Modification, Calibration and a Field Test of an Instrument for Measuring Light Absorption by Particles

Abstract

A filter-based single-wavelength photometer (Particle Soot Absorption Photometer, PSAP) for measuring light absorption by aerosols was modified to measure at three wavelengths, 467 nm, 530 nm, and 660 nm. The modified and an unmodified photometer were calibrated during the Reno Aerosol Optics Study (RAOS) 2002 against two absorption standards: a photoacoustic instrument and the difference between the extinction and scattering coefficient. This filter-based absorption method has to be corrected for scattering aerosol and transmission changes. A simple function for this was derived from the calibration experiment as a function of transmission and single-scattering albedo. For an unmodified PSAP at typical atmospheric absorption coefficients the algorithm yields about 5-7% lower absorption coefficients than does the usually used method. The three-wavelength PSAP was used for atmospheric measurements both during RAOS and during the New England Air Quality Study (NEAQS).

Comprehensive Simultaneous Shipboard and Airborne Characterization of Exhaust from a Modern Container Ship at Sea

“…The design of the three wavelength PSAP used in this study is described in Virkkula et al (27). The PSAP measures cumulative light absorption at 467, 530, and 660 nm as particles are collected onto a filter.…”

“…The PSAP measures cumulative light absorption at 467, 530, and 660 nm as particles are collected onto a filter. All absorption measurements presented in this paper have been corrected for scatter using the methods described in Virkkula et al (27).…”

The "dual-spot" Aethalometer: an improved measurement of aerosol black carbon with real-time loading compensation

“…All filter-based optical methods exhibit loading effects (Bond et al, 1999;Weingartner et al, 2003;Virkkula, 2010;Virkkula et al, 2005Virkkula et al, , 2007Collaud Coen et al, 2010;Park et al, 2010;Hyvärinen et al, 2013). The relationship between attenuation and BC surface loading is linear for low attenuation values.…”

“…The measurements must be compensated for this loading effect, so that they accurately represent the ambient BC concentrations. This has been performed in the past with an algorithm embedded in the filter photometer, assuming fixed compensation parameters (Bond et al, 1999;Virkkula, 2010;Virkkula et al, 2005Virkkula et al, , 2007 or with an attempt to compensate the data by performing an additional measurement of reflection (Petzold and Schönlinner, 2004) or scattering . Alternatively, a post-processing algorithm can be employed using either fixed parameters (Hyvärinen et al, 2013) or parameters obtained from the data themselves (Virkkula et al, 2007;Park et al, 2010;Hyvärinen et al, 2013).…”

Vertical distributions of aerosol optical properties during the spring 2016 ARIAs airborne campaign in the North China Plain

“…Its observation principle and uncertainties have been well documented (Bond et al, 1999;Sheridan et al, 2005;Virkkula et al, 2005;Chaudhry et al, 2007). To ensure a steady sample flow during flights, we monitored the total flow and PSAP flow rates to enhance the accuracy of measurements.…”