Shattering and modification of sea‐salt particles in the marine atmosphere

Abstract

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 ≥ 0.5 μm 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 μm exhibit a similar trend. However, these particles tend to show smaller Cl/Na ratios and larger S/Na ratios than those with r ≥ 0.5 μm. Chemical reaction between sea salt and acidic material, where Cl− is replaced by (SO4)2− and (NO3)−, is the most plausible explanation.

Biological Impacts on Carbon Speciation and Morphology of Sea Spray Aerosol

“…In addition, these particles exhibit a high degree of fractionary recrystallization and particle shattering (section 3.3.2), as indicated by externally mixed organic-rich spines and cubic inorganic salts. 36 Shattering and recrystallization likely occurred during sampling and analysis at low relative humidity. As the blooms progressed, a variety of carboxylic acids with varying carbon chain length and number of carboxylic acid groups were identified, as determined by electrospray ionization high-resolution mass spectrometry (ESI-HR-MS) by Cochran et al 37 Varying carboxylic acids have different surface activities and affinities for inorganic ions.…”

“…The lack of mixing between these phases is characteristic of the high degree of fractionary recrystallization and shattering as well as the increased surfactant behavior of organics under bloom conditions. 36 Fractionary recrystallization was exclusive to only the first bloom and for the size range 1.8−3.2 μm, where an abundance of these calcium/organic spines were observed. Mouri and Okada 36 reported similar calcium sulfate spines resulting from fractionary recrystallization when the Na/Ca or Na/S ratio is high.…”

“…36 Fractionary recrystallization was exclusive to only the first bloom and for the size range 1.8−3.2 μm, where an abundance of these calcium/organic spines were observed. Mouri and Okada 36 reported similar calcium sulfate spines resulting from fractionary recrystallization when the Na/Ca or Na/S ratio is high. The resulting spines and shattering occur from separate recrystallization of NaCl and CaSO 4 due to solubility differences, which results in loosely attached crystals of NaCl and CaSO 4 that readily shatter.…”

“…While prebloom and second bloom conditions primarily produced intact sea salt− organic particles, particles produced during the first bloom exhibited a high degree of fractionary recrystallization and particle shattering. 36 As a result, there were many particles with sizes of <3 μm during the first bloom, and these particles tended to be rich in either calcium, carboxylic acid-containing organics, or both. A bulk OVF (mass-weighted, including all particles) was calculated to be 0.25 ± 0.21 for large (1.8−3.2 μm) particles sampled during the first bloom.…”

Ocean–Atmosphere Interactions of Particles

“…The release of reactive chloride is considered to be an important intermediate in the oxidation reactions associated with the removal of light hydrocarbons and ozone in the marine atmosphere (Singh and Kasting 1988;Vogt et al 1996). The magnitude of Cl-depletion of marine aerosols has been demonstrated to usually increase with decreasing sea salt particle size (Mouri and Okada 1993;Kerminen et al 1998;Yao et al 2003;Hsu et al 2007). This reaction produces sea salt particles coated with sulphate and nitrate over Asian and Pacific areas (Matsumoto et al 2004;Matsuki et al 2005;Yang et al 2009) and in the Mediterranean region (Tursic et al 2006).…”