Beijing frequently experiences dust storms during spring, which result in deteriorated visibility and cause negative health impacts. In this paper, the dust particles were collected during a dust storm episode on 4–5 May 2017 in Beijing, and the samples before and after the dust storm were also collected. The morphology and elemental and mineralogical compositions of the dust samples were investigated using a transmission electron microscope equipped with an energy-dispersive X-ray spectrometer (TEM-EDX) and X-ray diffraction (XRD). The TEM-EDX results showed that the particles in the dust samples were mainly Si-rich, Ca-rich, S-rich, Fe-rich, Al-rich, Ti-rich, K-rich, Na-rich and Mg-rich particles. The XRD results demonstrated that the minerals in PM₁₀ samples were mainly clay, calcite, quartz, dolomite, plagioclase, potassium feldspar and hematite, in descending order of their contents. The clay minerals, having the highest content, were mainly kaolinite, chlorite and illite. The mixing state and aging degree of mineral particles before, during and after the dust storm episode behaved very differently. The mineral particles collected before and after the dust storm tended to have an internal mixing state, dominated by the S-rich particles internally mixed with alkaline mineral particles, revealing a more serious ageing degree. The mineral particles collected during the dust storm did not show clear internal mixing, revealing a less serious ageing degree. The amount of the Si-rich, Al-rich, Ca-rich and Ti-rich particles was highest during the dust storm, indicating that these particles mainly originated from long-distance transportation. The S-rich, Fe-rich, K-rich, Na-rich and Mg-rich particles were mainly enriched in the samples before and after the dust storm episode, indicating that they mainly originated from local sources. A comparison of the values of S/(Si + Al) in the individual particles with the particle sizes revealed that the finer mineral particles were associated with higher S contents before and after the dust storm, while the coarse particles were associated with lower S contents during the dust storm.

In the spring of 2023, two severe dust events occurred in the coastal city of Qinhuangdao, North China. We investigated organic carbon (OC) and elemental carbon (EC) in PM10 using an OC/EC analyzer and identified the morphology and elemental composition of individual dust particles using a scanning electron microscope coupled with energy-dispersive X-ray (SEM-EDX). Results showed that OC mass concentrations varied significantly from 12.6 μg m-3 to 74.6 μg m-3 and showed a significant positive correlation with the PM10 mass concentration. On average, OC made up 4.6% ± 1.1% and 4.3% ± 0.6% of the total PM10 mass in two dust periods. Particularly, the weight ratio of OC–to–coarse particles (PM2.5–10) was stable at approximately 2.8% ± 0.2%. In contrast, EC was less than 1.0% of the total PM10 mass, with an average value of 0.13% ± 0.26% and 0.28% ± 0.15% in two dust periods. According to SEM-EDX results, the average weight ratios of sulfur on detected individual dust particles were 0.48% and 1.88% in two dust periods, which were less than the previously reported value in non-dust days, indicating inefficient formation of secondary species on the dust particles. SEM-EDX analysis further revealed that approximately 5.2% of the particles (in number) were irregularly shaped C-dominated particles, which might be carbonaceous species-containing particles. These results highlighted that the dust plumes brought a certain amount of OC but limited EC from dust sources.

Traffic is a major source of anthropogenic aerosol in urban atmosphere. In this study, aerosol particles were measured with a TEM-EDX system at the roadside of a main road in the northwestern part of Beijing, China, under clear and hazy conditions. Soot, organic, sulfur-rich (S-rich), mineral, and metal particles, as well as the mixtures, were frequently encountered in aerosols. Under hazy conditions, S-rich particles coated with organic matter (S-OM particles) accounted for most of the total particles (15% to 24%), followed by soot particles (18% to 21%), organic particles (17% to 21%), non-mixed S-rich particles (10% to 18%), and S-rich particles with soot-, mineral-, or metal-inclusions (here referred to as S-inclusion particles) (11% to 15%). Under clear conditions, non-mixed S-rich and organic particles were dominant components, while mineral and soot particles were secondary components, among which, ~14% of the total particles had a sulfate core or OM coating; inclusions of mixture particles were often mixed with sulfate cores. In the sulfate core–OM shell structure particles, the ratio of core diameter to the whole particle diameter was ~0.52 under hazy conditions and ~0.60 under clear conditions, indicating a substantial sulfate and organic formation on the particles. Soot particles accounted for 18% to 21% of the total particles. The relative growth of aged soot particles was higher under hazy conditions than under clear conditions. In sum, particles from traffic emissions on a main urban road aged with the formation of sulfate and organic matter.

During the 2015 China Victory Day parade control periods, the air quality in Beijing hit the best record, leading to 15 continuous good days with an average PM_2.5 mass concentration 18 μg/m³, which provided a unique opportunity to study the ambient aerosols in megacity Beijing. The morphology and elemental composition of aerosol particles were investigated by transmission electron microscopy coupled with energy dispersive X-ray spectrometry (TEM-EDX). Five types of individual particles were identified, including homogeneous mixed S-rich particles (HS; 44.9%), organic coated S-rich particles (CS; 34.3%), mineral particles (10.5%), soot aggregates (7.21%) and organic particles (3.2%). The number percentage of secondary particles (including HS and CS) accounted for a large proportion with 79.2% during the control periods. The average diameter of secondary particles increased with relative humidity (RH), being 323 nm, 358 nm and 397 nm at the RH 34%, 43% and 53%, respectively, suggesting that the high RH might favor the growth of secondary particles. The higher proportion of CS particles may show great atmospheric implications and the CS particles may be formed by the condensation of secondary organic aerosols on pre-existing S-rich particles.