Peer Review #2 of "Air quality improvement during triple-lockdown in the coastal city of Kannur, Kerala to combat Covid-19 transmission (v0.1)"

Abstract

The novel SARS-CoV-2 coronavirus that emerged in the city of Wuhan, China, last year has since become the COVID-19 pandemic across all continents. To restrict the spread of the viruspandemic, the Government of India imposed a lockdown on 25 March 2020. In India, Kannur district was identified as the first "hotspot" of virus transmission and a "triplelockdown" was implemented for a span of twenty days from 20 April 2020. This paper highlights the variations of surface O 3 , NO, NO 2 , CO, SO 2, NH 3 , VOC's, PM 10 , PM 2.5 and meteorological parameters at the time of pre-lockdown, lockdown and triple-lockdown days at Kannur town in south India using ground-based analyzers. From pre-lockdown days to triple-lockdown days, surface O 3 concentration was found to increase by 22% in this VOC limited environment. NO and NO 2 concentrations were decreased by 61% and 71% respectively. The concentration of PM 10 and PM 2.5 were observed to decline significantly by 61% and 53% respectively. Reduction in PM 10 during lockdown and triple-lockdown days enhanced the intensity of solar radiation reaching the lower troposphere, and increased air temperature and reduced the relative humidity. Owing to this, surface O 3 production over Kannur was found to have increased during triple-lockdown days. The concentration of CO (67%), VOCs (61%), SO 2 (62%), and NH 3 (16%) were found to decrease significantly from pre-lockdown days to triple-lockdown days. The air quality index (AQI) revealed that the air quality at the observational site was clean during the lockdown.