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Seasonal Source Apportionment of PM2.5 in Ningbo, a Coastal City in Southeast China

Category: Aerosol and Atmospheric Chemistry

Article In Press
DOI: 10.4209/aaqr.2018.01.0011
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Mengren Li1, Min Hu 1,4, Qingfeng Guo1, Tianyi Tan1, Bohan Du2, Xiaofeng Huang2, Lingyan He2, Song Guo1, Weifeng Wang3, Yingguo Fan3, Dandan Xu3

  • 1 State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China
  • 2 Key Laboratory for Urban Habitat Environmental Science and Technology, School of Environment and Energy, Peking University Shenzhen Graduate School, Shenzhen 518055, China
  • 3 Ningbo Environmental Monitoring Center, Ningbo 315012, China
  • 4 Beijing Innovation Center for Engineering Sciences and Advanced Technology, Peking University, Beijing 100871, China

Highlights

Temporal and spatial features of PM2.5 and sources in Ningbo were recognized.
Secondary ions, vehicle exhaust and coal combustion contributed most to Ningbo PM2.5.
Coal combustion contributed high in winter. Sea salt was not negligible in summer.


Abstract

With the rapid economic development and urbanization of China, haze and photochemical smog events have been frequently observed during the last decade. To explore the temporal and spatial pollution characteristics in Ningbo, a medium-sized coastal city located in the Yangtze River Delta (YRD) in southeast China, 24-h PM2.5 (particulate matter with aerodynamic diameter ≤ 2.5 µm) samples were simultaneously collected at five sites (two urban residential sites, two urban coastal sites, and one suburban site) from winter 2012 to autumn 2013. The average PM2.5 concentration was 53.2 ± 30.4 µg m–3. Furthermore, the concentration exhibited a seasonal variation: It was highest in winter and lowest in summer. The urban residential sites had the highest PM2.5 concentrations, followed by the urban coastal sites, and the suburban site had the lowest concentration. OM (Organic Matters) and secondary inorganic ions (sulfate, nitrate, and ammonium) were the dominant components of the PM2.5. As a coastal city with industrial zones, sources are more complex in Ningbo than in inland cities due to ship emissions and the interactions between land and sea, and the marine and atmospheric environments. Positive matrix factorization (PMF) was used to apportion the particle sources. Nine factors were resolved in this study: secondary nitrate, vehicle exhaust, secondary sulfate, coal combustion, industrial emission, ship emission, dust, biomass burning, and aged sea salt, with average contributions of 26%, 21%, 13%, 12%, 9%, 7%, 5%, 4%, and 3%, respectively. Secondary nitrate and vehicle exhaust were the major sources of PM2.5 pollution in Ningbo. Coal combustion contributed significantly in winter and autumn, whereas sea salt formed a considerable contribution in summer. This study suggests that decreasing the PM2.5 pollution in Ningbo requires not only strategies for reducing local primary sources but also joint inter-regional prevention and the control of air pollution in the YRD.

Keywords

PM2.5 Source apportionment Positive matrix factorization (PMF) Temporal and spatial distribution


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