Characterizing isotopic compositions of TC-C, NO3−-N, and NH4+-N in PM2.5 in South Korea: Impact of China's winter heating☆
Graphical abstract
Introduction
Airborne particulate matter (PM) has negative impacts on the human health (WHO, 2013, Pope and Dockery, 2006). Previous epidemiological studies indicated that long-term exposure to pronounced PM is associated with adverse health effects, including increased incidences of premature mortality, hospital admissions, and respiratory and cardiovascular disease (Pope and Dockery, 2006). Particularly fine PM (aerodynamic diameter ≤ 2.5 μm; PM2.5) that can easily penetrate the human bronchi and lungs and are therefore more likely to has adverse effects on cardiopulmonary health (Schwartz et al., 2002, Pope and Dockery, 2006). For this reason, many countries have set strict standards for ambient PM2.5 levels. The Korean government issued national PM2.5 regulations in 2013 that require concentrations not exceeding 25 μg/m3 (yearly) or 50 μg/m3 (for 24 h; Moon et al., 2013). In spite of the political strategies implemented by the government, high PM episodes, in which PM2.5 concentration of 50 μg/m3 or higher lasts over 6 h, have increased in Korea (29 times, 2011; 58 times 2012; 93 times, 2013) (www.airkorea.or.kr, Shin et al., 2016). Since dominant winds near Korea are often westerly, the Korean Peninsula has been influenced by substantial transport of pollutants to the downwind area of China (Kim et al., 2009). The issue of PM2.5 in Korea has been exacerbated by increased SOx and NOx emissions produced by rapid industrial growth in China along with increase of the local sources of air pollution (Heo et al., 2009, Lee et al., 2015). Recently, Zhang et al. (2017) reported that 30,900 deaths in South Korea and Japan (the ‘rest of east Asian’ region) were related to pollution transported from China.
In particular, during haze episodes at Seoul, PM2.5 is mainly composed of ammonium sulfate (33.7%), ammonium nitrate (23.9%), and organic matter (25.6%; Moon et al., 2013). Thus, the emission sources of secondary inorganic aerosols (such as SO42−, NO3−, and NH4+) should be studied to develop effective PM2.5 control strategies (Heo et al., 2009, Lee et al., 2015).
Multi-isotope approaches using stable carbon (δ13C-TC) and nitrogen (δ15N-TN) isotope ratios have been widely used to investigate sources of atmospheric aerosols (Widory et al., 2004, Wang et al., 2010, Kundu et al., 2010, Kunwar et al., 2016). δ13C-TC value has been used to evaluate C source originating from fossil fuel based emission (i.e. coal, diesel, gasoline, and natural gas) and biogenic based emission (i.e. C3 and C4 plants; Kirillova, 2013 and references therein). To date, the application of stable N isotopes in NO3− and NH4+ rather than total nitrogen in atmospheric aerosols has been applied to identify the potential sources of its precursors, NOx and NH3 (for NO3−, Elliott et al., 2009; Proemse et al., 2012, for NH4+, Pan et al., 2016, Proemse et al., 2012). Although isotopic fractionations of δ15N during the gas-particle conversions should be considered, previous studies have suggested that δ15N-NO3−, and δ15N-NH4+ could be used to trace the sources (Elliott et al., 2009; Pan et al., 2016). Global NOx emissions are dominated by fossil fuel combustion from stationary (i.e. coal-fired power plants) and mobile (i.e. vehicles) sources and far exceed natural NOx sources such as lightning, biogenic soil emission and biomass burning. China is the largest NOx emitter, which is known to contribute 18% of global NOx emissions (Liu et al., 2016). In 2010, vehicles and power plants were two of the dominant sources of NOx emissions in China, which contributed to 25% and 28% of the total anthropogenic emissions, respectively (Zhao et al., 2013) whereas, in Korea, vehicle and coal combustion are responsible for 31% and 16% of NOx emission, respectively (airemiss.nier.go.kr). Ammonia (NH3) as the precursor of NH4+, plays major roles in PM2.5 formation since NH3 reacts with nitric acid and sulfuric acid to form particulate NH4+ compounds, and enhances aerosol growth. Although global NH3 emissions are mainly from agricultural activities such as livestock waste and fertilizer, NH3 emissions from vehicles and coal combustion have also recently become a significant source in urban areas (Wu et al., 2016, Chang et al., 2016a, Link et al., 2017).
In this study, we present δ13C-TC, δ15N-TN, δ15N-NO3−, δ18O-NO3−, and δ15N-NH4+ values in PM2.5 collected at Seoul (urban site) and Baengnyeong (rural site) in South Korea from January 2014 to February 2016. Seoul, the capital city of South Korea, is a metropolitan city with typical megacity pollution characteristics with half the Korean population in Seoul Metropolitan Area. Baengnyeong Island, located 210 km from Seoul and 195 km from the Shandong Peninsula of China, is a small island no anthropogenic emission sources. Regular transport of air masses from eastern China, North Korea, and South Korea is expected to provide a high loading of pollutants to the island. Thus, Baengnyeong Island is a pertinent study site for investigating outflow pollution from China to the Korean peninsula (Lee et al., 2015).
The purpose of this study was to investigate the sources of TC, NO3−, and NH4+ in PM2.5 of Seoul and Baengnyeong using stable isotope techniques and to determine the impact of China on air quality in South Korea. To our knowledge, this study is the first attempt that broadly investigates stable isotopic compositions of major components in PM2.5 based on a seasonal perspective in East Asian continental outflow regions.
Section snippets
Ambient PM2.5 sampling at Seoul and Baengnyeong
PM2.5 samples in Seoul were sampled on the roof of the School of Public Health building at Seoul National University (37°58′0″ N, 127°00′1″ E). The building is located in the most congested area in Seoul (Fig. 1). PM2.5 samples from Baengnyeong Island were collected at the Baengnyeong Atmospheric Research Center (37°96′4″ N, 124°63′0″ E). The sampling site is in the northwest corner of the island, approximately 150 m above sea level. There are approximately 4000 permanent residents who mainly
Chemical concentrations in PM2.5
Concentrations of PM2.5 mass, NO3−, SO42−, and NH4+ at Seoul and Baengnyeong are presented in Table A2 and monthly mean values are shown in Fig. 2. The mass concentrations of PM2.5 at Seoul and Baengnyeong were 31 ± 18 μg/m3 and 30 ± 20 μg/m3, respectively. Due to yellow dust storm in spring (www.airkorea.or.kr), higher PM2.5 mass were found in spring (48 ± 26 μg/m3 for Seoul and 35 ± 16 μg/m3 for Baengnyeong) than other seasons at both sites. China's pollutions are often introduced to Seoul
Conclusions
In this study, we present δ13C-TC, δ15N-NO3−, δ18O-NO3−, δ15N-TN, and δ15N-NH4+ values in PM2.5 sampled from East Asian receptor site (Seoul and Baengnyeong Island, in Korea) that are near to and downwind regions of China because cross-border air pollution from China was suspected as a source of the increase in PM2.5 in South Korea. The isotopic results implied that C, NO3−, and NH4+ in PM2.5 from Baengnyeong were nearly originated from coal combustion during winter heating seasons; the island
Acknowledgements
This research was supported by the Ministry of Environment of the Republic of Korea. We acknowledge the Korean Basic Science Institute for the analyses of N-NO3−, O-NO3−, and N-NH4+ isotopes.
References (60)
- et al.
Changes in atmospheric nitrate deposition in Germany –An isotopic perspective
Environ. Pollu.
(2014) - et al.
Isotopic composition of passively collected nitrogen dioxide emissions: vehicle, soil and livestock source signatures
Atmos. Environ.
(2014) - et al.
Isotopic composition of nitrate in sequential Hurricane Irene precipitation samples: implications for changing NOx sources
Atmos. Environ.
(2015) - et al.
Spatial and temporal patterns of nitrogen isotopic composition of ammonia at US ammonia monitoring network sites
Atmos. Environ.
(2017) - et al.
Distant source contributions to PM10 profile evaluated by SOM based cluster analysis of air mass trajectory set
Atmos. Environ.
(2010) - et al.
Chemical characteristics of long-range transport aerosol at background sites in Korea
Atmos. Environ.
(2009) - et al.
Stable carbon and nitrogen isotopic compositions of ambient aerosols collected from Okinawa Island in the western North Pacific Rim, an outflow region of Asian dusts and pollutants
Atmos. Environ.
(2016) - et al.
Characterization of aerosol composition, concentrations, and sources at Baengnyeong Island, Korea using an aerosol mass spectrometer
Atmos. Environ.
(2015) - et al.
Aerosol isotopic ammonium signatures over the remote Atlantic Ocean
Atmos. Environ.
(2016) - et al.
Elevated production of NH4NO3 from the photochemical processing of vehicle exhaust: implications for air quality in the Seoul Metropolitan Region
Atmos. Environ.
(2017)
Analysis of ammonia variation in the urban atmosphere
Atmos. Environ.
Isotopic characterization of nitrate, ammonium and sulfate in stack PM2.5 emissions in the Athabasca Oil Sands Region, Alberta, Canada
Atmos. Environ.
Nitrogen isotopes in the ocean
Ency. Ocean. Sci.
Sources of aerosol nitrate to the Gulf of Aqaba: evidence from_15N and _18O of nitrate and trace metal chemistry
Mar. Chem.
The Origin of atmospheric particles in Paris: a view through carbon and lead isotopes
Atmos. Environ.
PM2.5 pollution is substantially affected by ammonia emissions in China
Environ. Pollut.
Isotopic evidence for a marine ammonium source in rainwater at Bermuda
Glob. Biogeochem. Cy
Estimating the uptake of traffic-derived NO2 from 15N abundance in Norway spruce needles
Oecologia
The importance of vehicle emissions as a source of atmospheric ammonia in the megacity of Shanghai
Atmos. Chem. Phys.
Source apportionment of atmospheric ammonia before, during, and after the 2014 APEC summit in Beijing using stable nitrogen isotope signatures
Atmos. Chem. Phys.
Analysis of nitrogen isotopic composition of ammonium ion using the ammonium diffusion technique
J. Geol. Soc. Korea
A study on chemical characteristics of aerosol composition at west inflow regions in the Korean peninsula II. Characteristics of inorganic aerosol acidity and organic aerosol oxidation
J. Korean Soc. Atmos. Environ.
Chemical and stable carbon isotopic composition of PM2.5 from on-road vehicle emissions in the PRD region and implications for vehicle emission control policy
Atmos. Chem. Phys.
Dual nitrate isotopes in dry deposition: utility for partitioning NOx source contributions to landscape nitrogen deposition
J. Geophys. Res.
Anthropogenic imprints on nitrogen and oxygen isotopic composition of precipitation nitrate in a nitrogen-polluted city in Southern China
Atmos. Chem. Phys.
Nitrogen isotopic composition of coal-fired power plant NOx: influence of emission controls and implications for global emission inventories
Environ. Sci. Technol.
Characterizing the isotopic composition of atmospheric ammonia emission sources using passive samplers and a combined oxidation-bacterial denitrifier approach
Rapid Commun. Mass Spectrom.
On the interaction of isotopic exchange processes with photochemical reactions in atmospheric oxides of nitrogen
Geophys. Res. Atmos.
Nitrogen isotopic ratios of gaseous ammonia and ammonium aerosols in the atmosphere
J. Jpn. Soc. Atmos. Environ.
Potential canopy influences on the isotopic composition of nitrogen and sulphur in atmospheric deposition
Oecologia
Cited by (61)
Nitrogen isotopic characteristics of aerosol ammonium in a Chinese megacity indicate the reduction from vehicle emissions during the lockdown period
2024, Science of the Total EnvironmentIsotopic comparison of ammonium between two summertime field campaigns in 2013 and 2021 at a background site of North China
2023, Science of the Total Environment
- ☆
This paper has been recommended for acceptance by Eddy Y. Zeng.