Investigation of Winter-time Background Air Quality Index of Indo-Gangetic Plain over Sundarban Mangrove Reserve Forest in India

Abstract:

It is well known that deterioration of winter-time air quality due to strong emission of pollutants aggravates human health by increasing risk of cardiovascular morbidity and mortality. Major pollutants like PM2.5, Sulphur-di-oxide, carbon monoxide, nitrogen dioxide and ozone were measured at Kalas Island, the southern-most delta island of Sundarban mangrove reserve forest, which is downwind of the Indo-Gangetic Plain (IGP) in India. Having no local anthropogenic sources of pollutions, Sundarban reserve mangrove forest becomes unique location for investigations of background air quality index (AQI) of IGP. The minimum AQI is found to be ‘moderate’ of value about 180, which can be considered as background AQI of IGP. However, there is significant variation of background AQI due to significant variation of environmental conditions because of venting out the pollution over Sundarban from IGP to the Bay of Bengal. Background AQI becomes ‘poor’ during foggy morning when the surface reaching solar radiation reduced about 50%, nicely identify the fog by Indian Kalpana satellite. It could be due to accumulation of pollutants over measurement site in foggy environment. It is noticed during measurement period at Sundarban, surface solar radiation reduces about 35% on a day when a dense fog is noticed over central IGP but not present over measurement site. This is due to the presence of winter-time haze over Sundarban coming out from foggy region of central IGP, nicely captured the haze by MODIS sensor and considered the day as hazy day. On hazy day, AQI over Sundarban becomes ‘very poor’ due to presence of winter haze containing high concentration of black carbon particles coming out from the foggy region of central IGP. Such a very poor condition of breathing air causes serious deterioration of health condition for respiratory patients over urban regions in IGP.