Abstract
In situ measurements of PM (PM2.5 and PM10) 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 PM2.5 and PM10 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 PM2.5 and PM10 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 PM2.5, whereas mineral, aluminosilicates, and Cl-Na rich particles dominate in PM10. The morphology and elemental composition of the particles varied over the seasons due to atmospheric processing. The highest carbon concentration (56%) was observed in PM2.5 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 PM10 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.
Highlights
Particulate called aerosol air pollution is caused due to very small liquid and solid particles suspended in the air
An interesting feature was seen in seasonal analysis of carbonaceous aerosols in PM2.5 and PM10 particles at both sites
Morphological and elemental composition analysis of Particulate matters (PM) provides valuable information for the determination of their physicochemical properties and diverse sources. This analysis is essential for the assessment of health and ecological effects of airborne particles, which can not be obtained by mass concentration alone, and was not studied, in present study
Summary
Particulate called aerosol air pollution is caused due to very small liquid and solid particles suspended in the air. The data is very useful to analyze physicochemical characteristics, variability of particles in different seasons and their origin In this connection, the present study has been conducted covering the following objectives (i) to determine the mass, number concentration level and morphology of PM (PM2.5 and PM10) (ii) identification of elemental composition and (iii) source identification of aerosols over a World Heritage city at Agra, India during the period of 2010–2011. This can provide rapid qualitative, or with adequate standards, quantitative analysis of elemental composition with a sampling depth of 1–2 microns (Sielicki et al, 2011) Meteorological parameters such as atmospheric temperature (Tem.), wind direction (WD), wind speed (WS) and relative humidity (RH) were monitored at Agra station by automatic weather monitor (Envirotech WM251). The relative humidity was higher more than 46% for most of the study period except summer period; it is due to temperature along with the dry weather conditions
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