Development and application of a spectral light absorption photometer for aerosol and hydrosol samples

A multi-wavelength photometer for several particulate black carbon sample s ubstrates and sample sizes was developed and calibrated with synthetic soot samples and samples of external mixtures of soot and non-absorbing particl es. With this photometer a 13 month series of daily continental aerosol sam ples with aerodynamic diameters below 3.2 mu m was analysed to determine bl ack carbon concentrations and spectral absorption coefficients in the range 0.45-1 mu m wavelength. Gravimetric mass and sulphate were analysed on the same samples. Additionally, continuous SO2 and meteorological data were av ailable at the sampling site. Together with concurrent size distribution da ta 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 c omposition clearly demonstrated the effect of new German emission regulatio ns concerning large combustion sources. The fact that this compositional ch ange 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. (C) 2000 Elsevier Science Ltd. All rights reserved.