Measurement of Photolysis Rate of Trace Gases Based on Self-Developed Spectrometers
LI Hao-ran1, 2, ZENG Yi1*, ZHU Lei1, DOU Ke1, LIU Zhi-hong1, 3, CHANG Zhen1, JIANG Yu1, SI Fu-qi1
1. Key Laboratory of Environmental Optics and Technology, Anhui Institute of Optics and Fine Mechanics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China
2. University of Science and Technology of China, Science Island Branch, Hefei 230026, China
3. School of Biology, Food and Environment, Hefei University, Hefei 230601, China
Abstract：The photolysis rate and its measurement technology were first proposed by German scientists; Metcon developed the photolysis rate measuring instrument in the early 21st century, and then the technology received attention in China, and some universities and companies in China carried out research, and development on the photolysis rate measurement system. However, foreign products are generally larger and more expensive. Core devices such as spectrometers and receivers in domestic products still rely on imports and are vulnerable to foreign technology blockade. Under the guidance of the key project of “Comprehensive Control of Atmospheric, soil, and Groundwater Pollution” in China's “14th Five-Year Plan” National Key Research and Development plan, a spectrograph system for measuring the photolytic rate of atmospheric substances was developed and met the requirements of localization of its core components. The system uses a small spectrometer designed by ourselves as the core component and an optical receiver with uniform response in all directions to measure the photolysis rates of various substances after laboratory optical calibration. The operating band of the system is 285~430 nm, and the time resolution can reach 0.1 s. The measured substances include NO2, HONO, HCHO, H2O2，etc. Compared with the imported measuring instruments, the measurement error of the photolysis rate of each gas substance is less than 5%, and the correlation is more than 0.93. This system has continuously monitored the photolysis rate of gases in the atmosphere on Dongpu Island, Hefei City. The trend of NO2 photolysis rate and the correlation between NO2 photolysis rate and concentration were analyzed. It was found that the photolysis reaction was closely related to the energy driving the photochemical reaction, and the photolysis rate value was significantly higher on sunny days than on cloudy and rainy days. At the same time, it is found that there is an empirical formula between the integration curve of NO2 photolysis rate and concentration; the correlation is greater than 0.9, and the accumulation of NO2 concentration can be estimated by measuring the NO2 photolysis rate. The system realizes the localization of core components, the overall structure is simple and portable, convenient for field test and installation, and reduces cost and improves economy. This study provides data support for comprehensive monitoring and control of air pollution and has reference significance for environmental monitoring and pollution prevention in various regions.
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