scholarly journals Efficient N<sub>2</sub>O<sub>5</sub> Uptake and NO<sub>3</sub> Oxidation in the Outflow of Urban Beijing

2018 ◽  
Author(s):  
Haichao Wang ◽  
Keding Lu ◽  
Song Guo ◽  
Zhijun Wu ◽  
Dongjie Shang ◽  
...  
Keyword(s):  
Field Studies ◽  
Organic Nitrates ◽  
Air Masses ◽  
Dinitrogen Pentoxide ◽  
Nitryl Chloride ◽  
The North ◽  
Initial Reduction ◽  
Heterogeneous Processes ◽  
Volatile Organic ◽  
Ratio Condition

Abstract. Nocturnal reactive nitrogen compounds are important for understanding regional air pollution. Here we present the measurements of dinitrogen pentoxide (N2O5) associated with nitryl chloride (ClNO2) and particulate nitrate (pNO3−) in a suburban site of Beijing in the summer of 2016. High levels of N2O5 and ClNO2 were observed in the outflow of the urban Beijing air masses, with 1-min average maxima of 937 pptv and 2.9 ppbv, respectively. The N2O5 uptake coefficients, γ, and ClNO2 yield, f, were experimentally determined from the observed parameters. The N2O5 uptake coefficient ranged from 0.012 to 0.055, with an average of 0.034 ± 0.018, which is in the upper range of previous field studies reported in North America and Europe but is a moderate value in the North China Plain (NCP), which reflects efficient N2O5 heterogeneous processes in Beijing. The ClNO2 yield exhibited high variability, with a range of 0.50 to unity and an average of 0.73 ± 0.25. The nighttime nitrate radical (NO3) was calculated assuming that the thermal equilibrium between NO3 and N2O5 was maintained. In NO2-rich air masses, the oxidation of nocturnal biogenic volatile organic compounds (BVOCs) was dominated by NO3 rather than O2. The production rate of organic nitrates (ONs) via NO2+BVOCs was significant, with an average of 0.11 ± 0.09 ppbv h−1. We highlight the importance of NO2 oxidation of VOCs in the formation of ONs and subsequent secondary organic aerosols in summer in Beijing. The capacities of BVOCs oxidation and ONs formation are maximized and independent of NOx under a high NOx/BVOCs ratio condition (>10), which indicates that the initial reduction of the NOx emission cannot help reduce the nocturnal formation of ONs.

scholarly journals Efficient N<sub>2</sub>O<sub>5</sub> uptake and NO<sub>3</sub> oxidation in the outflow of urban Beijing

2018 ◽  
Vol 18 (13) ◽  
pp. 9705-9721 ◽  
Author(s):  
Haichao Wang ◽  
Keding Lu ◽  
Song Guo ◽  
Zhijun Wu ◽  
Dongjie Shang ◽  
...  
Keyword(s):  
North China Plain ◽  
North China ◽  
Field Studies ◽  
Organic Nitrate ◽  
Air Masses ◽  
Dinitrogen Pentoxide ◽  
Nitryl Chloride ◽  
The North ◽  
Heterogeneous Processes ◽  
Volatile Organic

Abstract. Nocturnal reactive nitrogen compounds play an important role in regional air pollution. Here we present the measurements of dinitrogen pentoxide (N2O5) associated with nitryl chloride (ClNO2) and particulate nitrate (pNO3-) at a suburban site of Beijing in the summer of 2016. High levels of N2O5 and ClNO2 were observed in the outflow of the urban Beijing air masses, with 1 min average maxima of 937 and 2900 pptv, respectively. The N2O5 uptake coefficients, γ, and ClNO2 yield, f, were experimentally determined from the observed parameters. The N2O5 uptake coefficient ranged from 0.012 to 0.055, with an average of 0.034 ± 0.018, which is in the upper range of previous field studies reported in North America and Europe but is a moderate value in the North China Plain (NCP), which reflects efficient N2O5 heterogeneous processes in Beijing. The ClNO2 yield exhibited high variability, with a range of 0.50 to unity and an average of 0.73 ± 0.25. The concentration of the nitrate radical (NO3) was calculated assuming that the thermal equilibrium between NO3 and N2O5 was maintained. In NOx-rich air masses, the oxidation of nocturnal biogenic volatile organic compounds (BVOCs) was dominated by NO3 rather than O3. The production rate of organic nitrate (ON) via NO3 + BVOCs was significant, with an average of 0.10 ± 0.07 ppbv h−1. We highlight the importance of NO3 oxidation of VOCs in the formation of ON and subsequent secondary organic aerosols in summer in Beijing.

scholarly journals Importance of biogenic volatile organic compounds to acyl peroxy nitrates (APN) production in the southeastern US during SOAS 2013

2019 ◽  
Vol 19 (3) ◽  
pp. 1867-1880 ◽  
Author(s):  
Shino Toma ◽  
Steve Bertman ◽  
Christopher Groff ◽  
Fulizi Xiong ◽  
Paul B. Shepson ◽  
...  
Keyword(s):  
Volatile Organic Compounds ◽  
Gas Phase ◽  
Organic Compounds ◽  
Model Simulation ◽  
Statistical Correlation ◽  
Organic Nitrates ◽  
Biogenic Volatile Organic Compounds ◽  
The North ◽  
Southeastern Us ◽  
Volatile Organic

Abstract. Gas-phase atmospheric concentrations of peroxyacetyl nitrate (PAN), peroxypropionyl nitrate (PPN), and peroxymethacryloyl nitrate (MPAN) were measured on the ground using a gas chromatograph electron capture detector (GC-ECD) during the Southern Oxidants and Aerosols Study (SOAS) 2013 campaign (1 June to 15 July 2013) in Centreville, Alabama, in order to study biosphere–atmosphere interactions. Average levels of PAN, PPN, and MPAN were 169, 5, and 9 pptv, respectively, and the sum accounts for an average of 16 % of NOy during the daytime (10:00 to 16:00 local time). Higher concentrations were seen on average in air that came to the site from the urban NOx sources to the north. PAN levels were the lowest observed in ground measurements over the past two decades in the southeastern US. A multiple regression analysis indicates that biogenic volatile organic compounds (VOCs) account for 66 % of PAN formation during this study. Comparison of this value with a 0-D model simulation of peroxyacetyl radical production indicates that at least 50 % of PAN formation is due to isoprene oxidation. MPAN has a statistical correlation with isoprene hydroxynitrates (IN). Organic aerosol mass increases with gas-phase MPAN and IN concentrations, but the mass of organic nitrates in particles is largely unrelated to MPAN.

scholarly journals Production of N<sub>2</sub>O<sub>5</sub> and ClNO<sub>2</sub> in summer in urban Beijing, China

2018 ◽  
Vol 18 (16) ◽  
pp. 11581-11597 ◽  
Author(s):  
Wei Zhou ◽  
Jian Zhao ◽  
Bin Ouyang ◽  
Archit Mehra ◽  
Weiqi Xu ◽  
...  
Keyword(s):  
Urban Areas ◽  
Product Formation ◽  
High Reactivity ◽  
Ionization Mass ◽  
Dinitrogen Pentoxide ◽  
Mixing Ratios ◽  
Nitryl Chloride ◽  
Volatile Organic ◽  
Beijing China ◽  
Hydrolysis Of

Abstract. The heterogeneous hydrolysis of dinitrogen pentoxide (N2O5) has a significant impact on both nocturnal particulate nitrate formation and photochemistry on the following day through the photolysis of nitryl chloride (ClNO2), yet these processes in highly polluted urban areas remain poorly understood. Here we present measurements of gas-phase N2O5 and ClNO2 by high-resolution time-of-flight chemical ionization mass spectrometer (ToF-CIMS) during summer in urban Beijing, China as part of the Air Pollution and Human Health (APHH) campaign. N2O5 and ClNO2 show large day-to-day variations with average (±1σ) mixing ratios of 79.2±157.1 and 174.3±262.0 pptv, respectively. High reactivity of N2O5, with τ (N2O5)−1 ranging from 0.20 × 10−2 to 1.46 × 10−2 s−1, suggests active nocturnal chemistry and a large nocturnal nitrate formation potential via N2O5 heterogeneous uptake. The lifetime of N2O5, τ (N2O5), decreases rapidly with the increase in aerosol surface area, yet it varies differently as a function of relative humidity with the highest value peaking at ∼ 40 %. The N2O5 uptake coefficients estimated from the product formation rates of ClNO2 and particulate nitrate are in the range of 0.017–0.19, corresponding to direct N2O5 loss rates of 0.00044–0.0034 s−1. Further analysis indicates that the fast N2O5 loss in the nocturnal boundary layer in urban Beijing is mainly attributed to its indirect loss via NO3, for example through the reactions with volatile organic compounds and NO, while the contribution of the heterogeneous uptake of N2O5 is comparably small (7–33 %). High ClNO2 yields ranging from 0.10 to 0.35 were also observed, which might have important implications for air quality by affecting nitrate and ozone formation.

scholarly journals 668 The Consequences to Emergency Surgery During COVID19 Pandemic in a UK District General Hospital in The North East of England

2021 ◽  
Vol 108 (Supplement_2) ◽  
Author(s):  
R Evans ◽  
C Ng
Keyword(s):  
Surgical Treatment ◽  
General Hospital ◽  
Emergency Surgery ◽  
Early Identification ◽  
District General Hospital ◽  
Public Confidence ◽  
Surgical Services ◽  
North East ◽  
The North ◽  
Initial Reduction

Abstract Aim COVID19 pandemic has significantly affected surgical services. We aim to review its effects on our theatre output and risk of encountering COVID 19 cases. Method Serial record of operations performed locally were reviewed from start of UK COVID19 pandemic lockdown on 23rd March 2020 to 13th July 2020 after it was lifted. A weekly average by month of operations and the percentage of COVID19 cases diagnosed within 30 days of the procedure were noted. Results 733 operations performed through this period. In March, 33 operations/week performed, 88.4% emergency and 7% diagnosed with COVID19. April, 31 operations /week performed, 95.9% emergency and 10.6% diagnosed with COVID19. May 46 operations /week performed, 94.5% emergency and 3.3% diagnosed with COVID19. June 56 operations /week, 80.9% emergency and less than 0.01% diagnosed with COVID19. By July 80 operations/week, 59.4% emergency and none diagnosed with COVID 19. Since testing capacity increased, only 6 of the 27 operated were diagnosed with COVID19. Conclusions There was initial reduction to non-emergency workload. However, this has gradually shifted as protocols are in place improve public confidence to return for surgical treatment. Mandatory admission testing allows early identification and remains essential for planning of services and protecting the workforce.

scholarly journals Vitality Structure of the Populations of Vegetative Motile Plants of Forest Ecosystems of the North-East of Ukraine

2019 ◽  
Vol 13 (1) ◽  
pp. 125-132
Author(s):  
Kovalenko Ihor ◽  
Skliar Iurii ◽  
Klymenko Hanna ◽  
Kovalenko Nataliia
Keyword(s):  
Quality Index ◽  
Forest Ecosystems ◽  
Morphological Structure ◽  
Field Studies ◽  
Complete Analysis ◽  
Individual Plant ◽  
North East ◽  
The North ◽  
Motile Species ◽  
Two Populations

Background: The vitality level of the populations has turned out to be statistically reliably associated with such coenotic factors: age and density of forest stand. In general, the vitality spectra vary widely: the quality index Q of the populations ranges from 0,00 to 0,50, that is, it fully covers the theoretically possible scale of the values of this coefficient, which indicates the sensitivity of the vitality structure of the populations to the ecological-coenotic conditions and determines high informative value of the vitality analysis. Objective: The aim of the study is to assess the vitality structure of the populations of vegetative motile plant species – typical representatives of the grassy layer of forest ecosystems of the North-East of Ukraine as a factor that determines their stability and dynamics. Methods: The analysis of the vitality structure is based on the field studies of the populations of 4 vegetative motile species of plants – Aegopodium podagraria L., Asarum europaeum L., Carex pilosa Scop. and Stellaria holostea L. in forest ecosystems of the North-East of Ukraine. Vitality analysis was carried out according to Yu. A. Zlobin’s methodology. Vitality analysis procedure, classically, is carried out in three stages: 1) Selection of quantitative features that characterize the vital status of the individual plant; 2) Evaluation of vitality of individual plants that were included in the sample; 3) Integral assessment of the population’s vitality. Depending on the ratio in the population of plants of classes a, b and c, the population belongs to one of three vitality types: prosperous, equilibrium or depressive. Results: The obtained estimates of the vitality structure of populations of the clone-forming plants in the grass-shrub layer of forests of the North-East of Ukraine can be considered quite reliable, because they are based, in general, on a complete analysis of the morphological structure of about 13 thousand ramets of the studied species of plants. The statistical reliability of estimates of the population’s vitality structure is predominantly between 70 and 99% and only in some cases lower than 70%. As the clone grows older, its ramet’s vitality decreases and the clone degrades. New young clones, that start to form on the basis of genets, replace old ones. Such ramets have increased vitality, greater stress and competitive resistance. Due to the mechanisms of clone substitution in the living cover, the dominance of nemoralis herbs persists for a long time. Conclusion: The vitality spectra of the populations of the studied species of plants vary widely: the quality index Q of the populations ranges from 0,00 to 0,50, that is, it covers full theoretically possible scale of the values of this coefficient, which indicates the sensitivity of the vitality structure of the populations to the ecological-coenotic conditions and determines high informative value of vitality analysis. Prosperous populations: two populations A. europaeum of the associations Quercetum (roboris) coryloso (avellanae) – convallariosum (majalis) and Quercetum (roboris) coryloso (avellanae) – convallariosum (majalis), two populations A. podagraria of the associations – Pinetum (sylvestris) vacciniosum (myrtilli) and Querceto (roboris) – Pinetum (sylvestris) convallarioso (majalis) – vacciniosum (myrtilli), one population S. holostea of the association Querceto (roboris) – Pinetum (sylvestris) vacciniosum (myrtilli) and one population C. pilosa of the association Querceto (roboris) – Pinetum (sylvestris) vaccinioso (myrtilli) – convallariosum (majalis).

scholarly journals Diel peroxy radicals in a semi industrial coastal area: nighttime formation of free radicals

2012 ◽  
Vol 12 (8) ◽  
pp. 19529-19570 ◽  
Author(s):  
M. D. Andrés-Hernández ◽  
D. Kartal ◽  
J. N. Growley ◽  
V. Sinha ◽  
E. Regelin ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Trace Gases ◽  
Peroxy Radical ◽  
Industrial Area ◽  
Diurnal Variations ◽  
Peroxy Radicals ◽  
Industrial Emissions ◽  
Air Masses ◽  
Volatile Organic ◽  
Organic Trace

Abstract. Peroxy radicals were measured by a PeRCA (Peroxy Radical Chemical Amplifier) instrument in the boundary layer during the DOMINO (Diel Oxidant Mechanisms In relation to Nitrogen Oxides) campaign at a coastal, forested site influenced by urban-industrial emissions in Southern Spain in late autumn. Total peroxy radicals (RO2* = HO2 + ΣRO2) generally showed a daylight maximum between 10 and 50 pptv at 13:00 UTC, with an average of 18 pptv over the 15 days of measurements. Emissions from the industrial area of Huelva often impacted the measurement site at night during the campaign. The processing of significant levels of anthropogenic organics leads to an intense nocturnal radical chemistry accompanied by formation of organic peroxy radicals at comparable levels to those of summer photochemical conditions with peak events up to 60–80 pptv. The RO2 production initiated by reactions of NO3 with organic trace gases was estimated to be significant but not sufficient to account for the concentrations of RO2* observed in air masses carrying high pollutant loading. The nocturnal production of peroxy radicals seems therefore to be dominated by ozonolysis of volatile organic compounds. RO2* diurnal variations were consistent with other HO2 measurements available at the site. HO2/RO2* ratios generally varied between 0.3 and 0.4 in all wind directions. Occasional HO2/RO2* ≥ 1 seemed to be associated with periods of high RO2* variability and with RO2 interferences in the HO2 measurement in air masses with high RO2 load.

scholarly journals Urban inland wintertime N<sub>2</sub>O<sub>5</sub> and ClNO<sub>2</sub> influenced by snow-covered ground, air turbulence, and precipitation

2021 ◽  
Author(s):  
Kathryn D. Kulju ◽  
Stephen M. McNamara ◽  
Qianjie Chen ◽  
Jacinta Edebeli ◽  
Jose D. Fuentes ◽  
...  
Keyword(s):  
Ground Cover ◽  
Atmospheric Particulate Matter ◽  
Ionization Mass ◽  
Bare Ground ◽  
Near Surface ◽  
Dinitrogen Pentoxide ◽  
Nitryl Chloride ◽  
Air Turbulence ◽  
Chlorine Radicals ◽  
Wet Scavenging

Abstract. The atmospheric multiphase reaction of dinitrogen pentoxide (N2O5) with chloride-containing aerosol particles produces nitryl chloride (ClNO2), which has been observed across the globe. The photolysis of ClNO2 produces chlorine radicals and nitrogen dioxide (NO2), which alter pollutant fates and air quality. However, the effects of local meteorology on near-surface ClNO2 production are not yet well understood, as most observational and modeling studies focus on periods of clear conditions. During a field campaign in Kalamazoo, Michigan from January–February 2018, N2O5 and ClNO2 were measured using chemical ionization mass spectrometry, with simultaneous measurements of atmospheric particulate matter and meteorological parameters. We examine the impacts of atmospheric turbulence, precipitation (snow, rain) and fog, and ground cover (snow-covered and bare ground) on the abundances of ClNO2 and N2O5. N2O5 mole ratios were lowest during periods of lower turbulence and were not statistically significantly different between snow-covered and bare ground. In contrast, ClNO2 mole ratios were highest, on average, over snow-covered ground, due to saline snowpack ClNO2 production. Both N2O5 and ClNO2 mole ratios were lowest, on average, during rainfall and fog because of scavenging, with N2O5 scavenging by fog droplets likely contributing to observed increased particulate nitrate concentrations. These observations, specifically those during active precipitation and with snow-covered ground, highlight important processes, including N2O5 and ClNO2 wet scavenging, fog nitrate production, and snowpack ClNO2 production, that govern the variability in observed atmospheric chlorine and nitrogen chemistry and are missed when considering only clear conditions.

scholarly journals Climatic influence on the composition of snow cover at Austre Okstindbreen, Norway, 1989 and 1990

1994 ◽  
Vol 19 ◽  
pp. 1-6 ◽  
Author(s):  
He Yuanqing ◽  
Wilfred H. Theakstone
Keyword(s):  
Snow Cover ◽  
North Atlantic ◽  
Early Summer ◽  
Late Winter ◽  
Crustal Material ◽  
Air Masses ◽  
The North ◽  
Air Temperatures ◽  
Winter Snow ◽  
Marine Source

Winter snow cover at Austre Okstindbreen is influenced strongly by patterns of atmospheric circulation, and by air temperatures during precipitation. Differences of circulation over the North Atlantic and Scandinavia during the winters of 1988–89 and 1989–90 were reflected in the ionic and isotopic composition of snow that accumulated at the glacier. Early summer ablation did not remove, or smooth out, all the initial stratigraphic differences. In the first half of the 1988–89 winter, most air masses took a relatively short route between a marine source and Okstindan; late winter snowfalls were from air masses which had taken a longer continental route. The snow that accumulated in the first half of the 1989–90 winter was associated with air masses which had followed longer continental routes, and so brought higher concentrations of impurities from forests, lakes and crustal material. The ablation season began earlier in 1990 than in 1989, and summer winds and rain supplied more impurities to the snowpack surface.

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