scholarly journals Ion-molecule interactions enable unexpected phase transitions in organic-inorganic aerosol

2020 ◽  
Vol 6 (47) ◽  
pp. eabb5643 ◽  
Author(s):  
David S. Richards ◽  
Kristin L. Trobaugh ◽  
Josefina Hajek-Herrera ◽  
Chelsea L. Price ◽  
Craig S. Sheldon ◽  
...  
Keyword(s):  
Air Quality ◽  
Inorganic Ions ◽  
Climate Projections ◽  
Atmospheric Models ◽  
Inorganic Aerosols ◽  
Low Mass ◽  
Inorganic Aerosol ◽  
Semi Solid ◽  
Molecule Interactions ◽  
Inorganic Fraction

Atmospheric aerosol particles are commonly complex, aqueous organic-inorganic mixtures, and accurately predicting the properties of these particles is essential for air quality and climate projections. The prevailing assumption is that aqueous organic-inorganic aerosols exist predominately with liquid properties and that the hygroscopic inorganic fraction lowers aerosol viscosity relative to the organic fraction alone. Here, in contrast to those assumptions, we demonstrate that increasing inorganic fraction can increase aerosol viscosity (relative to predictions) and enable a humidity-dependent gel phase transition through cooperative ion-molecule interactions that give rise to long-range networks of atmospherically relevant low-mass oxygenated organic molecules (180 to 310 Da) and divalent inorganic ions. This supramolecular, ion-molecule effect can drastically influence the phase and physical properties of organic-inorganic aerosol and suggests that aerosol may be (semi)solid under more conditions than currently predicted. These observations, thus, have implications for air quality and climate that are not fully represented in atmospheric models.

scholarly journals Understanding and improving model representation of aerosol optical properties for a Chinese haze event measured during KORUS-AQ

2019 ◽  
Author(s):  
Pablo E. Saide ◽  
Meng Gao ◽  
Zifeng Lu ◽  
Dan Goldberg ◽  
David G. Streets ◽  
...  
Keyword(s):  
Optical Properties ◽  
Air Quality ◽  
Data Assimilation ◽  
Health Effect ◽  
Model Representation ◽  
Climate Projections ◽  
Hygroscopic Growth ◽  
Multiple Sources ◽  
Inorganic Aerosols ◽  
Aerosol Mass

Abstract. KORUS-AQ was an international cooperative air quality field study in South Korea that measured local and remote sources of air pollution affecting the Korean peninsula during May–June 2016. Some of the largest aerosol mass concentrations were measured during a Chinese haze transport event (May 24th). Air quality forecasts using the WRF-Chem model with aerosol optical depth (AOD) data assimilation captured AOD during this pollution episode but over-predicted surface particulate matter concentrations, especially PM2.5 often by a factor of 2 or larger. Analysis revealed multiple sources of model deficiency related to the calculation of optical properties from aerosol mass that explain these discrepancies. Using in-situ observations of aerosol size and composition as inputs to the optical properties calculations showed that using a low resolution size bin representation under-estimates the efficiency at which aerosols scatter and absorb light (mass extinction efficiency). Besides using finer-resolution size bins, it was also necessary to increase the refractive indices and hygroscopicity of select aerosol species within the range of values reported in the literature to achieve consistency with measured values of mass/volume extinction efficiencies and light scattering enhancement factor (f(RH)) due to aerosol hygroscopic growth. Furthermore, evaluation of optical properties obtained using modeled aerosol properties revealed the inability of sectional and modal aerosol representations in WRF-Chem to properly reproduce the observed size distribution, with the models displaying a much wider accumulation mode. Other model deficiencies included an under-estimate of organic aerosol density and an over-prediction of the fractional contribution of inorganic aerosols other than sulfate, ammonium, nitrate, chloride and sodium (mostly dust). These results illustrate the complexity of achieving an accurate model representation of optical properties and provide potential solutions that are relevant to multiple disciplines and applications such as air quality forecasts, health-effect assessments, climate projections, solar-power forecasts, and aerosol data assimilation.

scholarly journals Summertime impacts of Eastern Mediterranean megacity emissions on air quality

2011 ◽  
Vol 11 (9) ◽  
pp. 26657-26690 ◽  
Author(s):  
U. Im ◽  
M. Kanakidou
Keyword(s):  
Air Quality ◽  
Rural Areas ◽  
Eastern Mediterranean ◽  
Anthropogenic Emissions ◽  
Urban Agglomerations ◽  
Mixing Ratios ◽  
Urban Core ◽  
Local Contribution ◽  
Regional Air Quality ◽  
Inorganic Aerosol

Abstract. Megacities are large urban agglomerations with intensive anthropogenic emissions that have significant impacts on local and regional air quality. In the present mesoscale modeling study, the impacts of anthropogenic emissions from Istanbul and Athens on local and regional air quality in the Eastern Mediterranean are quantified and the responses to hypothetical decentralization scenarios applied to the extended areas of these densely populated regions are evaluated. This study focuses on summertime impacts on air quality. The results show that Athens emissions have larger regional (0.8%) and downwind (2.7% at Finokalia) impacts on O3 than Istanbul emissions that contribute to surface O3 by 0.6% to the domain-mean and 2.1% to the levels at Finokalia. On the opposite, regarding fine particle (PM2.5) levels, Istanbul emissions have larger contribution both inside the megacity itself (75%) and regionally (2.4%) compared to Athens emissions, which have a local contribution of 65% and domain-wide contribution of 0.4%. Biogenic emissions are found to limit the production of secondary inorganic aerosol species due to their impact on oxidant levels. Hypothetical decentralization plans for these urban agglomerations, maintaining the total amount of their anthropogenic emissions constant but homogeneously distributing it over larger "new" extended areas, would result in higher O3 mixing ratios inside the urban core (215% and 26% in Istanbul and Athens, respectively). On the opposite, PM2.5 concentrations would decrease by 67% and 60% in Istanbul and Athens, respectively, whereas they would increase by 10% and 11% in the rural areas of Istanbul and Athens, respectively. Concerning the "new" extended areas, Athens would experience a reduction in O3 mixing ratios by ~2% whereas Istanbul would experience an increase by ~15%. Overall decreases of PM2.5 levels by 32% and 9% are calculated over the Istanbul and Athens "new" extended areas.

scholarly journals Improvement from the satellite-derived NO<sub>x</sub> emissions on air quality modeling and its effect on ozone and secondary inorganic aerosol formation in Yangtze River Delta, China

2020 ◽  
Author(s):  
Yang Yang ◽  
Yu Zhao ◽  
Lei Zhang ◽  
Jie Zhang ◽  
Xin Huang ◽  
...  
Keyword(s):  
Air Quality ◽  
Model Performance ◽  
Yangtze River Delta ◽  
Nox Emissions ◽  
Top Down ◽  
Bottom Up ◽  
Inorganic Aerosols ◽  
Quality Modeling ◽  
Emission Estimation ◽  
Reduced Rate

Abstract. We developed a top-down methodology combining the inversed chemistry transport modeling and satellite-derived tropospheric vertical column of NO2, and estimated the NOx emissions of Yangtze River Delta (YRD) region at a horizontal resolution of 9 km for January, April, July and October 2016. The effect of the top-down emission estimation on air quality modeling, and the response of ambient ozone (O3) and secondary inorganic aerosols (SO42−, NO3−, and NH4+, SNA) to the changed precursor emissions were evaluated with the Community Multi-scale Air Quality (CMAQ) system. The top-down estimates of NOx emissions were smaller than those in a national emission inventory, MEIC (i.e., the bottom-up estimates), for all the four months, and the monthly mean was calculated at 260.0 Gg/month, 24 % less than the bottom-up one. The NO2 concentrations simulated with the bottom-up estimate of NOx emissions were clearly higher than the ground observation, indicating the possible overestimation in current emission inventory attributed to its insufficient consideration of recent emission control in the region. The model performance based on top-down estimate was much better, and the biggest change was found for July with the normalized mean bias (NMB) and normalized mean error (NME) reduced from 111 % to −0.4 % and from 111 % to 33 %, respectively. The results demonstrate the improvement of NOx emission estimation with the nonlinear inversed modeling and satellite observation constraint. With the smaller NOx emissions in the top-down estimate than the bottom-up one, the elevated concentrations of ambient O3 were simulated for most YRD and they were closer to observation except for July, implying the VOC (volatile organic compound)-limit regime of O3 formation. With available ground observations of SNA in the YRD, moreover, better model performance of NO3− and NH4+ were achieved for most seasons, implying the effectiveness of precursor emission estimation on the simulation of secondary inorganic aerosols. Through the sensitivity analysis of O3 formation for April 2016, the decreased O3 concentrations were found for most YRD region when only VOCs emissions were reduced or the reduced rate of VOCs emissions was two times of that of NOx, implying the crucial role of VOCs control on O3 pollution abatement. The SNA level for January 2016 was simulated to decline 12 % when 30 % of NH3 emissions were reduced, while the change was much smaller with the same reduced rate for SO2 or NOx. The result suggests that reducing NH3 emissions was the most effective way to alleviate SNA pollution for YRD in winter.

scholarly journals Semi-continuous gas and inorganic aerosol measurements at a Finnish urban site: comparisons with filters, nitrogen in aerosol and gas phases, and aerosol acidity

2012 ◽  
Vol 12 (2) ◽  
pp. 4755-4796 ◽  
Author(s):  
U. Makkonen ◽  
A. Virkkula ◽  
J. Mäntykenttä ◽  
H. Hakola ◽  
P. Keronen ◽  
...  
Keyword(s):  
Particle Number ◽  
Road Traffic ◽  
Large Fraction ◽  
Inorganic Ions ◽  
Urban Site ◽  
Vehicle Exhaust ◽  
Gas Phases ◽  
Aerosol Acidity ◽  
Inorganic Aerosol ◽  
Online Monitor

Abstract. Concentrations of 5 gases (HCl, HNO3, HONO, NH3, SO2) and 8 major inorganic ions in particles (Cl−, NO3−, SO42−, NH4+, Na+, K+, Mg2+, Ca2+) were measured with an online monitor MARGA 2S in two size ranges, Dp < 2.5 μm and Dp < 10 μm, in Helsinki, Finland from November 2009 to May 2010. The results were compared with filter sampling, mass concentrations obtained from particle number size distributions, and a conventional SO2 monitor. The MARGA yielded lower concentrations than those analyzed from the filter samples for most ions. Linear regression yielded MARGA vs. filter slopes of 0.68, 0.89, 0.84, 0.52, 0.88, 0.17, 2.88, and 3.04 for Cl−, NO3−, SO42−, NH4+, Na+, K+, Mg2+, and Ca2+, respectively, and 0.90 for the MARGA vs. SO2 monitor. There were clear seasonal cycles in the concentrations of the nitrogen-containing gases: the median concentrations of HNO3, HONO, and NH3 were 0.09 ppb, 0.37 ppb, and 0.01 ppb in winter, respectively, and 0.15, 0.15, and 0.14 in spring, respectively. The gas-phase fraction of nitrogen decreased roughly with decreasing temperature so that in the coldest period from January to February the median contribution was 28% but in April to May 53%. There were also large fractionation variations that temperature alone cannot explain. HONO correlated well with NOx but a large fraction of the HONO-to-NOx ratios were larger than published ratios in a road traffic tunnel suggesting that a large amount of HONO had other sources than vehicle exhaust. Aerosol acidity was estimated by calculating ion equivalent ratios. The sources of acidic aerosols were studied with trajectory statistics that showed that continental aerosol is mainly neutralized and marine aerosol acidic.

scholarly journals Computation of liquid-liquid equilibria and phase stabilities: implications for RH-dependent gas/particle partitioning of organic-inorganic aerosols

2010 ◽  
Vol 10 (16) ◽  
pp. 7795-7820 ◽  
Author(s):  
A. Zuend ◽  
C. Marcolli ◽  
T. Peter ◽  
J. H. Seinfeld
Keyword(s):  
Phase Separation ◽  
Liquid Phase ◽  
Water Solubility ◽  
Inorganic Compounds ◽  
Liquid Phase Separation ◽  
Miscibility Gap ◽  
Inorganic Aerosols ◽  
Particulate Mass ◽  
Inorganic Aerosol ◽  
Liquid Liquid Phase Separation

Abstract. Semivolatile organic and inorganic aerosol species partition between the gas and aerosol particle phases to maintain thermodynamic equilibrium. Liquid-liquid phase separation into an organic-rich and an aqueous electrolyte phase can occur in the aerosol as a result of the salting-out effect. Such liquid-liquid equilibria (LLE) affect the gas/particle partitioning of the different semivolatile compounds and might significantly alter both particle mass and composition as compared to a one-phase particle. We present a new liquid-liquid equilibrium and gas/particle partitioning model, using as a basis the group-contribution model AIOMFAC (Zuend et al., 2008). This model allows the reliable computation of the liquid-liquid coexistence curve (binodal), corresponding tie-lines, the limit of stability/metastability (spinodal), and further thermodynamic properties of multicomponent systems. Calculations for ternary and multicomponent alcohol/polyol-water-salt mixtures suggest that LLE are a prevalent feature of organic-inorganic aerosol systems. A six-component polyol-water-ammonium sulphate system is used to simulate effects of relative humidity (RH) and the presence of liquid-liquid phase separation on the gas/particle partitioning. RH, salt concentration, and hydrophilicity (water-solubility) are identified as key features in defining the region of a miscibility gap and govern the extent to which compound partitioning is affected by changes in RH. The model predicts that liquid-liquid phase separation can lead to either an increase or decrease in total particulate mass, depending on the overall composition of a system and the particle water content, which is related to the hydrophilicity of the different organic and inorganic compounds. Neglecting non-ideality and liquid-liquid phase separations by assuming an ideal mixture leads to an overestimation of the total particulate mass by up to 30% for the composition and RH range considered in the six-component system simulation. For simplified partitioning parametrizations, we suggest a modified definition of the effective saturation concentration, Cj*, by including water and other inorganics in the absorbing phase. Such a Cj* definition reduces the RH-dependency of the gas/particle partitioning of semivolatile organics in organic-inorganic aerosols by an order of magnitude as compared to the currently accepted definition, which considers the organic species only.

scholarly journals Sensitivity of organic aerosol simulation scheme on biogenic organic aerosol concentrations in climate projections

2019 ◽  
Author(s):  
Arineh Cholakian ◽  
Matthias Beekmann ◽  
Isabelle Coll ◽  
Giancarlo Ciarelli ◽  
Augustin Colette
Keyword(s):  
Air Quality ◽  
Organic Aerosol ◽  
Basis Set ◽  
Climate Projections ◽  
Large Contribution ◽  
Climate Variables ◽  
European Area ◽  
Aerosol Aging ◽  
Relative Change ◽  
Molecular Scheme

Abstract. Organic aerosol can have important impacts on air quality and human health because of its chemical composition and its large contribution to the atmospheric fine aerosols. Simulation of this aerosol is difficult since there are many unknowns in the nature, mechanism and processes involved in the formation of these aerosols. These uncertainties become even more important in the context of a changing climate, because different mechanisms, and their representation in atmospheric models, imply different sensitivities to changes in climate variables. In this work, the effects caused by using different schemes to simulate OA are explored. Three schemes are used in this work: a molecular scheme, a standard volatility basis set (VBS) scheme with anthropogenic aging and a modified VBS scheme containing functionalization, fragmentation and formation of non-volatile SOA formation for all semi-volatile organic compounds (SVOCs). 5 years of historic and 5 years of future simulations were performed using the RCP8.5 climatic scenario. The years were chosen in a way to maximize the differences between future and historic simulations. The comparisons show that for the European area, the modified VBS scheme shows the highest relative change between future and historic simulations, while the molecular scheme shows the lowest (a factor of two lower). These changes are maximized over the summer period for biogenic SOA (BSOA) because the higher temperatures increase terpene and isoprene emissions, the major precursors of BSOA. This increase is partially off-set by a temperature induced shift of SVOCs to gas phase. This shift is indeed scheme dependent, and it is shown that it is the least pronounced for the modified VBS scheme including a full suite of aerosol aging processes, comprising also formation of non-volatile aerosol. For the Mediterranean Sea, without BVOC emissions, the OA changes are less pronounced and, at least on an annual average, more similar between different schemes. Absolute concentrations between different schemes are also different. Our results warrant further developments in organic aerosol schemes used for air quality modelling to reduce their uncertainty, including sensitivity to climate variables (temperature).

scholarly journals Using L dwarfs with distances to test models

2012 ◽  
Vol 8 (S289) ◽  
pp. 425-428
Author(s):  
Youfen Wang ◽  
H. R. A. Jones ◽  
R. L. Smart ◽  
Z. Shao
Keyword(s):  
The Other ◽  
Absorption Lines ◽  
Atmospheric Models ◽  
Test Models ◽  
Low Mass ◽  
L Dwarfs

AbstractWe test two contemporary low-mass atmospheric models using three L dwarfs with distances and published spectra. We find that the two models do not predict the same trends for temperature, gravity and metallicity in absorption lines. We find that one model appears to better reflect the temperature, but this sample is too small to investigate the other parameters in depth.

scholarly journals Global Warming Will Aggravate Ozone Pollution in the U.S. Mid-Atlantic

2019 ◽  
Vol 58 (6) ◽  
pp. 1267-1278 ◽  
Author(s):  
Cristina L. Archer ◽  
Joseph F. Brodie ◽  
Sara A. Rauscher
Keyword(s):  
Global Warming ◽  
Air Quality ◽  
Coupled Model ◽  
Historical Period ◽  
Climate Projections ◽  
Ozone Pollution ◽  
Near Surface ◽  
Weather Patterns ◽  
Temperature And Precipitation ◽  
The U.S

AbstractThe goal of this study is to evaluate the effects of anthropogenic climate change on air quality, in particular on ozone, during the summer in the U.S. mid-Atlantic region. First, we establish a connection between high-ozone (HO) days, defined as those with observed 8-h average ozone concentration greater than 70 parts per billion (ppb), and certain weather patterns, called synoptic types. We identify four summer synoptic types that most often are associated with HO days based on a 30-yr historical period (1986–2015) using NCEP–NCAR reanalysis. Second, we define thresholds for mean near-surface temperature and precipitation that characterize HO days during the four HO synoptic types. Next, we look at climate projections from five models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) for the early and late midcentury (2025–34 and 2045–54) and analyze the frequency of HO days. We find a general increasing trend, weaker in the early midcentury and stronger in the late midcentury, with 2 and 5 extra HO days per year, respectively, from 16 in 2015. These 5 extra days are the result of two processes. On one hand, the four HO synoptic types will increase in frequency, which explains about 1.5–2 extra HO days. The remaining 3–3.5 extra days are explained by the increase in near-surface temperatures during the HO synoptic types. Future air quality regulations, which have been successful in the historical period at reducing ozone concentrations in the mid-Atlantic, may need to become stricter to compensate for the underlying increasing trends from global warming.

scholarly journals Simulating Secondary Inorganic Aerosols using the chemistry transport model MOCAGE version R2.15.0

2015 ◽  
Vol 8 (4) ◽  
pp. 3593-3651 ◽  
Author(s):  
J. Guth ◽  
B. Josse ◽  
V. Marécal ◽  
M. Joly
Keyword(s):  
North America ◽  
Transport Model ◽  
Regional Scale ◽  
In Situ Measurements ◽  
Aerosol Composition ◽  
Chemistry Transport Model ◽  
Inorganic Aerosols ◽  
Modis Aod ◽  
Inorganic Aerosol

Abstract. In this study we develop a Secondary Inorganic Aerosol (SIA) module for the chemistry transport model MOCAGE developed at CNRM. Based on the thermodynamic equilibrium module ISORROPIA II, the new version of the model is evaluated both at the global scale and at the regional scale. The results show high concentrations of secondary inorganic aerosols in the most polluted regions being Europe, Asia and the eastern part of North America. Asia shows higher sulfate concentrations than other regions thanks to emissions reduction in Europe and North America. Using two simulations, one with and the other without secondary inorganic aerosol formation, the model global outputs are compared to previous studies, to MODIS AOD retrievals, and also to in situ measurements from the HTAP database. The model shows a better agreement in all geographical regions with MODIS AOD retrievals when introducing SIA. It also provides a good statistical agreement with in situ measurements of secondary inorganic aerosol composition: sulfate, nitrate and ammonium. In addition, the simulation with SIA gives generally a better agreement for secondary inorganic aerosols precursors (nitric acid, sulfur dioxide, ammonia) in particular with a reduction of the Modified Normalised Mean Bias (MNMB). At the regional scale, over Europe, the model simulation with SIA are compared to the in situ measurements from the EMEP database and shows a good agreement with secondary inorganic aerosol composition. The results at the regional scale are consistent with those obtained with the global simulations. The AIRBASE database was used to compare the model to regulated air quality pollutants being particulate matter, ozone and nitrogen dioxide concentrations. The introduction of the SIA in MOCAGE provides a reduction of the PM2.5 MNMB of 0.44 on a yearly basis and even 0.52 on a three spring months period (March, April, May) when SIA are maximum.

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