Measurements of aerosol optical depth and equivalent black carbon aerosols over a semi-arid station in Southern India

We reported the seasonal variations of columnar aerosol optical depth (AOD) and equivalent black carbon (EBC) from December 2018 to November 2019 in semi-arid station, Anantapur. Furthermore, using the two-component source apportionment model, we estimated the contribution of biomass burning (EBCbb) and fossil fuel combustion (EBCff) to the total EBC. The high AOD values at shorter wavelengths indicate that particle loading occurs primarily in fine mode aerosols. The high AOD500 was observed in the month of May (0.77 ± 0.19), and the low was in July (0.32 ± 0.11). The seasonal highest mean AOD500 was noticed during the summer (0.67 ± 0.12) followed by winter (0.49 ± 0.01), post-monsoon (0.43 ± 0.15) and monsoon (0.43 ± 0.17). The results revealed that both local emissions and long-range transported aerosols are primarily responsible for a significant spectral and temporal variability in AOD. In winter, the Angstrom exponent (α) was relatively high, whereas it was low in monsoon season. The mass concentrations of EBC, EBCff and EBCbb showed a strong diurnal and seasonal variations with in the study period. The highest and lowest EBC was noticed in winter and monsoon that is 2.64 ± 0.32, and 0.625 ± 0.16 μg/m3, respectively. The percentage contribution of annual mean EBC was 52.13% during the day and 47.86% during the night, respectively. With an average of 91.48%, EBCff contributes the most to total EBC during the study period. Furthermore, during all seasons, the hourly mean concentrations of EBC showed good agreement (r = 80) between the observed (Aethalometer) and MERRA-2 (Modern-Era Retrospective Study for Research and Applications). According to the MERRA-2 winds and Moderate Resolution Imaging Spectroradiometer (MODIS), the prevalence of fine mode particles throughout winter and summer is connected with continental air masses originating from India's central and northern regions.