SHATTERING AND MODIFICATION OF SEA-SALT PARTICLES IN THE MARINE ATMOSPHERE

Sampling of sea-salt particles was carried out over the western Pacific Ocean. The collected particles were studied individually by X-ray spectrometry. Sea-salt particles with radii r greater-than-or-equal-to 0.5 mum show a considerable range in their weight ratios of S/Na and Ca/Na, while Cl/Na ratios remain constant at the seawater value. Moreover, there is a tight correlation between S/Na and Ca/Na. This property is attributable to fractionary recrystallization within evaporating drops. Particles with r < 0.5 mum exhibit a similar trend. However, these particles tend to show smaller Cl/Na ratios and larger S/Na ratios than those with r greater-than-or-equal-to 0.5 mum. Chemical reaction between sea salt and acidic material, where Cl- is replaced by (SO4)2- and (NO3)-, is the most plausible explanation.