Explore the vast range of titles available.

The ongoing outbreak of coronavirus disease 2019 (COVID-19) has spread rapidly on a global scale. Although it is clear that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is transmitted through human respiratory droplets and direct contact, the potential for aerosol transmission is poorly understood 1 – 3 . Here we investigated the aerodynamic nature of SARS-CoV-2 by measuring viral RNA in aerosols in different areas of two Wuhan hospitals during the outbreak of COVID-19 in February and March 2020. The concentration of SARS-CoV-2 RNA in aerosols that was detected in isolation wards and ventilated patient rooms was very low, but it was higher in the toilet areas used by the patients. Levels of airborne SARS-CoV-2 RNA in the most public areas was undetectable, except in two areas that were prone to crowding; this increase was possibly due to individuals infected with SARS-CoV-2 in the crowd. We found that some medical staff areas initially had high concentrations of viral RNA with aerosol size distributions that showed peaks in the submicrometre and/or supermicrometre regions; however, these levels were reduced to undetectable levels after implementation of rigorous sanitization procedures. Although we have not established the infectivity of the virus detected in these hospital areas, we propose that SARS-CoV-2 may have the potential to be transmitted through aerosols. Our results indicate that room ventilation, open space, sanitization of protective apparel, and proper use and disinfection of toilet areas can effectively limit the concentration of SARS-CoV-2 RNA in aerosols. Future work should explore the infectivity of aerosolized virus. Aerodynamic analysis of SARS-CoV-2 RNA in two hospitals in Wuhan indicates that SARS-CoV-2 may have the potential to be transmitted through aerosols, although the infectivity of the virus RNA was not established in this study.

Atmospheric particulates can be produced by emissions or form de novo. New particle formation usually occurs in relatively clean air. This is because preexisting particles in the atmosphere will scavenge the precursors of new particles and suppress their formation. However, observations in some heavily polluted megacities have revealed substantial rates of new particle formation despite the heavy loads of ambient aerosols. Yao et al. investigated new particle formation in Shanghai and describe the conditions that make this process possible. The findings will help inform policy decisions about how to reduce air pollution in these types of environments. Science , this issue p. 278 Atmospheric new particle formation in heavily polluted cities can occur in certain chemical environments. Atmospheric new particle formation (NPF) is an important global phenomenon that is nevertheless sensitive to ambient conditions. According to both observation and theoretical arguments, NPF usually requires a relatively high sulfuric acid (H 2 SO 4 ) concentration to promote the formation of new particles and a low preexisting aerosol loading to minimize the sink of new particles. We investigated NPF in Shanghai and were able to observe both precursor vapors (H 2 SO 4 ) and initial clusters at a molecular level in a megacity. High NPF rates were observed to coincide with several familiar markers suggestive of H 2 SO 4 –dimethylamine (DMA)–water (H 2 O) nucleation, including sulfuric acid dimers and H 2 SO 4 -DMA clusters. In a cluster kinetics simulation, the observed concentration of sulfuric acid was high enough to explain the particle growth to ~3 nanometers under the very high condensation sink, whereas the subsequent higher growth rate beyond this size is believed to result from the added contribution of condensing organic species. These findings will help in understanding urban NPF and its air quality and climate effects, as well as in formulating policies to mitigate secondary particle formation in China.

Atmospheric ammonia (NH 3 ) has great environmental implications due to its important role in ecosystem and global nitrogen cycle, as well as contribution to secondary particle formation. Here, we report long-term continuous measurements of NH 3 at different locations (i.e. urban, industrial and rural) in Shanghai, China, which provide an unprecedented portrait of temporal and spatial characteristics of atmospheric NH 3 in and around this megacity. In addition to point emission sources, air masses originated from or that have passed over ammonia rich areas, e.g. rural and industrial sites, increase the observed NH 3 concentrations inside the urban area of Shanghai. Remarkable high-frequency NH 3 variations were measured at the industrial site, indicating instantaneous nearby industrial emission peaks. Additionally, we observed strong positive exponential correlations between NH 4 + /(NH 4 + +NH 3 ) and sulfate-nitrate-ammonium (SNA) aerosols, PM 2.5 mass concentrations, implying a considerable contribution of gas-to-particle conversion of ammonia to SNA aerosol formation. Lower temperature and higher humidity conditions were found to favor the conversion of gaseous ammonia to particle ammonium, particularly in autumn. Although NH 3 is currently not included in China’s emission control policies of air pollution precursors, our results highlight the urgency and importance of monitoring gaseous ammonia and improving its emission inventory in and around Shanghai.

To compare the efficacy and safety of bismuth-containing quadruple therapy with tetracycline or amoxicillin for rescue treatment of Helicobacter pylori. The study was a non-inferiority trial of H. pylori eradication with at least two previous treatment failures. Subjects were randomized to receive 14-day therapy with b.i.d. lansoprazole 30 mg and bismuth 220 mg, plus metronidazole 400 mg q.i.d and amoxicillin 1 g t.i.d (amoxicillin group) or tetracycline 500 mg q.i.d (tetracycline group). Antimicrobial susceptibility was assessed by the agar-dilution method. Primary outcome was H. pylori eradication at 6 weeks after treatment. In all, 312 subjects were randomized, 13 were lost to follow-up; 29 violated the protocol. The intention-to-treat, per-protocol, and modified intention-to-treat eradication rates were (amoxicillin) 88.5% (138/156, 95% confidence interval (CI) 83.4-93.5%), 93.7% (133/142, 95% CI 89.7-97.7%), and 92.6% (138/149, 95% CI 88.4-96.8%). With tetracycline, they were 87.2% (136/156, 95% CI 81.9-92.4%), 95.3% (122/128, 95% CI 91.7-99.0%), and 90.7% (136/150, 95% CI 86.0-95.3%). Amoxicillin-, tetracycline-, and metronidazole-resistant rates were 8.3, 1.0, and 87.8%, respectively. Non-inferiority was confirmed (P<0.025). Metronidazole resistance did not affect the efficacy of either therapy. Compliance was greater and moderate and severe adverse events were less among those receiving amoxicillin than those receiving tetracycline. The novel bismuth-containing quadruple therapy with metronidazole and amoxicillin is an alternative to classical bismuth quadruple therapy for H. pylori rescue treatment as it provides similar eradication with superior safety and compliance.

Growing shipping activities in port areas have generated negative impacts on climate, air quality and human health. To better evaluate the environmental impact of ship emissions, an experimental characterization of air pollution from ships was conducted in Shanghai Port in the summer of 2016. The ambient concentrations of gaseous NO, NO2, SO2 and O3 in addition to fine particulate matter concentrations (PM2.5), particle size distributions and the chemical composition of individual particles from ship emission were continuously monitored for 3 months. Ship emission plumes were visible at the port site in terms of clear peaks in the gaseous species and particulate matter concentrations. The SO2 and vanadium particle numbers were found to correlate best with ship emissions in Shanghai Port. Single-particle data showed that ship emission particles at the port site mainly concentrated in a smaller size range (<0.4 µm), where their number contributions were more important than their mass contributions to ambient particulate matter. The composition of ship emission particles at the port site suggested that they were mostly freshly emitted particles: their mass spectra were dominated by peaks of sulfate, elemental carbon (EC), and trace metals such as V, Ni, Fe and Ca, in addition to displaying very low nitrate signals. The gaseous NOx composition in some cases of plumes showed evidence of atmospheric transformation by ambient O3, which subsequently resulted in O3 depletion in the area. Quantitative estimations in this study showed that ship emissions contributed 36.4 % to SO2, 0.7 % to NO, 5.1 % to NO2, −0.9 % to O3, 5.9 % to PM2.5 and 49.5 % to vanadium particles in the port region if land-based emissions were included, and 57.2 % to SO2, 71.9 % to NO, 30.4 % to NO2, −16.6 % to O3, 27.6 % to PM2.5 and 77.0 % to vanadium particles if land-based emissions were excluded.

Identification of various emission sources and quantification of their contributions comprise an essential step in formulating scientifically sound pollution control strategies. Most previous studies have been based on traditional offline filter analysis of aerosol major components (usually inorganic ions, elemental carbon – EC, organic carbon – OC, and elements). In this study, source apportionment of PM2.5 using a positive matrix factorization (PMF) model was conducted for urban Shanghai in the Yangtze River Delta region, China, utilizing a large suite of molecular and elemental tracers, together with water-soluble inorganic ions, OC, and EC from measurements conducted at two sites from 9 November to 3 December 2018. The PMF analysis with inclusion of molecular makers (i.e., MM-PMF) identified 11 pollution sources, including 3 secondary-source factors (i.e., secondary sulfate; secondary nitrate; and secondary organic aerosol, SOA, factors) and 8 primary sources (i.e., vehicle exhaust, industrial emission and tire wear, industrial emission II, residual oil combustion, dust, coal combustion, biomass burning, and cooking). The secondary sources contributed 62.5 % of the campaign-average PM2.5 mass, with the secondary nitrate factor being the leading contributor. Cooking was a minor contributor (2.8 %) to PM2.5 mass while a significant contributor (11.4 %) to the OC mass. Traditional PMF analysis relying on major components alone (PMFt) was unable to resolve three organics-dominated sources (i.e., biomass burning, cooking, and SOA source factors). Utilizing organic tracers, the MM-PMF analysis determined that these three sources combined accounted for 24.4 % of the total PM2.5 mass. In PMFt, this significant portion of PM mass was apportioned to other sources and thereby was notably biasing the source apportionment outcome. Backward trajectory and episodic analysis were performed on the MM-PMF-resolved source factors to examine the variations in source origins and composition. It was shown that under all episodes, secondary nitrate and the SOA factor were two major source contributors to the PM2.5 pollution. Our work has demonstrated that comprehensive hourly data of molecular markers and other source tracers, coupled with MM-PMF, enables examination of detailed pollution source characteristics, especially organics-dominated sources, at a timescale suitable for monitoring episodic evolution and with finer source breakdown.

Ammonia in the atmosphere is essential for the formation of fine particles that impact air quality and climate. Despite extensive prior research to disentangle the relationship between ammonia and haze pollution, the role of ammonia in haze formation in high ammonia-emitting regions is still not well understood. Aiming to better understand secondary inorganic aerosol (sulfate, nitrate, ammonium – SNA) formation mechanisms under high-ammonia conditions, 1-year hourly measurement of water-soluble inorganic species (gas and particle) was conducted at a rural supersite in Shanghai. Exceedingly high levels of agricultural ammonia, constantly around 30 µg m−3, were observed. We find that gas-particle partitioning of ammonia (ε(NH4+)), as opposed to ammonia concentrations, plays a critical role in SNA formation during the haze period. From an assessment of the effects of various parameters, including temperature (T), aerosol water content (AWC), aerosol pH, and activity coefficient, it seems that AWC plays predominant regulating roles for ε(NH4+). We propose a self-amplifying feedback mechanism associated with ε(NH4+) for the formation of SNA, which is consistent with diurnal variations in ε(NH4+), AWC, and SNA. Our results imply that a reduction in ammonia emissions alone may not reduce SNA effectively, at least at rural agricultural sites in China.

To control the spread of COVID-19, China has imposed national lockdown policies to restrict the movement of its population since the Chinese New Year of January 2020. In this study, we quantitatively analyzed the changes of pollution sources in Shanghai during the COVID-19 lockdown; a high-resolution emission inventory of typical pollution sources including stationary source, mobile source, and oil and gas storage and transportation source was established based on pollution source data from January to February 2020. The results show that the total emissions of sulfur dioxide (SO 2 ), nitrogen oxides (NO x ), particulate matter (PM), and volatile organic compounds (VOCs) were 9520.2, 37,978.6, 2796.7, and 7236.9 tons, respectively, during the study period. Affected by the COVID-19 lockdown, the mobile source experienced the largest decline. The car mileage and oil sales decreased by about 80% during the COVID-19 lockdown (P3) when compared with those during the pre-Spring Festival (P1). The number of aircraft activity decreased by approximately 50%. The impact of the COVID-19 epidemic on industries such as iron and steel and petrochemicals was less significant, while the greater impact was on coatings, chemicals, rubber, and plastic. The emissions of SO 2 , NO x , PM 2.5 , and VOCs decreased by 11%, 39%, 37%, and 47%, respectively, during P3 when compared with those during P1. The results show that the measures to control the spread of the COVID-19 epidemic made a significant contribution to emission reductions. This study may provide a reference for other countries to assess the impact of the COVID-19 epidemic on emissions and help establish regulatory actions to improve air quality.

Speciated atmospheric mercury including gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM), and particulate-bound mercury (PBM) were measured continuously for a 1-year period at a suburban site, representing a regional transport intersection zone, in east China. Annual mean concentrations of GEM, PBM, and GOM reached 2.77 ng m−3, 60.8 pg m−3, and 82.1 pg m−3, respectively. GEM concentrations were elevated in all the seasons except autumn. High mercury concentrations were related to winds from the south, southwest, and north of the measurement site. Combining analysis results from using various source apportionment methods, it was found that GEM concentration was higher when quasi-local sources dominated over long-range transport. Six source factors belonging to the anthropogenic sources of GEM were identified, including the common sectors previously identified (industrial and biomass burning, coal combustion, iron and steel production, cement production, and incineration), as well as an additional factor of shipping emissions (accounting for 19.5 % of the total), which was found to be important in east China where marine vessel shipping activities are intense. Emissions of GEM from natural surfaces were also found to be as important as those from anthropogenic sources for GEM observed at this site. Concurrences of high GOM concentrations with elevated O3 and temperature, along with the lagged variations in GEM and GOM during daytime demonstrated that the very high GOM concentrations were partially ascribed to intense in situ oxidation of GEM. Strong gas–particle partitioning was also identified when PM2.5 was above a threshold value, in which case GOM decreased with increasing PM2.5.

The intensive monitoring of air pollutants has led to the acquisition of vast quantities of data. Traditional quality control methods based on existing knowledge may be inefficient because of our limited understanding regarding the interaction of human activities and stochastic environmental factors. Moreover, traditional methods for outlier detection may be misleading because of the existence of valid outliers and invalid inliers. In this research, artificial neural networks (ANNs) are developed to identify instrument failure based on current and historical observations. Two structures, i.e., multilayer perceptrons and recurrent networks, are trained using 50,000 hourly data points labeled by human reviewers. The most conservative model identified 57.5% of the invalid sulfur compound observations and 44.9% of the invalid nitrogen compound observations. By setting a more liberal threshold, these values increased to 76.0% and 79.7%, respectively. Except for SO2, the ANNs outperformed the traditional methods for data quality control, as demonstrated with a plausibility test, a test of temporal consistency and a residential analysis. Compared with the test of temporal consistency, which was the most effective traditional method studied, the true positive rates of the ANNs were 19.4% to 29.5% higher for all pollutants except SO2, given the same false positive rates. The results indicate the effectiveness of ANNs for data quality control even without supplementary information. Methods for performance improvement are discussed.