| Urban environment pollution problem is becoming more and more serious, it has attracted the attention all of the world.NO2 is one of the near ground atmospheric pollutants, Excessive NO2 will produce photochemical smog, forming acid rain then lead to land eutrophication. It not only pose a threat to the ecological environment, but also endanger human health. So the monitoring of atmospheric NO2 has very important meaning to the analysis of pollution source and environmental protection work.Chemical detection method is unable to meet the requirements of modern atmospheric pollutants monitoring due to its complex sampling process and impossible to monitoring on line. Optical detection method gets rid of these disadvantages, it is perfect for near ground atmospheric trace gas detection by the advantages of high sensitivity, low detection limits, low cost, simple operations.According to the monitoring demand of atmospheric NO2, the research on quantitative method of atmospheric NO2 was carried out by the simplified telescope detection system based on differential optical absorption spectroscopy (DOAS) technique with optical fiber coupling technique. Blue LED was chosen for light source by the absorption characteristics of NO2. Continuous observations of atmospheric NO2 were carried out for two days. Atmospheric NO2 concentration was below 48ppb within the period. During the process of measurement, the temperature fluctuation of the light source was within the range of 0.2℃ by the control of thermostatic system, the stability of the absorption spectrum was improved. When the measurement path is 800m, NO2 detection limit is 3.32ppb retrieved over 445nm-465nm. The comparison results between LED-DOAS and XE-DOAS show that correlation coefficient is 0.98.The research results show that DOAS quantitative method based on LED can accurately obtain atmospheric NO2 concentration, which can provide firm data support for environmental pollution control work and atmospheric chemistry research. |
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