Analysis of Absorption Characteristics and Source Apportionment of Carbonaceous Aerosol in Arid Region of Western India

Abstract

The present work analyses the equivalent Black Carbon (EBC) data obtained using Aethalometer (AE-33) located at India Meteorological Department, Jodhpur, Rajasthan during the year 2016. The annual mean EBC concentration is 5.76 µg m−3 and the monthly mean concentration is maximum (12.12 µg m−3) in January and minimum (1.27 µg m−3) in December. The seasonal mean of wind speeds are 1.94, 2.02, 1.34, 1.02 m s−1 and the calm percentages are 7, 5.7, 28.7, 25.7% during pre-monsoon (MAM), monsoon (JJAS), post-monsoon (ON) and winter (DJF), respectively. The night time EBC concentrations are more than the day time concentrations due to the shallowness of the boundary layer and local anthropogenic activities. The Concentrated Weighted Trajectories (CWT) are calculated using back trajectories ending at 100 m above ground level at Jodhpur station using National Centre for Medium Range Weather Forecast (NCMRWF) Global Forecast System (GFS) based reanalysis T574 data. The CWT, directional source region analysis reveals the effect of long-range transport in the winter season with a 60% of probability of source regions from the W, NW direction of observational site. Source apportionment also carried out by assuming alpha (at 470-, 950-nm wavelengths) close to 1 for anthropogenic emissions and alpha close to 2 for biomass burning aerosols. The monthly mean biomass burning concentration is found maximum (2.58 µg m−3) in November and minimum (0.22 µg m−3) in July.