The Loss of Cl as HCl from Sea Salt Particles by Air Pollutants in the Marine Atmosphere

The loss of Cl as HCl from sea salt particles by air pollutants (NO₃^- and SO₄^2-) in the marine atmosphere was discussed, based on both laboratory experiments and field measurements. In the laboratory experiments, the release of gaseous HCl from sea salt particles was simulated by passing NO₂ or SO₂ through a filter impregnated with sea water. The release of HCl from the filter occurred by the aeration with NO₂ or SO₂, and the concentration of HCl released depended on both the concentration of NO₂ or SO₂ and relative humidity. The generation rates of HCl calcurated from the added amounts of NO₂ and SO₂ were 9% for NO₂ and 18% for SO₂ (Table 1 and 2). The marine aerosol was collected by Andersen samplers during January 13~20 and December 14~20, 1981 in the two remote islands, Hachijo-jima and Chichi-jima in order to investigate the CI loss from sea salt in the marine atmosphere. The calcurated Cl losses from sea salt particles (<2/μm) based on the Cl/Na ratio in sea water (1.8) were 0.21 to 0. 36μg/m³, and 2 to 7% of total particulate marine Cl at the two islands. The Cl loss from sea salt particles smaller than lμm was more than 20%, while that from particles larger than 2μm was negligible (Fig. 4). A linear correlation was observed between measured SO₄^2- concentrations (<2μm) and Cl losses, indicating a 1.1 μmol/m³ Cl loss per 1 μmol/m³ SO₄^2- (Fig. 5). The HCl concentrations estimated from the Cl losses (5. 9×l0⁻³ to 10×l0⁻³μmol/m³) agreed with the measured HCl concentrations in the marine atomosphere (4. 8×l0⁻³ to 15×l0^-7#x03BC;mol/m³) (Table 5), suggesting that the release salt particles is the main source of gaseous HCl in the marine atomosphere.