Source apportionment of visibility degradation problems in Brisbane (Australia) using the multiple linear regression techniques

Different aspects of visibility degradation problems in Brisbane were inves tigated through concurrent visibility monitoring and aerosol sampling progr ams carried out in 1995. The relationship between the light extinction coef ficients and aerosol mass/composition was derived by using multiple linear regression techniques. The visibility properties at different sites in Bris bane were found to be correlated with each other on a daily basis, but not correlated with each other hour by hour. The cause of scattering of light b y moisture (b(sw)) was due to sulphate particles which shift to a larger si ze under high-humidity conditions. The scattering of light by particulate m atter (b(sp)) was found to be highly correlated with the mass of fine aeros ols, in particular the mass of fine soot, sulphate and non-soil K. For the period studied, on average, the total light extinction coefficient (b(ext)) at five sites in Brisbane was 0.65 x 10(-4) m(-1), considerably smaller th an those values found in other Australian and overseas cities. On average, the major component of b(ext) is b(sp) (49 % of b(ext)), followed by b(ap) (the absorption of light, mainly by fine soot particles, 28%), b(sg) (Rayle igh scattering, 20%) and b(sw) (3%). The absorption of light by NO2 (b(ag)) is expected to contribute less than 5% of b(ext). On average, the percenta ge contribution of the visibility degrading species to b(ext) (excluding b( ag)) were: soot (53%), sulphate (21%), Rayleigh scattering (20%), non-soil K (2%) and humidity (3%). In terms of visibility degrading sources, motor v ehicles (including soot and the secondary products) are expected to contrib ute more than half of the b(ext) (excluding b(ag)) in Brisbane on average, followed by secondary sulphates (17%) and biomass burning (10%). (C) 1999 E lsevier Science Ltd. All rights reserved.