Observations of atmospheric trace gases in China using a compact LED long path DOAS system

Özet

In this paper, we present the development and evaluation of a new designed light emitting diodes (LEDs) basedoptical fiber coupling long-path differential optical absorption spectroscopy (LP-DOAS) instrument for atmosphericSO2, O3 and NO2 detections. The strongest absorption structures of these trace gases scattered along awide spectral range which could not be covered by a single LED. Therefore, a new fiber optic coupling telescopewas developed to combine multiple LEDs with different spectral emission ranges as broad band light source foratmospheric trace gas detections. Details of the experimental setup, measurement and retrieval procedure, erroranalysis and the atmospheric measurement results are presented. The new LED LP-DOAS measurement resultsshow perfect agreements with a co-located Xenon Lamp coaxial LP-DOAS observations with Pearson correlationcoefficient (R) larger than 0.9 for SO2, O3 and NO2 observations. The estimated background light contributesabout 3–10% of the total measurement error during daytime, which is improved by a factor of 3–10 compared toprevious study. Diurnal analysis of the measurement results shows a similar diurnal pattern of NO2 and SO2which implies that they are probably originated from similar emission sources. Satellite observation andbackward trajectories analysis indicated local and regional transports of pollutants have significant impacts onthe air quality in Hefei. Analysis of the wind speed and wind direction show that elevated NO2 and SO2 levelswere related to the emissions of the power plant and factories located at the east and northeast of the measurementsite.