Good news for Delhi: Less pollution, the beginning of a clean winter
According to an analysis by the Center for Science and Environment (CSE), meteorological conditions due to extended periods of rainfall this year mean that the winter of 2021 is starting with a “cleaner threshold” than previous years. The analysis assesses the level of PM 2.5 from January 1, 2018 to October 15, 2021. PM 2.5 levels start violating the 24-hour norm, resulting in bad windy days when the monsoon retreats. It began in September in 2018 and 2020, while it was delayed until October in 2019 and 2021. The period from 1 September to 15 October is considered ‘pre-winter’ in the analysis. According to data provided by CSE, the average PM 2.5 level for the pre-winter season this year was 42 µg/m3, up from 62 µg/m3 in 2020, 51 µg/m3 in 2019 and 59 µg/m3 in 2018. M was less than 3. Anumita Roychowdhury, executive director, research and advocacy, CSE, said, “The strong monsoon and delayed rains contributed to a relatively clean pre-winter season this year. What we are seeing now is the effect of the weather. The number of fires is small, but it may also happen that rain may delay the fire. We cannot predict the extent to which pollution is going to return this winter. We cannot take it lightly that a clear pre-winter period will assure a clean winter.” CSE’s analysis of fire count data from NASA satellites indicates that this year’s pre-winter season fire counts are less than half last year’s. This is attributed to the rain or cloud cover seen this year, which may have hindered satellite imagery. The fire count (total for Punjab and Haryana) for the pre-winter season last year was 5,078, compared to 2,351 this year. In 2019, it increased to 2,299 from 1,765 in 2018. The total number of winter seasons in 2020 was 75,600, up from 48,155 in 2019 and 63,979 in 2018. The analysis noted that the contribution of stubble burning to air quality began around October 10, 2021, as did 2018 and 2020. This contribution peaked on 16 October this year when 14% of PM 2.5 levels in Delhi were attributed to stubble burning by the SAFAR monitoring system. The contribution of stubble burning to the level of PM 2.5 can go up to 40%. The average contribution per day last year was 12.2%, up from 8.9% per day in 2019 and 10.9% per day in 2018. Last winter, PM 2.5 levels were in the severe category for 23 days, down from 25 in 2019-20. , and 34 days in the winter of 2018-19. The winter seasonal average PM 2.5 levels were 194 micrograms per cubic meter in 2020, 180 micrograms per cubic meter in 2019 and 200 micrograms per cubic meter in 2018. Monsoon was clean in Delhi this year, but the summer was more polluted. The analysis indicates that this year, the monsoon season was the ‘cleanest’ for Delhi since 2018. The average PM 2.5 level during the monsoon season this year was 41 µg/m3, as against 44 µg/m3, 46 µg/m3 in 2020. 49 micrograms per cubic meter in 2019 and in 2018. This summer showed higher PM 2.5 levels than in 2020. The average PM 2.5 level was recorded at 57 micrograms per cubic meter in the summer of 2020, while a higher average of 79 micrograms per cubic meter was recorded this year.
