A MULTICHANNEL INTEGRATING NEPHELOMETER TO MEASURE REAL-TIME ATMOSPHERIC AEROSOL SCATTERING COEFFICIENTS

A novel multi-channel integrating nephelometer (MIN) is described whic h monitors the aerosol scattering coefficient in real-time for differe nt aerosol size fractions. A May cascade impactor fractionates the aer osol into eight specific size ranges, of which the latter five are mon itored by five helium-neon laser beams in the geometry of a reciprocal integrating nephelometer. The May impactor stage fractions are more l imited than the MIN size ranges which are accumulative. However, after subtraction, the MIN scattering coefficients and the aerosol mass on the impactor stages are for similar size fractions and should therefor e be directly correlated. Scattering coefficients in the range 2 x 10( -6)-1 x 10(-4) m-1 may be determined by a primary calibration while va lues up to 1 x 10(-2) m-1 may be determined by a secondary calibration using a NaCl aerosol.