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1
Crowley, J. N., G. Schuster, N. Pouvesle, U. Parchatka, H. Fischer, B. Bonn, H. Bingemer, and J. Lelieveld. "Nocturnal nitrogen oxides at a rural mountain-site in South-Western Germany." Atmospheric Chemistry and Physics Discussions 10, no. 1 (January 19, 2010): 1309–53. http://dx.doi.org/10.5194/acpd-10-1309-2010.
Повний текст джерелаАнотація:
Abstract. A new, two-channel instrument for simultaneous NO3 and N2O5 monitoring was used to make the first comprehensive set of nocturnal NOx measurements (NO, NO2, NO3 and N2O5) at the Taunus Observatory, a rural mountain site (Kleiner Feldberg) in South-western Germany. In May 2008, NO3 and N2O5 mixing ratios were well above the instrumental detection limit (a few ppt) on all nights of the campaign and were characterised by large variability resulting from inhomogeneously distributed sinks. The concentrations of NO3, N2O5 and NO2 were consistent with the equilibrium constant, K2, defining the rates of formation and thermal dissociation of N2O5. A steady-state lifetime analysis showed that nocturnal NOx losses were generally dominated by reaction of NO3 with volatile organic compounds in this forested region, with N2O5 uptake to aerosols of secondary importance. Analysis of a limited dataset obtained at high relative humidity indicated that the loss of N2O5 by reaction with water vapour is less efficient (> factor 3) than derived using laboratory kinetic data. The fraction of NOx present as NO3 and N2O5 reached ≈20% on some nights, with night-time losses of NOx competing with daytime losses.
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Crowley, J. N., G. Schuster, N. Pouvesle, U. Parchatka, H. Fischer, B. Bonn, H. Bingemer, and J. Lelieveld. "Nocturnal nitrogen oxides at a rural mountain-site in south-western Germany." Atmospheric Chemistry and Physics 10, no. 6 (March 25, 2010): 2795–812. http://dx.doi.org/10.5194/acp-10-2795-2010.
Повний текст джерелаАнотація:
Abstract. A new, two-channel instrument for simultaneous NO3 and N2O5 monitoring was used to make the first comprehensive set of nocturnal NOx measurements (NO, NO2, NO3 and N2O5) at the Taunus Observatory, a rural mountain site (Kleiner Feldberg) in South-western Germany. In May 2008, NO3 and N2O5 mixing ratios were well above the instrumental detection limit (a few ppt) on all nights of the campaign and were characterised by large variability. The concentrations of NO3, N2O5 and NO2 were consistent with the equilibrium constant, K2, defining the rates of formation and thermal dissociation of N2O5. A steady-state lifetime analysis is consistent with the loss of nocturnal NOx being dominated by the reaction of NO3 with volatile organic compounds in this forested region, with N2O5 uptake to aerosols of secondary importance. Analysis of a limited dataset obtained at high relative humidity indicated that the loss of N2O5 by reaction with water vapour is less efficient (>factor 3) than derived using laboratory kinetic data. The fraction of NOx present as NO3 and N2O5 reached ~20% on some nights, with night-time losses of NOx competing with daytime losses.
3
Delaria, Erin R., Megan Vieira, Julie Cremieux, and Ronald C. Cohen. "Measurements of NO and NO<sub>2</sub> exchange between the atmosphere and <i>Quercus agrifolia</i>." Atmospheric Chemistry and Physics 18, no. 19 (October 5, 2018): 14161–73. http://dx.doi.org/10.5194/acp-18-14161-2018.
Повний текст джерелаАнотація:
Abstract. NO2 foliar deposition through the stomata of leaves has been identified as a significant sink of NOx within a forest canopy. In this study, we investigated NO2 and NO exchange between the atmosphere and the leaves of the native California oak tree Quercus agrifolia using a branch enclosure system. NO2 detection was performed with laser-induced fluorescence (LIF), which excludes biases from other reactive nitrogen compounds and has a low detection limit of 5–50 ppt. We performed both light and dark experiments with concentrations between 0.5 and 10 ppb NO2 and NO under constant ambient conditions. Deposition velocities for NO2 during light and dark experiments were 0.123±0.009 and 0.015±0.001 cm s−1, respectively. Much slower deposition was seen for NO, with deposition velocities of 0.012±0.002 and 0.005±0.002 cm s−1 measured during light and dark experiments, respectively. This corresponded to a summed resistance of the stomata and mesophyll of 6.9±0.9 s cm−1 for NO2 and 140±40 s cm−1 for NO. No significant compensation point was detected for NO2 uptake, but compensation points ranging from 0.74 to 3.8 ppb were observed for NO. NO2 and NO deposition velocities reported here are comparable both with previous leaf-level chamber studies and inferences from canopy-level field measurements. In parallel with these laboratory experiments, we have constructed a detailed 1-D atmospheric model to assess the contribution of leaf-level NOx deposition to the total NOx loss and NOx canopy fluxes. Using the leaf uptake rates measured in the laboratory, these modeling studies suggest that loss of NOx to deposition in a California oak woodland competes with the pathways of HNO3 and RONO2 formation, with deposition making up 3 %–22 % of the total NOx loss. Additionally, foliar uptake of NOx at these rates could account for ∼15 %–30 % canopy reduction of soil NOx emissions.
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Schönauer-Kamin, Daniela, Yongxiang Li, Wojtek Wlodarski, Samuel Ippolito, and Ralf Moos. "2D SnS2—A Material for Impedance-Based Low Temperature NOx Sensing?" Proceedings 1, no. 4 (August 9, 2017): 455. http://dx.doi.org/10.3390/proceedings1040455.
Повний текст джерелаАнотація:
The sensor signal of tin disulfide (SnS2), a two-dimensional (2D) group-IV dichalcogenide, deposited as a film on a conductometric transducer is investigated at 130 °C. The focus is on the detection of the total NOx concentration. Therefore, the sensor response to NO and NO2 at ppm- and sub-ppm level at low operating temperature is determined. The results show that the sensing device provides a high sensor signal to NO and NO2 even at concentrations of only 390 ppb NOx. Both nitrous components, NO and NO2, yield the same signal, which offers the opportunity to sense the total concentration of NOx.
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Friedrich, Nils, Ivan Tadic, Jan Schuladen, James Brooks, Eoghan Darbyshire, Frank Drewnick, Horst Fischer, Jos Lelieveld, and John N. Crowley. "Measurement of NO<sub><i>x</i></sub> and NO<sub><i>y</i></sub> with a thermal dissociation cavity ring-down spectrometer (TD-CRDS): instrument characterisation and first deployment." Atmospheric Measurement Techniques 13, no. 10 (October 29, 2020): 5739–61. http://dx.doi.org/10.5194/amt-13-5739-2020.
Повний текст джерелаАнотація:
Abstract. We present a newly constructed, two-channel thermal dissociation cavity ring-down spectrometer (TD-CRDS) for the measurement of NOx (NO+NO2), NOy (NOx+HNO3+RO2NO2+2N2O5 etc.), NOz (NOy−NOx) and particulate nitrate (pNit). NOy-containing trace gases are detected as NO2 by the CRDS at 405 nm following sampling through inlets at ambient temperature (NOx) or at 850 ∘C (NOy). In both cases, O3 was added to the air sample directly upstream of the cavities to convert NO (either ambient or formed in the 850 ∘C oven) to NO2. An activated carbon denuder was used to remove gas-phase components of NOy when sampling pNit. Detection limits, defined as the 2σ precision for 1 min averaging, are 40 pptv for both NOx and NOy. The total measurement uncertainties (at 50 % relative humidity, RH) in the NOx and NOy channels are 11 %+10 pptv and 16 %+14 pptv for NOz respectively. Thermograms of various trace gases of the NOz family confirm stoichiometric conversion to NO2 (and/or NO) at the oven temperature and rule out significant interferences from NH3 detection (<2 %) or radical recombination reactions under ambient conditions. While fulfilling the requirement of high particle transmission (>80 % between 30 and 400 nm) and essentially complete removal of reactive nitrogen under dry conditions (>99 %), the denuder suffered from NOx breakthrough and memory effects (i.e. release of stored NOy) under humid conditions, which may potentially bias measurements of particle nitrate. Summertime NOx measurements obtained from a ship sailing through the Red Sea, Indian Ocean and Arabian Gulf (NOx levels from <20 pptv to 25 ppbv) were in excellent agreement with those taken by a chemiluminescence detector of NO and NO2. A data set obtained locally under vastly different conditions (urban location in winter) revealed large diel variations in the NOz to NOy ratio which could be attributed to the impact of local emissions by road traffic.
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Martínez Torres, Javier, Jorge Pastor Pérez, Joaquín Sancho Val, Aonghus McNabola, Miguel Martínez Comesaña, and John Gallagher. "A Functional Data Analysis Approach for the Detection of Air Pollution Episodes and Outliers: A Case Study in Dublin, Ireland." Mathematics 8, no. 2 (February 10, 2020): 225. http://dx.doi.org/10.3390/math8020225.
Повний текст джерелаАнотація:
Ground level concentrations of nitrogen oxide (NOx) can act as an indicator of air quality in the urban environment. In cities with relatively good air quality, and where NOx concentrations rarely exceed legal limits, adverse health effects on the population may still occur. Therefore, detecting small deviations in air quality and deriving methods of controlling air pollution are challenging. This study presents different data analytical methods which can be used to monitor and effectively evaluate policies or measures to reduce nitrogen oxide (NOx) emissions through the detection of pollution episodes and the removal of outliers. This method helps to identify the sources of pollution more effectively, and enhances the value of monitoring data and exceedances of limit values. It will detect outliers, changes and trend deviations in NO2 concentrations at ground level, and consists of four main steps: classical statistical description techniques, statistical process control techniques, functional analysis and a functional control process. To demonstrate the effectiveness of the outlier detection methodology proposed, it was applied to a complete one-year NO2 dataset for a sub-urban site in Dublin, Ireland in 2013. The findings demonstrate how the functional data approach improves the classical techniques for detecting outliers, and in addition, how this new methodology can facilitate a more thorough approach to defining effect air pollution control measures.
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Delaria, Erin R., Bryan K. Place, Amy X. Liu, and Ronald C. Cohen. "Laboratory measurements of stomatal NO<sub>2</sub> deposition to native California trees and the role of forests in the NO<sub>x</sub> cycle." Atmospheric Chemistry and Physics 20, no. 22 (November 19, 2020): 14023–41. http://dx.doi.org/10.5194/acp-20-14023-2020.
Повний текст джерелаАнотація:
Abstract. Both canopy-level field measurements and laboratory studies suggest that uptake of NO2 through the leaf stomata of vegetation is a significant sink of atmospheric NOx. However, the mechanisms of this foliar NO2 uptake and their impact on NOx lifetimes remain incompletely understood. To understand the leaf-level processes affecting ecosystem-scale atmosphere–biosphere NOx exchange, we have conducted laboratory experiments of branch-level NO2 deposition fluxes to six coniferous and four broadleaf native California trees using a branch enclosure system with direct laser-induced fluorescence (LIF) detection of NO2. We report NO2 foliar deposition that demonstrates a large degree of inter-species variability, with maximum observed deposition velocities ranging from 0.15 to 0.51 cm s−1 during the daytime, as well as significant stomatal opening during the night. We also find that the contribution of mesophyllic processing to the overall deposition rate of NO2 varies by tree species but has an ultimately inconsequential impact on NOx budgets and lifetimes. Additionally, we find no evidence of any emission of NO2 from leaves, suggesting an effective unidirectional exchange of NOx between the atmosphere and vegetation.
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Alam, Mohammed S., Leigh R. Crilley, James D. Lee, Louisa J. Kramer, Christian Pfrang, Mónica Vázquez-Moreno, Milagros Ródenas, Amalia Muñoz, and William J. Bloss. "Interference from alkenes in chemiluminescent NO<sub><i>x</i></sub> measurements." Atmospheric Measurement Techniques 13, no. 11 (November 10, 2020): 5977–91. http://dx.doi.org/10.5194/amt-13-5977-2020.
Повний текст джерелаАнотація:
Abstract. Nitrogen oxides (NOx=NO+NO2) are critical intermediates in atmospheric chemistry and air pollution. NOx levels control the cycling and hence abundance of the primary atmospheric oxidants OH and NO3 and regulate the ozone production which results from the degradation of volatile organic compounds (VOCs) in the presence of sunlight. They are also atmospheric pollutants, and NO2 is commonly included in air quality objectives and regulations. NOx levels also affect the production of the nitrate component of secondary aerosol particles and other pollutants, such as the lachrymator peroxyacetyl nitrate (PAN). The accurate measurement of NO and NO2 is therefore crucial for air quality monitoring and understanding atmospheric composition. The most commonly used approach for the measurement of NO is the chemiluminescent detection of electronically excited NO2 (NO2∗) formed from the NO + O3 reaction within the NOx analyser. Alkenes, ubiquitous in the atmosphere from biogenic and anthropogenic sources, also react with ozone to produce chemiluminescence and thus may contribute to the measured NOx signal. Their ozonolysis reaction may also be sufficiently rapid that their abundance in conventional instrument background cycles, which also utilises the reaction with ozone, differs from that in the measurement cycle such that the background subtraction is incomplete, and an interference effect results. This interference has been noted previously, and indeed, the effect has been used to measure both alkenes and ozone in the atmosphere. Here we report the results of a systematic investigation of the response of a selection of commercial NOx monitors to a series of alkenes. These NOx monitors range from systems used for routine air quality monitoring to atmospheric research instrumentation. The species-investigated range was from short-chain alkenes, such as ethene, to the biogenic monoterpenes. Experiments were performed in the European PHOtoREactor (EUPHORE) to ensure common calibration and samples for the monitors and to unequivocally confirm the alkene levels present (via Fourier transform infrared spectroscopy – FTIR). The instrument interference responses ranged from negligible levels up to 11 %, depending upon the alkene present and conditions used (e.g. the presence of co-reactants and differing humidity). Such interferences may be of substantial importance for the interpretation of ambient NOx data, particularly for high VOC, low NOx environments such as forests or indoor environments where alkene abundance from personal care and cleaning products may be significant.
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Lee, Jae-Hyeong, Sang-Hyun Lee, and Hyun Cheol Kim. "Detection of Strong NOX Emissions from Fine-scale Reconstruction of the OMI Tropospheric NO2 Product." Remote Sensing 11, no. 16 (August 9, 2019): 1861. http://dx.doi.org/10.3390/rs11161861.
Повний текст джерелаАнотація:
Satellite-retrieved atmospheric NO2 column products have been widely used in assessing bottom-up NOX inventory emissions emitted from large cities, industrial facilities, and power plants. However, the satellite products fail to quantify strong NOX emissions emitted from the sources less than the satellite’s pixel size, with significantly underestimating their emission intensities (smoothing effect). The poor monitoring of the emissions makes it difficult to enforce pollution restriction regulations. This study reconstructs the tropospheric NO2 vertical column density (VCD) of the Ozone Monitoring Instrument (OMI)/Aura (13 × 24 km2 pixel resolution at nadir) over South Korea to a fine-scale product (grid resolution of 3 × 3 km2) using a conservative spatial downscaling method, and investigates the methodological fidelity in quantifying the major Korean area and point sources that are smaller than the satellite’s pixel size. Multiple high-fidelity air quality models of the Weather Research and Forecast-Chemistry (WRF-Chem) and the Weather Research and Forecast/Community Multiscale Air Quality modeling system (WRF/CMAQ) were used to investigate the downscaling uncertainty in a spatial-weight kernel estimate. The analysis results showed that the fine-scale reconstructed OMI NO2 VCD revealed the strong NOX emission sources with increasing the atmospheric NO2 column concentration and enhanced their spatial concentration gradients near the sources, which was accomplished by applying high-resolution modeled spatial-weight kernels to the original OMI NO2 product. The downscaling uncertainty of the reconstructed OMI NO2 product was inherent and estimated by 11.1% ± 10.6% at the whole grid cells over South Korea. The smoothing effect of the original OMI NO2 product was estimated by 31.7% ± 13.1% for the 6 urbanized area sources and 32.2% ± 17.1% for the 13 isolated point sources on an effective spatial resolution that is defined to reduce the downscaling uncertainty. Finally, it was found that the new reconstructed OMI NO2 product had a potential capability in quantifying NOX emission intensities of the isolated strong point sources with a good correlation of R = 0.87, whereas the original OMI NO2 product failed not only to identify the point sources, but also to quantify their emission intensities (R = 0.30). Our findings highlight a potential capability of the fine-scale reconstructed OMI NO2 product in detecting directly strong NOX emissions, and emphasize the inherent methodological uncertainty in interpreting the reconstructed satellite product at a high-resolution grid scale.
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Li, Zhiyan, Renzhi Hu, Pinhua Xie, Hao Chen, Xiaoyan Liu, Shuaixi Liang, Dan Wang, et al. "Simultaneous measurement of NO and NO<sub>2</sub> by a dual-channel cavity ring-down spectroscopy technique." Atmospheric Measurement Techniques 12, no. 6 (June 17, 2019): 3223–36. http://dx.doi.org/10.5194/amt-12-3223-2019.
Повний текст джерелаАнотація:
Abstract. Nitric oxide (NO) and nitrogen dioxide (NO2) are relevant to air quality due to their roles in tropospheric ozone (O3) production. In China, NOx emissions are very high and NOx emissions exhausted from on-road vehicles make up 20 % of total NOx emissions. In order to detect the NO and NO2 emissions on road, a dual-channel cavity ring-down spectroscopy (CRDS) system for NO2 and NO detection has been developed. In the system, NO is converted to NO2 by its reaction with excess O3 in the NOx channel, such that NO can be determined through the difference between two channels. The detection limits of NO2 and NOx for the system are estimated to be about 0.030 (1σ, 1 s) and 0.040 ppb (1σ, 1 s), respectively. Considering the error sources of NO2 absorption cross section and RL determination, the total uncertainty of NO2 measurements is about 5%. The performance of the system was validated against a chemiluminescence (CL) analyser (42i, Thermo Scientific, Inc.) by measuring the NO2 standard mixtures. The measurement results of NO2 showed a linear correction factor (R2) of 0.99 in a slope of 1.031±0.006, with an offset of (-0.940±0.323) ppb. An intercomparison between the system and a cavity-enhanced absorption spectroscopy (CEAS) instrument was also conducted separately for NO2 measurement in an ambient environment. Least-squares analysis showed that the slope and intercept of the regression line are 1.042±0.002 and (-0.393±0.040) ppb, respectively, with a linear correlation factor of R2=0.99. Another intercomparison conducted between the system and the CL analyser for NO detection also showed a good agreement within their uncertainties, with an absolute shift of (0.352±0.013) ppb, a slope of 0.957±0.007 and a correlation coefficient of R2=0.99. The system was deployed on the measurements of on-road vehicle emission plumes in Hefei, and the different emission characteristics were observed in the different areas of the city. The successful deployment of the system has demonstrated that the instrument can provide a new method for retrieving fast variations in NO and NO2 plumes.
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Beirle, Steffen, Christian Borger, Steffen Dörner, Ang Li, Zhaokun Hu, Fei Liu, Yang Wang, and Thomas Wagner. "Pinpointing nitrogen oxide emissions from space." Science Advances 5, no. 11 (November 2019): eaax9800. http://dx.doi.org/10.1126/sciadv.aax9800.
Повний текст джерелаАнотація:
Satellite observations of nitrogen dioxide (NO2) provide valuable information on the location and strength of NOx emissions, but spatial resolution is limited by horizontal transport and smearing of temporal averages due to changing wind fields. In this study, we map NOx emissions on high spatial resolution from TROPOMI observations of NO2 combined with wind fields based on the continuity equation. The divergence of horizontal fluxes proves to be highly sensitive for point sources like exhaust stacks. Thus, NOx emissions from individual power plants can be resolved and quantified even on top of considerably high urban pollution from the Saudi Arabian capital city Riyadh. This allows us to catalog NOx emissions from large point sources globally, as demonstrated for South Africa and Germany, with a detection limit of about 0.11 kg/s down to 0.03 kg/s for ideal conditions.
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Shimizu, Youichi, Satoko Takase, and Daisuke Koba. "A NOx Sensor Based on Solid-Electrolyte Impedance Transducer." Advanced Materials Research 47-50 (June 2008): 479–82. http://dx.doi.org/10.4028/www.scientific.net/amr.47-50.479.
Повний текст джерелаАнотація:
A new solid-electrolyte impedance-metric NOx sensor device composed of a lithium ionic solid electrolyte: Li1.5Al0.5Ti1.5(PO4)3 (LATP) as a transducer and ceramic oxides (perovskite-type oxides, TiO2, SnO2, etc) as a receptor, respectively, have been systematically investigated for the detection of NOx (NO and NO2 ) in the range 10 – 200 ppm at 400 - 500°C. Responses of the sensors were able to divide component between resistance and capacitance, and it was found that the device was applicable to the selective detection of NO or NO2 concentration in each ingredient. Especially, those using TiO2, SnO2 (n-type semiconductor) and perovskite-type oxides (LaCoO3, LaNiO3 and LaCrO3) based receptors gave good responses to NO and NO2. It was also found that the responses were different between n-type or p-type semiconductors, in which we tried to elucidate the sensing mechanism
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Hibino, T. "NOx detection using the electrolysis of water vapour in a YSZ cell Part I. NOx detection." Solid State Ionics 107, no. 3-4 (April 1, 1998): 213–16. http://dx.doi.org/10.1016/s0167-2738(97)00538-9.
Повний текст джерела
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Bauguitte, S. J. B., W. J. Bloss, M. J. Evans, R. A. Salmon, P. S. Anderson, A. E. Jones, J. D. Lee, et al. "Summertime NO<sub>x</sub> measurements during the CHABLIS campaign: can source and sink estimates unravel observed diurnal cycles?" Atmospheric Chemistry and Physics 12, no. 2 (January 19, 2012): 989–1002. http://dx.doi.org/10.5194/acp-12-989-2012.
Повний текст джерелаАнотація:
Abstract. NOx measurements were conducted at the Halley Research Station, coastal Antarctica, during the austral summer period 1 January–10 February 2005. A clear NOx diurnal cycle was observed with minimum concentrations close to instrumental detection limit (5 pptv) measured between 04:00–05:00 GMT. NOx concentrations peaked (24 pptv) between 19:00–20:00 GMT, approximately 5 h after local solar noon. An optimised box model of NOx concentrations based on production from in-snow nitrate photolysis and chemical loss derives a mean noon emission rate of 3.48 × 108 molec cm−2 s−1, assuming a 100 m boundary layer mixing height, and a relatively short NOx lifetime of ~6.4 h. This emission rate compares to directly measured values ranging from 2.1 to 12.6 × 108 molec cm−2 s−1 made on 3 days at the end of the study period. Calculations of the maximum rate of NO2 loss via a variety of conventional HOx and halogen oxidation processes show that the lifetime of NOx is predominantly controlled by halogen processing, namely BrNO3 and INO3 gas-phase formation and their subsequent heterogeneous uptake. Furthermore the presence of halogen oxides is shown to significantly perturb NOx concentrations by decreasing the NO/NO2 ratio. We conclude that in coastal Antarctica, the potential ozone production efficiency of NOx emitted from the snowpack is mitigated by the more rapid NOx loss due to halogen nitrate hydrolysis.
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Bauguitte, S. J. B., W. J. Bloss, M. J. Evans, R. A. Salmon, P. S. Anderson, A. E. Jones, J. D. Lee, et al. "Summertime NO<sub>x</sub> measurements during the CHABLIS campaign: can source and sink estimates unravel observed diurnal cycles?" Atmospheric Chemistry and Physics Discussions 9, no. 5 (September 29, 2009): 20371–406. http://dx.doi.org/10.5194/acpd-9-20371-2009.
Повний текст джерелаАнотація:
Abstract. NOx measurements were conducted at the Halley Research Station, Antarctica, during the austral summer period 1 January–10 February 2005. A clear NOx diurnal cycle was observed with minimum concentrations close to instrumental detection limit (5 pptv) measured between 04:00–05:00 GMT. NOx concentrations peaked (24 pptv) between 19:00–20:00 GMT, approximately 5 h after local solar noon. An optimised box model of NOx concentrations based on production from in-snow nitrate photolysis and chemical loss derives a mean noon emission rate of 3.48×108 molecules cm−2 s−1, assuming a 100 m boundary layer mixing height, and a relatively short NOx lifetime of ~6.4 h. This emission rate compares to directly measured values ranging from 1.7 to 3.4×108 molecules cm−2 s−1 made on 3 days at the end of the study period. Calculations of the maximum rate of NO2 loss via a variety of conventional HOx and halogen oxidation processes show that the lifetime of NOx is predominantly controlled by halogen processing, namely BrNO3 and INO3 gas-phase formation and their subsequent heterogeneous uptake, with a potential smaller contribution from HNO4 formation and uptake. Furthermore the presence of halogen oxides is shown to significantly perturb NOx concentrations by decreasing the NO/NO2 ratio. We conclude that in coastal Antarctica, the potential ozone production efficiency of NOx emitted from the snowpack is mitigated by the more rapid NOx loss due to halogen nitrate hydrolysis. These results suggest that the role of halogen oxides need to be considered when interpreting the isotopic signature of nitrate impurities held within snow and ice.
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Yamamoto, Toshiro, and Akira Noda. "Detection of Deteriorated NOx Storage-Reduction Catalyst by Thick Film Zr02 NOx Sensor." Proceedings of the JSME annual meeting 2004.7 (2004): 415–16. http://dx.doi.org/10.1299/jsmemecjo.2004.7.0_415.
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Lin, J. T., and M. B. McElroy. "Detection from space of a reduction in anthropogenic emissions of nitrogen oxides during the Chinese economic downturn." Atmospheric Chemistry and Physics Discussions 11, no. 1 (January 6, 2011): 193–223. http://dx.doi.org/10.5194/acpd-11-193-2011.
Повний текст джерелаАнотація:
Abstract. Rapid economic and industrial development in China and relatively weak emission controls have resulted in significant increases in emissions of nitrogen oxides (NOx) in recent years, with the exception of late 2008 to mid 2009 when the economic downturn led to emission reductions detectable from space. Here vertical column densities (VCDs) of tropospheric NO2 retrieved from satellite observations by SCIAMACHY, GOME-2 and OMI (both by KNMI and by NASA) are used to evaluate changes in emissions of NOx from October 2004 to February 2010 identifying impacts of the economic downturn. Data over polluted regions of Northern East China suggest an increase of 27–33% in annual mean VCD of NO2 prior to the downturn, consistent with an increase of 49% in thermal power generation (TPG) reflecting the economic growth. More detailed analysis is used to quantify changes in emissions of NOx in January over the period 2005–2010 when the effect of the downturn was most evident. The GEOS-Chem model is employed to evaluate the effect of changes in chemistry and meteorology on VCD of NO2. This analysis indicates that emissions decreased by 20% from January 2008 to January 2009, close to the reduction of 18% in TPG that occurred over the same interval. A combination of three relatively independent approaches indicates that the economic downturn was responsible for a~reduction in emissions by 9–11% in January 2009 with an additional decrease of 10% attributed to the slow-down in industrial activity associated with the coincident celebration of the Chinese New Year.
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Andersen, Simone T., Lucy J. Carpenter, Beth S. Nelson, Luis Neves, Katie A. Read, Chris Reed, Martyn Ward, Matthew J. Rowlinson, and James D. Lee. "Long-term NO<sub><i>x</i></sub> measurements in the remote marine tropical troposphere." Atmospheric Measurement Techniques 14, no. 4 (April 27, 2021): 3071–85. http://dx.doi.org/10.5194/amt-14-3071-2021.
Повний текст джерелаАнотація:
Abstract. Atmospheric nitrogen oxides (NO + NO2 = NOx) have been measured at the Cape Verde Atmospheric Observatory (CVAO) in the tropical Atlantic (16∘51′ N, 24∘52′ W) since October 2006. These measurements represent a unique time series of NOx in the background remote troposphere. Nitrogen dioxide (NO2) is measured via photolytic conversion to nitric oxide (NO) by ultraviolet light-emitting diode arrays followed by chemiluminescence detection. Since the measurements began, a blue light converter (BLC) has been used for NO2 photolysis, with a maximum spectral output of 395 nm from 2006 to 2015 and of 385 nm from 2015 onwards. The original BLC used was constructed with a Teflon-like material and appeared to cause an overestimation of NO2 when illuminated. To avoid such interferences, a new additional photolytic converter (PLC) with a quartz photolysis cell (maximum spectral output also 385 nm) was implemented in March 2017. Once corrections are made for the NO2 artefact from the original BLC, the two NO2 converters are shown to give comparable NO2 mixing ratios (BLC = 0.99 × PLC + 0.7 ppt, linear least-squares regression), giving confidence in the quantitative measurement of NOx at very low levels. Data analysis methods for the NOx measurements made at CVAO have been developed and applied to the entire time series to produce an internally consistent and high-quality long-term data set. NO has a clear diurnal pattern with a maximum mixing ratio of 2–10 ppt during the day depending on the season and ∼ 0 ppt during the night. NO2 shows a fairly flat diurnal signal, although a small increase in daytime NOx is evident in some months. Monthly average mixing ratios of NO2 vary between 5 and 30 ppt depending on the season. Clear seasonal trends in NO and NO2 levels can be observed with a maximum in autumn and winter and a minimum in spring and summer.
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Berkes, Florian, Norbert Houben, Ulrich Bundke, Harald Franke, Hans-Werner Pätz, Franz Rohrer, Andreas Wahner, and Andreas Petzold. "The IAGOS NO<sub><i>x</i></sub> instrument – design, operation and first results from deployment aboard passenger aircraft." Atmospheric Measurement Techniques 11, no. 6 (June 27, 2018): 3737–57. http://dx.doi.org/10.5194/amt-11-3737-2018.
Повний текст джерелаАнотація:
Abstract. We describe the nitrogen oxide instrument designed for the autonomous operation on board passenger aircraft in the framework of the European Research Infrastructure IAGOS (In-service Aircraft for a Global Observing System). We demonstrate the performance of the instrument using data from two deployment periods aboard an A340-300 aircraft of Deutsche Lufthansa. The well-established chemiluminescence detection method is used to measure nitrogen monoxide (NO) and nitrogen oxides (NOx). NOx is measured using a photolytic converter, and nitrogen dioxide (NO2) is determined from the difference between NOx and NO. This technique allows measuring at high time resolution (4 s) and high precision in the low ppt range (NO: 2σ = 24 pptv; NOx: 2σ = 35 pptv) over different ambient temperature and ambient pressure altitude ranges (from surface pressure down to 190 hPa). The IAGOS NOx instrument is characterized for (1) calibration stability and total uncertainty, (2) humidity and chemical interferences (e.g., ozone; nitrous acid, HONO; peroxyacetyl nitrate, PAN) and (3) inter-instrumental precision. We demonstrate that the IAGOS NOx instrument is a robust, fully automated, and long-term stable instrument suitable for unattended operation on airborne platforms, which provides useful measurements for future air quality studies and emission estimates.
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Pieterse, Elmar, Nils Rother, Cansu Yanginlar, Jelle Gerretsen, Sebastian Boeltz, Luis Enrique Munoz, Martin Herrmann, Peter Pickkers, Luuk B. Hilbrands, and Johan van der Vlag. "Cleaved N-terminal histone tails distinguish between NADPH oxidase (NOX)-dependent and NOX-independent pathways of neutrophil extracellular trap formation." Annals of the Rheumatic Diseases 77, no. 12 (August 17, 2018): 1790–98. http://dx.doi.org/10.1136/annrheumdis-2018-213223.
Повний текст джерелаАнотація:
ObjectivesNeutrophil extracellular traps (NETs) act in various rheumatic diseases. Although NET formation was originally described as a nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX)-dependent pathway, it appears that there are also NOX-independent pathways of NET release. Currently, no tools are available that can discriminate between both NET-forming pathways. We aimed to develop a serological method allowing the discrimination between NETs generated through NOX-dependent or NOX-independent pathways.MethodsHistones from in vitro generated NOX-dependent and NOX-independent NETs were characterised with a panel of lupus-derived antibodies against N-terminal histone tails using immunofluorescence microscopy, western blot and ELISA. NETs in patients with NET-associated diseases, that is, rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), psoriatic arthritis (PsA) and sepsis, were characterised in sandwich ELISAs employing antibodies against myeloperoxidase (MPO) and N-terminal histone tails as detecting and capturing antibodies, respectively. Functional responses of endothelial cells to NOX-dependent and NOX-independent NETs were assessed as well.ResultsNeutrophil elastase cleaves the N-terminal tails of core histones during NOX-dependent, but not during NOX-independent NET formation. Consequently, the detection of MPO–histone complexes with antibodies against N-terminal histone tails allows discrimination between NETs formed through a NOX-dependent or NOX-independent manner. Characterisation of in vivo circulating NETs revealed the presence of NOX-independent NETs in RA, SLE and sepsis, but NOX-dependent NETs in PsA. NOX-independent NETs displayed an increased capacity to activate endothelial cells when compared with NOX-dependent NETs.ConclusionsThese results indicate heterogeneity in NET-forming pathways in vivo and highlight the need for disease-specific strategies to prevent NET-mediated pathology.
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Lin, J. T., and M. B. McElroy. "Detection from space of a reduction in anthropogenic emissions of nitrogen oxides during the Chinese economic downturn." Atmospheric Chemistry and Physics 11, no. 15 (August 10, 2011): 8171–88. http://dx.doi.org/10.5194/acp-11-8171-2011.
Повний текст джерелаАнотація:
Abstract. Rapid economic and industrial development in China and relatively weak emission controls have resulted in significant increases in emissions of nitrogen oxides (NOx) in recent years, with the exception of late 2008 to mid 2009 when the economic downturn led to emission reductions detectable from space. Here vertical column densities (VCDs) of tropospheric NO2 retrieved from satellite observations by SCIAMACHY, GOME-2 and OMI (both by KNMI and by NASA) are used to evaluate changes in emissions of NOx from October 2004 to February 2010 identifying impacts of the economic downturn. Data over polluted regions of Northern East China suggest an increase of 27–33 % in 12-month mean VCD of NO2 prior to the downturn, consistent with an increase of 49 % in thermal power generation (TPG) reflecting the economic growth. More detailed analysis is used to quantify changes in emissions of NOx in January over the period 2005–2010 when the effect of the downturn was most evident. The GEOS-Chem model is employed to evaluate the effect of changes in chemistry and meteorology on VCD of NO2. This analysis indicates that emissions decreased by 20 % from January 2008 to January 2009, close to the reduction of 18 % in TPG that occurred over the same interval. A combination of three independent approaches indicates that the economic downturn was responsible for a reduction in emissions by 9–11 % in January 2009 with an additional decrease of 10 % attributed to the slow-down in industrial activity associated with the coincident celebration of the Chinese New Year; errors in the estimate are most likely less than 3.4 %.
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Barbero, Albane, Camille Blouzon, Joël Savarino, Nicolas Caillon, Aurélien Dommergue, and Roberto Grilli. "A compact incoherent broadband cavity-enhanced absorption spectrometer for trace detection of nitrogen oxides, iodine oxide and glyoxal at levels below parts per billion for field applications." Atmospheric Measurement Techniques 13, no. 8 (August 17, 2020): 4317–31. http://dx.doi.org/10.5194/amt-13-4317-2020.
Повний текст джерелаАнотація:
Abstract. We present a compact, affordable and robust instrument based on incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) for simultaneous detection of NOx, IO, CHOCHO and O3 in the 400–475 nm wavelength region. The instrument relies on the injection of a high-power LED source in a high-finesse cavity (F∼33 100), with the transmission signal being detected by a compact spectrometer based on a high-order diffraction grating and a charge-coupled device (CCD) camera. A minimum detectable absorption of 2.0×10-10 cm−1 was achieved within ∼22 min of total acquisition, corresponding to a figure of merit of 1.8×10-10 cm−1 Hz-1/2 per spectral element. Due to the multiplexing broadband feature of the setup, multi-species detection can be performed with simultaneous detection of NO2, IO, CHOCHO and O3 achieving detection limits of 11, 0.3, 10 ppt (parts per trillion) and 47 ppb (parts per billion) (1σ) within 22 min of measurement, respectively (half of the time is spent on the acquisition of the reference spectrum in the absence of the absorber, and the other half is spent on the absorption spectrum). The implementation on the inlet gas line of a compact ozone generator based on electrolysis of water allows for the measurement of NOx (NO+NO2) and therefore an indirect detection of NO with detection limits for NOx and NO of 10 and 21 ppt (1σ), respectively. The device has been designed to fit in a 19 in., 3U (5.25 in.) rack-mount case; weighs 15 kg; and has a total electrical power consumption of <300 W. The instrument can be employed to address different scientific objectives such as better constraining the oxidative capacity of the atmosphere, studying the chemistry of highly reactive species in atmospheric chambers as well as in the field and looking at the sources of glyoxal in the marine boundary layer to study possible implications on the formation of secondary aerosol particles.
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Zhang, Wenyi, Elder Alpes de Vasconcelos, Hidekazu Uchida, Teruaki Katsube, Toshiya Nakatsubo, and Yasushiro Nishioka. "NOx Detection with Schottky Diodes and Heterojunction Structures." IEEJ Transactions on Sensors and Micromachines 118, no. 12 (1998): 614–20. http://dx.doi.org/10.1541/ieejsmas.118.614.
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Dong, Yang, Mingsi Gu, Gongdong Zhu, Tu Tan, Kun Liu, and Xiaoming Gao. "Fully Integrated Photoacoustic NO2 Sensor for Sub-ppb Level Measurement." Sensors 20, no. 5 (February 26, 2020): 1270. http://dx.doi.org/10.3390/s20051270.
Повний текст джерелаАнотація:
A fully integrated photoacoustic nitrogen dioxide (NO2) sensor is developed and demonstrated. In this sensor, an embedded photoacoustic cell was manufactured by using an up-to-date 3D printing technique. A blue laser diode was used as a light source for excitation of photoacoustic wave in the photoacoustic cell. The photoacoustic wave is detected by a sensitive microelectromechanical system (MEMS) microphone. Homemade circuits are integrated into the sensor for laser diode driving and signal processing. The sensor was calibrated by using a chemiluminescence NO–NO2–NOX gas analyzer. And the performance of this sensor was evaluated. The linear relationship between photoacoustic signals and NO2 concentrations was verified in a range of below 202 ppb. The limit of detection was determined to 0.86 ppb with an integration time of 1 s. The corresponding normalized noise equivalent absorption was 2.0 × 10−8 cm−1∙W∙Hz−1/2. The stability and the optimal integration time were evaluated with an Allan deviation analysis, from which a detection limit of 0.25 ppb at the optimal integration time of 240 s was obtained. The sensor was used to measure outdoor air and the results agree with that obtained from the NO–NO2–NOX gas analyzer. The low-cost and portable photoacoustic NO2 sensor has a potential application for atmospheric NO2 monitoring.
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Song, Hui, Kun Li, and Chang Wang. "Selective Detection of NO and NO2 with CNTs-Based Ionization Sensor Array." Micromachines 9, no. 7 (July 16, 2018): 354. http://dx.doi.org/10.3390/mi9070354.
Повний текст джерелаАнотація:
The accurate detection of NOx is an important issue, because nitrogen oxides are not only environmental pollutants, but also harm to human health. An array composed of two carbon nanotubes (CNTs)-based ionization sensors with different separations is proposed for NO and NO2 selective detection. The experimental results indicate that the CNTs-based ionization sensor has an intrinsic, monotonically decreasing response to NO or NO2. The sensor with 80 µm separations and 100 µm separations exhibited the highest sensitivity of −0.11 nA/ppm to 300 ppm NO and −0.49 nA /ppm to 70 ppm NO2, respectively. Although the effect of the NO2 concentration on the NO response is much stronger than that of NO on NO2, the array of these two sensors still exhibits the ability to simultaneously detect the concentrations of NO and NO2 in a gas mixture without component separation.
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King, S. D. "Measurement of atmospheric oxides of nitrogen and a preliminary investigation of their source." Journal of The Royal Naval Medical Service 105, no. 1 (2019): 6–11. http://dx.doi.org/10.1136/jrnms-105-6.
Повний текст джерелаАнотація:
AbstractIntroductionMaintenance of a breathable atmosphere is a core tenet of dived submarine operations, and the responsibility for this falls to the medical department. Nitrogen oxides (NOx) are atmospheric contaminants from a currently unconfirmed source. If not controlled, these contaminants can act as respiratory irritants and asphyxiants which may endanger health and threaten sustained dived operations.MethodsUsing the issued Dräger Short Term Detection Tubes (STDTs) to sample strategic locations, the relationship between atmospheric contaminants and NOx was investigated in an attempt to determine the source of NOx formation. Interventions were implemented to reduce NOx by reducing leakage of monoethanolamine (MEA) from carbon dioxide (CO2) scrubbing equipment, a known potential source of NOx if oxidised (combusted). Dräger STDTs for NH3 demonstrate cross-reactivity with MEA, these levels being referred to as NH3/MEA.ResultsA relationship was demonstrated between elevated readings for atmospheric NH3/MEA and elevated readings for NOx, with a variable lag period. Findings suggest that NOx production may be reduced by control of atmospheric NH3/MEA. Of the control measures examined, replacement of resin filter bags was noted to reduce atmospheric NH3/MEA, while replenishment of CO2 scrubber MEA was noted to increase it, with a resultant increase in NOx production.ConclusionsElevated NH3 atmospheric readings may in fact be due to MEA from CO2 scrubbers. This, when catalytically oxidised by CO/H2 burners, produces NOx. Management of MEA egress from CO2 scrubbers (carryover) represents a potential target for NOx control interventions. Specific MEA detection equipment is required to demonstrate whether MEA or NH3 is the progenitor species for NOx. Furthermore, controlled trials are required to prove a definitive relationship between MEA and NOx and to evaluate the best control measures.
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Sklaveniti, Sofia, Nadine Locoge, Philip S. Stevens, Ezra Wood, Shuvashish Kundu, and Sébastien Dusanter. "Development of an instrument for direct ozone production rate measurements: measurement reliability and current limitations." Atmospheric Measurement Techniques 11, no. 2 (February 7, 2018): 741–61. http://dx.doi.org/10.5194/amt-11-741-2018.
Повний текст джерелаАнотація:
Abstract. Ground-level ozone (O3) is an important pollutant that affects both global climate change and regional air quality, with the latter linked to detrimental effects on both human health and ecosystems. Ozone is not directly emitted in the atmosphere but is formed from chemical reactions involving volatile organic compounds (VOCs), nitrogen oxides (NOx= NO + NO2) and sunlight. The photochemical nature of ozone makes the implementation of reduction strategies challenging and a good understanding of its formation chemistry is fundamental in order to develop efficient strategies of ozone reduction from mitigation measures of primary VOCs and NOx emissions. An instrument for direct measurements of ozone production rates (OPRs) was developed and deployed in the field as part of the IRRONIC (Indiana Radical, Reactivity and Ozone Production Intercomparison) field campaign. The OPR instrument is based on the principle of the previously published MOPS instrument (Measurement of Ozone Production Sensor) but using a different sampling design made of quartz flow tubes and a different Ox (O3 and NO2) conversion–detection scheme composed of an O3-to-NO2 conversion unit and a cavity attenuated phase shift spectroscopy (CAPS) NO2 monitor. Tests performed in the laboratory and in the field, together with model simulations of the radical chemistry occurring inside the flow tubes, were used to assess (i) the reliability of the measurement principle and (ii) potential biases associated with OPR measurements. This publication reports the first field measurements made using this instrument to illustrate its performance. The results showed that a photo-enhanced loss of ozone inside the sampling flow tubes disturbs the measurements. This issue needs to be solved to be able to perform accurate ambient measurements of ozone production rates with the instrument described in this study. However, an attempt was made to investigate the OPR sensitivity to NOx by adding NO inside the instrument. This type of investigations allows checking whether our understanding of the turnover point between NOx-limited and NOx-saturated regimes of ozone production is well understood and does not require measuring ambient OPR but instead only probing the change in ozone production when NO is added. During IRRONIC, changes in ozone production rates ranging from the limit of detection (3σ) of 6.2 ppbv h−1 up to 20 ppbv h−1 were observed when 6 ppbv of NO was added into the flow tubes.
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Pal, Nabamita, Gaurab Dutta, Khawlah Kharashi, and Erica Murray. "Investigation of an Impedimetric LaSrMnO3-Au/Y2O3-ZrO2-Al2O3 Composite NOx Sensor." Materials 15, no. 3 (February 2, 2022): 1165. http://dx.doi.org/10.3390/ma15031165.
Повний текст джерелаАнотація:
Composite NOx sensors were fabricated by combining partially and fully stabilized yttria-doped zirconia with alumina forming a composite electrolyte, Y2O3-ZrO2-Al2O3, and strontium-doped lanthanum manganese oxide mixed with gold to form the composite sensing electrode, La0.8 Sr0.2MnO3-Au. A surface chemistry analysis of the composite sensor was conducted to interpret defects and the structural phases present at the Y2O3-ZrO2-Al2O3 electrolyte, as well as the charge conduction mechanism at the LaSrMnO3-Au electrode surface. Based on the surface chemistry analysis, ionic and electronic transport properties, and microstructural features of sensor components, the working principle was described for NOx sensing at the composite sensor. The role of the composite materials on the NOx sensing response, cross-sensitivity to O2, H2O, CO, CO2, and CH4, and the response/recovery rates relative to sensor accuracy were characterized by operating the composite NOx sensors via the impedimetric method. The composite sensors were operated at temperatures ranging from 575 to 675 °C in dry and humidified gas environments with NO and NO2 concentrations varying from 0 to 100 ppm, where the balance gas was N2. It was found that the microstructure of the composite NOx sensor electrolyte and sensing electrode had a significant effect on interfacial reactions at the triple phase boundary, as well as the density of active sites for oxygen reactions. Overall, the composite NOx sensor microstructure enabled a high NOx sensing response, along with low cross-sensitivity to O2, CO, CO2, and CH4, and promoted NO detection down to 2 ppm.
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Huang, Yeyuan, Ang Li, Thomas Wagner, Yang Wang, Zhaokun Hu, Pinhua Xie, Jin Xu, et al. "The quantification of NO<sub><i>x</i></sub> and SO<sub>2</sub> point source emission flux errors of mobile differential optical absorption spectroscopy on the basis of the Gaussian dispersion model: a simulation study." Atmospheric Measurement Techniques 13, no. 11 (November 11, 2020): 6025–51. http://dx.doi.org/10.5194/amt-13-6025-2020.
Повний текст джерелаАнотація:
Abstract. Mobile differential optical absorption spectroscopy (mobile DOAS) has become an important tool for the quantification of emission sources, including point sources (e.g., individual power plants) and area emitters (e.g., entire cities). In this study, we focused on the error budget of mobile DOAS measurements from point sources, and we also offered recommendations for the optimum settings of such measurements via a simulation with a modified Gaussian plume model. Following the analysis, we conclude that (1) the proper sampling resolution should be between 5 and 50 m. (2) When measuring far from the source, undetectable flux (measured slant column densities (SCDs) are under the detection limit) resulting from wind dispersion is the main error source. The threshold for the undetectable flux can be lowered by larger integration time. When measuring close to the source, low sampling frequency results in large errors, and wind field uncertainty becomes the main error source of SO2 flux (for NOx this error also increases, but other error sources dominate). More measurement times can lower the flux error that results from wind field uncertainty. The proper wind speed for mobile DOAS measurements is between 1 and 4 m s−1. (3) The remaining errors by [NOx] ∕ [NO2] ratio correction can be significant when measuring very close. To minimize the [NOx] ∕ [NO2] ratio correction error, we recommend minimum distances from the source, at which 5 % of the NO2 maximum reaction rate is reached and thus NOx steady state can be assumed. (4) Our study suggests that emission rates < 30 g s−1 for NOx and < 50 g s−1 for SO2 are not recommended for mobile DOAS measurements. Based on the model simulations, our study indicates that mobile DOAS measurements are a very well-suited tool to quantify point source emissions. The results of our sensitivity studies are important to make optimum use of such measurements.
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Beirle, S., N. Spichtinger, A. Stohl, K. L. Cummins, T. Turner, D. Boccippio, O. R. Cooper, et al. "Estimating the NO<sub>x</sub> produced by lightning from GOME and NLDN data: a case study in the Gulf of Mexico." Atmospheric Chemistry and Physics Discussions 5, no. 6 (November 9, 2005): 11295–329. http://dx.doi.org/10.5194/acpd-5-11295-2005.
Повний текст джерелаАнотація:
Abstract. Nitrogen oxides (NOx=NO+NO2) play an important role in tropospheric chemistry, in particular in catalytic ozone production. Lightning provides a natural source of nitrogen oxides, dominating the production in the tropical upper troposphere, with strong impact on tropospheric ozone and the atmosphere's oxidizing capacity. Recent estimates of lightning produced NOx (LNOx) are of the order of 5 Tg [N] per year with still high uncertainties in the range of one order of magnitude. The Global Ozone Monitoring Experiment (GOME) on board the ESA-satellite ERS-2 allows the retrieval of tropospheric vertical column densities (TVCDs) of NO2 on a global scale. Here we present the GOME NO2 measurement directly over a large convective system over the Gulf of Mexico. Simultaneously, cloud-to-ground (CG) flashes are counted by the U.S. National Lightning Detection Network (NLDNTM), and extrapolated to include intra-cloud (IC)+CG flashes based on a climatological IC:CG ratio derived from NASA's space-based lightning sensors. A series of 14 GOME pixels shows largely enhanced TVCDs over thick and high clouds, coinciding with strong lightning activity. The enhancements can not be explained by transport of anthropogenic NOx and must be due to fresh production of LNOx. A quantitative analysis, accounting in particular for the visibility of LNOx from satellite, yields a LNOx production of 77 (27–230) moles of NOx, or 1.1 (0.4–3.2) kg [N], per flash. If simply extrapolated, this corresponds to a global LNOx production of 1.5 (0.5–4.5) Tg [N]/yr.
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Beirle, S., H. Huntrieser, and T. Wagner. "Direct satellite observation of lightning-produced NO<sub>x</sub>." Atmospheric Chemistry and Physics Discussions 10, no. 8 (August 2, 2010): 18255–313. http://dx.doi.org/10.5194/acpd-10-18255-2010.
Повний текст джерелаАнотація:
Abstract. Lightning is an important source of NOx in the free troposphere, especially in the tropics, with high impact on ozone production. However, estimates of lightning NOx (LNOx) production efficiency (LNOx per flash) are still quite uncertain. In this study we present a systematic analysis of NO2 column densities from SCIAMACHY measurements over active thunderstorms, as detected by the World-Wide Lightning Location Network (WWLLN), where the WWLLN detection efficiency was estimated using the flash climatology of the satellite lightning sensors LIS/OTD. Only events with high lightning activity are considered, where corrected WWLLN flash rate densities inside the satellite pixel within the last hour are above 1 /km2/h. For typical SCIAMACHY ground pixels of 30×60 km2, this threshold corresponds to 1800 flashes over the last hour, which, for literature estimates of lightning NOx production, should result in clearly enhanced NO2 column densities. From 2004–2008, we find 287 coincidences of SCIAMACHY measurements and high WWLLN flash rate densities. For some of these events, a clear enhancement of column densities of NO2 could be observed, indeed. But overall, the measured column densities are below the expected values by more than one order of magnitude, and in most of the cases, no enhanced NO2 could be found at all. Our results are in contradiction to the currently accepted range of LNOx production per flash of 15 (2–40)×1025 molec/flash. This probably partly results from the specific conditions for the events under investigation, i.e. events of high lightning activity in the morning (local time) and mostly (for 162 out of 287 events) over ocean. Within the detected coincidences, the highest NO2 column densities were observed around the US Eastcoast. This might be partly due to interference with ground sources of NOx being uplifted by the convective systems. However, it could also indicate that flashes in this region are particularly productive. We conclude that current estimates of LNOx production might be biased high for two reasons. First, we observe a high variability of NO2 for coincident lightning events. This high variability can easily cause a publication bias, since studies reporting on high NOx production have likely been published, while studies finding no or low amounts of NOx might have been rejected as errorneous or not significant. Second, many estimates of LNOx production in literature have been performed over the US, which is probably not representative for global lightning.
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Beirle, S., H. Huntrieser, and T. Wagner. "Direct satellite observation of lightning-produced NO<sub>x</sub>." Atmospheric Chemistry and Physics 10, no. 22 (November 24, 2010): 10965–86. http://dx.doi.org/10.5194/acp-10-10965-2010.
Повний текст джерелаАнотація:
Abstract. Lightning is an important source of NOx in the free troposphere, especially in the tropics, with strong impact on ozone production. However, estimates of lightning NOx (LNOx) production efficiency (LNOx per flash) are still quite uncertain. In this study we present a systematic analysis of NO2 column densities from SCIAMACHY measurements over active thunderstorms, as detected by the World-Wide Lightning Location Network (WWLLN), where the WWLLN detection efficiency was estimated using the flash climatology of the satellite lightning sensors LIS/OTD. Only events with high lightning activity are considered, where corrected WWLLN flash rate densities inside the satellite pixel within the last hour are above 1 /km2/h. For typical SCIAMACHY ground pixels of 30 × 60 km2, this threshold corresponds to 1800 flashes over the last hour, which, for literature estimates of lightning NOx production, should result in clearly enhanced NO2 column densities. From 2004–2008, we find 287 coincidences of SCIAMACHY measurements and high WWLLN flash rate densities. For some of these events, a clear enhancement of column densities of NO2 could be observed, indeed. But overall, the measured column densities are below the expected values by more than one order of magnitude, and in most of the cases, no enhanced NO2 could be found at all. Our results are in contradiction to the currently accepted range of LNOx production per flash of 15 (2–40)×1025 molec/flash. This probably partly results from the specific conditions for the events under investigation, i.e. events of high lightning activity in the morning (local time) and mostly (for 162 out of 287 events) over ocean. Within the detected coincidences, the highest NO2 column densities were observed around the US Eastcoast. This might be partly due to interference with ground sources of NOx being uplifted by the convective systems. However, it could also indicate that flashes in this region are particularly productive. We conclude that current estimates of LNOx production might be biased high for two reasons. First, we observe a high variability of NO2 for coincident lightning events. This high variability can easily cause a publication bias, since studies reporting on high NOx production have likely been published, while studies finding no or low amounts of NOx might have been rejected as errorneous or not significant. Second, many estimates of LNOx production in literature have been performed over the US, which is probably not representative for global lightning.
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Donker, Nils, Anastasiya Ruchets, Daniela Schoenauer-Kamin, Jens Zosel, Ulrich Guth, and Ralf Moos. "NOx Detection By Pulse Polarization: Influence of Gold Electrodes." ECS Meeting Abstracts MA2021-01, no. 56 (May 30, 2021): 1501. http://dx.doi.org/10.1149/ma2021-01561501mtgabs.
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Donker, Nils, Anastasiya Ruchets, Daniela Schönauer-Kamin, Jens Zosel, Ulrich Guth, and Ralf Moos. "NOx Detection By Pulse Polarization: Influence of Gold Electrodes." ECS Meeting Abstracts MA2020-01, no. 28 (May 1, 2020): 2062. http://dx.doi.org/10.1149/ma2020-01282062mtgabs.
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Chang, Fei, Zhuoli Shi, Yibo Lei, Zhongyuan Zhao, Yingfei Qi, Penghong Yin, and Shengwen Chen. "The Strengthened Photocatalytic NOx Removal of Composites Bi4O5Br2/BiPO4: The Efficient Regulation of Interface Carriers by Integrating a Wide-Bandgap Ornament." Molecules 27, no. 23 (December 2, 2022): 8474. http://dx.doi.org/10.3390/molecules27238474.
Повний текст джерелаАнотація:
A series of binary composites Bi4O5Br2/BiPO4 (PBX) was fabricated through a simple mechanical ball milling protocol. Relevant microstructural, morphological, and optical properties were thoroughly analyzed via various techniques. The integration of both components was confirmed to produce heterojunction domains at the phase boundaries. Upon exposure to visible light irradiation, the as-achieved PBX series possessed the reinforced photocatalytic NOx removal efficiencies and the weakened generation of toxic intermediate NO2 in comparison to both bare components, chiefly attributed to the efficient transport and separation of carriers and boosted production of superoxide radicals (·O2−) through the combination of a wide-bandgap ornament BiPO4 as an electron acceptor. In particular, the composite PB5 with the optimal phase composition exhibited the highest NOx removal of 40% with the lowest NO2 formation of 40 ppb among all tested candidates. According to the band structures’ estimation and reactive species’ detection, a reasonable mechanism was ultimately proposed to describe the migration of charge carriers and the enhancement of photocatalytic performance.
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Wagner, N. L., W. P. Dubé, R. A. Washenfelder, C. J. Young, I. B. Pollack, T. B. Ryerson, and S. S. Brown. "Diode laser-based cavity ring-down instrument for NO<sub>3</sub>, N<sub>2</sub>O<sub>5</sub>, NO, NO<sub>2</sub> and O<sub>3</sub> from aircraft." Atmospheric Measurement Techniques 4, no. 6 (June 28, 2011): 1227–40. http://dx.doi.org/10.5194/amt-4-1227-2011.
Повний текст джерелаАнотація:
Abstract. This article presents a diode laser-based, cavity ring-down spectrometer for simultaneous in situ measurements of four nitrogen oxide species, NO3, N2O5, NO, NO2, as well as O3, designed for deployment on aircraft. The instrument measures NO3 and NO2 by optical extinction at 662 nm and 405 nm, respectively; N2O5 is measured by thermal conversion to NO3, while NO and O3 are measured by chemical conversion to NO2. The instrument has several advantages over previous instruments developed by our group for measurement of NO2, NO3 and N2O5 alone, based on a pulsed Nd:YAG and dye laser. First, the use of continuous wave diode lasers reduces the requirements for power and weight and eliminates hazardous materials. Second, detection of NO2 at 405 nm is more sensitive than our previously reported 532 nm instrument, and does not have a measurable interference from O3. Third, the instrument includes chemical conversion of NO and O3 to NO2 to provide measurements of total NOx (= NO + NO2) and Ox (= NO2 + O3) on two separate channels; mixing ratios of NO and O3 are determined by subtraction of NO2. Finally, all five species are calibrated against a single standard based on 254 nm O3 absorption to provide high accuracy. Disadvantages include an increased sensitivity to water vapor on the 662 nm NO3 and N2O5 channels and a modest reduction in sensitivity for these species compared to the pulsed laser instrument. The in-flight detection limit for both NO3 and N2O5 is 3 pptv (2 σ, 1 s) and for NO, NO2 and O3 is 140, 90, and 120 pptv (2 σ, 1 s) respectively. Demonstrated performance of the instrument in a laboratory/ground based environment is better by approximately a factor of 2–3. The NO and NO2 measurements are less precise than research-grade chemiluminescence instruments. However, the combination of these five species in a single instrument, calibrated to a single analytical standard, provides a complete and accurate picture of nighttime nitrogen oxide chemistry. The instrument performance is demonstrated using data acquired during a recent field campaign in California.
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Casanova, John A., Lois K. Gross, Sarah E. McMullen, and Frank J. Schenck. "Use of Griess Reagent Containing Vanadium(III) for Post-Column Derivatization and Simultaneous Determination of Nitrite and Nitrate in Baby Food." Journal of AOAC INTERNATIONAL 89, no. 2 (March 1, 2006): 447–51. http://dx.doi.org/10.1093/jaoac/89.2.447.
Повний текст джерелаАнотація:
Abstract An ion chromatographic method with post-column derivatization and spectrophotometric detection is presented for the determination of nitrate and nitrite (NOx) in baby food. NOx residues found naturally or added as preservatives were extracted from baby foods and determined by using ion chromatography with post-column derivatization and spectrophotometric detection. Nitrate was reduced to nitrite online by post-column reduction using vanadium(III) chloride and heat. Nitrite reacted with Griess reagent to produce a dye that was detected at 525 nm. The use of V(III) and heat to promote the reduction of nitrate to nitrite online is a novel feature of this detection system. The determination of incurred NOx residues in samples by using AOAC Method 993.03 yielded results comparable to those obtained by ion chromatography with spectrophotometric detection. The toxic and carcinogenic metal cadmium used in the AOAC Method to reduce the nitrate to nitrite was avoided. The proposed method provides simultaneous determination of nitrate and nitrite. Average recoveries of nitrate and nitrite residues ranged from 82 to 107 for fortification levels of 25400 ppm.
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Beirle, S., N. Spichtinger, A. Stohl, K. L. Cummins, T. Turner, D. Boccippio, O. R. Cooper, et al. "Estimating the NO<sub>x</sub> produced by lightning from GOME and NLDN data: a case study in the Gulf of Mexico." Atmospheric Chemistry and Physics 6, no. 4 (April 3, 2006): 1075–89. http://dx.doi.org/10.5194/acp-6-1075-2006.
Повний текст джерелаАнотація:
Abstract. Nitrogen oxides (NOxNO+NO2) play an important role in tropospheric chemistry, in particular in catalytic ozone production. Lightning provides a natural source of nitrogen oxides, dominating the production in the tropical upper troposphere, with strong impact on tropospheric ozone and the atmosphere's oxidizing capacity. Recent estimates of lightning produced NOx (LNOx) are of the order of 5 Tg [N] per year with still high uncertainties in the range of one order of magnitude. The Global Ozone Monitoring Experiment (GOME) on board the ESA-satellite ERS-2 allows the retrieval of tropospheric column densities of NO2 on a global scale. Here we present the GOME NO2 measurement directly over a large convective system over the Gulf of Mexico. Simultaneously, cloud-to-ground (CG) flashes are counted by the U.S. National Lightning Detection Network (NLDNTM), and extrapolated to include intra-cloud (IC)+CG flashes based on a climatological IC:CG ratio derived from NASA's space-based lightning sensors. A series of 14 GOME pixels shows largely enhanced column densities over thick and high clouds, coinciding with strong lightning activity. The enhancements can not be explained by transport of anthropogenic NOx and must be due to fresh production of LNOx. A quantitative analysis, accounting in particular for the visibility of LNOx from satellite, yields a LNOx production of 90 (32-240) moles of NOx, or 1.3 (0.4-3.4) kg [N], per flash. If simply extrapolated, this corresponds to a global LNOx production of 1.7 (0.6-4.7)Tg [N]/yr.
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Valdés-Madrigal, Manuel A., Fernando Montejo-Alvaro, Amelia S. Cernas-Ruiz, Hugo Rojas-Chávez, Ramon Román-Doval, Heriberto Cruz-Martinez, and Dora I. Medina. "Role of Defect Engineering and Surface Functionalization in the Design of Carbon Nanotube-Based Nitrogen Oxide Sensors." International Journal of Molecular Sciences 22, no. 23 (November 30, 2021): 12968. http://dx.doi.org/10.3390/ijms222312968.
Повний текст джерелаАнотація:
Nitrogen oxides (NOx) are among the main atmospheric pollutants; therefore, it is important to monitor and detect their presence in the atmosphere. To this end, low-dimensional carbon structures have been widely used as NOx sensors for their outstanding properties. In particular, carbon nanotubes (CNTs) have been widely used as toxic-gas sensors owing to their high specific surface area and excellent mechanical properties. Although pristine CNTs have shown promising performance for NOx detection, several strategies have been developed such as surface functionalization and defect engineering to improve the NOx sensing of pristine CNT-based sensors. Through these strategies, the sensing properties of modified CNTs toward NOx gases have been substantially improved. Therefore, in this review, we have analyzed the defect engineering and surface functionalization strategies used in the last decade to modify the sensitivity and the selectivity of CNTs to NOx. First, the different types of surface functionalization and defect engineering were reviewed. Thereafter, we analyzed experimental, theoretical, and coupled experimental–theoretical studies on CNTs modified through surface functionalization and defect engineering to improve the sensitivity and selectivity to NOx. Finally, we presented the conclusions and the future directions of modified CNTs as NOx sensors.
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Möller, Peter, Mike Andersson, Anita Lloyd Spetz, Jarkko Puustinen, Jyrki Lappalainen, and Jens Eriksson. "NOx Sensing with SiC Field Effect Transistors." Materials Science Forum 858 (May 2016): 993–96. http://dx.doi.org/10.4028/www.scientific.net/msf.858.993.
Повний текст джерелаАнотація:
In this paper, we investigated the nitrogen oxides (NO, NO2) detection capability of strontium titanate (SrTiO3) when used as sensing layer on gas sensitive silicon carbide field effect transistors (SiC-FETs). Sensitivity, selectivity and response times for NO, NO2, and NH3 were characterized, to determine the possibility for diesel exhaust after treatment control applications. It was found that NOx can be detected down to single digit ppm levels at sensor temperatures in the 550°C - 600°C range. In addition, the results indicate that it is possible to suppress sensitivity to ammonia by selecting an operating temperature around 530°C.
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Dixneuf, Sophie, Albert A. Ruth, Rolf Häseler, Theo Brauers, Franz Rohrer, and Hans-Peter Dorn. "Detection of nitrous acid in the atmospheric simulation chamber SAPHIR using open-path incoherent broadband cavity-enhanced absorption spectroscopy and extractive long-path absorption photometry." Atmospheric Measurement Techniques 15, no. 4 (February 23, 2022): 945–64. http://dx.doi.org/10.5194/amt-15-945-2022.
Повний текст джерелаАнотація:
Abstract. An instrument based on 20 m open-path incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) was established at the Jülich SAPHIR chamber in spring 2011. The setup was optimized for the detection of HONO and NO2 in the near-UV region 352–386 nm, utilizing a bright hot-spot Xe-arc lamp and a UV-enhanced charge-coupled device (CCD) detector. A 2σ detection limit of 26 pptv for HONO and 76 pptv for NO2 was achieved for an integration time of 1 min. Methacrolein (MACR) was also detected at mixing ratios below 5 ppbv with an estimated 2σ detection limit of 340 pptv for the same integration time. The IBBCEAS instrument's performance for HONO and NO2 detection was compared to that of extractive wet techniques, long-path absorption photometry (LOPAP), and chemiluminescence spectrometry (CLS) NOx detection, respectively. For the combined data sets an overall good agreement for both trend and absolute mixing ratios was observed between IBBCEAS and these established instruments at SAPHIR. Correlation coefficients r for HONO range from 0.930 to 0.994 and for NO2 from 0.937 to 0.992. For the single measurement of MACR r=0.981 is found in comparison to proton-transfer-reaction mass spectrometry (PTRMS).
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Do, Jing-Shan, and Po-Jen Chen. "Amperometric sensor array for NOx, CO, O2 and SO2 detection." Sensors and Actuators B: Chemical 122, no. 1 (March 2007): 165–73. http://dx.doi.org/10.1016/j.snb.2006.05.030.
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Melamed, M. L., R. Basaldud, R. Steinbrecher, S. Emeis, L. G. Ruíz-Suárez, and M. Grutter. "Detection of pollution transport events southeast of Mexico City using ground-based visible spectroscopy measurements of nitrogen dioxide." Atmospheric Chemistry and Physics Discussions 9, no. 1 (February 24, 2009): 4769–804. http://dx.doi.org/10.5194/acpd-9-4769-2009.
Повний текст джерелаАнотація:
Abstract. This work presents ground based differential optical absorption spectroscopy (DOAS) measurements of nitrogen dioxide (NO2) during the MILAGRO field campaign in March 2006 at the Tenango del Aire research site located to the southeast of Mexico City. The DOAS NO2 column density measurements are used in conjunction with ceilometer, meteorological and surface nitrogen oxides (NOx) and total reactive nitrogen (NOy) measurements to show a more comprehensive view of air pollution results when a research site has both surface and remote sensing instruments. An in depth analysis of 13 March 2006 demonstrates how DOAS NO2, surface NO2 and ceilometer data can be used to determine the extent of mixing of the pollution layer. In addition, we show the effectiveness of how DOAS measurements can be used to observe pollution sources that may reside above the mixing layer, such as the presence of lightning produced NO2 as seen on 28 March 2006.
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Wagner, N. L., W. P. Dubé, R. A. Washenfelder, C. J. Young, I. B. Pollack, T. B. Ryerson, and S. S. Brown. "Diode laser-based cavity ring-down instrument for NO<sub>3</sub>, N<sub>2</sub>O<sub>5</sub>, NO, NO<sub>2</sub> and O<sub>3</sub> from aircraft." Atmospheric Measurement Techniques Discussions 4, no. 2 (March 3, 2011): 1555–91. http://dx.doi.org/10.5194/amtd-4-1555-2011.
Повний текст джерелаАнотація:
Abstract. This article presents a diode laser based, cavity ring-down spectrometer for simultaneous in situ measurements of four nitrogen oxide species, NO3, N2O5, NO, NO2, as well as O3, designed for deployment on aircraft. The instrument measures NO3 and NO2 by optical extinction at 662 nm and 405 nm, respectively; N2O5 is measured by thermal conversion to NO3, while NO and O3 are measured by chemical conversion to NO2. The instrument has several advantages over previous instruments developed by our group for measurement of NO2, NO3 and N2O5 alone, based on a pulsed Nd:YAG and dye laser. First, the use of continuous wave diode lasers reduces the requirements for power and weight and eliminates hazardous materials. Second, detection of NO2 at 405 nm is more sensitive than our previously reported 532 nm instrument, and does not have a measurable interference from O3. Third, the instrument includes chemical conversion of NO and O3 to NO2 to provide measurements of total NOx (= NO + NO2) and Ox (= NO2 + O3) on two separate channels; mixing ratios of NO and O3 are determined by subtraction of NO2. Finally, all five species are calibrated against a single standard based on 254 nm O3 absorption to provide high accuracy. Disadvantages include an increased sensitivity to water vapor on the 662 nm NO3 and N2O5 channels and a modest reduction in sensitivity for these species compared to the pulsed laser instrument. The measurement precision for both NO3 and N2O5 is below 1 pptv (2σ, 1 s) and for NO, NO2 and O3 is 170, 46, and 56 pptv (2σ, 1 s) respectively. The NO and NO2 measurements are less precise than research-grade chemiluminescence instruments. However, the combination of these five species in a single instrument, calibrated to a single analytical standard, provides a complete and accurate picture of nighttime nitrogen oxide chemistry. The instrument performance is demonstrated using data acquired during a recent field campaign in California.
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Bleicher, S., J. C. Buxmann, R. Sander, T. P. Riedel, J. A. Thornton, U. Platt, and C. Zetzsch. "The influence of nitrogen oxides on the activation of bromide and chloride in salt aerosol." Atmospheric Chemistry and Physics Discussions 14, no. 7 (April 22, 2014): 10135–66. http://dx.doi.org/10.5194/acpd-14-10135-2014.
Повний текст джерелаАнотація:
Abstract. Experiments on salt aerosol with different salt contents were performed in a Teflon chamber under tropospheric light conditions with various initial contents of nitrogen oxides (NOx = NO + NO2). A strong activation of halogens was found at high NOx mixing ratios, even in samples with lower bromide contents such as road salts. The ozone depletion by reactive halogen species released from the aerosol, was found to be a function of the initial NOx mixing ratio. Besides bromine, large amounts of chlorine have been released in our smog chamber. Time profiles of the halogen species Cl2, Br2, ClNO2, BrNO2 and BrO, ClO, OClO and Cl atoms were simultaneously measured by various techniques (chemical ionization mass spectrometry, differential optical absorption spectrometry coupled with a multi-reflection cell and gas chromatography of hydrocarbon tracers for Cl and OH, employing cryogenic preconcentration and flame ionization detection). Measurements are compared to calculations by the CAABA/MECCA 0-D box model, which was adapted to the chamber conditions and took the aerosol liquid water content and composition into account. The model results agree reasonably with the observations and provide important information about the prerequisites for halogen release, such as the time profiles of the aerosol bromide and chloride contents as well as the aerosol pH.
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Saoutieff, Elise, Tiziana Polichetti, Laurent Jouanet, Adrien Faucon, Audrey Vidal, Alexandre Pereira, Sébastien Boisseau, et al. "A Wearable Low-Power Sensing Platform for Environmental and Health Monitoring: The Convergence Project." Sensors 21, no. 5 (March 5, 2021): 1802. http://dx.doi.org/10.3390/s21051802.
Повний текст джерелаАнотація:
The low-power sensing platform proposed by the Convergence project is foreseen as a wireless, low-power and multifunctional wearable system empowered by energy-efficient technologies. This will allow meeting the strict demands of life-style and healthcare applications in terms of autonomy for quasi-continuous collection of data for early-detection strategies. The system is compatible with different kinds of sensors, able to monitor not only health indicators of individual person (physical activity, core body temperature and biomarkers) but also the environment with chemical composition of the ambient air (NOx, COx, NHx particles) returning meaningful information on his/her exposure to dangerous (safety) or pollutant agents. In this article, we introduce the specifications and the design of the low-power sensing platform and the different sensors developed in the project, with a particular focus on pollutant sensing capabilities and specifically on NO2 sensor based on graphene and CO sensor based on polyaniline ink.
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Kuhlmann, Gerrit, Grégoire Broquet, Julia Marshall, Valentin Clément, Armin Löscher, Yasjka Meijer, and Dominik Brunner. "Detectability of CO<sub>2</sub> emission plumes of cities and power plants with the Copernicus Anthropogenic CO<sub>2</sub> Monitoring (CO2M) mission." Atmospheric Measurement Techniques 12, no. 12 (December 19, 2019): 6695–719. http://dx.doi.org/10.5194/amt-12-6695-2019.
Повний текст джерелаАнотація:
Abstract. High-resolution atmospheric transport simulations were used to investigate the potential for detecting carbon dioxide (CO2) plumes of the city of Berlin and neighboring power stations with the Copernicus Anthropogenic Carbon Dioxide Monitoring (CO2M) mission, which is a proposed constellation of CO2 satellites with imaging capabilities. The potential for detecting plumes was studied for satellite images of CO2 alone or in combination with images of nitrogen dioxide (NO2) and carbon monoxide (CO) to investigate the added value of measurements of other gases coemitted with CO2 that have better signal-to-noise ratios. The additional NO2 and CO images were either generated for instruments on the same CO2M satellites (2 km× 2 km resolution) or for the Sentinel-5 instrument (7.5 km× 7.5 km) assumed to fly 2 h earlier than CO2M. Realistic CO2, CO and NOX(=NO+NO2) fields were simulated at 1 km× 1 km horizontal resolution with the Consortium for Small-scale Modeling model extended with a module for the simulation of greenhouse gases (COSMO-GHG) for the year 2015, and they were used as input for an orbit simulator to generate synthetic observations of columns of CO2, CO and NO2 for constellations of up to six satellites. A simple plume detection algorithm was applied to detect coherent structures in the images of CO2, NO2 or CO against instrument noise and variability in background levels. Although six satellites with an assumed swath of 250 km were sufficient to overpass Berlin on a daily basis, only about 50 out of 365 plumes per year could be observed in conditions suitable for emission estimation due to frequent cloud cover. With the CO2 instrument only 6 and 16 of these 50 plumes could be detected assuming a high-noise (σVEG50=1.0 ppm) and low-noise (σVEG50=0.5 ppm) scenario, respectively, because the CO2 signals were often too weak. A CO instrument with specifications similar to the Sentinel-5 mission performed worse than the CO2 instrument, while the number of detectable plumes could be significantly increased to about 35 plumes with an NO2 instrument. CO2 and NO2 plumes were found to overlap to a large extent, although NOX had a limited lifetime (assumed to be 4 h) and although CO2 and NOX were emitted with different NOX:CO2 emission ratios by different source types with different temporal and vertical emission profiles. Using NO2 observations from the Sentinel-5 platform instead resulted in a significant spatial mismatch between NO2 and CO2 plumes due to the 2 h time difference between Sentinel-5 and CO2M. The plumes of the coal-fired power plant Jänschwalde were easier to detect with the CO2 instrument (about 40–45 plumes per year), but, again, an NO2 instrument could detect significantly more plumes (about 70). Auxiliary measurements of NO2 were thus found to greatly enhance the capability of detecting the location of CO2 plumes, which will be invaluable for the quantification of CO2 emissions from large point sources.
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Womack, Caroline C., J. Andrew Neuman, Patrick R. Veres, Scott J. Eilerman, Charles A. Brock, Zachary C. J. Decker, Kyle J. Zarzana, et al. "Evaluation of the accuracy of thermal dissociation CRDS and LIF techniques for atmospheric measurement of reactive nitrogen species." Atmospheric Measurement Techniques 10, no. 5 (May 31, 2017): 1911–26. http://dx.doi.org/10.5194/amt-10-1911-2017.
Повний текст джерелаАнотація:
Abstract. The sum of all reactive nitrogen species (NOy) includes NOx (NO2 + NO) and all of its oxidized forms, and the accurate detection of NOy is critical to understanding atmospheric nitrogen chemistry. Thermal dissociation (TD) inlets, which convert NOy to NO2 followed by NO2 detection, are frequently used in conjunction with techniques such as laser-induced fluorescence (LIF) and cavity ring-down spectroscopy (CRDS) to measure total NOy when set at > 600 °C or speciated NOy when set at intermediate temperatures. We report the conversion efficiency of known amounts of several representative NOy species to NO2 in our TD-CRDS instrument, under a variety of experimental conditions. We find that the conversion efficiency of HNO3 is highly sensitive to the flow rate and the residence time through the TD inlet as well as the presence of other species that may be present during ambient sampling, such as ozone (O3). Conversion of HNO3 at 400 °C, nominally the set point used to selectively convert organic nitrates, can range from 2 to 6 % and may represent an interference in measurement of organic nitrates under some conditions. The conversion efficiency is strongly dependent on the operating characteristics of individual quartz ovens and should be well calibrated prior to use in field sampling. We demonstrate quantitative conversion of both gas-phase N2O5 and particulate ammonium nitrate in the TD inlet at 650 °C, which is the temperature normally used for conversion of HNO3. N2O5 has two thermal dissociation steps, one at low temperature representing dissociation to NO2 and NO3 and one at high temperature representing dissociation of NO3, which produces exclusively NO2 and not NO. We also find a significant interference from partial conversion (5–10 %) of NH3 to NO at 650 °C in the presence of representative (50 ppbv) levels of O3 in dry zero air. Although this interference appears to be suppressed when sampling ambient air, we nevertheless recommend regular characterization of this interference using standard additions of NH3 to TD instruments that convert reactive nitrogen to NO or NO2.
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Crowley, J. N., J. Thieser, M. Tang, G. Schuster, H. Bozem, Z. Hosaynali Beygi, H. Fischer, et al. "Variable lifetimes and loss mechanisms for NO<sub>3</sub> and N<sub>2</sub>O<sub>5</sub> during the DOMINO campaign: contrasts between marine, urban and continental air." Atmospheric Chemistry and Physics Discussions 11, no. 6 (June 23, 2011): 17825–77. http://dx.doi.org/10.5194/acpd-11-17825-2011.
Повний текст джерелаАнотація:
Abstract. Nighttime mixing ratios of boundary layer N2O5 were determined using cavity-ring-down spectroscopy during the DOMINO campaign. Observation of N2O5 was intermittent, with mixing ratios ranging from below the detection limit (~5 ppt) to ~500 ppt. A steady-state analysis constrained by measured mixing ratios of NO2 and O3 was used to derive NO3 lifetimes and compare them to calculated rates of loss via gas-phase and heterogeneous reactions of both NO3 and N2O5. Three distinct types of air masses were encountered, which were largely marine (Atlantic), continental or urban-industrial in origin. NO3 lifetimes were longest in the Atlantic sector (up to ~30 min) but were very short (a few seconds) in polluted, air masses from the local city and petroleum-related industrial complex of Huelva. Air from the continental sector was an intermediate case. The high reactivity to NO3 of the urban air mass was not accounted for by gas-phase and heterogeneous reactions, rates of which were constrained by measurements of NO, volatile organic species and aerosol surface area. In general, high NO2 mixing ratios resulted in low NO3 lifetimes, though heterogeneous processes (e.g. reaction of N2O5 on aerosol) were generally less important than direct gas-phase losses of NO3. The presence of SO2 at levels above ~2 ppb in the urban air sector was always associated with very low N2O5 mixing ratios indicating either very short NO3 lifetimes in the presence of combustion-related emissions or an important role for reduced sulphur species in urban, nighttime chemistry. High production rates coupled with low lifetimes of NO3 imply an important contribution of nighttime chemistry to removal of both NOx and VOC.
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Sava Gallis, Dorina F., Dayton J. Vogel, Grace A. Vincent, Jessica M. Rimsza, and Tina M. Nenoff. "NOx Adsorption and Optical Detection in Rare Earth Metal–Organic Frameworks." ACS Applied Materials & Interfaces 11, no. 46 (October 28, 2019): 43270–77. http://dx.doi.org/10.1021/acsami.9b16470.
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