Chemical and Morphological Characterization of Atmospheric Aerosols over the Southern Western Ghats: Impact of Long-Range Anthropogenic Transport on a Sensitive Ecosystem

Continental outflows from Southeast and East Asia significantly influence aerosol distribution over southern peninsular India during the winter period, when northeast air mass dominates over the region, impacting sensitive ecosystems that regulate regional climate and rainfall patterns. To study the composition of atmospheric aerosols and document signatures of anthropogenic influence over background atmospheric environments, PM10 and PM2.5 aerosol samples were collected from the High-Altitude Cloud Physics Observatory (HACPO; 1820 m above MSL) located at Munnar, a hill-station situated on the windward side of the southern Western Ghats. The collected samples were subjected to offline chemical analyses to estimate the different components of aerosols including water-soluble inorganic ions, water-soluble organic carbon (OC) (WSOC), OC, elemental carbon (EC), and light absorption characteristics of water-soluble brown carbon (WS-BrC) as well as morphology and elemental characterization. Results show that NH4+, SO42–, NO3–, K+, and EC, predominantly from anthropogenic sources, contributed to 45% of PM10 mass loading, with WS-BrC chromophores at 365 nm exhibiting increased abundance and enhanced absorbing capacity in winter, confirming the presence of pollutants influenced from northeastern continental transport. The PMF-identified sources showed distinct seasonal variability, with dust and secondary biogenic aerosols dominant in premonsoon and secondary inorganic aerosols and combustion-related sources prevailing in winter. The resolved source profiles exhibited strong similarity with previous regional studies, highlighting a consistent spatial pattern of long-range transported aged anthropogenic emissions across southern-peninsular India during the winter period, under the influence of northeast air-mass. Analysis of the surface morphology and elemental characterization of individual particles reveals that the particles exist in a mixed state, originating from both anthropogenic and natural sources, comprising carbonaceous components, mineral dust, and secondary-formed sulfate and nitrate. The findings from this study underscore the significant presence of anthropogenic aerosols over the pristine region of Western Ghats, comparable to that observed over other regions in peninsular India during the continental outflow period. Understanding the characteristics of these transported aerosols in this tropical hill station, which experiences relatively pristine atmospheric background conditions, can provide valuable insights into their impact on hygroscopic growth and cloud condensation nuclei activity within the existing aerosol system.