A New type UV-visible DOAS System Based on Photodiode Array (PDA)

摘要

DOAS technique provides a more representative picture of air quality and typical urban exposures over traditional point monitoring equipments, it has been widely used for urban air quality monitoring in China. Most commercial DOAS instruments presently used for air quality monitoring adopt photomultiplier and scanning slit as detector, which is called slotted disk (SD) detector. In contrast with the SD detector, Photodiode Array can overcome the problem of scintillation noise caused by atmospheric turbulence and reduce photon noise. We report here a new type UV-visible DOAS system based on photodiode array. The properties of the system, including offset, dark current, noise, linearity of the detector and resolution, stray light of the spectrometer, are described. Field observations of a number of pollutants (e.g. SO_2, NO_2, O_3 and HCHO) were performed in the urban area of Beijing City during August 2004. The measurement results show that the system fulfils automatic ambient air monitoring with high time resolution and sufficient sensitivity.