Optical and radiative properties of coated black carbon during hygroscopic growth and retrieval errors of mixing state using single-particle soot photometer--颗粒学报PARTICUOLOGY

Liu, J., Zhou, D., Zhu, C., Han, J., & Yin, B. (2025). Optical and radiative properties of coated black carbon during hygroscopic growth and retrieval errors of mixing state using single-particle soot photometer. Particuology, 97, 183-192. https://doi.org/10.1016/j.partic.2024.12.010

Optical and radiative properties of coated black carbon during hygroscopic growth and retrieval errors of mixing state using single-particle soot photometer

Jia Liu^{a b c *}, Donghui Zhou^{a b c}, Cancan Zhu^{a b c}, Jinbao Han^{a b c}, Bo Yin^{a b c *}

a Non-destructive Testing Laboratory, School of Quality and Technical Supervision, Hebei University, Baoding, 071002, China
b Engineering Research Center of Zero-carbon Energy Buildings and Measurement Techniques, Ministry of Education, Hebei University, Baoding, 071002, China
c Hebei Key Laboratory of Energy Metering and Safety Testing Technology, Hebei University, Baoding, 071002, China

10.1016/j.partic.2024.12.010

Volume 97, February 2025, Pages 183-192

Received 1 September 2024, Revised 16 December 2024, Accepted 19 December 2024, Available online 6 January 2025, Version of Record 15 January 2025.

E-mail: liujia@hbu.edu.cn; 13582211867@163.com

Highlights

• SP2 retrieval errors of BC mixing states at various RHs are numerically studied.

• Retrieved mixing states of coated BC are underestimated at different RHs.

• Radiative forcing enhancements for different BC models are distinct at high RHs.

Abstract

Under environment with various water contents, the variations in the mixing state and particle size of coated black carbon (BC) aerosols cause changes in optical and radiative effects. In this study, fractal models for thinly, partially, and thickly coated BC under six relative humidities (RHs = 0–95%) are constructed and optically simulated at 1064 and 532 nm. Differential scattering cross-sections are selected to retrieve the mixing state (D_p/D_c) of BC to investigate the possible retrieval errors caused by the nonspherical morphology when using the single-particle soot photometer (SP2). Furthermore, the radiative forcing of BC aerosols at different RHs are analyzed. Results showed that the retrieval errors (REs) of D_p/D_c are negative for coated particles with BC volume fraction smaller than 0.10, indicating that the mixing states of coated fractal BC are underestimated during the hygroscopic growth. The partially-coated BC has the best retrieval accuracy of the mixing state, followed by the closed-cell and coated-aggregate model, judging from averaged REs. Radiative forcing enhancements for partially-coated aerosols with different BC volume fractions exponentially increase to opposite values, resulting in a warming or cooling effect. This study helps understand the uncertainties in D_p/D_c of BC aerosols retrieved by SP2 and their radiative forcing at different RHs.

Graphical abstract

Keywords

BC aerosol; Hygroscopic growth; SP2; Mixing state; Radiative forcing

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