Dr Abhijit Chatterjee delivering the lecture
The Millennium Institute of Energy & Environment Management (MIEEM), a Kolkata-based NGO joined hands with the CSIR-Central Glass & Ceramic Research Institute (CGCRI), Kolkata, to organise a lecture as a part of its monthly lecture programme on 13 March 2020 within CGCRI premises. The lecture titled “Role of Sundarban Mangrove Ecosystem: The Saviour of Kolkata from Atmospheric Aerosol Pollution” was delivered by Dr Abhijit Chatterjee, Associate Professor, Environmental Sciences Section, Bose Institute, Kolkata within the CGCRI premises.
Dr Chatterjee emphasised on how aerosols, which are suspended particulate matter of different chemical compositions with size varying from few nanometres to several micrometres, affect the human health and climate. The speaker distinguished between direct and indirect effects of aerosol on radiation from sunlight. While on direct impact, sunlight either gets scattered by reflection or refraction resulting in cooling or gets absorbed causing warming, in the indirect impact, cooling takes place due to increased cloud lifetime and albedo.
Dr Chatterjee talked about the concept of ‘Blue Carbon’ that was first declared in 2009 in the United Nations Climate Change Conference at the Conference of Parties 15(COP15) in Copenhagen. Blue carbon refers to CO2 removed from the atmosphere and stored as organic carbon within the sediments as well as plants mostly in the coastal ecosystems. Twenty per cent of the countries in the Paris Agreement, India included, in 2016 pledged to use blue carbon in Nationally Determined Contributions (NDC). He emphasised on the importance of blue carbon as mangroves are among the most carbon-rich forests in the tropics.
Dr Chatterjee informed that aerosols generated by burning of agricultural wastes in the south Indian states along the Eastern Ghats are driven by winds over the Bay of Bengal and travel a long distance to rush towards Kolkata through the Sundarban forest with the onset of summer. Shifting cultivation in Odissa and Chhattisgarh and the accompanied forest clearing and burning leads to emission of SO2 and NO2, VOCs, PAHs, ultrafine aerosols and black carbon called soot.
Presence of high amount of organic acids contributed by mangroves over the Sundarbans’ atmosphere along with high amount of ultrafine soot particles from the Eastern Ghats biomass burning increases the size of soot particles. Cloud droplets scavenge various metals, fly-ash species, sulphur compounds, soot particles, dust particles, etc. The species scavenged within clouds absorb solar radiation and warms the atmosphere of the cloud. The water gets evaporated and cloud burns.
Dr K. Muraleedaran, Director, CSIR-CGCRI summed up the lecture session with his concluding remarks, Mr Subhashis Majumdar and Prof Pranab Roy, President and Secretary of MIEEM also spoke on the occasion.