Abstract: During sea-fog field observation programs on Donghai Island in Guangdong, China in March 2010, fog water and aerosol spectrum were obtained. We studied the evolution of sea fog water chemical composition and microphysical properties of aerosol, as well as the influence of dust on them. The number concentration of aerosol was one order of magnitude lower than that in other regions. There was bimodal distribution with two peaks around morning and dusk, and a nadir at afternoon. The distribution of aerosol was unimodal, with peak radius at 0.02-0.1 μm. Number concentration of aerosol on fog day was lower than that on non-fog day, the maximum values focused on 0.05-0.1 μm and 0.1-0.5 μm, respectively. Aerosol number density decreased significantly during the fog cases especially in small particles; however, it recovered to the original level after fog dissipation. The analysis on the effect of dust on fog water and aerosol were carried out to indicate that Ca²⁺ and Mg²⁺ in fog water increased significantly with the broaden of aerosol spectrum, and the aerosol number density of diameter larger than 1 μm was higher than that in other cases. When the influence of dust was over, the aerosol spectrum became narrow along with the decline of number density and low ion concentration.

Key words: sea fog, aerosol, fog water, ion concentration, dust