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1.
Sci Total Environ ; 802: 149695, 2022 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-34438127

RESUMO

Particle number size distribution (PNSD) is of importance for understanding the mechanisms of particle growth, haze formation and climate impacts. However, the measurements of PNSD aloft in megacities are very limited. Here we report the first simultaneous winter measurements of size-resolved particle number concentrations along with collocated gaseous species and aerosol composition at ground level and 260 m in Beijing. Our study showed that the vertical differences of particle number concentrations between ground level and aloft varied significantly as a function of particle size throughout the study. Further analysis illustrated the impacts of boundary dynamics and meteorological conditions on the vertical differences of PNSD. In particular, the temperature and relative humidity inversions were one of the most important factors by decoupling the boundary layer into different sources and processes. Positive matrix factorization analysis identified six sources of PNSD at both ground level and city aloft. The local source emissions dominantly contributed to Aitken-mode particles, and showed the largest vertical gradients in the city. Comparatively, the regional particles were highly correlated between ground level and city aloft, and the vertical differences were relatively stable throughout the day. Our results point towards a complex vertical evolution of PNSD due to the changes in boundary layer dynamics, meteorological conditions, sources, and processes in megacities.


Assuntos
Poluentes Atmosféricos , Aerossóis/análise , Poluentes Atmosféricos/análise , Pequim , China , Monitoramento Ambiental , Tamanho da Partícula , Material Particulado/análise , Estações do Ano
2.
Sci Total Environ ; 803: 150012, 2022 Jan 10.
Artigo em Inglês | MEDLINE | ID: mdl-34525708

RESUMO

Thermal desorption coupled with different detectors is an important analysis method for ambient carbonaceous aerosols. However, it is unclear how the compounds coexisting in both the gas and particle phases affect carbonaceous aerosol concentrations and measurements during thermal desorption. We observed matrix effects leading to a redistribution of different OC fractions (OC1 to OC4) during the thermal desorption process. These factors led to the formation of OC with low volatility (OC4), mainly from high-volatility OC (OC1 and OC2). Laboratory studies further indicated that ammonium promotes such matrix effects by transforming OC in the particle phase. Therefore, in addition to providing insights into the chemical evolution of OC during haze events, we argue that thermal-desorption-based OC measurements should be used with caution, which is an important step towards a more accurate measurement of OC in the ambient atmosphere.


Assuntos
Poluentes Atmosféricos , Compostos de Amônio , Aerossóis/análise , Poluentes Atmosféricos/análise , Carbono/análise , Monitoramento Ambiental , Tamanho da Partícula , Material Particulado/análise , Estações do Ano
3.
Sci Total Environ ; 808: 152191, 2021 Dec 05.
Artigo em Inglês | MEDLINE | ID: mdl-34875334

RESUMO

Carbonaceous aerosol is one of the main components of atmospheric particulate matter, which is of great significance due to its role in climate change, earth's radiation balance, visibility, and human health. In this work, carbonaceous aerosols were measured in Shijiazhuang and Beijing using the OC/EC analyzer from December 1, 2019 to March 15, 2020, which covered the Coronavirus Disease 2019 (COVID-19) pandemic. The observed results show that the gas-phase pollutants, such as NO, NO2, and aerosol-phase pollutants (Primary Organic Compounds, POC) from anthropogenic emissions, were significantly reduced during the lockdown period due to limited human activities in North China Plain (NCP). However, the atmospheric oxidation capacity (Ox/CO) shows a significantly increase during the lockdown period. Meanwhile, additional sources of nighttime Secondary Organic Carbon (SOC), Secondary Organic Aerosol (SOA), and babs, BrC(370 nm) are observed and ascribed to the nocturnal chemistry related to NO3 radical. The Potential Source Contribution Function (PSCF) analysis indicates that the southeast areas of the NCP region contributed more to the SOC during the lockdown period than the normal period. Our results highlight the importance of regional nocturnal chemistry in SOA formation.

4.
Environ Sci Atmos ; 1(7): 481-497, 2021 Nov 25.
Artigo em Inglês | MEDLINE | ID: mdl-34913037

RESUMO

The effects of the urban morphological characteristics on the spatial variation of near-surface PM2.5 air quality were examined. Unlike previous studies, we performed the analyses in real urban environments using continuous observations covering the whole scale of urban densities typically found in cities. We included data from 31 measurement stations divided into 8 different wind sectors with individually defined morphological characteristics leading to highly varying urban characteristics. The urban morphological characteristics explained up to 73% of the variance in normalized PM2.5 concentrations in street canyons, indicating that the spatial variation of the near-surface PM2.5 air quality was mostly defined by the characteristics studied. The fraction of urban trees nearby the stations was found to be the most important urban morphological characteristic in explaining the PM2.5 air quality, followed by the height-normalized roughness length as the second important parameter. An increase in the fraction of trees within 50 m of the stations from 25 percentile to 75 percentile (i.e. by the interquartile range, IQR) increased the normalized PM2.5 concentration by up to 24% in the street canyons. In open areas, an increase in the trees by the IQR actually decreased the normalized PM2.5 by 6% during the pre-COVID period. An increase in the height-normalized roughness length by the IQR increased the normalized PM2.5 by 9% in the street canyons. The results obtained in this study can help urban planners to identify the key urban characteristics affecting the near-surface PM2.5 air quality and also help researchers to evaluate how representative the existing measurement stations are compared to other parts of the cities.

5.
Environ Sci Atmos ; 1(7): 543-557, 2021 Nov 25.
Artigo em Inglês | MEDLINE | ID: mdl-34913038

RESUMO

Aerosol particles affect the climate and human health. Thus, understanding and accurately quantifying the processes associated with secondary formation of aerosol particles is highly important. The loss rate of vapor to aerosol particles affects the mass balance of that vapor in the atmosphere. The condensation sink (CS) describes the condensation rate of vapor to particles while the effective condensation sink (CSeff) describes the loss rate including both condensation and evaporation of vapor. When the CS is determined, the mass accommodation coefficient (α) is usually assumed to be unity and the condensing vapor is often assumed to be sulfuric acid. In addition, evaporation is assumed to be negligible (CSeff = CS) and the total loss rate of vapor is described by the CS. To study the possible uncertainties resulting from these assumptions, we investigate how vapor properties such as vapor mass and α affect the CS. In addition, the influence of evaporation on the CSeff is evaluated. The CS and CSeff are determined using particle number size distribution data from Beijing, China. Vapors are observed to have differing CSs depending on molecular mass and diffusivity volume and larger molecules are lost at a slower rate. If the condensing vapor is composed, for example, of oxidized organic molecules, which often have larger masses than sulfuric acid molecules, the CS is smaller than for pure sulfuric acid vapor. We find that if α is smaller than unity, the CS can be significantly overestimated if unity is assumed. Evaporation can significantly influence the CSeff for volatile and semi-volatile vapors. Neglecting the evaporation may result in an overestimation of vapor loss rate and hence an underestimation of the fraction of vapor molecules that is left to form clusters.

6.
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.

7.
Environ Sci Technol ; 2021 Nov 22.
Artigo em Inglês | MEDLINE | ID: mdl-34806377

RESUMO

The understanding at a molecular level of ambient secondary organic aerosol (SOA) formation is hampered by poorly constrained formation mechanisms and insufficient analytical methods. Especially in developing countries, SOA related haze is a great concern due to its significant effects on climate and human health. We present simultaneous measurements of gas-phase volatile organic compounds (VOCs), oxygenated organic molecules (OOMs), and particle-phase SOA in Beijing. We show that condensation of the measured OOMs explains 26-39% of the organic aerosol mass growth, with the contribution of OOMs to SOA enhanced during severe haze episodes. Our novel results provide a quantitative molecular connection from anthropogenic emissions to condensable organic oxidation product vapors, their concentration in particle-phase SOA, and ultimately to haze formation.

8.
Environ Sci Atmos ; 1(6): 449-472, 2021 Sep 23.
Artigo em Inglês | MEDLINE | ID: mdl-34604756

RESUMO

Major atmospheric oxidants (OH, O3 and NO3) dominate the atmospheric oxidation capacity, while H2SO4 is considered as a main driver for new particle formation. Although numerous studies have investigated the long-term trend of ozone in Europe, the trends of OH, NO3 and H2SO4 at specific sites are to a large extent unknown. The one-dimensional model SOSAA has been applied in several studies at the SMEAR II station and has been validated by measurements in several projects. Here, we applied the SOSAA model for the years 2007-2018 to simulate the atmospheric chemical components, especially the atmospheric oxidants OH and NO3, as well as H2SO4 at SMEAR II. The simulations were evaluated with observations from several shorter and longer campaigns at SMEAR II. Our results show that daily OH increased by 2.39% per year and NO3 decreased by 3.41% per year, with different trends of these oxidants during day and night. On the contrary, daytime sulfuric acid concentrations decreased by 2.78% per year, which correlated with the observed decreasing concentration of newly formed particles in the size range of 3-25 nm with 1.4% per year at SMEAR II during the years 1997-2012. Additionally, we compared our simulated OH, NO3 and H2SO4 concentrations with proxies, which are commonly applied in case a limited number of parameters are measured and no detailed model simulations are available.

9.
Environ Sci Atmos ; 1(6): 434-448, 2021 Sep 23.
Artigo em Inglês | MEDLINE | ID: mdl-34604755

RESUMO

Aerosol particles negatively affect human health while also having climatic relevance due to, for example, their ability to act as cloud condensation nuclei. Ultrafine particles (diameter D p < 100 nm) typically comprise the largest fraction of the total number concentration, however, their chemical characterization is difficult because of their low mass. Using an extractive electrospray time-of-flight mass spectrometer (EESI-TOF), we characterize the molecular composition of freshly nucleated particles from naphthalene and ß-caryophyllene oxidation products at the CLOUD chamber at CERN. We perform a detailed intercomparison of the organic aerosol chemical composition measured by the EESI-TOF and an iodide adduct chemical ionization mass spectrometer equipped with a filter inlet for gases and aerosols (FIGAERO-I-CIMS). We also use an aerosol growth model based on the condensation of organic vapors to show that the chemical composition measured by the EESI-TOF is consistent with the expected condensed oxidation products. This agreement could be further improved by constraining the EESI-TOF compound-specific sensitivity or considering condensed-phase processes. Our results show that the EESI-TOF can obtain the chemical composition of particles as small as 20 nm in diameter with mass loadings as low as hundreds of ng m-3 in real time. This was until now difficult to achieve, as other online instruments are often limited by size cutoffs, ionization/thermal fragmentation and/or semi-continuous sampling. Using real-time simultaneous gas- and particle-phase data, we discuss the condensation of naphthalene oxidation products on a molecular level.

10.
Natl Sci Rev ; 8(3): nwaa157, 2021 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-34691590

RESUMO

A new mechanism of new particle formation (NPF) is investigated using comprehensive measurements of aerosol physicochemical quantities and meteorological variables made in three continents, including Beijing, China; the Southern Great Plains site in the USA; and SMEAR II Station in Hyytiälä, Finland. Despite the considerably different emissions of chemical species among the sites, a common relationship was found between the characteristics of NPF and the stability intensity. The stability parameter (ζ = Z/L, where Z is the height above ground and L is the Monin-Obukhov length) is found to play an important role; it drops significantly before NPF as the atmosphere becomes more unstable, which may serve as an indicator of nucleation bursts. As the atmosphere becomes unstable, the NPF duration is closely related to the tendency for turbulence development, which influences the evolution of the condensation sink. Presumably, the unstable atmosphere may dilute pre-existing particles, effectively reducing the condensation sink, especially at coarse mode to foster nucleation. This new mechanism is confirmed by model simulations using a molecular dynamic model that mimics the impact of turbulence development on nucleation by inducing and intensifying homogeneous nucleation events.

11.
Environ Sci Technol ; 55(20): 13646-13656, 2021 10 19.
Artigo em Inglês | MEDLINE | ID: mdl-34585932

RESUMO

Gas-phase oxygenated organic molecules (OOMs) can contribute substantially to the growth of newly formed particles. However, the characteristics of OOMs and their contributions to particle growth rate are not well understood in urban areas, which have complex anthropogenic emissions and atmospheric conditions. We performed long-term measurement of gas-phase OOMs in urban Beijing during 2018-2019 using nitrate-based chemical ionization mass spectrometry. OOM concentrations showed clear seasonal variations, with the highest in the summer and the lowest in the winter. Correspondingly, calculated particle growth rates due to OOM condensation were highest in summer, followed by spring, autumn, and winter. One prominent feature of OOMs in this urban environment was a high fraction (∼75%) of nitrogen-containing OOMs. These nitrogen-containing OOMs contributed only 50-60% of the total growth rate led by OOM condensation, owing to their slightly higher volatility than non-nitrate OOMs. By comparing the calculated condensation growth rates and the observed particle growth rates, we showed that sulfuric acid and its clusters are the main contributors to the growth of sub-3 nm particles, with OOMs significantly promoting the growth of 3-25 nm particles. In wintertime Beijing, however, there are missing contributors to the growth of particles above 3 nm, which remain to be further investigated.


Assuntos
Poluentes Atmosféricos , Aerossóis/análise , Poluentes Atmosféricos/análise , Monitoramento Ambiental , Compostos Orgânicos/análise , Tamanho da Partícula , Material Particulado/análise , Estações do Ano
12.
Nat Commun ; 12(1): 5637, 2021 09 24.
Artigo em Inglês | MEDLINE | ID: mdl-34561456

RESUMO

Aerosol particles cool the climate by scattering solar radiation and by acting as cloud condensation nuclei. Higher temperatures resulting from increased greenhouse gas levels have been suggested to lead to increased biogenic secondary organic aerosol and cloud condensation nuclei concentrations creating a negative climate feedback mechanism. Here, we present direct observations on this feedback mechanism utilizing collocated long term aerosol chemical composition measurements and remote sensing observations on aerosol and cloud properties. Summer time organic aerosol loadings showed a clear increase with temperature, with simultaneous increase in cloud condensation nuclei concentration in a boreal forest environment. Remote sensing observations revealed a change in cloud properties with an increase in cloud reflectivity in concert with increasing organic aerosol loadings in the area. The results provide direct observational evidence on the significance of this negative climate feedback mechanism.

13.
Environ Sci Technol ; 2021 Aug 02.
Artigo em Inglês | MEDLINE | ID: mdl-34338506

RESUMO

Molecular clustering is the initial step of atmospheric new particle formation (NPF) that generates numerous secondary particles. Using two online mass spectrometers with and without a chemical ionization inlet, we characterized the neutral clusters and the naturally charged ion clusters during NPF periods in urban Beijing. In ion clusters, we observed pure sulfuric acid (SA) clusters, SA-amine clusters, SA-ammonia (NH3) clusters, and SA-amine-NH3 clusters. However, only SA clusters and SA-amine clusters were observed in the neutral form. Meanwhile, oxygenated organic molecule (OOM) clusters charged by a nitrate ion and a bisulfate ion were observed in ion clusters. Acid-base clusters correlate well with the occurrence of sub-3 nm particles, whereas OOM clusters do not. Moreover, with the increasing cluster size, amine fractions in ion acid-base clusters decrease, while NH3 fractions increase. This variation results from the reduced stability differences between SA-amine clusters and SA-NH3 clusters, which is supported by both quantum chemistry calculations and chamber experiments. The lower average number of dimethylamine (DMA) molecules in atmospheric ion clusters than the saturated value from controlled SA-DMA nucleation experiments suggests that there is insufficient DMA in urban Beijing to fully stabilize large SA clusters, and therefore, other basic molecules such as NH3 play an important role.

14.
Ecohealth ; 18(2): 217-228, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-34453636

RESUMO

In 2016, an outbreak of anthrax killing thousands of reindeer and affecting dozens of humans occurred on the Yamal peninsula, Northwest Siberia, after 70 years of epidemiological situation without outbreaks. The trigger of the outbreak has been ascribed to the activation of spores due to permafrost thaw that was accelerated during the summer heat wave. The focus of our study is on the dynamics of local environmental factors in connection with the observed anthrax revival. We show that permafrost was thawing rapidly for already 6 years before the outbreak. During 2011-2016, relatively warm years were followed by cold years with a thick snow cover, preventing freezing of the soil. Furthermore, the spread of anthrax was likely intensified by an extremely dry summer of 2016. Concurrent with the long-term decreasing trend in the regional annual precipitation, the rainfall in July 2016 was less than 10% of its 30-year mean value. We conclude that epidemiological situation of anthrax in the previously contaminated Arctic regions requires monitoring of climatic factors such as warming and precipitation extremes.

15.
Environ Sci Atmos ; 1(5): 214-227, 2021 Jul 22.
Artigo em Inglês | MEDLINE | ID: mdl-34355190

RESUMO

The lockdown measures implemented to curb the COVID-19 epidemic in Italy reduced human mobility dramatically, which resulted in a marked decline in traffic intensity. In this study, we present the effect of lockdown measures on several air pollutants, particle number size distribution as well as on regional new particle formation (NPF) frequency in the Po Valley (northern Italy). The results show that during the lockdown period, concentrations of nitrogen dioxide (NO2), nitric oxide (NO), benzene (C6H6), and toluene (C7H8) decreased, while ozone (O3) concentrations mildly increased as compared to the corresponding period in 2016-2019. Unlike gaseous pollutants, particulate matter mass concentrations (PM2.5 and PM10) showed no significant changes. The impact of lockdown measures on particle number size distributions were also quite limited. During the lockdown period, the number concentrations of 10-25 and 25-50 nm primary particles were reduced by 66% and 34%, respectively, at the regional background site (Ispra) but surprisingly there was no difference during and after lockdown at the urban background site (Modena). Conversely, the NPF frequency was exceptionally high, 70%, in Modena during the lockdown as compared to values (22-26%) observed for the same period in 2006 and 2009, while NPF frequency in Ispra only slightly increased compared to the same period in 2016-2019. The particle growth rates, however, were slightly lower during the lockdown at both sites compared to other periods. The study shows that a drastic decrease in traffic had little influence on particulate pollution levels in the Po Valley, suggesting that other sources and processes also have a prominent impact on particle number and particulate matter mass concentration in this region.

16.
Ann Work Expo Health ; 2021 Aug 08.
Artigo em Inglês | MEDLINE | ID: mdl-34365499

RESUMO

STOFFENMANAGER® and the Advanced REACH Tool (ART) are recommended tools by the European Chemical Agency for regulatory chemical safety assessment. The models are widely used and accepted within the scientific community. STOFFENMANAGER® alone has more than 37 000 users globally and more than 310 000 risk assessment have been carried out by 2020. Regardless of their widespread use, this is the first study evaluating the theoretical backgrounds of each model. STOFFENMANAGER® and ART are based on a modified multiplicative model where an exposure base level (mg m-3) is replaced with a dimensionless intrinsic emission score and the exposure modifying factors are replaced with multipliers that are mainly based on subjective categories that are selected by using exposure taxonomy. The intrinsic emission is a unit of concentration to the substance emission potential that represents the concentration generated in a standardized task without local ventilation. Further information or scientific justification for this selection is not provided. The multipliers have mainly discrete values given in natural logarithm steps (…, 0.3, 1, 3, …) that are allocated by expert judgements. The multipliers scientific reasoning or link to physical quantities is not reported. The models calculate a subjective exposure score, which is then translated to an exposure level (mg m-3) by using a calibration factor. The calibration factor is assigned by comparing the measured personal exposure levels with the exposure score that is calculated for the respective exposure scenarios. A mixed effect regression model was used to calculate correlation factors for four exposure group [e.g. dusts, vapors, mists (low-volatiles), and solid object/abrasion] by using ~1000 measurements for STOFFENMANAGER® and 3000 measurements for ART. The measurement data for calibration are collected from different exposure groups. For example, for dusts the calibration data were pooled from exposure measurements sampled from pharmacies, bakeries, construction industry, and so on, which violates the empirical model basic principles. The calibration databases are not publicly available and thus their quality or subjective selections cannot be evaluated. STOFFENMANAGER® and ART can be classified as subjective categorization tools providing qualitative values as their outputs. By definition, STOFFENMANAGER® and ART cannot be classified as mechanistic models or empirical models. This modeling algorithm does not reflect the physical concept originally presented for the STOFFENMANAGER® and ART. A literature review showed that the models have been validated only at the 'operational analysis' level that describes the model usability. This review revealed that the accuracy of STOFFENMANAGER® is in the range of 100 000 and for ART 100. Calibration and validation studies have shown that typical log-transformed predicted exposure concentration and measured exposure levels often exhibit weak Pearson's correlations (r is <0.6) for both STOFFENMANAGER® and ART. Based on these limitations and performance departure from regulatory criteria for risk assessment models, it is recommended that STOFFENMANAGER® and ART regulatory acceptance for chemical safety decision making should be explicitly qualified as to their current deficiencies.

17.
Environ Int ; 155: 106662, 2021 10.
Artigo em Inglês | MEDLINE | ID: mdl-34098335

RESUMO

BACKGROUND: The evidence on the association between ultrafine (UFP) particles and mortality is still inconsistent. Moreover, health effects of specific UFP sources have not been explored. We assessed the impact of UFP sources on daily mortality in Barcelona, Helsinki, London, and Zurich. METHODS: UFP sources were previously identified and quantified for the four cities: daily contributions of photonucleation, two traffic sources (fresh traffic and urban, with size mode around 30 nm and 70 nm, respectively), and secondary aerosols were obtained from data from an urban background station. Different periods were investigated in each city: Barcelona 2013-2016, Helsinki 2009-2016, London 2010-2016, and Zurich 2011-2014. The associations between total particle number concentrations (PNC) and UFP sources and daily (natural, cardiovascular [CVD], and respiratory) mortality were investigated using city-specific generalized linear models (GLM) with quasi-Poisson regression. RESULTS: We found inconsistent results across cities, sources, and lags for associations with natural, CVD, and respiratory mortality. Increased risk was observed for total PNC and natural mortality in Helsinki (lag 2; 1.3% [0.07%, 2.5%]), CVD mortality in Barcelona (lag 1; 3.7% [0.17%, 7.4%]) and Zurich (lag 0; 3.8% [0.31%, 7.4%]), and respiratory mortality in London (lag 3; 2.6% [0.84%, 4.45%]) and Zurich (lag 1; 9.4% [1.0%, 17.9%]). A similar pattern of associations between health outcomes and total PNC was followed by the fresh traffic source, for which we also found the same associations and lags as for total PNC. The urban source (mostly aged traffic) was associated with respiratory mortality in Zurich (lag 1; 12.5% [1.7%, 24.2%]) and London (lag 3; 2.4% [0.90%, 4.0%]) while the secondary source was associated with respiratory mortality in Zurich (lag 1: 12.0% [0.63%, 24.5%]) and Helsinki (4.7% [0.11%, 9.5%]). Reduced risk for the photonucleation source was observed for respiratory mortality in Barcelona (lag 2, -8.6% [-14.5%, -2.4%]) and for CVD mortality in Helsinki, as this source is present only in clean atmospheres (lag 1, -1.48 [-2.75, -0.21]). CONCLUSIONS: We found inconsistent results across cities, sources and lags for associations with natural, CVD, and respiratory mortality.


Assuntos
Poluentes Atmosféricos , Poluição do Ar , Idoso , Poluentes Atmosféricos/análise , Poluentes Atmosféricos/toxicidade , Poluição do Ar/análise , Cidades , Humanos , Tamanho da Partícula , Material Particulado/análise
18.
Environ Sci Technol ; 55(10): 6665-6676, 2021 05 18.
Artigo em Inglês | MEDLINE | ID: mdl-33960763

RESUMO

Gaseous sulfuric acid (H2SO4) is a crucial precursor for secondary aerosol formation, particularly for new particle formation (NPF) that plays an essential role in the global number budget of aerosol particles and cloud condensation nuclei. Due to technology challenges, global-wide and long-term measurements of gaseous H2SO4 are currently very challenging. Empirical proxies for H2SO4 have been derived mainly based on short-term intensive campaigns. In this work, we performed comprehensive measurements of H2SO4 and related parameters in the polluted Yangtze River Delta in East China during four seasons and developed a physical proxy based on the budget analysis of gaseous H2SO4. Besides the photo-oxidation of SO2, we found that primary emissions can contribute considerably, particularly at night. Dry deposition has the potential to be a non-negligible sink, in addition to condensation onto particle surfaces. Compared with the empirical proxies, the newly developed physical proxy demonstrates extraordinary stability in all the seasons and has the potential to be widely used to improve the understanding of global NPF fundamentally.


Assuntos
Poluentes Atmosféricos , Material Particulado , Poluentes Atmosféricos/análise , China , Monitoramento Ambiental , Tamanho da Partícula , Material Particulado/análise , Rios , Ácidos Sulfúricos
19.
Artigo em Inglês | MEDLINE | ID: mdl-33809366

RESUMO

Transmission of respiratory viruses is a complex process involving emission, deposition in the airways, and infection. Inhalation is often the most relevant transmission mode in indoor environments. For severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the risk of inhalation transmission is not yet fully understood. Here, we used an indoor aerosol model combined with a regional inhaled deposited dose model to examine the indoor transport of aerosols from an infected person with novel coronavirus disease (COVID-19) to a susceptible person and assess the potential inhaled dose rate of particles. Two scenarios with different ventilation rates were compared, as well as adult female versus male recipients. Assuming a source strength of 10 viruses/s, in a tightly closed room with poor ventilation (0.5 h-1), the respiratory tract deposited dose rate was 140-350 and 100-260 inhaled viruses/hour for males and females; respectively. With ventilation at 3 h-1 the dose rate was only 30-90 viruses/hour. Correcting for the half-life of SARS-CoV-2 in air, these numbers are reduced by a factor of 1.2-2.2 for poorly ventilated rooms and 1.1-1.4 for well-ventilated rooms. Combined with future determinations of virus emission rates, the size distribution of aerosols containing the virus, and the infectious dose, these results could play an important role in understanding the full picture of potential inhalation transmission in indoor environments.


Assuntos
COVID-19 , Infecções por Coronavirus , Coronavirus , Aerossóis , Feminino , Humanos , Masculino , SARS-CoV-2
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