Development of Automated and Continuous Measurement Equipment for Air Pollution Gases by Using Miniature Diffusion Scrubber and LED Photometer

近年来，大气环境污染已成为一个大问题。虽然各种分析仪器已被用于大气污染气体的测量，但不便于现场分析。因为分析仪器价格昂贵，需要在实验室中设置。因此，需要一种简单、方便的空气污染气体检测设备，本研究开发了一种小型扩散洗涤器。该装置结构简单，为双管结构，可以有效地收集气体。该器械使用PPTFE（多孔聚四氟乙烯）管作为内管，聚碳酸酯管作为外管。微型扩散洗涤器可以将污染气体收集到仅1 ml的捕集溶液中。因此，LED-PM（Light Emitting Diode-Photometer）比色法无需浓缩过程即可测定这些气体，并利用该装置和常规方法对环境空气中甲醛和二氧化氮的浓度进行了实际测量。结果表明，两种方法的测量值吻合较好。接下来，我们研制了一种新型的空气污染气体自动连续测量系统。该系统由微型扩散洗涤器和LED-PM组成。将捕集溶液进料到PPTFE管中，并将空气吸入PPTFE管和玻璃管之间的环形空间中。PPTFE管还充当吸收单元。可以与空气采样并行地测量洗涤器内的捕集溶液的吸光度。作为光源的LED还可以作为波长选择性光电探测器工作。我们将用该设备测量的环境空气中二氧化氮和氧化剂浓度与用传统方法测量的浓度进行了比较。在同一时期内，两种方法测量的环境空气中二氧化氮和氧化剂的浓度分别显示出良好的一致性。

In recent years, air environment pollution has become a big problem. While various analytical instruments have been used for the measurement of air pollution gases, but it is not convenient for the on-site analysis. Because analytical instruments are expensive and need to be set in a laboratory. Therefore, the simple and convenient equipment is required for measuring air pollution gases.In this study, we developed "miniature diffusion scrubber", which became more compact in size. This devise is very simple structure as a double tube, and it can efficiently collect only gases. This device uses PPTFE (porous poly tetra fluoro ethylene) tube for the inside tube and a poly-carbonate tube for the outside tube. The miniature diffusion scrubber can collect pollution gases into only 1ml of trapping solution. Therefore, colorimetric method with LED-PM (Light Emitting Diode-Photometer) can determined these gases without a concentration process.The concentration of formaldehyde and nitrogen dioxide in ambient air were actually measured by this equipment and the conventional method. It showed a good agreement between the measured values by both methods.Next, we developed a new automated continuous measurement system of air pollution gases. This system consists of the miniature diffusion scrubber and LED-PM. A trapping solution feeds into the PPTFE tube and an air is drawn into the annular space between the PPTFE tube and the glass tube. The PPTFE tube also acts as an absorption cell. The absorbance of trapping solution inside the scrubber can be measured in parallel with air sampling. The LED for the light source can also work as a wavelength selective photodetector.We compared nitrogen dioxide and oxidants concentrations in ambient air measured by this equipment with those measured by conventional methods. The concentrations of nitrogen dioxide and oxidants in ambient air measured by both methods showed a good agreement, respectively, during the same period.