A comparison of chemical mechanisms based on TRAMP-2006 field data

Chen, Shuang; Ren, Xinrong; Mao, J.; Chen, Zhong; Brune, William H.; Lefer, B. L.; Rappenglück, Bernhard; Flynn, James; Olson, Jennifer; Crawford, J. H.

doi:10.1016/j.atmosenv.2009.05.027

Cited by 75 publications

(73 citation statements)

References 45 publications

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“…Observations of OH and HO2 in the urban atmosphere have primarily been 5 made using fluorescence assay by gas expansion (FAGE), and comparisons with predicted radical concentrations using chemistry box models constrained with co-located radical precursor measurements have revealed varying levels of success in replicating observations. Radical concentrations have been reported to be under-predicted by models (Ren et al, 2003;Martinez et al, 2003;Emmerson et al, 2005a;Chen et al, 2010;Lu et al, 2012;Lu et al, 2013), over-predicted (George et al, 1999;Konrad et al, 2003;Dusanter et al, 2009) and, at times, models and measurements have been reported to be in 10 reasonable agreement, to within 40%, (Shirley et al, 2006;Emmerson et al, 2007;Kanaya et al, 2007;Sheehy et al, 2010;Elshorbany et al, 2012;Ren et al, 2013;Griffith et al, 2016). Often the level of agreement observed was found to be dependent on time of day (Brune et al, 2016); with poorest agreement between modelled and measured OH concentrations generally observed during the night.…”

Section: Introductionsupporting

confidence: 51%

Understanding in situ ozone production in the summertime through radical observations and modelling studies during the Clean air for London project (ClearfLo)

Whalley¹,

Stone²,

Dunmore³

et al. 2017

Preprint

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Abstract. Measurements of OH, HO2, RO2i (alkene and aromatic related RO2) and total RO2 radicals taken during the ClearfLo campaign in central London in the summer of 2012 are presented. A photostationary steady-state calculation of OH which considered measured OH reactivity as the OH sink term and the measured OH sources (of which HO2+NO reaction and HONO photolysis dominated) compared well with the observed levels of OH. Comparison with calculations from a detailed box model utilising the Master Chemical Mechanism v3.2, however, highlighted a substantial discrepancy between radical 20 observations under lower NOx conditions ([NO] < 1 ppbv) typically experienced during the afternoon hours, and indicated that the model was missing a significant peroxy radical sink; the model over-predicted HO2 by up to a factor of 10 at these times.Known radical termination steps, such as HO2 uptake on aerosols, were not sufficient to reconcile the model measurement discrepancies alone suggesting other missing termination processes. This missing sink was most evident when the air reaching the site had previously passed over central London to the east and when elevated temperatures were experienced and, hence, 25 contained higher concentrations of VOC. Uncertainties in the degradation mechanism at low NOx of complex biogenic and diesel related VOC species which were particularly elevated and dominated OH reactivity under these easterly flows, may account for some of the model measurement disagreement. Under higher [NO] (>3 ppbv) the box model increasingly underpredicted total [RO2]. The modelled and observed HO2 were in agreement, however, under elevated NO concentrations ranging from 7 -15 ppbv. 30The model uncertainty under low NO conditions leads to more ozone production predicted using modelled peroxy radical concentrations (~3 ppbv hr -1 ) versus ozone production from peroxy radicals measured (~1 ppbv hr -1 ). Conversely, ozone 2 production derived from the predicted peroxy radicals is up to an order of magnitude lower than from the observed peroxy radicals as [NO] increases beyond 7 ppbv due to the model under-prediction of RO2 under these conditions.

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Section: Introductionsupporting

confidence: 51%

Understanding in situ ozone production in the summertime through radical observations and modelling studies during the Clean air for London project (ClearfLo)

Whalley¹,

Stone²,

Dunmore³

et al. 2017

Preprint

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“…More data from the laboratory, environmental reaction chamber and field are required to improve atmospheric chemical mechanisms. It is very possible that there are major surprises to be discovered especially in the chemistry of HO x and other processes that control O 3 and particle formation [57].…”

Section: Discussionmentioning

confidence: 99%

A Review of Tropospheric Atmospheric Chemistry and Gas-Phase Chemical Mechanisms for Air Quality Modeling

et al. 2011

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Gas-phase chemical mechanisms are vital components of prognostic air quality models. The mechanisms are incorporated into modules that are used to calculate the chemical sources and sinks of ozone and the precursors of particulates. Fifty years ago essential atmospheric chemical processes, such as the importance of the hydroxyl radical, were unknown and crude air quality models incorporated only a few parameterized reactions obtained by fitting observations. Over the years, chemical mechanisms for air quality modeling improved and became more detailed as more experimental data and more powerful computers became available. However it will not be possible to incorporate a detailed treatment of the chemistry for all known chemical constituents because there are thousands of organic compounds emitted into the atmosphere. Some simplified method of treating atmospheric organic chemistry is required to make air quality modeling computationally possible. The majority of the significant differences between air quality mechanisms are due to the differing methods of treating this organic chemistry. The purpose of this review is to present an overview of atmospheric chemistry that is incorporated into air quality mechanisms and to suggest areas in which more research is needed.

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“…Instead, we have evaluated the HARC mechanism's predictions of radical concentrations against 2006 TRAMP data, because Vizuete et al (2008) have shown that ozone formed during emission events is directly related to the amount of hydroxyl (OH) radicals produced. The TRAMP data set was previously used by Chen et al (2010) to evaluate various established chemical mechanisms, including CB05 and SAPRC. Results of the evaluation versus TRAMP data are provided in the Supporting Information of Olaguer (2012), in addition to ozone simulations using the OZIPR model and the HARC, CB05, and SAPRC mechanisms.…”

Section: Model Descriptionmentioning

confidence: 99%

Near-source air quality impacts of large olefin flares

Olaguer

2012

Journal of the Air & Waste Management Association

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Large petrochemical flares, common in the Houston Ship Channel (the Ship Channel) and other industrialized areas in the Gulf of Mexico region, emit hundreds to thousands of pounds per hour of highly reactive volatile organic compounds (HRVOCs). We employed fine horizontal resolution (200 m Â 200 m) in a three-dimensional (3D) Eulerian chemical transport model to simulate two historical Ship Channel flares. The model reasonably reproduced the observed ozone rise at the nearest monitoring stations downwind of the flares. The larger of the two flares had an olefin emission rate exceeding 1400 lb/hr. In this case, the model simulated a rate of increase in peak ozone greater than 40 ppb/hr over a 12 km Â 12 km horizontal domain without any unusual meteorological conditions. In this larger flare, formaldehyde emissions typically neglected in official inventories enhanced peak ozone by as much as 16 ppb and contributed over 10 ppb to ambient formaldehyde up to $8 km downwind of the flare. The intense horizontal gradients in large flare plumes cannot be simulated by coarse models typically used to demonstrate ozone attainment. Moreover, even the relatively dense monitoring network in the Ship Channel may not be able to detect many transient high ozone events (THOEs) caused by industrial flare emissions in the absence of stagnant air recirculation or stalled sea breeze fronts, even though such conditions are unnecessary for the occurrence of THOEs.Implications: Flare minimization may be an important strategy to attain the U.S. federal ozone standard in industrialized areas, and to avoid inordinate exposure to formaldehyde in neighborhoods surrounding petrochemical facilities. Moreover, air quality monitoring networks, emission inventories, and chemical transport models with higher spatial and temporal resolution and more refined speciation of HRVOCs are needed to better account for the near-source air quality impacts of large olefin flares.

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A comparison of chemical mechanisms based on TRAMP-2006 field data

Cited by 75 publications

References 45 publications

Understanding in situ ozone production in the summertime through radical observations and modelling studies during the Clean air for London project (ClearfLo)

Understanding in situ ozone production in the summertime through radical observations and modelling studies during the Clean air for London project (ClearfLo)

A Review of Tropospheric Atmospheric Chemistry and Gas-Phase Chemical Mechanisms for Air Quality Modeling

Near-source air quality impacts of large olefin flares

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