Comparison of three methods for measuring light absorption by collected aerosols

Area of Science:

• Atmospheric science
• Aerosol optics
• Instrumental analysis

Background:

• Accurate measurement of visible light absorption by atmospheric aerosols is crucial for understanding climate and air quality.
• Various instruments exist, but their comparative performance, especially on diverse aerosol types, requires thorough evaluation.

Purpose of the Study:

• To compare the performance of three distinct instruments for measuring atmospheric aerosol light absorption.
• To assess the consistency of measurements across different instrument designs and aerosol compositions.

Main Methods:

• Comparison of a visual comparator, plate diffuser, and photoacoustic spectrometer (two versions each).
• Testing involved laboratory-generated aerosols (carbon, carbon/ammonium sulfate) and field-collected atmospheric aerosols.
• Aerosols were collected on Nuclepore filters; different reflective surfaces were used for the visual comparator.

Main Results:

• All three instrument types provided reasonably consistent measurements of aerosol absorption.
• Consistency was observed even when analyzing lightly absorbing nonurban atmospheric samples.
• Variations in instrument construction (e.g., photoacoustic spectrometer materials) did not significantly impair overall agreement.

Conclusions:

• The visual comparator, plate diffuser, and photoacoustic spectrometer are reliable methods for quantifying aerosol light absorption.
• These instruments are suitable for diverse atmospheric conditions, including those with weakly absorbing aerosols.