Development of an open-path incoherent broadband cavity-enhanced spectroscopy based instrument for simultaneous measurement of HONO and NO2 in ambient air |
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Authors: | T Wu W Chen E Fertein F Cazier D Dewaele and X Gao |
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Institution: | (1) Laboratoire de Physicochimie de l’Atmosph?re, Universit? du Littoral C?te d’Opale, 189A, Av. Maurice Schumann, 59140 Dunkerque, France;(2) Environmental Spectroscopy Laboratory, Anhui Institute of Optics & Fine Mechanics, Chinese Academy of Sciences, Hefei, 230031, China;(3) Key Laboratory of Nondestructive Test (Ministry of Education), Nanchang Hangkong University, Nanchang, 330063, China;(4) Centre Commun de Mesures, Universit? du Littoral C?te d’Opale, 145, Av. Maurice Schumann, 59140 Dunkerque, France; |
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Abstract: | We report on the development of an optical instrument based on incoherent broadband cavity-enhanced absorption spectroscopy
(IBBCEAS) for simultaneous open-path measurements of nitrous acid (HONO) and nitrogen dioxide (NO2) in ambient air using a UV light emitting diode operating at ∼366 nm. Detection limits of ∼430 pptv for HONO and ∼1 ppbv
for NO2 were achieved with an optimum acquisition time of 90 s, determined by an Allan variance analysis. Based on a 1.85 m long
high optical finesse open-path cavity, the effective optical path length of 2.8 km was realized in aerosol-free samples or
in an urban environment at modest aerosol levels. Such a kilometer long optical absorption is comparable to that achieved
in the well established differential optical absorption spectroscopy (DOAS) technology while keeping the instrument very compact.
Open-path detection configuration allows one to avoid absorption cell wall losses and sampling induced artifacts. The demonstrated
sensitivity and specificity shows high potential of this cost-effective and compact infrastructure for future field applications
with high spatial resolution. |
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