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Cheng, Chunlei, Zuzhao Huang, Chak K. Chan, Yangxi Chu, Mei Li, Tao Zhang, Yubo Ou et al. „Characteristics and mixing state of amine-containing particles at a rural site in the Pearl River Delta, China“. Atmospheric Chemistry and Physics 18, Nr. 12 (29.06.2018): 9147–59. http://dx.doi.org/10.5194/acp-18-9147-2018.
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Abstract. Particulate amines play an important role for the particle acidity and hygroscopicity and also contribute to secondary organic aerosol mass. We investigated the sources and mixing states of particulate amines using a single-particle aerosol mass spectrometer (SPAMS) during summer and winter 2014 at a rural site in the Pearl River Delta, China. Amine-containing particles accounted for 11.1 and 9.4 % of the total detected individual particles in summer and winter, respectively. Although the increase in amine-containing particle counts mostly occurred at night, no obvious correlations between amine-containing particles and ambient relative humidity (RH) were found during the sampling period. Among the three markers we considered, the most abundant amine marker was 74(C2H5)2NH2+, which was detected in 90 and 86 % of amine-containing particles in summer and winter, followed by amine marker ions of 59(CH3)3N+, and 86(C2H5)2NCH2+ which were detected in less than 10 % of amine-containing particles during sampling period. The amine-containing particles were characterized by high fractions of carbonaceous marker ions, carbon–nitrogen fragments, sulfate, and nitrate in both summer and winter. More than 90 % of amine-containing particles were found to be internally mixed with sulfate throughout the sampling period, while the percentage of amine particles containing nitrate increased from 43 % in summer to 69 % in winter. Robust correlations between the peak intensities of amines, sulfate, and nitrate were observed, suggesting the possible formation of aminium sulfate and nitrate salts. Interestingly, only 8 % of amine particles contained ammonium in summer, while the percentage increased dramatically to 54 % in winter, indicating a relatively ammonium-poor state in summer and an ammonium-rich state in winter. The total ammonium-containing particles were investigated and showed a much lower abundance in ambient particles in summer (3.6 %) than that in winter (32.6 %), which suggests the ammonium-poor state of amine-containing particles in summer may be related to the lower abundance of ammonia/ammonium in gas and particle phases. In addition, higher abundance of amines in ammonium-containing particles than that of ammonium in amine-containing particles suggests a possible contribution of ammonium–amine exchange reactions to the low abundance of ammonium in amine-containing particles at high ambient RH (72 ± 13 %) in summer. The particle acidity of amine-containing particles is estimated via the relative acidity ratio (Ra), which is defined as the ratio of the sum of the sulfate and nitrate peak areas divided by the ammonium peak area. The Ra was 326 ± 326 in summer and 31 ± 13 in winter, indicating that the amine-containing particles were more acidic in summer than in winter. However, after including amines along with the ammonium in the acidity calculation, the new Ra′ values showed no seasonal change in summer (11 ± 4) and winter (10 ± 2), which suggests that amines could be a buffer for the particle acidity of ammonium-poor particles.
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Peng, Weihan, Cavan McCaffery, Niina Kuittinen, Topi Rönkkö, David R. Cocker und Georgios Karavalakis. „Secondary Organic and Inorganic Aerosol Formation from a GDI Vehicle under Different Driving Conditions“. Atmosphere 13, Nr. 3 (08.03.2022): 433. http://dx.doi.org/10.3390/atmos13030433.
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This study investigated the primary emissions and secondary aerosol formation from a gasoline direct injection (GDI) passenger car when operated over different legislative and real-world driving cycles on a chassis dynamometer. Diluted vehicle exhaust was photooxidized in a 30 m3 environmental chamber. Results showed elevated gaseous and particulate emissions for the cold-start cycles and higher secondary organic aerosol (SOA) formation, suggesting that cold-start condition will generate higher concentrations of SOA precursors. Total secondary aerosol mass exceeded primary PM emissions and was dominated by inorganic aerosol (ammonium and nitrate) for all driving cycles. Further chamber experiments in high temperature conditions verified that more ammonium nitrate nucleates to form new particles, forming a secondary peak in particle size distribution instead of condensing to black carbon particles. The results of this study revealed that the absorption of radiation by black carbon particles can lead to changes in secondary ammonium nitrate formation. Our work indicates the potential formation of new ammonium nitrate particles during low temperature conditions favored by the tailpipe ammonia and nitrogen oxide emissions from gasoline vehicles.
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Hauglustaine, D. A., Y. Balkanski und M. Schulz. „A global model simulation of present and future nitrate aerosols and their direct radiative forcing of climate“. Atmospheric Chemistry and Physics 14, Nr. 20 (21.10.2014): 11031–63. http://dx.doi.org/10.5194/acp-14-11031-2014.
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Abstract. The ammonia cycle and nitrate particle formation are introduced into the LMDz-INCA (Laboratoire de Météorologie Dynamique, version 4 – INteraction with Chemistry and Aerosols, version 3) global model. An important aspect of this new model is that both fine nitrate particle formation in the accumulation mode and coarse nitrate forming on existing dust and sea-salt particles are considered. The model simulates distributions of nitrates and related species in agreement with previous studies and observations. The calculated present-day total nitrate direct radiative forcing since the pre-industrial is −0.056 W m−2. This forcing corresponds to 18% of the sulfate forcing. Fine particles largely dominate the nitrate forcing, representing close to 90% of this value. The model has been used to investigate the future changes in nitrates and direct radiative forcing of climate based on snapshot simulations for the four representative concentration pathway (RCP) scenarios and for the 2030, 2050, and 2100 time horizons. Due to a decrease in fossil fuel emissions in the future, the concentration of most of the species involved in the nitrate–ammonium–sulfate system drop by 2100 except for ammonia, which originates from agricultural practices and for which emissions significantly increase in the future. Despite the decrease of nitrate surface levels in Europe and North America, the global burden of accumulation mode nitrates increases by up to a factor of 2.6 in 2100. This increase in ammonium nitrate in the future arises despite decreasing NOx emissions due to increased availability of ammonia to form ammonium nitrate. The total aerosol direct forcing decreases from its present-day value of −0.234 W m−2 to a range of −0.070 to −0.130 W m−2 in 2100 based on the considered scenario. The direct forcing decreases for all aerosols except for nitrates, for which the direct negative forcing increases to a range of −0.060 to −0.115 W m−2 in 2100. Including nitrates in the radiative forcing calculations increases the total direct forcing of aerosols by a factor of 1.3 in 2000, by a factor of 1.7–2.6 in 2030, by 1.9–4.8 in 2050, and by 6.4–8.6 in 2100. These results show that the agricultural emissions of ammonia will play a key role in the future mitigation of climate change, with nitrates becoming the dominant contributor to the anthropogenic aerosol optical depth during the second half of the 21st century and significantly increasing the calculated aerosol direct forcing. This significant increase in the influence that nitrate exerts on climate in the future will at the same time affect regional air quality and nitrogen deposition to the ecosystem.
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Myhre, G., und A. Grini. „Modelling of nitrate particles: importance of sea salt“. Atmospheric Chemistry and Physics Discussions 6, Nr. 1 (22.02.2006): 1455–80. http://dx.doi.org/10.5194/acpd-6-1455-2006.
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Abstract. A thermo dynamical model for treatment of gas/aerosol partitioning of semi volatile inorganic aerosols has been implemented in a global chemistry and aerosol transport model (Oslo CTM2). The sulphur cycle and sea salt particles have been implemented earlier in the Oslo CTM2 and the focus of this study is on whether nitrate particles are formed as fine mode ammonium nitrate or react on existing sea salt particles. The model results show that ammonium nitrate particles play a non-negligible role in the total aerosol composition in certain industrialized regions and therefore have a significant local radiative forcing. On a global scale the aerosol optical depth of ammonium nitrate is relatively small due to limited availability of ammonia and reaction with sea salt particles. Inclusion of sea salt in the calculations reduces the aerosol optical depth and burden of ammonium nitrate particles by 25% on a global scale but with large regional variations.
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Hauglustaine, D. A., Y. Balkanski und M. Schulz. „A global model simulation of present and future nitrate aerosols and their direct radiative forcing of climate“. Atmospheric Chemistry and Physics Discussions 14, Nr. 5 (14.03.2014): 6863–949. http://dx.doi.org/10.5194/acpd-14-6863-2014.
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Abstract. The ammonia cycle and nitrate particle formation have been introduced in the LMDz-INCA global model. Both fine nitrate particles formation in the accumulation mode and coarse nitrate forming on existing dust and sea-salt particles are considered. The model simulates distributions of nitrates and related species in agreement with previous studies and observations. The calculated present-day total nitrate direct radiative forcing since the pre-industrial is −0.056 W m−2. This forcing has the same magnitude than the forcing associated with organic carbon particles and represents 18% of the sulfate forcing. Fine particles largely dominate the nitrate forcing representing close to 90% of this value. The model has been used to investigate the future changes in nitrates and direct radiative forcing of climate based on snapshot simulations for the four Representative Concentration Pathway (RCP) scenarios and for the 2030, 2050 and 2100 time horizons. Due to a decrease in fossil fuel emissions in the future, the concentrations of most of the species involved in the nitrate-ammonium-sulfate system drop by 2100 except for ammonia which originates from agricultural practices and for which emissions significantly increase in the future. Despite the decrease of nitrate surface levels in Europe and Northern America, the global burden of accumulation mode nitrates increases by up to a factor of 2.6 in 2100. This increase in nitrate in the future arises despite decreasing NOx emissions due to increased availability of ammonia to form ammonium nitrate. The total aerosol direct forcing decreases from its present-day value of −0.234 W m−2 to a range of −0.070 to −0.130 W m−2 in 2100 based on the considered scenario. The direct forcing decreases for all aerosols except for nitrates for which the direct negative forcing increases to a range of −0.060 to −0.115 W m−2 in 2100. Including nitrates in the radiative forcing calculations increases the total direct forcing of aerosols by a factor of 1.3 in 2000, by a factor of 1.7–2.6 in 2030, by 1.9–4.8 in 2050 and by 6.4–8.6 in 2100. These results show that agricultural emissions of ammonia will play a key role in the future mitigation of climate change with nitrates becoming the dominant contributor to the anthropogenic aerosol optical depth during the second half of the XXIst century and significantly increasing the calculated aerosol direct forcing. This significant increase in the influence that nitrate exert on climate in the future will at the same time affect regional air quality and nitrogen deposition to the ecosystems.
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Schneider, Johannes, Stephan Mertes, Dominik van Pinxteren, Hartmut Herrmann und Stephan Borrmann. „Uptake of nitric acid, ammonia, and organics in orographic clouds: mass spectrometric analyses of droplet residual and interstitial aerosol particles“. Atmospheric Chemistry and Physics 17, Nr. 2 (31.01.2017): 1571–93. http://dx.doi.org/10.5194/acp-17-1571-2017.
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Abstract. Concurrent in situ analyses of interstitial aerosol and cloud droplet residues have been conducted at the Schmücke mountain site during the Hill Cap Cloud Thuringia campaign in central Germany in September and October 2010. Cloud droplets were sampled from warm clouds (temperatures between −3 and +16 °C) by a counterflow virtual impactor and the submicron-sized residues were analyzed by a compact time-of-flight aerosol mass spectrometer (C-ToF-AMS), while the interstitial aerosol composition was measured by an high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). During cloud-free periods, the submicron out-of-cloud aerosol was analyzed using both instruments, allowing for intercomparison between the two instruments. Further instrumentation included black carbon measurements and optical particle counters for the aerosol particles as well as optical sizing instrumentation for the cloud droplets. The results show that, under cloud conditions, on average 85 % of the submicron aerosol mass partitioned into the cloud liquid phase. Scavenging efficiencies of nitrate, ammonium, sulfate, and organics ranged between 60 and 100 %, with nitrate having, in general, the highest values. For black carbon, the scavenging efficiency was markedly lower (about 24 %). The nitrate and ammonium mass fractions were found to be markedly enhanced in cloud residues, indicating uptake of gaseous nitric acid and ammonia into the aqueous phase. This effect was found to be temperature dependent: at lower temperatures, the nitrate and ammonium mass fractions in the residues were higher. Also, the oxidation state of the organic matter in cloud residues was found to be temperature dependent: the O : C ratio was lower at higher temperatures. A possible explanation for this observation is a more effective uptake and/or higher concentrations of low-oxidized water-soluble volatile organic compounds, possibly of biogenic origin, at higher temperatures. Organic nitrates were observed in cloud residuals as well as in the out-of-cloud aerosol, but no indication of a preferred partitioning of organic nitrates into the aqueous phase or into the gas phase was detected. Assuming the uptake of nitric acid and ammonia in cloud droplets will be reversible, it will lead to a redistribution of nitrate and ammonium among the aerosol particles, leading to more uniform, internally mixed particles after several cloud passages.
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Wu, Can, Cong Cao, Jianjun Li, Shaojun Lv, Jin Li, Xiaodi Liu, Si Zhang et al. „Different physicochemical behaviors of nitrate and ammonium during transport: a case study on Mt. Hua, China“. Atmospheric Chemistry and Physics 22, Nr. 23 (13.12.2022): 15621–35. http://dx.doi.org/10.5194/acp-22-15621-2022.
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Abstract. To understand the chemical evolution of aerosols in the transport process, the chemistry of PM2.5 and nitrogen isotope compositions on the mountainside of Mt. Hua (∼1120 m above sea level, a.s.l.) in inland China during the 2016 summertime were investigated and compared with parallel observations collected at surface sampling site (∼400 m a.s.l.). The PM2.5 exhibited a high level at the mountain foot site (MF; average 76.0±44.1 µg m−3) and could be transported aloft by anabatic valley winds, leading to the gradual accumulation of daytime PM2.5 with a noon peak at the mountainside sampling site (MS). As the predominant ion species, sulfate exhibited nearly identical mass concentrations at both sites, but its PM2.5 mass fraction was moderately enhanced by ∼4 % at the MS site. The ammonium variations were similar to the sulfate variations, the chemical forms of both of which mainly existed as ammonium bisulfate (NH4HSO4) and ammonium sulfate ((NH4)2SO4) at the MF and MS sites, respectively. Unlike sulfate and ammonium, nitrate mainly existed as ammonium nitrate (NH4NO3) in fine particles and exhibited decreasing mass concentration and proportion trends with increasing elevation. This finding was ascribed to NH4NO3 volatilization, in which gaseous HNO3 from semi-volatile NH4NO3 subsequently reacted with dust particles to form nonvolatile salts, resulting in significant nitrate shifts from fine particles into coarse particles. Such scavenging of fine-particle nitrate led to an enrichment in the daytime 15N of nitrate at the MS site compared with to the MF site. In contrast to nitrate, at the MS site, the 15N in ammonium depleted during the daytime. Considering the lack of any significant change in ammonia (NH3) sources during the vertical transport process, this 15N depletion in ammonium was mainly the result of unidirectional reactions, indicating that additional NH3 would partition into particulate phases and further neutralize HSO4- to form SO42-. This process would reduce the aerosol acidity, with a higher pH (3.4±2.2) at the MS site and lower ones (2.9±2.0) at the MF site. Our work provides more insight into physicochemical behaviors of semi-volatile nitrate and ammonium, which will facilitate the improvement in the model for a better simulation of aerosol composition and properties.
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Richardson, C. B., und R. L. Hightower. „Evaporation of ammonium nitrate particles“. Atmospheric Environment (1967) 21, Nr. 4 (Januar 1987): 971–75. http://dx.doi.org/10.1016/0004-6981(87)90092-8.
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Xu, Xiao Juan, Xu Dong Sun, Ya Qiu Liang und Wei Qiu. „Synthesis of Uniform Spherical Alumina Powders by Homogeneous Precipitation“. Applied Mechanics and Materials 341-342 (Juli 2013): 100–104. http://dx.doi.org/10.4028/www.scientific.net/amm.341-342.100.
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Uniform spherical alumina powders have been synthesized via homogeneous precipitation method from aluminum nitrate using urea as the precipitant. The amount of ammonium sulfate has a significant effect on morphology and particle size of the precursor powders. It was found that spherical particles can be obtained when the molar ratio of ammonium sulfate to aluminum nitrate is about 0.72 and the concentration of the aluminum nitrate is 0.005M. Spherical alumina particles with 400 nm in diameter were obtained by calcining the precursors at 1100°C for 4 hrs.
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Hightower, R. L., und C. B. Richardson. „Evaporation of ammonium nitrate particles containing ammonium sulfate“. Atmospheric Environment (1967) 22, Nr. 11 (Januar 1988): 2587–91. http://dx.doi.org/10.1016/0004-6981(88)90492-1.
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Kutzner, Rebecca D., Juan Cuesta, Pascale Chelin, Jean-Eudes Petit, Mokhtar Ray, Xavier Landsheere, Benoît Tournadre et al. „Diurnal evolution of total column and surface atmospheric ammonia in the megacity of Paris, France, during an intense springtime pollution episode“. Atmospheric Chemistry and Physics 21, Nr. 15 (12.08.2021): 12091–111. http://dx.doi.org/10.5194/acp-21-12091-2021.
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Abstract. Ammonia (NH3) is a key precursor for the formation of atmospheric secondary inorganic particles, such as ammonium nitrate and sulfate. Although the chemical processes associated with the gas-to-particle conversion are well known, atmospheric concentrations of gaseous ammonia are still scarcely characterized. However, this information is critical, especially for processes concerning the equilibrium between ammonia and ammonium nitrate, due to the semivolatile character of the latter. This study presents an analysis of the diurnal cycle of atmospheric ammonia during a pollution event over the Paris megacity region in spring 2012 (5 d in late March 2012). Our objective is to analyze the link between the diurnal evolution of surface NH3 concentrations and its integrated column abundance, meteorological variables and relevant chemical species involved in gas–particle partitioning. For this, we implement an original approach based on the combined use of surface and total column ammonia measurements. These last ones are derived from ground-based remote sensing measurements performed by the Observations of the Atmosphere by Solar Infrared Spectroscopy (OASIS) Fourier transform infrared observatory at an urban site over the southeastern suburbs of the Paris megacity. This analysis considers the following meteorological variables and processes relevant to the ammonia pollution event: temperature, relative humidity, wind speed and direction, and the atmospheric boundary layer height (as indicator of vertical dilution during its diurnal development). Moreover, we study the partitioning between ammonia and ammonium particles from concomitant measurements of total particulate matter (PM) and ammonium (NH4+) concentrations at the surface. We identify the origin of the pollution event as local emissions at the beginning of the analyzed period and advection of pollution from Benelux and western Germany by the end. Our results show a clearly different diurnal behavior of atmospheric ammonia concentrations at the surface and those vertically integrated over the total atmospheric column. Surface concentrations remain relatively stable during the day, while total column abundances show a minimum value in the morning and rise steadily to reach a relative maximum in the late afternoon during each day of the spring pollution event. These differences are mainly explained by vertical mixing within the boundary layer, provided that this last one is considered well mixed and therefore homogeneous in ammonia concentrations. This is suggested by ground-based measurements of vertical profiles of aerosol backscatter, used as tracer of the vertical distribution of pollutants in the atmospheric boundary layer. Indeed, the afternoon enhancement of ammonia clearly seen by OASIS for the whole atmospheric column is barely depicted by surface concentrations, as the surface concentrations are strongly affected by vertical dilution within the rising boundary layer. Moreover, the concomitant occurrence of a decrease in ammonium particle concentrations and an increase in gaseous ammonia abundance suggests the volatilization of particles for forming ammonia. Furthermore, surface observations may also suggest nighttime formation of ammonium particles from gas-to-particle conversion, for relative humidity levels higher than the deliquescence point of ammonium nitrate.
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Kache, S., I. Bartl, J. Wäge-Recchioni und M. Voss. „Influence of organic particle addition on nitrification rates and ammonium oxidiser abundances in Baltic seawater“. Marine Ecology Progress Series 674 (16.09.2021): 59–72. http://dx.doi.org/10.3354/meps13797.
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Nitrification is a key microbial process in the nitrogen cycle of the ocean that largely determines the pool sizes of nitrite, nitrate and ammonium but hardly affects the total pool of inorganic nitrogen (except through N2O losses to the atmosphere). This study explored the regulation of nitrification and its dependency on particle and ammonium concentrations. Incubation experiments were conducted in which particles of different origin were added to Baltic seawater, followed by 15NH4+-labelling and droplet digital PCR. Both nitrification rates according to particle size (>3 µm and 0.22-3 µm) and archaeal and betaproteobacterial ammonia monooxygenase α-subunit gene (amoA) abundances were determined in order to assess the impact of high particle concentrations found in coastal areas of the Baltic Sea. The data show that the addition of particulate organic matter enhanced the nitrification rates in bulk (~805 nmol l-1 d-1) but not in the <3 µm fraction (<100 nmol l-1 d-1), indicative of a strong influence of the added particles on nitrification rates. The regulation of nitrification rates by the substrate ammonium was suggested by the inverse correlation between these 2 variables. Measurements of amoA gene abundances showed the dominance of ammonium-oxidising bacteria over ammonium-oxidising archaea during most of the 41 d experiment. Abundances of amoA were highest in the particle-associated fraction of the bacteria (≤6.9 × 106 amoA copies l-1). These findings demonstrate the importance of particle-associated ammonium-oxidising bacteria in the nitrification processes of coastal and estuarine waters containing high particle densities.
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Xu, L., und J. E. Penner. „Global simulations of nitrate and ammonium aerosols and their radiative effects“. Atmospheric Chemistry and Physics Discussions 12, Nr. 4 (19.04.2012): 10115–79. http://dx.doi.org/10.5194/acpd-12-10115-2012.
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Abstract. We examine the formation of nitrate and ammonium on five types of externally mixed pre-existing aerosols using the hybrid dynamic method in a global chemistry transport model. The model developed here predicts a similar spatial pattern of total aerosol nitrate and ammonium to that of several pioneering studies, but separates the effects of nitrate and ammonium on pure sulfate, biomass burning, fossil fuel, dust and sea salt aerosols. Nitrate and ammonium boost the scattering efficiency of sulfate and organic matter but lower the extinction of sea salt particles since the hygroscopicity of a mixed nitrate-ammonium-sea salt particle is less than that of pure sea salt. The direct anthropogenic forcing of particulate nitrate and ammonium at the top of atmosphere (TOA) is estimated to be −0.12 W m−2. Nitrate, ammonium and nitric acid gas also affect aerosol activation and the reflectivity of clouds. The first aerosol indirect forcing by anthropogenic nitrate (gas plus aerosol) and ammonium is estimated to be −0.09 W m−2 at TOA, almost all of which is due to nitric acid gas (−0.08 W m−2).
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Xu, L., und J. E. Penner. „Global simulations of nitrate and ammonium aerosols and their radiative effects“. Atmospheric Chemistry and Physics 12, Nr. 20 (22.10.2012): 9479–504. http://dx.doi.org/10.5194/acp-12-9479-2012.
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Abstract. We examine the formation of nitrate and ammonium on five types of externally mixed pre-existing aerosols using the hybrid dynamic method in a global chemistry transport model. The model developed here predicts a similar spatial pattern of total aerosol nitrate and ammonium to that of several pioneering studies, but separates the effects of nitrate and ammonium on pure sulfate, biomass burning, fossil fuel, dust and sea salt aerosols. Nitrate and ammonium boost the scattering efficiency of sulfate and organic matter but lower the extinction of sea salt particles since the hygroscopicity of a mixed nitrate-ammonium-sea salt particle is less than that of pure sea salt. The direct anthropogenic forcing of particulate nitrate and ammonium at the top of the atmosphere (TOA) is estimated to be −0.12 W m−2. Nitrate, ammonium and nitric acid gas also affect aerosol activation and the reflectivity of clouds. The first aerosol indirect forcing by anthropogenic nitrate (gas plus aerosol) and ammonium is estimated to be −0.09 W m−2 at the TOA, almost all of which is due to condensation of nitric acid gas onto growing droplets (−0.08 W m−2).
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Healy, R. M., N. Riemer, J. C. Wenger, M. Murphy, M. West, L. Poulain, A. Wiedensohler et al. „Single particle diversity and mixing state measurements“. Atmospheric Chemistry and Physics Discussions 14, Nr. 3 (14.02.2014): 3973–4005. http://dx.doi.org/10.5194/acpd-14-3973-2014.
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Abstract. A newly developed framework for quantifying aerosol particle diversity and mixing state based on information-theoretic entropy is applied for the first time to single particle mass spectrometry field data. Single particle mass fraction estimates for black carbon, organic aerosol, ammonium, nitrate and sulphate, derived using single particle mass spectrometer, aerosol mass spectrometer and multi-angle absorption photometer measurements are used to calculate single particle species diversity (Di). The average single particle species diversity (Dα) is then related to the species diversity of the bulk population (Dγ) to derive a mixing state index value (χ) at hourly resolution. The mixing state index is a single parameter representation of how internally/externally mixed a particle population is at a given time. The index describes a continuum, with values of 0% and 100% representing fully external and internal mixing, respectively. This framework was applied to data collected as part of the MEGAPOLI winter campaign in Paris, France 2010. Di values are low (∼2) for fresh traffic and woodburning particles that contain high mass fractions of black carbon and organic aerosol but low mass fractions of inorganic ions. Conversely, Di values are higher (∼4) for aged carbonaceous particles containing similar mass fractions of black carbon, organic aerosol, ammonium, nitrate and sulphate. Aerosol in Paris is estimated to be 59% internally mixed in the size range 150–1067 nm, and mixing state is dependent both upon time of day and air mass origin. Daytime primary emissions associated with vehicular traffic and woodburning result in low χ values, while enhanced condensation of ammonium nitrate on existing particles at night leads to higher χ values. Advection of particles from continental Europe containing ammonium, nitrate and sulphate leads to increases in Dα, Dγ and χ. The mixing state index represents a useful metric by which to compare and contrast ambient particle mixing state at other locations globally.
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Kodikara, Jayanga, Buddhika Gunawardana, Mahesh Jayaweera, Madhusha Sudasinghe und Jagath Manatunge. „Nitrate removal in potable groundwater by nano zerovalent iron under oxic conditions“. Water Practice and Technology 15, Nr. 4 (10.09.2020): 1126–43. http://dx.doi.org/10.2166/wpt.2020.086.
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Abstract Groundwater pollution by nitrate contamination has become a significant issue in some areas of Sri Lanka, giving rise to health concerns and a dearth in good quality potable water. In this study, the effectiveness of nano zerovalent iron (nZVI) for the removal of nitrate in potable groundwater under oxic conditions was investigated to meet the drinking water quality standards stipulated by World Health Organization (WHO) and Sri Lanka Standards Institution (SLSI) (nitrate level <50 mg/L). Under oxic conditions, the nZVI was synthesized and batch experiments were conducted using an artificial nitrate (150 mg/L) contaminated water sample. Our results corroborated that with an optimum nZVI dose of 1 g/L and optimum contact time of 30 minutes, 80% nitrate removal could be achieved and the remaining nitrate level was ≈ 30 mg/L as nitrate (<50 mg/L), which was equivalent to ≈ 7 mg/L as nitrate–N (≈21% of the total–N). Ammonium ions were the main product of nitrate reduction by nZVI and at 30 minutes contact time, ≈ 20 mg/L of ammonium as ammonium–N was detected (≈ 59% of the total–N). Ammonia stripping took place under the basic solution pH (pH > 9.5). At 30 minutes of contact time, ≈7 mg/L of ammonia as ammonia–N was accounted for ammonia stripping, which is 20% of the total–N. Ammonia stripping resulted in a decrease in nitrogen-containing species in the aqueous phase. The spent nZVI particles were recovered (99.9%) from the treated water using an external magnetic field. In conclusion, nZVI particles synthesized under oxic conditions are viable to successfully treat the nitrate-contaminated groundwater under aerobic conditions to reduce the nitrate levels to meet the WHO/SLSI drinking water quality standards.
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Myhre, G., A. Grini und S. Metzger. „Modelling of nitrate and ammonium-containing aerosols in presence of sea salt“. Atmospheric Chemistry and Physics 6, Nr. 12 (25.10.2006): 4809–21. http://dx.doi.org/10.5194/acp-6-4809-2006.
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Abstract. A thermodynamical model for treatment of gas/aerosol partitioning of semi volatile inorganic aerosols has been implemented in a global chemistry and aerosol transport model (Oslo CTM2). The sulphur cycle and sea salt particles have been implemented earlier in the Oslo CTM2 and the focus of this study is on nitrate partitioning to the aerosol phase and if particulate nitrate is expected to form in fine or coarse mode aerosols. Modelling of the formation of fine mode nitrate particles is complicated since it depends on other aerosol components and aerosol precursors as well as meteorological condition. The surface concentrations from the model are compared to observed surface concentrations at around 20 sites around Europe for nitrate and ammonium. The agreement for nitrate is good but the modelled values are somewhat underestimated compared to observations at high concentrations, whereas for ammonium the agreement is very good. However, we underscore that such a comparison is not of large importance for the aerosol optical depth of particulate nitrate since the vertical profile of aerosol components and their precursors are so important. Fine mode nitrate formation depends on vertical profiles of both ammonia/ammonium and sulphate. The model results show that fine mode particulate nitrate play a non-negligible role in the total aerosol composition in certain industrialized regions and therefore have a significant local radiative forcing. On a global scale the aerosol optical depth of fine mode nitrate is relatively small due to limited availability of ammonia and loss to larger sea salt particles. Inclusion of sea salt in the calculations reduces the aerosol optical depth and burden of fine mode nitrate by 25% on a global scale but with large regional variations.
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Ahlberg, Erik, Axel Eriksson, William H. Brune, Pontus Roldin und Birgitta Svenningsson. „Effect of salt seed particle surface area, composition and phase on secondary organic aerosol mass yields in oxidation flow reactors“. Atmospheric Chemistry and Physics 19, Nr. 4 (01.03.2019): 2701–12. http://dx.doi.org/10.5194/acp-19-2701-2019.
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Abstract. Atmospheric particulate water is ubiquitous, affecting particle transport and uptake of gases. Yet, research on the effect of water on secondary organic aerosol (SOA) mass yields is not consistent. In this study, the SOA mass yields of an α-pinene and m-xylene mixture, at a concentration of 60 µg m−3, were examined using an oxidation flow reactor operated at a relative humidity (RH) of 60 % and a residence time of 160 s. Wet or dried ammonium sulfate and ammonium nitrate seed particles were used. By varying the amount of seed particle surface area, the underestimation of SOA formation induced by the short residence time in flow reactors was confirmed. Starting at a SOA mass concentration of ∼5 µg m−3, the maximum yield increased by a factor of ∼2 with dry seed particles and on average a factor of 3.2 with wet seed particles. Hence, wet particles increased the SOA mass yield by ∼60 % compared to the dry experiment. Maximum yield in the reactor was achieved using a surface area concentration of ∼1600 µm2 cm−3. This corresponded to a condensational lifetime of 20 s for low-volatility organics. The O:C ratio of SOA on wet ammonium sulfate was significantly higher than when using ammonium nitrate or dry ammonium sulfate seed particles, probably due to differences in heterogeneous chemistry.
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Healy, R. M., N. Riemer, J. C. Wenger, M. Murphy, M. West, L. Poulain, A. Wiedensohler et al. „Single particle diversity and mixing state measurements“. Atmospheric Chemistry and Physics 14, Nr. 12 (25.06.2014): 6289–99. http://dx.doi.org/10.5194/acp-14-6289-2014.
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Abstract. A newly developed framework for quantifying aerosol particle diversity and mixing state based on information-theoretic entropy is applied for the first time to single particle mass spectrometry field data. Single particle mass fraction estimates for black carbon, organic aerosol, ammonium, nitrate and sulfate, derived using single particle mass spectrometer, aerosol mass spectrometer and multi-angle absorption photometer measurements are used to calculate single particle species diversity (Di). The average single particle species diversity (Dα) is then related to the species diversity of the bulk population (Dγ) to derive a mixing state index value (χ) at hourly resolution. The mixing state index is a single parameter representation of how internally/externally mixed a particle population is at a given time. The index describes a continuum, with values of 0 and 100% representing fully external and internal mixing, respectively. This framework was applied to data collected as part of the MEGAPOLI winter campaign in Paris, France, 2010. Di values are low (~ 2) for fresh traffic and wood-burning particles that contain high mass fractions of black carbon and organic aerosol but low mass fractions of inorganic ions. Conversely, Di values are higher (~ 4) for aged carbonaceous particles containing similar mass fractions of black carbon, organic aerosol, ammonium, nitrate and sulfate. Aerosol in Paris is estimated to be 59% internally mixed in the size range 150–1067 nm, and mixing state is dependent both upon time of day and air mass origin. Daytime primary emissions associated with vehicular traffic and wood-burning result in low χ values, while enhanced condensation of ammonium nitrate on existing particles at night leads to higher χ values. Advection of particles from continental Europe containing ammonium, nitrate and sulfate leads to increases in Dα, Dγ and χ. The mixing state index represents a useful metric by which to compare and contrast ambient particle mixing state at other locations globally.
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Mihai, Oana, Stefanie Tamm, Marie Stenfeldt und Louise Olsson. „The effect of soot on ammonium nitrate species and NO 2 selective catalytic reduction over Cu–zeolite catalyst-coated particulate filter“. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 374, Nr. 2061 (28.02.2016): 20150086. http://dx.doi.org/10.1098/rsta.2015.0086.
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A selective catalytic reduction (SCR)-coated particulate filter was evaluated by means of dynamic tests performed using NH 3 , NO 2 , O 2 and H 2 O. The reactions were examined both prior to and after soot removal in order to study the effect of soot on ammonium nitrate formation and decomposition, ammonia storage and NO 2 SCR. A slightly larger ammonia storage capacity was observed when soot was present in the sample, which indicated that small amounts of ammonia can adsorb on the soot. Feeding of NO 2 and NH 3 in the presence of O 2 and H 2 O at low temperature (150, 175 and 200°C) leads to a large formation of ammonium nitrate species and during the subsequent temperature ramp using H 2 O and argon, a production of nitrous oxides was observed. The N 2 O formation is often related to ammonium nitrate decomposition, and our results showed that the N 2 O formation was clearly decreased by the presence of soot. We therefore propose that in the presence of soot, there are fewer ammonium nitrate species on the surface due to the interactions with the soot. Indeed, we do observe CO 2 production during the reaction conditions also at 150°C, which shows that there is a reaction with these species and soot. In addition, the conversion of NO x due to NO 2 SCR was significantly enhanced in the presence of soot; we attribute this to the smaller amount of ammonium nitrate species present in the experiments where soot is available since it is well known that ammonium nitrate formation is a major problem at low temperature due to the blocking of the catalytic sites. Further, a scanning electron microscopy analysis of the soot particles shows that they are about 30–40 nm and are therefore too large to enter the pores of the zeolites. There are likely Cu x O y or other copper species available on the outside of the zeolite crystallites, which could have been enhanced due to the hydrothermal treatment at 850°C of the SCR-coated filter prior to the soot loading. We therefore propose that soot is interacting with the ammonium nitrate species on the Cu x O y or other copper species on the surface of the zeolite particles, which reduces the ammonium nitrate blocking of the catalyst and thereby results in higher NO 2 SCR activity.
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Wu, Li, Xue Li, HyeKyeong Kim, Hong Geng, Ricardo H. M. Godoi, Cybelli G. G. Barbosa, Ana F. L. Godoi et al. „Single-particle characterization of aerosols collected at a remote site in the Amazonian rainforest and an urban site in Manaus, Brazil“. Atmospheric Chemistry and Physics 19, Nr. 2 (31.01.2019): 1221–40. http://dx.doi.org/10.5194/acp-19-1221-2019.
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Abstract. In this study, aerosol samples collected at a remote site in the Amazonian rainforest and an urban site in Manaus, Brazil, were investigated on a single-particle basis using a quantitative energy-dispersive electron probe X-ray microanalysis (ED-EPMA). A total of 23 aerosol samples were collected in four size ranges (0.25–0.5, 0.5–1.0, 1.0–2.0, and 2.0–4.0 µm) during the wet season in 2012 at two Amazon basin sites: 10 samples in Manaus, an urban area; and 13 samples at an 80 m high tower, located at the Amazon Tall Tower Observatory (ATTO) site in the middle of the rainforest, 150 km northeast of Manaus. The aerosol particles were classified into nine particle types based on the morphology on the secondary electron images (SEIs) together with the elemental concentrations of 3162 individual particles: (i) secondary organic aerosols (SOA); (ii) ammonium sulfate (AS); (iii) SOA and AS mixtures; (iv) aged mineral dust; (v) reacted sea salts; (vi) primary biological aerosol (PBA); (vii) carbon-rich or elemental carbon (EC) particles, such as soot, tarball, and char; (viii) fly ash; and (ix) heavy metal (HM, such as Fe, Zn, Ni, and Ti)-containing particles. In submicron aerosols collected at the ATTO site, SOA and AS mixture particles were predominant (50 %–94 % in relative abundance) with SOA and ammonium sulfate comprising 73 %–100 %. In supermicron aerosols at the ATTO site, aged mineral dust and sea salts (37 %–70 %) as well as SOA and ammonium sulfate (28 %–58 %) were abundant. PBAs were observed abundantly in the PM2−4 fraction (46 %), and EC and fly ash particles were absent in all size fractions. The analysis of a bulk PM0.25−0.5 aerosol sample from the ATTO site using Raman microspectrometry and attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) showed that ammonium sulfate, organics, and minerals are the major chemical species, which is consistent with the ED-EPMA results. In the submicron aerosols collected in Manaus, either SOA and ammonium sulfate (17 %–80 %) or EC particles (6 %–78 %) were dominant depending on the samples. In contrast, aged mineral dust, reacted sea salt, PBA, SOA, ammonium sulfate, and EC particles comprised most of the supermicron aerosols collected in Manaus. The SOA, ammonium sulfate, and PBAs were mostly of a biogenic origin from the rainforest, whereas the EC and HM-containing particles were of an anthropogenic origin. Based on the different contents of SOA, ammonium sulfate, and EC particles among the samples collected in Manaus, a considerable influence of the rainforest over the city was observed. Aged mineral dust and reacted sea-salt particles, including mineral dust mixed with sea salts probably during long-range transatlantic transport, were abundant in the supermicron fractions at both sites. Among the aged mineral dust and reacted sea-salt particles, sulfate-containing ones outnumbered those containing nitrates and sulfate + nitrate in the ATTO samples. In contrast, particles containing sulfate + nitrate were comparable in number to particles containing sulfate only in the Manaus samples, indicating the different sources and formation mechanisms of secondary aerosols, i.e., the predominant presence of sulfate at the ATTO site from mostly biogenic emissions and the elevated influences of nitrates from anthropogenic activities at the Manaus site.
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Xu, Xiao Juan, Xu Dong Sun, Ji Guang Li, Xiao Dong Li, Di Huo und Shao Hong Liu. „Synthesis of Ultrafine Spherical Yttrium Aluminum Garnet Powders from Yttrium Nitrate and Aluminum Nitrate System“. Applied Mechanics and Materials 377 (August 2013): 151–55. http://dx.doi.org/10.4028/www.scientific.net/amm.377.151.
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Ultrafine spherical yttrium aluminum garnet (YAG) powders have been synthesized via homogeneous precipitation method using urea as the precipitant. The precursor powders were calcinated at 1000°C or 1100°C for 4 hrs and then were studied by means of FE-SEM, XRD, FT-IR and TG-DTA. The result shows that the amount of ammonium sulfate has a significant effect on morphology and particle size of powders. Pure phase and spherical YAG particles with 350 nm in diameter can be obtained when the molar ratio of ammonium sulfate to aluminum nitrate is about 0.75 and the concentration of the metallic ions is 0.008M.
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Uekawa, Naofumi, Takashi Kojima und Kazuyuki Kakegawa. „Synthesis of nitrogen-doped ZnO particles by decomposition of zinc nitrate hexahydrate in molten ammonium salts“. Journal of Materials Research 24, Nr. 11 (November 2009): 3343–49. http://dx.doi.org/10.1557/jmr.2009.0399.
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The N-doped ZnO was prepared by heating a mixture of zinc nitrate hexahydrate [Zn(NO3)2·6 H2O] and ammonium salt at 623 K for 1 h in air. The mixture of zinc nitrate hydrate and ammonium salt formed a homogeneous molten salt at 623 K, and the homogeneous dispersion of the metal ions and ammonium ions contributed to the N-doping. In particular, when the mixture of zinc nitrate hydrate and ammonium acetate (CH3COONH4) was heated at 623 K, the doped amount of nitrogen was higher than with the mixture of zinc nitrate hydrate and NH4NO4. The acetate anion (CH3COO−) restricted the oxidation reaction of nitrate anion (NO3−). Furthermore, Al- and N-co-doped ZnO particles were obtained by heating the mixture of zinc nitrate hydrate, aluminum nitrate hydrate, and ammonium acetate. The Al and N co-doping effectively increased the doped amount of nitrogen. The spontaneous formation of ZnO lattice and the nitrogen source in the molten salt and the homogeneous dispersion of Zn2+ ions and Al3+ ions contributed to the increase in the amount of doped nitrogen.
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Romakkaniemi, S., A. Jaatinen, A. Laaksonen, A. Nenes und T. Raatikainen. „Ammonium nitrate evaporation and nitric acid condensation in DMT CCN counters“. Atmospheric Measurement Techniques 7, Nr. 5 (20.05.2014): 1377–84. http://dx.doi.org/10.5194/amt-7-1377-2014.
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Abstract. The effect of inorganic semivolatile aerosol compounds on the cloud condensation nucleus (CCN) activity of aerosol particles was studied by using a computational model for a DMT-CCN counter, a cloud parcel model for condensation kinetics and experiments to quantify the modelled results. Concentrations of water vapour and semivolatiles as well as aerosol trajectories in the CCN column were calculated by a computational fluid dynamics model. These trajectories and vapour concentrations were then used as an input for the cloud parcel model to simulate mass transfer kinetics of water and semivolatiles between aerosol particles and the gas phase. Two different questions were studied: (1) how big a fraction of semivolatiles is evaporated from particles after entering but before particle activation in the DMT-CCN counter? (2) How much can the CCN activity be increased due to condensation of semivolatiles prior to the maximum water supersaturation in the case of high semivolatile concentration in the gas phase? Both experimental and modelling results show that the evaporation of ammonia and nitric acid from ammonium nitrate particles causes a 10 to 15 nm decrease to the critical particle size in supersaturations between 0.1% and 0.7%. On the other hand, the modelling results also show that condensation of nitric acid or similar vapour can increase the CCN activity of nonvolatile aerosol particles, but a very high gas phase concentration (as compared to typical ambient conditions) would be needed. Overall, it is more likely that the CCN activity of semivolatile aerosol is underestimated than overestimated in the measurements conducted in ambient conditions.
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Pollema, Cy H., Emil B. Milosavljević, James L. Hendrix, Ljiljana Solujić und John H. Nelson. „Photocatalytic oxidation of aqueous ammonia (ammonium ion) to nitrite or nitrate at TiO2 particles“. Monatshefte für Chemie Chemical Monthly 123, Nr. 4 (April 1992): 333–39. http://dx.doi.org/10.1007/bf00810945.
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Jeong, C. H., M. L. McGuire, K. J. Godri, J. G. Slowik, P. J. G. Rehbein und G. J. Evans. „Quantification of aerosol chemical composition using continuous single particle measurements“. Atmospheric Chemistry and Physics 11, Nr. 14 (20.07.2011): 7027–44. http://dx.doi.org/10.5194/acp-11-7027-2011.
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Abstract. Mass concentrations of sulphate, nitrate, ammonium, organic carbon (OC), elemental carbon (EC) were determined from real time single particle data in the size range 0.1–3.0 μm measured by an Aerosol Time-of-Flight Mass Spectrometer (ATOFMS) at urban and rural sites in Canada. To quantify chemical species within individual particles measured by an ATOFMS, ion peak intensity of m/z −97 for sulphate, −62 for nitrate, +18 for ammonium, +43 for OC, and +36 for EC were scaled using the number and size distribution data by an Aerodynamic Particle Sizer (APS) and a Fast Mobility Particle Sizer (FMPS). Hourly quantified chemical species from ATOFMS single-particle analysis were compared with collocated fine particulate matter (aerodynamic diameter < 2.5 μm, PM2.5) chemical composition measurements by an Aerosol Mass Spectrometer (AMS) at a rural site, a Gas-Particle Ion Chromatograph (GPIC) at an urban site, and a Sunset Lab field OCEC analyzer at both sites. The highest correlation was found for nitrate, with correlation coefficients (Pearson r) of 0.89 (ATOFMS vs. GPIC) and 0.85 (ATOFMS vs. AMS). ATOFMS mass calibration factors, determined for the urban site, were used to calculate mass concentrations of the major PM2.5 chemical components at the rural site near the US border in southern Ontario. Mass reconstruction using the ATOFMS mass calibration factors agreed very well with the PM2.5 mass concentrations measured by a Tapered Element Oscillating Microbalance (TEOM, r = 0.86) at the urban site and a light scattering monitor (DustTrak, r = 0.87) at the rural site. In the urban area nitrate was the largest contributor to PM2.5 mass in the winter, while organics and sulphate contributed ~64 % of the summer PM2.5 in the rural area, suggesting a strong influence of regional/trans-boundary pollution. The mass concentrations of five major species in ten size-resolved particle-types and aerosol acidity of each particle-type were determined for the rural site. On a mass basis sulphate and OC rich particle-types (OC-S and OC-S-N) accounted for up to 59 % of the particles characterized and aerosols were weakly acidic in the rural area. This is the first study to estimate hourly quantitative data of sulphate, nitrate, ammonium, OC and EC in ambient particles from scaled ATOFMS single particle analysis; these were closely comparable with collocated high time resolution data of sulphate, nitrate and ammonium detected by AMS and GPIC.
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Martin, S. T., H. M. Hung, R. J. Park, D. J. Jacob, R. J. D. Spurr, K. V. Chance und V. Chin. „Effects of the physical state of tropospheric ammonium-sulfate-nitrate particles on global aerosol direct radiative forcing“. Atmospheric Chemistry and Physics Discussions 3, Nr. 5 (29.10.2003): 5399–467. http://dx.doi.org/10.5194/acpd-3-5399-2003.
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Abstract. The effect of aqueous versus crystalline sulfate-nitrate-ammonium tropospheric particles on global aerosol direct radiative forcing is assessed. A global three-dimensional chemical transport model predicts sulfate, nitrate, and ammonium aerosol mass. An aerosol thermodynamics model is called twice, once for the upper side (US) and once for lower side (LS) of the hysteresis loop of particle phase. On the LS, the sulfate mass budget is 40% solid ammonium sulfate, 12% letovicite, 11% ammonium bisulfate, and 37% aqueous. The LS nitrate mass budget is 26% solid ammonium nitrate, 7% aqueous, and 67% gas-phase nitric acid release due to increased volatility upon crystallization. The LS ammonium budget is 45% solid ammonium sulfate, 10% letovicite, 6% ammonium bisulfate, 4% ammonium nitrate, 7% ammonia release due to increased volatility, and 28% aqueous. LS aerosol water mass partitions as 22% effloresced to the gas-phase and 78% remaining as aerosol mass. The predicted US/LS global fields of aerosol mass are employed in a Mie scattering model to generate global US/LS aerosol optical properties, including scattering efficiency, single scattering albedo, and asymmetry parameter. Global annual average LS optical depth and mass scattering efficiency are, respectively, 0.023 and 10.7 m2 (g SO42−)−1, which compare to US values of 0.030 and 13.9 m2 (g SO42−)−1. Radiative transport is computed, first for a base case having no aerosol and then for the two global fields corresponding to the US and LS of the hysteresis loop. Regional, global, seasonal, and annual averages of top-of-the-atmosphere aerosol radiative forcing on the LS and US (FL and FU, respectively, in W m2−) are calculated. Including both anthropogenic and natural emissions, we obtain global annual averages of FL = −0.750, FU = −0.930, and ΔFU,L = 24% for full sky calculations without clouds and FL = −0.485, FU = −0.605, and ΔFU,L = 25% when clouds are included. Regionally, ΔFU,L = 48% over the USA, 55% over Europe, and 34% over East Asia. Seasonally, ΔFU,L varies from 18% in DJF to 75% in SON over the USA. The global annual average contribution from anthropogenic aerosol is FL = −0.314 and FU = −0.404, which yield normalized direct radiative forcings (G) of GL = −205 W (g SO42−)−1 and GU = −264 W (g SO42−)−1.
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Martin, S. T., H. M. Hung, R. J. Park, D. J. Jacob, R. J. D. Spurr, K. V. Chance und M. Chin. „Effects of the physical state of tropospheric ammonium-sulfate-nitrate particles on global aerosol direct radiative forcing“. Atmospheric Chemistry and Physics 4, Nr. 1 (04.02.2004): 183–214. http://dx.doi.org/10.5194/acp-4-183-2004.
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Abstract. The effect of aqueous versus crystalline sulfate-nitrate-ammonium tropospheric particles on global aerosol direct radiative forcing is assessed. A global three-dimensional chemical transport model predicts sulfate, nitrate, and ammonium aerosol mass. An aerosol thermodynamics model is called twice, once for the upper side (US) and once for lower side (LS) of the hysteresis loop of particle phase. On the LS, the sulfate mass budget is 40% solid ammonium sulfate, 12% letovicite, 11% ammonium bisulfate, and 37% aqueous. The LS nitrate mass budget is 26% solid ammonium nitrate, 7% aqueous, and 67% gas-phase nitric acid release due to increased volatility upon crystallization. The LS ammonium budget is 45% solid ammonium sulfate, 10% letovicite, 6% ammonium bisulfate, 4% ammonium nitrate, 7% ammonia release due to increased volatility, and 28% aqueous. LS aerosol water mass partitions as 22% effloresced to the gas-phase and 78% remaining as aerosol mass. The predicted US/LS global fields of aerosol mass are employed in a Mie scattering model to generate global US/LS aerosol optical properties, including scattering efficiency, single scattering albedo, and asymmetry parameter. Global annual average LS optical depth and mass scattering efficiency are, respectively, 0.023 and 10.7 m2 (g SO4-2)-1, which compare to US values of 0.030 and 13.9 m2 (g SO4-2)-1. Radiative transport is computed, first for a base case having no aerosol and then for the two global fields corresponding to the US and LS of the hysteresis loop. Regional, global, seasonal, and annual averages of top-of-the-atmosphere aerosol radiative forcing on the LS and US (FL and FU, respectively, in W m-2) are calculated. Including both anthropogenic and natural emissions, we obtain global annual averages of FL=-0.750, FU=-0.930, and DFU,L=24% for full sky calculations without clouds and FL=-0.485, FU=-0.605, and DFU,L=25% when clouds are included. Regionally, DFU,L=48% over the USA, 55% over Europe, and 34% over East Asia. Seasonally, DFU,L varies from 18% in DJF to 75% in SON over the USA. The global annual average contribution from anthropogenic aerosol is FL=-0.314 and FU=-0.404, which yield normalized direct radiative forcings (G) of GL=-205 W (g SO4-2)-1 and GU=-264 W (g SO4-2)-1.
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Liang, Zhancong, Zhihao Cheng, Ruifeng Zhang, Yiming Qin und Chak K. Chan. „Distinct photochemistry in glycine particles mixed with different atmospheric nitrate salts“. Atmospheric Chemistry and Physics 23, Nr. 16 (29.08.2023): 9585–95. http://dx.doi.org/10.5194/acp-23-9585-2023.
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Abstract. Particulate free amino acids (FAAs) are essential components of organonitrogen that have critical climate impacts, and they are usually considered stable end-products from protein degradation. In this work, we investigated the decay of glycine (GC) as a model FAA under the photolysis of different particulate nitrate salts using an in situ Micro-Raman system. Upon cycling the relative humidity (RH) between 3 % and 80 % RH, ammonium nitrate (AN) and GC mixed particles did not exhibit any phase change, whereas sodium nitrate (SN) and GC mixed particles crystallized at 60 % and deliquesced at 82 % RH. Under light illumination at 80 % RH, AN + GC particles showed almost no spectral changes, while rapid decays of glycine and nitrate were observed in SN + GC particles. The interactions between nitrate and glycine in AN + GC particles suppressed crystallization but also hindered nitrate photolysis and glycine decay. On the other hand, glycine may form a complex with Na+ in deliquescent SN + GC particles and allow unbonded nitrate to undergo photolysis and trigger glycine decay, though nitrate photolysis was greatly hindered upon particle crystallization. Our work provides insights into how FAAs may interact with different nitrate salts under irradiation and lead to distinct decay rates, which facilitates their atmospheric lifetime estimation.
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Wang, Y. H., Z. R. Liu, J. K. Zhang, B. Hu, D. S. Ji, Y. C. Yu und Y. S. Wang. „Aerosol physicochemical properties and implications for visibility during an intense haze episode during winter in Beijing“. Atmospheric Chemistry and Physics 15, Nr. 6 (23.03.2015): 3205–15. http://dx.doi.org/10.5194/acp-15-3205-2015.
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Abstract. The evolution of physical, chemical and optical properties of urban aerosol particles was characterized during an extreme haze episode in Beijing, PRC, from 24 through 31 January 2013 based on in situ measurements. The average mass concentrations of PM1, PM2.5 and PM10 were 99 ± 67 μg m−3 (average ± SD), 188 ± 128 μg m−3 and 265 ± 157 μg m−3, respectively. A significant increase in PM1-2.5 fraction was observed during the most heavily polluted period. The average scattering coefficient at 550 nm was 877 ± 624 Mm−1. An increasing relative amount of coarse particles can be deduced from the variations of backscattering ratios, asymmetry parameter and scattering Ångström exponent. Particle number-size distributions between 14 and 2500 nm diameter showed high number concentrations, particularly in the nucleation mode and accumulation mode. Size-resolved chemical composition of submicron aerosol from a high-resolution time-of-flight aerosol mass spectrometer showed that the mass concentrations of organic, sulfate, nitrate, ammonium and chlorine mainly resided on particles between 500 and 800 nm (vacuum diameter), and nitrate and ammonium contributed greatly to particle growth during the heavily polluted day (28 January). Increasing relative humidity and stable synoptic conditions on 28 January combined with heavy pollution on 28 January, leading to enhanced water uptake by the hygroscopic submicron particles and formation of secondary aerosol, which might be the main reasons for the severity of the haze episode. Light-scattering apportionment showed that organic, sulfate, ammonium nitrate and ammonium chloride compounds contributed to light-scattering fractions of 54, 24, 12 and 10%, respectively. This study indicated that the organic component in submicron aerosol played an important role in visibility degradation during the haze episode in Beijing.
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Wu, Li, Xue Li und Chul-Un Ro. „Hygroscopic Behavior of Ammonium Sulfate, Ammonium Nitrate, and their Mixture Particles“. Asian Journal of Atmospheric Environment 13, Nr. 3 (30.09.2019): 196–211. http://dx.doi.org/10.5572/ajae.2019.13.3.196.
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ERMAKOV, A. N., A. E. ALOYAN und V. O. ARUTYUNYAN. „ACIDITY OF AEROSOL PARTICLES IN THE RURAL ATMOSPHERE“. Meteorologiya i Gidrologiya, Nr. 11 (November 2021): 56–63. http://dx.doi.org/10.52002/0130-2906-2021-11-56-63.
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Estimates for the acidity of aerosol particles in the rural atmosphere over Wingene (Belgium) are presented. The results of processing monitoring data using data of the control of meteorological conditions, gas impurities, ion composition, and mass concentration of aerosol particles, as well as the use of thermodynamic methods showed that the level of acidity of aerosol particles in the atmosphere is unexpectedly high (pH ≈ 3.5-4.3) despite their sampling in the background area. It is found that the variability of particle acidity is mainly determined by fluctuations in relative humidity and the content of gas-phase ammonia in the air. In this case, the lower the relative humidity is, the higher the acidity of particles is, which reflects the variability of moisture content in particles and the solubility of ammonium nitrate.
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Schlenker, Julie C., und Scot T. Martin. „Crystallization Pathways of Sulfate−Nitrate−Ammonium Aerosol Particles“. Journal of Physical Chemistry A 109, Nr. 44 (November 2005): 9980–85. http://dx.doi.org/10.1021/jp052973x.
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Lloyd, Julie A., Katherine J. Heaton und Murray V. Johnston. „Reactive Uptake of Trimethylamine into Ammonium Nitrate Particles“. Journal of Physical Chemistry A 113, Nr. 17 (30.04.2009): 4840–43. http://dx.doi.org/10.1021/jp900634d.
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Maggi, Filippo, und Priya Garg. „Fragmentation of Ammonium Nitrate Particles under Thermal Cycling“. Propellants, Explosives, Pyrotechnics 43, Nr. 3 (30.01.2018): 315–19. http://dx.doi.org/10.1002/prep.201700230.
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Liu, X. H., Y. J. Zhu, M. Zheng, H. W. Gao und X. H. Yao. „Production and growth of new particles during two cruise campaigns in the marginal seas of China“. Atmospheric Chemistry and Physics Discussions 14, Nr. 2 (28.01.2014): 3043–69. http://dx.doi.org/10.5194/acpd-14-3043-2014.
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Abstract. In this paper, we investigated production and growth of new particles in the marine atmosphere during two cruise campaigns in China Seas using a Fast Mobility Particle Sizer. Only eight new particle formation (NPF) events (> 30 min) occurred on 5 days out of 31 sampling days and the subsequent growth of new particles were observed only in five events. Apparent formation rates of new particles (in the range of 5.6–30 nm) varied from 0.3 to 15.2 particles cm−3 s−1 in eight events and growth rates ranged from 2.5 to 10 nm h−1 in five NPF events. Modeling results simulated by US EPA Community Multi-scale Air Quality Model (CMAQ) showed that ammonium nitrate (NH4NO3) was newly formed in the atmosphere over the corresponding sea zone during 2 out of 5 events, in which new particles partially or mostly grew over 50 nm. However, in the remaining three events, new particles cannot grow over 30 nm and the modeling results showed that no NH4NO3 was newly formed in the corresponding marine atmosphere. Modeling results also showed that formation of secondary organics occurred through all new particle growth periods. Difference between the two types of new particle growth patterns suggested that a combination of ammonium nitrate and organics newly formed likely contributed to the growth of new particles from 30 nm to larger size. The findings were obtained from the limited data and still required more future study for confirmation.
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Dall'Osto, M., R. M. Harrison, H. Coe, P. I. Williams und J. D. Allan. „Real time chemical characterization of local and regional nitrate aerosols“. Atmospheric Chemistry and Physics Discussions 8, Nr. 6 (17.11.2008): 19457–86. http://dx.doi.org/10.5194/acpd-8-19457-2008.
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Abstract. Nitrate aerosols make a very major contribution to PM2.5 and PM10 in western Europe, but their sources and pathways have not been fully elucidated. An Aerosol Time-Of-Flight Mass Spectrometer (ATOFMS) and a Compact Time of Flight Aerosol Mass Spectrometer (C-ToF-AMS) were deployed in an urban background location in London, UK, collecting data as part of the REPARTEE-I experiment. During REPARTEE-I, daily PM10 concentrations ranged up to 43.6 µg m−3, with hourly nitrate concentrations (measured by AMS) of up to 5.3 µg m−3. The application of the ART-2a neural network algorithm to the ATOFMS data characterised the nitrate particles as occurring in two distinct clusters (i.e. particle types). The first (33.6% of particles by number) appeared to be locally produced in urban locations during nighttime, whilst the second (22.8% of particles by number) was regionally transported from continental Europe. Nitrate in locally produced aerosol was present mainly in particles smaller than 300 nm, whilst the regional nitrate presented a coarser mode, peaking at 600 nm. In both aerosol types, nitrate was found to be internally mixed with sulphate, ammonium, elemental and organic carbon. Nitrate in regional aerosol appeared to be more volatile than that locally formed. During daytime, a core of the regionally transported nitrate aerosol particle type composed of organic carbon and sulphate was detected.
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Dall'Osto, M., R. M. Harrison, H. Coe, P. I. Williams und J. D. Allan. „Real time chemical characterization of local and regional nitrate aerosols“. Atmospheric Chemistry and Physics 9, Nr. 11 (09.06.2009): 3709–20. http://dx.doi.org/10.5194/acp-9-3709-2009.
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Abstract. Nitrate aerosols make a very major contribution to PM2.5 and PM10 in western Europe, but their sources and pathways have not been fully elucidated. An Aerosol Time-of-Flight Mass Spectrometer (ATOFMS) and a Compact Time of Flight Aerosol Mass Spectrometer (C-ToF-AMS) were deployed in an urban background location in London, UK, collecting data as part of the REPARTEE-I experiment. During REPARTEE-I, daily PM10 concentrations ranged up to 43.6 μg m−3, with hourly nitrate concentrations (measured by AMS) of up to 5.3 μg m−3. The application of the ART-2a neural network algorithm to the ATOFMS data characterised the nitrate particles as occurring in two distinct clusters (i.e. particle types). The first (33.6% of particles by number) appeared to be locally produced in urban locations during nighttime, whilst the second (22.8% of particles by number) was regionally transported from continental Europe. Nitrate in locally produced aerosol was present mainly in particles smaller than 300 nm, whilst the regional nitrate presented a coarser mode, peaking at 600 nm. In both aerosol types, nitrate was found to be internally mixed with sulphate, ammonium, elemental and organic carbon. Nitrate in regional aerosol appeared to be more volatile than that locally formed. During daytime, a core of the regionally transported nitrate aerosol particle type composed of organic carbon and sulphate was detected.
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Denisova, E. I., Irina A. Ustyuzhaninova, Vadim V. Kartashov, Vladimir A. Volkovich, Ivan V. Chernetskiy und Alexander V. Vlasov. „Glycine-Nitrate Combustion Synthesis of ZrO2-Y2O3 Nanopowders“. Advanced Materials Research 1103 (Mai 2015): 37–43. http://dx.doi.org/10.4028/www.scientific.net/amr.1103.37.
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Formation of ZrO2-5 wt.% Y2O3 nanostructured powders in glycine-nitrate combustion synthesis was investigated and the effect of "glycine-to-NO3-" ratio and heating method on the reaction product composition and particle morphology studied. Urea and ammonium nitrate additives were used to optimize the regime of the process. The effect of these reagents on gas generation required for the dispersion of particles, and on the process temperature was investigated.
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Stockwell, Chelsea E., Agnieszka Kupc, Bartłomiej Witkowski, Ranajit K. Talukdar, Yong Liu, Vanessa Selimovic, Kyle J. Zarzana et al. „Characterization of a catalyst-based conversion technique to measure total particulate nitrogen and organic carbon and comparison to a particle mass measurement instrument“. Atmospheric Measurement Techniques 11, Nr. 5 (14.05.2018): 2749–68. http://dx.doi.org/10.5194/amt-11-2749-2018.
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Abstract. The chemical composition of aerosol particles is a key aspect in determining their impact on the environment. For example, nitrogen-containing particles impact atmospheric chemistry, air quality, and ecological N deposition. Instruments that measure total reactive nitrogen (Nr = all nitrogen compounds except for N2 and N2O) focus on gas-phase nitrogen and very few studies directly discuss the instrument capacity to measure the mass of Nr-containing particles. Here, we investigate the mass quantification of particle-bound nitrogen using a custom Nr system that involves total conversion to nitric oxide (NO) across platinum and molybdenum catalysts followed by NO−O3 chemiluminescence detection. We evaluate the particle conversion of the Nr instrument by comparing to mass-derived concentrations of size-selected and counted ammonium sulfate ((NH4)2SO4), ammonium nitrate (NH4NO3), ammonium chloride (NH4Cl), sodium nitrate (NaNO3), and ammonium oxalate ((NH4)2C2O4) particles determined using instruments that measure particle number and size. These measurements demonstrate Nr-particle conversion across the Nr catalysts that is independent of particle size with 98 ± 10 % efficiency for 100–600 nm particle diameters. We also show efficient conversion of particle-phase organic carbon species to CO2 across the instrument's platinum catalyst followed by a nondispersive infrared (NDIR) CO2 detector. However, the application of this method to the atmosphere presents a challenge due to the small signal above background at high ambient levels of common gas-phase carbon compounds (e.g., CO2). We show the Nr system is an accurate particle mass measurement method and demonstrate its ability to calibrate particle mass measurement instrumentation using single-component, laboratory-generated, Nr-containing particles below 2.5 µm in size. In addition we show agreement with mass measurements of an independently calibrated online particle-into-liquid sampler directly coupled to the electrospray ionization source of a quadrupole mass spectrometer (PILS–ESI/MS) sampling in the negative-ion mode. We obtain excellent correlations (R2 = 0.99) of particle mass measured as Nr with PILS–ESI/MS measurements converted to the corresponding particle anion mass (e.g., nitrate, sulfate, and chloride). The Nr and PILS–ESI/MS are shown to agree to within ∼ 6 % for particle mass loadings of up to 120 µg m−3. Consideration of all the sources of error in the PILS–ESI/MS technique yields an overall uncertainty of ±20 % for these single-component particle streams. These results demonstrate the Nr system is a reliable direct particle mass measurement technique that differs from other particle instrument calibration techniques that rely on knowledge of particle size, shape, density, and refractive index.
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Wang, Y. H., Z. R. Liu, J. K. Zhang, B. Hu, D. S. Ji, Y. C. Yu und Y. S. Wang. „Aerosol physicochemical properties and implication for visibility during an intense haze episode during winter in Beijing“. Atmospheric Chemistry and Physics Discussions 14, Nr. 16 (10.09.2014): 23375–413. http://dx.doi.org/10.5194/acpd-14-23375-2014.
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Abstract. The evolution of physical, chemical and optical properties of urban aerosol particles was characterized during an extreme haze episode in Beijing, PRC from 24 January through 31 January 2013 based on in-situ measurements. The average mass concentrations of PM1, PM2.5 and PM10 were 99 ± 67 μg m−3 (average ± stdev), 188 ± 128 μg m−3 and 265 ± 157 μg m−3, respectively. A significant increase in PM1−2.5 fraction was observed during the most heavily polluted periods. The average scattering coefficient (λ = 550 nm) was 877 ± 624 M m−1. An increasing relative amount of coarse particles can be deduced from the variations of backscattering ratios, asymmetry parameter and scattering Ångström exponent. Particle number size distributions between 14 nm and 2500 nm diameter showed high number concentrations, particularly in the nucleation mode and accumulation modes. Size-resolved chemical composition of submicron aerosol from a High Resolution-ToF-Aerosol Mass Spectrometer showed that the mass concentration of organic, sulfate, nitrate, ammonium and chlorine mainly resided on 500 nm to 800 nm (vacuum diameter) particles, and sulfate and ammonium contributed most to particle growth during the most heavily polluted day (28 January). Increasing relative humidity and stable synoptic conditions on 28 January combined with heavy pollution, lead to enhanced water uptake by the hygroscopic submicron particles and formation of secondary aerosol, maybe the main reasons for the severity of the haze episode. Light scattering apportionment showed that organic, ammonium sulfate, ammonium nitrate and ammonium chloride compounds contributed to light scattering fractions of 57%, 23%, 10% and 10%, respectively. This study indicated that the organic component in submicron aerosol plays an important role in visibility degradation in this haze episode in and around Beijing.
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Ciuraru, Raluca, Sylvie Gosselin, Nicolas Visez und Denis Petitprez. „Heterogeneous reactivity of chlorine atoms with ammonium sulfate and ammonium nitrate particles“. Physical Chemistry Chemical Physics 14, Nr. 13 (2012): 4527. http://dx.doi.org/10.1039/c2cp23455f.
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Nagayama, Seiichiro, Katsumi Katoh, Eiko Higashi, Masahiko Hayashi, Kosuke Kumagae, Hiroto Habu, Yuji Wada, Katsuyuki Nakano und Mitsuru Arai. „Moisture Proofing of Spray Dried Particles Comprising Ammonium Nitrate/Potassium Nitrate/Polymer“. Propellants, Explosives, Pyrotechnics 40, Nr. 4 (25.03.2015): 544–50. http://dx.doi.org/10.1002/prep.201400125.
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Slowik, J. G., D. J. Cziczo und J. P. D. Abbatt. „Analysis of cloud condensation nuclei composition and growth kinetics using a pumped counterflow virtual impactor and aerosol mass spectrometer“. Atmospheric Measurement Techniques Discussions 4, Nr. 1 (17.01.2011): 285–313. http://dx.doi.org/10.5194/amtd-4-285-2011.
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Abstract. We present a new method of determining the size and composition of CCN-active aerosol particles. Method utility is illustrated through a series of ambient measurements. A continuous-flow thermal-gradient diffusion chamber (TGDC), pumped counterflow virtual impactor (PCVI), and Aerodyne time-of-flight mass spectrometer (AMS) are operated in series. Ambient particles are sampled into the TGDC, where a constant supersaturation is maintained, and CCN-active particles grow to ~2.5±0.5 μm. The output flow from the TGDC is directed into the PCVI, where a counterflow of dry N2 gas opposes the particle-laden flow, creating a region of zero velocity. This stagnation plane can only be traversed by particles with sufficient momentum, which depends on their size. Particles that have activated in the TGDC cross the stagnation plane and are entrained in the PCVI output flow, while the unactivated particles are diverted to a pump. Because the input gas is replaced by the counterflow gas with better than 99% efficiency at the stagnation plane, the output flow consists almost entirely of dry N2 and water evaporates from the activated particles. In this way, the system yields an ensemble of CCN-active particles whose chemical composition and size are analyzed using the AMS. Measurements of urban aerosol in downtown Toronto identified an external mixture of CCN-active particles consisting almost entirely of ammonium nitrate and ammonium sulfate, with CCN-inactive particles of the same size consisting of a mixture of ammonium nitrate, ammonium sulfate, and organics. We also discuss results from the first field deployment of the TGDC-PCVI-AMS system, conducted from mid-May to mid-June 2007 in Egbert, Ontario, a semirural site ~80 km north of Toronto influenced both by clean air masses from the north and emissions from the city. Organic-dominated particles sampled during a major biogenic event exhibited higher CCN activity and/or faster growth kinetics than urban outflow from Toronto, despite the latter having a higher inorganic content and higher O:C ratio. During both events, particles were largely internally mixed.
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Slowik, J. G., D. J. Cziczo und J. P. D. Abbatt. „Analysis of cloud condensation nuclei composition and growth kinetics using a pumped counterflow virtual impactor and aerosol mass spectrometer“. Atmospheric Measurement Techniques 4, Nr. 8 (30.08.2011): 1677–88. http://dx.doi.org/10.5194/amt-4-1677-2011.
Annotation:
Abstract. We present a new method of determining the size and composition of CCN-active aerosol particles. Method utility is illustrated through a series of ambient measurements. A continuous-flow thermal-gradient diffusion chamber (TGDC), pumped counterflow virtual impactor (PCVI), and Aerodyne time-of-flight mass spectrometer (AMS) are operated in series. Ambient particles are sampled into the TGDC, where a constant supersaturation is maintained, and CCN-active particles grow to ~2.5 &pm; 0.5 μm. The output flow from the TGDC is directed into the PCVI, where a counterflow of dry N2 gas opposes the particle-laden flow, creating a region of zero axial velocity. This stagnation plane can only be traversed by particles with sufficient momentum, which depends on their size. Particles that have activated in the TGDC cross the stagnation plane and are entrained in the PCVI output flow, while the unactivated particles are diverted to a pump. Because the input gas is replaced by the counterflow gas with better than 99 % efficiency at the stagnation plane, the output flow consists almost entirely of dry N2 and water evaporates from the activated particles. In this way, the system yields an ensemble of CCN-active particles whose chemical composition and size are analyzed using the AMS. Measurements of urban aerosol in downtown Toronto identified an external mixture of CCN-active particles consisting almost entirely of ammonium nitrate and ammonium sulfate, with CCN-inactive particles of the same size consisting of a mixture of ammonium nitrate, ammonium sulfate, and organics. We also discuss results from the first field deployment of the TGDC-PCVI-AMS system, conducted from mid-May to mid-June 2007 in Egbert, Ontario, a semirural site ~80 km north of Toronto influenced both by clean air masses from the north and emissions from the city. Organic-dominated particles sampled during a major biogenic event exhibited higher CCN activity and/or faster growth kinetics than urban outflow from Toronto, despite the latter having a higher inorganic content and higher O:C ratio. During both events, particles were largely internally mixed.
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Liu, X. H., Y. J. Zhu, M. Zheng, H. W. Gao und X. H. Yao. „Production and growth of new particles during two cruise campaigns in the marginal seas of China“. Atmospheric Chemistry and Physics 14, Nr. 15 (11.08.2014): 7941–51. http://dx.doi.org/10.5194/acp-14-7941-2014.
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Abstract. In this paper, we investigated production and growth of new particles in the marine atmosphere during two cruise campaigns in China Seas using a Fast Mobility Particle Sizer. Only eight new particle formation (NPF) events (> 30 min) occurred on 5 days out of 31 sampling days, and the subsequent growth of new particles was observed only in five events. Apparent formation rates of new particles (in the range of 5.6–30 nm) varied from 0.3 to 15.2 particles cm−3 s−1 in eight events, and growth rates ranged from 2.5 to 10 nm h−1 in five NPF events. Modeling results simulated by US EPA Community Multi-scale Air Quality Model (CMAQ) showed that ammonium nitrate (NH4NO3) was newly formed in the atmosphere over the corresponding sea zone during 2 out of 5 events, in which new particles partially or mostly grew over 50 nm. However, in the remaining three events, new particles cannot grow over 30 nm, and the modeling results showed that no NH4NO3 was newly formed in the corresponding marine atmosphere. Modeling results also showed that formation of secondary organics occurred through all new particle growth periods. Difference between the two types of new particle growth patterns suggested that a combination of ammonium nitrate and organics newly formed likely contributed to the growth of new particles from 30 nm to larger size. However, the findings were obtained from the limited data, and the simulations of CMAQ also suffered from several weaknesses such as only having three size bins for different particles, lack of marine aerosol precursors, etc. More future studies are thereby needed for confirmation.
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Jeong, C. H., M. L. McGuire, K. J. Godri, J. G. Slowik, P. J. G. Rehbein und G. J. Evans. „Quantification of aerosol chemical composition using continuous single particle measurements“. Atmospheric Chemistry and Physics Discussions 11, Nr. 1 (17.01.2011): 1219–64. http://dx.doi.org/10.5194/acpd-11-1219-2011.
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Abstract. Mass concentrations of particulate matter (PM) chemical components were determined from data for 0.3 to 3.0 μm particles measured by an Aerosol Time-of-Flight Mass Spectrometer (ATOFMS) data at an urban and rural site. Hourly-averaged concentrations of nitrate, sulphate, ammonium, organic carbon, and elemental carbon, estimated based on scaled ATOFMS peak intensities of corresponding ion marker species, were compared with collocated chemical composition measurements by an Aerosol Mass Spectrometer (AMS), a Gas-Particle Ion Chromatograph (GPIC), and a Sunset Lab field OCEC analyzer. The highest correlation was found for nitrate, with correlation coefficients (Pearson r) of 0.89 and 0.85 at the urban and rural sites, respectively. ATOFMS mass calibration factors, determined for the urban site, were used to calculate mass concentrations of the major PM chemical components at the rural site. Mass reconstruction using this ATOFMS based composition data agreed very well with the total PM mass measured at the rural site. Size distributions of the ten main types of particles were resolved for the rural site and the mass composition of each particle type was determined in terms of sulphate, nitrate, ammonium, organic carbon and elemental carbon. This is the first study to estimate hourly mass concentrations of individual aerosol components and the mass composition of individual particle-types based on ATOFMS single particle measurements.
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Zhou, Shengzhen, Luolin Wu, Junchen Guo, Weihua Chen, Xuemei Wang, Jun Zhao, Yafang Cheng et al. „Measurement report: Vertical distribution of atmospheric particulate matter within the urban boundary layer in southern China – size-segregated chemical composition and secondary formation through cloud processing and heterogeneous reactions“. Atmospheric Chemistry and Physics 20, Nr. 11 (04.06.2020): 6435–53. http://dx.doi.org/10.5194/acp-20-6435-2020.
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Abstract. Many studies have recently been done on understanding the sources and formation mechanisms of atmospheric aerosols at ground level. However, vertical profiles and sources of size-resolved particulate matter within the urban boundary layer are still lacking. In this study, vertical distribution characteristics of size-segregated particles were investigated at three observation platforms (ground level, 118 m, and 488 m) on the 610 m high Canton Tower in Guangzhou, China. Size-segregated aerosol samples were simultaneously collected at the three levels in autumn and winter. Major aerosol components, including water-soluble ions, organic carbon, and elemental carbon, were measured. The results showed that daily average fine-particle concentrations generally decreased with height. Concentrations of sulfate and ammonium in fine particles displayed shallow vertical gradients, and nitrate concentrations increased with height in autumn, while the chemical components showed greater variations in winter than in autumn. The size distributions of sulfate and ammonium in both seasons were characterized by a dominant unimodal mode with peaks in the size range of 0.44–1.0 µm. In autumn, the nitrate size distribution was bimodal, peaking at 0.44–1.0 and 2.5–10 µm, while in winter it was unimodal, implying that the formation mechanisms for nitrate particles were different in the two seasons. Our results suggest that the majority of the sulfate and nitrate is formed from aqueous-phase reactions, and we attribute coarse-mode nitrate formation at the measurement site to the heterogeneous reactions of gaseous nitric acid on existing sea-derived coarse particles in autumn. Case studies further showed that atmospheric aqueous-phase and heterogeneous reactions could be important mechanisms for sulfate and nitrate formation, which, in combination with adverse weather conditions such as temperature inversion and calm wind, led to haze formation during autumn and winter in the Pearl River Delta (PRD) region.
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Sullivan, R. C., S. A. Guazzotti, D. A. Sodeman und K. A. Prather. „Direct observations of the atmospheric processing of Asian mineral dust“. Atmospheric Chemistry and Physics 7, Nr. 5 (22.02.2007): 1213–36. http://dx.doi.org/10.5194/acp-7-1213-2007.
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Abstract. The accumulation of secondary acids and ammonium on individual mineral dust particles during ACE-Asia has been measured with an online single-particle mass spectrometer, the ATOFMS. Changes in the amounts of sulphate, nitrate, and chloride mixed with dust particles correlate with air masses from different source regions. The uptake of secondary acids depended on the individual dust particle mineralogy; high amounts of nitrate accumulated on calcium-rich dust while high amounts of sulphate accumulated on aluminosilicate-rich dust. Oxidation of S(IV) to S(VI) by iron in the aluminosilicate dust is a possible explanation for this enrichment of sulphate, which has important consequences for the fertilization of remote oceans by soluble iron. This study shows the segregation of sulphate from nitrate and chloride in individual aged dust particles for the first time. A transport and aging timeline provides an explanation for the observed segregation. Our data suggests that sulphate became mixed with the dust first. This implies that the transport pathway is more important than the reaction kinetics in determining which species accumulate on mineral dust. Early in the study, dust particles in volcanically influenced air masses were mixed predominately with sulphate. Dust mixed with chloride then dominated over sulphate and nitrate when a major dust front reached the R. V. Ronald Brown. We hypothesize that the rapid increase in chloride on dust was due to mixing with HCl(g) released from acidified sea salt particles induced by heterogeneous reaction with volcanic SO2(g), prior to the arrival of the dust front. The amount of ammonium mixed with dust correlated strongly with the total amount of secondary acid reaction products in the dust. Submicron dust and ammonium sulphate were internally mixed, contrary to frequent reports that they exist as external mixtures. The size distribution of the mixing state of dust with these secondary species validates previous mechanisms of the atmospheric processing of dust and generally agrees with simulated aerosol chemistry from the STEM-2K3 model. This series of novel results has important implications for improving the treatment of dust in global chemistry models and highlights a number of key processes that merit further investigation through laboratory and field studies.
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Cho, Hee-Joo, Jia Kang, Dohyeong Kim, Arom Seo, Minhan Park, Hungsoo Joo und Kihong Park. „A Study on Elevated Concentrations of Submicrometer Particles in an Urban Atmosphere“. Atmosphere 9, Nr. 10 (10.10.2018): 393. http://dx.doi.org/10.3390/atmos9100393.
Annotation:
Mass concentrations of chemical constituents (organics, nitrate, sulfate, ammonium, chloride, and black carbon (BC)) and the number size distribution of submicrometer particles in the ambient atmosphere were continuously measured in urban Gwangju, Korea, during the Megacity Air Pollution Studies (MAPS)-Seoul campaign. Organics (9.1 μg/m3) were the most dominant species, followed by sulfate (4.7 μg/m3), nitrate (3.2 μg/m3), ammonium (2.6 μg/m3), and BC (1.3 μg/m3) in submicrometer particles (particulate matter less than 1 μm (PM1)). The potential source regions of the sulfate were located in the South and East regions of China and South and East regions of Korea, while local sources were responsible for the elevated BC concentration. Diurnal variation showed that concentrations of organics, nitrate, ammonium, chloride, and BC decreased with increasing mixing layer and wind speed (dilution effect), while sulfate and oxidized organics increased possibly due to their strong photochemical production in the afternoon. During the campaign, an elevated mass concentration of PM1 (PM1 event) and number concentration (nanoparticle formation (NPF) event) were observed (one PM1 event and nine NPF events out of 28 days). The PM1 event occurred with Western and Southwestern air masses with increasing sulfate and organics. Long-range transported aerosols and stagnant meteorological conditions favored the elevated mass concentration of submicrometer particles. Most of the NPF events took place between 10:00 and 14:00, and the particle growth rates after the initial nanoparticle formation were 7.2–11.0 nm/h. The times for increased concentration of nanoparticles and their growth were consistent with those for elevated sulfate and oxidized organics in submicrometer particles under strong photochemical activity.