ABSTRACT
China is the largest emitter of greenhouse gases in the world. However, the atmospheric observation of greenhouse gases is relatively sparse. In this study, surface measurements of CH4 over 5 years at a typical city site (Hangzhou) in an economically developed region in China were conducted to study the temporal variations and the influence of meteorological factors and airmass transport. The CH4 observations from a suburban site (Lin'an station [LAN]) which is a World Meteorological Organization/Global Atmosphere Monitoring Program (WMO/GAW) regional site, were also compared. Our results showed that the atmospheric CH4 mole fraction in Hangzhou was not only affected by meteorological factors and topography, but also by strong local emissions. Although the distance between the two stations was only 50 km, there was a significant difference in the temporal CH4 variations. The strong anthropogenic emissions in the city were responsible for the urban-suburban site difference. The CH4 peaks in the diurnal cycles in Hangzhou corresponded to rush hours, and there were unique variations during special periods (i.e., the National Day holiday, coronavirus disease 2019 [COVID - 19] lock-down). It also led to an annual average CH4 mole fraction at the Hangzhou station (HZ) that was on average 111.1 ± 1.6 ppb higher than that at the LAN from 2016 to 2020. The lock-down measures caused by the outbreak of COVID - 19 decreased the atmospheric CH4 mole fractions by 6.8% in Hangzhou but only 1.9% in Lin'an in 2020 compared to those in 2019. Excluding the data in 2020, the annual growth rate of the CH4 mole fraction was 19.0 ppb yr−1 in Hangzhou. Our results indicated that the CH4 mole fraction in Hangzhou was mainly driven by local anthropogenic emissions, although they were influenced by emissions from surrounding cities such as Nanjing and Ningbo.
ABSTRACT
Coronavirus disease 2019 (COVID-19), which is triggered by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, continues to threaten global public health. Developing a vaccine that only requires single immunization but provides long-term protection for the prevention and control of COVID-19 is important. Here, we developed an adeno-associated virus (AAV)-based vaccine expressing a stable receptor-binding domain (SRBD) protein. The vaccine requires only a single shot but provides effective neutralizing antibodies (NAbs) over 598 days in rhesus macaques (Macaca mulatta). Importantly, our results showed that the NAbs were kept in high level and long lasting against authentic wild-type SARS-CoV-2, Beta, Delta and Omicron variants using plaque reduction neutralization test. Of note, although we detected pre-existing AAV2/9 antibodies before immunization, the vaccine still induced high and effective NAbs against COVID-19 in rhesus macaques. AAV-SRBD immune serum also efficiently inhibited the binding of ACE2 with RBD in the SARS-CoV-2 B.1.1.7 (Alpha), B.1.351 (Beta), P.1/P.2 (Gamma), B.1.617.2 (Delta), B.1.617.1/3(Kappa), and C.37 (Lambda) variants. Thus, these data suggest that the vaccine has great potential to prevent the spread of SARS-CoV-2.