Ozone pollution increases as winter abates; IMD predicts one last spell of cold

Publish on February 09, 2020     Source: Hindustan Times

Air quality in the city remained ‘poor’ on Sunday, with an index value of 242 on the Central Pollution Control Board’s (CPCB) air quality index (AQI) bulletin, up from 222 the previous day. Experts and officials maintained that air quality would remain in the ‘poor’ category for the next several days, with winter conditions receding and summer meteorology taking over. As per the early air quality warning system for Delhi-NCR, “The air quality is likely to remain in the lower end of the ‘very poor’ category on February 10 and February 11,” with weak winds between 4 to 6kmph blowing from the west and northwest of NCR. As per a CPCB, forecast, the daily average AQI for Gurugram over the next three days will range between 202 to 239. The minimum temperature on Sunday fell slightly to 6.7 degrees Celsius from 7 degrees Celsius on Saturday, as per IMD data. The maximum temperature too fell to 20.6 degrees Celsius, down from 21 degrees Celsius on Saturday. The winter chill is likely to abate post-February 13 as both day and night temperatures in the city would inch closer to normal, according to weather experts. The India Meteorological Department (IMD) has predicted cold wave conditions around Monday as the minimum temperature over the next two days is likely to be around 5 or 6 degrees Celsius against a normal of 10 degrees Celsius.

Spike in ozone levels

As the winter chill subsides and concentrations of particulate matter pollutants drop to less-than-extreme levels, the city has begun seeing a spike in the concentration of another pollutant — ozone. The CPCB’s daily AQI bulletin recorded zero days in January when ozone was the primary pollutant in Gurugram, whereas in February so far, ozone was recorded as the primary pollutant on two days (February 8 and February 6). As per CPCB data, the 24 hour-average concentration of ozone on January 3 was 7.23ug/m3 and rose to 15.79ug/m3 on January 9. By January 15, the level of ozone stood at 33.68ug/m3. Concentrations of ozone in the past week alone have ranged between 46.5ug/m3 on February 3 and 69.53ug/m3 on February 9.

Hindustan Times had reported, on June 25 last year, of a spike in ozone levels while particulate matter pollutants remained at a season-low during the summer. At the time, ozone levels had touched as much as 268ug/m3. A senior scientist at the CPCB’s air quality lab in Delhi explained, “Presence of sunlight has a direct impact on the formation of ground-level ozone. Given the intense heat waves that occurred last year, the spike in ozone is plausible. Ozone levels tend to spike when winter conditions subside as well.”

Polash Mukherjee, an air quality expert with the National Research Development Corporation (NRDC) of India, explained at the time, “Ozone is a composite, or a secondary pollutant, which is formed due to chemical reactions undergone by other pollutants, such as sulphur oxides (SOx) and nitrogen oxides (NOx). Heat, which is a catalyst, facilitates these reactions. Hence, higher concentrations of ozone are seen during the summer months.” Ozone pollution is thus also a clear indicator of vehicular pollution through emissions such as SOx and NOx.

While experts said that the prevalent levels of ozone pollution are not as alarming as they were last summer, they indicate the recession of winter, along with rising temperatures and greater penetration of sunlight. They also warned of the possible health hazards of ozone pollution, which can include irritation of skin and eyes, tightening of the chest, exacerbation of the symptoms of emphysema, asthma and bronchitis and other respiratory ailments.

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