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 virus pandemic, the Government of India imposed a lockdown from 25 March 2020. In India, Kannur district was identified as the first “hotspot” of virus transmission and a “triple-lockdown” was implemented for a span of twenty days from 20 April 2020. This article highlights the variations of surface O3, NO, NO2, CO, SO2, NH3, VOC’s, PM10, PM2.5 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 O3 concentration was found to increase by 22% in this VOC limited environment. NO and NO2 concentrations were decreased by 61% and 71% respectively. The concentration of PM10 and PM2.5 were observed to decline significantly by 61% and 53% respectively. Reduction in PM10 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 O3 production over Kannur was found to have increased during triple-lockdown days. The concentration of CO (67%), VOCs (61%), SO2 (62%) and NH3 (16%) were found to decrease significantly from pre-lockdown days to triple-lockdown days. The air quality index revealed that the air quality at the observational site was clean during the lockdown.

No abstract

No abstract

No abstract

Continuous measurements of surface ozone (O 3 ), NOx (NO + NO 2 ) and meteorological parameters have been made in Kannur (11.9°N, 75.4°E, 5 m asl), India from November 2009 to October 2010. It was observed that O 3 and NOx showed distinct diurnal and seasonal variabilities at this site. The annual average diurnal profile of O 3 showed a peak of (30.3±10.4) ppbv in the late afternoon and a minimum of (3.2±0.7) ppbv in the early morning. The maximum value of O 3 mixing ratio was observed in winter (44±3.1) ppbv and minimum during monsoon (18.46±3.5) ppbv. The rate of production of O 3 was found to be higher in December (10.1 ppbv/h) and lower in July (1.8 ppbv/h) during the time interval 0800-1000 h. A correlation coefficient of 0.52 for the relationship between O 3 and [NO 2 ]/[NO] reveals the role of NO 2 photolysis that generates O 3 at this site. The correlation between O 3 and meteorological parameters indicate the influence of seasonal changes on O 3 production. Investigations were further extended to explore the week day weekend variations in O 3 mixing ratio at an urban site reveals the enhancement of O 3 . The variations of O 3 mixing ratio with seasonal air mass flows were elucidated with the aid of backward air trajectories. This study also indicates how vapor phase organic species present in the ambient air at this location may influence the complex chemistry involving (VOCs) that enhances the production of O 3 at this location.