Abstract
ABSTRACT Particulate pollution is a serious environmental problem in China and has received much attention from the public. Airborne particles were collected during haze days in Beijing from June 2013 to May 2014. The morphology and elemental composition were investigated with transmission electron microscopy coupled with energy dispersive X-ray spectrometry (TEM-EDX). Six types of individual particles were identified, including sulfate particles (35.1%), mineral particles (26.0%), metal particles (13.5%), fly ash (13.2%), organic particles (5.9%), and soot aggregates (5.7%). Non-carbonaceous particles are mainly “S-rich”, ranging from 37.4% in spring to 56.7% in summer, with certain amount of “Si-rich”, “Ca-rich”, “Fe-rich”, and “K-rich” particles. The relative number percentage of sulfate particles shows a positive correlation with relative humidity (RH), suggesting that high RH might accelerate the sulfation of individual particles. Based on air mass backward trajectories, the high pollution in Beijing might be influenced by local emissions and air masses from adjacent areas south of Beijing. Air masses from Inner Mongolia carry higher concentrations of mineral particles and alleviate the abundance of “S-rich” and other particles.
Highlights
Atmospheric particles, which are typically composed of a complex constituent of organic and inorganic species, receive much attention because they are responsible for a multitude of climate and environmental issues in megacities in China (Huang et al, 2014)
The relative number percentage of sulfate particles shows a positive correlation with relative humidity (RH), suggesting that high RH might accelerate the sulfation of individual particles
Based on the transmission electron microscopy (TEM) images and elemental compositions, we propose a three-step sulfation mechanism on the individual particle surface explaining the above-mentioned secondary heterogeneous formation (Fig. 7)
Summary
Atmospheric particles, which are typically composed of a complex constituent of organic and inorganic species, receive much attention because they are responsible for a multitude of climate and environmental issues in megacities in China (Huang et al, 2014). Depending on their composition, they directly and indirectly affect the climate by scattering or absorbing solar radiation (Griessbach et al, 2013; Rozanov et al, 2014).
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