Observational study of microphysical and chemical characteristics of size-resolved fog in different regional backgrounds in China

• Published in: The Science of the total environment Vol. 950; p. 175329
• Main Authors: Ge, Panyan, Zhang, Yun, Fan, Shuxian, Wang, Yuan, Wu, Haopeng, Wang, Xinyi, Zhang, Sirui
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 10.11.2024
• Subjects: Chemical composition; Droplet size; Liquid water content; Microphysical characteristics; Microphysical characteristics; Chemical composition; Droplet size; Liquid water content
• ISSN: 0048-9697; 1879-1026; 1879-1026
• DOI: 10.1016/j.scitotenv.2024.175329

To investigate the relationship between microphysical and chemical characteristics of size-resolved fog droplets in different regional backgrounds, we conducted observational experiments in urban, mountainous, rainforest, and rural areas of China. Fog water samples across different diameter ranges (4–16 μm, 16–22 μm, and >22 μm) were collected, alongside fog droplet spectra data. Our findings reveal a close relationship between pH value, electrical conductivity (EC), total ion concentration (TIC) of droplets, and droplet sizes, with smaller droplets exhibiting stronger acidity and higher ion concentrations. Significant differences in chemical composition are observed across size ranges and regional backgrounds. Droplet number concentration (N) and liquid water content (LWC) distributions in different regional backgrounds are skewed, with peak diameters of LWC spectra similar to those of N spectra, yet overall spectral distributions varied significantly. Droplet number concentrations are highest in urban area, while large droplets contribute more to overall LWC in mountainous, rainforest, and rural areas. No direct evidence linked LWC or surface area (S) to LWC ratio to water-soluble ion concentrations of size-resolved fog droplets in different regional backgrounds. However, by adjusting the contributions of S and LWC proportions of different-sized droplets to the ion concentration proportions, we find that expanding the LWC proportion to 2.43 times and decreasing the S proportion to 0.2 times for large droplets, while decreasing the LWC ratio to 0.76 times for small droplets, provided a better explanation for the distribution of ion concentrations. This study advances our understanding of the intricate relationship between the microphysical and chemical characteristics of fog, helping to develop more robust and comprehensive models for fog prediction and management. [Display omitted] •Distribution of physical and chemical characteristics of droplets varies significantly in different regional backgrounds.•Smaller droplets exhibit significantly stronger acidity and higher ion concentration.•Contribution reasons of liquid water content of droplets in different regional backgrounds are different.•Adjusting the microphysical quantities contribution of size-resolved fog droplets can explain the fog chemical distribution.