Investigation of the source, morphology, and trace elements associated with atmospheric PM₁₀ and human health risks due to inhalation of carcinogenic elements at Dehradun, an Indo-Himalayan city

To study the physical and chemical properties of atmospheric particulate matter over Dehradun city located along the foothills of the Himalayas, both in situ and satellite-based observations were utilized in the present research. Ambient respirable suspended particles denoted by PM₁₀ (atmospheric particulate matter having an aerodynamic diameter of ≤ 10 µm) was measured during 2016–2017. The morphology and elemental characteristics of PM₁₀ was studied through scanning electron microscopy (SEM) and SEM-energy-dispersive X-ray spectroscopy, respectively. The 24-h mean ± standard deviation of PM₁₀ was observed to be 158.6 ± 33.4 µg/m³, which is more than 2 times the permissible limit of World Health Organization (50 µg/m³). Microscopic analysis revealed particles with irregular, porous, rounded, flaky, chain and branched structures indicating various types such as tar balls, soot, crystalline and biogenic particles. The frequently found particle types were investigated for the atomic percentage contribution, which revealed vehicular exhaust, industrial emission, biomass burning, and crustal/dust re-suspension as the chief source of PM₁₀. To delineate the source and transport pathway of air masses converging over the city, 24-h air mass back trajectories were associated with MODerate resolution Imaging Spectroradiometer derived fire spots, geographical location of cement manufacturing and thermal power plants in the vicinity of monitoring site. Excess cancer risk due to inhalation of Lead particles (mean = 0.159 µg/m³) associated with PM₁₀ was 0.16 × 10⁻⁶, which is well below the safe limit (1 × 10⁻⁶) framed by the United States Environment Protection Agency.