A Framework for Quantifying the Size and Fractal Dimension of Compacting Soot Particles

Area of Science:

• Atmospheric Science
• Aerosol Science
• Climate Modeling

Background:

• Black carbon (BC) is a major atmospheric aerosol with significant warming effects.
• BC particles are emitted as fractal aggregates and undergo compaction upon coating.
• Accurate representation of BC size and shape evolution is crucial for climate models but computationally challenging.

Purpose of the Study:

• To develop a framework for predicting the size and shape of black carbon particles during compaction.
• To link BC particle restructuring to the coating volume ratio, a parameter tracked in atmospheric models.
• To improve the representation of BC's atmospheric lifetime and radiative properties in climate simulations.

Main Methods:

• Combined laboratory measurements of BC compaction with detailed restructuring models.
• Developed a predictive framework based on the coating volume ratio.
• Validated predictions against experimental data for mobility diameter and fractal dimension.

Main Results:

• The framework accurately predicts the mobility diameter and fractal dimension of BC particles and their cores.
• Root-mean-squared errors were below 6.8% for mobility diameter and 4.3% for fractal dimension.
• The model captures BC particle evolution across a range of coating volumes.

Conclusions:

• The proposed framework enables a more complete representation of evolving BC size and shape.
• This improves the accuracy of climate models at a low computational cost.
• Facilitates better understanding of black carbon's role in climate.