Special Issue "Atmospheric Aqueous-Phase Chemistry"

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

Deadline for manuscript submissions: 29 February 2020.

Special Issue Editor

Dr. Irena Grgić
E-Mail Website1 Website2
Guest Editor
Department of Analytical Chemistry, National Institute of Chemistry, Ljubljana, Slovenia
Interests: Multiphase atmospheric chemistry; formation of acidic components in tropospheric aqueous phase; secondary organic aerosol (SOA); kinetic & mechanistic studies of atmospheric aqueous-phase reactions; aerosol measurements (size-segregated sampling & nanoparticles); physico-chemical characterization of aerosols; analytical methods for environmentally important constituents

Special Issue Information

Dear Colleagues,

Liquid water in cloud and fog droplets, and in moist aerosol particles, is ubiquitous in the atmosphere. Dissolved species from the soluble aerosol fraction as well as soluble trace gases undergo chemical reactions in the aqueous phase via different mechanisms, usually yielding different products from those in the gas phase. In addition to their different reactivity, the chemical species’ solubility determines their fate in the atmosphere, i.e., their involvement in gas-phase or aqueous-phase chemistry.

Numerous studies confirm that the predominant fraction of atmospheric sulfate formed through the multiphase oxidation of sulfur (IV) from fossil fuel combustion takes place in cloud droplets. Yet, there are still unresolved questions concerning sulfate formation under extremely polluted conditions such as, e.g., found in China.

Recently, it has been recognized that secondary organic aerosol (SOA) mass may also be formed via chemical reactions, in cloud and fog droplets and moist aerosol particles. During atmospheric processing, the primary emitted organic pollutants become more oxidized, less volatile, and more water-soluble. Consequently, within the pollutants’ lifetime in the atmosphere, aqueous-phase chemistry becomes more and more important for their aging.

In this Special Issue, we welcome manuscripts on all aspects of atmospheric aqueous-phase chemistry associated with

  1. kinetic and mechanistic studies of organic and inorganic systems,
  2. the unraveling of chemical mechanisms leading to the identification of products in the atmospheric liquid water,
  3. and the use of predictive modeling providing insights on the mechanisms unraveled.

Dr. Irena Grgić
Guest Editor

Manuscript Submission Information

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Keywords

  • atmospheric aqueous-phase chemistry
  • multiphase chemistry
  • organic pollutants
  • inorganic species
  • kinetic studies
  • mechanistic studies
  • chemical mechanisms
  • modeling

Published Papers (7 papers)

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Research

Open AccessArticle
On Aerosol Liquid Water and Sulfate Associations: The Potential for Fine Particulate Matter Biases
Atmosphere 2020, 11(2), 194; https://doi.org/10.3390/atmos11020194 - 12 Feb 2020
Abstract
In humid locations of the Eastern U.S., sulfate is a surrogate for aerosol liquid water (ALW), a poorly measured particle constituent. Regional and seasonal variation in ALW–sulfate relationships offers a potential explanation to reconcile epidemiology and toxicology studies regarding particulate sulfur and health [...] Read more.
In humid locations of the Eastern U.S., sulfate is a surrogate for aerosol liquid water (ALW), a poorly measured particle constituent. Regional and seasonal variation in ALW–sulfate relationships offers a potential explanation to reconcile epidemiology and toxicology studies regarding particulate sulfur and health endpoints. ALW facilitates transfer of polar species from the gas phase to the particle phase and affects particle pH and metal oxidation state. Though abundant and a potential indicator of adverse health endpoints, ALW is largely removed in most particulate matter measurement techniques, including in routine particulate matter (PM2.5) networks that use federal reference method (FRM) monitors, which are used in epidemiology studies. We find that in 2004, a typical year in the available record, ambient ALW mass is removed during sampling and filter equilibration to standard laboratory conditions at most (94%) sites, up to 85% of the ambient water mass. The removal of ALW can induce the evaporation of other semi-volatile compounds present in PM2.5, such as ammonium nitrate and numerous organics. This produces an artifact in the PM mass measurements that is, importantly, not uniform in space or time. This suggests that PM2.5 epidemiology studies that exclude ALW are biased. This work provides a plausible explanation to resolve multi-decade discrepancies regarding ambient sulfate and health impacts in some epidemiological and toxicological studies. Full article
(This article belongs to the Special Issue Atmospheric Aqueous-Phase Chemistry)
Open AccessArticle
Aqueous-Phase Production of Secondary Organic Aerosols from Oxidation of Dibenzothiophene (DBT)
Atmosphere 2020, 11(2), 151; https://doi.org/10.3390/atmos11020151 - 30 Jan 2020
Abstract
Intermediate-volatility organic compounds (IVOCs) have been recognized as an important contributor to the secondary organic aerosol (SOA) formation via gas-phase reactions. However, it is unclear whether or not IVOCs-SOA can be produced in the aqueous phase. This work investigated aqueous oxidation of one [...] Read more.
Intermediate-volatility organic compounds (IVOCs) have been recognized as an important contributor to the secondary organic aerosol (SOA) formation via gas-phase reactions. However, it is unclear whether or not IVOCs-SOA can be produced in the aqueous phase. This work investigated aqueous oxidation of one model compound of IVOCs, dibenzothiophene (DBT). Results show that DBT can be degraded by both hydroxyl radical and the triplet excited states of organic light chromophores (3C*). Aqueous dark oxidation of DBT was also possible. SOA yields of 32% and 15% were found for hydroxyl radical (OH)-mediated photo-oxidation and dark oxidation, respectively. A continuous and significant increase of oxidation degree of SOA was observed during OH photo-oxidation, but not during the dark oxidation. Factor analyses revealed that there was a persistent production of highly oxygenated compounds from the less oxygenated species. OH-initiated photochemical reactions can also produce species with a relatively large light-absorbing ability, while such photo-enhancement due to direct light irradiation and 3C*-initiated oxidation could occur, but is much less important. In the future, studies on the second-order rate constants, molecular characterization of the oxidation products from this and other IVOCs precursors are needed to better understand the role of this reaction pathway in SOA budget, air quality and climate change. Full article
(This article belongs to the Special Issue Atmospheric Aqueous-Phase Chemistry)
Open AccessArticle
Physico-Chemical Characterization of an Urban Rainwater (Zagreb, Croatia)
Atmosphere 2020, 11(2), 144; https://doi.org/10.3390/atmos11020144 - 28 Jan 2020
Abstract
The characterization of organic matter (OM) and trace elements (TEs) was conducted in bulk precipitation samples collected in an urban area of Croatia (Zagreb center), from January 2009 to October 2011 (N = 31). Characterization of OM was performed by measurement of dissolved [...] Read more.
The characterization of organic matter (OM) and trace elements (TEs) was conducted in bulk precipitation samples collected in an urban area of Croatia (Zagreb center), from January 2009 to October 2011 (N = 31). Characterization of OM was performed by measurement of dissolved (DOC) and particulate forms of organic carbon (POC), as well as surface-active substances, copper complexing capacity and reduced sulfur species which were determined electrochemically. Concentrations of TEs (Al, Fe, Zn, Cr, Ba, Mn, Cu, Sr, Ti, Pb, V, Ni, Rb, Sb, As, Sn, Se, Co, Cd, Mo) were analyzed by HR ICP-MS. The most important outcome of this study is confirmed relatively low concentrations of DOC (0.69–4.86 mgC L−1) and TEs. Daily fluxes of Zn, Pb, Ni, As, and Cd were two to three times lower than that of those reported for an urban industrial site in Europe. Additionally, this study shows that the value and reactivity of rainwater DOC has not considerably changed if compared with the results from the 1998–1999 study (0.78–4.39 mgC L−1). High traffic density and thermal power plants are assumed to be the main local sources of pollutants in Zagreb. Using Al as a reference element, it was found that Cd, Sb, and Cu were associated with anthropogenic sources. The solubility of Sr, Zn, Cd, Ni, Cr, As, and Rb was higher than 70%. Another critical characteristic of precipitation composition is episodic variation in POC concentration because of Saharan dust transport. Obtained data can be valuable for environmental quality assessment, as well as for insight into atmospheric deposition processes. Full article
(This article belongs to the Special Issue Atmospheric Aqueous-Phase Chemistry)
Open AccessArticle
Aqueous-Phase Brown Carbon Formation from Aromatic Precursors under Sunlight Conditions
Atmosphere 2020, 11(2), 131; https://doi.org/10.3390/atmos11020131 - 24 Jan 2020
Abstract
At present, there are still numerous unresolved questions concerning the mechanisms of light-absorbing organic aerosol (brown carbon, BrC) formation in the atmosphere. Moreover, there is growing evidence that chemical processes in the atmospheric aqueous phase can be important. In this work, we investigate [...] Read more.
At present, there are still numerous unresolved questions concerning the mechanisms of light-absorbing organic aerosol (brown carbon, BrC) formation in the atmosphere. Moreover, there is growing evidence that chemical processes in the atmospheric aqueous phase can be important. In this work, we investigate the aqueous-phase formation of BrC from 3-methylcatechol (3MC) under simulated sunlight conditions. The influence of different HNO2/NO2 concentrations on the kinetics of 3MC degradation and BrC formation was investigated. Under illumination, the degradation of 3MC is faster (k2nd(global) = 0.075 M−1·s−1) in comparison to its degradation in the dark under the same solution conditions (k2nd = 0.032 M−1·s−1). On the other hand, the yield of the main two products of the dark reaction (3-methyl-5-nitrocatechol, 3M5NC, and 3-methyl-4-nitrocatechol, 3M4NC) is low, suggesting different degradation pathways of 3MC in the sunlight. Besides the known primary reaction products with distinct absorption at 350 nm, second-generation products responsible for the absorption above 400 nm (e.g., hydroxy-3-methyl-5-nitrocatechol, 3M5NC-OH, and the oxidative cleavage products of 3M4NC) were also confirmed in the reaction mixture. The characteristic mass absorption coefficient (MAC) values were found to increase with the increase of NO2/3MC concentration ratio (at the concentration ratio of 50, MAC is greater than 4 m2·g−1 at 350 nm) and decrease with the increasing wavelength, which is characteristic for BrC. Yet, in the dark, roughly 50% more BrC is produced at comparable solution conditions (in terms of MAC values). Our findings reveal that the aqueous-phase processing of 3MC in the presence of HNO2/NO2, both under the sunlight and in the dark, may significantly contribute to secondary organic aerosol (SOA) light absorption. Full article
(This article belongs to the Special Issue Atmospheric Aqueous-Phase Chemistry)
Open AccessArticle
Aqueous Reactions of Sulfate Radical-Anions with Nitrophenols in Atmospheric Context
Atmosphere 2019, 10(12), 795; https://doi.org/10.3390/atmos10120795 - 09 Dec 2019
Abstract
Nitrophenols, hazardous environmental pollutants, react promptly with atmospheric oxidants such as hydroxyl or nitrate radicals. This work aimed to estimate how fast nitrophenols are removed from the atmosphere by the aqueous-phase reactions with sulfate radical-anions. The reversed-rates method was applied to determine the [...] Read more.
Nitrophenols, hazardous environmental pollutants, react promptly with atmospheric oxidants such as hydroxyl or nitrate radicals. This work aimed to estimate how fast nitrophenols are removed from the atmosphere by the aqueous-phase reactions with sulfate radical-anions. The reversed-rates method was applied to determine the relative rate constants for reactions of 2-nitrophenol, 3-nitrophenol, 4-nitrophenol, 2,4-dinitrophenol, and 2,4,6-trinitrophenol with sulfate radical-anions generated by the autoxidation of sodium sulfite catalyzed by iron(III) cations at ~298 K. The constants determined were: 9.08 × 108, 1.72 × 109, 6.60 × 108, 2.86 × 108, and 7.10 × 107 M−1 s−1, respectively. These values correlated linearly with the sums of Brown substituent coefficients and with the relative strength of the O–H bond of the respective nitrophenols. Rough estimation showed that the gas-phase reactions of 2-nitrophenol with hydroxyl or nitrate radicals dominated over the aqueous-phase reaction with sulfate radical-anions in deliquescent aerosol and haze water. In clouds, rains, and haze water, the aqueous-phase reaction of 2-nitrophenol with sulfate radical-anions dominated, provided the concentration of the radical-anions was not smaller than that of the hydroxyl or nitrate radicals. The results presented may be also interesting for designers of advanced oxidation processes for the removal of nitrophenol. Full article
(This article belongs to the Special Issue Atmospheric Aqueous-Phase Chemistry)
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Open AccessArticle
Electrochemical Evidence of non-Volatile Reduced Sulfur Species in Water-Soluble Fraction of Fine Marine Aerosols
Atmosphere 2019, 10(11), 674; https://doi.org/10.3390/atmos10110674 - 01 Nov 2019
Abstract
The traditional voltammetric method at the mercury electrode, and an acidification step developed for the determination of reduced sulfur species (RSS) in natural waters, was for the first time used for the quantification of RSS in the water-soluble fraction of fine marine aerosols [...] Read more.
The traditional voltammetric method at the mercury electrode, and an acidification step developed for the determination of reduced sulfur species (RSS) in natural waters, was for the first time used for the quantification of RSS in the water-soluble fraction of fine marine aerosols collected at the Middle Adriatic location (Rogoznica Lake). The evidence of two types of non-volatile RSS that have different interaction with the Hg electrode was confirmed: mercapto-type which complexes Hg as RS–Hg and sulfide/S0-like compounds which deposits HgS. The analytical protocol that was used for RSS determination in aerosol samples is based on separate voltammetric studies of a methyl 3-mercaptopropionate (3-MPA) as a representative of mercapto-type compounds and sulfide as a representative of inorganic RSS. Our preliminary study indicates the presence of mainly RS–Hg compounds in spring samples, ranging from 2.60–15.40 ng m−3, while both, the mercapto-type (0.48–2.23 ng m−3) and sulfide and/or S0-like compounds (0.02–0.26 ng m−3) were detected in early autumn samples. More expressed and defined RS–Hg peaks recorded in the spring potentially indicate their association with biological activity in the area. Those samples were also characterized by a higher water-soluble organic carbon content and a more abundant surface-active fraction, pointing to enhanced solubility and stabilization of RSS in the aqueous atmospheric phase. Full article
(This article belongs to the Special Issue Atmospheric Aqueous-Phase Chemistry)
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Open AccessArticle
Impact of Aerosol-Cloud Cycling on Aqueous Secondary Organic Aerosol Formation
Atmosphere 2019, 10(11), 666; https://doi.org/10.3390/atmos10110666 - 31 Oct 2019
Abstract
Chemical processing of organic material in aqueous atmospheric aerosols and cloudwater is known to form secondary organic aerosols (SOA), although the extent to which each of these processes contributes to total aerosol mass is unclear. In this study, we use GAMMA 5.0, a [...] Read more.
Chemical processing of organic material in aqueous atmospheric aerosols and cloudwater is known to form secondary organic aerosols (SOA), although the extent to which each of these processes contributes to total aerosol mass is unclear. In this study, we use GAMMA 5.0, a photochemical box model with coupled gas and aqueous-phase chemistry, to consider the impact of aqueous organic reactions in both aqueous aerosols and clouds on isoprene epoxydiol (IEPOX) SOA over a range of pH for both aqueous phases, including cycling between cloud and aerosol within a single simulation. Low pH aqueous aerosol, in the absence of organic coatings or other morphology which may limit uptake of IEPOX, is found to be an efficient source of IEPOX SOA, consistent with previous work. Cloudwater at pH 4 or lower is also found to be a potentially significant source of IEPOX SOA. This phenomenon is primarily attributed to the relatively high uptake of IEPOX to clouds as a result of higher water content in clouds as compared with aerosol. For more acidic cloudwater, the aqueous organic material is comprised primarily of IEPOX SOA and lower-volatility organic acids. Both cloudwater pH and the time of day or sequence of aerosol-to-cloud or cloud-to-aerosol transitions impacted final aqueous SOA mass and composition in the simulations. The potential significance of cloud processing as a contributor to IEPOX SOA production could account for discrepancies between predicted IEPOX SOA mass from atmospheric models and measured ambient IEPOX SOA mass, or observations of IEPOX SOA in locations where mass transfer limitations are expected in aerosol particles. Full article
(This article belongs to the Special Issue Atmospheric Aqueous-Phase Chemistry)
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