ANTHROPOGENIC, BIOGENIC AND PYROGENIC EMISSION SOURCES AND ATMOSPHERIC FORMALDEHYDE (HCHO) AND NITROGEN DIOXIDE (NO2) COLUMNS OVER DIFFERENT LANDUSE/LANDCOVERS OF SOUTH ASIA.

This study presents spatiotemporal variability of two important air pollutants, Formaldehyde (HCHO) and Nitrogen dioxide (NO₂), concomitant to underlying anthropogenic, biogenic and pyrogenic emission sources from different landuse/landcovers over South Asia, from 2005-2016, using OMI sensor onboard Aura satellite. Annual and seasonal spatial distributions for both the gases reveal that trends of change are linked with landuse/landcovers of different geographical regions of South Asia. Annual distribution of NO₂ shows a negative trend from 2012-2016, with annual decrease of ~1.06% in comparison to a rise, from 2005-2011 at a rate of ~1.86%/year. Analyzing seven study zones, distinctively identifies higher-emissions for both the gases from anthropogenic sources, in zones, 2,3,4 and 6, highlighting, emissions from megacities of Pakistan (Lahore, Faisalabad), India (Delhi, Kolkata, Lucknow) and Bangladesh (Dhaka), mainly due to urbanization, power-generation plants and mining-activities. Episodes of pyrogenic-emissions dominate seasonally in zones2 and 4, due to crop residue burning from Punjab plains of Pakistan and India and zone5 from Bangladesh and Myanmar. Isoprene, a precursor to HCHO is one of its main biogenic sources and higher emissions of HCHO dominate in zones3 and 7 with deciduous forests of lower Himalayas in northwest and Western Ghats in southwest India. In zones 4,5 HCHO emissions are dictated by isoprene emissions from Sundarbans in Bangladesh and palm-oil-plantations in Myanmar. [ABSTRACT FROM AUTHOR]