Temporal Variation of Atmospheric Aerosols and Associated Optical and Metrological Parameters

In the present study the particulate matter (PM) mass concentrations such as PM
2.5
and PM
10
for the winter (November 2016-February 2017) and summer (March 2017-May 2017) months were observed and analyzed. The aerosol optical properties such as MODIS-Aqua AOD (Aerosol optical depth) and Angstrom Exponent (AE) were found the significance seasonal variations. Monthly average AOD $(\sim 1.00)$ and AE $\gt1$ were observed in the winter season. Whereas, in the summer season monthly average AOD $(\sim 0.50)$ and AE $\lt1$ were observed. High monthly mean aerosol mass loading was recorded for both PM $_{2.5}\,(156.38 \pm 21.24 \mu \mathrm{g}/ \mathrm{m}^{3})$ and PM $_{10}(256.54 \pm 69.82 \mu \mathrm{g}/ \mathrm{m}^{3})$ in winter season. Whereas concentrations of PM $_{2.5}(25.47 \pm 16.95 \mu \mathrm{g}/ \mathrm{m}^{3})$ in April 2017 and PM $_{10}(127.68 \pm 51.31 \mu \mathrm{g}/ \mathrm{m}^{3})$ in May 2017 were found low in summer season, typically exceeding national standard. The mean PM $_{2.5} /PM_{10}$ ratio was $\sim 61$% in the winter season, is the indicative of a higher loading of the fine aerosol particles compared to the coarser aerosols in Varanasi. However the unfavorable meteorological conditions are also responsible for the highly increasing atmospheric pollution in Varanasi.