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Droplets and aerosols: An artificial dichotomy in respiratory virus transmission

HEALTH SCIENCE REPORTS 2021年第2期4卷 e275页

作者： Drossinos, Yannis Weber, Thomas P. Stilianakis, Nikolaos, I European Commiss Joint Res Ctr Ispra Italy European Commiss Directorate Gen Hlth & Food Safety Brussels Belgium Univ Erlangen Nurnberg Dept Biometry & Epidemiol Erlangen Germany

In the medical literature, three mutually non-exclusive modes of pathogen transmission associated with respiratory droplets are usually identified: contact, droplet, and airborne (or aerosol) transmission. The demarcation between droplet and airborne transmission is often based on a cut-off droplet diameter, most commonly 5 mu m. We argue here that the infectivity of a droplet, and consequently the transmissivity of the virus, as a function of droplet size is a continuum, depending on numerous factors (gravitational settling rate, transport, and dispersion in a turbulent air jet, viral load and viral shedding, virus inactivation) that cannot be adequately characterized by a single droplet diameter. We propose instead that droplet and aerosol transmission should be replaced by a unique airborne transmission mode, to be distinguished from contact transmission.

关键词： aerosols airborne droplets influenza respiratory pathogens SARS-CoV-2 transmission mode

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Assessing the Seasonal Dynamics of Nitrate and Sulfate aerosols at the South Pole Utilizing Stable Isotopes

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JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES 2019年第14期124卷 8161-8177页

作者： Walters, Wendell W. Michalski, Greg Bohlkes, J. K. Alexander, Becky Savarino, Joel Thiemens, Mark H. Brown Univ Dept Earth Environm & Planetary Sci Providence RI 02912 USA Brown Univ Inst Brown Environm & Soc Providence RI 02912 USA Purdue Univ Dept Earth Atmospher & Planetary Sci W Lafayette IN 47907 USA Purdue Univ Dept Chem W Lafayette IN 47907 USA US Geol Survey 959 Natl Ctr Reston VA 22092 USA Univ Washington Dept Atmospher Sci Seattle WA 98195 USA Univ Grenoble Alpes CNRS IRD Grenoble INPIGE Grenoble France Univ Calif San Diego Dept Chem & Biogeochem San Diego CA 92103 USA

Atmospheric nitrate (NO3- = particulate NO3- + gas-phase nitric acid [HNO3]) and sulfate (SO42-) are key molecules that play important roles in numerous atmospheric processes. Here, the seasonal cycles of NO3- and total suspended particulate sulfate (SO4(TSP)2-) were evaluated at the South Pole from aerosol samples collected weekly for approximately 10 months (26 January to 25 October) in 2002 and analyzed for their concentration and isotopic compositions. Aerosol NO3- was largely affected by snowpack emissions in which [NO3-] and delta N-15(NO3-) were highest (49.3 +/- 21.4 ng/m(3), n = 8) and lowest (-47.0 +/- 11.7 parts per thousand, n = 5), respectively, during periods of sunlight in the interior of Antarctica. The seasonal cycle of Delta O-17(NO3-) reflected tropospheric chemistry year-round with lower values observed during sunlight periods and higher values observed during dark periods, reflecting shifts from HOx- to O-3-dominated oxidation chemistry. SO4(TSP)2- concentrations were highest during austral summer and fall (86.7 +/- 73.7 ng/m(3), n = 18) and are indicated to be derived from dimethyl sulfide (DMS) emissions, as delta S-34(SO42-)((TSP)) values (18.5 +/- 1.0 parts per thousand, n = 10) were similar to literature delta S-34(DMS) values. The seasonal cycle of Delta O-17(SO42-)((TSP)) exhibited minima during austral summer (0.9 +/- 0.1 parts per thousand, n = 5) and maxima during austral fall (1.3 +/- 0.3 parts per thousand, n = 6) and austral spring (1.6 +/- 0.1 parts per thousand, n = 5), indicating a shift from HOx- to O-3-dominated chemistry in the atmospheric derived SO42- component. Overall, the budgets of NO3- and SO4(TSP)2- at the South Pole were complex functions of transport, localized chemistry, biological activity, and meteorological conditions, and these results will be important for interpretations of oxyanions in ice core records in the interior of Antarctica.

关键词： nitrate sulfate aerosols isotopes South Pole oxidation chemistry

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Characteristics and exposure risks of potential pathogens and toxic metal (loid)s in aerosols from wastewater treatment plants

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ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2019年 183卷 109543-000页

作者： Yang, Tang Han, Yunping Zhang, Mengzhu Xue, Song Li, Lin Liu, Junxin Qiu, Zhongping Chinese Acad Sci Res Ctr Ecoenvironm Sci State Key Lab Environm Aquat Chem Beijing 100085 Peoples R China Univ Chinese Acad Sci Natl Engn Lab VOCs Pollut Control Mat & Technol Beijing 101408 Peoples R China Beijing Mech Biol Treatment Engineer Co Ltd Beijing 100086 Peoples R China Longyan Univ Univ Engn Res Ctr Solid Waste Resource Utilizat Longyan 364012 Peoples R China Longyan Univ Fujian Prov Coll Longyan 364012 Peoples R China Southwest Jiaotong Univ Sch Life Sci & Engn Chengdu 611756 Sichuan Peoples R China

aerosols from wastewater treatment plants (WWTPs) are considered to be potentially hazardous to on-site employees and surrounding residents. However, their harmful components and their effects remain poorly understood. In this study, the characteristics, responsible factors, sources and exposure risks of potential pathogens and toxic metal(loid)s in aerosols from four WWTPs were investigated. There were 21 potential pathogens and 15 toxic metal(loid)s detected in the aerosols. Arcobacter and Fe were the dominant taxa responsible for the dissimilarity of the potential pathogen population and toxic metal(loid) composition between the aerosols and the wastewater/sludge, respectively. Both meteorological factors and sources affected pathogen and toxic metal(loid) composition. The potential pathogens and toxic metal(loid)s in indoor aerosols mainly originated from wastewater/sludge, while those in outdoor aerosols originated from wastewater/sludge and ambient air. The highest respirable fraction (< 3.30 mu m) concentrations and proportions were detected at the aeration units. Non-carcinogenic and carcinogenic risks of toxic metal(loid)s for both adults and children were found within and/or around WWTPs, and non-carcinogenic risks of bacteria for children were found at downwind, suggesting the need for active safeguard procedures, such as that employees wear masks and work clothes, covering the main emission sites, and collecting and destroying of aerosols.

关键词： Wastewater treatment plants aerosols Potential pathogens Toxic metal(loid)s Risk assessment

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Climate Forcing and Response to Greenhouse Gases, aerosols, and Ozone in CESM1

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JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES 2019年第24期124卷 13876-13894页

作者： Zhao, Alcide Stevenson, David S. Bollasina, Massimo A. Univ Edinburgh Sch GeoSci Edinburgh Midlothian Scotland

It is crucial to reduce uncertainties in our understanding of the climate impacts of short-lived climate forcers, in the context that their emissions/concentrations are anticipated to decrease significantly in the coming decades worldwide. Using the Community Earth System Model (CESM1), we performed time-slice experiments to investigate the effective radiative forcing (ERF) and climate respons to 1970-2010 changes in well-mixed greenhouse gases (GHGs), anthropogenic aerosols, and tropospheric and stratospheric ozone. Once the present-day climate has fully responded to 1970-2010 changes in all forcings, both the global mean temperature and precipitation responses are twice as large as the transient ones, with wet regions getting wetter and dry regions drier. The temperature response per unit ERF for short-lived species varies considerably across many factors including forcing agents and the magnitudes and locations of emission changes. This suggests that the ERF should be used carefully to interpret the climate impacts of short-lived climate forcers. Changes in both the mean and the probability distribution of global mean daily precipitation are driven mainly by GHG increases. However, changes in the frequency distributions of regional mean daily precipitation are more strongly influenced by changes in aerosols, rather than GHGs. This is particularly true over Asia and Europe where aerosol changes have significant impacts on the frequency of heavy-to-extreme precipitation. Our results may help guide more reliable near-future climate projections and allow us to manage climate risks more effectively.

关键词： aerosols equilibrium climate response radiative forcing precipitation greenhouse gases ozone

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High-Nicotine Electronic Cigarette Products: Toxicity of JUUL Fluids and aerosols Correlates Strongly with Nicotine and Some Flavor Chemical Concentrations

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CHEMICAL RESEARCH IN TOXICOLOGY 2019年第6期32卷 1058-1069页

作者： Omaiye, Esther E. McWhirter, Kevin J. Luo, Wentai Pankow, James F. Talbot, Prue Univ Calif Riverside Environm Toxicol Grad Program Riverside CA 92521 USA Portland State Univ Dept Civil & Environm Engn Portland OR 97207 USA Portland State Univ Dept Chem Portland OR 97207 USA Univ Calif Riverside Dept Mol Cell & Syst Biol Riverside CA 92521 USA

Whereas JUUL electronic cigarettes (ECs) have captured the majority of the EC market, with a large fraction of their sales going to adolescents, little is known about their cytotoxicity and potential effects on health. The purpose of this study was to determine flavor chemical and nicotine concentrations in the eight currently marketed prefilled JUUL EC cartridges ("pods") and to evaluate the cytotoxicity of the different variants (e.g., "Cool Mint" and "Creme Brulee") using in vitro assays. Nicotine and flavor chemicals were analyzed using gas chromatography-mass spectrometry in pod fluid before and after vaping and in the corresponding aerosols. 59 flavor chemicals were identified in JUUL pod fluids, and 3 were >1 mg/mL. Duplicate pods were similar in flavor chemical composition and concentration. Nicotine concentrations (average 60.9 mg/mL) were significantly higher than those of any EC products we have previously analyzed. The transfer efficiency of individual flavor chemicals that were >1 mg/mL and nicotine from the pod fluid into aerosols was generally 35-80%. All pod fluids were cytotoxic at a 1:10 dilution (10%) in the MTT and neutral red uptake assays when tested with BEAS-2B lung epithelial cells. Most aerosols were cytotoxic in these assays at concentrations between 0.2 and 1.8%. The cytotoxicity of collected aerosol materials was highly correlated with nicotine and ethyl maltol concentrations and moderately to weakly correlated with total flavor chemical concentration and menthol concentration. Our study demonstrates that (1) some JUUL flavor pods have sufficiently high concentrations of flavor chemicals that may make them attractive to youth and (2) the concentrations of nicotine and some flavor chemicals (e.g., ethyl maltol) are high enough to be cytotoxic in acute in vitro assays, emphasizing the need to determine if JUUL products will lead to adverse health effects with chronic use.

关键词： aerosols Fluids Nicotine Flavor Toxicity

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Filtering performances of 20 protective fabrics against solid aerosols

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JOURNAL OF OCCUPATIONAL AND ENVIRONMENTAL HYGIENE 2019年第8期16卷 592-606页

作者： Wingert, Loic Cloutier, Yves Halle, Stephane Bahloul, Ali Tessier, Dominic Giraudel, Jean-Luc Dolez, Patricia Tuduri, Ludovic Inst Rech Robert Sauve Sante & Secur Travail PRCB Montreal PQ Canada Ecole Technol Super Dept Mech Engn Montreal PQ Canada Grp CTT St Hyacinthe PQ Canada Univ Bordeaux Equipe Rech LPTC UMR 5805 EPOC F-33405 Talence France Univ Alberta Dept Human Ecol Edmonton AB Canada

Workers can be exposed to solid airborne particles in some occupational environments, and they might be required to wear chemical protective clothing to prevent skin exposure. Dedicated standards exist to certify the protective value of such clothing, but they are not informative enough to identify the main pathways of entry for solid particles nor to compare performances between different chemical protective clothing. In this work, 20 non-woven fabrics used to make chemical protective clothing for solid particle protection were selected to be examined for both filtration and comfort performances. Nine were microporous fabrics (MP), 10 were multilayered nonwoven fibrous media (SMS) and one was a flash spun material (FS). To assess their filtration performances, fabrics were challenged in a benchtop wind tunnel with a 20-3,000nm diameter sodium chloride aerosol at three low fabric face velocities (0.05, 0.15, 0.3cm/sec). Airflow resistance and water vapor transmission rate were also measured to provide indications of comfort for the wearer. The penetration results led to the classification of the 20 fabrics into distinct groups of filtration efficiency. The data were analysed based on the porous media characteristics (thickness, fiber diameter, porosity, etc.). MPs were the most efficient fabrics, and SMSs showed a wide range of performances, mostly due to variations in the thickness of the filtering layer as well as to the fabric treatment. Measurements of airflow resistance and water vapor transmission rates revealed major differences between MPs and FSs and SMSs. This highlights the potential of some SMS fabrics to meet a compromise between protection and comfort.

关键词： aerosols chemical protective clothing filtration non-woven

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Assessing the spatial distribution of aerosols and air quality over the Ganga River basin during COVID-19 lockdown phase-1

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REMOTE SENSING APPLICATIONS-SOCIETY AND ENVIRONMENT 2021年 23卷

作者： Rani, Seema Kumar, Rajesh Acharya, Prasenjit Maharana, Pyarimohan Singh, Rajkumar Banaras Hindu Univ Inst Sci Dept Geog Varanasi 221005 Uttar Pradesh India Sikkim Univ Sch Human Sci Dept Geog Gangtok 737102 Sikkim India Vidyasagar Univ Dept Geog Midnapore 721102 W Bengal India Sri Sri Univ Fac Sci Cuttack 754006 Odisha India World Agroforestry ICRAF NASC Complex New Delhi 110012 India

The present study aims to analyze the variations in aerosol optical depth (AOD), black carbon (BC), organic carbon (OC), sulfate (SO4), dust, sea salt, fine mode dust and sea salt, and air quality over the Ganga River basin (GB), during the nation-wise lockdown phase-1 due to the outbreak of COVID-19. The aerosol data have been obtained from Moderate Resolution Imaging Spectroradiometer (MODIS) and Modern-Era Retrospective analysis for Research and Applications (MERRA-2) for the lockdown phase-1 (March 25 - April 15, 2020) and its corresponding average of the reference period (2001-2019). The total PM2.5 has been modeled over the GB based on the inputs from MERRA-2. The in-situ air quality index (AQI) values from cities across the GB have been obtained during pre-lockdown (February, 29 - March 20, 2020) and lockdown phase-1 period to evaluate changes. Non-parametric pairwise comparison is performed to evaluate the significant change in the pollutants including AOD, and quantile regression is used to explore the effect of meteorology on AOD and other pollutants. The results show a significant reduction (p <= 0.05) in AOD, BC, OC, SO4, dust, dust particulate matter (PM2.5), sea salt, sea salt PM2.5, and estimated total PM2.5 during the lockdown phase-1 with respect to the reference period. The analysis also reveals that meteorological factors do not play a vital role in the reduction of AOD during the lockdown phase-1 period. The estimated reductions for AOD, BC, OC, SO4, dust, dust PM2.5, sea salt, and sea salt PM2.5 are 33%, 21%, 24%, 20%, 18%, 17%, 64%, and 61%, respectively due to imposition of lockdown measures. As many as 28 cities in the GB have shown substantial improvement in the air quality during the lockdown phase-1 period. The reduction in the emission quantity and subsequent improvement in AQI has opened up a new discourse for combatting the persistent air quality issues for million-plus cities in particular and for the north Indian plain in general. The

关键词： aerosols Air quality index Ganga river basin COVID-19 lockdown phase-1 Estimated total PM2.5 surface mass concentrations

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Effects of aerosols on the Precipitation of Convective Clouds: A Case Study in the Yangtze River Delta of China

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JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES 2019年第14期124卷 7868-7885页

作者： Liu, Chong Wang, Ti-Jian Chen, Pu-Long Li, Meng-Meng Zhao, Ming Zhao, Kun Wang, Ming-Huai Yang, Xiu-Qun Nanjing Univ Sch Atmospher Sci Nanjing Jiangsu Peoples R China Minist Educ Key Lab Mesoscale Severe Weather Nanjing Jiangsu Peoples R China CMA NJU Joint Lab Climate Predict Studies Nanjing Jiangsu Peoples R China

Aerosol is a critical factor affecting the atmospheric hydrological cycle and climate change. Acting as cloud condensation nuclei for cloud formation, aerosols have a significant impact on regional precipitation. This study uses the fully coupled chemistry module (Weather Research and Forecasting/Chem) within the Weather Research and Forecasting model to simulate convective cloud precipitation in the Yangtze River Delta of China. To investigate the impact of on precipitation, four numerical experiments are conducted. The base case uses the full emission inventory (which we call the 100% case), and the other three cases are designed based on reduced emissions for different percentages (which we call the 50% case, the 10% case, and the 1% case). Compared to the other cases, the grid point hour maximum precipitation of the 50% case is the largest, which can reach 44.1 mm/hr and has an increase of 5% over the 100% case. The strongest precipitation is delayed by about 1 hr in the 50% case, and precipitation area is increased by 6.5%. This study indicates that the influence of aerosols on regional precipitation is a nonlinear process, with a correlation coefficient of 0.52 (p < 0.01) showing a strong positive correlation between cloud condensation nuclei (>250 cm(-3), height of 0.5-3 km) and precipitation. Further analysis of the dynamics and microphysical processes of this convective precipitation shows that the 50% case has an area with higher rising velocity and bigger cloud water mixing ratio than the other cases but has a relatively low convective center. The formation of precipitation is mainly influenced by the accretion of snow by rain, but the role of the snow melting into rain cannot be ignored.

关键词： aerosols cloud condensation nuclei convective cloud precipitation WRF-Chem

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Anthropogenic fine aerosols dominate over the Pune region, Southwest India

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METEOROLOGY AND ATMOSPHERIC PHYSICS 2019年第5期131卷 1497-1508页

作者： Gawhane, R. D. Rao, P. S. P. Budhavant, Krishnakant Meshram, D. C. Safai, P. D. Indian Inst Trop Meteorol Pune 411008 Maharashtra India Stockholm Univ Dept Environm Sci & Analyt Chem ACES S-10691 Stockholm Sweden Savitribai Phule Pune Univ Dept Geol Pune 411007 Maharashtra India

The major water-soluble ions, organic carbon (OC), elemental carbon (EC) and mass concentration of fine- (PM2.5) and coarse-mode (PM10-2.5) aerosols were measured at Pune during January-December 2016. The mass closure approach was used by comparing the sum of the masses of the individual chemical species to the gravimetric PM obtained by weighting the filter samples. The 1 year mean total mass concentration of fine and coarse mode was 40 mu gm(-3) (64%) and 23 mu g m(-3) (36%), respectively. The PM2.5/PM10 ratio was 0.64 +/- 0.9 indicating an abundance of fine-mode particles over Pune during the study period. A principal component analysis identified three components, where the one with highest explanatory power (59%) displayed clear impact of anthropogenic sources on the measured mass concentration of a majority of the compounds. The strong linear relationships between EC, OC, nss-SO42- and nss-K+ suggest a predominance of a common primary source, with a contribution from biofuel as well as biomass burning sources. Keeping the strong correlation and sources of individual chemical species as the base, it was noticed that (1) major contributors to fine- and coarse-mode particles over the Pune regions are carbonaceous aerosols and secondary inorganic aerosols (non-sea-salt SO42-, NO3-, and NH4+), (2) anthropogenic aerosols contribute mostly to the fine-mode, and (3) meteorological parameters play an important role in controlling levels of fine- and coarse-mode particles. Taken together, the study clearly indicates the dominance of anthropogenic sources during the entire year with more significance in the winter season.

关键词： aerosols Organic carbon Meteorological parameters Gravimetry Biomass burning Anthropogenic factors Human influences Principal components analysis Chemical speciation Organic chemistry Burning Incineration Mass Particulate matter Abundance Species Biofuels

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Potential effects of aerosols on the diurnal cycle of precipitation over Central Africa by RegCM4.4

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SN APPLIED SCIENCES 2019年第2期1卷 1-16页

作者： Mbienda, A. J. Komkoua Guenang, G. M. Tanessong, R. S. Sandjon, A. Tchakoutio Univ Dschang Fac Sci Dept Phys Lab Mech & Modeling Phys Syst POB 67 Dschang Cameroon Univ Yaounde I Fac Sci Dept Phys Lab Environm Modeling & Atmospher Phys Yaounde Cameroon Univ Dschang Fac Agron & Agr Sci Sch Wood Water & Nat Resources Dschang Cameroon Univ Buea Higher Teacher Tech Sch Buea Cameroon

In this study, we examine the potential influence of aerosols on the diurnal cycle of precipitation over Central Africa by analysing 5-year simulations performed with the version 4.4 of the Abdus Salam International Centre of Theoretical Physics model (RegCM4.4). Two sets of 6 years from January 2001 to December 2006 were simulated at a 40-km horizontal grid with 1 year for spin-up. Overall, our results indicate that the simulated seasonal aerosol loads are underestimated everywhere over the study domain compared to MODIS total aerosol optical depth retrieval, except the northern part encompassing Sahel region characterized by an occurrence of dust aerosols loading coming from the Sahelian region in West Africa. The model diurnal precipitation was evaluated against the TRMM 3B42 rainfall product. The diurnal evolution of precipitation reveals that the model represents the general pattern, but always with very low values peculiarly in the late afternoon. Over the rainy area, amplitude of precipitation is systematically affected by either a reduction or an increase by up to +/- 20% and +/- 40% during DJF and JAS, respectively. Scattering and absorption of solar radiation by aerosols can explain the reduction in diurnal amplitude of *** time of maximum precipitation is not really affected during both seasons over the major part of rainy area.

关键词： RegCM4.4 aerosols Radiative forcing Diurnal cycle

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