No abstract

Due to the COVID-19 pandemic, all countries around the world have imposed nationwide lockdowns to control the spreading of the virus. During the lockdown period, many countries saw a drastic drop in air pollution. In Bangladesh, there were two nationwide lockdowns. The first lockdown was imposed on 26 March–30 May in 2020 and the second lockdown was imposed on 3 April until the study period of 31 May in 2021. This study aimed to analyze the NO2 pollution over Bangladesh during the two periods of lockdown. Tropospheric NO2 column spatial configuration was measured over Bangladesh using Sentinel-5P data. A map of the monthly average concentration of tropospheric NO2 in 2020 and 2021 over Bangladesh was produced using the HARP toolkit and Python. Then, the map was compared with same period Sentinel-5P product’s map for the same period in 2019. It was found that during the first lockdown in Bangladesh between 26 March and 30 May 2020, NO2 concentration drastically decreased in April but increased in May. However, during the second lockdown from 3 April to 31 May in 2021, the NO2 concentration was found to be much higher. Most of the pollution occurred in the Dhaka district. During the second lockdown, the restrictions were much lighter than those during the first one, which impacted the NO2 concentration. This kind of study can be essential for the authorities to look closely at air quality and use sentinel data to improve air quality monitoring in the future.

The present research has evaluated the suitability of river water near industrial area of Dhaka for multi uses by calculating various indices. A considerable variation in the content of physicochemical and toxic elements in the studied river water suggests input of pollution from different sources. Further, excess concentration of Fe, Al and K compared to WHO standard was observed in Turag, Pb, Fe, Al, Cr and K in Buriganga, Cd, Fe, K, Al and Cr in Shitalakhya, Fe, Al and K in Bongshi and As in Dhaleswari river water. Moreover, all the river water is found to be safe for irrigation with respect to pH, TDS, SAR and MR. However, the metal pollution indices PF, PD, PLI and irrigation indices Na% and KI indicates that Buriganga river water is no longer suitable for the use of any purposes. But water of Turag, Shitalakhya and Bangshi River still can be used by controlling the source of pollution through proper treatment of waste or by preventing any further discharge of waste into the river. On the other hand Dhaleswari river water can be used for all purposes. Moreover, from the toxicity distribution pattern, it is seen that Buriganga > Shitalakhya > Bangshi > Turag > Dhaleswari. Therefore, proper management plan is necessary to protect this invaluable resource for multi use.

No abstract