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. 2021 Apr 30;292:112694. doi: 10.1016/j.jenvman.2021.112694

Table 3.

Summary of the observed reduction in sulfur oxides SOx due to the COVID-19 lockdown.

COUNTRY STUDY SCOPE (AREA AND PERIOD IN, 2020) KEY FINDINGS REF.
BRAZIL São Paulo
Feb. 25 – Mar. 23		 SO2: A reduction of about 18.1–32.7% relative to 5-years average, and an increase of 8–16.2% relative to pre-lockdown. Nakada and Urban (2020)
CHINA Country wide, Jan. 1st – Feb. 25th SO2: Average concentration is 11 μg/m3(-21.4% year-on-year) Wang and Su (2020)
INDIA Countrywide
Feb. 15 – May 3
Lockdown: Mr. 25 –May 3		 SO2:
Central India: 4.1% increase to 11.5 ± 8.0 μg/m3 in 2020 relative to 11.1 ± 6.6 μg/m3 (2017–2019),
Indo Gangetic Plain: 19.6% reduction to 11.0 ± 5.2 μg/m3 in 2020 relative to 13.6 ± 7.4 μg/m3 (2017–2019)
North-west: 6.8% reduction to 10.1 ± 5.5 μg/m3 in 2020 relative to 10.9 ± 3.9 μg/m3 (2017–2019)
South: 16.5% reduction to 4.9 ± 1.9 μg/m3 in 2020 relative to 5.9 ± 2.7 μg/m3 (2017–2019)		 (V. Singh et al., 2020)
Ghaziabad, Jan. 10 – Apr. 19.
1st Phase: Mar. 25 – Apr. 14
2nd Phase: Apr. 15 –May 3.		 SO2: −14.3% as compared to pre-lockdown (to January 14, 2020), and −16.3% as compared to 2019 (i.e., April 14, 2019). Lokhandwala and Gautam (2020)
Chandigarh, Mar. 25 – May 17.
1st Phase: Mar. 25 – Apr. 16
2nd Phase: Apr. 17 –May 3.
3rd Phase: 4th – 17th May.		 SO2: Pre-lockdown 9.9 μg/m3, Lockdown: 1st phase 10.0 μg/m3, 2nd phase 11.4 μg/m3, 3rd phase 11.8 μg/m3. Mor et al. (2021)
SPAIN Countrywide, Jan. 1 – Jun. 20
Strict lockdown: Mar. 14 –May 3.
Relaxed lockdown: May 5 – Jun. 20.		 Urban areas:
  • ➢

    Prior to lockdown 3.72 ± 0.36 μg SO2/m3

  • ➢

    Strict lockdown 3.15 ± 0.24 μg SO2/m3 (−15.4%)

  • ➢

    Relaxed lockdown 2.97 ± 0.23 μg SO2/m3 (−20%)

Rural areas:
  • ➢

    Prior to lockdown 2.01 ± 0.22 μg SO2/m3

  • ➢

    Strict lockdown 1.86 ± 0.16 μg SO2/m3 (−7.3%)

  • ➢

    Relaxed lockdown 1.72 ± 0.14 μg SO2/m3 (−14.6%)

 Martorell-Marugán et al. (2021)
Barcelona
March 14–30		 SO2: Avarage concentration of 1.0 μg/m3 relative to 1.2 μg/m3 pre-lockdown (−19.4%) in Urban background. Tobías et al. (2020)
EAST ASIA Beijing-Tianjin-Hebei (BTH) & Wuhan, China; Seoul metropolitan area (SMA), S. Korea; Tokyo metropolitan area (TMA), Japan. 1st – 29th Feb. SO2:
BTH: 1.3E16 ± 1.1E16 molecule/cm2 in 2020 relative to 1.3E16 ± 1.4E15 molecule/cm2 in 2019 (−0.01%).
Wuhan: 1.1E15 ± 8.1E15 molecule/cm2 in 2020 relative to 3.9E15 ± 2.3E16 molecule/cm2 in 2019 (−71.5%)
SMA: 1.1E16 ± 8.4E15 molecule/cm2 in 2020 relative to 8.2E15 ± 9.8E15 molecule/cm2 in 2019 (+38.1%).
TMA: 9.4E15 ±8E15 molecule/cm2 in 2020 relative to 2.7E15 ± 8.1E15 molecule/cm2 in 2019 (+243.4%)		 Ghahremanloo et al. (2021)