Study of sampling efficiency for nitric acid gas and particulate nitrate concentrations in atmosphere

• Main Authors: Huang, Gorgin, 黃博君
• Other Authors: Hsunling Bai
• Format: Others
• Language: zh-TW
• Published: 1996
• Online Access: http://ndltd.ncl.edu.tw/handle/05799579398694638065

碩士 === 國立交通大學 === 環境工程研究所 === 84 === Annular denuder system, owing to its excellent efficiency on acidic and basicgas and their particulate salts as proved by many laboratory studies, is themost widely used sampling method. But its sampling efficiency was alsoquestioned while detecting nitric acid gaseous concentration during fieldsampling. The interferences were suspected from nitrogen- containing compoundswhich cause positive errors from the real concentration. For example, theinterference of nitrogen dioxide and nitrous acid gas, the adsorption of nitratecontaining particle deposited to the denuder wall by diffusional process, andthe evaporation of ammonium nitrate etc., will produce positive errors to thesampling result.The comparison of Annular denuder sampling system （ ADS ） and Filter pack （FP ） sampling system was made in this study in terms of the sampling of nitricacid gas and particulate nitrate. The results show similar sampling efficienciesfor total nitrate ion, but there were some differences on particulate nitrateand gaseous nitric acid. The collection of particulate nitrate by FP isinterfered probably by nitric acid and nitrous acid gas. The nitrate evaporationrates from the Teflon filter of FP are lower than that from ADS.The ADS has a better efficiency for particulate nitrate than the FP method. Butfor collecting nitric acid gas the ADS is easily interfered by other compounds.According to experimental results, the sampling error of ADS for nitric acid gasusing only one denuder tube may be larger than 100 ﹪. The precipitation orevaporation of particulate nitrate accounts for around 10 ﹪ error, thereforemost of the error may be contributed by other nitrogen-containing gaseouscompounds such as nitrous acid and nitrogen dioxide.