Continental outflow of anthropogenic aerosols over Arabian Sea and Indian Ocean during wintertime: ICARB-2018 campaign

A R Aswini; Prashant Hegde; S Aryasree; Imran A Girach; Prabha R Nair

doi:10.1016/j.scitotenv.2019.135214

Continental outflow of anthropogenic aerosols over Arabian Sea and Indian Ocean during wintertime: ICARB-2018 campaign

Sci Total Environ. 2020 Apr 10:712:135214. doi: 10.1016/j.scitotenv.2019.135214. Epub 2019 Nov 23.

Authors

A R Aswini¹, Prashant Hegde², S Aryasree³, Imran A Girach⁴, Prabha R Nair⁴

Affiliations

¹ Space Physics Laboratory, Vikram Sarabhai Space Centre, Thiruvananthapuram, India; Cochin University of Science and Technology, Cochin, India.
² Space Physics Laboratory, Vikram Sarabhai Space Centre, Thiruvananthapuram, India. Electronic address: prashant_hegde@vssc.gov.in.
³ Institute for applied Geosciences, Technical University Darmstadt, Darmstadt, Germany.
⁴ Space Physics Laboratory, Vikram Sarabhai Space Centre, Thiruvananthapuram, India.

PMID: 31836221
DOI: 10.1016/j.scitotenv.2019.135214

Abstract

Chemical characterisation of atmospheric aerosols over Arabian Sea (AS) and Indian Ocean (IO) have been carried out during the winter period (January to February 2018) as part of the Integrated Campaign for Aerosols, gases and Radiation Budget (ICARB-2018). Mass concentrations of organic carbon (OC), elemental carbon (EC), water soluble and insoluble OC (WSOC, WIOC), primary and secondary OC (POC, SOC), water-soluble inorganic ions and trace metals have been estimated with a view to identify and quantify the major anthropogenic pollutants affecting the oceanic environments. Aerosol mass loading was found to exhibit strong spatial heterogeneity (varying from 13 to 84 μg m^-3), significantly modulated by the origin of air-mass trajectories. Chemical analysis of aerosols revealed the presence of an intense pollution plume over south-eastern coastal Arabian Sea, near to south-west Indian peninsula (extending from ~ 12°N to 0° at 75°E) with a strong latitudinal gradient (~3 μg m^-3/deg. from north to south) dominated by anthropogenic species contributing as high as 73% (38% nss-SO₄²^-, 24.2% carbonaceous aerosols (21% Organic Matter, 3.2% EC) and 10% NH₄⁺). Anthropogenic signature over oceanic environment was also evident from the dominance and high enrichment of elements like Zn, Cu, Mn and Pb in trace metals. Long-range transport of air-masses originating from Indo Gangetic Plains and its outflow regions in Bay of Bengal, has been seen over Arabian Sea during winter, that imparted such strong anthropogenic signatures over this oceanic environment. Comparison with previous cruise studies conducted nearly two decades ago shows a more than two-fold increase in the concentration of nss-SO₄²^-, over the continental outflow region in Arabian Sea.

Keywords: Anthropogenic; Arabian sea; Chemical composition; Marine aerosol; Sources.