Characterization of submicron aerosols at a suburban site in central China

doi:10.1016/j.atmosenv.2016.01.054

Atmospheric Environment

Volume 131, April 2016, Pages 115-123

https://doi.org/10.1016/j.atmosenv.2016.01.054 Get rights and content

Highlights

•
Submicron aerosol (PM₁) at a suburban site in central China was characterized.
•
Organics and sulfate dominated PM₁ composition in central China.
•
Aerosol composition was relatively similar from different sources areas near the suburban site.

Abstract

We have characterized the chemical composition and sources of submicron aerosol (PM₁) at a suburban site in Xinzhou in central China using an Aerosol Chemical Speciation Monitor from July 17 to September 5, 2014. The average (±1σ) PM₁ concentration was 35.4 (±20.8) μg/m³ for the entire study period, indicating that Xinzhou was less polluted compared to the megacities in the North China Plain (NCP). The PM₁ was mainly composed of organic aerosol and sulfate, on average accounting for 33.1% and 32.4%, respectively, followed by nitrate (14.4%) and ammonium (11.8%). Higher sulfate and lower nitrate contributions than those in megacities in the NCP elucidated an important emission source of coal combustion in central China. Three organic aerosol (OA) factors, i.e., hydrocarbon-like OA (HOA), semi-volatile oxygenated OA (SV-OOA) and low-volatility OOA (LV-OOA), were identified using positive matrix factorization. Secondary OA (=SV-OOA + LV-OOA) dominated OA, on average accounting for 82%, indicating that OA at the Xinzhou site was overall oxidized. We also observed relatively similar aerosol bulk composition and OA composition at low and high mass loading periods, and also from the different source areas, indicating that aerosol species were homogeneously distributed over a regional scale near the site for most of the time during this study. Slightly higher mass concentrations and sulfate contributions from the southern air masses were likely due to the transport from the polluted cities, such as Taiyuan to the south. In addition, the daily variation of PM₁ in Xinzhou resembled that observed in Beijing, indicating that the wide-scale regional haze pollution often influences both the NCP and the central China.

Introduction

Atmospheric pollution caused by high concentrations of aerosol particles is a major environmental problem in China (Chan and Yao, 2008, Yuan et al., 2015, Zhang et al., 2012). In addition to the direct and indirect climate effects by scattering and absorbing sunlight or serving as cloud condensation nuclei (CCN) (Stocker et al., 2013), aerosol also causes potential health risks and visibility problems (Chen et al., 2013).

In recent years, air pollution studies were extensively carried out in megacities in east China, such as Beijing (Guo et al., 2014, Sun et al., 2014, Sun et al., 2015), Shanghai (Cheng et al., 2015), Nanjing (Zhuang et al., 2014) and Guangzhou (Cui et al., 2015, Huang et al., 2011), including chemical compositions, optical properties, source apportionment, and meteorological effects. However, aerosol chemistry in the cities of central China has not been sufficiently investigated or given adequate attention (Yang et al., 2013). Therefore, our knowledge of the composition and sources of atmospheric aerosol in central China remains poor. In this study, we conducted a field campaign in Xinzhou, a city located to the west of Mountain Taihang (average elevation: 1500 m a.s.l.). Xinzhou is also located in Shanxi Basin, one of the largest coal bases in China (Zhong et al., 2014), which is approximately 80 km north of Taiyuan city. Some recent studies characterized aerosol particles in Taiyuan, and the results showed that coal combustion, vehicle exhaust and industrial emissions were the three major sources of fine particles (He et al., 2015, Li et al., 2014). However, few studies have been conducted in the northern area in central China. Shi et al., 2014a, Shi et al., 2014b reported the levels, temporal and spatial distributions of carbonaceous aerosol and water-soluble ions during heating and non-heating periods in Xinzhou. Their results showed that coal combustion was a dominant source of organic carbon (OC) and elemental carbon (EC) during the heating period. The mass ratio of NO₃⁻/SO₄²⁻ also indicated a dominant contribution of stationary sources, e.g., coal combustion, with a considerable contribution from vehicle emissions. However, most previous studies were based on filter measurements with the sampling duration in days and even weeks, our knowledge of the air pollution levels, daily variations, and meteorological effects in central China remains less understood.

Here an Aerodyne Aerosol Chemical Speciation Monitor (ACSM) was deployed for the first time at a suburban site in Xinzhou in central China (Fig. 1), from July 17 to September 5, 2014 as an integral part of the Atmosphere, Aerosol, Cloud, and CCN (A²C²) campaign (Zhang et al., 2015). A major goal of this campaign was to investigate the relationship between aerosol composition and hygroscopicity and CCN. In this work, we have a detailed characterization of submicron aerosol composition, diurnal variations, and the influences of meteorological variables on aerosol characteristics. Also, the composition and sources of organic aerosol (OA) are investigated using positive matrix factorization (PMF) analysis, and the major source areas of aerosol particles are discussed.

Section snippets

Sampling site

The sampling site is located at Xinfuqu National Meteorological Observatory (38.07°N, 112.12°E) (700 m a.s.l.), which is a suburban site in Xinzhou in Xinding Basin. The site was surrounded by agricultural crops land with minor influences from industry emissions. A national road G108 is located at approximately 100 m to the east. The meteorological conditions during the study period are presented in Fig. 2. Wind speed was generally below 4 m/s with the prevailing winds from the north and the

Mass concentrations

Fig. 2 shows the time series of meteorological parameters and submicron aerosol composition. The average (±1σ) PM₁ concentration during the entire study period was 35.4 (±20.8) μg/m³, with daily average concentration ranging from 12.0 to 72.3 μg/m³. Considering that PM₁ generally contributed ∼60–70% of PM_2.5 in China (Wang et al., 2015b), the mass concentration of PM_2.5 derived from the PM₁ mass in Xinzhou city was generally below the secondary class of National Ambient Air Quality Standards

Conclusions

The chemical composition and sources of submicron aerosol at a suburban site in Xinzhou city in central China was characterized. The average PM₁ concentration was 35.4 μg/m³ during this study period, indicating that the Xinzhou city was less polluted compared with the megacities in North China Plain. The PM₁ was dominantly contributed by organic aerosol (33.1%) and sulfate (32.4%), followed by nitrate (14.4%) and ammonium (11.8%). Higher sulfate and lower nitrate contributions than those in

Acknowledgments

This work was supported by the National Key Basic Research Program of China (2013CB955801) and the Strategic Priority Research Program (B) of the Chinese Academy of Sciences (XDB05020501). We also thank the team members for their assistance during the A²C² campaign.

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Characterization of submicron aerosols at a suburban site in central China

Highlights

Abstract

Introduction

Section snippets

Sampling site

Mass concentrations

Conclusions

Acknowledgments

Atmos. Environ.

Atmos. Environ.

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Atmos. Environ.

Atmos. Environ.

J. Atmos. Solar Terr. Phys.

Atmos. Environ.

Atmos. Environ.

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Environ. Sci. Technol.

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Am. J. Respir. Crit. Care Med.

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