Researchers must find the particles that are most dangerous to health in each place so policies can reduce levels of those pollutants first, urge Xiangdong Li and colleagues. Researchers must find ...the particles that are most dangerous to health in each place so policies can reduce levels of those pollutants first, urge Xiangdong Li and colleagues.
This study numerically investigated the thermal effect of human body on the time-dependent dispersion of cough droplets with evaporation process. The thermal flow of human body was imitated using a ...3D thermal manikin with real body features, while a recent developed multi-component Eulerian-Lagrangian approach was used to address the effects of inhomogeneous temperature and humidity fields on droplet evaporation. By comparing the results yielded without and with the human body heat, the outcomes demonstrated strong impact of human body heat on the droplets mass fraction and local air velocity distributions. Inspirable droplets could potentially drop into respirable droplets by evaporation, although the evaporation rate was not significantly affected by body heat. The thermal effect of human body revealed its vital impacts on the time-dependent droplets dispersion. Due to the buoyancy driven thermal flow, both the vertical velocity and displacement of small droplets (≤20 μm) were completely reversed from descending to ascending, while the deposition time of large droplets (≥50 μm) were significantly delayed. With the reduced droplet size by evaporation and droplets lifted into breathing zone by human thermal effect, the inhalability and infection risks of cough droplets would be much higher in real occupied indoor spaces.
•Inspirable droplets could drop into respirable droplets through evaporation process.•Human body heat strongly affects the local droplets mass fraction.•Evaporation rate is not sensitive to human body heat but to the RH and droplet size.•Cough droplets could be lifted to breathing zone by buoyancy driven thermal flow.•Human thermal effect promotes evaporation process by delaying droplets deposition.
Fine particle (PM2.5) samples were collected simultaneously at three urban sites (Shanghai, Nanjing, and Hangzhou) and one rural site near Ningbo in the Yangtze River Delta (YRD) region, China, on a ...weekly basis from September 2013 to August 2014. In addition, high-frequency daily sampling was conducted in Shanghai and Nanjing for one month during each season. Severe regional PM2.5 pollution episodes were frequently observed in the YRD, with annual mean concentrations of 94.6 ± 55.9, 97.8 ± 40.5, 134 ± 54.3, and 94.0 ± 57.6 μg m−3 in Shanghai, Nanjing, Hangzhou, and Ningbo, respectively. The concentrations of PM2.5 and ambient trace metals at the four sites showed clear seasonal trends, with higher concentrations in winter and lower concentrations in summer. In Shanghai, similar seasonal patterns were found for organic carbon (OC), elemental carbon (EC), and water-soluble inorganic ions (K+, NH4+, Cl−, NO3−, and SO42-). Air mass backward trajectory and potential source contribution function (PSCF) analyses implied that areas of central and northern China contributed significantly to the concentration and chemical compositions of PM2.5 in Shanghai during winter. Three heavy pollution events in Shanghai were observed during autumn and winter. The modelling results of the Nested Air Quality Prediction Modeling System (NAQPMS) showed the sources and transport of PM2.5 in the YRD during the three pollution processes. The contribution of secondary species (SOC, NH4+, NO3−, and SO42-) in pollution event (PE) periods was much higher than in BPE (before pollution event) and APE (after pollution event) periods, suggesting the importance of secondary aerosol formation during the three pollution events. Furthermore, the bioavailability of Cu, and Zn in the wintertime PM2.5 samples from Shanghai was much higher during the pollution days than during the non-pollution days.
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Secondary aerosol formation is important and the bioavailability of trace metals is much higher during the pollution events.
The synthesis of 5‐(cyano)dibenzothiophenium triflate 9, prepared by activation of dibenzob,dthiophene‐5‐oxide with Tf2O and subsequent reaction with TMSCN is reported, and its reactivity as ...electrophilic cyanation reagent evaluated. The scalable preparation, easy handling and broad substrate scope of the electrophilic cyanation promoted by 9, which includes amines, thiols, silyl enol ethers, alkenes, electron rich (hetero)arenes and polyaromatic hydrocarbons, illustrate the synthetic potential of this reagent. Importantly, Lewis acid activation of the reagent is not required for the transfer process. We additionally report herein biomimetic cyanocyclization cascade reactions, which are not promoted by typical electrophilic cyanation reagents, demonstrating the superior ability of 9 to trigger challenging transformations.
Perfidious to its nature: The synthesis of 5‐(cyano)dibenzothiophenium triflate is reported. In this compound, the umpolung of the cyano moiety is so efficient that this group can not only be transferred to typical organic nucleophiles, but it is also capable to initiate cationic cyanocyclization cascades in appropriately designed substrates.
Environmental pollution due to uncontrolled e-waste recycling activities has been reported in a number of locations of China. In the present study, metal pollution to the surrounding environment from ...a primitive e-waste processing facility was investigated. Soils at sites where e-waste is burned in the open air, those of surrounding paddy fields and vegetable gardens, as well as common vegetable samples were collected and analyzed for heavy metals. The results showed that the soils of former incineration sites had the highest concentrations of Cd, Cu, Pb, and Zn with mean values of 17.1, 11,140, 4500, and 3690mgkg−1, respectively. The soils of nearby paddy fields and vegetable gardens also had relatively high concentrations of Cd and Cu. In the edible tissues of vegetables, the concentrations of Cd and Pb in most samples exceeded the maximum level permitted for food in China. Sequential leaching tests revealed that the Cu, Pb, and Zn were predominantly associated with the residual fraction, followed by the carbonate/specifically adsorbed phases with the exception of Cd, which was mainly in the extractable form in paddy fields and vegetable soils. The data showed that uncontrolled e-waste processing operations caused serious pollution to local soils and vegetables. The cleaning up of former incineration sites should be a priority in any future remediation program.
As an important reservoir of intrinsic antimicrobial resistance, soil is subjected to increasing anthropogenic activities that creates sustained selection pressure for the prevalence of antibiotic ...resistance genes (ARGs), thus constituting an important environmental dissemination pathway to human exposure. This study investigated the levels and spatial distributions of three classes of ARGs in relation to a range of co-occurring chemical mixtures and soil properties at a regional scale of the Yangtze River Delta (YRD), China. The selected eight ARGs were all detected in 241 agricultural soil samples with relative abundances ranging from 1.01 × 10−7 to 2.31 × 10−1 normalized to the 16S rRNA gene. The sulII and tetG were the dominant ARGs with a mean relative abundance of 6.67 × 10−3 and 5.25 × 10−3, respectively. The ARGs were mainly present in agricultural soils alongside Taihu Lake and Shanghai municipality, the most agriculturally and economically vibrant area of the YRD region. Antibiotics, rather than other co-occurring pollutants and soil properties, remain to be the dominant correlate to the ARGs, suggesting their co-introduction into the soils via irrigation and manure application or the sustained selection pressure of antibiotics from these sources for the proliferation of ARGs in the soils. While the current dataset provided useful information to assess the ARGs pollution for mitigation, future studies are warranted to reveal the complete picture on the potential transfer of antimicrobial resistance from soil to agricultural produces to human consumption and associated health implications.
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•Ubiquitous distribution of ARGs at high abundances in regional agricultural soils.•Hotspot areas of ARG pollution concentrated in the most agriculturally vibrant area.•Dominance of antibiotics over co-occurring pollutants and soil properties in ARG prevalence.
Knowledge of the origins and dissemination of antibiotic resistance genes (ARGs) is essential for understanding modern resistomes in the environment. The mechanisms of the dissemination of ARGs can ...be revealed through comparative studies on the metagenomic profiling of ARGs between relatively pristine and human-impacted environments. The deep ocean bed of the South China Sea (SCS) is considered to be largely devoid of anthropogenic impacts, while the Pearl River Estuary (PRE) in south China has been highly impacted by intensive human activities. Commonly used antibiotics (sulfamethazine, norfloxacin, ofloxacin, tetracycline, and erythromycin) have been detected through chemical analysis in the PRE sediments, but not in the SCS sediments. In the relatively pristine SCS sediments, the most prevalent and abundant ARGs are those related to resistance to macrolides and polypeptides, with efflux pumps as the predominant mechanism. In the contaminated PRE sediments, the typical ARG profiles suggest a prevailing resistance to antibiotics commonly used in human health and animal farming (including sulfonamides, fluoroquinolones, and aminoglycosides), and higher diversity in both genotype and resistance mechanism than those in the SCS. In particular, antibiotic inactivation significantly contributed to the resistance to aminoglycosides, β-lactams, and macrolides observed in the PRE sediments. There was a significant correlation in the levels of abundance of ARGs and those of mobile genetic elements (including integrons and plasmids), which serve as carriers in the dissemination of ARGs in the aquatic environment. The metagenomic results from the current study support the view that ARGs naturally originate in pristine environments, while human activities accelerate the dissemination of ARGs so that microbes would be able to tolerate selective environmental stress in response to anthropogenic impacts.
Antibiotic resistance genes (ARGs) are increasingly a focus of concern because they pose a potential health risk. The Pearl River (PR) and Pearl River Estuary (PRE) show a distinct gradient in ...anthropogenic impacts, in particular associated with the use of antibiotics, from the river, to the estuary, and on to the coast. In this study, two surveys were conducted in the PR and PRE areas during the winter and summer of 2011, respectively. Seven tet genes consisting of efflux pump (tetA, tetC, and tetH) and ribosomal protection proteins (tetB, tetM, tetO, and tetW) were analyzed using the polymerase chain reaction (PCR) technique. The tet genes, with the exception of tetA and tetH, were widely detected in the PR and PRE environments. The tet genes exhibited a trend of an increase in total concentration and diversity with the degree of anthropogenic impacts from the river to the coast, indicating that riverine input was the main source of ARGs in the region. Significant correlations were observed between tet genes and antibiotic concentrations, as well as among different environmental compartments (water and sediments). The distribution patterns of tet genes were similar between the potential sources of pollution and the highly-impacted sites, but were significantly different between less-impacted sites and highly-impacted ones or pollution sources. The results suggest that ARGs and antibiotics may be released from identical sources, and transported in a similar manner in estuary/coastal environments close to sources of pollution.
The relative distribution pattern of tet genes was a good indicator in differentiating anthropogenic sources of ARGs from the regional background. Display omitted
► Relative distribution of tet genes was related to anthropogenic impacts. ► Transport from exogenous sources was the dominant process of ARGs in estuaries. ► ARGs can migrate among different environmental compartments. ► It is important to reduce/eliminate ARGs at pollution sources.
Airborne transmission is one of the environmental dissemination pathways of antibiotic resistance genes (ARGs), and has critical implications for human exposure through inhalation. In this study, we ...focused on three regions of China to reveal some unique spatiotemporal features of airborne bacteria and ARGs in fine aerosols (PM2.5): (1) greater seasonal variations in the abundance of bacteria and ARGs in temperate urban Beijing than in the subtropical urban areas of the Yangtze River Delta (YRD) and Pearl River Delta (PRD) regions, with regional disparities in bacterial communities; (2) geographical fingerprints of ARG profiles independent of seasonal cycles and land-use gradients within each region; (3) region-independent associations between the targeted ARGs and limited bacterial genera; (4) common correlations between ARGs and mobile genetic elements (MGEs) across regions; and (5) PM2.5 at the higher end of ARG enrichment across various environmental and human media. The spatiotemporally differentiated bacterial communities and ARG abundances, and the compositions, mobility, and potential hosts of ARGs in the atmosphere have strong implications for human inhalational exposure over spatiotemporal scales. By comparing other contributing pathways for the intake of ARGs (e.g., drinking water and food ingestion) in China and the U.S.A., we identified the region-specific importance of inhalation in China as well as country-specific exposure scenarios. Our study thus highlights the significance of inhalation as an integral part of the aggregate exposure pathways of environmentally disseminated ARGs, which, in turn, may help in the formulation of adaptive strategies to mitigate the exposure risks in China and beyond.
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