In:
Journal of Geophysical Research: Atmospheres, American Geophysical Union (AGU), Vol. 95, No. D4 ( 1990-03-20), p. 3579-3597
Abstract:
An intercomparison was made near Niwot Ridge, Colorado, of three different instruments for measuring NO 2 at low concentrations in ambient air: (1) the photolysis/chemiluminescence (PC) instrument, (2) the tunable diode laser absorption spectrometer (TDLAS), and (3) the Luminox instrument. Calibrated mixtures of NO 2 in air and NO 2 with possible interferants (HNO 3 , peroxyacetyl nitrate (PAN), H 2 O 2 , n ‐propyl nitrate, and O 3 ) were provided in simultaneous tests. In addition, ambient air measurements were made using the three instruments. Blind procedures were followed in preparing all results. Several conclusions were reached concerning the performance of these instruments during this intercomparison: (1) For NO 2 levels above 2 parts per billion by volume (ppbv), similar results were obtained for all instruments; (2) Below 2 ppbv, the expected interferences from ozone and PAN influenced the NO 2 measurements made using the Luminox instruments. Those interferences were sufficiently consistent that they could be corrected for by using the measured values Of O 3 and PAN down to about 0.3 ppbv NO 2 ; (3) The ozone interference on the Luminox instruments was removed by an ozone scrubber placed in the sampled air stream of the Luminox instrument. However, this did not remove PAN. In addition, the scrubber appeared to remove about 50% of the NO 2 as well; (4) Although no interferences were identified for the TDLAS technique, care must be taken in the data analysis near (or below) the detection limit for the instrument. At these levels the data reduction program provided with the TDLAS will tend to find background noise that is correlated with the reference NO 2 spectrum and calculate levels of NO 2 that are too high; (5) No interferences or artifacts were found for the final results reported by the PC technique. However, these results for ambient measurements were corrected by subtracting an artifact that averaged 5 parts per trillion by volume (pptv) and by calculating a correction for the effect of ambient ozone. This latter correction averaged 1.0% in magnitude.
Type of Medium:
Online Resource
ISSN:
0148-0227
DOI:
10.1029/JD095iD04p03579
Language:
English
Publisher:
American Geophysical Union (AGU)
Publication Date:
1990
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