Search

We report on the development of a low-cost and compact instrument for quantifying atmospheric NO(2) concentrations by detecting NO(2) fluorescence using a commercial light-emitting diode around 435 nm as a fluorescence excitation light source. The minimum detectable limit of the NO(2) instrument developed has been estimated to be 9.8 parts per billion of volume mixing ratio (ppbv) in a 60 s integration time and with a signal-to-noise ratio of 2.

We report on the development of a highly sensitive detection system for measuring atmospheric NO(2) by means of a laser-induced fluorescence (LIF) technique at 473 nm using a diode-pumped Nd:YAG laser. A GaN-based laser diode emitting at 410 nm is also used as an alternative fluorescence-excitation source. For laboratory calibrations, standard NO(2) gas is diluted with synthetic air and is introduced into a fluorescence-detection cell. The NO(2) LIF signal is detected by a photomultiplier tube and processed by a photon-counting method. The minimum detectable limits of the NO(2) instrument developed have been estimated to be 0.14 ppbv and 0.39 ppbv (parts per billion, 10(-9), by volume) in 60 s integration time (signal-to-noise ratio of 2) for 473 and 410 nm excitation systems, respectively. Practical performance of the instrument has been demonstrated by the 24 hour continuous measurements of ambient NO(2) in a suburban area.