SEM-EDX Characterization of Individual Coarse Particles in Agra, India

Natural and anthropogenic chloride aerosols make up a significant fraction of atmospheric particulate matter and play important roles in the boundary layer chemistry. Here we provide a review of the mixing characteristics of chloride aerosols and the subsequent atmospheric implications, which are rarely considered in current field and modeling studies. Single-particle analytical techniques have shown that a large fraction of chlorides mix internally with other components, in particular inorganic salts and organic matters, instead of existing separately. In marine and coastal regions, high proportions of chloride aerosols usually mix with inorganic substances (e.g., Mg, Ca, K, N, S), while small quantities of them are coated by organic matter. In forest, grassland, and agricultural areas, most chlorides in biomass burning particles mix with or are coated by organics. In industrialized urban areas, the chloride aerosols often co-exist with heavy/transition metals (e.g., Zn, Pb) and are coated by organic materials in aged plumes. Moreover, secondary chlorides also mix with mineral dusts, nitrates, and sulfates. The mixing of chloride aerosols with insoluble substances can inhibit their hygroscopic properties, which in turn affects the cloud condensation nuclei activation and heterogeneous reactivity. The encasing of chloride aerosols within light-absorbing substances changes their optical properties and subsequently causes atmospheric warming. This paper emphasizes the complexity of the mixing of chloride aerosols, as well as the potential atmospheric implications thereof, and proposes some research topics deserving future study.

Section: Analytical Techniques For Particle Mixing Statementioning

confidence: 99%

Mixed Chloride Aerosols and their Atmospheric Implications: A Review

Wang

Yang

et al. 2017

“…Electron scanning microscopy coupled with energy dispersive spectrometer (SEM-EDS) analysis can provide substantial information on the elemental composition, mineral types, size distribution, and morphology of the airborne particle, which cannot be achieved by bulk chemical analysis alone (Sharma and Srinivas 2009;Srivastava et al, 2009;Pachauri et al, 2013). SEM-EDS is an analytical method for surface elemental analysis, with a potential detection limit of 0.1-0.5 wt.% for most elements (Haley et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

Study of Surface Morphology, Elemental Composition and Origin of Atmospheric Aerosols (PM2.5 and PM10) over Agra, India

Pipal

Jan

Satsangi

et al. 2014

109

In situ measurements of PM (PM 2.5 and PM 10 ) particles were carried out using a medium volume air sampler (offline) and particle number concentrations of PM were measured by a Grimm aerosol spectrophotometer (online) during the study period of 2010-2011. The morphology and elemental composition analyses of PM were performed by Scanning Electron Microscopy (SEM) and Energy Dispersive Spectrometry (EDS), respectively. The average mass concentrations of PM 2.5 and PM 10 were 97.2 and 242.6 µg/m 3 at roadside (RD) and 121.2 and 230.5 µg/m 3 at a semirural (SR) site, respectively. These concentrations were substantially higher than the NAAQS, WHO and USEPA standards. The highest mass and number concentrations of PM 2.5 and PM 10 were observed during winter, followed by those during the post-monsoon period and summer, with the lowest in the monsoon period. SEM and EDS analysis of PM indicated the presence of soot, mineral, tarballs, fly ash, aluminosilicates/silica, fluorine, carbon rich, and Cl-Na rich particles. Of these particles, soot, tarballs, and F-C rich particles dominate in PM 2.5 , whereas mineral, aluminosilicates, and Cl-Na rich particles dominate in PM 10 . The morphology and elemental composition of the particles varied over the seasons due to atmospheric processing. The highest carbon concentration (56%) was observed in PM 2.5 during summer at the RD, while in the monsoon, postmonsoon period and winter the carbon concentration was ~9% lower at the RD as compared to the SR. However, the concentration of carbon in PM 10 was ~38% higher at the RD as compared to SR during both summer and winter. Air mass backward trajectory cluster analysis was performed, and the results indicate that the aerosol loadings over Agra are mainly transported from the Middle East and Arabian Sea during the summer and monsoon period, while during the pre-monsoon period and winter the aerosol loadings came from the northern region, and were due to the burning of biomass and coal, as well as other local activities.

“…Some samples show high concentrations of carbon and oxygen as the main elements in EDS spectrum. These are presented in previous studies as characteristics of organic biogenic particles that can be identified easily (Srivastava et al, 2009;Wang and Luo, 2009;Pachauri et al, 2013;Singh et al, 2014). Sometimes these particles are found in clusters.…”

Section: Surface Morphologymentioning

confidence: 99%

“…The results showed that the particles are round, flaky, spherical and irregular shapes. Depending on the elemental composition and observed shapes the particles were divided into two groups (Wang and Luo, 2009;Pachauri et al, 2013). i) Soil dust particles: these particles possess crystalline or irregular shape shown in Fig.…”

Section: Surface Morphologymentioning

confidence: 99%

PM10 Sampling and AOD Trends during 2016 Winter Fog Season in the Islamabad Region

Bulbul

Shahid

Chishtie

et al. 2018

PM 10 samples were collected during intensive fog days in Islamabad, Pakistan, to investigate the impact of particulate matter on fog formation. The PM 10 concentrations were monitored at the Institute of Space Technology site using a highvolume air sampler and its elemental composition was studied using Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS). Sampling was done for a duration of 24 hours on selected days, including all foggy days in a period from January 2016 to . On most occasions, PM 10 levels were considerably high as compared to permissible limits of both Pak-NEQS and WHO guidelines. It has been observed that the air quality during fog days was much worse, with elevated levels of particulate matter observed during foggy days. The SEM-EDS revealed the presence of different elements including some metals Si, K, Ca, Mg, Zn, Fe, Cr, Pb, Al etc. The morphological studies suggest that most of the particles are crystalline in shape, suggesting their main source as soil. Some samples also showed round spherical shape which refers their anthropogenic source. The sun photometer observations of aerosol optical depth (AOD) and satellite observations from Aqua's Moderate-resolution Imaging Spectro-radiometer (MODIS) showed significant correlation. Moreover, elevated level of AOD were found during heavy fog days. The validated high satellite AOD were associated with high PM 10 concentration during heavy fog days.