Atmospheric aerosol, both of natural and anthropogenic origin, regulates the earth global temperature by acting as a forcing on the radiative balance due to its optical properties, i.e., the ability to absorb and diffuse sunlight. Indeed, observations and models indicate how the effect of aerosol on climate depends greatly on light absorption properties ( Loeb and Su, 2010). Measuring the absorptive part of particulate matter is critical not only for estimating the direct and indirect effects of aerosols on climate but also, for assessments of air quality and health effects (WMO, report2012: Health Effects of Black Carbon). Black Carbon (BC), referred to in the WMO report, is an operational definition that describes the carbonaceous component present in fine particulate matter (PM 2.5) as measured by the absorption of light by aerosol settling on a filter. The main emission sources of BC are related to the combustion of engines (especially diesel), domestic wood or charcoal as well as forest or vegetation fires. The use of multiple wavelengths allows the calculation of the Angstrom absorption coefficient, which, by defining the spectral pattern of absorption, provides the characterization of the type of particulate matter.
The Dual Beam Absorption Photometer is an absorption photometer on a filter that measures the absorptive properties of particulate matter at 5 wavelengths comprising the IR-UV range. The use of dual beam technology allows for high measurement accuracy, making the instrument also suitable for background measurements.
DBAP5 was used in the RHAPS (Redox-activity and Health-effects of Atmospheric Primary and Secondary aerosols) measurement campaign, a PRIN project aimed at identifying specific properties of atmospheric particulate matter, or thereof combinations that are responsible for the toxicological properties of aerosols. This project, coordinated by the CNR’s ISAC institute, involved Statale di Milano, Sapienza di Roma, the University of Aquila, and INFNs in Florence and Genoa.