Carbonaceous and water-soluble inorganic aerosols over a semi-arid location in north west India: Seasonal variations and source characteristics

Prashant Hegde,B.M Vyas,A.R Aswini,S Aryasree,Prabha R Nair

doi:10.1016/j.jaridenv.2019.104018

Prashant Hegde, B.M Vyas + Show 3 more

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https://doi.org/10.1016/j.jaridenv.2019.104018

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Abstract

This paper presents the seasonal features of major carbonaceous components in aerosols, their source characteristics and the role of meteorology in influencing the chemical characteristics of aerosols at a semi-arid location Udaipur (24.5°N; 73.6°E), India, based on the analysis of PM10 samples (N = 128) collected during 2010–14. The samples were analysed for OC (organic carbon), EC (elemental carbon), CC (carbonate carbon), WSOC (water-soluble OC), WSTN (water-soluble total nitrogen) and water-soluble inorganic ions. Primary and secondary OC (POC and SOC), water-insoluble OC (WIOC) and water-soluble organic nitrogen (WSON) were also estimated. The carbonaceous aerosols (TC) contributed to ~23% of PM10 loading. Both EC and OC mass loading showed high values during dry period (October to May) (OC = 26 ± 14 μg m−3, EC = 3.2 ± 2.2 μg m−3 with the PM10 mass loading of 140 ± 52 μg m−3) compared to wet period (June to September) (OC = 16 ± 10 μg m−3, EC = 1.4 ± 0.8 μg m−3 with the PM10 mass loading of 84 ± 43 μg m−3). While the crustal species, biomass tracers and anthropogenic species dominated during dry period, the sea salt species (Na+, Cl−, ss-SO4, ss-Mg, ss-Ca, ss-K) were comparatively higher in wet period. OC was found to be predominantly water-insoluble and secondary in nature. Local anthropogenic/natural emissions and marine transported aerosols (by south-westerlies) contributed during wet period, while dry period is influenced by transported anthropogenic aerosols from IGP and northern India (by north/north-easterlies) along with mineral aerosols from desert regions (by westerlies). Monthly average contribution of total carbonaceous aerosols (TCA = OM (organic matter) +EC + CC) varied from 20 to 42%, over a year while the water-soluble ionic fraction varied from 16 to 36% of the PM10 mass. The un-analysed part which is mostly mineral dust contributed 39–55%.

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