In-depth characterization of particulate matter in a highly polluted urban environment at the foothills of Himalaya-Karakorum Region

Abstract

In recent years, the rising levels of atmospheric particulate matter (PM) have an impact on the earth's system, leading to undesirable consequences on various aspects like human health, visibility, and climate. The present work is carried out over an insufficiently studied but polluted urban area of Peshawar, which lies at the foothills of the famous Himalaya and Karakorum area, Northern Pakistan. The particulate matter with an aerodynamic diameter of less than 10 µm, i.e., PM₁₀ are collected and analyzed for mineralogical, morphological, and chemical properties. Diverse techniques were used to examine the PM₁₀ samples, for instance, Fourier transform infrared spectroscopy, x-ray diffraction, and scanning electron microscopy along with energy-dispersive x-ray spectroscopy, proton-induced x-ray emission, and an OC/EC carbon analyzer. The 24 h average PM₁₀ mass concentration along with standard deviation was investigated to be 586.83 ± 217.70 µg/m³, which was around 13 times greater than the permissible limit of the world health organization (45 µg/m³) and 4 times the Pakistan national environmental quality standards for ambient PM₁₀ (150 µg/m³). Minerals such as crystalline silicate, carbonate, asbestiform minerals, sulfate, and clay minerals were found using FTIR and XRD investigations. Microscopic examination revealed particles of various shapes, including angular, flaky, rod-like, crystalline, irregular, rounded, porous, chain, spherical, and agglomeration structures. This proved that the particles had geogenic, anthropogenic, and biological origins. The average value of organic carbon, elemental carbon, and total carbon is found to be 91.56 ± 43.17, 6.72 ± 1.99, and 102.41 ± 44.90 µg/m³, respectively. Water-soluble ions K⁺ and OC show a substantial association (R = 0.71). Prominent sources identified using Principle component analysis (PCA) are anthropogenic, crustal, industrial, and electronic combustion. This research paper identified the potential sources of PM₁₀, which are vital for preparing an air quality management plan in the urban environment of Peshawar.

Keywords: Elemental carbon; Organic carbon; Peshawar; Principle component analysis, Air quality analysis; Total carbon.