Evidence of increased mass fraction of NO2 within real-world NOx emissions of modern light vehicles — derived from a reliable online measuring method

Alvarez, Robert; Weilenmann, Martin; Favez, J.-Y.

doi:10.1016/j.atmosenv.2008.01.046

Cited by 75 publications

(42 citation statements)

References 15 publications

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“…The main reason for this increase is considered to be the use of diesel oxidation catalysts (DOCs) and catalyzed diesel particulate filters (DPFs) (Bar-Ilan et al, 2010;Bishop et al, 2010), which became standard equipment on new diesel trucks starting with 2007 (Ban- Weiss et al, 2008; see also: http://www.epa.gov/oms/highwaydiesel/). These exhaust-treatment systems may enhance NO 2 fraction in NO x emission up to 70% (Alvarez et al, 2008;Millstein and Harley, 2010).…”

Section: Resultsmentioning

confidence: 99%

Radical precursors and related species from traffic as observed and modeled at an urban highway junction

Rappenglück

Lubertino

Alvarez

et al. 2013

Journal of the Air & Waste Management Association

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Nitrous acid (HONO) and formaldehyde (HCHO) are important precursors for radicals and are believed to favor ozone formation significantly. Traffic emission data for both compounds are scarce and mostly outdated. A better knowledge of today's HCHO and HONO emissions related to traffic is needed to refine air quality models. Here the authors report results from continuous ambient air measurements taken at a highway junction in Houston, Texas, from July 15 to October 15, 2009. The observational data were compared with emission estimates from currently available mobile emission models (MOBILE6; MOVES [MOtor Vehicle Emission Simulator]). Observations indicated a molar carbon monoxide (CO) versus nitrogen oxides (NO x ) ratio of 6.01 AE 0.15 (r 2 ¼ 0.91), which is in agreement with other field studies. Both MOBILE6 and MOVES overestimate this emission ratio by 92% and 24%, respectively. For HCHO/CO, an overall slope of 3.14 AE 0.14 g HCHO/kg CO was observed. Whereas MOBILE6 largely underestimates this ratio by 77%, MOVES calculates somewhat higher HCHO/CO ratios (1.87) than MOBILE6, but is still significantly lower than the observed ratio. MOVES shows high HCHO/CO ratios during the early morning hours due to heavyduty diesel off-network emissions. The differences of the modeled CO/NO x and HCHO/CO ratios are largely due to higher NO x and HCHO emissions in MOVES (30% and 57%, respectively, increased from MOBILE6 for 2009), as CO emissions were about the same in both models. The observed HONO/NO x emission ratio is around 0.017 AE 0.0009 kg HONO/kg NO x which is twice as high as in MOVES. The observed NO 2 /NO x emission ratio is around 0.16 AE 0.01 kg NO 2 /kg NO x , which is a bit more than 50% higher than in MOVES. MOVES overestimates the CO/CO 2 emission ratio by a factor of 3 compared with the observations, which is 0.0033 AE 0.0002 kg CO/kg CO 2 . This as well as CO/NO x overestimation is coming from light-duty gasoline vehicles.Implications: Nitrous acid (HONO) and formaldehyde (HCHO) are important precursors for radicals that ultimately contribute to ozone formation. There still exist uncertainties in emission sources of HONO and HCHO and thus regional air quality modeling still tend to underestimate concentrations of free radicals in the atmosphere. This paper demonstrates that the latest U.S. Environmental Protection Agency (EPA) traffic emission model MOVES still shows significant deviations from observed emission ratios, in particular underestimation of HCHO/CO and HONO/NO x ratios. Improving the performance of MOVES may improve regional air quality modeling.

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Section: Resultsmentioning

confidence: 99%

Radical precursors and related species from traffic as observed and modeled at an urban highway junction

Rappenglück

Lubertino

Alvarez

et al. 2013

Journal of the Air & Waste Management Association

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“…Surface O 3 in the atmosphere has been monitored at various sites around the globe for the past several decades (Oltmans, 1981;Volz and Kley, 1988). Many studies have been carried out on the photochemical characteristics of O 3 and its precursor gases in the United States (Aneja et al, 1991;Qin et al, 2004;Alvarez et al, 2008;Yarwood et al, 2008), Europe (Zerefos et al, 2002;Mazzeo et al, 2005;Bossioli et al, 2007;Ordóñez et al, 2007;Solberg et al, 2008), and Asia (Pudasainee et al, 2006;Zhu et al, 2006;Bonasoni et al, 2008;Shan et al, 2008;Moore and Semple, 2009;Yin et al, 2010;Han et al, 2011). In the free troposphere region over Northern Hemisphere, increasing ozone concentration has been recently reported based on aircraft and ozonesonde data (Proberaj et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

Observational Study of Surface O3, NOx, CH4 and Total NMHCs at Kannur, India

Nishanth

2014

Aerosol Air Qual. Res.

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This paper presents the results of measurements of the surface ozone (O 3 ), oxides of nitrogen (NO x ), methane (CH 4 ) and total non-methane hydrocarbons (TNMHCs) in a rural coastal location at Kannur (11.9°N, 75.4°E, 5 m asl), India from November 2009 to December 2011. The diurnal cycle for surface O 3 had a peak in the afternoon and declined during nighttime. The maximum and minimum mixing ratio of surface O 3 was observed in winter and monsoon seasons respectively. NO x concentration was high during mid-night to early morning and low during noontime. The diurnal variations of mixing ratios for NO x and O 3 were anti-correlated. Monthly average maximum (2.26 ± 0.44 ppmv) and minimum (0.43 ± 0.19 ppmv) CH 4 concentrations were observed in December and August respectively. The diurnal variations of CH 4 were similar to that of NO x . A CH 4 buildup was observed during early morning hours throughout the observational period. On an annual basis, the maximum, minimum and average total NMHCs were (25.45 ± 6.58 ppbv), (13.84 ± 4.31 ppbv), and (19.23 ± 5.56 ppbv) respectively at the observational site. Analysis of O 3 , NO, NO 2 , CH 4 and NMHC have been carried out and the correlation between O 3 and its precursors is discussed detailed. Further, the diurnal variation of O 3 over a free tropospheric region at Ooty, a hill station lying in the Western Ghats region of south India on clear sky days in February 2011 is also reported for a comparison.

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“…The NO 2 share of emitted NOx is increasing (Keuken et al, 2009) due to the increased number of diesel vehicles, especially those equipped with exhaust after-treatment systems (i.e. CRT -continuous regenerating trap) which use NO 2 to regenerate the filter: soot particles are burned at 550 • K using NO 2 (Alvarez et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

Prediction of ultrafine particle number concentrations in urban environments by means of Gaussian process regression based on measurements of oxides of nitrogen

Reggente

Peters

Theunis

et al. 2014

Environmental Modelling & Software

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Evidence of increased mass fraction of NO2 within real-world NOx emissions of modern light vehicles — derived from a reliable online measuring method

Cited by 75 publications

References 15 publications

Radical precursors and related species from traffic as observed and modeled at an urban highway junction

Radical precursors and related species from traffic as observed and modeled at an urban highway junction

Observational Study of Surface O3, NOx, CH4 and Total NMHCs at Kannur, India

Prediction of ultrafine particle number concentrations in urban environments by means of Gaussian process regression based on measurements of oxides of nitrogen

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