The COVID-19 epidemic broke out in Wuhan, Hubei in December 2019 and in January 2020 and was later transmitted to the entire country. Quarantine measures during Chinese New Year effectively ...alleviated the spread of the epidemic, but they simultaneously resulted in a decline in anthropogenic emissions from industry, transportation, and import and export of goods. Herein, we present the major chemical composition of non-refractory PM2.5 (NR-PM2.5) and the concentrations of gaseous pollutants in an urban site in Shanghai before and during the quarantine period of the COVID-19 epidemic, which was Jan. 8―23 and Jan. 24―Feb. 8, respectively. The observed results show that the reduction in PM2.5 can be mainly attributed to decreasing concentrations of nitrate and primary aerosols. Nitrate accounted for 37% of NR-PM2.5 before the quarantine period when there was no emission reduction. During the quarantine period, the nitrate concentration decreased by approximately 60%, which is attributed to a reduction in the NOx concentration. Ammonium, as the main balancing cation, showed an approximately 45% simultaneous decrease in concentration. The concentrations of chloride and hydrocarbon-like organic aerosols from primary emissions also declined due to limited human activities. By contrast, sulphate and oxygenated organic aerosols showed a slight decrease in concentration, with their contributions increasing to 27% and 18%, respectively, during the quarantine period, which resulted in two pollution episodes with PM2.5 exceeding 100 μg/m3. This study provides a better understanding of the impact of quarantine measures on variations of the PM2.5 concentration and chemical compositions. Atmospheric oxidation capacities based on the oxidant (Ox = O3 + NO2) and oxidation ratios have been discussed for elucidating the source and formation of haze in an environment with lower anthropogenic emissions. With increasing contribution of secondary aerosols, lower NOx and nitrate concentrations did not completely avoid haze in Shanghai during the epidemic.
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•Quarantine measures led to a reduction in the concentrations of PM2.5, SO2, NOx, and CO in Shanghai.•Reduction in NOx led to increasing O3 and decreasing nitrate.•Reduction in PM2.5 is attributed to the decreasing concentrations of primary aerosols and nitrate.•The increasing contribution of sulphate and OOA inhibited further PM2.5 reduction.
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
. 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.
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
SO
) 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
SO
) and initial clusters at a molecular level in a megacity. High NPF rates were observed to coincide with several familiar markers suggestive of H
SO
-dimethylamine (DMA)-water (H
O) nucleation, including sulfuric acid dimers and H
SO
-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.
Abstract To control the spread of the 2019 novel coronavirus (COVID-19), China imposed nationwide restrictions on the movement of its population (lockdown) after the Chinese New Year of 2020, leading ...to large reductions in economic activities and associated emissions. Despite such large decreases in primary pollution, there were nonetheless several periods of heavy haze pollution in eastern China, raising questions about the well-established relationship between human activities and air quality. Here, using comprehensive measurements and modeling, we show that the haze during the COVID lockdown was driven by enhancements of secondary pollution. In particular, large decreases in NOx emissions from transportation increased ozone and nighttime NO3 radical formation, and these increases in atmospheric oxidizing capacity in turn facilitated the formation of secondary particulate matter. Our results, afforded by the tragic natural experiment of the COVID-19 pandemic, indicate that haze mitigation depends upon a coordinated and balanced strategy for controlling multiple pollutants.
High pollution episodes of PM2.5 and O3 were frequently observed at a rural site (N31.0935º, E120.978°) in eastern Yangtze River Delta (YRD) in summer. To study the impacts of photochemical reactions ...on secondary aerosol formation in this region, we performed real-time measurements of the mass concentration and composition of PM2.5, particle size distribution (13.6~736.5 nm), concentrations of gas pollutants including O3, SO2, NO2, CO, non-methane hydrocarbons (NMHC)), and nitrate radical in 2013. During the sampling period, the average concentration of PM2.5 was 76.1 (± 16.5) μg/m3, in which secondary aerosol species including sulfate, nitrate, ammonium, and secondary organic aerosol (SOA) accounted for ~ 62%. Gas-phase oxidation of SO2 was mainly responsible for a fast increase of sulfate (at 1.70 μg/m3/h) in the morning. Photochemical production of nitric acid was intense during daytime, but particulate nitrate concentration was low in the afternoon due to high temperature. At night, nitrate was mainly formed through the hydrolysis of NO3 and/or N2O5. The correlations among NMHC, Ox (= O3 + NO2), and SOA suggested that a combination of high emission of hydrocarbons and active photochemical reactions led to the rapid formation of SOA. In addition, several new particle formation and fast growth events were observed despite high ambient aerosol loading. Since the onset of new particle events was accompanied by a rapid increase of H2SO4 and SOA, enhanced formation of sulfate and SOA driven by photochemical oxidation likely promoted the formation and growth of new particles. Together, our results demonstrated that strong atmospheric photochemical reactions enhanced secondary aerosols formation and led to the synchronous occurrence of high concentrations of PM2.5 and O3 in a regional scale. These findings are important for better understanding the air pollution in summer in YRD.
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•High pollution episodes of both PM2.5 and O3 were observed in summer in YRD.•Formation mechanisms of secondary aerosol were studied by real-time measurement.•Secondary aerosol formation was enhanced by photochemical reactions.•New particle formation and growth was observed despite high aerosol loading.•Control measures for PM2.5 and O3 must be considered holistically in YRD.
To investigate composition characteristics and assess occupational health risks and odor pollution of volatile organic compounds (VOCs) from industrial activities in the Yangtze River Delta (YRD) ...region, China, one-year field measurements of VOCs were conducted simultaneously at an iron and steel industrial park (ISP), one chemical industrial park (CMP) and one petrochemical industrial park (PCP) from September, 2018 to August, 2019. The concentrations of VOCs were 80.2 ± 67.9 ppbv, 28.1 ± 27.2 ppbv and 144 ± 378 ppbv for ISP, CMP and PCP, respectively. Aromatics, alkanes and alkenes were the major components of VOCs at ISP, CMP and PCP, respectively. Moreover, the toluene to benzene ratios were 0.330 ± 0.302, 4.31 ± 6.48 and 1.84 ± 3.34, which generally showed the characteristics of combustion source for ISP, industrial activities for CMP and petrochemical industry for PCP, respectively. The hazard index values were 0.752 ± 0.438, 0.108 ± 0.248 and 0.090 ± 0.260 at ISP, CMP and PCP, which were generally lower than threshold limit value, suggesting a low noncarcinogenic risk for workers. Meanwhile, the 95th percentile LCR values of VOCs were 8.76 × 10−5, 1.15 × 10−5 and 1.00 × 10−5 at ISP, CMP and PCP, respectively, which were also under acceptable risk level, indicating a low carcinogenic risk. Benzene and 1,3-butadiene were main harmful substances for both noncarcinogenic and carcinogenic risks of VOCs. The odor levels of VOCs were 2.12 ± 4.21, 12.5 ± 28.7 and 1.01 ± 7.84 at ISP, CMP and PCP, respectively. Aromatics for ISP and sulfide compounds for CMP and PCP were primary pollutants for odor pollution. This work could improve the understanding of risk levels and odor characteristics of VOCs and benefit policy development on alleviating odor complaints and health risks for workers in YRD region, China.
•Toluene to benzene ratios showed the source characteristics on these industries.•Primary odorants were aromatics for ISP and sulfide compounds for CMP and PCP.•VOCs generally showed the low noncarcinogenic and carcinogenic risks levels.•Benzene and 1,3-butadiene were primary harmful substances for VOCs.
Ground-based multi-axis differential optical absorption spectroscopy (MAX-DOAS) observations were performed from 27 December 2018 to 16 January 2019 in Changshou, one of subdistricts of Chongqing, ...China. Primary atmospheric pollutant in Changshou during wintertime was PM2.5, whose contribution averaged about 70.15% ± 9.5% of PM10. The ratio of PM2.5/PM10 decreased when PM2.5 pollution became worse, and it should attribute to biomass burning and the contribution of hygroscopic growth and enhanced heterogeneous chemistry under high relative humidity condition. Moreover, nitrogen dioxide (NO2), formaldehyde (HCHO) and glyoxal (CHOCHO) vertical profiles during the campaign period were retrieved separately. TROPOMI HCHO vertical column densities (VCDs) and MAX-DOAS HCHO VCDs were correlated well (R = 0.93). In order to identify the sources of volatile organic compound (VOC) in Changshou, the ratio of CHOCHO to HCHO (RGF) in five different layers were estimated. The estimated daily averaged RGF were 0.0205 ± 0.0077, 0.0727 ± 0.0286, 0.0864 ± 0.0296, 0.0770 ± 0.0275 and 0.0746 ± 0.0263 in 0–100 m, 100–200 m, 300–400 m, 500–600 m and 700–800 m layers, respectively. The estimated RGF will increase when biomass burnings were dominated. Using NO2 as a tracer of anthropogenic emissions, we found the RGF values gradually decrease with the increase of NO2 levels. RGF values in 0–100 m layer and all the other upper layers are 0.015–0.025 and 0.06–0.14, and that means the dominant sources of VOCs in 0–100 m layer and all the other upper layers are biogenic emission and anthropogenic emission (especially biomass burning), respectively. In addition, we found that RGF has site dependence which is in compliance with several previous studies.
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•The ratio of PM2.5/PM10 decreased when PM2.5 pollution became worse•HCHO and CHCOHO mainly distributed in 0-100 m and 100-200 m, respectively.•The sources of VOCs above 100 m are mainly from biomass burning.
Joint field observations were conducted from October to November in 2011 to observe haze pollution in the Yangtze River Delta (YRD), China. Samples of particulate matter with diameter less than ...2.5 μm (PM2.5) and less than 10 μm (PM10), gaseous pollutants and meteorology data were collected in five cities – Shanghai, Suzhou, Nanjing, Ningbo and Hangzhou – in the YRD. The chemical composition of PM2.5 was analyzed and the light extinction resulting from each chemical species was calculated using the IMPROVE algorithm. A typical heavy haze episode was selected and the chemical mass balance (CMB) model was applied to identify the sources of PM2.5. The average PM2.5 and PM10 mass concentrations during the haze episode were 100 ± 24 μg/m3 and 164 ± 19 μg/m3, respectively; visibility decreased to 1 km. Organic matter (OM), sulfate, nitrate, and ammonium were the dominant components of PM2.5, accounting for 33%, 19%, 17% and 11% of PM2.5 mass, respectively. Sulfate, OM and nitrate had the highest impact on light extinction, contributing 30%, 28% and 19%, respectively. The source apportionment indicate that PM2.5 is primarily from secondary pollutants and primary emissions from vehicles and biomass burning. A polluted air mass from north Jiangsu Province and stagnant meteorology further aggravated the haze pollution. The five cities had similar characteristics and pollution sources.
•The pollution exhibited temporal synchronization in the YRD and occurred in a regional scale.•Organic matter, sulfate, nitrate, and ammonium were the dominant components of PM2.5, and impact the visibility most.•PM2.5 mainly came from the secondary pollutants and the primary emissions of vehicles and biomass burning in this episode.•A polluted air mass transported from the north Jiangsu Province and the stagnant meteorology further aggravated the haze.
Atmospheric particulate polycyclic aromatic hydrocarbons (PAHs) have been drawing sustained attention due to their health risk and effects on air pollution. It is essential to determine the main ...sources and reduce atmospheric levels of PAHs to protect human health. PAHs in PM2.5 have been detected at five sites located in five districts in Shanghai, a modern metropolitan city in China. Spatial and temporal variations of composition profiles and sources of PAHs at each site in each season were investigated. The results showed that atmospheric particulate PAHs level in Shanghai was the lowest in summer and the highest in winter, dominated by high molecular weight (HMW) PAHs. Analysis with a combination of coefficients of Pearson's correlation and coefficient of divergences indicated heterogeneous spatial and temporal distribution for LMW PAHs and homogenous distribution for HMW PAHs. Diagnostic ratios and positive matrix factorization (PMF) model both identified pyrogenic sources as the main contributor of PAHs in Shanghai, with vehicular source contribution of 32–43% to the total PAHs annually and around 20% from biomass burning emissions in urban and urban buildup areas. While in winter, coal combustion and biomass burning could act as two major sources of PAHs in suburban areas, which could contribute to >70% of total PAHs measured in PM2.5 in Shanghai.
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•HMW PAHs were more homogeneously distributed compared to LMW PAHs.•Suburban sites were subjected to higher BaPeq values in winter, suggesting higher health risks.•Vehicle emission was a major source of PAHs (32–43%) in urban and urban buildup areas.•Biomass and coal combustion were major sources in suburban areas in winter.
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•We surveyed 3177 preschoolers who did not change residences after birth.•We studied associations of early exposures to NO2, SO2, PM10 with airway diseases.•Prenatal and Postnatal ...exposures to NO2 were associated with airway diseases.•Associations of NO2 were generally stronger than in the early than later trimesters.
It’s inconsistent about associations of early exposures to outdoor air pollutants with allergies and airway diseases in childhood. Here, we investigated associations of prenatal and postnatal exposures to outdoor nitrogen dioxide (NO2), sulphur dioxide (SO2), and PM10 (particulate matter with an aerodynamic diameter ≤ 10 μm) with asthma, wheeze, hay fever, rhinitis, pneumonia, and eczema in childhood. We surveyed 3,177 preschoolers who never change residences since birth in Shanghai, China. Parents reported information regarding children’s health status. Daily-averaged concentrations of these pollutants in the children’s gestation and in the first year of lifetime for district where children lived were collected by Shanghai Environmental Monitoring Center. After adjusting for covariates, exposures to higher level of NO2 during different trimesters of gestation and of the first year of lifetime had significant associations with the increased odds of asthma, hay fever, rhinitis, pneumonia, and eczema in childhood. Associations of NO2 exposures in the early trimesters of gestation and of the first year of lifetime with pneumonia were stronger than in the later trimesters, whereas associations of NO2 exposures in the early trimesters with hay fever and eczema were weaker than in the later trimesters. Our results indicated that prenatal and postnatal exposures to outdoor NO2 could be risk factors for allergies and airway diseases in childhood. Both dose and duration were related with the influence degree of early NO2 exposure on childhood allergies and airway diseases.
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