Instrument for long-path spectral extinction measurements in air: application to sizing of airborne particles

Abstract

A novel instrument that is capable of taking spectral extinction measurements over long optical paths (approximately 1-100 m) in the UV, visible, and IR ranges is described. The instrument is fully automated, and the extinction spectrum is acquired in almost real time (approximately 5-10 s) with a resolution of ~3 nm. Its sensitivity and accuracy were estimated by tests carried out in a clean room that showed that, for optical paths between 50 and 100 m, the extinction coefficient can be detected at levels of ~10(-5) m(-1). Tests carried out on calibrated latex particles showed that, when it was combined with an appropriate inversion method, the technique could be profitably applied to characterize airborne particulate distributions. By carrying out measurements over optical paths of ~100 m, the instrument is also capable of detecting extinction coefficients that are due to aerosol concentrations well below the limits imposed by the European Economic Community for atmospheric pollution (150 mug/m(3)). Scaled over optical paths of ~10 m, the limit imposed for particle emissions from industrial plants (10 mg/m(3)) can also be detected sensitively.

Night-Time Ground Hyperspectral Imaging for Urban-Scale Remote Sensing of Ambient PM. I. Aerosol Optical Thickness Acquisition

“…Such systems have a dedicated reflector at the periphery of the (relatively short) open path (Paganini et al 2001;Müller et al 2005;Varma et al 2009). In contrast, here we portray the first steps toward the development of a novel passive RS approach for ground imaging spectroscopy procedure with high temporal resolution, applicable for night-time (i.e., dark scenes) urban monitoring of fine PM.…”