Air Monitoring Analysis for April-September 2021

Preview
Humidity and Rainfall tend to coagulate aerosols in the air and help clearing the air. The intensity of coagulation that takes place depends on a variety of factors and it cannot be foretold with certainty its level of effectiveness. But it is important to take a note of rainfall that occurs in a region to understand its effect on air physiology. Rainfall patterns have been changing every year and a look at the five-year district rainfall provides some insights in varying rainfall.

Year Rainfall (mm) Year Rainfall (mm)
2016 41.5 2019 59.1
2017 117.9 2020 41.6
2018 164.8 2021 523.4*

2016-2020 rainfall from IMD for South Delhi; *IARI Meteorological Database System (1.9.2021 to 21.09.2021)

AIR QUALITY MONITORING

  • AQI starts declining from April onwards in both the periods[1] subject to increase in humidity levels due to pre-monsoon rainfalls and it is further showing declining trend during the monsoon period.
  • Asansol and Korba both lead the AQI curve.
  • The AQI for 2021 period indicates 7 cities in the AQI band of 150 to 350 whereas majority of the cities were in the AQI band of 150 to 250 barring Asansol which had an AQI of 376
  • 2021 has seen rise in AQI of Korba which remained under 100 during June-September period in 2020
  • Asansol’s AQI remained between 100 and 150 for both the periods from April to September for 2020 and 2021

Table 1 – AQI Categorised

January to September 2020 and 2021

Note: ‘-‘ indicates no value for the period. Data for September is accounted upto 21.09.2021

  • Kolkata remained in the good AQI category i.e. <50 for April to September period in 2020. The median value for 2020 was 34 where as it reached 41 in 2021
  • Median value of AQI for Korba in 2020 was 103 whereas in 2021 it is 133 for the 9 months period from January till September indicating that the AQI has worsened
  • Median value of AQI for Asansol in 2020 was 144 whereas in 2021 it is 118 for the 9 months period from January till September indicating that the AQI has improved in 2021. Is it due to 36% excess rainfall in Bardhamaan district from January 2021 to September 2021? (Select State ‘West Bengal’ to see results)
  • Median value of AQI for Delhi remained 83 in 2020 and 105 in 2021 for the 9-month period from January till September indicating that the AQI values have increased. As per IMD, South Delhi District received normal rainfall from January to 21 September
  • Median value of AQI remained at 74 for Jharsuguda for both periods.

Table 2 – Month wise past and present AQI Categorisation

The positive transition from moderately polluted to satisfactory AQI from 2019 onwards is observed over most of the months whereas few industrial districts/cities like Korba, Asansol and New Delhi almost came back pre 2020 status in few of the months.

 Table 3- Number of Days Devices Worked and Number of Days AQI Category in a City

0-50 51-100 101-200 201-300 301-400 >401 Not Worked
Uttar Pradesh Apr-21 3 10 4 0 0 0 13 30
May-21 4 10 4 0 0 0 13 31
Jun-21 13 9 1 1 0 3 3 30
Jul-21 13 9 1 1 0 3 4 31
Aug-21 26 0 2 0 0 0 3 31
Sep-21 18 1 0 1 0 1 0 21
Raigarh Jun-21 4 20 0 0 0 0 6 30
Jul-21 4 20 0 0 0 0 7 31
New Delhi Apr-21 0 8 22 0 0 0 0 30
May-21 0 9 22 0 0 0 0 31
Jun-21 0 29 1 0 0 0 0 30
Jul-21 0 30 1 0 0 0 0 31
Aug-21 2 26 1 0 0 0 2 31
Sep-21 10 10 0 0 0 0 1 21
Korba Apr-21 0 4 25 1 0 0 0 30
May-21 0 5 25 1 0 0 0 31
Jun-21 0 4 8 9 7 2 0 30
Jul-21 0 4 9 9 7 2 0 31
Aug-21 5 15 7 2 1 1 0 31
Sep-21 1 2 3 0 0 0 15 21
Kolkata Apr-21 5 24 1 0 0 0 0 30
May-21 5 25 1 0 0 0 0 31
Jun-21 27 3 0 0 0 0 0 30
Jul-21 28 3 0 0 0 0 0 31
Aug-21 11 6 0 0 0 0 14 31
Jharsuguda Apr-21 0 22 8 0 0 0 0 30
May-21 0 23 8 0 0 0 0 31
Jun-21 13 15 1 1 0 0 0 30
Jul-21 14 15 1 1 0 0 0 31
Aug-21 25 3 0 0 0 0 3 31
Asansol Apr-21 0 2 22 3 1 0 2 30
May-21 0 2 23 3 1 0 2 31
Jun-21 0 7 23 0 0 0 0 30
Jul-21 0 7 24 0 0 0 0 31
Aug-21 2 11 8 2 0 0 8 31
Sep-21 4 6 9 0 0 0 2 21
Sambhalpur Apr-21 0 7 23 0 0 0 0 30
May-21 0 7 24 0 0 0 0 31
Jun-21 0 21 9 0 0 0 0 30
Jul-21 0 22 9 0 0 0 0 31
Aug-21 12 14 2 0 0 0 3 31
  • Raigarh remained in Satisfactory category for 83% of days the device worked (24) and the remaining number of days it remained in good category
  • Delhi – In April and May the AQI remained 70%-73% of the times device worked in moderately polluted. Majority of the days in June till July remained in Satisfactory conditions whereas in September 50% of the times it has been in good and satisfactory category of AQI
  • Korba – Moderately polluted for most of the times in April and May whereas in June and July 60% of the AQI categories migrated to poor, very poor and severe. In August, maximum number of days remained in satisfactory category (15), 7 days in moderately polluted. Severe days reduced to 1 day
  • Kolkata – It has remained the best in terms of maximum number of days in good and satisfactory category. In April and May maximum number of days were in satisfactory category whereas the AQI categories transitioned to good category for June and July. No poor, very poor or severe days observed.
  • Jharsuguda – In April and May the AQI categories were in satisfactory and moderately polluted category – 73 & 74% of the days respectively. In June and July AQI category days got distributed in good and satisfactory category equally (13,15 & 14, 15) and 1 day each in moderately polluted and poor category. August led the good category for Jharsuguda at 25 days
  • Asansol – Asansol showed a completely different trend in terms of maximum number of days (ranging 22-24) for the months of April, May, June and July in moderately polluted category. August showed a bit of improvement with 11 days in satisfactory category
  • Sambalpur – April and May months remained maximum in moderately polluted category (23 & 24 days) and rest of the days in satisfactory category. The AQI improved with maximum number of days migrating to satisfactory category in June and July (21 & 22 days), an equal number of days i.e. 9 days remained in moderately polluted. In August AQI was in good and satisfactory category (12 & 14 days respectively).

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