This study investigates how organics contribute to initial particle growth in the 3–10 nm size range. Through laboratory experiments, it was found that sulfuric acid dominates the growth of smaller particles, while organics play an increasingly important role as particle size increases. Elevated humidity also significantly enhances the contribution of organics. These findings further our understanding of new particle formation and subsequent growth.

Black carbon (BC) is a light-absorbing particle that contributes to atmospheric warming, but its radiative impact remains highly uncertain. We conducted field measurements in Hangzhou, China, to examine how mass ratio (coating-to-BC) and morphology influence light absorption. Our results show that widely used optical models overestimate absorption especially under clean conditions. A new morphology-based method improves model accuracy and reduces this uncertainty.

This study investigates the size-resolved effective density (ρ_eff) of aerosol particles in Hangzhou using a tandem aerodynamic aerosol classifier and scanning mobility particle sizer system. The ρ_eff values ranged from 1.47 to 1.63 g cm^-3, increasing with particle diameter. The relationship between ρ_eff and the particle diameter varies due to differences in the chemical composition of the particles. A new method to derive the size-resolved chemical composition of particles from ρ_eff is proposed.

Mobile CH₄ measurements were conducted at a wastewater treatment plant in Hangzhou in the summer and winter of 2023. A multi-source Gaussian plume model, combined with a genetic algorithm inversion framework, was used to locate major CH₄ sources at the plant and quantify emissions. Results indicate that the summer CH₄ emissions (603.33 ± 152.66 t a^-1) were 2.8 times as high as inventory values, and winter values (418.95 ± 187.59 t a^-1) were twice as high. The main sources were the screen and primary clarifier.

An aerosol optical tweezer (AOT) Raman spectroscopy system is developed to capture a single aerosol droplet for phase transition monitoring and morphology studies. Rapid droplet capture is achieved and accurate droplet size and refractive index are retrieved. Results indicate that mixed inorganic/organic droplets are more inclined to form core–shell morphology when RH decreases. The phase transitions of secondary mixed organic aerosol/inorganic droplets vary with their precursors.