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NOx instrument intercomparison for laboratory biomass burning source studies and urban ambient measurements in Albuquerque, New Mexico.
- Source :
- Journal of the Air & Waste Management Association (Taylor & Francis Ltd); Nov2018, Vol. 68 Issue 11, p1175-1189, 15p
- Publication Year :
- 2018
-
Abstract
- Understanding nitrogen oxides (NO<subscript>x</subscript> = NO + NO<subscript>2</subscript>) measurement techniques is important as air-quality standards become more stringent, important sources change, and instrumentation develops. NO<subscript>x</subscript> observations are compared in two environments: source testing from the combustion of Southwestern biomass fuels, and urban, ambient NO<subscript>x</subscript>. The latter occurred in the urban core of Albuquerque, NM, at an EPA NCORE site during February-March 2017, a relatively clean photochemical environment with ozone (O<subscript>3</subscript>) <60 ppb for all but 6 hr. We compare two techniques used to measure NO<subscript>x</subscript> in biomass smoke during biomass burning source testing: light absorption at 405 nm and a traditional chemiluminescence monitor. Two additional oxides of nitrogen techniques were added in urban measurements: a cavity attenuated phase shift instrument for direct NO<subscript>2</subscript>, and the NO<subscript>y</subscript> chemiluminescence instrument (conversion of NO<subscript>y</subscript> to NO by molybdenum catalyst). We find agreement similar to laboratory standards for NO<subscript>x</subscript>, NO<subscript>2</subscript>, and NO comparing all four instruments (R<superscript>2</superscript> > 0.97, slopes between 0.95 and 1.01, intercepts < 2 ppb for 1-hr averages) in the slowly varying ambient setting. Little evidence for significant interferences in NO<subscript>2</subscript> measurements was observed in comparing techniques in late-winter urban Albuquerque. This was also confirmed by negligible NO<subscript>z</subscript> contributions as measured with an NO<subscript>y</subscript> instrument. For the rapidly varying (1-min) higher NO<subscript>x</subscript> concentrations in biomass smoke source testing, larger variability characterized chemiluminescence and absorption instruments. Differences between the two instruments were both positive and negative and occurred for total NO<subscript>x</subscript>, NO, and NO<subscript>2</subscript>. Nonetheless, integrating the NO<subscript>x</subscript> signals over an entire burn experiment and comparing 95 combustion experiments, showed little evidence for large systematic influences of possible interfering species biasing the methods. For concentrations of <2 ppm, a comparison of burn integrated NOx, NO<subscript>2</subscript>, and NO yielded slopes of 0.94 to 0.96, R<superscript>2</superscript> of 0.83 to 0.93, and intercepts of 8 to 25 ppb. We attribute the latter, at least in part, to significant noise particularly at low NO<subscript>x</subscript> concentrations, resulting from short averaging times during highly dynamic lab burns. Discrepancies between instruments as indicated by the intercepts urge caution with oxides of nitrogen measurements at concentrations <50 ppb for rapidly changing conditions. Implications: Multiple NO<subscript>x</subscript> measurement methods were employed to measure NO<subscript>x</subscript> concentrations at an EPA NCORE site in Albuquerque, NM, and in smoke produced by the combustion of Southwestern biomass fuels. Agreement shown during intercomparison of these NO<subscript>x</subscript> techniques indicated little evidence of significant interfering species biasing the methods in these two environments. Instrument agreement is important to understand for accurately characterizing ambient NO<subscript>x</subscript> conditions in a range of environments. [ABSTRACT FROM AUTHOR]
- Subjects :
- NITRIC oxide
BIOMASS
AIR quality
CHEMILUMINESCENCE
LIGHT absorption
Subjects
Details
- Language :
- English
- ISSN :
- 10962247
- Volume :
- 68
- Issue :
- 11
- Database :
- Complementary Index
- Journal :
- Journal of the Air & Waste Management Association (Taylor & Francis Ltd)
- Publication Type :
- Academic Journal
- Accession number :
- 132556331
- Full Text :
- https://doi.org/10.1080/10962247.2018.1487347