PHOTOACOUSTIC AND FILTER MEASUREMENTS RELATED TO AEROSOL LIGHT-ABSORPTION DURING THE NORTHERN FRONT RANGE AIR-QUALITY STUDY (COLORADO 1996 1997)/

A new photoacoustic instrument for the measurement of aerosol light ab sorption was collocated with conventional aerosol instrumentation duri ng the 1996-1997 winter intensive monitoring period of the Northern Fr ont Range Air Quality, Study. Measurements of the Light absorption eff iciency for black carbon were 5 m(2)/g at 685 nm and IO m(2)/g at 532 nm, and for elemental carbon, they were 3.6 m(2)/g at 685 nm. We show that these values together with previous photoacoustic measurements of aerosol light absorption shed some light on the wavelength dependence of absorption efficiency for carbonaceous aerosol in the visible and near-visible region. Integrating plate type filter measurements of aer osol light absorption result in far larger values than those measured with the photoacoustic instrument. We demonstrate that a recently publ ished correction technique [Horvath, 1997] can yield improved agreemen t.