The airborne transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been identified as a potential pandemic challenge, especially in poorly ventilated indoor environments, ...such as certain hospitals, schools, public buildings, and transports. The impacts of meteorological parameters (temperature and humidity) and physical property (droplet size) on the airborne transmission of coronavirus in indoor settings have been previously investigated. However, the impacts of chemical properties of viral droplets and aerosol particles (i.e., chemical composition and acidity (pH)) on viability and indoor transmission of coronavirus remain largely unknown. Recent studies suggest high organic content (proteins) in viral droplets and aerosol particles supports prolonged survival of the virus by forming a glassy gel-type structure that restricts the virus inactivation process under low relative humidity (RH). In addition, the virus survival was found at neutral pH, and inactivation was observed to be best at low (<5) and high pH (>10) values (enveloped bacteriophage Phi6). Due to limited available information, this article illustrates an urgent need to research the impact of chemical properties of exhaled viral particles on virus viability. This will improve our fundamental understanding of indoor viral airborne transmission mechanisms.
The chemical composition of ambient organic aerosols was analyzed using complementary mass spectrometric techniques during a field study in central Europe in July 2014 (Fichtelgebirge – Biogenic ...Emission and Aerosol Chemistry, F-BEACh 2014). Among several common biogenic secondary organic aerosol (BSOA) marker compounds, 93 acidic oxygenated hydrocarbons were detected with elevated abundances and were thus attributed to be characteristic for the organic aerosol mass at the site. Monoterpene measurements exhibited median mixing ratios of 1.6 and 0.8 ppbV for in and above canopy levels respectively. Nonetheless, concentrations for early-generation oxidation products were rather low, e.g., pinic acid (c = 4.7 (±2.5) ng m−3). In contrast, high concentrations were found for later-generation photooxidation products such as 3-methyl-1,2,3-butanetricarboxylic acid (MBTCA, c = 13.8 (±9.0) ng m−3) and 3-carboxyheptanedioic acid (c = 10.2 (±6.6) ng m−3), suggesting that aged aerosol masses were present during the campaign period. In agreement, HYSPLIT trajectory calculations indicate that most of the arriving air masses traveled long distances (> 1500 km) over land with high solar radiation. In addition, around 47 % of the detected compounds from filter sample analysis contained sulfur, confirming a rather high anthropogenic impact on biogenic emissions and their oxidation processes. Among the sulfur-containing compounds, several organosulfates, nitrooxy organosulfates, and highly oxidized organosulfates (HOOS) were tentatively identified by high-resolution mass spectrometry. Correlations among HOOS, sulfate, and highly oxidized multifunctional organic compounds (HOMs) support the hypothesis of previous studies that HOOS are formed by reactions of gas-phase HOMs with particulate sulfate. Moreover, periods with high relative humidity indicate that aqueous-phase chemistry might play a major role in HOOS production. However, for dryer periods, coinciding signals for HOOS and gas-phase peroxyradicals (RO2 ) were observed, suggesting RO2 to be involved in HOOS formation.
Despite the huge extent of the ocean’s surface, until now relatively little attention has been paid to the sea surface microlayer (SML) as the ultimate interface where heat, momentum and mass ...exchange between the ocean and the atmosphere takes place. Via the SML, large-scale environmental changes in the ocean such as warming, acidification, deoxygenation and eutrophication potentially influence cloud formation, precipitation and the global radiation balance. Due to the deep connectivity between biological, chemical and physical processes, studies of the SML may reveal multiple sensitivities to global and regional changes. Understanding the processes at the ocean’s surface, in particular involving the SML as an important and determinant interface, could therefore provide an essential contribution to the reduction of uncertainties regarding ocean-climate feedbacks. This review identifies gaps in our current knowledge of the SML and highlights a need to develop a holistic and mechanistic understanding of the diverse biological, chemical and physical processes occurring at the ocean-atmosphere interface. We advocate the development of strong interdisciplinary expertise and collaboration in order to bridge between ocean and atmospheric sciences. Although this will pose significant methodological challenges, such an initiative would represent a new role model for interdisciplinary research in Earth System sciences.
An improvement is made to a method for the quantification of SOA-bound peroxides. The procedure is based on an iodometric-spectrophotometric method that has been commonly used for the determination ...of peroxides in a wide range of biological and environmental samples. The improved method was applied to determine the peroxide content of laboratory-generated SOA from α-pinene ozonolysis. Besides main improvements for the detection conditions, the use of more environmentally sound solvents is considered instead of carcinogenic solvents. In addition to the improved method for peroxide determination, the present study provides evidence for artefact formation caused by ultrasonic agitation for the extraction of organic compounds in SOA filter samples. The concentration of SOA-bound peroxides in the extracts from ultrasonic agitation were up to three times higher than those from a laboratory orbital shaker under the same extraction conditions, indicating peroxide formation caused by acoustic cavitation during extraction. In contrast, pinic acid, terebic acid and terpenylic acid showed significantly lower concentrations in the sample extract prepared using ultrasonic agitation, indicating that these compounds react with OH radicals that are formed from acoustic cavitation. Great care should be taken when extracting SOA samples and the use of ultrasound should be avoided.
Glyoxal and methylglyoxal, the two smallest yet most abundant dicarbonyls, play vital roles in forming secondary organic aerosols (SOA) in the ambient air. The direct sources for glyoxal and ...methylglyoxal from vehicles are still unclear because of only a few investigations in the USA. Here we carried out tests in the Zhujiang tunnel in urban Guangzhou in south China to obtain emission factors (EFs) of glyoxal and methylglyoxal for on-road vehicles. Measured EFs for glyoxal and methylglyoxal averaged 1.18 ± 0.43 and 0.52 ± 0.26 mg km−1 veh−1, and were about 6.6 and 2.3 times those measured in the Tuscarora Mountain Tunnel in 1999 (Grosjean et al., 2001), respectively. Multiple linear regressions further resolved glyoxal EFs of 1.64 ± 1.03, 0.10 ± 3.49 and 0.58 ± 2.37 mg km−1 and methylglyoxal EFs of 0.17 ± 0.33, 1.68 ± 1.20 and 0.70 ± 0.66 mg km−1, respectively, for gasoline, diesel and liquefied petroleum gas (LPG) vehicles. The fuel-based EFs for glyoxal and methylglyoxal were estimated to be 28.1 and 2.9 mg kg−1 for gasoline vehicles, and 1.5 and 26.3 mg kg−1 for diesel vehicles, respectively. Based on available SOA yields, SOA formed from vehicle-emitted glyoxal and methylglyoxal could attain 25–50% of that formed from vehicle-emitted toluene. With the EFs from this study, the vehicle emission of the two dicarbonyls in China and in the world were roughly estimated. Either the CO-tracer-based or the fuel-based global estimates are below 0.1 Tg a−1 and therefore vehicle emission could be negligible in their global total sources, yet they might play vital roles in urban areas in forming SOA, particularly in the early chemical evolution of vehicle exhausts in the ambient.
•Road vehicle emission factors for glyoxal and methylglyoxal were obtained by tunnel tests.•Vehicle glyoxal and methylglyoxal EFs in China were compared with those in the US.•Mileage-based and fuel-based EFs were resolved by multiple linear regressions.•Vehicle emissions of glyoxal and methylglyoxal in China and in the world were estimated.
Alternative pathway for atmospheric particles growth Monge, Maria Eugenia; Rosenørn, Thomas; Favez, Olivier ...
Proceedings of the National Academy of Sciences - PNAS,
05/2012, Letnik:
109, Številka:
18
Journal Article
Recenzirano
Odprti dostop
Credible climate change predictions require reliable fundamental scientific knowledge of the underlying processes. Despite extensive observational data accumulated to date, atmospheric aerosols still ...pose key uncertainties in the understanding of Earth’s radiative balance due to direct interaction with radiation and because they modify clouds’ properties. Specifically, major gaps exist in the understanding of the physicochemical pathways that lead to aerosol growth in the atmosphere and to changes in their properties while in the atmosphere. Traditionally, the driving forces for particle growth are attributed to condensation of low vapor pressure species following atmospheric oxidation of volatile compounds by gaseous oxidants. The current study presents experimental evidence of an unaccounted-for new photoinduced pathway for particle growth. We show that heterogeneous reactions activated by light can lead to fast uptake of noncondensable Volatile Organic Compounds (VOCs) at the surface of particles when only traces of a photosensitizer are present in the seed aerosol. Under such conditions, size and mass increase; changes in the chemical composition of the aerosol are also observed upon exposure to volatile organic compounds such as terpenes and near-UV irradiation. Experimentally determined growth rate values match field observations, suggesting that this photochemical process can provide a new, unaccounted-for pathway for atmospheric particle growth and should be considered by models.
The influence of aerosols, both natural and
anthropogenic, remains a major area of uncertainty when predicting the
properties and the behaviours of clouds and their influence on climate. In
an ...attempt to better understand the microphysical properties of cloud
droplets, the simultaneous variations in aerosol microphysics and their
potential interactions during cloud life cycles in the North China Plain, an
intensive observation took place from 17 June to 30 July 2018 at the
summit of Mt. Tai. Cloud microphysical parameters were monitored
simultaneously with number concentrations of cloud condensation nuclei
(NCCN) at different supersaturations, PM2.5 mass concentrations,
particle size distributions and meteorological parameters. Number
concentrations of cloud droplets (NC), liquid water content (LWC) and
effective radius of cloud droplets (reff) show large variations among 40
cloud events observed during the campaign. The low values of reff and
LWC observed at Mt. Tai are comparable with urban fog. Clouds on clean days
are more susceptible to the change in concentrations of particle number
(NP), while clouds formed on polluted days might be more sensitive to
meteorological parameters, such as updraft velocity and cloud base height.
Through studying the size distributions of aerosol particles and cloud
droplets, we find that particles larger than 150 nm play important roles in
forming cloud droplets with the size of 5–10 µm. In general, LWC
consistently varies with reff. As NC increases, reff changes
from a trimodal distribution to a unimodal distribution and shifts to
smaller size mode. By assuming a constant cloud thickness and ignoring any
lifetime effects, increase in NC and decrease in reff would increase
cloud albedo, which may induce a cooling effect on the local climate system.
Our results contribute valuable information to enhance the understanding of
cloud and aerosol properties, along with their potential interactions on the
North China plain.
Secondary organic aerosol (SOA) formation from the gas phase ozonolysis of limonene and the influence of particle acidity were investigated in a series of indoor aerosol chamber experiments. The ...particle acidity was adjusted in three stages using Na
2SO
4 (neutral), (NH
4)
2SO
4/H
2SO
4 (acidic) and H
2SO
4 (strongly acidic) seed particles. Detected low molecular weight carboxylic acids
(
M
w
<
300
)
were found to account only for a smaller fraction of produced SOA mass at all particle acidities. Although SOA components with molecular weights between 300 and 900 were detected regardless of the seed particle acidity, the intensities of these compounds were much higher for acidic seed particle experiments. Compounds with mass to charge ratios
(
m
/
z
)
281, 465 and 481 were only detected in the presence of sulfuric acid.
MS
n
and TOFMS analyses showed a strong fragment of
m
/
z
97 and elemental compositions of
C
10
H
17
O
7
S
-
,
C
20
H
33
O
10
S
-
and
C
20
H
33
O
11
S
-
suggesting organic sulfate structures, possibly formed by a heterogeneous acid catalyzed reaction of limonene oxidation products and sulfuric acid in the particle phase. The high intensities of organic sulfate esters suggest that these compounds contribute at least as much as first and second generation oxidation products to the SOA mass.
An analytical method coupled to multivariate statistical analysis was developed based on transmission-mode direct analysis in real-time quadrupole time-of-flight mass spectrometry (TM-DART-QTOF-MS) ...to interrogate lipophilic compounds in seawater samples without the need for desalinization. An untargeted metabolomics approach is addressed here as
seaomics and was successfully implemented to discriminate the sea surface microlayer (SML) from the underlying water (ULW) samples (n=22, 10 paired samples) collected during a field campaign at the Cabo Verde islands during
September–October 2017. A panel of 11 ionic species detected in all samples allowed sample class discrimination by means of supervised multivariate statistical models. Tentative identification of the species enriched in the SML samples suggests that fatty alcohols, halogenated compounds, and oxygenated
boron-containing organic compounds are available at the surface for
air–water transfer processes. A subset of SML samples (n=5) were subjected
to on-site experiments during the campaign by using a lab-to-field approach
to test their secondary organic aerosol (SOA) formation potency. The results
from these experiments and the analytical seaomics strategy provide a proof
of a concept that can be used for an approach to identifying organic molecules involved in aerosol formation processes at the air–water interface.
Daily concentrations of inorganic and organic compounds associated with PM_(10), i.e., atmospheric particulate matter with aerodynamic diameter of less than 10 μm, was determined at the south ...Mediterranean coastal area located in Bou Ismaïl, 40 km west of the Algiers city area in Algeria. From September 2011 to January 2012, chemical characterization of aerosol particles comprising water-soluble ions (WSI), trace metals, carbonaceous aerosols, the anhydrosugars levoglucosan and arabitol, dicarboxylic acids, and semi-volatile organic compounds (SVOC), i.e., alkanes, PAHs, and hopanes, was carried out by using a variety of analytical techniques. Overall, the concentrations of selected ionic species were similar to those reported at other Mediterranean sites, ranging from 3.62 μg m-(^3) to 5.20 μg m^(-3) for the monthly total WSI. Sulfate was the most abundant ion. The total concentrations of semi-volatile organic compounds (SVOC) recorded in Bou Ismaïl ranged from 7.06 to 58.8 ng m^(-3) for n-alkanes, from 2.44 to 35.3 ng m^(-3) for polycyclic aromatic hydrocarbons (PAHs), from 0.14 to 1 ng m^(-3) for hopanes, and from 0.67 to 13.2 ng m^(-3) for n-alkan-2-one. In order to reconcile species concentrations and their emission sources, sampling days were grouped into two categories according to air mass origin. In the first group, the aerosol particles were mainly of a marine origin, while those of the second group originated in the dust sector. A source analysis of total contents organic compounds (PAHs, alkanes, hopanes, and alkanones) and individual inorganic compounds by spearman rank correlation illustrated that the principal sources consisted of sea salt, secondary aerosol, and biomass burning. Additionally, PM_(10) constituent diagnostic ratios and the carbon preference index (CPI) for n-alkanes indicated the importance of anthropogenic emissions.
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