Insights on optical absorption and isotopic properties of carbonaceous aerosol in PM_2.5 and PM₁₀ from different emission sources

Area of Science:

• Atmospheric Chemistry
• Environmental Science
• Aerosol Science

Background:

• Carbonaceous aerosols significantly impact air quality and Earth's radiative balance.
• Their optical absorption and isotopic signatures are not fully understood, hindering accurate climate and pollution assessments.
• Primary emission sources like traffic and solid fuel burning contribute substantially to atmospheric aerosol loading.

Purpose of the Study:

• To analyze the optical absorption and isotopic composition of PM$_{10}$ and PM$_{2.5}$ from traffic and solid fuel emission sources.
• To differentiate the contributions of black carbon (BC) and brown carbon (BrC) to light absorption.
• To investigate the influence of particle size and emission source on aerosol optical properties and carbon isotopes.

Main Methods:

• Analysis of optical properties including Angstrom absorption exponent (AAE), BC and BrC contributions, and mass absorption efficiencies (MAE).
• Measurement of carbon isotope ratios (δ$^{13}$C) for different particle sizes and emission types.
• Comparison of aerosol characteristics between traffic-related (e.g., diesel) and solid fuel (e.g., coal, coke) emission sources.

Main Results:

• Solid fuel emissions exhibited higher AAE values and greater BrC contributions compared to traffic emissions.
• Mass absorption efficiencies for BC (MAE$_{BC}$) were higher in PM$_{2.5}$ than PM$_{10}$, with diesel and coal burning showing the highest MAE$_{BC}$.
• Traffic emissions had more enriched carbon isotope ratios (δ$^{13}$C) than solid fuels, and solid fuel combustion's δ$^{13}$C was size-independent.

Conclusions:

• Source-specific characterization of carbonaceous aerosols is crucial for understanding their atmospheric impact.
• Particle size plays a significant role in the mass absorption efficiency of black carbon.
• Distinct optical and isotopic signatures of traffic and solid fuel aerosols are vital for improving air pollution models and climate forcing estimates.