New Delhi: As Delhi grapples with its annual pollution crisis, a subtle but significant shift has occurred in the cocktail of pollutants that cloud its skies. Through most of October, the Capital\u2019s air has transformed \u2013 from being dominated by photochemical pollutants like ozone (O3) and carbon monoxide (CO) in the first 19 days to particulate matter (PM10 and PM2.5) in the past four days.<\/p>\n
The change, experts said, points to a sharp rise in combustion-driven emissions \u2013 primarily firecrackers, and aided by emissions from vehicles, industries, and local burning \u2013 that now define the city\u2019s toxic air.<\/p>\n
Between October 1 and 19, data from Central Pollution Control Board\u2019s (CPCB) Sameer app showed that ground-level ozone was the primary pollutant on 12 of the 19 days, with CO and NO2 also contributing significantly to the overall air quality index (AQI).<\/p>\n
Ozone, a secondary pollutant, is not directly emitted but formed when nitrogen oxides (NOx) and volatile organic compounds (VOCs) from vehicles, factories, and power plants react in bright sunlight. CO, meanwhile, is a direct byproduct of incomplete combustion from similar sources.<\/p>\n
In the first 19 days, Delhi\u2019s skies were clearer, the air was occasionally washed by light rain, and sunlight was abundant \u2013 ideal conditions for ozone formation. The city even recorded AQI reading of \u201csatisfactory\u201d on four days in this spell \u2013 on October 3 (88), October 7 (73), October 8 (81) and October 9 (100).<\/p>\n
But the chemistry of Delhi\u2019s air changed dramatically \u2013 particularly with the onset of Diwali.<\/p>\n
From October 20 onward, ozone and CO disappeared from the AQI charts, replaced by particulate matter \u2013 tiny, hazardous particles that penetrate deep into the lungs.<\/p>\n
Since then, PM10 was the lead pollutant on October 20, 22 and 23. To be sure, the Capital\u2019s AQI has remained in the \u201cvery poor\u201d category for four consecutive days since October 20. On Thursday, it stood at 305, marginally lower than Wednesday\u2019s 353 but still chokingly high.<\/p>\n
Overall, CPCB data shows a nearly 300-point swing this month \u2013 from 73 at the start of October to a peak of 353 as firecrackers and stagnant air combined to trap pollutants over the city.<\/p>\n
CPCB calculates sub-indices for eight individual pollutants (PM10, PM2.5, NO2, SO2, CO, O3, NH3, and Pb) at a monitoring location using its 24-hourly average concentration value (8-hourly in case of CO and O3). The worst sub-index is the AQI for that location.<\/p>\n
The overall average AQI is calculated by considering data for all stations, with a minimum data of three pollutants, out of which one should necessarily be either PM2.5 or PM10.<\/p>\n
CPCB classifies AQI between 0-50 as \u201cgood\u201d, between 51 and 100 as \u201csatisfactory\u201d, between 101 and 200 as \u201cmoderate\u201d, between 201 and 300 as \u201cpoor\u201d, between 301 and 400 as \u201cvery poor\u201d, and over 400 as \u201csevere\u201d.<\/p>\n
\u201cThe first half of the month was dominated with some rain, but also ample sunshine. Gases like ozone form when combustion sources like vehicles and emissions from industries combine with volatile organic compounds under sunlight. If O3 and CO were lead pollutants, it means that the impact of external combustion sources was minimal,\u201d said Sunil Dahiya, stating with rains stopping, the air has become drier and a drop in wind speed had led to accumulation of both local sources and cross-boundary emissions.<\/p>\n
\u201cEmissions from vehicles, industries and waste burning have begun to shoot up, leading to PM 2.5 and PM 10 rising. There is also dust, which leads to a spike in PM 10. However, from October 20, we have been seeing regular bursting of firecrackers, which is the primary combustion source at the moment,\u201d Dahiya said.<\/p>\n
Anumita Roychowdhury, executive director of research and advocacy at the Centre for Science and Environment (CSE), said the transition was inevitable. \u201cCombustion sources always dominate Delhi\u2019s air, except in peak summer when dust plays a bigger role,\u201d she said. \u201cIn the first half of October, rainfall helped settle particulate matter, allowing gases like ozone and CO to dominate. But once the weather turned dry and calm, particulates rose sharply. Add to that vehicles, industries, and the early burst of firecrackers, and you get the pollution mix we\u2019re seeing now.\u201d<\/p>\n","protected":false},"excerpt":{"rendered":"New Delhi: As Delhi grapples with its annual pollution crisis, a subtle but significant shift has occurred in…\n","protected":false},"author":2,"featured_media":248421,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[47],"tags":[135667,131288,192,135668,131296,135666,79],"class_list":{"0":"post-248420","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-environment","8":"tag-central-pollution-control-board","9":"tag-delhi-air-quality","10":"tag-environment","11":"tag-firecrackers-emissions","12":"tag-particulate-matter","13":"tag-pollution-crisis","14":"tag-science"},"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/posts\/248420","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/comments?post=248420"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/posts\/248420\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/media\/248421"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/media?parent=248420"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/categories?post=248420"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/tags?post=248420"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}