Particulate Matter Pollution in Urban Cities of India During Unusually Restricted Anthropogenic Activities

The outbreak of COVID-19 is a global public health challenge and has affected many countries, including India. The nationwide lockdown was imposed in India from March 25 to May 31, 2020 to prevent the transmission of COVID-19. The study intends to assess the impact of the absence of major anthropogenic activities during the various phases of the COVID-19 lockdown (LDN) period on the daily mean concentrations of PM2.5 and PM10 in six populated cities of Jaipur, Jodhpur, Kota, Udaipur, Ajmer, and Alwar in the state of Rajasthan. Investigation has been done for the different periods, including the pre-lockdown—PRELD (January 1–March 4, 2020), partial lockdown—PLDN (March 5–24, 2020), COVID-19 lockdown—LDN (March 25–May 31, 2020), and unlocking—ULC (June 1–August 31, 2020) phases. We have also compared the mean concentrations of PM2.5 and PM10 with the same period of the year 2019. A significant improvement in air quality during the COVID-19 LDN period was noticed in all cities compared to 2019 and for the same period of the year 2020. However, the levels of PM2.5 and PM10 were seen to rise during the second, third, and fourth LDN phases compared to the first LDN, indicating that the subsequent lockdowns started with some relaxations and dusty conditions. On the other hand, wind-blown dust is another vital source of PM10, resulting in high concentrations in the summer months (April–May). Significant reductions in PM2.5 (~25–50%) and PM10 (20–37%) in all six cities during the LDN period compared with PRELD were estimated. However, with significant variations from city to city, the lowest reductions in PM2.5 (~25%) and PM10 (~20%) were measured in Jodhpur and Ajmer, respectively. It was noticed that the episodes of rainfall and transport of oceanic air masses resulted in a reduction of particles during the ULC period compared to the LDN period. The air quality index was, more or less, in the “good to satisfactory” category during the first 3 LDN periods, whereas it was moderate for Jodhpur, Jaipur, and Ajmer during the last LDN period. The study will be helpful to determine mitigation policies to minimize air pollution, especially in developing regions. Copyright © 2022 Yadav, Vyas, Kumar, Sahu, Pandya, Tripathi, Gupta, Singh, Dave, Rathore, Beig and Jaaffrey.

Anomalous behaviour of ozone under COVID-19 and explicit diagnosis of O3-NOx-VOCs mechanism.

Air pollution is linked to higher rates of human mortality especially those infected with COVID 19. Ozone is a harmful pollutant and is responsible for many health issues. However, some reports suggest that ozone is a strong disinfectant, and can kill the viruses. We hereby, report on the vulnerability of ozone due to COVID-19 lockdown whose levels flutter from surging to saturation in a highly polluted Indian capital, due to significant decline in anthropogenic emissions of ozone precursors. Average observed levels stabilized at 30 ppb, 12 ppb, 740 ppb, and 900 ppb for ozone (O3), nitrogen dioxide (NO2), carbon monoxide (CO) and volatile organic compounds (VOCs) respectively during lockdown period from 27th March to 10th April 2020. The NO2, CO and VOC declined by 50 %, 37 %, 38 % respectively during the lockdown period of 2020 as compared to similar period in 2019. The anomalous response of ozone during the lockdown is explained by resolving the poorly known complex O3-NOx-VOCs mechanism with the help of data from air monitoring stations in Delhi, India. The data obtained from this study advances the fundamental understanding of ozone chemistry that may lead to improved ozone parameterization in chemical transport models and better planning of ozone risk management strategies for any global mega cities.

Towards baseline air pollution under COVID-19: implication for chronic health and policy research for Delhi, India

The Megacity of Delhi, home to 19 million inhabitants, is infamous for its poor air quality mainly due to anthropogenic emissions. While the COVID-19 pandemic is a health emergency, lockdown due to it saw an unprecedented decline in emission sources of pollutants by ~85%-90% in Delhi, resulting in sharp decline in the concentration of majority of pollutants. Here we report the experimental estimate of baseline level that is defined as the minimum level reached after lockdown under consistent fair weather condi-tion of major criteria pollutants. This may be consi-dered as an indicator of the background levels to which the population is chronically exposed. The con-sequences of such chronic air pollution exposure are excess respiratory and cardiovascular morbidity and mortality which are reported to be more serious than severe pollution episodes by epidemiologists. As the lockdown which was imposed on 24 March 2020, was extended during April and May, we present the pre-vailing ambient pollution levels and compare them with the baseline levels. Results are based on India’s largest monitoring network of 34 stations in Delhi. The findings are critical for policymakers to fine-tune ambient air quality standards and regulations leading to the development of effective risk management poli-cies and control strategies. © 2020. All rights reserved.