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1.
J Environ Sci (China) ; 114: 98-114, 2022 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-35459518

RESUMO

The characteristics of wintertime volatile organic compounds (VOCs) in the North China Plain (NCP) region are complicated and remain obscure. VOC measurements were conducted by a proton transfer reaction time-of-flight mass spectrometer (PTR-ToF-MS) at a rural site in the NCP from November to December 2018. Uncalibrated ions measured by PTR-ToF-MS were quantified and the overall VOC compositions were investigated by combining the measurements of PTR-ToF-MS and gas chromatography-mass spectrometer/flame ionization detector (GC-MS/FID). The measurement showed that although atmospheric VOCs concentrations are often dominated by primary emissions, the secondary formation of oxygenated VOCs (OVOCs) is non-negligible in the wintertime, i.e., OVOCs accounts for 42% ± 7% in the total VOCs (151.3 ± 75.6 ppbV). We demonstrated that PTR-MS measurements for isoprene are substantially overestimated due to the interferences of cycloalkanes. The chemical changes of organic carbon in a pollution accumulation period were investigated, which suggests an essential role of fragmentation reactions for large, chemically reduced compounds during the heavy-polluted stage in wintertime pollution. The changes of emission ratios of VOCs between winter 2011 and winter 2018 in the NCP support the positive effect of "coal to gas" strategies in curbing air pollutants. The high abundances of some key species (e.g. oxygenated aromatics) indicate the strong emissions of coal combustion in wintertime of NCP. The ratio of naphthalene to C8 aromatics was proposed as a potential indicator of the influence of coal combustion on VOCs.


Assuntos
Poluentes Atmosféricos , Compostos Orgânicos Voláteis , Poluentes Atmosféricos/análise , China , Carvão Mineral , Monitoramento Ambiental , Prótons , Tempo de Reação , Compostos Orgânicos Voláteis/análise
2.
Environ Sci Technol ; 56(4): 2204-2212, 2022 02 15.
Artigo em Inglês | MEDLINE | ID: mdl-35104400

RESUMO

Nitrous acid (HONO) is an important component of the global nitrogen cycle and can regulate the atmospheric oxidative capacity. Soil is an important source of HONO. [HONO]*, the equilibrium gas-phase concentration over the aqueous solution of nitrous acid in the soil, has been suggested as a key parameter for quantifying soil fluxes of HONO. However, [HONO]* has not yet been well-validated and quantified. Here, we present a method to retrieve [HONO]* by conducting controlled dynamic chamber experiments with soil samples applied with different HONO concentrations at the chamber inlet. We show a bi-directional soil-atmosphere exchange of HONO and confirm the existence of [HONO]* over soil: when [HONO]* is higher than the atmospheric HONO concentration, HONO will be released from soil; otherwise, HONO will be deposited. We demonstrate that [HONO]* is a soil characteristic, which is independent of HONO concentrations in the chamber but varies with different soil water contents. We illustrate the robustness of using [HONO]* for quantifying soil fluxes of HONO, whereas the laboratory-determined chamber HONO fluxes can largely deviate from those in the real world for the same soil sample. This work advances the understanding of the soil-atmosphere exchange of HONO and the evaluation of its impact on the atmospheric oxidizing capacity.


Assuntos
Ácido Nitroso , Solo , Atmosfera , Ciclo do Nitrogênio , Microbiologia do Solo , Água
3.
Sci Total Environ ; 803: 150010, 2022 Jan 10.
Artigo em Inglês | MEDLINE | ID: mdl-34487897

RESUMO

This study investigates the impact of aerosol liquid water content (ALWC) and related factors, i.e., relative humidity (RH), aerosol mass concentration (PM2.5), and aerosol hygroscopicity, on aerosol optical properties, based on field measurements made in the Pearl River Delta (PRD) region of China at the surface (1 November 2019 to 21 January 2020) and in the upper boundary layer (the 532-m Guangzhou tower from 1 February to 21 March 2020). In general, temporal variations in the ambient aerosol backscattering coefficient (ßp) and ALWC followed each other. However, the surface ßp and 532-m ßp had generally opposite diurnal variation patterns, caused by dramatic differences in PM2.5 and ambient RH between the surface and the upper boundary layer. The ambient 532-m RH was systematically higher than the surface RH, with the latter having a much pronounced diurnal cycle than the former. The surface PM2.5 concentration was systematically higher than the PM2.5 concentration at 532 m, and their diurnal cycle patterns were overall opposite. These dramatic differences reveal that the atmospheric variables, i.e., ambient RH and the PM2.5 concentration in the upper boundary layer, cannot be directly represented by the same variables at the surface. Vertical variability should be considered. Clear differences in the sensitivities of aerosol light scattering to ambient RH, PM2.5, and aerosol hygroscopicity between the two levels were found and examined. Aerosol chemical composition played a minor role in causing the differences between the two levels. In particular, ßp was more sensitive to PM2.5 at the surface level but more to the ambient RH in the upper boundary layer. The larger contribution of aerosol loading to the variability in ßp at the surface implies that local emission controls can decrease ßp and further improve atmospheric visibility effectively at the surface during winter in the PRD region.


Assuntos
Poluentes Atmosféricos , Material Particulado , Aerossóis/análise , Poluentes Atmosféricos/análise , China , Monitoramento Ambiental , Umidade , Material Particulado/análise , Molhabilidade
4.
Acta Pharmacol Sin ; 2021 Dec 10.
Artigo em Inglês | MEDLINE | ID: mdl-34893682

RESUMO

PTEN-induced putative kinase 1 (PINK1)/parkin pathway mediates mitophagy, which is a specialized form of autophagy. Evidence shows that PINK1 can exert protective effects against stress-induced neuronal cell death. In the present study we investigated the effects of PINK1 overexpression on tau hyperphosphorylation, mitochondrial dysfunction and oxidative stress in a specific rat model of tau hyperphosphorylation. We showed that intracerebroventricular (ICV) microinjection of forskolin (FSK, 80 µmol) induced tau hyperphosphorylation in the rat brain and resulted in significant spatial working memory impairments in Y-maze test, accompanied by synaptic dysfunction (reduced expression of synaptic proteins synaptophysin and postsynaptic density protein 95), and neuronal loss in the hippocampus. Adeno-associated virus (AAV)-mediated overexpression of PINK1 prevented ICV-FSK-induced cognition defect and pathological alterations in the hippocampus, whereas PINK1-knockout significantly exacerbated ICV-FSK-induced deteriorated effects. Furthermore, we revealed that AAV-PINK1-mediated overexpression of PINK1 alleviated ICV-FSK-induced tau hyperphosphorylation by restoring the activity of PI3K/Akt/GSK3ß signaling. PINK1 overexpression reversed the abnormal changes in mitochondrial dynamics, defective mitophagy, and decreased ATP levels in the hippocampus. Moreover, PINK1 overexpression activated Nrf2 signaling, thereby increasing the expression of antioxidant proteins and reducing oxidative damage. These results suggest that PINK1 deficiency exacerbates FSK-induced tau pathology, synaptic damage, mitochondrial dysfunction, and antioxidant system defects, which were reversed by PINK1 overexpression. Our data support a critical role of PINK1-mediated mitophagy in controlling mitochondrial quality, tau hyperphosphorylation, and oxidative stress in a rat model of Alzheimer's disease.

5.
Nat Commun ; 12(1): 6416, 2021 11 05.
Artigo em Inglês | MEDLINE | ID: mdl-34741045

RESUMO

Low clouds play a key role in the Earth-atmosphere energy balance and influence agricultural production and solar-power generation. Smoke aloft has been found to enhance marine stratocumulus through aerosol-cloud interactions, but its role in regions with strong human activities and complex monsoon circulation remains unclear. Here we show that biomass burning aerosols aloft strongly increase the low cloud coverage over both land and ocean in subtropical southeastern Asia. The degree of this enhancement and its spatial extent are comparable to that in the Southeast Atlantic, even though the total biomass burning emissions in Southeast Asia are only one-fifth of those in Southern Africa. We find that a synergetic effect of aerosol-cloud-boundary layer interaction with the monsoon is the main reason for the strong semi-direct effect and enhanced low cloud formation in southeastern Asia.

6.
Environ Sci Technol ; 55(24): 16747-16756, 2021 12 21.
Artigo em Inglês | MEDLINE | ID: mdl-34699200

RESUMO

Aqueous extracts of biogenic secondary organic aerosols (BSOAs) have been found to exhibit fluorescence that may interfere with the laser/light-induced fluorescence (LIF) detection of primary biological aerosol particles (PBAPs). In this study, we quantified the interference of BSOAs to PBAPs by directly measuring airborne BSOA particles, rather than aqueous extracts. BSOAs were generated by the reaction of d-limonene (LIM) or α-pinene (PIN) and ozone (O3) with or without ammonia in a chamber under controlled conditions. With an excitation wavelength of 355 nm, BSOAs exhibited peak emissions at 464-475 nm, while fungal spores exhibited peak emissions at 460-483 nm; the fluorescence intensity of BSOAs with diameters of 0.7 µm was in the same order of magnitude as that of fungal spores with diameters of 3 µm. The number fraction of 0.7 µm BSOAs that exhibited fluorescence above the threshold was in the range of 1.9-15.9%, depending on the species of precursors, relative humidity (RH), and ammonia. Similarly, the number fraction of 3 µm fungal spores that exhibited fluorescence above the threshold was 4.9-36.2%, depending on the species of fungal spores. Normalized fluorescence by particle volumes suggests that BSOAs exhibited fluorescence in the same order of magnitude as pollen and 10-100 times higher than that of fungal spores. A comparison with ambient particles suggests that BSOAs caused significant interference to ambient fine particles (15 of 16 ambient fine particle measurements likely detected BSOAs) and the interference was smaller for ambient coarse particles (4 of 16 ambient coarse particle measurements likely detected BSOAs) when using LIF instruments.


Assuntos
Poluentes Atmosféricos , Ozônio , Aerossóis/análise , Poluentes Atmosféricos/análise , Limoneno , Tamanho da Partícula , Espectrometria de Fluorescência , Esporos Fúngicos
7.
Sci Total Environ ; 788: 147712, 2021 Sep 20.
Artigo em Inglês | MEDLINE | ID: mdl-34134364

RESUMO

In recent decade the ambient fine particle (PM2.5) levels have shown a trend of distinct dropping in China, while ground-level ozone concentrations have been increasing in Beijing and many other Chinese mega-cities. The variation pattern in Los Angeles was markedly different, with PM2.5 and ozone decreasing together over past decades. In this study, we utilize observation-based methods to establish the parametric relationship between PM2.5 concentration and key aerosol physical properties (including aerosol optical depth and aerosol surface concentration), and an observation-based 1-D photochemical model to quantify the response of PM2.5 decline in enhancing ground-level ozone pollution over a large PM2.5 concentration range (10-120 µg m-3). We find that the significance of ozone enhancement due to PM2.5 dropping depends on both the PM2.5 levels and optical properties of particles. Ozone formation increased by 37% in 2006-2016 due to PM2.5 dropping in Beijing, while it becomes less important (7%) as PM2.5 reaches below 40 µg/m3, similar to Los Angeles since 1980s. Therefore, the two cities show the convergence of air pollutant characteristics. Hence a control strategy prioritizing reactive volatile organic compound abatement is projected to yield simultaneous ozone and PM2.5 reductions in Beijing, as experienced in Los Angeles.

8.
Science ; 2021 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-34016743

RESUMO

Airborne transmission by droplets and aerosols is important for the spread of viruses. Face masks are a well-established preventive measure, but their effectiveness for mitigating SARS-CoV-2 transmission is still under debate. We show that variations in mask efficacy can be explained by different regimes of virus abundance and related to population-average infection probability and reproduction number. For SARS-CoV-2, the viral load of infectious individuals can vary by orders of magnitude. We find that most environments and contacts are under conditions of low virus abundance (virus-limited) where surgical masks are effective at preventing virus spread. More advanced masks and other protective equipment are required in potentially virus-rich indoor environments including medical centers and hospitals. Masks are particularly effective in combination with other preventive measures like ventilation and distancing.

9.
Sci Total Environ ; 770: 144821, 2021 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-33736402

RESUMO

The light absorption black carbon (BC) and brown carbon (BrC) are two important sources of uncertainties in radiative forcing estimate. Here we investigated the light absorption enhancement (Eabs) of BC due to coated materials at an urban (Beijing) and a rural site (Gucheng) in North China Plain (NCP) in winter 2019 by using a photoacoustic extinctiometer coupled with a thermodenuder. Our results showed that the average (±1σ) Eabs was 1.32 (±0.15) at the rural site, which was slightly higher than that at the urban site (1.24 ± 0.15). The dependence of Eabs on coating materials was found to be relatively limited at both sites. However, Eabs presented considerable increases as a function of relative humidity below 70%. Further analysis showed that Eabs during non-heating period in Beijing was mainly caused by secondary components, while it was dominantly contributed by enhanced primary emissions in heating season at both sites. In particular, aerosol particles mixed with coal combustion emissions had a large impact on Eabs (>1.40), while the fresh traffic emissions and freshly oxidized secondary OA (SOA) had limited Eabs (1.00-1.23). Although highly aged or aqueous-phase processed SOA coated on BC showed the largest Eabs, their contributions to the bulk absorption enhancement were generally small. We also quantified the absorption of BrC and source contributions. The results showed the BrC absorption at the rural site was nearly twice that of urban site, yet absorption Ångström exponents were similar. Multiple linear regression analysis highlighted the major sources of BrC being coal combustion emissions and photochemical SOA at both sites with additional biomass burning at the rural site. Overall, our results demonstrated the relatively limited winter light absorption enhancement of BC in different chemical environments in NCP, which needs be considered in regional climate models to improve BC radiative forcing estimates.

10.
J Clin Pharm Ther ; 46(2): 476-483, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33210301

RESUMO

WHAT IS KNOWN AND OBJECTIVE: Adverse drug events (ADEs) are a major public health concern worldwide and may prolong hospital stays, causing a burden on the healthcare system and increasing the associated costs. Therefore, optimizing medication use and reducing ADEs are priorities for public health. Medication safety can be monitored and improved by identifying ADEs. The utilization of diagnoses coded according to the International Statistical Classification of Diseases and Related Health Problems (ICD) system for the identification of ADEs has been firmly established. In Taiwan, however, the validity of recording ADEs on the basis of inpatient ICD-10-CM T codes has not been evaluated. Therefore, this study investigated the potential usefulness of ICD-10-CM T codes in routine hospital data for the identification of ADEs and for increasing the rate of reporting. METHODS: We use hospital claims data of hospitalized patients from one medical centre in northern Taiwan between 1 July 2016 and 30 June 2018. We defined an ADE to have taken place if an ICD-10-CM T code was present among the primary or secondary diagnosis codes. The inpatients who were discharged with T codes in a primary or secondary diagnosis were identified by the computerized T code information platform, and the retrospective review of the medical charts was performed by pharmacists to confirm the ADEs. RESULTS AND DISCUSSION: 1384 inpatients who were discharged with the relevant T codes in a primary or secondary diagnosis were identified during the study period. Code T36 (poisoning by, adverse effect of or underdosing of systemic antibiotics) was the most common code, accounting for 56.6%, followed by T42 (17.7%; poisoning by, adverse effect of or underdosing of antiepileptic, sedative-hypnotic or antiparkinsonism drug). Overall, 789 clinically significant ADEs were identified after medical chart review. The dermatologic system was the most commonly involved. The overall positive predictive value for a flagged code representing an ADE was 57%. Furthermore, the use of T codes to confirm the number of ADE cases increased the ADE reporting rate by 9.17%. WHAT IS NEW AND CONCLUSION: The PPV of ICD-10-CM T codes analysed in our study was insufficient for identifying ADEs during hospitalization. The sensitivity and specificity of this were inadequate. However, the T code system can be used as an auxiliary resource for pharmacists to identify potential ADEs and report the information as prompts on the physician order entry system. When a physician prescribes a drug that may cause an ADE in a patient, an alert is issued to ensure medication safety. In conclusion, the T codes did not perform well in our study and caution should be exercised in their use to identify ADEs on their own.


Assuntos
Efeitos Colaterais e Reações Adversas Relacionados a Medicamentos/epidemiologia , Revisão da Utilização de Seguros/estatística & dados numéricos , Classificação Internacional de Doenças , Humanos , Reprodutibilidade dos Testes , Índice de Gravidade de Doença , Taiwan
11.
Faraday Discuss ; 226: 207-222, 2021 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-33284304

RESUMO

Fine-particle pollution associated with winter haze threatens the health of more than 400 million people in the North China Plain. The Multiphase chemistry experiment in Fogs and Aerosols in the North China Plain (McFAN) investigated the physicochemical mechanisms leading to haze formation with a focus on the contributions of multiphase processes in aerosols and fogs. We integrated observations on multiple platforms with regional and box model simulations to identify and characterize the key oxidation processes producing sulfate, nitrate and secondary organic aerosols. An outdoor twin-chamber system was deployed to conduct kinetic experiments under real atmospheric conditions in comparison to literature kinetic data from laboratory studies. The experiments were spanning multiple years since 2017 and an intensive field campaign was performed in the winter of 2018. The location of the site minimizes fast transition between clean and polluted air masses, and regimes representative for the North China Plain were observed at the measurement location in Gucheng near Beijing. The consecutive multi-year experiments document recent trends of PM2.5 pollution and corresponding changes of aerosol physical and chemical properties, enabling in-depth investigations of established and newly proposed chemical mechanisms of haze formation. This study is mainly focusing on the data obtained from the winter campaign 2018. To investigate multiphase chemistry, the results are presented and discussed by means of three characteristic cases: low humidity, high humidity and fog. We find a strong relative humidity dependence of aerosol chemical compositions, suggesting an important role of multiphase chemistry. Compared with the low humidity period, both PM1 and PM2.5 show higher mass fraction of secondary inorganic aerosols (SIA, mainly as nitrate, sulfate and ammonium) and secondary organic aerosols (SOA) during high humidity and fog episodes. The changes in aerosol composition further influence aerosol physical properties, e.g., with higher aerosol hygroscopicity parameter κ and single scattering albedo SSA under high humidity and fog cases. The campaign-averaged aerosol pH is 5.1 ± 0.9, of which the variation is mainly driven by the aerosol water content (AWC) concentrations. Overall, the McFAN experiment provides new evidence of the key role of multiphase reactions in regulating aerosol chemical composition and physical properties in polluted regions.

12.
Artigo em Inglês | MEDLINE | ID: mdl-33153155

RESUMO

The role of aerosolized SARS-CoV-2 viruses in airborne transmission of COVID-19 has been debated. The aerosols are transmitted through breathing and vocalization by infectious subjects. Some authors state that this represents the dominant route of spreading, while others dismiss the option. Here we present an adjustable algorithm to estimate the infection risk for different indoor environments, constrained by published data of human aerosol emissions, SARS-CoV-2 viral loads, infective dose and other parameters. We evaluate typical indoor settings such as an office, a classroom, choir practice, and a reception/party. Our results suggest that aerosols from highly infective subjects can effectively transmit COVID-19 in indoor environments. This "highly infective" category represents approximately 20% of the patients who tested positive for SARS-CoV-2. We find that "super infective" subjects, representing the top 5-10% of subjects with a positive test, plus an unknown fraction of less-but still highly infective, high aerosol-emitting subjects-may cause COVID-19 clusters (>10 infections). In general, active room ventilation and the ubiquitous wearing of face masks (i.e., by all subjects) may reduce the individual infection risk by a factor of five to ten, similar to high-volume, high-efficiency particulate air (HEPA) filtering. A particularly effective mitigation measure is the use of high-quality masks, which can drastically reduce the indoor infection risk through aerosols.


Assuntos
Aerossóis , Infecções por Coronavirus/transmissão , Modelos Teóricos , Pneumonia Viral/transmissão , Microbiologia do Ar , Algoritmos , Betacoronavirus , COVID-19 , Infecções por Coronavirus/prevenção & controle , Filtração , Humanos , Máscaras , Pandemias/prevenção & controle , Pneumonia Viral/prevenção & controle , SARS-CoV-2 , Ventilação
13.
Proc Natl Acad Sci U S A ; 117(49): 31018-31025, 2020 12 08.
Artigo em Inglês | MEDLINE | ID: mdl-33229579

RESUMO

The Chinese "coal-to-gas" and "coal-to-electricity" strategies aim at reducing dispersed coal consumption and related air pollution by promoting the use of clean and low-carbon fuels in northern China. Here, we show that on top of meteorological influences, the effective emission mitigation measures achieved an average decrease of fine particulate matter (PM2.5) concentrations of ∼14% in Beijing and surrounding areas (the "2+26" pilot cities) in winter 2017 compared to the same period of 2016, where the dispersed coal control measures contributed ∼60% of the total PM2.5 reductions. However, the localized air quality improvement was accompanied by a contemporaneous ∼15% upsurge of PM2.5 concentrations over large areas in southern China. We find that the pollution transfer that resulted from a shift in emissions was of a high likelihood caused by a natural gas shortage in the south due to the coal-to-gas transition in the north. The overall shortage of natural gas greatly jeopardized the air quality benefits of the coal-to-gas strategy in winter 2017 and reflects structural challenges and potential threats in China's clean-energy transition.


Assuntos
Poluição do Ar/análise , Carvão Mineral/análise , Gás Natural/análise , Estações do Ano , China , Cidades , Política Ambiental , Calefação , Material Particulado/análise
14.
Environ Sci Technol ; 54(24): 15710-15721, 2020 12 15.
Artigo em Inglês | MEDLINE | ID: mdl-33237756

RESUMO

Secondary aerosol (SA) frequently drives severe haze formation on the North China Plain. However, previous studies mostly focused on submicron SA formation, thus our understanding of SA formation on supermicron particles remains poor. In this study, PM2.5 chemical composition and PM10 number size distribution measurements revealed that the SA formation occurred in very distinct size ranges. In particular, SA formation on dust-dominated supermicron particles was surprisingly high and increased with relative humidity (RH). SA formed on supermicron aerosols reached comparable levels with that on submicron particles during evolutionary stages of haze episodes. These results suggested that dust particles served as a medium for rapid secondary organic and inorganic aerosol formation under favorable photochemical and RH conditions in a highly polluted environment. Further analysis indicated that SA formation pathways differed among distinct size ranges. Overall, our study highlights the importance of dust in SA formation during non-dust storm periods and the urgent need to perform size-resolved aerosol chemical and physical property measurements in future SA formation investigations that are extended to the coarse mode because the large amount of SA formed thereon might have significant impacts on ice nucleation, radiative forcing, and human health.


Assuntos
Poluentes Atmosféricos , Poeira , Aerossóis/análise , Poluentes Atmosféricos/análise , China , Poeira/análise , Monitoramento Ambiental , Humanos , Tamanho da Partícula , Material Particulado/análise , Estações do Ano
15.
Acc Chem Res ; 53(10): 2034-2043, 2020 10 20.
Artigo em Inglês | MEDLINE | ID: mdl-32927946

RESUMO

Atmospheric aerosols and fine particulate matter (PM2.5) are strongly affecting human health and climate in the Anthropocene, that is, in the current era of globally pervasive and rapidly increasing human influence on planet Earth. Poor air quality associated with high aerosol concentrations is among the leading health risks worldwide, causing millions of attributable excess deaths and years of life lost every year. Besides their health impact, aerosols are also influencing climate through interactions with clouds and solar radiation with an estimated negative total effective radiative forcing that may compensate about half of the positive radiative forcing of carbon dioxide but exhibits a much larger uncertainty. Heterogeneous and multiphase chemical reactions on the surface and in the bulk of solid, semisolid, and liquid aerosol particles have been recognized to influence aerosol formation and transformation and thus their environmental effects. However, atmospheric multiphase chemistry is not well understood because of its intrinsic complexity of dealing with the matter in multiple phases and the difficulties of distinguishing its effect from that of gas phase reactions.Recently, research on atmospheric multiphase chemistry received a boost from the growing interest in understanding severe haze formation of very high PM2.5 concentrations in polluted megacities and densely populated regions. State-of-the-art models suggest that the gas phase reactions, however, are not capturing the high concentrations and rapid increase of PM2.5 observed during haze events, suggesting a gap in our understanding of the chemical mechanisms of aerosol formation. These haze events are characterized by high concentrations of aerosol particles and high humidity, especially favoring multiphase chemistry. In this Account, we review recent advances that we have made, as well as current challenges and future perspectives for research on multiphase chemical processes involved in atmospheric aerosol formation and transformation. We focus on the following questions: what are the key reaction pathways leading to aerosol formation under polluted conditions, what is the relative importance of multiphase chemistry versus gas-phase chemistry, and what are the implications for the development of efficient and reliable air quality control strategies? In particular, we discuss advances and challenges related to different chemical regimes of sulfate, nitrate, and secondary organic aerosols (SOAs) under haze conditions, and we synthesize new insights into the influence of aerosol water content, aerosol pH, phase state, and nanoparticle size effects. Overall, there is increasing evidence that multiphase chemistry plays an important role in aerosol formation during haze events. In contrast to the gas phase photochemical reactions, which are self-buffered against heavy pollution, multiphase reactions have a positive feedback mechanism, where higher particle matter levels accelerate multiphase production, which further increases the aerosol concentration resulting in a series of record-breaking pollution events. We discuss perspectives to fill the gap of the current understanding of atmospheric multiphase reactions that involve multiple physical and chemical processes from bulk to nanoscale and from regional to global scales. A synthetic approach combining laboratory experiments, field measurements, instrument development, and model simulations is suggested as a roadmap to advance future research.

16.
Environ Sci Technol ; 54(19): 11818-11826, 2020 10 06.
Artigo em Inglês | MEDLINE | ID: mdl-32876440

RESUMO

Isocyanic acid (HNCO) is a potentially toxic atmospheric pollutant, whose atmospheric concentrations are hypothesized to be linked to adverse health effects. An earlier model study estimated that concentrations of isocyanic acid in China are highest around the world. However, measurements of isocyanic acid in ambient air have not been available in China. Two field campaigns were conducted to measure isocyanic acid in ambient air using a high-resolution time-of-flight chemical ionization mass spectrometer (ToF-CIMS) in two different environments in China. The ranges of mixing ratios of isocyanic acid are from below the detection limit (18 pptv) to 2.8 ppbv (5 min average) with the average value of 0.46 ppbv at an urban site of Guangzhou in the Pearl River Delta (PRD) region in fall and from 0.02 to 2.2 ppbv with the average value of 0.37 ppbv at a rural site in the North China Plain (NCP) during wintertime, respectively. These concentrations are significantly higher than previous measurements in North America. The diurnal variations of isocyanic acid are very similar to secondary pollutants (e.g., ozone, formic acid, and nitric acid) in PRD, indicating that isocyanic acid is mainly produced by secondary formation. Both primary emissions and secondary formation account for isocyanic acid in the NCP. The lifetime of isocyanic acid in a lower atmosphere was estimated to be less than 1 day due to the high apparent loss rate caused by deposition at night in PRD. Based on the steady state analysis of isocyanic acid during the daytime, we show that amides are unlikely enough to explain the formation of isocyanic acid in Guangzhou, calling for additional precursors for isocyanic acid. Our measurements of isocyanic acid in two environments of China provide important constraints on the concentrations, sources, and sinks of this pollutant in the atmosphere.


Assuntos
Poluentes Atmosféricos , Poluentes Atmosféricos/análise , China , Cianatos/análise , Monitoramento Ambiental , América do Norte
17.
Science ; 369(6509): 1374-1377, 2020 09 11.
Artigo em Inglês | MEDLINE | ID: mdl-32913103

RESUMO

Aerosol acidity largely regulates the chemistry of atmospheric particles, and resolving the drivers of aerosol pH is key to understanding their environmental effects. We find that an individual buffering agent can adopt different buffer pH values in aerosols and that aerosol pH levels in populated continental regions are widely buffered by the conjugate acid-base pair NH4 +/NH3 (ammonium/ammonia). We propose a multiphase buffer theory to explain these large shifts of buffer pH, and we show that aerosol water content and mass concentration play a more important role in determining aerosol pH in ammonia-buffered regions than variations in particle chemical composition. Our results imply that aerosol pH and atmospheric multiphase chemistry are strongly affected by the pervasive human influence on ammonia emissions and the nitrogen cycle in the Anthropocene.

18.
Phys Chem Chem Phys ; 22(18): 9967-9973, 2020 May 14.
Artigo em Inglês | MEDLINE | ID: mdl-32352140

RESUMO

We investigated the hygroscopic growth of sodium chloride (NaCl) nanoparticles with curvature related diameters ranging from 10 nm to 200 nm, at different relative humidities using scanning force microscopy. Hygroscopic aerosol nanoparticles play a vital role in the Earth's climate and human health. We report that 10 nm NaCl nanoparticles adsorbed on silicon surfaces have a higher deliquescence relative humidity than larger NaCl nanoparticles (size > 30 nm). This finding is consistent with the observations for airborne nanoparticles by hygroscopicity tandem differential mobility analyzer. Therefore, the presence of silicon surfaces plays no significant role in the deliquescence relative humidity. Moreover, the study of individual airborne particles by means of scanning force microscopy revealed that the ability of water uptake, i.e. growth factor, of NaCl particles differs by as large as 40% at the same relative humidity. This finding indicates that the individual nature of NaCl particles influences the growth factor.

19.
Sci Total Environ ; 734: 139318, 2020 Sep 10.
Artigo em Inglês | MEDLINE | ID: mdl-32454334

RESUMO

Amino acids are important water-soluble nitrogen-containing compounds in atmospheric aerosols. They can be involved in cloud formation due to their hygroscopicity and have significant influences on the hygroscopicity of inorganic compounds, which have not yet been well characterized. In this work, the hygroscopic properties of three amino acids, including aspartic acid, glutamine, and serine, as well as their mixtures with ammonium sulfate (AS) were investigated using a hygroscopicity tandem differential mobility analyzer (HTDMA) system. The gradual water uptake of aspartic acid, glutamine and serine particles indicates that they exist as liquid phase at low RH. When mixing either aspartic acid or glutamine with AS by mass ratio of 1:3, we observed a clear phase transition but with a lower deliquescence relative humidity (DRH) with respect to that of pure AS. This suggests the crystallization of AS in the presence of each of these two amino acids. However, as the mass fractions of these two amino acids increased in the mixed particles, the deliquescence transition process was not obvious. In contrast, the crystallization of AS was efficiently hampered even at low content (i.e., 25% by mass) of serine in the mixed particles. The Zdanovskii-Stokes-Robinson (ZSR) method in general underestimated the hygroscopic growth of any mixtures at RH below 79% (prior to AS deliquescence), suggesting both amino acid and the partially dissolved AS contributed the overall hygroscopicity at RH in this range. Relatively good agreements were reached between the measurements and model predictions using the Extended Aerosol Inorganic Model (E-AIM) assuming solid state AS in the mixed particles for 1:3 aspartic acid-AS and glutamine-AS systems. However, the model failed to simulate the water uptake behaviors of any other systems. It demonstrates that the interactions between components within the aerosols have a significant effect on the phase state of the mixed particles.


Assuntos
Molhabilidade , Aerossóis , Aminoácidos , Sulfato de Amônio , Água
20.
Environ Sci Technol ; 54(7): 3849-3860, 2020 04 07.
Artigo em Inglês | MEDLINE | ID: mdl-32131584

RESUMO

Secondary organic aerosol (SOA) constitutes a large fraction of organic aerosol worldwide, however, the formation mechanisms in polluted environments remain poorly understood. Here we observed fast daytime growth of oxygenated organic aerosol (OOA) (with formation rates up to 10 µg m-3 h-1) during low relative humidity (RH, daytime average 38 ± 19%), high RH (53 ± 19%), and fog periods (77 ± 13%, fog occurring during nighttime with RH reaching 100%). Evidence showed that photochemical aqueous-phase SOA (aqSOA) formation dominantly contributed to daytime OOA formation during the periods with nighttime fog, while both photochemical aqSOA and gas-phase SOA (gasSOA) formation were important during other periods with the former contributing more under high RH and the latter under low RH conditions, respectively. Compared to daytime photochemical aqSOA production, dark aqSOA formation was only observed during the fog period and contributed negligibly to the increase in OOA concentrations due to fog scavenging processes. The rapid daytime aging, as indicated by the rapid decrease in m,p-xylene/ethylbenzene ratios, promoted the daytime formation of precursors for aqSOA formation, e.g., carbonyls such as methylglyoxal. Photooxidants related to aqSOA formation such as OH radical and H2O2 also bear fast daytime growth features even under low solar radiative conditions. The simultaneous increases in ultraviolet radiation, photooxidant, and aqSOA precursor levels worked together to promote the daytime photochemical aqSOA formation. We also found that biomass burning emissions can promote photochemical aqSOA formation by adding to the levels of aqueous-phase photooxidants and aqSOA precursors. Therefore, future mitigation of air pollution in a polluted environment would benefit from stricter control on biomass burning especially under high RH conditions.


Assuntos
Poluentes Atmosféricos , Aerossóis , China , Peróxido de Hidrogênio , Raios Ultravioleta
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