COVID-19 suddenly struck Wuhan at the end of 2019 and soon spread to the whole country and the rest of world in 2020. To mitigate the pandemic, China authority has taken unprecedentedly strict measures across the country. That provides a precious window to study how the air quality response to quick decline of anthropogenic emissions in terms of national scale, which would be critical basis to make atmospheric governance policies in the future. In this work, we utilized observations from both remote sensing and in-situ measurements to investigate impacts of COVID-19 lockdown on different air pollutions in different regions of China. It is witnessed that the PM 2.5 concentrations exhibited distinct trends in different regions, despite of plunges of NO 2 concentrations over the whole country. The steady HCHO concentration in urban area provides sufficient fuels for generations of tropospheric O 3 , leading to high concentrations of O 3 , especially when there is not enough NO to consume O 3 via the titration effect. Moreover, the SO 2 concentration kept steady at a low level regardless of cities. As a conclusion, the COVID-19 lockdown indeed helped reduce NO 2 concentration. However, the atmospheric quality in urban areas of China has not improved overall due to lockdown measures. It underscores the significance of comprehensive control of atmospheric pollutants in cleaning air. Reducing VOCs (volatile organic compounds) concentrations in urban areas would be a critical mission for better air quality in the future.

Current observations show that the growth of the atmospheric CO 2 concentration is evidently lower than expected, suggesting that anthropogenic carbon emissions have been offset by some unclear carbon sinks. Oceans and terrestrial ecosystems are supposed to be responsible for the missing carbon sinks (Sabine et al., 2004;Takahashi et al., 2009). Scientists have utilized varieties of means to explore carbon fluxes of terrestrial ecosystems quantitatively in the recent decades, trying to narrow gaps between observations and estimates of models (Eldering et al., 2017;Watson et al., 2009). Comparing with progresses in estimating carbon fluxes of terrestrial ecosystems, we still have some barriers to a better understanding on carbon fluxes of oceans. We do know oceans offset anthropogenic carbon emissions but there are lacks of quantitative and accurate estimates of CO 2 fluxes over oceans. Therefore, we don't have insight knowledge on distributions and dynamics of ocean carbon uptakes. Some pieces of evidence suggest that there may be a trigger point beyond which CO 2 uptakes of oceans would rapidly decline or even shift to a net CO 2 emission (DeVries et al., 2019). Therefore, designing more measurement methods to estimate ocean CO 2 fluxes more reliably and efficiently is of great importance.The difference of CO 2 partial pressures in seawater (p(CO 2 ) sw ) and overlying air (p(CO 2 ) air ) would cause a net transfer of CO 2 flux between ocean and atmosphere (Wanninkhof, 2014). Experiments for measuring (p(CO 2 ) sw ) during ship tracks have been implemented in different regions of the global sea, which help to

No abstract

No abstract