Roles of water-soluble aerosol coatings for the enhanced radiative absorption of black carbon over south asia and the northern indian ocean

Nair, HRCR and Budhavant, K and Manoj, MR and Kirillova, EN and Satheesh, SK and Gustafsson, � (2024) Roles of water-soluble aerosol coatings for the enhanced radiative absorption of black carbon over south asia and the northern indian ocean. In: Science of the Total Environment, 926 .

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Abstract

Black Carbon (BC), formed by incomplete combustion, absorbs solar radiation and heats the atmosphere. We investigated the enhancement in optical absorption of BC due to coatings of water-soluble (WS) species in the polluted South Asian atmosphere. The BC Mass Absorption Cross-section (MAC; 678 nm) was estimated before and after removal of the WS components. Wintertime samples were collected from three South Asian receptor observatories intercepting large-footprint outflow: Bangladesh Climate Observatory Bhola (BCOB; integrating outflow of the Indo-Gangetic Plain), Maldives Climate Observatories at Hanimaadhoo (MCOH) and at Gan (MCOG), both reflecting outflow from the South Asian region. The ambient MAC observed at BCOB, MCOH and MCOG were 4.2 ± 1.4, 7.9 ± 1.9 and 7.1 ± 1.5 m2 g�1, respectively. The average enhancement of the BC MAC due to WS coatings (i.e., ws-EMAC) was identical at all three sites (1.6 ± 0.5) indicating that the anthropogenic aerosols had already evolved to a fully coated morphology at BCOB and/or that subsequent aging involved two compensating evolution processes of the coating. Inspecting the key coating component sulfate; the sulfate-to-BC ratio increased threefold when transitioning from BCOB to MCOH and by about 1.5 times from BCOB to MCOG. Conversely, both WS organic carbon (WSOC)/BC and water-insoluble OC (WIOC)/BC ratios declined with distance: WSOC/BC diminished by 84 from BCOB to MCOH and by 80 from BCOB to MCOG, while WIOC/BC dropped by about 63 and 59 , respectively. Such declines in WSOC and WIOC reflect a combination of photochemical oxidation and more efficient washout of OC compared to BC. The observed changes in the SO42�/BC and WSOC/BC ratios across South Asia highlight the significant impact of aerosol composition on the optical properties of Black Carbon (BC). These findings emphasize the need for detailed studies on aerosol composition to improve climate models and develop effective strategies for reducing the impact of anthropogenic aerosols on the climate. © 2024 The Authors

Item Type:	Journal Article
Publication:	Science of the Total Environment
Publisher:	Elsevier B.V.
Additional Information:	The copyright for this article belongs to authors.
Keywords:	Atmospheric aerosols; Climate models; Coatings; Light absorption; Observatories; Optical properties; Organic carbon; Water absorption, Absorption enhancement; Black carbon; Carbon ratio; Climate warming; Maldives; Mass absorption; Mass absorption enhancement; Water-soluble organic carbon; Watersoluble, Sulfur compounds, ammonia; black carbon; calcium; ground water; magnesium; organic carbon; potassium; sodium; sulfate; water; organic carbon; water, absorption; aerosol; black carbon; combustion; global warming; organic carbon; radiative forcing, absorption; aerosol; aquatic environment; Article; climate change; climate model; climate warming; controlled study; cyanobacterium; cycling; energy dispersive X ray spectroscopy; flow rate; geographic distribution; Indian Ocean; mass spectrometry; nonhuman; particulate matter; quality control; remote sensing; seasonal variation; solar radiation; South Asia; spatial analysis; warming; absorption; aging; article; atmosphere; Bangladesh; climate; combustion; Indian Ocean; Maldives; pharmaceutics; photooxidation; South Asia; South Asian, Indian Ocean; Indian Ocean (North); South Asia
Department/Centre:	Division of Mechanical Sciences > Divecha Centre for Climate Change
Date Deposited:	20 May 2024 11:53
Last Modified:	20 May 2024 11:53
URI:	https://eprints.iisc.ac.in/id/eprint/84759

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