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NOX/NOY MONITORING USING MODIFIED/UNMODIFIED COMMERCIAL INSTRUMENTATION
Citation:
Kronmiller, K. G., M. L. Wheeler, E. H. Daughtrey Jr., AND W A. McClenny. NOX/NOY MONITORING USING MODIFIED/UNMODIFIED COMMERCIAL INSTRUMENTATION. Presented at SOS Data Analysis Workshop 2000, Research Triangle Park, NC, March 6-10, 2000.
Impact/Purpose:
The main objective of this task is to provide the Agency with instrumentation to support its monitoring activities with respect to establishing the ambient air concentrations of ozone and ozone precursors such as nitrogen oxides and volatile organic compounds.
Description:
Three systems were used for monitoring oxides of nitrogen (NO, NO2, Noy, at the Cornelia Fort Airpark site in the 1999 Southern Oxidant Study near Nashville, TN during the months of June and July. Of the three systems, one was an unmodified ultraviolet differential optical absorption spectrometer (UV-DOAS) instrument manufactured by OPSIS AB (Furuland, Sweden) configured to measure NO2. The second system was a standard chemiluminescence type oxides of nitrogen analyzer manufactured by Thermo Instruments (model Tei42, Franklin, MA) modified with an automated flow controller so that ambient air passed through either a standard heated molybdenum converter, a chromium trioxide converter or an unaffected pathway. This system also included a luminol based chemiluminescence analyzer (LMA3, Unisearch, Toronto, Canada) sampling the same air as the TEI42 monitor from a common manifold. The third system used was a modified chemiluminescence monitor which, in addition to the standard heated molybdenum converter, used a prototype NO2 photolytic cell for a direct measurement of NO2, unlike standard chemiluminescence Nox monitors which derive NO2 by a mathematical subtraction of the NO value from the Noy value. This instrument thus provided NO2 by photolysis as well as direct NO and Noy measurements. The standard instrument (model Tei42C, Thermo Instruments) was modified by the manufacturer to include additional sampling, controls and firmware revisions to permit the use of photolytic converter.