Spectroscopic and chemical compositional analysis of the atmospheric aerosols in urban and rural tropical environment of southern India

Abstract

This study provides a comprehensive characterization of atmospheric aerosols collected from Gadanki (13.5°N, 79.2°E, a rural background) and Hyderabad (17.5°N, 78.6°E, an urban location), marking the first detailed analysis of aerosol particles in these contrasting environments in southern peninsular India. Aerosol particulate matter (PM) samples, spanning different aerodynamic size ranges (10 μm, 2.5 μm, and 1.4 μm), were analyzed spectroscopically to determine the molecular structure of the chemical species. Both organic compounds (hydrocarbons, carbonaceous species, and amines) and inorganic species (ammonium sulfates/nitrates, clay minerals, gypsum, calcium carbonate, kaolinite, and metal-oxygen bonds) were identified. The urban PM exhibited higher carbon content, while rural aerosols showed a greater oxygen ratio, as confirmed by Energy-dispersive X-ray spectroscopy (EDX). Metal ions such as silicon (1.46–13.63 %), aluminium (0.34–5.72 %), sodium (0.61–3.99 %), calcium (0.14–1.5 %), iron (0.08–1.07 %), and zinc (0.06–0.81 %) were attributed to sources including vehicular emissions and wind-blown dust. Scanning Electron Microscopy (SEM) revealed that the particles were irregularly shaped and aggregated. Ultraviolet–visible (UV–Vis) spectroscopy revealed strong UV absorption and high transparency (∼99 %) in the visible range, with optical band gaps of ∼5.6 eV and 5.8 eV for Hyderabad and Gadanki, respectively, indicating their non-conducting nature. This study provides critical insights into the aerosol composition and behavior in tropical urban and rural locations, with important implications for air quality management and climate modeling.