An Evaluation of Integrating Techniques for Measuring Atmospheric Nitrogen Dioxide

Two integrating techniques for measuring ambient NO2 were evaluated. Both techniques involved quantitative collection of NO2 in a reagent coated cartridge, specifically triethanolamine (TEA)-coated silica gel and diphenyl-amine (DPA)-coated Florisil. The evaluation of these techniques consisted of laboratory and field studies. The laboratory studies of the TEA method indicated collection and reaction efficiencies of 100 and 90%, respectively. A positive interference occurred when O3 and NO were passed through the cartridge simultaneously. PAN was found to produce a 67% positive interference. The ambient concentrations determined using the TEA method were approximately a factor of two higher than those determined using TDLAS. For the DPA method the collection and reaction efficiencies were determined to be 100 and 64%, respectively. O3 produced a negative interference by reacting with the NO2-DPA products. PAN produced a 42% positive interference. A regression of the DPA versus TDLAS determined ambient NO2 concentrations yielded a slope of .91±.08 (r2=0.990.). Neither method was found suitable for network use in its present form.