![]() ![]() ![]() Studies from the Indian Institute of Technology, Kanpur in 2015, and a joint study by The Energy Research Institute (TERI) and the Automotive Research Association of India (ARAI) in Delhi in 2018 have shown that during summer, Delhi experiences relatively higher contribution of dust compared to winter also, the share of secondary particulates that form from the gases in the atmosphere, is comparatively lower. ![]() This is in contrast to winter - with its inversion, lower mixing height of air, and cold and calm conditions that trap the air and the pollutants in it.” ![]() The characteristics of summer pollution are different: there are high winds, intermittent rains and thunderstorms, and high temperature and heat waves. Normally, every year, winter pollution is what draws our attention. Says Anumita Roychowdhury, executive director-research and advocacy, CSE: “This pandemic-led change in air quality has helped us understand summer pollution. Ozone can be controlled only if gases from all sources are controlled. Ozone is not directly emitted by any source but is formed by photochemical reactions between oxides of nitrogen (NOx) and other volatile organic compounds (VOCs) and gases in the air under the influence of sunlight and heat. That is why ozone has a short-term standard – one hour and eight hours, as opposed to 24 hours for other pollutants. It is a highly reactive gas even short-term exposure (one hour) is dangerous for those with respiratory conditions and asthma. This has emerged from a new analysis of 22 mega and metropolitan cities in India, done by Centre for Science and Environment (CSE).ĬSE researchers point out that ozone is primarily a sunny weather problem in India that otherwise remains highly variable during the year. While the PM2.5 and NO 2 curves fell and flattened dramatically in cities – a phenomenon that hogged the national attention - tropospheric ozone pollution (henceforth ozone) increased and even breached standards in several cities: a fact that was not noticed as widely. New Delhi, June 24, 2020: New analysis of summer air quality trends during the national lockdown that started on March 25, 2020, reveals a mixed trend. Crop fires in April were quite extensive in Punjab and Haryana, but their impact was blunted by the overall very low background and local pollution.As traffic nearly stopped, the daily NO 2 curve flattened in all cities.While particulate levels hit the lowest possible range during lockdown phases, the share of PM2.5 fraction in the overall particulate concentration increased.This indicated higher level of exceedence in cities. Instead of the official method of considering only the fixed eight-hour average (from 8 PM to 4 PM) to assess ozone levels, CSE adapted the global best practice of calculating the maximum eight-hour average of the day.While PM2.5 and NO 2 levels plummeted, invisible ozone became the most prominent pollutant in several cities.Analysis brings out many learnings on summer pollution from the lockdown period in Indian cities ![]()
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