Chemometric assessment, seasonal variation and source apportionment of air pollutants in Islamabad's industrial area

Abstract

Introduction

Global warming is intensified by atmospheric pollution, with industrial activities significantly contributing to this issue. This study investigates air pollution levels in the industrial area of Islamabad, the capital of Pakistan, a developing South Asian nation grappling with severe air quality threats.

Study area

This study was designed to assess the pollution levels in the air of industrial area of Islamabad, Pakistan

Methodology

Fine (size < 2.5µm: PM_2.5) and coarse (size between 2.5 and 10 µm: PM_2.5–10) particulate matter samples were collected on Polycarbonate air filters for three seasons in 2023. The elemental composition of PM was quantified using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES).

Results

The average PM_2.5 (40.42 µg m⁻³) and PM_2.5–10 (221 µg m⁻³) concentrations exceeded Pakistan Environmental Protection Agency (Pak-EPA) limits (PM_2.5: 35 µg m⁻³; PM_2.5–10: 150 µg m⁻³, respectively). In PM_2.5, Na showed the highest mean concentration (8670 ng m⁻³), As the lowest (40 ng m⁻³); in PM_2.5–10, Ca was highest (5476 ng m⁻³), Zr lowest (28 ng m⁻³). Seasonal variations revealed for PM_2.5–10 Ca peaked at 7800 ng m⁻³ in autumn, with Mg, Si, Fe, and Al fluctuating significantly, while toxic elements As, Pb, Co and Cr decreased from spring to autumn. In PM_2.5, Ca peaked at 7043 ng m⁻³ and Na remained elevated in spring, with crustal and toxic metals concentration decreasing from spring to autumn. Depositional flux was high for Ca and Ba in PM_2.5–10, and Na, Cr, and Cu in PM_2.5. The Enrichment factor and pollution index indicated higher contamination by Cr, Cu, Pb, S, Zn, Ni, As, Li, Mo, Sn, and Ag. Environmental Protection Agency Positive Matrix Factorization (EPA-PMF) identified steel mills, marble processing, e-waste incineration, Industrial dust, battery processing and vehicular emissions as primary sources. National Oceanic and Atmospheric Administration's Hybrid Single-Particle Lagrangian Integrated Trajectory model (NOAA HYSPLIT) confirmed local and transboundary contributions to elevated PM levels.

Conclusion

This study concludes that the air of Islamabad's industrial area has high levels of pollution, dependent upon various sources and mitigation of pollution can be achieved by strict enforcement of regulations and laws.