Special Issue "Atmospheric Composition Observations"

A special issue of Atmosphere (ISSN 2073-4433). This special issue belongs to the section "Air Quality".

Deadline for manuscript submissions: closed (31 August 2015).

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A printed edition of this Special Issue is available here.

Special Issue Editor

Prof. Dr. Armin Sorooshian
E-Mail Website
Guest Editor
1. Department of Chemical and Environmental Engineering, University of Arizona, Tucson, AZ 85721, USA
2. Department of Hydrology and Atmospheric Sciences, University of Arizona, Tucson, AZ 85721, USA
Interests: surface and airborne measurements of aerosol composition, size, and water-uptake properties; aerosol-cloud-precipitation interactions; ocean-land-atmosphere interactions; cloud water and precipitation chemistry; satellite data analysis

Special Issue Information

Dear Colleagues,

The composition of the atmosphere is a critical factor in understanding the nature and magnitude of processes associated with the planet’s energy balance, clouds and precipitation, biogeochemical cycling of nutrients, and public health and welfare. A detailed understanding of trace gases, aerosol particles, and hydrometeors is challenging due to the combination of their physicochemical complexity, variable lifetimes, and spatial inhomogeneity. Recent advances in instrumentation have resulted in improved measurements and an increased understanding of atmospheric composition. Laboratory and field in-situ measurement studies have benefited from such improvements, including improved spatial and temporal resolution, the ability to sample in challenging conditions (e.g., on airborne platforms, in clouds, at widely ranging pressure and temperature conditions), and the ability to measure a wider range of chemical species, and in the case of aerosol particles, to detect smaller sizes. Remote sensing capabilities have increased in recent years, thus offering new views of atmospheric composition across broad spatiotemporal ranges.

Manuscripts related to all aspects of atmospheric observations are welcome for this Special Issue, including advances in observational techniques and scientific insights about atmospheric composition.

Prof. Dr. Armin Sorooshian
Guest Editor

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Keywords

  • aerosol
  • gases
  • cloud processing
  • aqueous chemistry
  • volatile organic compounds
  • biogenic
  • anthropogenic
  • remote sensing
  • in-situ measurements

Published Papers (15 papers)

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Research

Article
Characterization of Fine Particulate Matter Emitted from the Resuspension of Road and Pavement Dust in the Metropolitan Area of São Paulo, Brazil
Atmosphere 2016, 7(3), 31; https://doi.org/10.3390/atmos7030031 - 23 Feb 2016
Cited by 23 | Viewed by 2963
Abstract
Many studies have been performed in order to characterize the sources of airborne particles in the Metropolitan Area of São Paulo (MASP), in Brazil. Those studies have been based on receptor modeling and most of the uncertainties in their results are related to [...] Read more.
Many studies have been performed in order to characterize the sources of airborne particles in the Metropolitan Area of São Paulo (MASP), in Brazil. Those studies have been based on receptor modeling and most of the uncertainties in their results are related to the emission profile of the resuspended road dust particles. In this study, we analyzed the composition of resuspended road dust particles in different environments: local streets, paved roads inside traffic tunnels, and high traffic streets. We analyzed the samples to quantify the concentrations of trace elements and black carbon. On the basis of that analysis, we developed emission profiles of the resuspended road dust that are representative of the different types of urban pavement in the MASP. This study is important given the international efforts in improving emissions factors with local characteristics, mainly in South America and other regions for which there is a lack of related information. This work presents emission profiles derived from resuspended road dust samples that are representative of the different types of urban pavement in the Metropolitan Area of São Paulo. Full article
(This article belongs to the Special Issue Atmospheric Composition Observations)
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Article
Decreasing Aerosol Loading in the North American Monsoon Region
Atmosphere 2016, 7(2), 24; https://doi.org/10.3390/atmos7020024 - 05 Feb 2016
Cited by 6 | Viewed by 2567
Abstract
We examine the spatio-temporal variability of aerosol loading in the recent decade (2005–2014) over the North American Monsoon (NAM) region. Emerging patterns are characterized using aerosol optical depth (AOD) retrievals from the NASA Terra/Moderate Resolution Imaging Spectroradiometer (MODIS) instrument along with a suite [...] Read more.
We examine the spatio-temporal variability of aerosol loading in the recent decade (2005–2014) over the North American Monsoon (NAM) region. Emerging patterns are characterized using aerosol optical depth (AOD) retrievals from the NASA Terra/Moderate Resolution Imaging Spectroradiometer (MODIS) instrument along with a suite of satellite retrievals of atmospheric and land-surface properties. We selected 20 aerosol hotspots and classified them into fire, anthropogenic, dust, and NAM alley clusters based on the dominant driver influencing aerosol variability. We then analyzed multivariate statistics of associated anomalies during pre-, monsoon, and post-monsoon periods. Our results show a decrease in aerosol loading for the entire NAM region, confirming previous reports of a declining AOD trend over the continental United States. This is evident during pre-monsoon and monsoon for fire and anthropogenic clusters, which are associated with a decrease in the lower and upper quartile of fire counts and carbon monoxide, respectively. The overall pattern is obfuscated in the NAM alley, especially during monsoon and post-monsoon seasons. While the NAM alley is mostly affected by monsoon precipitation, the frequent occurrence of dust storms in the area modulates this trend. We find that aerosol loading in the dust cluster is associated with observed vegetation index and has only slightly decreased in the recent decade. Full article
(This article belongs to the Special Issue Atmospheric Composition Observations)
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Article
Windblown Dust Deposition Forecasting and Spread of Contamination around Mine Tailings
Atmosphere 2016, 7(2), 16; https://doi.org/10.3390/atmos7020016 - 28 Jan 2016
Cited by 16 | Viewed by 2818
Abstract
Wind erosion, transport and deposition of windblown dust from anthropogenic sources, such as mine tailings impoundments, can have significant effects on the surrounding environment. The lack of vegetation and the vertical protrusion of the mine tailings above the neighboring terrain make the tailings [...] Read more.
Wind erosion, transport and deposition of windblown dust from anthropogenic sources, such as mine tailings impoundments, can have significant effects on the surrounding environment. The lack of vegetation and the vertical protrusion of the mine tailings above the neighboring terrain make the tailings susceptible to wind erosion. Modeling the erosion, transport and deposition of particulate matter from mine tailings is a challenge for many reasons, including heterogeneity of the soil surface, vegetative canopy coverage, dynamic meteorological conditions and topographic influences. In this work, a previously developed Deposition Forecasting Model (DFM) that is specifically designed to model the transport of particulate matter from mine tailings impoundments is verified using dust collection and topsoil measurements. The DFM is initialized using data from an operational Weather Research and Forecasting (WRF) model. The forecast deposition patterns are compared to dust collected by inverted-disc samplers and determined through gravimetric, chemical composition and lead isotopic analysis. The DFM is capable of predicting dust deposition patterns from the tailings impoundment to the surrounding area. The methodology and approach employed in this work can be generalized to other contaminated sites from which dust transport to the local environment can be assessed as a potential route for human exposure. Full article
(This article belongs to the Special Issue Atmospheric Composition Observations)
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Article
Frequency and Character of Extreme Aerosol Events in the Southwestern United States: A Case Study Analysis in Arizona
Atmosphere 2016, 7(1), 1; https://doi.org/10.3390/atmos7010001 - 23 Dec 2015
Cited by 20 | Viewed by 2416
Abstract
This study uses more than a decade’s worth of data across Arizona to characterize the spatiotemporal distribution, frequency, and source of extreme aerosol events, defined as when the concentration of a species on a particular day exceeds that of the average plus two [...] Read more.
This study uses more than a decade’s worth of data across Arizona to characterize the spatiotemporal distribution, frequency, and source of extreme aerosol events, defined as when the concentration of a species on a particular day exceeds that of the average plus two standard deviations for that given month. Depending on which of eight sites studied, between 5% and 7% of the total days exhibited an extreme aerosol event due to either extreme levels of PM10, PM2.5, and/or fine soil. Grand Canyon exhibited the most extreme event days (120, i.e., 7% of its total days). Fine soil is the pollutant type that most frequently impacted multiple sites at once at an extreme level. PM10, PM2.5, fine soil, non-Asian dust, and Elemental Carbon extreme events occurred most frequently in August. Nearly all Asian dust extreme events occurred between March and June. Extreme Elemental Carbon events have decreased as a function of time with statistical significance, while other pollutant categories did not show any significant change. Extreme events were most frequent for the various pollutant categories on either Wednesday or Thursday, but there was no statistically significant difference in the number of events on any particular day or on weekends versus weekdays. Full article
(This article belongs to the Special Issue Atmospheric Composition Observations)
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Article
Effect of Nearby Forest Fires on Ground Level Ozone Concentrations in Santiago, Chile
Atmosphere 2015, 6(12), 1926-1938; https://doi.org/10.3390/atmos6121838 - 17 Dec 2015
Cited by 12 | Viewed by 3629
Abstract
On 4 and 8 January 2014, at the height of the austral summer, intense wildfires in forests and dry pastures occurred in the Melipilla sector, located about 70 km to the southwest of Santiago, the Chilean capital, affecting more than 6 million inhabitants. [...] Read more.
On 4 and 8 January 2014, at the height of the austral summer, intense wildfires in forests and dry pastures occurred in the Melipilla sector, located about 70 km to the southwest of Santiago, the Chilean capital, affecting more than 6 million inhabitants. Low level winds transported the forest fire plume towards Santiago causing a striking decrease in visibility and a marked increase in the concentration of both primary (PM10 and CO) and secondary (Ozone) pollutants in the urban atmosphere. In particular, ozone maximum concentrations in the Santiago basin reached hourly averages well above 80 ppb, the national air quality standard. This ozone increase took place at the three sampling sites considered in the present study. These large values can be explained in terms of high NOx concentrations and NO2/NO ratios in biomass burning emissions. Full article
(This article belongs to the Special Issue Atmospheric Composition Observations)
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Article
The Influence of Sandstorms and Long-Range Transport on Polycyclic Aromatic Hydrocarbons (PAHs) in PM2.5 in the High-Altitude Atmosphere of Southern China
Atmosphere 2015, 6(11), 1633-1651; https://doi.org/10.3390/atmos6111633 - 30 Oct 2015
Cited by 13 | Viewed by 3049
Abstract
PM2.5 (Particulate Matter 2.5) samples were collected at Mount Heng and analyzed for polycyclic aromatic hydrocarbons (PAHs). During sampling, a sandstorm from northern China struck Mount Heng and resulted in a mean PM2.5 concentration of 150.61 μg/m3, which greatly [...] Read more.
PM2.5 (Particulate Matter 2.5) samples were collected at Mount Heng and analyzed for polycyclic aromatic hydrocarbons (PAHs). During sampling, a sandstorm from northern China struck Mount Heng and resulted in a mean PM2.5 concentration of 150.61 μg/m3, which greatly exceeded the concentration measured under normal conditions (no sandstorm: 58.50 μg/m3). The average mass of PAHs in PM2.5 was 30.70 μg/g, which was much lower than in the non-sandstorm samples (80.80 μg/g). Therefore, the sandstorm increased particle levels but decreased PAH concentrations due to dilution and turbulence. During the sandstorm, the concentrations of 4- and 5-ring PAHs were below their detection limits, and 6-ring PAHs were the most abundant. Under normal conditions, the concentrations of 2-, 3- and 6-ring PAHs were higher, and 4- and 5-ring PAHs were lower relative to the other sampling sites. In general, the PAH contamination was low to medium at Mount Heng. Higher LMW (low molecular weight) concentrations were primarily linked to meteorological conditions, and higher HMW (high molecular weight) concentrations primarily resulted from long-range transport. Analysis of diagnostic ratios indicated that PM2.5 PAHs had been emitted during the combustion of coal, wood or petroleum. The transport characteristics and origins of the PAHs were investigated using backwards Lagrangian particle dispersion modeling. Under normal conditions, the “footprint” retroplumes and potential source contributions of PAHs for the highest and lowest concentrations indicated that local sources had little effect. In contrast, long-range transport played a vital role in the levels of PM2.5 and PAHs in the high-altitude atmosphere. Full article
(This article belongs to the Special Issue Atmospheric Composition Observations)
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Article
CCN Properties of Organic Aerosol Collected Below and within Marine Stratocumulus Clouds near Monterey, California
Atmosphere 2015, 6(11), 1590-1607; https://doi.org/10.3390/atmos6111590 - 28 Oct 2015
Cited by 6 | Viewed by 2837
Abstract
The composition of aerosol from cloud droplets differs from that below cloud. Its implications for the Cloud Condensation Nuclei (CCN) activity are the focus of this study. Water-soluble organic matter from below cloud, and cloud droplet residuals off the coast of Monterey, California [...] Read more.
The composition of aerosol from cloud droplets differs from that below cloud. Its implications for the Cloud Condensation Nuclei (CCN) activity are the focus of this study. Water-soluble organic matter from below cloud, and cloud droplet residuals off the coast of Monterey, California were collected; offline chemical composition, CCN activity and surface tension measurements coupled with Köhler Theory Analysis are used to infer the molar volume and surfactant characteristics of organics in both samples. Based on the surface tension depression of the samples, it is unlikely that the aerosol contains strong surfactants. The activation kinetics for all samples examined are consistent with rapid (NH4)2SO4 calibration aerosol. This is consistent with our current understanding of droplet kinetics for ambient CCN. However, the carbonaceous material in cloud drop residuals is far more hygroscopic than in sub-cloud aerosol, suggestive of the impact of cloud chemistry on the hygroscopic properties of organic matter. Full article
(This article belongs to the Special Issue Atmospheric Composition Observations)
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Article
Inland Concentrations of Cl2 and ClNO2 in Southeast Texas Suggest Chlorine Chemistry Significantly Contributes to Atmospheric Reactivity
Atmosphere 2015, 6(10), 1487-1506; https://doi.org/10.3390/atmos6101487 - 14 Oct 2015
Cited by 46 | Viewed by 3591
Abstract
Measurements of molecular chlorine (Cl2), nitryl chloride (ClNO2), and dinitrogen pentoxide (N2O5) were taken as part of the DISCOVER-AQ Texas 2013 campaign with a High Resolution Time-of-Flight Chemical Ionization Mass Spectrometer (HR-ToF-CIMS) using iodide (I-) [...] Read more.
Measurements of molecular chlorine (Cl2), nitryl chloride (ClNO2), and dinitrogen pentoxide (N2O5) were taken as part of the DISCOVER-AQ Texas 2013 campaign with a High Resolution Time-of-Flight Chemical Ionization Mass Spectrometer (HR-ToF-CIMS) using iodide (I-) as a reagent ion. ClNO2 concentrations exceeding 50 ppt were regularly detected with peak concentrations typically occurring between 7:00 a.m. and 10:00 am. Hourly averaged Cl2 concentrations peaked daily between 3:00 p.m. and 4:00 p.m., with a 29-day average of 0.9 ± 0.3 (1σ) ppt. A day-time Cl2 source of up to 35 ppt∙h−1 is required to explain these observations, corresponding to a maximum chlorine radical (Cl) production rate of 70 ppt∙h−1. Modeling of the Cl2 source suggests that it can enhance daily maximum O3 and RO2concentrations by 8%–10% and 28%–50%, respectively. Modeling of observed ClNO2 assuming a well-mixed nocturnal boundary layer indicates O3 and RO2 enhancements of up to 2.1% and 38%, respectively, with a maximum impact in the early morning. These enhancements affect the formation of secondary organic aerosol and compliance with air quality standards for ozone and particulate matter. Full article
(This article belongs to the Special Issue Atmospheric Composition Observations)
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Article
Analysis of PAHs Associated with Particulate Matter PM2.5 in Two Places at the City of Cuernavaca, Morelos, México
Atmosphere 2015, 6(9), 1259-1270; https://doi.org/10.3390/atmos6091259 - 25 Aug 2015
Cited by 13 | Viewed by 2501
Abstract
This study was carried out between January and February 2013, at two sites in the city of Cuernavaca, México, using low-volume equipment. Fifteen Polycyclic aromatic hydrocarbons (PAHs), were identified by gas chromatography coupled with mass spectrometry. The total average concentration observed for PAHs [...] Read more.
This study was carried out between January and February 2013, at two sites in the city of Cuernavaca, México, using low-volume equipment. Fifteen Polycyclic aromatic hydrocarbons (PAHs), were identified by gas chromatography coupled with mass spectrometry. The total average concentration observed for PAHs was 24.0 ng·m3, with the high molecular weight compounds being the most abundant. The estimated equivalent concentration for Benzo (a) P (BaPE) was 4.05 ng·m3. Diagnostic ratios together with the principal components analysis (PCA) allowed for establishing coal burning and vehicle emissions as being the main sources of these compounds in the area. The PAHs used to calculate this index account for 51% of the 15 PAHs identified, which probably involves a risk to the exposed population. Full article
(This article belongs to the Special Issue Atmospheric Composition Observations)
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Article
Characteristics of PM10 and PM2.5 at Mount Wutai Buddhism Scenic Spot, Shanxi, China
Atmosphere 2015, 6(8), 1195-1210; https://doi.org/10.3390/atmos6081195 - 18 Aug 2015
Cited by 11 | Viewed by 3402
Abstract
A survey was conducted to effectively investigate the characteristics of airborne particulate pollutants PM10 and PM2.5 during the peak tourist season at Mount Wutai Buddhism scenic spot, Shanxi, China. Characteristics of the PM10 and PM2.5 in Wu Ye Temple [...] Read more.
A survey was conducted to effectively investigate the characteristics of airborne particulate pollutants PM10 and PM2.5 during the peak tourist season at Mount Wutai Buddhism scenic spot, Shanxi, China. Characteristics of the PM10 and PM2.5 in Wu Ye Temple (core incense burners), Manjusri Temple (a traffic hub), Yang Bai Lin Village (a residential district), and Nan Shan Temple (located in a primitive forest district), were determined. The results showed that the PM10 concentration was more than 1.01–1.14 times higher than the threshold (50 μg/m3) of World Health Organization Air Quality Guidelines (2005), and the PM2.5 concentration was 1.75–2.70 times higher than the above standard (25 μg/m3). Particle size analysis indicated that the distribution of fine particulate matter in Wu Ye Temple ranged from 0 to 3.30 μm. In other sampling points, the fine particulate was mainly distributed in the range of 0–5.90 μm. The particulates in Wu Ye Temple were mainly characterized by spherical, rod-like, and irregular soot aggregates (PM10) and spherical particles of dust (PM2.5). Manjusri Temple and Yang Bai Lin Village predominantly exhibited irregular soil mineral particulate matter (PM10), and amorphous ultrafine soot particulate matter (PM2.5). Full article
(This article belongs to the Special Issue Atmospheric Composition Observations)
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Article
Study of Black Sand Particles from Sand Dunes in Badr, Saudi Arabia Using Electron Microscopy
Atmosphere 2015, 6(8), 1175-1194; https://doi.org/10.3390/atmos6081175 - 17 Aug 2015
Cited by 2 | Viewed by 4907
Abstract
Particulate air pollution is a health concern. This study determines the microscopic make-up of different varieties of sand particles collected at a sand dune site in Badr, Saudi Arabia in 2012. Three categories of sand were studied: black sand, white sand, and volcanic [...] Read more.
Particulate air pollution is a health concern. This study determines the microscopic make-up of different varieties of sand particles collected at a sand dune site in Badr, Saudi Arabia in 2012. Three categories of sand were studied: black sand, white sand, and volcanic sand. The study used multiple high resolution electron microscopies to study the morphologies, emission source types, size, and elemental composition of the particles, and to evaluate the presence of surface “coatings or contaminants” deposited or transported by the black sand particles. White sand was comprised of natural coarse particles linked to wind-blown releases from crustal surfaces, weathering of igneous/metamorphic rock sources, and volcanic activities. Black sand particles exhibited different morphologies and microstructures (surface roughness) compared with the white sand and volcanic sand. Morphological Scanning Electron Microscopy (SEM) and Laser Scanning Microscopy (LSM) analyses revealed that the black sand contained fine and ultrafine particles (50 to 500 nm ranges) and was strongly magnetic, indicating the mineral magnetite or elemental iron. Aqueous extracts of black sands were acidic (pH = 5.0). Fe, C, O, Ti, Si, V, and S dominated the composition of black sand. Results suggest that carbon and other contaminant fine particles were produced by fossil-fuel combustion and industrial emissions in heavily industrialized areas of Haifa and Yanbu, and transported as cloud condensation nuclei to Douf Mountain. The suite of techniques used in this study has yielded an in-depth characterization of sand particles. Such information will be needed in future environmental, toxicological, epidemiological, and source apportionment studies. Full article
(This article belongs to the Special Issue Atmospheric Composition Observations)
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Article
The Impact of Selected Parameters on Visibility: First Results from a Long-Term Campaign in Warsaw, Poland
Atmosphere 2015, 6(8), 1154-1174; https://doi.org/10.3390/atmos6081154 - 12 Aug 2015
Cited by 23 | Viewed by 3227
Abstract
The aim of this study was to investigate how atmospheric air pollutants and meteorological conditions affected atmospheric visibility in the largest Polish agglomeration. The correlation analysis, principal component analysis (PCA) and generalized regression models (GRMs) were used to accomplish this objective. The meteorological [...] Read more.
The aim of this study was to investigate how atmospheric air pollutants and meteorological conditions affected atmospheric visibility in the largest Polish agglomeration. The correlation analysis, principal component analysis (PCA) and generalized regression models (GRMs) were used to accomplish this objective. The meteorological parameters (temperature, relative humidity, precipitation, wind speed and insolation) and concentrations of the air pollutants (PM10, SO2, NO2, CO and O3) were recorded in 2004–2013. The data came from the Ursynów-SGGW, MzWarszUrsynów and Okęcie monitoring stations, located in the south of Warsaw (Poland). It was shown that the PM10 concentration was the most important parameter affecting the visibility in Warsaw. The concentration, and indirectly the visibility, was mainly affected by the pollutant emission from the flat/building heating (combustion of various fuels). It changed intensively during the research period. There were also periods in which this emission type did not have a great influence on the pollutant concentrations (mainly PM10) and visibility. In such seasons, the research revealed the influence of the traffic emission and secondary aerosol formation processes on the visibility. Full article
(This article belongs to the Special Issue Atmospheric Composition Observations)
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Article
Airborne Aerosol in Situ Measurements during TCAP: A Closure Study of Total Scattering
Atmosphere 2015, 6(8), 1069-1101; https://doi.org/10.3390/atmos6081069 - 31 Jul 2015
Cited by 14 | Viewed by 4382
Abstract
We present a framework for calculating the total scattering of both non-absorbing and absorbing aerosol at ambient conditions from aircraft data. Our framework is developed emphasizing the explicit use of chemical composition data for estimating the complex refractive index (RI) of particles, and [...] Read more.
We present a framework for calculating the total scattering of both non-absorbing and absorbing aerosol at ambient conditions from aircraft data. Our framework is developed emphasizing the explicit use of chemical composition data for estimating the complex refractive index (RI) of particles, and thus obtaining improved ambient size spectra derived from Optical Particle Counter (OPC) measurements. The feasibility of our framework for improved calculations of total scattering is demonstrated using three types of data collected by the U.S. Department of Energy’s (DOE) aircraft during the Two-Column Aerosol Project (TCAP). Namely, these data types are: (1) size distributions measured by a suite of OPC’s; (2) chemical composition data measured by an Aerosol Mass Spectrometer and a Single Particle Soot Photometer; and (3) the dry total scattering coefficient measured by a integrating nephelometer and scattering enhancement factor measured with a humidification system. We demonstrate that good agreement (~10%) between the observed and calculated scattering can be obtained under ambient conditions (RH < 80%) by applying chemical composition data for the RI-based correction of the OPC-derived size spectra. We also demonstrate that ignoring the RI-based correction or using non-representative RI values can cause a substantial underestimation (~40%) or overestimation (~35%) of the calculated scattering, respectively. Full article
(This article belongs to the Special Issue Atmospheric Composition Observations)
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Article
Chemical Composition of Water Soluble Inorganic Species in Precipitation at Shihwa Basin, Korea
Atmosphere 2015, 6(6), 732-750; https://doi.org/10.3390/atmos6060732 - 25 May 2015
Cited by 28 | Viewed by 2856
Abstract
Weekly rain samples were collected in coastal areas of the Shihwa Basin (Korea) from June 2000 to November 2007. The study region includes industrial, rural, and agricultural areas. Wet precipitation was analyzed for conductivity, pH, Cl, NO3, SO [...] Read more.
Weekly rain samples were collected in coastal areas of the Shihwa Basin (Korea) from June 2000 to November 2007. The study region includes industrial, rural, and agricultural areas. Wet precipitation was analyzed for conductivity, pH, Cl, NO3, SO42, Na+, K+, Mg2+, NH4+, and Ca2+. The major components of precipitation in the Shihwa Basin were NH4+, volume-weighted mean (VWM) of 44.6 µeq∙L−1, representing 43% of all cations, and SO42, with the highest concentration among the anions (55%) at all stations. The pH ranged from 3.4 to 7.7 with a VMM of 4.84. H+ was weakly but positively correlated with SO42 (r = 0.39, p < 0.001) and NO3 (r = 0.38, p < 0.001). About 66% of the acidity was neutralized by NH4+ and Ca2+. The Cl/Na+ ratio of the precipitation was 37% higher than seawater Cl/Na+. The high SO42/NO3 ratio of 2.3 is attributed to the influence of the surrounding industrial sources. Results from positive matrix factorization showed that the precipitation chemistry in Shihwa Basin was influenced by secondary nitrate and sulfate (41% ± 1.1%), followed by sea salt and Asian dust, contributing 23% ± 3.9% and 17% ± 0.2%, respectively. In this study, the annual trends of SO42 and NO3 (p < 0.05) increased, different from the trends in some locations, due to the influence of the expanding power generating facilities located in the upwind area. The increasing trends of SO42 and NO3 in the study region have important implications for reducing air pollution in accordance with national energy policy. Full article
(This article belongs to the Special Issue Atmospheric Composition Observations)
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Article
The Possible Role of Penning Ionization Processes in Planetary Atmospheres
Atmosphere 2015, 6(3), 299-317; https://doi.org/10.3390/atmos6030299 - 11 Mar 2015
Cited by 42 | Viewed by 3216
Abstract
In this paper we suggest Penning ionization as an important route of formation for ionic species in upper planetary atmospheres. Our goal is to provide relevant tools to researchers working on kinetic models of atmospheric interest, in order to include Penning ionizations in [...] Read more.
In this paper we suggest Penning ionization as an important route of formation for ionic species in upper planetary atmospheres. Our goal is to provide relevant tools to researchers working on kinetic models of atmospheric interest, in order to include Penning ionizations in their calculations as fast processes promoting reactions that cannot be neglected. Ions are extremely important for the transmission of radio and satellite signals, and they govern the chemistry of planetary ionospheres. Molecular ions have also been detected in comet tails. In this paper recent experimental results concerning production of simple ionic species of atmospheric interest are presented and discussed. Such results concern the formation of free ions in collisional ionization of H2O, H2S, and NH3 induced by highly excited species (Penning ionization) as metastable noble gas atoms. The effect of Penning ionization still has not been considered in the modeling of terrestrial and extraterrestrial objects so far, even, though metastable helium is formed by radiative recombination of He+ ions with electrons. Because helium is the second most abundant element of the universe, Penning ionization of atomic or molecular species by He*(23S1) is plausibly an active route of ionization in relatively dense environments exposed to cosmic rays. Full article
(This article belongs to the Special Issue Atmospheric Composition Observations)
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