2.5 emitted from field biomass burning in Northeast China were transported to the Hokkaido and Tohoku regions in Japan and caused high PM2.5 pollution in the early spring of 2019. Other reports reveal that diacids, their intermediates, and biomass burning tracers in the mainland of Japan and in Chichijima, which is located in the western North Pacific, 2000 km east of the Asian continent, are associated with the long-range atmospheric transport of pollutants from East Asia (Gowda and Kawamura, 2018; Verma et al., 2015). The results of these studies indicate that the transboundary pollution from East and Northeast Asia affects islands in the Pacific Ocean, as well as the neighboring countries downwind of East and Northeast Asia. However, details about the sources, contributions, and effects of organic aerosols transported from East and Northeast Asia are still unclear.
To evaluate the source and process of organic aerosols, specific chemical organic compounds were proposed as tracers. For example, anhydrous sugar such as levoglucosan and hydroxy, and methoxy phenol (4-hydroxybenzoic acid) were used as a tracer for biomass burning (Bhattarai et al., 2019; Simoneit et al., 1999; Wan et al., 2019). Dicarboxylic acids, such as oxalic acid and malic acid, were used as tracers for SOAs and their process (Kawamura and Bikkina, 2016). Terephthalic acid is a major pyrolysis product from plastic products such as polyethylene terephthalate (Simoneit et al., 2005). Moreover, laboratory studies proposed several tracers of biogenic SOA and anthropogenic SOA (ASOA). Pinic acid, 3-hydroxyglutaric acid, and 3-methylbutane-1,2,3-tricarboxylic acid were reported oxidation products from pinene (Claeys et al., 2007; Jaoui and Kamens, 2001; Szmigielski et al., 2007). 2,3-Dihydroxy-4-oxopentanoic acid, phthalic acid, 4-methylphthalic acid, and some nitroaromatics were also proposed as oxidation products from anthropogenic volatile organic compounds (VOCs) such as toluene and naphthalene (Al-Naiema and Stone, 2017; Ikemori et al., 2019). Although various organic tracers were suggested, the few studies that used them were conducted in the downwind area of East and Northeast Asia. Kundu et al. (2016) examined the trend in major surrogate compounds (C2–C10 diacids) of SOA in atmospheric aerosols of the Gosan site on Cheju Island, South Korea, that were influenced by pollution outflows from Eastern Asia during 2001 to 2008. They demonstrated that sulfate, nitrate, and ammonium decreased in Eastern Asia, whereas diacids decreased insignificantly and concluded that the pollution control strategies in Eastern Asia could not decrease organic acidic species. This report illustrates the importance of evaluating the impact of organic aerosols and their precursors released in the Asian continent, not limited to dicarboxylic acids, on the surrounding areas. Furthermore, it is also critical to determine the source and its emitting regions of transported organic aerosols.
Japan is located downwind of East and Northeast Asia and strongly affected by transboundary pollution (Ikemori et al., 2016; Itahashi et al., 2017; Kaneyasu et al., 2014; Tang et al., 2015; Uranishi et al., 2019). The Ministry of the Environment (MOE) in Japan hourly measured PM2.5 mass and chemical components such as sulfate and nitrate at 10 sites in Japan since April 2017. They used a continuous dichotomous aerosol chemical speciation analyzer (ACSA) to strengthen the PM2.5 monitoring system and monitor transboundary pollution from East and Northeast Asia. This monitoring revealed that the annual average values of WSOC among remote sites indicated high values at the Oki and Goto, which are western monitoring sites in Japan, and decreased from the western to eastern monitoring sites in Japan (MOE, 2019a). The results indicate that transboundary WSOC from East and Northeast Asia significantly influenced air quality downwind of East and Northeast Asia. However, the source and major factor causing high values of WSOC are still unclear. In this study, we measured the organic compounds using the tape filter of a PM2.5 mass analyzer in Oki Island in March 2019 to evaluate the source and emitting regions of WSOC. We focus organic tracers during the period of high values of both PM2.5 and WSOC and discuss the factors of high-WSOC values and the sources and process of transported pollution of organic aerosols.
Section snippets
Site description and sample collection
The Oki Islands are approximately 90 km north of the Japan mainland, 350 km east of the Korean Peninsula, and 1000 km southeast of Northeast China (Shenyang) (Fig. S1). Oki has a population of about 20,000. It is an ideal remote location for investigating transboundary pollution from East and Northeast Asia because of its geographical environment and limited local anthropogenic emissions (Mukai et al., 1990; Mukai and Yokouchi, 1995; Fujihara et al., 2003). Hourly PM2.5 was collected in a spot
PM2.5 mass and major component concentrations in march 2019
Fig. 1 (a) and (b), respectively, show temporal variations of mass concentrations of PM2.5, WSOC, sulfate, and nitrate by ACSA and fractions of those components in PM2.5 at Oki during PM2.5 collecting periods from March 7, 2019, at 11:00 to April 8, 2019, at 10:00. PM2.5 concentration showed high values, such as hourly values exceeding 35 μg/m3, which is an environmental standard for daily averaged concentration in Japan, on March 12, 22, and 26–27, 2019. On those days, sulfate and/or nitrate
Conclusion
This study conducted high time-resolved measurements of organic tracer compounds in PM2.5 in March 2019 on Oki Island, where the local emissions are small to evaluate organic aerosols of the transboundary pollution from Northeast Asia. WSOC concentrations and WSOC fraction in PM2.5 also showed high values on March 22–23 (HWSOC), suggesting the influence of WSOC on the high PM2.5 concentration. The air mass during this term passed through Northeast China where many fire spots were detected. In
CRediT authorship contribution statement
Fumikazu Ikemori: Conceptualization, Writing - original draft, Investigation, Funding acquisition. Katsushige Uranishi: Visualization, Writing - review & editing. Takahiro Sato: Investigation. Makoto Fujihara: Investigation. Hitomi Hasegawa: Resources. Seiji Sugata: Writing - review & editing, Supervision, Funding acquisition.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgments
This research was conducted as Type II joint research between the National Institute for Environmental Studies and the local environmental research institutes in Japan. The study was supported by the Grant from the Steel Foundation for Environmental Protection Technology. We acknowledge the use of data and imagery from LANCE FIRMS operated by the NASA/GSFC/Earth Science Data and Information System with funding provided by NASA/HQ.
References (75)
- et al.
Secondary organic aerosols from aromatic hydrocarbons and their contribution to fine particulate matter in Atlanta, Georgia
Atmos. Environ.
(2020) - et al.
Arabitol and mannitol as tracers for the quantification of airborne fungal spores
Atmos. Environ.
(2008) - et al.
Chemical characteristics of dicarboxylic acids and related organic compounds in PM2.5 during biomass-burning and non-biomass-burning seasons at a rural site of Northeast China
Environ. Pollut.
(2017) - et al.
Carbohydrate sources in a coastal marine environment
Geochim. Cosmochim. Acta
(1984) - et al.
High molecular weight organic compounds (HMW-OCs) in severe winter haze: direct observation and insights on the formation mechanism
Environ. Pollut.
(2016) - et al.
Formation of 2-methyl tetrols and 2-methylglyceric acid in secondary organic aerosol from laboratory irradiated isoprene/NOx/SO2/air mixtures and their detection in ambient PM2.5 samples collected in the eastern United States
Atmos. Environ.
(2005) - et al.
Determination of levoglucosan in biomass combustion aerosol by high-performance anionexchange chromatography with pulsed amperometric detection
Atmos. Environ.
(2006) - et al.
Levoglucosan and other cellulose and lignin markers in emissions from burning of Miocene lignites
Atmos. Environ.
(2009) - et al.
Annual and seasonal variations in oxidant concentration in Matsue, Japan
Atmos. Environ.
(2003) - et al.
Seasonal variations of low molecular weight hydroxy-dicarboxylic acids and oxaloacetic acid in remote marine aerosols from Chichijima Island in the western North Pacific (December 2010–November 2011)
Atmos. Res.
(2018)