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Artykuły w czasopismach na temat "Aerosols - Production Mechanisms"
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Lin, G., J. E. Penner, S. Sillman, D. Taraborrelli i J. Lelieveld. "Global mechanistic model of SOA formation: effects of different chemical mechanisms". Atmospheric Chemistry and Physics Discussions 11, nr 9 (22.09.2011): 26347–413. http://dx.doi.org/10.5194/acpd-11-26347-2011.
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Abstract. Recent experimental findings indicate that Secondary Organic Aerosol (SOA) represents an important and, under many circumstances, the major fraction of the organic aerosol burden. Here, we use a global 3-d model (IMPACT) to test the results of different mechanisms for the production of SOA. The basic mechanism includes SOA formation from organic nitrates and peroxides produced from an explicit chemical formulation, using partition coefficients based on thermodynamic principles. We also include the formation of non-evaporative SOA from the reaction of glyoxal and methylglyoxal on aqueous aerosols and cloud droplets as well as from the reaction of epoxides on aqueous aerosols. A model simulation including these SOA formation mechanisms gives an annual global SOA production of 113.5 Tg. The global production of SOA is substantially decreased to 85.0 Tg yr−1 if the HOx regeneration mechanism proposed by Peeters et al. (2009) is used. Model predictions with and without this HOx regeneration scheme are compared with multiple surface observation datasets, namely: the Interagency Monitoring of Protected Visual Environments (IMPROVE) for the United States, the European Monitoring and Evaluation Programme (EMEP) as well as Aerosol Mass Spectrometry (AMS) data measured in both Northern Hemisphere and tropical forest regions. All model simulations realistically predict the organic carbon mass observed in the Northern Hemisphere, although they tend to overestimate the concentrations in tropical forest regions. This overestimate may result from an unrealistically high uptake rate of glyoxal and methylglyoxal on aqueous aerosols and in cloud drops. The modeled OC in the free troposphere is in agreement with measurements in the ITCT-2K4 aircraft campaign over the North America and in pollution layers in Asia during the INTEX-B campaign, although the model underestimates OC in the free troposphere during the ACE-Asia campaign off the coast of Japan.
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Chen, J. P., T. S. Tsai i S. C. Liu. "Aerosol nucleation spikes in the planetary boundary layer". Atmospheric Chemistry and Physics Discussions 10, nr 11 (9.11.2010): 26931–59. http://dx.doi.org/10.5194/acpd-10-26931-2010.
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Abstract. Photochemically driven nucleation bursts, which typically occur in a few hours after sunrise, often produce strong aerosol number concentration (ANC) fluctuations. The causes of such ANC spikes were investigated using a detailed aerosol model running in the parcel mode. Two potential mechanisms for the ANC spikes are proposed and simulated. The blocking of actinic flux by scattered clouds can significantly influence new particle production, but this does not cause strong fluctuations in the number of aerosols within sizes greater than the detection limit of our measurements. A more plausible mechanism is the turbulence eddy effect. Strong aerosol nucleation may occur in both updrafts and downdrafts, while the cloud formation at the boundary layer top strongly reduces the number of aerosols. As the number of aerosols is sensitive to turbulence eddy and cloud formation properties, a changing turbulence condition would result in large fluctuations in the evolution of ANC similar to that observed at the surface.
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Chen, J. P., T. S. Tsai i S. C. Liu. "Aerosol nucleation spikes in the planetary boundary layer". Atmospheric Chemistry and Physics 11, nr 14 (21.07.2011): 7171–84. http://dx.doi.org/10.5194/acp-11-7171-2011.
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Abstract. Photochemically driven nucleation bursts, which typically occur within a few hours after sunrise, often produce strong aerosol number concentration (ANC) fluctuations. The causes of such ANC spikes were investigated using a detailed aerosol model running in the parcel mode. Two potential mechanisms for the ANC spikes were proposed and simulated. The blocking of actinic flux by scattered clouds can significantly influence new particle production, but this does not cause strong fluctuations in the number of aerosols within sizes greater than the detection limit of our measurements. A more plausible mechanism is the turbulence eddy effect. Strong aerosol nucleation may occur in both updrafts and downdrafts, while the cloud formation at the boundary layer top strongly reduces the number of aerosols. As the number of aerosols is sensitive to turbulence eddy and cloud formation properties, a changing turbulence condition would result in large fluctuations in the evolution of ANC similar to that observed at the surface.
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Dyson, Joanna E., Graham A. Boustead, Lauren T. Fleming, Mark Blitz, Daniel Stone, Stephen R. Arnold, Lisa K. Whalley i Dwayne E. Heard. "Production of HONO from NO<sub>2</sub> uptake on illuminated TiO<sub>2</sub> aerosol particles and following the illumination of mixed TiO<sub>2</sub>∕ammonium nitrate particles". Atmospheric Chemistry and Physics 21, nr 7 (16.04.2021): 5755–75. http://dx.doi.org/10.5194/acp-21-5755-2021.
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Abstract. The rate of production of HONO from illuminated TiO2 aerosols in the presence of NO2 was measured using an aerosol flow tube system coupled to a photo-fragmentation laser-induced fluorescence detection apparatus. The reactive uptake coefficient of NO2 to form HONO, γNO2→HONO, was determined for NO2 mixing ratios in the range 34–400 ppb, with γNO2→HONO spanning the range (9.97 ± 3.52) × 10−6 to (1.26 ± 0.17) × 10−4 at a relative humidity of 15 ± 1 % and for a lamp photon flux of (1.63 ± 0.09) ×1016 photons cm−2 s−1 (integrated between 290 and 400 nm), which is similar to midday ambient actinic flux values. γNO2→HONO increased as a function of NO2 mixing ratio at low NO2 before peaking at (1.26 ± 0.17) ×10-4 at ∼ 51 ppb NO2 and then sharply decreasing at higher NO2 mixing ratios rather than levelling off, which would be indicative of surface saturation. The dependence of HONO production on relative humidity was also investigated, with a peak in production of HONO from TiO2 aerosol surfaces found at ∼ 25 % RH. Possible mechanisms consistent with the observed trends in both the HONO production and reactive uptake coefficient were investigated using a zero-dimensional kinetic box model. The modelling studies supported a mechanism for HONO production on the aerosol surface involving two molecules of NO2, as well as a surface HONO loss mechanism which is dependent upon NO2. In a separate experiment, significant production of HONO was observed from illumination of mixed nitrate/TiO2 aerosols in the absence of NO2. However, no production of HONO was seen from the illumination of nitrate aerosols alone. The rate of production of HONO observed from mixed nitrate/TiO2 aerosols was scaled to ambient conditions found at the Cape Verde Atmospheric Observatory (CVAO) in the remote tropical marine boundary layer. The rate of HONO production from aerosol particulate nitrate photolysis containing a photocatalyst was found to be similar to the missing HONO production rate necessary to reproduce observed concentrations of HONO at CVAO. These results provide evidence that particulate nitrate photolysis may have a significant impact on the production of HONO and hence NOx in the marine boundary layer where mixed aerosols containing nitrate and a photocatalytic species such as TiO2, as found in dust, are present.
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Lin, G., J. E. Penner, S. Sillman, D. Taraborrelli i J. Lelieveld. "Global modeling of SOA formation from dicarbonyls, epoxides, organic nitrates and peroxides". Atmospheric Chemistry and Physics 12, nr 10 (31.05.2012): 4743–74. http://dx.doi.org/10.5194/acp-12-4743-2012.
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Abstract. Recent experimental findings indicate that secondary organic aerosol (SOA) represents an important and, under many circumstances, the major fraction of the organic aerosol burden. Here, we use a global 3-D model (IMPACT) to test the results of different mechanisms for the production of SOA. The basic mechanism includes SOA formation from organic nitrates and peroxides produced from an explicit chemical formulation, using partition coefficients based on thermodynamic principles together with assumptions for the rate of formation of low-volatility oligomers. We also include the formation of low-volatility SOA from the reaction of glyoxal and methylglyoxal on aqueous aerosols and cloud droplets as well as from the reaction of epoxides on aqueous aerosols. A model simulation including these SOA formation mechanisms gives an annual global SOA production of 120.5 Tg. The global production of SOA is decreased substantially to 90.8 Tg yr−1 if the HOx regeneration mechanism proposed by Peeters et al. (2009) is used. Model predictions with and without this HOx (OH and HO2 regeneration scheme are compared with multiple surface observation datasets, namely: the Interagency Monitoring of Protected Visual Environments (IMPROVE) for the United States, the European Monitoring and Evaluation Programme (EMEP), and aerosol mass spectrometry (AMS) data measured in both the Northern Hemisphere and tropical forest regions. All model simulations show reasonable agreement with the organic carbon mass observed in the IMPROVE network and the AMS dataset, however observations in Europe are significantly underestimated, which may be caused by an underestimation of primary organic aerosol emissions (POA) in winter and of emissions and/or SOA production in the summer. The modeled organic aerosol concentrations tend to be higher by roughly a factor of three when compared with measurements at three tropical forest sites. This overestimate suggests that more measurements and model studies are needed to examine the formation of organic aerosols in the tropics. The modeled organic carbon (OC) in the free troposphere is in agreement with measurements in the ITCT-2K4 aircraft campaign over North America and in pollution layers off Asia during the INTEX-B campaign, although the model underestimates OC in the free troposphere in comparison with the ACE-Asia campaign off the coast of Japan.
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He, Pengzhen, Becky Alexander, Lei Geng, Xiyuan Chi, Shidong Fan, Haicong Zhan, Hui Kang i in. "Isotopic constraints on heterogeneous sulfate production in Beijing haze". Atmospheric Chemistry and Physics 18, nr 8 (23.04.2018): 5515–28. http://dx.doi.org/10.5194/acp-18-5515-2018.
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Abstract. Discerning mechanisms of sulfate formation during fine-particle pollution (referred to as haze hereafter) in Beijing is important for understanding the rapid evolution of haze and for developing cost-effective air pollution mitigation strategies. Here we present observations of the oxygen-17 excess of PM2.5 sulfate (Δ17O(SO42−)) collected in Beijing haze from October 2014 to January 2015 to constrain possible sulfate formation pathways. Throughout the sampling campaign, the 12-hourly averaged PM2.5 concentrations ranged from 16 to 323 µg m−3 with a mean of (141 ± 88 (1σ)) µg m−3, with SO42− representing 8–25 % of PM2.5 mass. The observed Δ17O(SO42−) varied from 0.1 to 1.6 ‰ with a mean of (0.9 ± 0.3) ‰. Δ17O(SO42−) increased with PM2.5 levels in October 2014 while the opposite trend was observed from November 2014 to January 2015. Our estimate suggested that in-cloud reactions dominated sulfate production on polluted days (PDs, PM2.5 ≥ 75 µg m−3) of Case II in October 2014 due to the relatively high cloud liquid water content, with a fractional contribution of up to 68 %. During PDs of Cases I and III–V, heterogeneous sulfate production (Phet) was estimated to contribute 41–54 % to total sulfate formation with a mean of (48 ± 5) %. For the specific mechanisms of heterogeneous oxidation of SO2, chemical reaction kinetics calculations suggested S(IV) ( = SO2 ⚫ H2O + HSO3− + SO32−) oxidation by H2O2 in aerosol water accounted for 5–13 % of Phet. The relative importance of heterogeneous sulfate production by other mechanisms was constrained by our observed Δ17O(SO42−). Heterogeneous sulfate production via S(IV) oxidation by O3 was estimated to contribute 21–22 % of Phet on average. Heterogeneous sulfate production pathways that result in zero-Δ17O(SO42−), such as S(IV) oxidation by NO2 in aerosol water and/or by O2 via a radical chain mechanism, contributed the remaining 66–73 % of Phet. The assumption about the thermodynamic state of aerosols (stable or metastable) was found to significantly influence the calculated aerosol pH (7.6 ± 0.1 or 4.7 ± 1.1, respectively), and thus influence the relative importance of heterogeneous sulfate production via S(IV) oxidation by NO2 and by O2. Our local atmospheric conditions-based calculations suggest sulfate formation via NO2 oxidation can be the dominant pathway in aerosols at high-pH conditions calculated assuming stable state while S(IV) oxidation by O2 can be the dominant pathway providing that highly acidic aerosols (pH ≤ 3) exist. Our local atmospheric-conditions-based calculations illustrate the utility of Δ17O(SO42−) for quantifying sulfate formation pathways, but this estimate may be further improved with future regional modeling work.
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Swanson, William F., Chris D. Holmes, William R. Simpson, Kaitlyn Confer, Louis Marelle, Jennie L. Thomas, Lyatt Jaeglé i in. "Comparison of model and ground observations finds snowpack and blowing snow aerosols both contribute to Arctic tropospheric reactive bromine". Atmospheric Chemistry and Physics 22, nr 22 (15.11.2022): 14467–88. http://dx.doi.org/10.5194/acp-22-14467-2022.
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Abstract. Reactive halogens play a prominent role in the atmospheric chemistry of the Arctic during springtime. Field measurements and modeling studies suggest that halogens are emitted into the atmosphere from snowpack and reactions on wind-blown snow-sourced aerosols. The relative importance of snowpack and blowing snow sources is still debated, both at local scales and regionally throughout the Arctic. To understand the implications of these halogen sources on a pan-Arctic scale, we simulate Arctic reactive bromine chemistry in the atmospheric chemical transport model GEOS-Chem. Two mechanisms are included: (1) a blowing snow sea salt aerosol formation mechanism and (2) a snowpack mechanism assuming uniform molecular bromine production from all snow surfaces. We compare simulations including neither mechanism, each mechanism individually, and both mechanisms to examine conditions where one process may dominate or the mechanisms may interact. We compare the models using these mechanisms to observations of bromine monoxide (BrO) derived from multiple-axis differential optical absorption spectroscopy (MAX-DOAS) instruments on O-Buoy platforms on the sea ice and at a coastal site in Utqiaġvik, Alaska, during spring 2015. Model estimations of hourly and monthly average BrO are improved by assuming a constant yield of 0.1 % molecular bromine from all snowpack surfaces on ozone deposition. The blowing snow aerosol mechanism increases modeled BrO by providing more bromide-rich aerosol surface area for reactive bromine recycling. The snowpack mechanism led to increased model BrO across the Arctic Ocean with maximum production in coastal regions, whereas the blowing snow aerosol mechanism increases BrO in specific areas due to high surface wind speeds. Our uniform snowpack source has a greater impact on BrO mixing ratios than the blowing snow source. Model results best replicate several features of BrO observations during spring 2015 when using both mechanisms in conjunction, adding evidence that these mechanisms are both active during the Arctic spring. Extending our transport model throughout the entire year leads to predictions of enhanced fall BrO that are not supported by observations.
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Song, Shaojie, Meng Gao, Weiqi Xu, Yele Sun, Douglas R. Worsnop, John T. Jayne, Yuzhong Zhang i in. "Possible heterogeneous chemistry of hydroxymethanesulfonate (HMS) in northern China winter haze". Atmospheric Chemistry and Physics 19, nr 2 (1.02.2019): 1357–71. http://dx.doi.org/10.5194/acp-19-1357-2019.
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Abstract. The chemical mechanisms responsible for rapid sulfate production, an important driver of winter haze formation in northern China, remain unclear. Here, we propose a potentially important heterogeneous hydroxymethanesulfonate (HMS) chemical mechanism. Through analyzing field measurements with aerosol mass spectrometry, we show evidence for a possible significant existence in haze aerosols of organosulfur primarily as HMS, misidentified as sulfate in previous observations. We estimate that HMS can account for up to about one-third of the sulfate concentrations unexplained by current air quality models. Heterogeneous production of HMS by SO2 and formaldehyde is favored under northern China winter haze conditions due to high aerosol water content, moderately acidic pH values, high gaseous precursor levels, and low temperature. These analyses identify an unappreciated importance of formaldehyde in secondary aerosol formation and call for more research on sources and on the chemistry of formaldehyde in northern China winter.
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Flores, J. M., G. Bourdin, O. Altaratz, M. Trainic, N. Lang-Yona, E. Dzimban, S. Steinau i in. "Tara Pacific Expedition’s Atmospheric Measurements of Marine Aerosols across the Atlantic and Pacific Oceans: Overview and Preliminary Results". Bulletin of the American Meteorological Society 101, nr 5 (1.05.2020): E536—E554. http://dx.doi.org/10.1175/bams-d-18-0224.1.
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Abstract Marine aerosols play a significant role in the global radiative budget, in clouds’ processes, and in the chemistry of the marine atmosphere. There is a critical need to better understand their production mechanisms, composition, chemical properties, and the contribution of ocean-derived biogenic matter to their mass and number concentration. Here we present an overview of a new dataset of in situ measurements of marine aerosols conducted over the 2.5-yr Tara Pacific Expedition over 110,000 km across the Atlantic and Pacific Oceans. Preliminary results are presented here to describe the new dataset that will be built using this novel set of measurements. It will characterize marine aerosols properties in detail and will open a new window to study the marine aerosol link to the water properties and environmental conditions.
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Li, Siyuan, Dantong Liu, Shaofei Kong, Yangzhou Wu, Kang Hu, Huang Zheng, Yi Cheng i in. "Evolution of source attributed organic aerosols and gases in a megacity of central China". Atmospheric Chemistry and Physics 22, nr 10 (30.05.2022): 6937–51. http://dx.doi.org/10.5194/acp-22-6937-2022.
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Abstract. The secondary production of oxygenated organic aerosol (OOA) impacts air quality, climate, and human health. The importance of various sources in contributing to the OOA loading and associated different ageing mechanisms remains to be elucidated. Here we present a concurrent observation and factorization analysis on the mass spectra of organic aerosol (OA) by a high-resolution aerosol mass spectrometer and volatile organic compounds (VOCs) by a proton transfer reaction mass spectrometer in Wuhan, a megacity in central China, during autumn. The full mass spectra of organics with two principle anthropogenic sources were identified as the traffic and cooking sources, for their primary emission profiles in aerosol and gas phases, the evolutions, and their respective roles in producing OOA and secondary VOCs. Primary emissions in gas and aerosol phases both contributed to the production of OOA. The photooxidation of traffic sources from the morning rush hour caused a 2.5 fold increase in OOA mass in a higher oxidation state (oxygen-to-carbon ratio as O/C =0.72), co-producing gas phase carboxylic acids, while, at night, cooking aerosols and VOCs (particularly acrolein and hexanal) importantly caused the nocturnal formation of oxygenated intermediate VOCs, increasing OOA mass by a factor of 1.7 (O/C =0.42). The daytime and nighttime formation of secondary aerosols, as contributed by different sources, was found to be modulated by solar radiation and air moisture, respectively. The environmental policy should, therefore, consider the primary emissions and their respective ageing mechanisms influenced by meteorological conditions.
Rozprawy doktorskie na temat "Aerosols - Production Mechanisms"
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Wiegand, Aaron Nathaniel. "Modelling photochemical production of fine particulates in a toluene/NOx/water vapour system". Thesis, Queensland University of Technology, 1999. https://eprints.qut.edu.au/36975/1/36975_Digitised%20Thesis.pdf.
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This work investigates the computer modelling of the photochemical formation of smog products such as ozone and aerosol, in a system containing toluene, NOx and
water vapour. In particular, the problem of modelling this process in the Commonwealth Scientific and Industrial Research Organization (CSIRO) smog chambers, which utilize outdoor exposure, is addressed. The primary requirement for such modelling is a knowledge of the photolytic rate
coefficients. Photolytic rate coefficients of species other than N02 are often related to JNo2 (rate coefficient for the photolysis ofN02) by a simple factor, but for outdoor
chambers, this method is prone to error as the diurnal profiles may not be similar in shape. Three methods for the calculation of diurnal JNo2 are investigated. The most
suitable method for incorporation into a general model, is found to be one which determines the photolytic rate coefficients for N02, as well as several other species,
from actinic flux, absorption cross section and quantum yields. A computer model was developed, based on this method, to calculate in-chamber photolysis rate
coefficients for the CSIRO smog chambers, in which ex-chamber rate coefficients are adjusted by accounting for variation in light intensity by transmittance through
the Teflon walls, albedo from the chamber floor and radiation attenuation due to clouds. The photochemical formation of secondary aerosol is investigated in a series of toluene-NOx experiments, which were performed in the CSIRO smog chambers. Three stages of aerosol formation, in plots of total particulate volume versus time, are identified: a delay period in which no significant mass of aerosol is formed, a regime of rapid aerosol formation (regime 1) and a second regime of slowed aerosol formation (regime 2). Two models are presented which were developed from the experimental data. One model is empirically based on observations of discrete stages of aerosol formation and readily allows aerosol growth profiles to be calculated. The
second model is based on an adaptation of published toluene photooxidation mechanisms and provides some chemical information about the oxidation products.
Both models compare favorably against the experimental data.
The gross effects of precursor concentrations (toluene, NOx and H20) and ambient conditions (temperature, photolysis rate) on the formation of secondary aerosol are
also investigated, primarily using the mechanism model. An increase in [NOx]o results in increased delay time, rate of aerosol formation in regime 1 and volume of aerosol formed in regime 1. This is due to increased formation of dinitrocresol and furanone products. An increase in toluene results in a decrease in the delay time and
an increase in the rate of aerosol formation in regime 1, due to enhanced reactivity from the toluene products, such as the radicals from the photolysis of benzaldehyde.
Water vapor has very little effect on the formation of aerosol volume, except that rates are slightly increased due to more OH radicals from reaction with 0(1D) from
ozone photolysis. Increased temperature results in increased volume of aerosol formed in regime 1 (increased dinitrocresol formation), while increased photolysis
rate results in increased rate of aerosol formation in regime 1. Both the rate and volume of aerosol formed in regime 2 are increased by increased temperature or
photolysis rate.
Both models indicate that the yield of secondary particulates from hydrocarbons (mass concentration aerosol formed/mass concentration hydrocarbon precursor) is proportional to the ratio [NOx]0/[hydrocarbon]0
Książki na temat "Aerosols - Production Mechanisms"
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Lewis, Ernie R. Sea salt aerosol production: Mechanisms, methods, measurements and models : a critical review. Washington, DC: American Geophysical Union, 2004.
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Schwartz, Stephen E., i Ernie R. Lewis. Sea Salt Aerosol Production: Mechanisms, Methods, Measurements, and Models. Wiley & Sons, Limited, John, 2013.
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Sea Salt Aerosol Production: Mechanisms, Methods, Measurements, and Models - A Critical Review (Geophysical Monograph). Amer Geophysical Union, 2005.
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Kucharski, Fred, i Muhammad Adnan Abid. Interannual Variability of the Indian Monsoon and Its Link to ENSO. Oxford University Press, 2017. http://dx.doi.org/10.1093/acrefore/9780190228620.013.615.
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The interannual variability of Indian summer monsoon is probably one of the most intensively studied phenomena in the research area of climate variability. This is because even relatively small variations of about 10% to 20% from the mean rainfall may have dramatic consequences for regional agricultural production. Forecasting such variations months in advance could help agricultural planning substantially. Unfortunately, a perfect forecast of Indian monsoon variations, like any other regional climate variations, is impossible in a long-term prediction (that is, more than 2 weeks or so in advance). The reason is that part of the atmospheric variations influencing the monsoon have an inherent predictability limit of about 2 weeks. Therefore, such predictions will always be probabilistic, and only likelihoods of droughts, excessive rains, or normal conditions may be provided. However, even such probabilistic information may still be useful for agricultural planning. In research regarding interannual Indian monsoon rainfall variations, the main focus is therefore to identify the remaining predictable component and to estimate what fraction of the total variation this component accounts for. It turns out that slowly varying (with respect to atmospheric intrinsic variability) sea-surface temperatures (SSTs) provide the dominant part of the predictable component of Indian monsoon variability. Of the predictable part arising from SSTs, it is the El Niño Southern Oscillation (ENSO) that provides the main part. This is not to say that other forcings may be neglected. Other forcings that have been identified are, for example, SST patterns in the Indian Ocean, Atlantic Ocean, and parts of the Pacific Ocean different from the traditional ENSO region, and springtime snow depth in the Himalayas, as well as aerosols. These other forcings may interact constructively or destructively with the ENSO impact and thus enhance or reduce the ENSO-induced predictable signal. This may result in decade-long changes in the connection between ENSO and the Indian monsoon. The physical mechanism for the connection between ENSO and the Indian monsoon may be understood as large-scale adjustment of atmospheric heatings and circulations to the ENSO-induced SST variations. These adjustments modify the Walker circulation and connect the rising/sinking motion in the central-eastern Pacific during a warm/cold ENSO event with sinking/rising motion in the Indian region, leading to reduced/increased rainfall.
Części książek na temat "Aerosols - Production Mechanisms"
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Bharali, Bhagawan, Zafar Ullah, Bhupendra Haloi, Jayashree Chutia i Sonbeer Chack. "Phytotoxicity of Oxidised and Reduced Nitrogen Aerosols on Potato (Solanum Tuberosum L.) Crop". W Sustainable Potato Production and the Impact of Climate Change, 169–88. IGI Global, 2017. http://dx.doi.org/10.4018/978-1-5225-1715-3.ch008.
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In a field trial (2012), simulated aerosols: NH4Cl (reduced) and NaNO2 (oxidised) @ 10 & 20 kg ha-1y-1 (˜ 100 ppm & ˜ 200 ppm respectively), 1000 cm3m-2 of each along with a control were misted to population of Kufri Jyoti at different growth stages viz., vegetative (10-60 DAS), tuber initiation (60-90 DAS) and tuber bulking >90DAS). The higher dose of aerosols lowered nitrate reductase activity, nitrogen use efficiency, cell membrane stability, tuber yield, but increased photosynthesis, peroxidise activity significantly. The mechanisms of injury in terms of higher peroxidase activity and lower membrane stability of leaf cells have been elucidated. Foliar feeding of nitrogenous pollutant in the form of aerosols to plants at juvenile stage is important in addition to basal use of recommended fertilizers.
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Calvert, Jack G., John J. Orlando, William R. Stockwell i Timothy J. Wallington. "The Oxides of Nitrogen: Their Relation to Tropospheric Ozone". W The Mechanisms of Reactions Influencing Atmospheric Ozone. Oxford University Press, 2015. http://dx.doi.org/10.1093/oso/9780190233020.003.0006.
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Reactive (or “odd”) nitrogen is emitted into the atmosphere in a variety of forms, with the most important being NOx (NO and NO2), ammonia (NH3), and nitrous oxide (N2O). Emissions of these species into the atmosphere have been summarized, for example, by the IPCC Fourth Assessment Report (the AR4; IPCC, 2007). Some discussion of NOx emissions and trends has also been presented in Chapter I. Emissions of NOx are mainly the result of anthropogenic activity associated with fossil fuel combustion and industrial activity. For the 1990s, the AR4 estimates total anthropogenic NOx emissions of 33.4 TgN yr−1, with natural emissions (mostly from soil and lightning) accounting for an additional 8.4–13.7 TgN yr−1. Ammonia emissions are comparable in magnitude to those for NOx, with anthropogenic emissions (45.5 TgN yr−1) again exceeding natural emissions (10.6 TgN yr−1). Although the majority of the ammonia produces aerosols or is scavenged by aerosol and is subsequently lost from the atmosphere, some gas phase oxidation does occur, which can in part lead to NOx production. The N2O source strength is about 17.7 TgN yr−1, with natural sources outweighing anthropogenic ones (IPCC, 2007). However, N2O is essentially inert in the troposphere, and thus the vast majority of its photooxidation and concomitant NOx release occurs in the stratosphere. The major NOx − related reactions occurring in the Earth’s troposphere are summarized in Figure III-A-1. As just alluded to, the species NO and NO2 are jointly referred to as NOx and are often treated collectively. This is because, under daytime conditions, these two species are rapidly interconverted, with the interconversion occurring on a much shorter timescale than the loss of either species.
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Calvert, Jack G., John J. Orlando, William R. Stockwell i Timothy J. Wallington. "Chemical Mechanisms for Air Quality Modeling and Their Applications". W The Mechanisms of Reactions Influencing Atmospheric Ozone. Oxford University Press, 2015. http://dx.doi.org/10.1093/oso/9780190233020.003.0012.
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A chemical mechanism is a critical component of an air quality model. Tropospheric gas phase chemical mechanisms for air quality modeling are designed to simulate the production of ozone, acids, and aerosol precursors. Therefore, their focus is on the oxidation chemistry of ozone, nitrogen oxides, sulfur compounds, and organic compounds. Figure IX-A-1 is an overview of the most important cycles of radicals that must be represented in a chemical mechanism for air quality modeling. The processes shown schematically on one level may appear to be relatively simple, but, in reality, the chemical mechanism is extremely complicated due to the very large number of organic compounds present in the atmosphere. Atmospheric chemistry mechanisms are based on laboratory data and tested against environmental experiments and field measurements (Stockwell et al., 2012). Usually, the mechanism is considered to consist of chemical species and their reactions and rate coefficients, along with the photochemical data (used to calculate photolysis frequencies). An atmospheric chemical mechanism employed in an air quality model could be considered to include the rules for aggregating emissions and initial concentrations into species (Middleton et al., 1990). There are many thousands of volatile organic compounds (VOCs) emitted into the atmosphere, and each has its own decomposition mechanism that determines the effect of the VOC on ozone production. It is critical for a chemical mechanism to characterize the chemistry of the VOCs and their differences in chemical reactivity as accurately as possible. Middleton et al. (1990) pointed out that air quality models have only a limited number of species compared to emission inventories. An emissions aggregation scheme is the process of mapping a detailed emissions inventory into the limited number of species used in an air quality model. The scheme is an important component of any model chemical mechanism. Middleton et al. published their aggregation process for the mechanism used in the Regional Acid Deposition Model (RADM2, Stockwell et al., 1990), but, too often, the emissions aggregation scheme for a given chemical mechanism is in the gray literature and difficult to access.
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Calvert, Jack G., John J. Orlando, William R. Stockwell i Timothy J. Wallington. "The Impact of Inorganic Trace Gases on Ozone in the Atmosphere". W The Mechanisms of Reactions Influencing Atmospheric Ozone. Oxford University Press, 2015. http://dx.doi.org/10.1093/oso/9780190233020.003.0010.
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A major focus of the previous six chapters has been on the chemistry and interactions of the HOx, NOx, and volatile organic compound (VOC) families. Details of the reactions of O3 NO3, and HO that act to initiate VOC oxidation have been presented, as has the ensuing chemistry involving organic peroxy and alkoxy radicals and their interactions with NOx. In this chapter, we complete our discussion of thermal chemical reactions that impact tropospheric ozone. The chapter begins with a discussion of the budgets of two simple (inorganic) carbon-containing species not yet discussed, carbon dioxide (CO2) and carbon monoxide (CO). Although CO2 is not directly involved in ozone-related tropospheric chemistry, it is of course the species most critical to discussions of global climate change, and thus a very brief overview of its concentrations, sources, and sinks is presented. CO is a ubiquitous global pollutant, and its reaction with HO is an essential part of the tropospheric background chemistry. This is followed by a presentation of the tropospheric chemistry of halogen species, beginning with a discussion of inorganic halogen cycles that impact (in particular) the ozone chemistry of the marine boundary layer (MBL) and concluding with a detailed presentation of the reactions of Cl atoms and Br atoms with VOC species. The chapter concludes with an overview of tropospheric sulfur chemistry. The reactions leading to the oxidation of inorganic (SO2 and SO3) as well as organic sulfur compounds (e.g., DMS, CH3SCH3) are detailed, and a brief discussion of the effects of the oxidation of sulfur species on aerosol production in the troposphere and stratosphere is also given. The abundance of CO2 in the atmosphere has obviously received a great deal of attention in recent decades due to the influence of this gas on Earth’s climate system. Indeed, changes in the atmospheric CO2 concentration represent the single largest contributor to changes in radiative forcing since preindustrial times (c. 1750). The atmospheric burden of CO2 is controlled by the processes that make up the global carbon cycle—the exchanges of carbon (mostly in the form of CO2) between various “reservoirs,” including the atmosphere, land (vegetation and soil), the surface ocean, the intermediate and deep ocean, sediment on the ocean floor, and the fossil fuel reservoir (IPCC, 2007).
Streszczenia konferencji na temat "Aerosols - Production Mechanisms"
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Nuñez, M. Hidalgo, P. Cavalli, G. A. Petrucci i N. Omenetto. "Feasibility Study of On-line Detection of Sulphuric Acid Aerosols in the Atmosphere by Laser Photofragmentation and Plasma Spectroscopy". W Laser Applications to Chemical and Environmental Analysis. Washington, D.C.: Optica Publishing Group, 1998. http://dx.doi.org/10.1364/lacea.1998.ltud.1.
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A major interest of our Institute lies in the study of the atmospheric sulphur cycle and in the oxidation mechanism(s) of Dimethylsulfide (DMS) in air. DMS originates from the ocean biota and its crucial role in the formation of atmospheric aerosols is well-documented (1,2). When DMS is oxidized, it generates SO2 that can be further oxidized to H2SO4, inducing the production and growth of new aerosol particles that can act as cloud condensation nuclei and affect the Earth’s albedo (2). The possibility of detecting sulphuric acid aerosols with laser excitation has been discussed, to the best of our knowledge, only in one paper (3), where the aerosols generated by mixing SO3 and H2O were addressed with laser photons at 193 nm. The resulting broadband emission was attributed to sulphuric acid and was similar to the emission spectrum of gaseous SO2.
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Ju, C., J. Sun, D. J. Michalek i J. W. Sutherland. "Application of an Imaging System to Study Machining Mist Formation via an Atomization Mechanism". W ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-32033.
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Airborne inhalable particulate in the workplace represents a significant health hazard. One of the primary sources of this particulate is mist produced through the application of cutting fluids in machining operations. One of the important mechanisms for the production of cutting fluid mist is the atomization mechanism. In this paper, atomization is studied by applying cutting fluid to a rotating workpiece such as found in turning. An imaging system is presented for the study of the atomization mechanism. The imaging system extends the size measurement range typically achievable with aerosol sampling devices to consider larger particles. Experimental observations from the imaging system reveal that workpiece rotation speed and cutting fluid flow rate have significant effects on the size of the droplets produced by the atomization mechanism. With respect to atomization, the technical literature describes models for fluid interaction with the rotating workpiece and droplet formation via drop and ligament formation modes. Experimental measurements are compared with model predictions. For a range of rotation speeds and fluid application flow rates, the experimental data is seen to compare favorably with the model predictions.
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Goel, Paridhi, i Arun K. Nayak. "Numerical Investigation of Aerosol Collection Efficiency in a Venturi Scrubber". W 2018 26th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/icone26-82489.
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In an extreme situation, as happened in Fukushima nuclear power plant, the failure of multiple safety systems may lead to severe core damage and melt relocation. This may be accompanied by production of large amount of steam which may result in the over-pressurization of the containment. Another associated concern is that the exposed core melt is highly radioactive which if exposed to the atmosphere can ruthlessly deteriorate the quality of environment and living beings. The radioactive materials present in the containment can be in vapor form or aerosol form. The containment of a nuclear power plant is therefore the final shielding to prevent the release of radioactive products to the environment. Therefore, the installation of Filtered Containment Venting system (FCVS) is mandatory in a nuclear reactor which actuates passively to depressurize the containment. Additionally it assists in the retention of radionuclides in the containment. The FCVS consists of venturi scrubbers submerged in a pool of scrubbing liquid along with a demister housed in a scrubber tank. The performance of venturi scrubber is dependent on the interaction of the contaminated air stream from the nuclear reactor with the scrubbing liquid. This represents a multi-field and multi-fluid system. The present analysis investigates this system through a computational framework in which air stream is solved using Eulerian framework while the scrubbing liquid is tracked through Lagrangian framework. The collection efficiency of aerosols is modeled assuming impaction to be the predominant mechanism.
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Al-Safran, Eissa, Batoul Al-Ali i Hessah Alrashidi. "Evaluation and Modeling of Asphaltene Deposition in Oil Wells". W SPE Annual Technical Conference and Exhibition. SPE, 2021. http://dx.doi.org/10.2118/206366-ms.
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Abstract Asphaltene deposition in oil wells is a challenging flow-assurance phenomenon that affects the well production, project economics, and operational safety. While asphaltene precipitation is governed by the hydrocarbon mixture thermodynamics, Asphaltene deposition is governed by the complexity of flow hydrodynamic behavior and characteristics. This study aims to evaluate and compare the performance of the existing asphaltene deposition models and improve the current theoretical understanding of the deposition phenomenon by developing better predictive asphaltene deposition model. A large experimental database is collected, including aerosol and asphaltene particles deposition in air and crude oil systems, respectively, to carry on the evaluation. The results of this study revealed that Kor and Kharrat (2017) model of transport coefficient, which accounts for both diffusional and inertial deposition mechanisms outperformed other models in matching the transport coefficient from aerosol/air data. In addition, an improved sticking probability model is proposed in this study, and curve fitted using corrected deposition flux data to obtain the model constant. The improved model is not only physically sound, i.e. SP≥1, but also it requires less input data than other models. A validation study of the improved model shows a slight over prediction of experimental data with an absolute average error of 6.8% and standard deviation of 11.4%. The significance of this work is to provide theoretical predictive tool for asphaltene deposition in pipes to enable prevention, mitigation, and management of oil field asphaltene deposition strategies.
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Ma, L., M. C. Pourkashanian i C. W. Wilson. "A CFD Model for Reacting Flows in an Aero-Engine Hot End Simulator". W ASME Turbo Expo 2005: Power for Land, Sea, and Air. ASMEDC, 2005. http://dx.doi.org/10.1115/gt2005-68077.
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This paper presents a three-dimensional CFD model that numerically simulates the physical and chemical species transformations in the aero-engine turbine and nozzle aimed at contributing to an improved understanding of the minor species emitted by the aircraft, in particular the production of the gaseous aerosol precursors such as SO3, H2SO4 and HONO within the aircraft engine. The results presented are for the model applications to an aero-engine Hot End Simulator (HES). The HES was designed in the PARTEMIS programme to recreate the thermodynamic profile in the turbine and nozzle through which the hot gases pass after leaving the combustor so that detailed measurements can be made within the HES providing key boundary conditions and validations to the CFD model predictions. A detailed sulphur reaction mechanism has been incorporated in the numerical model, together with hydrocarbon-air and nitrogen chemistry, so that the effect of both engine condition and fuel sulphur content on the sulphur IV to VI conversion, as well as NOx/NOy conversion, in the post combustor region can be numerically predicted. For the two operational conditions studied, it is noted that there is still a significant portion of sulphur conversions taking place within the HES, although they are smaller when compared with the sulphur conversions that take place in the combustor. Overall conversion efficiencies of about 3.2% and 2.8% have been predicted for the Cruise and the Modern conditions studied, respectively, of which 0.6% and 0.7% were predicted occurring within the HES, respectively. The CFD predictions compared well with the available data from the HES measurements, although considerable uncertainties in the model input exist. The modelling results suggest that reasonable predictions can be obtained for the fluid flow, heat transfer and the chemical species transformations that occur in the turbine and nozzle, particularly for some of the unstable species that are not readily obtained through measurements. These results could also provide useful information/boundary conditions for the subsequent post engine modelling of the new particulate materials formed within the aircraft wake.
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Hamilton, Ian S., Donald A. Halter, Donald F. Haumann, Erich H. Fruchtnicht i Matthew G. Arno. "Characterization of NORM Sources in Petroleum Coke Calcining Processes". W ASME 2009 12th International Conference on Environmental Remediation and Radioactive Waste Management. ASMEDC, 2009. http://dx.doi.org/10.1115/icem2009-16314.
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Petroleum coke, or “petcoke,” is a waste by-product of the oil refining industry. The majority of petcoke consumption is in energy applications; catalyst coke is used as refinery fuel, anode coke for electricity conduction, and marketable coke for heating cement kilns. Roskill has predicted that long-term growth in petroleum coke production will be maintained, and may continue to increase slightly through 2012. Petcoke must first be calcined to drive off any undesirable petroleum by-products that would shorten the coke product-life cycle. As an example, the calcining process can take place in large, rotary kilns heated to maximum temperatures as high as approximately 1400–1540°C. The kilns and combustion/settling chambers, as well as some cooler units, are insulated with refractory bricks and other, interstitial materials, e.g., castable refractory materials, to improve the efficiency of the calcining process. The bricks are typically made of 70–85-percent bauxite, and are slowly worn away by the calcining process; bricks used to line the combustion chambers wear away, as well, but at a slower rate. It has been recognized that the refractory materials contain slight amounts of naturally occurring radioactive materials (NORM) from the uranium- and thorium-decay series. Similarly, low levels of NORM could be present in the petcoke feed stock given the nature of its origin. Neither the petcoke nor the refractory bricks represent appreciable sources of radiation or radioactive waste. However, some of the demolished bricks that have been removed from service because of the aforementioned wearing process have caused portal alarms to activate at municipal disposal facilities. This has lead to the current investigation into whether there is a NORM concentrating mechanism facilitated by the presence of the slightly radioactive feed stock in the presence of the slightly radioactive refractory materials, at calcining-zone temperatures. Research conducted to date has been used to determine the speciation and concentration of nuclides in both the feed stock and the various refractory materials, as well as the slag that forms at the interface of the two materials, as a function of temperature. Further investigation into any potential for generation of a NORM hazard as a result of refractory demolition has been conducted. Aerosol generation (mass loading), particle size distribution, and pulmonary solubility class have been investigated as a function of demolition-task description. In addition, external radiation levels in the kilns, chambers and waste piles, as a function of temperature profile and brick/operating history have been investigated.
Raporty organizacyjne na temat "Aerosols - Production Mechanisms"
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Meskhidze, Nicholas. Production Mechanism, Number Concentration, Size Distribution, Chemical Composition, and Optical Properties of Sea Spray Aerosols Workshop, Summer 2012. Office of Scientific and Technical Information (OSTI), październik 2013. http://dx.doi.org/10.2172/1096933.
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