Chlorine Deficiency in Coastal Aerosols

Abstract

The gaseous chlorine in the atmosphere and the water-soluble material of the aerosols collected at Owase in October 1975 were analyzed. The concentration of gaseous chlorine was found to be 3.1 µg/m3. It is found that the Cl/Na ratios inn the aerosols were always lower than that of seawater. Their mean value was 0.67. On the basis of this value, it was estimated that the amount of Cl deficiency in the aerosols was 2.1 µg/m3 which is 61% of the theoretical Cl content of sea-salt particles. The amount of Cl deficiency corresponded to the concentration of {2(So4)ex.+NO3-NH4} in the aerosols. Thus, it is suggested that the Cl deficiency is mainly due to the chemical reaction between the sea-salt particles and H2SO4 and HNO3 originated from the gaseous materials such as SO2 and No2, in the atmosphere. According to the relationship between the amount of Cl deficiency in the aerosols and the concentration of gaseous chlorine in the atmosphere, it was considered that a considerable amount of the gaseous chlorine in the coastal atmosphere at Owase was released from sea-salt particles.

Aerosol characteristics at Mauna Loa Observatory, Hawaii, after east Asian dust storm episodes

“…The first Cl peak occurs in late evening April 24 near the temperature minimum and corresponds to gentle westerly winds and S and Fe, but not CNC, peaks. This Cl is more difficult to explain, but one possible hypothesis is that it is related to a lesser acidity of the air mass inhibiting gaseous Cl evolution from aerosols as may occur by, for example, reaction with H2SO4 and HNO3 [Okada et al, 1978]. The S aerosol concentration would not be sensitive to such conditions but would exist to a greater extent as a salt, such as (NH4)2SO4, and would still track the Fe concentration as it typically does during much of this sampling period.…”

The Effect of Continental Air Mass on the Modification of Individual Sea-Salt Particles Collected over the Coast and the Open Sea

“…The modification of sea-salt particles has been of interest in connection with the origin of atmospheric gaseous chlorine in the field of air chemistry (e.g., Oddie, 1959;Junge, 1956Junge, , 1963Martens et al, 1973;van de Vate et al, 1978;Okada et al, 1978Okada et al, , 1989. Junge (1963) reviewed that the Cl/Na ratios in rainwater were always smaller than that in seawater.…”

Factors controlling sea salt modification and dry deposition of nonsea‐salt components to the ocean

“…Because the NO 3 − /Na + concentration ratio in surface seawater is <0.001 [ James , 2005], high NO 3 − /Na + ratios (0.01–1.03) observed in coarse particles suggest that most of the NO 3 − in coarse particles was added from the atmosphere and derived from nonsea‐salt compounds [ Parungo et al , 1986; Mamane and Mehler , 1987; Pósfai et al , 1995; Hara et al , 1999; Zhuang et al , 1999; Pryor and Sørensen , 2000]. Similarly, absorption and subsequent oxidation of SO 2 injects additional SO 4 2− to coarse SSA particles as nss‐SO 4 2− [ Okada et al , 1978; Parungo et al , 1986; McInnes et al , 1994; Pósfai et al , 1995; Buseck and Pósfai , 1999]. Although the HNO 3 concentration in the atmosphere was almost the same or lower than SO 2 , the NO 3 − concentration found in coarse particles was more than four times higher than that of nss‐SO 4 2− in most samples (Figure 4).…”

“…Sea salt aerosol particles derived from the ocean constitute the major component of the total aerosol mass in the lower atmosphere [ Andreae , 1995]. Sea salt aerosol particles (SSA particles) are often modified by various acidic gases such as HNO 3 and SO 2 [ Okada et al , 1978; Parungo et al , 1986; Mamane and Mehler , 1987; McInnes et al , 1994; Pósfai et al , 1995; Pio and Lopes , 1998; Buseck and Pósfai , 1999; Hara et al , 1999; Zhuang et al , 1999; Spokes et al , 2000; Rossi , 2003]. Because supermicrometer SSA particles are quickly deposited onto the Earth's surface or are returned to the ocean, once they are absorbed and react with acidic gases, they carry nonsea‐salt (nss) components, such as NO 3 − and nss‐SO 4 2− , from the atmosphere to Earth's surface.…”