Differential Optical Absorption Spectroscopy System for Suburb of Nanjing Atmospheric Pollution Monitoring

A full computer-controlled multiple light paths differential optical absorption spectroscopy (DOAS) apparatus are applied for air pollution monitoring in the suburb of Nanjing. Two optical paths have been installed in the DOAS system (OPSIS AB, Sweden), which is operating since September 2007, and both are controlled with the same main unit, and so only one analyzer system studies the light received. A beam-finding servosystem and automatic gain control permit unattended long-time monitoring. The concentrations and standard deviations of a wide number of pollutants, along with light levels in the system are stored in the central unit computer. Being able to monitor a range of user-specified compounds continuously in real time with a single system, the OPSIS instruments offer high levels of accuracy, reliability and data capture. The first results obtained with the DOAS system are presented in this work; comparisons between pollutant data obtained along the two optical paths (and relations between different pollutant concentrations) have been carried out.