NO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; photolysis frequencies in street canyons

Koepke, Peter; Garhammer, Markus; Heß, Michael; Roeth, E. P.

doi:10.5194/acp-10-7457-2010

Cited by 8 publications

(4 citation statements)

References 16 publications

(13 reference statements)

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“…The value for the photolysis frequency is a rough estimate for clear viewing conditions [cf. Koepke et al , 2010], the actual one might be lower, which would lead to an even lower L Leighton .…”

Section: Results Discussion and Comparison With Other Datamentioning

confidence: 99%

Flux calculation using CARIBIC DOAS aircraft measurements: SO₂ emission of Norilsk

et al. 2012

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[1] Based on a case-study of the nickel smelter in Norilsk (Siberia), the retrieval of trace gas fluxes using airborne remote sensing is discussed. A DOAS system onboard an Airbus 340 detected large amounts of SO 2 and NO 2 near Norilsk during a regular passenger flight within the CARIBIC project. The remote sensing data were combined with ECMWF wind data to estimate the SO 2 output of the Norilsk industrial complex to be around 1 Mt per year, which is in agreement with independent estimates. This value is compared to results using data from satellite remote sensing (GOME, OMI). The validity of the assumptions underlying our estimate is discussed, including the adaptation of this method to other gases and sources like the NO 2 emissions of large industries or cities.

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Section: Results Discussion and Comparison With Other Datamentioning

confidence: 99%

Flux calculation using CARIBIC DOAS aircraft measurements: SO₂ emission of Norilsk

et al. 2012

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“…Eco Physics AG PLC 760), and the averaged measured spectral output of six individual BLC UV-LED arrays of varying running hours. Also shown is the NO 2 quantum yield (Gardner et al, 1987;Koepke et al, 2010). It can be discerned that the UV-LED output overlaps fully with the NO 2 absorption band and the NO 2 quantum yield and is therefore photon-efficient.…”

Section: Possible Photolytic Interferences Of Blcsmentioning

confidence: 99%

Interferences in photolytic NO<sub>2</sub> measurements: explanation for an apparent missing oxidant?

et al. 2016

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Abstract. Measurement of NO 2 at low concentrations (tens of ppts) is non-trivial. A variety of techniques exist, with the conversion of NO 2 into NO followed by chemiluminescent detection of NO being prevalent. Historically this conversion has used a catalytic approach (molybdenum); however, this has been plagued with interferences. More recently, photolytic conversion based on UV-LED irradiation of a reaction cell has been used. Although this appears to be robust there have been a range of observations in low-NO x environments which have measured higher NO 2 concentrations than might be expected from steady-state analysis of simultaneously measured NO, O 3 , j NO 2 , etc. A range of explanations exist in the literature, most of which focus on an unknown and unmeasured "compound X" that is able to convert NO to NO 2 selectively. Here we explore in the laboratory the interference on the photolytic NO 2 measurements from the thermal decomposition of peroxyacetyl nitrate (PAN) within the photolysis cell. We find that approximately 5 % of the PAN decomposes within the instrument, providing a potentially significant interference. We parameterize the decomposition in terms of the temperature of the light source, the ambient temperature, and a mixing timescale (∼ 0.4 s for our instrument) and expand the parametric analysis to other atmospheric compounds that decompose readily to NO 2 (HO 2 NO 2 , N 2 O 5 , CH 3 O 2 NO 2 , IONO 2 , BrONO 2 , higher PANs). We apply these parameters to the output of a global atmospheric model (GEOS-Chem) to investigate the global impact of this interference on (1) the NO 2 measurements and (2) the NO 2 : NO ratio, i.e. the Leighton relationship. We find that there are significant interferences in cold regions with low NO x concentrations such as the Antarctic, the remote Southern Hemisphere, and the upper troposphere. Although this interference is likely instrument-specific, the thermal decomposition to NO 2 within the instrument's photolysis cell could give an at least partial explanation for the anomalously high NO 2 that has been reported in remote regions. The interference can be minimized by better instrument characterization, coupled to instrumental designs which reduce the heating within the cell, thus simplifying interpretation of data from remote locations.

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“…In contrast, it has been reported that the photolysis of NO 2 can be considerably decreased (by 40 % compared to open areas) within street canyons (Koepke et al, 2010) because incoming direct and diffuse sun light at large zenith angles may be obstructed by the buildings. Koepke et al (2010) suggest the application of a scaling factor of 0.5 to adjust J NO 2 from a free horizon to street canyons. it is expected that the photochemical steady state assumption was fulfilled.…”

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confidence: 81%

Development of the city-scale chemistry transport model CityChem-EPISODE and its application to the city of Hamburg

Karl

2018

Preprint

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Abstract. This paper describes the City-scale Chemistry (CityChem) extension of the urban dispersion model EPISODE with the aim to enable chemistry/transport simulations of multiple reactive pollutants on urban scales. The new model is called CityChem-EPISODE. The primary focus is on the simulation of urban ozone concentrations. Ozone is produced in photochemical reaction cycles involving nitrogen oxides (NO X ) and volatile organic compounds (VOC) emitted by various anthropogenic activities in the urban area. The performance of the new model was evaluated with a series of synthetic tests 5 and with a first application to the air quality situation in the city of Hamburg, Germany. The model performs fairly well for ozone in terms of temporal correlation and bias at the air quality monitoring stations in Hamburg. In summer afternoons, when photochemical activity is highest, modelled median ozone at an inner-city urban background station was about 30 % lower than the observed median ozone. Inaccuracy of the computed photolysis frequency of nitrogen dioxide (NO 2 ) is the most probable explanation for this. CityChem-EPISODE reproduces the spatial variation of annual mean NO 2 concentrations between urban 10 background, traffic and industrial stations. However, the temporal correlation between modelled and observed hourly NO 2 concentrations is weak for some of the stations. For daily mean PM 10 , the performance of CityChem-EPISODE is moderate due to low temporal correlation. The low correlation is linked to uncertainties in the seasonal cycle of the anthropogenic particulate matter (PM) emissions within the urban area. Missing emissions from domestic heating might be an explanation for the too low modelled PM 10 in winter months. Four areas of need for improvement have been identified: (1) dry and wet deposition 15 fluxes; (2) treatment of photochemistry in the urban atmosphere; (3) formation of secondary inorganic aerosol (SIA); and (4) formation of biogenic and anthropogenic secondary organic aerosol (SOA). The inclusion of secondary aerosol formation will allow for a better sectorial attribution of observed PM levels. Envisaged applications of the CityChem-EPISODE model are urban air quality studies, environmental impact assessment, sensitivity analysis of sector-specific emission and the assessment of local and regional emission abatement policy options.

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NO<sub>2</sub> photolysis frequencies in street canyons

Cited by 8 publications

References 16 publications

Flux calculation using CARIBIC DOAS aircraft measurements: SO₂ emission of Norilsk

Flux calculation using CARIBIC DOAS aircraft measurements: SO₂ emission of Norilsk

Interferences in photolytic NO<sub>2</sub> measurements: explanation for an apparent missing oxidant?

Development of the city-scale chemistry transport model CityChem-EPISODE and its application to the city of Hamburg

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NO&lt;sub&gt;2&lt;/sub&gt; photolysis frequencies in street canyons

Cited by 8 publications

References 16 publications

Flux calculation using CARIBIC DOAS aircraft measurements: SO2 emission of Norilsk

Flux calculation using CARIBIC DOAS aircraft measurements: SO2 emission of Norilsk

Interferences in photolytic NO&lt;sub&gt;2&lt;/sub&gt; measurements: explanation for an apparent missing oxidant?

Development of the city-scale chemistry transport model CityChem-EPISODE and its application to the city of Hamburg

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Product

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NO<sub>2</sub> photolysis frequencies in street canyons

Flux calculation using CARIBIC DOAS aircraft measurements: SO₂ emission of Norilsk

Flux calculation using CARIBIC DOAS aircraft measurements: SO₂ emission of Norilsk

Interferences in photolytic NO<sub>2</sub> measurements: explanation for an apparent missing oxidant?