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1.
Environ Sci Technol ; 54(7): 3767-3782, 2020 04 07.
Artigo em Inglês | MEDLINE | ID: mdl-32157872

RESUMO

Organosulfates (OSs), also referred to as organic sulfate esters, are well-known and ubiquitous constituents of atmospheric aerosol particles. Commonly, they are assumed to form upon mixing of air masses of biogenic and anthropogenic origin, that is, through multiphase reactions between organic compounds and acidic sulfate particles. However, in contrast to this simplified picture, recent studies suggest that OSs may also originate from purely anthropogenic precursors or even directly from biomass and fossil fuel burning. Moreover, besides classical OS formation pathways, several alternative routes have been discovered, suggesting that OS formation possibly occurs through a wider variety of formation mechanisms in the atmosphere than initially expected. During the past decade, OSs have reached a constantly growing attention within the atmospheric science community with evermore studies reporting on large numbers of OS species in ambient aerosol. Nonetheless, estimates on OS concentrations and implications on atmospheric physicochemical processes are still connected to large uncertainties, calling for combined field, laboratory, and modeling studies. In this Critical Review, we summarize the current state of knowledge in atmospheric OS research, discuss unresolved questions, and outline future research needs, also in view of reductions of anthropogenic sulfur dioxide (SO2) emissions. Particularly, we focus on (1) field measurements of OSs and measurement techniques, (2) formation pathways of OSs and their atmospheric relevance, (3) transformation, reactivity, and fate of OSs in atmospheric particles, and (4) modeling efforts of OS formation and their global abundance.


Assuntos
Atmosfera , Dióxido de Enxofre , Aerossóis , Compostos Orgânicos , Sulfatos
2.
Nat Commun ; 9(1): 3222, 2018 08 08.
Artigo em Inglês | MEDLINE | ID: mdl-30089803

RESUMO

The authors became aware of a mistake in the data displayed in the original version of the paper. Specifically, for the calculation of the total emission estimates (i.e., from an average molecular weight and summed laboratory production values for all VOCs), the authors mistakenly added seasonal estimates to the annual estimates because both values are stored in the same variable of the code. Eventually, this additional sum resulted in a doubling of emission estimates.As a result of this, the following changes have been made to the originally published version of this Article:The fifth sentence of the abstract originally read "Our results indicate global emissions of 46.4-184 Tg C yr-1 of organic vapors from the oceans into the marine atmosphere and a potential contribution to organic aerosol mass of more than 60% over the remote ocean." In the corrected version "46.4-184 Tg C yr-1" is replaced by "23.2-91.9 Tg C yr-1"The seventh sentence of the second paragraph of the Introduction originally read "We infer global emissions of 65.0-257 Tg yr-1 (46.4-184 Tg C yr-1) of organic vapors from the oceans into the marine atmosphere." In the corrected version, "65.0-257 Tg yr-1 (46.4-184 Tg C yr-1)" is replaced by "32.5-129 Tg C yr-1 (23.2-91.9 Tg C yr-1)".The last sentence of the first paragraph of the Results subheading "Marine isoprene emissions from interfacial photochemistry" originally read "In the same way, we infer total emissions of organic vapors from abiotic interfacial photochemistry in the range of 65.0-257 Tg yr-1 (46.4-184 Tg C yr-1), hence, contributing significantly to marine VOC emissions." In the corrected version, "65.0-257 Tg yr-1 (46.4-184 Tg C yr-1)" is replaced by "32.5-129 Tg C yr-1 (23.2-91.9 Tg C yr-1)".This has been corrected in both the PDF and the HTML versions of the Article. While the new estimates are lower than previously reported this error does not affect the original discussion or conclusions of the Article. The authors apologize for the confusion caused by this mistake.

3.
Nat Commun ; 9(1): 2101, 2018 05 29.
Artigo em Inglês | MEDLINE | ID: mdl-29844311

RESUMO

The surface of the oceans acts as a global sink and source for trace gases and aerosol particles. Recent studies suggest that photochemical reactions at this air/water interface produce organic vapors, enhancing particle formation in the atmosphere. However, current model calculations neglect this abiotic source of reactive compounds and account only for biological emissions. Here we show that interfacial photochemistry serves as a major abiotic source of volatile organic compounds (VOCs) on a global scale, capable to compete with emissions from marine biology. Our results indicate global emissions of 46.4-184 Tg C yr-1 of organic vapors from the oceans into the marine atmosphere and a potential contribution to organic aerosol mass of more than 60% over the remote ocean. Moreover, we provide global distributions of VOC formation potentials, which can be used as simple tools for field studies to estimate photochemical VOC emissions depending on location and season.

5.
Faraday Discuss ; 200: 59-74, 2017 08 24.
Artigo em Inglês | MEDLINE | ID: mdl-28598469

RESUMO

Films of biogenic compounds exposed to the atmosphere are ubiquitously found on the surfaces of cloud droplets, aerosol particles, buildings, plants, soils and the ocean. These air/water interfaces host countless amphiphilic compounds concentrated there with respect to in bulk water, leading to a unique chemical environment. Here, photochemical processes at the air/water interface of biofilm-containing solutions were studied, demonstrating abiotic VOC production from authentic biogenic surfactants under ambient conditions. Using a combination of online-APCI-HRMS and PTR-ToF-MS, unsaturated and functionalized VOCs were identified and quantified, giving emission fluxes comparable to previous field and laboratory observations. Interestingly, VOC fluxes increased with the decay of microbial cells in the samples, indicating that cell lysis due to cell death was the main source for surfactants and VOC production. In particular, irradiation of samples containing solely biofilm cells without matrix components exhibited the strongest VOC production upon irradiation. In agreement with previous studies, LC-MS measurements of the liquid phase suggested the presence of fatty acids and known photosensitizers, possibly inducing the observed VOC production via peroxy radical chemistry. Up to now, such VOC emissions were directly accounted to high biological activity in surface waters. However, the results obtained suggest that abiotic photochemistry can lead to similar emissions into the atmosphere, especially in less biologically-active regions. Furthermore, chamber experiments suggest that oxidation (O3/OH radicals) of the photochemically-produced VOCs leads to aerosol formation and growth, possibly affecting atmospheric chemistry and climate-related processes, such as cloud formation or the Earth's radiation budget.


Assuntos
Tensoativos/química , Compostos Orgânicos Voláteis/síntese química , Aerossóis/síntese química , Aerossóis/química , Atmosfera/química , Processos Fotoquímicos , Compostos Orgânicos Voláteis/química
6.
J Mass Spectrom ; 51(2): 141-9, 2016 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-26889930

RESUMO

Ambient desorption/ionization mass spectrometry (MS) has gained growing interest during the last decade due to its high analytical performance and yet simplicity. Here, one of the recently developed ambient desorption/ionization MS sources, the flowing atmospheric-pressure afterglow (FAPA) source, was investigated in detail regarding background ions and typical ionization patterns in the positive as well as the negative ion mode for a variety of compound classes, comprising alkanes, alcohols, aldehydes, ketones, carboxylic acids, organic peroxides and alkaloids. A broad range of signals for adducts and losses was found, besides the usually emphasized detection of quasimolecular ions, i.e. [M + H](+) and [M - H](-) in the positive and the negative mode, respectively. It was found that FAPA-MS is best suited for polar analytes containing nitrogen and/or oxygen functionalities, e.g. carboxylic acids, with low molecular weights and relatively high vapor pressures. In addition, the source was used in proof-of-principle studies, illustrating the capabilities and limitations of the technique: Firstly, traces of cocaine were detected and unambiguously identified on euro banknotes using FAPA ionization in combination with tandem MS, suggesting a correlation between cocaine abundance and age of the banknote. Secondly, FAPA-MS was used for the identification of acidic marker compounds in organic aerosol samples, indicating yet-undiscovered matrix and sample surface effects of ionization pathways in the afterglow region.

7.
Environ Sci Technol ; 49(9): 5571-8, 2015 May 05.
Artigo em Inglês | MEDLINE | ID: mdl-25861027

RESUMO

Organic compounds contribute to a major fraction of atmospheric aerosols and have significant impacts on climate and human health. However, because of their chemical complexity, their measurement remains a major challenge for analytical instrumentation. Here we present the development and characterization of a new soft ionization technique that allows mass spectrometric real-time detection of organic compounds in aerosols. The aerosol flowing atmospheric-pressure afterglow (AeroFAPA) ion source is based on a helium glow discharge plasma, which generates excited helium species and primary reagent ions. Ionization of the analytes occurs in the afterglow region after thermal desorption and produces mainly intact quasimolecular ions, facilitating the interpretation of the acquired mass spectra. We illustrate that changes in aerosol composition and concentration are detected on the time scale of seconds and in the ng m(-3) range. Additionally, the successful application of AeroFAPA-MS during a field study in a mixed forest region is presented. In general, the observed compounds are in agreement with previous offline studies; however, the acquisition of chemical information and compound identification is much faster. The results demonstrate that AeroFAPA-MS is a suitable tool for organic aerosol analysis and reveal the potential of this technique to enable new insights into aerosol formation, growth, and transformation in the atmosphere.


Assuntos
Aerossóis/análise , Pressão Atmosférica , Sistemas Computacionais , Espectrometria de Massas/métodos , Compostos Orgânicos/análise , Aerossóis/química , Humanos , Íons , Compostos Orgânicos/química
8.
Artigo em Inglês | MEDLINE | ID: mdl-24881453

RESUMO

We present the development and characterization of a combination of a micro-orifice volatilization impactor (MOVI) and an ion trap mass spectrometer (IT/MS) with an atmospheric-pressure chemical ionization (APCI) source. The MOVI is a multi-jet impactor with 100 nozzles, allowing the collection of aerosol particles by inertial impaction on a deposition plate. The pressure drop behind the nozzles is approximately 5%, resulting in a pressure of 96kPa on the collection surface for ambient pressures of 101.3 kPa. The cut-point diameter (diameter of 50% collection efficiency) is at 0.13 microm for a sampling flow rate of 10 L min(-1). After the collection step, aerosol particles are evaporated by heating the impaction surface and transferred into the APCI-IT/MS for detection of the analytes. APCI was used in the negative ion mode to detect predominantly mono- and dicarboxylic acids, which are major oxidation products of biogenic terpenes. The MOVI-APCI-IT/MS instrument was used for the analysis of laboratory-generated secondary organic aerosol (SOA), which was generated by ozonolysis of alpha-pinene in a 100 L continuous-flow reactor under dark and dry conditions. The combination of the MOVI with an APCI-IT/MS improved the detection Limits for small dicarboxylic acids, such as pinic acid, compared to online measurements by APCI-IT/MS. The Limits of detection and quantification for pinic acid were determined by external calibration to 4.4 ng and 13.2 ng, respectively. During a field campaign in the southern Rocky Mountains (USA) in summer 2011 (BEACHON-RoMBAS), the MOVI-APCI-IT/MS was applied for the analysis of ambient organic aerosols and the quantification of individual biogenic SOA marker compounds. Based on a measurement frequency of approximately 5 h, a diurnal cycle for pinic acid in the sampled aerosol particles was found with maximum concentrations at night (median: 10.1 ngm(-3)) and minimum concentrations during the day (median: 8.2 ng m(-3)), which is likely due to the partitioning behavior of pinic acid and the changing phase state of the organic aerosol particles with changing relative humidity.


Assuntos
Aerossóis/química , Ácidos Carboxílicos/análise , Espectrometria de Massas/métodos , Pressão Atmosférica , Monoterpenos Bicíclicos , Ácidos Carboxílicos/química , Humanos , Íons/análise , Espectrometria de Massas/instrumentação , Monoterpenos/química , Oxirredução , Ozônio/química , Terpenos/análise , Terpenos/química , Volatilização
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