Abstract
Enhanced transport of dust with the prevailing mid to upper tropospheric westerly winds from arid regions in South-west Asia and North-west India into the Indo-Gangetic Plain (IGP) and the influx of marine aerosol from the Arabian Sea (AS), Tropical Indian Ocean (TIO) and Southern Bay of Bengal (SBoB) into India along with the low level south-west wind flow during the onset of the South-west (SW) monsoon, 2014 was observed in campaign mode. Ambient airborne particulates (PM2.5 and PM10) were collected at 9 sites in and around IGP, India, viz. Patiala, Delhi, Lucknow, Varanasi, Giridih, Kolkata, Darjeeling, Bhubaneswar and Nagpur; over AS, TIO and SBoB providing a glimpse into the aerosol loading and its transport mechanisms. The highest average PM2.5 (61.8 ± 18.6 μg m−3) and PM10 (182.2 ± 58.0 μg m−3) mass concentrations were recorded at Delhi (upper IGP) and Lucknow (middle IGP) respectively. Average PM2.5 (18.1 ± 10.1 μg m−3) and PM10 (39.6 ± 15.8 μg m−3) levels recorded over the open oceanic regions in AS, TIO and SBoB were much lower than those observed over the land stations and the average PM2.5 recorded over coastal AS and SBoB (49.1 ± 28.7 μg m−3).
Cluster analysis, Potential Source Contribution Function (PSCF) and Concentration Weighted Trajectory (CWT) analysis portray that PM2.5 and PM10 levels at the land stations were influenced by weak to moderate contributions from AS, BoB, the arid South-west Asia and North-west India, peninsular India and from the polluted IGP region.
•PM2.5 & PM10 levels were observed to be highest over upper and middle IGP, India and lowest over marine regions.•Coarse mode aerosols were dominant over middle and upper IGP, India.•PM2.5 & PM10 levels levels exhibited prominent seasonal variation over all sites.•Cluster, PSCF and CWT analyses portray possible advection of marine and dust aerosols to the land sites.