scholarly journals Airborne determination of the temporo-spatial distribution of benzene, toluene, nitrogen oxides and ozone in the boundary layer across Greater London, UK

2015 ◽  
Vol 15 (9) ◽  
pp. 5083-5097 ◽  
Author(s):  
M. D. Shaw ◽  
J. D. Lee ◽  
B. Davison ◽  
A. Vaughan ◽  
R. M. Purvis ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Nitrogen Oxides ◽  
Linear Regression Analysis ◽  
Proton Transfer Reaction ◽  
Mixing Ratios ◽  
Spatially Resolved ◽  
Dual Channel ◽  
Benzene Toluene

Abstract. Highly spatially resolved mixing ratios of benzene and toluene, nitrogen oxides (NOx) and ozone (O3) were measured in the atmospheric boundary layer above Greater London during the period 24 June to 9 July 2013 using a Dornier 228 aircraft. Toluene and benzene were determined in situ using a proton transfer reaction mass spectrometer (PTR-MS), NOx by dual-channel NOx chemiluminescence and O3 mixing ratios by UV absorption. Average mixing ratios observed over inner London at 360 ± 10 m a.g.l. were 0.20 ± 0.05, 0.28 ± 0.07, 13.2 ± 8.6, 21.0 ± 7.3 and 34.3 ± 15.2 ppbv for benzene, toluene, NO, NO2 and NOx respectively. Linear regression analysis between NO2, benzene and toluene mixing ratios yields a strong covariance, indicating that these compounds predominantly share the same or co-located sources within the city. Average mixing ratios measured at 360 ± 10 m a.g.l. over outer London were always lower than over inner London. Where traffic densities were highest, the toluene / benzene (T / B) concentration ratios were highest (average of 1.8 ± 0.5 ppbv ppbv-1), indicative of strong local sources. Daytime maxima in NOx, benzene and toluene mixing ratios were observed in the morning (~ 40 ppbv NOx, ~ 350 pptv toluene and ~ 200 pptv benzene) and in the mid-afternoon for ozone (~ 40 ppbv O3), all at 360 ± 10 m a.g.l.

scholarly journals Airborne determination of the temporo-spatial distribution of benzene, toluene, nitrogen oxides and ozone in the boundary layer across Greater London, UK

2014 ◽  
Vol 14 (19) ◽  
pp. 27335-27371 ◽  
Author(s):  
M. D. Shaw ◽  
J. D. Lee ◽  
B. Davison ◽  
A. Vaughan ◽  
R. M. Purvis ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Nitrogen Oxides ◽  
Linear Regression Analysis ◽  
Proton Transfer Reaction ◽  
Mixing Ratios ◽  
Spatially Resolved ◽  
Dual Channel ◽  
Benzene Toluene

Abstract. Highly spatially resolved mixing ratios of benzene and toluene, nitrogen oxides (NOx) and ozone (O3) were measured in the atmospheric boundary layer above Greater London during the period 24 June to 9 July 2013 using a Dornier 228 aircraft. Toluene and benzene were determined in-situ using a proton transfer reaction mass spectrometer (PTR-MS), NOx by dual channel NOx chemiluminescence and O3 mixing ratios by UV absorption. Average mixing ratios observed over inner London at 360 ± 10 m a.g.l. were 0.20 ± 0.05, 0.28 ± 0.07, 13.2 ± 8.6, 21.0 ± 7.3 and 34.3 ± 15.2 ppbv for benzene, toluene, NO, NO2 and NOx respectively. Linear regression analysis between NO2, benzene and toluene mixing ratios yielded a trimodal distribution indicating that these compounds predominantly share the same or co-located sources within the city and that a significant fraction of NOx is directly emitted as NO2. Average mixing ratios measured at 360 ± 10 m a.g.l. over outer London were always lower than over inner London. Where traffic densities were highest, the toluene $/$ benzene (T / B) concentration ratios were highest (average of 1.8 ± 0.3 ppbv ppbv−1) indicative of strong local sources. Daytime maxima in NOx, benzene and toluene mixing ratios were observed in the morning (~40 ppbv NOx, ~350 pptv toluene and ~200 pptv benzene) and for ozone in the mid-afternoon (~40 ppbv O3) all at 360 ± 10 m a.g.l.

scholarly journals Near-surface and path-averaged mixing ratios of NO<sub>2</sub> derived from car DOAS zenith-sky and tower DOAS off-axis measurements in Vienna: a case study

2019 ◽  
Vol 19 (9) ◽  
pp. 5853-5879 ◽  
Author(s):  
Stefan F. Schreier ◽  
Andreas Richter ◽  
John P. Burrows
Keyword(s):  
Boundary Layer ◽  
Planetary Boundary Layer ◽  
Linear Regression Analysis ◽  
Optical Absorption Spectroscopy ◽  
Near Surface ◽  
Pollution Levels ◽  
Mixing Ratios ◽  
Tropospheric No2

Abstract. Nitrogen dioxide (NO2), produced as a result of fossil fuel combustion, biomass burning, lightning, and soil emissions, is a key urban and rural tropospheric pollutant. In this case study, ground-based remote sensing has been coupled with the in situ network in Vienna, Austria, to investigate NO2 distributions in the planetary boundary layer. Near-surface and path-averaged NO2 mixing ratios within the metropolitan area of Vienna are estimated from car DOAS (differential optical absorption spectroscopy) zenith-sky and tower DOAS horizon observations. The latter configuration is innovative in the sense that it obtains horizontal measurements at more than a hundred different azimuthal angles – within a 360∘ rotation taking less than half an hour. Spectral measurements were made with a DOAS instrument on nine days in April, September, October, and November 2015 in the zenith-sky mode and on five days in April and May 2016 in the off-axis mode. The analysis of tropospheric NO2 columns from the car measurements and O4 normalized NO2 path averages from the tower observations provide interesting insights into the spatial and temporal NO2 distribution over Vienna. Integrated column amounts of NO2 from both DOAS-type measurements are converted into mixing ratios by different methods. The estimation of near-surface NO2 mixing ratios from car DOAS tropospheric NO2 vertical columns is based on a linear regression analysis including mixing height and other meteorological parameters that affect the dilution and reactivity in the planetary boundary layer – a new approach for such conversion. Path-averaged NO2 mixing ratios are calculated from tower DOAS NO2 slant column densities by taking into account topography and geometry. Overall, lap averages of near-surface NO2 mixing ratios obtained from car DOAS zenith-sky measurements, around a circuit in Vienna, are in the range of 3.8 to 26.1 ppb and in good agreement with values obtained from in situ NO2 measurements for days with wind from the southeast. Path-averaged NO2 mixing ratios at 160 m above the ground as derived from the tower DOAS measurements are between 2.5 and 9 ppb on two selected days with different wind conditions and pollution levels and show similar spatial distribution as seen in the car DOAS zenith-sky observations. We conclude that the application of the two methods to obtain near-surface and path-averaged NO2 mixing ratios is promising for this case study.

scholarly journals Near-surface and path-averaged mixing ratios of NO<sub>2</sub> derived from car DOAS zenith-sky and tower DOAS off-axis measurements in Vienna: a case study

2018 ◽  
Author(s):  
Stefan F. Schreier ◽  
Andreas Richter ◽  
John P. Burrows
Keyword(s):  
Boundary Layer ◽  
Planetary Boundary Layer ◽  
Linear Regression Analysis ◽  
Optical Absorption Spectroscopy ◽  
Near Surface ◽  
Pollution Levels ◽  
Mixing Ratios ◽  
Tropospheric No2

Abstract. Nitrogen dioxide (NO2), produced as a result of fossil fuel combustion, biomass burning, lightning, and soil emissions, is a key urban and rural tropospheric pollutant. In this case study, ground-based remote sensing has been coupled with the in situ network in Vienna, Austria, to investigate NO2 distributions in the planetary boundary layer. Near-surface and path-averaged NO2 mixing ratios within the metropolitan area of Vienna are estimated from car DOAS (Differential Optical Absorption Spectroscopy) zenith-sky and tower DOAS horizon observations. The latter configuration is innovative in the sense that it obtains horizontal measurements at more than hundred different azimuthal angles – within a 360° rotation taking less than half an hour. Spectral measurements were made with a DOAS instrument on nine days in April, September, October, and November 2015 in the zenith-sky mode and on five days in April and May 2016 in the off-axis mode. The analysis of tropospheric NO2 columns from the car measurements and O4 normalized NO2 path averages from the tower observations provide interesting insights into the spatial and temporal NO2 distribution over Vienna. Integrated column amounts of NO2 from both DOAS-type measurements are converted into mixing ratios by different methods. The estimation of near-surface NO2 mixing ratios from car DOAS tropospheric NO2 vertical columns is based on a linear regression analysis including mixing-height and other meteorological parameters that affect the dilution and reactivity in the planetary boundary layer – a new approach for such conversion. Path-averaged NO2 mixing ratios are calculated from tower DOAS NO2 slant column densities by taking into account topography and geometry. Overall, lap averages of near-surface NO2 mixing ratios obtained from car DOAS zenith-sky measurements, around a circuit in Vienna, are in the range of 3.8 to 26.2 ppb and in good agreement with values obtained from in situ NO2 measurements for days with wind from the Southeast. Path-averaged NO2 mixing ratios at 160 m above the ground as derived from the tower DOAS measurements are between 2.5 and 9 ppb on two selected days with different wind conditions and pollution levels and show similar spatial distribution as seen in the car DOAS zenith-sky observations. We conclude that the application of the two methods to obtain near-surface and path-averaged NO2 mixing ratios is promising for this case study.

scholarly journals Ambient measurements of aromatic and oxidized VOCs by PTR-MS and GC-MS: intercomparison between four instruments in a boreal forest in Finland

2015 ◽  
Vol 8 (10) ◽  
pp. 4453-4473 ◽  
Author(s):  
M. K. Kajos ◽  
P. Rantala ◽  
M. Hill ◽  
H. Hellén ◽  
J. Aalto ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Boreal Forest ◽  
Proton Transfer Reaction ◽  
Systematic Difference ◽  
Gas Chromatography Mass Spectrometry ◽  
Forest Site ◽  
Mixing Ratios ◽  
Measurement Protocol ◽  
R Value

Abstract. Proton transfer reaction mass spectrometry (PTR-MS) and gas chromatography mass spectrometry GC-MS) are commonly used methods for automated in situ measurements of various volatile organic compounds (VOCs) in the atmosphere. In order to investigate the reliability of such measurements, we operated four automated analyzers using their normal field measurement protocol side by side at a boreal forest site. We measured methanol, acetaldehyde, acetone, benzene and toluene by two PTR-MS and two GC-MS instruments. The measurements were conducted in southern Finland between 13 April and 14 May 2012. This paper presents correlations and biases between the concentrations measured using the four instruments. A very good correlation was found for benzene and acetone measurements between all instruments (the mean R value was 0.88 for both compounds), while for acetaldehyde and toluene the correlation was weaker (with a mean R value of 0.50 and 0.62, respectively). For some compounds, notably for methanol, there were considerable systematic differences in the mixing ratios measured by the different instruments, despite the very good correlation between the instruments (mean R = 0.90). The systematic difference manifests as a difference in the linear regression slope between measurements conducted between instruments, rather than as an offset. This mismatch indicates that the systematic uncertainty in the sensitivity of a given instrument can lead to an uncertainty of 50–100 % in the methanol emissions measured by commonly used methods.

scholarly journals Tracer measurements in the tropical tropopause layer during the AMMA/SCOUT-O3 aircraft campaign

2010 ◽  
Vol 10 (8) ◽  
pp. 3615-3627 ◽  
Author(s):  
C. D. Homan ◽  
C. M. Volk ◽  
A. C. Kuhn ◽  
A. Werner ◽  
J. Baehr ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Deep Convection ◽  
Transport Processes ◽  
Gradual Transition ◽  
Tropical Tropopause Layer ◽  
Mixing Ratios ◽  
Tropical Tropopause ◽  
Multidisciplinary Analysis ◽  
The Tropics

Abstract. We present airborne in situ measurements made during the AMMA (African Monsoon Multidisciplinary Analysis)/SCOUT-O3 campaign between 31 July and 17 August 2006 on board the M55 Geophysica aircraft, based in Ouagadougou, Burkina Faso. CO2 and N2O were measured with the High Altitude Gas Analyzer (HAGAR), CO was measured with the Cryogenically Operated Laser Diode (COLD) instrument, and O3 with the Fast Ozone ANalyzer (FOZAN). We analyse the data obtained during five local flights to study the dominant transport processes controlling the tropical tropopause layer (TTL, here ~350–375 K) and lower stratosphere above West-Africa: deep convection up to the level of main convective outflow, overshooting of deep convection, and horizontal inmixing across the subtropical tropopause. Besides, we examine the morphology of the stratospheric subtropical barrier. Except for the flight of 13 August, distinct minima in CO2 mixing ratios indicate convective outflow of boundary layer air in the TTL. The CO2 profiles show that the level of main convective outflow was mostly located at potential temperatures between 350 and 360 K, and for 11 August reached up to 370 K. While the CO2 minima indicate quite significant convective influence, the O3 profiles suggest that the observed convective signatures were mostly not fresh, but of older origin (several days or more). When compared with the mean O3 profile measured during a previous campaign over Darwin in November 2005, the O3 minimum at the main convective outflow level was less pronounced over Ouagadougou. Furthermore O3 mixing ratios were much higher throughout the whole TTL and, unlike over Darwin, rarely showed low values observed in the regional boundary layer. Signatures of irreversible mixing following overshooting of convective air were scarce in the tracer data. Some small signatures indicative of this process were found in CO2 profiles between 390 and 410 K during the flights of 4 and 8 August, and in CO data at 410 K on 7 August. However, the absence of expected corresponding signatures in other tracer data makes this evidence inconclusive, and overall there is little indication from the observations that overshooting convection has a profound impact on gas-phase tracer TTL composition during AMMA. We find the amount of photochemically aged air isentropically mixed into the TTL across the subtropical tropopause to be not significant. Using the N2O observations we estimate the fraction of aged extratropical stratospheric air in the TTL to be 0.0±0.1 up to 370 K during the local flights. Above the TTL this fraction increases to 0.3±0.1 at 390 K. The subtropical barrier, as indicated by the slope of the correlation between N2O and O3 between 415 and 490 K, does not appear as a sharp border between the tropics and extratropics, but rather as a gradual transition region between 10° N and 25° N where isentropic mixing between these two regions may occur.

scholarly journals Fluxes and concentrations of volatile organic compounds above central London, UK

2009 ◽  
Vol 9 (4) ◽  
pp. 17297-17333 ◽  
Author(s):  
B. Langford ◽  
E. Nemitz ◽  
E. House ◽  
G. J. Phillips ◽  
D. Famulari ◽  
...  
Keyword(s):  
Volatile Organic Compounds ◽  
Organic Compounds ◽  
Transfer Reaction ◽  
Proton Transfer Reaction ◽  
Traffic Density ◽  
Mixing Ratios ◽  
Oxygenated Compounds ◽  
Volatile Organic ◽  
Benzene Toluene ◽  
The Uk

Abstract. Concentrations and fluxes of eight volatile organic compounds (VOCs) were measured during October 2006 from a high telecom tower above central London, as part of the CityFlux contribution to the REPARTEE I campaign. A continuous flow disjunct eddy covariance technique with analysis by proton transfer reaction mass spectrometry was used. Daily averaged VOC mixing ratios were within the range 1–19 ppb for the oxygenated compounds (methanol, acetaldehyde and acetone) and 0.2–1.3 ppb for the aromatics (benzene, toluene and ethylbenzene). Typical VOC fluxes were in the range 0.1–1.0 mg m−2 h−1. There was a non-linear relationship between VOC fluxes and traffic density for most of the measured compounds. Traffic activity was estimated to account for approximately 70% of the aromatic compound fluxes, whereas non-traffic related sources were found to be more important for methanol and isoprene fluxes. The measured fluxes were comparable to the estimates of the UK national atmospheric emission inventory for the aromatic VOCs and CO. In contrast, fluxes of the oxygenated compounds were about three times larger than inventory estimates. For isoprene and acetonitrile this difference was many times larger. At temperatures over 25°C it is estimated that more than half the isoprene observed in central London is of biogenic origin.

scholarly journals In situ measurements of molecular iodine in the marine boundary layer: the link to macroalgae and the implications for O<sub>3</sub>, IO, OIO and NO<sub>x</sub>

2010 ◽  
Vol 10 (1) ◽  
pp. 361-390
Author(s):  
R.-J. Huang ◽  
K. Seitz ◽  
J. Buxmann ◽  
D. Poehler ◽  
K. E. Hornsby ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Marine Boundary Layer ◽  
Single Point ◽  
Molecular Iodine ◽  
In Situ Measurements ◽  
Gas Chromatography Mass Spectrometry ◽  
Optical Absorption Spectroscopy ◽  
Mixing Ratios ◽  
Concentration Levels

Abstract. "Single-point" in situ measurements of molecular iodine (I2) were carried out in the coastal marine boundary layer (MBL) using diffusion denuders in combination with a gas chromatography-mass spectrometry (GC-MS) method. Comparison measurements were taken at Mace Head and Mweenish Bay, on the West Coast of Ireland. The observed mixing ratios of I2 at Mweenish Bay are much higher than that at Mace Head, indicating the emissions of I2 are correlated with the local algal biomass density and algae species. The concentration levels of I2 were found to correlate inversely with tidal height and correlate positively with the concentration levels of O3 in the surrounding air. However, the released I2 can also lead to O3 destruction via the reaction of O3 with iodine atoms that are formed by the photolysis of I2 during the day and via the reaction of I2 with NOx at night. IO and OIO were measured by long-path differential optical absorption spectroscopy (LP-DOAS). The results show that the concentrations of both daytime and nighttime IO are correlated with the mixing ratios of I2. OIO was observed not only during the day but also, for the first time at both Mace Head and Mweenish Bay, at night. In addition, I2 was measured simultaneously by the LP-DOAS technique and compared with the "single-point" in situ measurement. The results suggest that the local algae sources dominate the inorganic iodine chemistry at Mace Head and Mweenish Bay.

scholarly journals Sources and Characteristics of Summertime Organic Aerosol in the Colorado Front Range: Perspective from Measurements and WRF-Chem Modeling

2018 ◽  
Author(s):  
Roya Bahreini ◽  
Ravan Ahmadov ◽  
Stu A. McKeen ◽  
Kennedy T. Vu ◽  
Justin H. Dingle ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Organic Aerosol ◽  
Colorado Front Range ◽  
Weather Research And Forecasting ◽  
Front Range ◽  
Top Down ◽  
Mixing Ratios ◽  
Oil And Natural Gas ◽  
The Mean

Abstract. Evolution of organic aerosol (OA) and their precursors in the boundary layer of Colorado Front Range during the Front Range Air Pollution and Photochemistry Éxperiment (FRAPPÉ, July–August 2014) was analyzed by in-situ measurements and chemical transport modeling. Measurements indicated significant production of secondary OA (SOA), with enhancement ratio of OA with respect to carbon monoxide (CO) reaching 0.068 ± 0.004 μg m−3 ppbv−1. At background mixing ratios of CO, up to ~ 2 μg m−3 background OA was observed, suggesting significant non-combustion contribution to OA in the Front Range. The mean concentration of OA in plumes with a high influence of oil and natural gas (O&amp;G) emissions was ~ 40 % higher than in urban-influenced plumes. Positive matrix factorization confirmed a dominant contribution of secondary, oxygenated OA (OOA) in the boundary layer instead of fresh, hydrocarbon-like OA (HOA). Combinations of primary OA (POA) volatility assumptions, aging of semi-volatile species, and different emission estimates from the O&amp;G sector were used in the Weather Research and Forecasting model, coupled with Chemistry (WRF-Chem) simulation scenarios. The assumption of semi-volatile POA resulted in greater than a factor of 10 lower POA concentrations compared to PMF-resolved HOA. Including a top-down modified O&amp;G emissions resulted in substantially better agreements in modeled ethane, toluene, hydroxyl radical, and ozone compared to measurements in the high O&amp;G-influenced plumes. By including emissions from the O&amp;G sector using the top-down approach, it was estimated that the O&amp;G sector contributed to

scholarly journals New insights in the global cycle of acetonitrile: release from theocean and dry deposition in the tropical savanna of Venezuela

2004 ◽  
Vol 4 (1) ◽  
pp. 275-280 ◽  
Author(s):  
E. Sanhueza ◽  
R. Holzinger ◽  
B. Kleiss ◽  
L. Donoso ◽  
P. J. Crutzen
Keyword(s):  
Boundary Layer ◽  
Biomass Burning ◽  
Dry Deposition ◽  
Mixed Boundary ◽  
Deposition Velocity ◽  
Caribbean Sea ◽  
Proton Transfer Reaction ◽  
Wet Season ◽  
Mixing Ratios ◽  
The Caribbean

Abstract. Using the proton transfer reaction mass spectrometry (PTR-MS) technique, acetonitrile was measured during the wet season in a Venezuelan woodland savanna. The site was located downwind of the Caribbean Sea and no biomass burning events were observed in the region. High boundary layer concentrations of 211±36pmol/mol (median, ±standard deviation) were observed during daytime in the well mixed boundary layer, which is about 60pmol/mol above background concentrations recently measured over the Mediterranean Sea and the Pacific Ocean. Most likely acetonitrile is released from the warm waters of the Caribbean Sea thereby enhancing mixing ratios over Venezuela. Acetonitrile concentrations will probably still be much higher in biomass burning plumes, however, the general suitability of acetonitrile as a biomass burning marker should be treated with care. During nights, acetonitrile dropped to levels typically around 120pmol/mol, which is consistent with a dry deposition velocity of 0.14cm/s when a nocturnal boundary layer height of 100m is assumed.

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