This study was conducted during high-pollution days, designated as Event I (PM2.5: ≥ 300 µg m−3), and during moderate-pollution days (Events II; PM2.5: ≤ 100 µg m−3) to understand the dynamic and toxic nature of submicron (PM1) and fine particles (PM2.5). Average PM1 and PM2.5 concentrations were 259.50 μg m−3 and 307.20 μg m−3, respectively, for Event I. These values declined to 69.25 μg m−3 and 103.58 μg m−3 during Event II for PM1 and PM2.5, respectively. This reduction in PM concentration was attributed to a significant decrease in the primary source emissions, regional weather variability and atmospheric chemical processes. Chemical composition such organic carbon (OC) and elemental carbon (EC), inorganic species (SO42−, NO3−, NH4+, Cl−) were observed higher in Event I compared to Event II. The secondary organic carbon (SOC) fraction was elevated during Event I in PM2.5, accompanied by higher organic pollutants, which are attributed to enhanced primary emissions. Morphological analysis revealed diverse particle shapes, including irregular, fibrous, rod-like, elongated, spherical, and flattened forms, characterized by variations in aspect ratio, roundness, form factor, and circularity. Based on morphology and elemental mapping, we observed carbonates, quartz, sulfates, metal oxides, and fluoride particles. Furthermore, sulfate compounds appeared as K-S–O (high density) in Event I and as Na-S–O (mirabilite, low density) in Event II. The oxidative potential (OPv and OPm) showed higher levels in Event I. However, OPm exhibited a slightly increase in PM2.5 during Event II also, due to the change in particle characteristics during atmospheric chemical processes. The total excess cancer risks (ECRs) were higher (PM1:1.18 × 10–3 and PM2.5: 8.48 × 10–4) for Event I and exhibited lower ECRs (PM1: 8.98 × 10–4 and PM2.5: 3.46 × 10–4) for Event II. Among trace metals, Chromium (Cr), Nickel (Ni), and Cobalt (Co) exhibited elevated ECR, while Lead (Pb) and Cadmium (Cd) exhibited lower ECR. Inhalation exposure was also higher during Event I compared to Event II; however, OPm contributed significantly exposure to both Events.

Unveiling air toxicity in urban environment through morphology and chemical reactivity of aerosol: insights from Delhi, India

期刊论文
发表日期：

2026年1月21日

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Atar Singh Pipal,
Molla Nageswar Rao,
Arkabanee Mukherjee,
Sandip S. Nivdange,
Chaitri Roy,
Abhilash S. Panicker,
Sachin D. Ghude

摘要

This study was conducted during high-pollution days, designated as Event I (PM_2.5: ≥ 300 µg m⁻³), and during moderate-pollution days (Events II; PM_2.5: ≤ 100 µg m⁻³) to understand the dynamic and toxic nature of submicron (PM₁) and fine particles (PM_2.5). Average PM₁ and PM_2.5 concentrations were 259.50 μg m⁻³ and 307.20 μg m⁻³, respectively, for Event I. These values declined to 69.25 μg m⁻³ and 103.58 μg m⁻³ during Event II for PM₁ and PM_2.5, respectively. This reduction in PM concentration was attributed to a significant decrease in the primary source emissions, regional weather variability and atmospheric chemical processes. Chemical composition such organic carbon (OC) and elemental carbon (EC), inorganic species (SO₄²⁻, NO₃⁻, NH₄⁺, Cl⁻) were observed higher in Event I compared to Event II. The secondary organic carbon (SOC) fraction was elevated during Event I in PM_2.5, accompanied by higher organic pollutants, which are attributed to enhanced primary emissions. Morphological analysis revealed diverse particle shapes, including irregular, fibrous, rod-like, elongated, spherical, and flattened forms, characterized by variations in aspect ratio, roundness, form factor, and circularity. Based on morphology and elemental mapping, we observed carbonates, quartz, sulfates, metal oxides, and fluoride particles. Furthermore, sulfate compounds appeared as K-S–O (high density) in Event I and as Na-S–O (mirabilite, low density) in Event II. The oxidative potential (OPv and OPm) showed higher levels in Event I. However, OPm exhibited a slightly increase in PM_2.5 during Event II also, due to the change in particle characteristics during atmospheric chemical processes. The total excess cancer risks (ECRs) were higher (PM₁:1.18 × 10^–3 and PM_2.5: 8.48 × 10^–4) for Event I and exhibited lower ECRs (PM₁: 8.98 × 10^–4 and PM_2.5: 3.46 × 10^–4) for Event II. Among trace metals, Chromium (Cr), Nickel (Ni), and Cobalt (Co) exhibited elevated ECR, while Lead (Pb) and Cadmium (Cd) exhibited lower ECR. Inhalation exposure was also higher during Event I compared to Event II; however, OPm contributed significantly exposure to both Events.