DEVELOPMENT AND APPLICATION OF A SPECTRAL LIGHT ABSORPTION PHOTOMETER FOR AEROSOL AND HYDROSOL SAMPLES

A multi-wavelength photometer for several particulate black carbon sample substrates and sample sizes was developed and calibrated with synthetic soot samples and samples of external mixtures of soot and non-absorbing particles. With this photometer a 13 month series of daily continental aerosol samples with aerodynamic diameters below 3.2µm was analysed to determine black carbon concentrations and spectral absorption coefficients in the range 0.45-1µm wavelength. Gravimetric mass and sulphate were analysed on the same samples. Additionally, continuous SO2 and meteorological data were available at the sampling site. Together with concurrent size distribution data this data set provides the information for subsequent radiative transfer modelling of the radiative forcing of the light absorbing aerosol over the study area. A strong break in the time series of mass concentrations and composition clearly demonstrated the effect of new German emission regulations concerning large combustion sources. The fact that this compositional change had no effect on black carbon concentrations confirms previous studies findings indicating that black carbon over Central Europe is more related to traffic sources than to power plants.