Air quality during the Covid-19 Pandemic in Denpasar City

According to LAPAN, PM 10 concentrations decreased in March 2020 compared to the same month in the previous year. It is also suspected that there was a decrease in the concentration of particulate Nitrogen Dioxide (NO2) in a number of countries in March 2020 which carried out a lockdown as an effort to prevent the spread of the corona virus 19. Some media said that in China the first to apply quarantine, the cessation of plant operations and the loneliness of roads had a significant impact on improving air quality . Based on the journal Nature published on May 19, 2020, Quéré et al. said that CO2 globally had fallen by around 17% as shown in the Figure below. Quoted from CNN Indonesia also informed that BMKG said that due to the PSBB in the capital city of Jakarta there was a decrease in pollution levels.

The global daily average CO2 image as revealed by Quéré et al in the journal Nature, where the black line in the left figure indicates the annual average daily emissions and the red line indicates daily CO2 emissions until April 2020. Meanwhile the right picture is the daily CO2 emissions from January until April 2020.

How is the air quality in Denpsar City with a policy work from home (WFH) during the covid-19 pandemic. With this policy a decline in community movement activities can be seen from the decrease in traffic volume . The results of the 2017 and 2018 Greenhose gas inventories the potential for emissions in the city of Denpasar and in the province of Bali is greatest in the energy sector which includes energy sourced from transportation activities.

Air quality at the time of community activity restriction (PKM) in Denpasar City in April, May and June based on the Pollutant Standards Index (PSI) for PM 10, SO2 and NO2 components was good, while for CO and O3 components it fluctuated from good to not healthy. The data was obtained from the monitoring of the air quality of the automatic ambient air quality monitoring station in Lumintang, Denpasar City (Bali Forestry and Environment Service, June 26, 2020). Average air quality during the covid-19 pandemic for PM 10, SO2, CO and NO2 components did not differ significantly from the previous month. But the concentration of O3 at the end of April to early May is at very unhealthy to dangerous levels. In the previous month O3 level was good. This is related to the amount of ultrafiolet (UV) light reaching the lower troposphere. At that time the cities of Denpasar and Bali generally received maximum sunlight in accordance with the sun's circulation. Ozone (O3) belongs to secondary pollutants formed in the atmosphere from photochemical reactions. The O3 reaction formed from NOx pollutants is as follows.

                        NO₂ + sunlight  NO + O

                        O + O₂          O₃

Ozone is also formed when electrical sparks pass in oxygen. Ozone is unique because as a secondary pollutant it is also an oxidizing agent. High-energy solar UV rays with wavelengths of more than 240 nm crash into O2 molecules, so they will break down into two single oxygen atoms, these free oxygen atoms then join with other oxygen molecules and form ozone molecules.

                    O₂ + light (l< 240 nm)             O + O

                    O + O₂            O₃

So the concentration of ozone in the atmosphere is not all directly related to pollutant compounds from human activities.

If overall data and analysis are drawn there are other sources of emissions that contribute to air quality in the city of Denpasar. The source of these emissions did not only come from transportation and community movement activities, but there were other stationary sources that had hitherto escaped the government and the public.

There are many factors that affect air quality in an area. In addition to industrial activity, transportation and human movement, air pollution is also greatly affected by weather, wind direction, and sunshine intensity. The imposition of restrictions on the movement of people is not merely a cause of improved air quality.