Quantifying NO2 Reduction Before and During Covid-19 Movement Control Order In Major Cities And Industrial Area InPeninsular Malaysia Using Satellite Data Observation

Abstract

Movement Control Order (MCO) which was the restrictions or the lockdown that were implemented by the government of Malaysia from 18 March 2020 to 31 March 2020. Our study aims toevaluate Nitrogen Dioxide (NO2) changes, before and during the MCO in Malaysia's major cities especially the Klang Valley area as well as some industrial areas in the country. Tropospheric NO2 vertical column density from the TROPOspheric Monitoring Instrument (TROPOMI) was used to evaluate the spatial-temporal variations of the NO2 before and during the first phase of the MCO for theentire Peninsular. It is found that the NO2 concentrations is very prominent in Greater Klang Valley (GKV) but those location outside the GKV are related to Power Plant Stations in the country. Reductionof NO2 quantified by TROPOMI satellite showed a sharp decline for the daily readings, with the highestdifferences in Greater Klang Valley urban stations (− 52%) in Cheras, followed by Shah Alam (-43%).The lowest decline was recorded in Putrajaya with only (− 18%). The industrial site locations mostly show neutral readings or low increments as low as 5%. Only the location in Johor Bahru shows a verysharp increase up till 142% perhaps due to the 'business as usual' of the neighbouring country. Mediumcorrelation between ground measurement and TROPOMI column was obtained for the Greater Klang Valley locations R=0.455 before the MCO implementation, and R=0.588 after the MCO implementation. These results suggested that air pollution improvement in Greater Klang Valley area isgained from the implementation of the government full scale MCO or lockdown measures. The transportation activities played the key role in decreasing the NO2 level in Greater Klang Valley.