Chemical Characteristics, Size Distributions, and Aerosol Liquid Water in Size-Resolved Coastal Urban Aerosols Allied with Distinct Air Masses over Tropical Peninsular India

The present study reports on carbonaceous, water-soluble inorganic and organic components in size-resolved aerosols collected under different polluted air masses over a coastal urban location (Cochin) of tropical India. Results show that a high abundance of carbonaceous, non sea-salt (nss)-SO₄^2–, nss-K⁺, and NH₄⁺ in fine mode (<2 μm) is associated with northeasterly air masses, whereas sea-salts (Na⁺ and Cl^–), NO₃^–, and nss-Ca²⁺ were higher in coarse mode (>2.0 μm) aligned with northwesterly and southwest air masses. Organic carbon (OC) was characterized by a unimodal size distribution with a peak in fine mode during northeasterly and northwesterly air masses, whereas the peak was shifted to the coarse mode during southwest air masses. Elemental carbon (EC) showed unimodal size distribution during southwest air masses while bimodal distribution under northeasterly and northwesterly air masses with a prominent peak in fine mode was shown. NH₄⁺, nss-SO₄^2–, nss-K⁺, and water-soluble OC (WSOC) showed unimodal size distributions with a peak in fine mode, whereas NO₃^–, sea-salts, and dust particles showed unimodal size distributions with a peak in the coarse mode. On the basis of these results together with correlation analysis and specific mass ratios, we emphasize that northeasterly air masses are highly enriched with secondary anthropogenic aerosols whereas primary coarse mode aerosols come from various sources such as sea-salts, dust, and NO_x emissions linked with northwesterly and southwest air masses. The estimated aerosol–liquid–water (ALW) revealed that sea-salts, nitrate, and dust aerosols contribute to ALW in the coarse mode, whereas NH₄⁺, SO₄^2–, and water-soluble organics are significantly important in fine mode aerosols.