Executive Summary
Comprehensive analysis of PM2.5 chemical composition using X-ray Fluorescence (XRF) and Ion Chromatography (IC) methods reveals distinct seasonal patterns and source contributions in atmospheric aerosols.
The PM2.5 samples were collected during two field campaigns in the dry season (June-September 2024) and in the wet season (December 2024-March 2025).
Key Findings
- Secondary sulfate aerosols dominate during dry season
- Sea salt influence more pronounced in wet season
- Strong correlation between XRF and IC methods validates cross-method consistency
- Non-sea-salt sulfate contributes >95% of total sulfate
Methodology
XRF Analysis
X-ray Fluorescence spectroscopy for elemental composition determination of PM2.5 samples.
IC Analysis
Ion Chromatography for water-soluble ionic species measurement in atmospheric particles.
PCA Analysis
Principal Component Analysis to identify source contributions and chemical associations.
Seasonal Comparison
Statistical analysis of dry vs wet season variations using Mann-Whitney U test.
XRF Principal Component Analysis
Variance explained by each principal component
Component Loadings
Principal Component Interpretations
IC Principal Component Analysis
Variance explained by each principal component
Component Loadings
Principal Component Interpretations
Seasonal Comparison
Statistical Significance Legend
Ionic Balance
Cation vs Anion Equivalents
Slight excess of cations over anions on average
SO₄²⁻/NO₃⁻ Ratio Distribution
Distribution of SO₄²⁻/NO₃⁻ ratios, indicating the prevalence of different atmospheric conditions or sources. Dominance of sulfur-based secondary aerosol from SO₂ emissions.
NH₄⁺ Neutralization Ratio Distribution
Distribution of NH₄⁺ neutralization ratios. Under-neutralization indicates some sulfate exists as acidic species.
Non-Sea-Salt Sulfate (nss-SO₄²⁻)
Example:
Total SO₄²⁻: 3.11 μg/m³
nss-SO₄²⁻: 3.07 μg/m³
Anthropogenic SO₂ origin dominates (Contribution >95%).
Cross-Method Validation
Consistency assessment between XRF and IC analytical methods
XRF-IC Sulfur Method Comparison
XRF-IC Potassium Method Comparison
Validation Summary
Sulfur Consistency
Strong correlation between XRF S and IC SO₄²⁻ validates measurement accuracy across both analytical platforms.
Potassium Cross-Reference
Consistent signal between XRF K and IC K⁺ confirms reliable detection of crustal and biomass burning sources.
Crustal Elements
Crustal elements show consistent patterns, especially evident in PC4 of IC PCA analysis.