Characterization and morphological analysis of airborne PM₂.₅ and PM₁₀ in Agra located in north central India

PM₂.₅ and PM₁₀ samples were collected from road and semirural sites of Agra, the north central part of India. The average mass concentration of PM₁₀ was 278.67 ± 106.58 μg/m³ and of PM₂.₅ was 90.16 ± 7.21 μg/m³ at roadside while at semirural site it was 234.54 ± 128.27 μg/m³ for PM₁₀ and 89.12 ± 37.94 μg/m³ for PM₂.₅. Scanning electron microscopy coupled with energy dispersive spectrometer (SEM-EDS) was used to understand the difference in terms of shapes, morphology, and elemental composition of aerosols in PM₁₀ and PM₂.₅ and to further link them to the potential source as well as emission and transport of pollutants from different polluted areas. The SEM micrograph of PM₁₀ was different from PM₂.₅ size range particles at both sites. EDS spectra indicates the three main groups of particles i.e., C, O rich particles, Si, Na and Al rich particles and Mg, Ca, Fe, K, S, Co rich particles on the basis of their percentage contribution in PM₁₀ and PM₂.₅. PM₂.₅ constituted C, O (95.93%), Si, Al, Na (2.63%), S, Fe, K, (1.41%) and PM₁₀ constituted O, C (72.16%), Si, Al, Na (24.58%), S, K, Fe, Co (3.24%) respectively at roadside whereas at semirural site, PM₂.₅ and PM₁₀ constituted O, C (92.8%), Si, Al, Na (4.86%), Mg, K, Ca, Fe (2.32%), and O, C, (72.14%), Si, Na, Al (23.11%) and Mg, K, Ca, Fe (4.73%) respectively. Crustal elements such as Si, Na and Al rich particles are dominant excluding C and O in PM₁₀ and PM₂.₅ at roadside as well as semirural site. Correlation between element and particulate matter indicates two groups in which one group is highly significant (r > 0.90) and another group shows positive correlation (r > 0.53 to 0.90). Soot, tarballs, carbonaceous and mineral type particles were observed at roadside while aluminosilicates, quartz, fly ash and soil dust particles were observed at semirural site in PM₂.₅ and PM₁₀ respectively. It was concluded that SEM-EDS is a convenient method to identify the source of emission of particulate air pollution.