Optical properties of Asian mineral dust suspended in seawater

Abstract

The spectral optical properties of Asian mineral dust suspended in seawater exhibit significant variability associated with the origin (and, hence, the chemistry and mineralogy) and particle size distribution of the samples. The measurements of dust samples from different locations show that the mass-specific absorption coefficient of particles, ap*, at a wavelength of light λ = 440 nm, varies from about 0.028 m2 g-1 for the soil dust from Chinese desert near Dunhuang to 0.15 m2 g-1 for the soil dust of volcanic origin in Cheju Island (South Korea). At λ = 400 nm, this range is 0.05-0.23 m 2 g-1. The aerosol sample collected in the Sea of Japan during a massive dust storm in East Asia shows ap*(λ) > 0.1 m2 g-1 for λ < 425 nm. The mass-specific scattering coefficient, bp*(λ), ranges from about 0.8 to 1.5 m2 g-1 at blue and green wavelengths for the samples examined. The single scattering albedo, ωo, increases with wavelength. For λ > 400 nm, ωo was >0.78 for the sample from Cheju Island and >0.9 for other samples. In the near-infrared region (750-850 nm), where absorption by dust particles is small or undetectable, ωo was close to 1.