Abstract
Atmospheric aerosols were sampled with a high volume impactor/diffusion battery system and the collected fractions analysed for their major water-soluble inorganic constituents. Sulphate, nitrate and chloride showed bimodal distributions; sulphate and nitrate were mainly associated with NH
4
+, having approximately log-normal distributions with modes at 1.0 μm. In unpolluted maritime air, chlorides appeared as salts of sodium and magnesium with average modes at c. 5 μm, whilst in polluted air masses significant concentrations of ammonium chloride sub-μm aerosols were detected. Sodium nitrate and sodium sulphate aerosols having average modes of
c. 3.5 μm were observed in mixed maritime/polluted air masses. The dimensions of these particles indicate formation from absorption of H
2SO
4 and HNO
3 at the surface of marine NaCl particles. The concentration of H
+ was very low, but the possibility of its neutralization by atmospheric ammonia during sampling was ruled out by parallel air sampling using an ‘ammonia denuder’.