Impact of COVID-19 lock-down on aerosol characteristics over urban and
rural environments in peninsular India
Abstract
The COVID-19 pandemic has caused concerns globally. However, there are
some positive effects because of the outbreak such as cleaner air caused
due to the lock-down. The pandemic and consequent lock-down (LD) has
caused significant reduction in anthropogenic activities, which provided
an unprecedented opportunity to study the contribution of manmade
short-lived climate forcing agents from two distinct environmental
locations; Bengaluru, a mega city and rural continental region,
Challakere, in southern part of peninsular India. We have used
continuous and simultaneous analytical measurements of the aerosol
loading and optical properties of near-surface aerosols for this
purpose. The near total shutdown of rail, road, and air traffic as well
as total closure of most of the business establishments and IT industry,
is found to dramatically reduce black carbon (BC) aerosol abundance.
Within one week of the LD, urban Bengaluru has witnessed nearly 60%
reduction in BC from fossil fuel (BCff) emissions, which is almost
comparable to that at a rural region like Challakere, located about 230
km northwest to Bengaluru. BC concentration at Challakere did not show
any major impact because of the lock-down. On other hand, BC from
biomass burning (BCwb) from both the locations didn’t show any
conspicuous impact. Consequently, the fraction of BCwb to total BC
became more than double and spectral absorption coefficient increased
from ~1.15 to ~1.4. The single
scattering albedo increased from its prevailing mean value of
~0.66 before LD to 0.74 during LD1 and then gradually
decreased with more relaxations. The measurements also have shown the
manner in which the environment responded to the gradual relaxation in
the subsequent phases of LD leading to gradual increase in emissions.
The findings re-emphasize that the emissions from fossil fuel combustion
in industrial and automobile sector are the major source of absorbing
aerosols over urban and semi-urban environments.