The effect of meteorological parameters and aerosol constituents on visibility in urban Hong Kong

A study on the possible atmospheric factors reponsible for visibility reduction in Hong Kong has been carried out using time-matched sets of data on the important meteorological parameters and on the chemical species in aerosol matter over the 1990-1992 period. Careful observations on the correlations as well as rotated principal components obtained from the original and screened (< 80% RH) data sets suggest that (i) visibility is highest in the summer and lowest in the winter halves of the year; (ii) mixing height is the most important meteorological variable and (iii) ammonium-sulphate, nitrate and potassium are the primary chemical species, among those considered;that affect visibility. ft is suggested that sulphates and nitrates of ammonium formed through gas-to-particle conversion reactions, and a fine particulate component containing potassium, possibly from some unknown biomass combustion source(s) are involved in the visibility reduction through catering in the urban Hong Kong atmosphere. However, additional scattering by organics and absorption by elemental carbon from combustion of biofuels, especially automotive (diesel) emission is quit: likely, and needs to be investigated, as is the question of local and foreign contributions of pollutants to visibility reduction. (C) 1998 Elsevier Science Ltd. All rights reserved.