What Business Researchers are producing during Covid-19 A bibliometric approach

The way COVID-19 impacted every aspect of human life around the world, is now considered more disastrous than the World War II. Both the policy and academic researchers have been contributing to assess its severity and impact on businesses and economies while examining the foci of business researchers in this era of contagion. In this assessment, we have applied the approaches of bibliometric and content analysis on 403 qualified studies, drawn from the Scopus database. The period of data ranges from 2003 to June 2020. We identified 11 different research streams including tourism, supply chain besides economic and finance-related research. We highlighted the sub-streams and main concerns raised in the published literature. The findings of this research indicate that COVID will force the policy makers to come up with strategy and changes in various business fields. The implications of the study may be important for business managers to chalk out a proactive approach for business handling during and post-COVID eras.

COVID-19 Pandemic Reveals Distinct Impact of Aerosols on Surface Solar Radiation in China

With the abrupt and significant drop of PM2.5 concentrations during the lockdown in 2020, hourly direct radiation (Rdir) at surface substantially increased in East China, such as Zhengzhou, Wuhan and Baoshan, with the maximum enhancement of 86% at Wuhan. Most of these stations had decreased diffuse radiation (Rdif) except Zhengzhou. Zhengzhou had both enhanced Rdir and Rdif, as well as reduced but still high PM2.5 concentrations, indicating atmospheric particles were more scattering in this region. At Beijing and Harbin in North and Northeast China, intensification of aerosol pollution led to hourly Rdir (Rdif) falling (rising) up to −28% (59%) and −23% (40%), respectively. By contrast, surface solar radiation (SSR) in West China was also greatly influenced by the elevated dust/smoke layers, revealed by aerosol layer vertical distribution and the reduction of SSR and PM2.5 concentrations. This study highlighted the importance of aerosol optical properties and vertical structures in aerosol–radiation interactions. © 2023. The Authors.

Enhanced natural releases of mercury in response to the reduction in anthropogenic emissions during the COVID-19 lockdown by explainable machine learning

The wide spread of the coronavirus (COVID-19) has significantly impacted the global human activities. Compared to numerous studies on conventional air pollutants, atmospheric mercury that has matched sources from both anthropogenic and natural emissions is rarely investigated. At a regional site in eastern China, an intensive measurement was performed, showing obvious decreases in gaseous elemental mercury (GEM) during the COVID-19 lockdown, while it was not as significant as most of the other measured air pollutants. Before the lockdown, when anthropogenic emissions dominated, GEM showed no correlation with temperature and negative correlations with wind speed and the height of the boundary layer. In contrast, GEM showed significant correlation with temperature, while the relationship between GEM and the wind speed/boundary layer disappeared during the lockdown, suggesting the enhanced natural emissions of mercury. By applying a machine learning model and the SHAP (SHapley Additive exPlanations) approach, it was found that the mercury pollution episodes before the lockdown were driven by anthropogenic sources, while they were mainly driven by natural sources during and after the lockdown. Source apportionment results showed that the absolute contribution of natural surface emissions to GEM unexpectedly increased (44 %) during the lockdown. Throughout the whole study period, a significant negative correlation was observed between the absolute contribution of natural and anthropogenic sources to GEM. We conclude that the natural release of mercury could be stimulated to compensate for the significantly reduced anthropogenic GEM via the surface-air exchange in the balance of mercury.

Assessment of Atmospheric PM2.5 and PCDD/Fs Collected by Different High-volume Ambient Air Sampling Systems

To evaluate the difference in hazardous air pollutants in PM2.5 between reference method (National Institute of Environmental Analysis;NIEAA205) and high-volume air sampler (European standard:EN14907 and Japan method), we set up a sampling station on the campus of National Yang-Ming Chiao Tung University, northern Taiwan, during 2014-2015. Both vapor and solid phases of dioxins were collected using high-volume samplers, according to EN14907 and Japan method. The flow rate was set at 500 L min(-1) and 1000 L min(-1), respectively. To compare the difference with the high-volume air sampler, we simultaneously used the reference air sampler based on Taiwan NIEA A205.11C, at the flow rate of 16.7 L min(-1) (BGI PQ200-FRM). The mass concentrations of PM2.5 measured with NIEA A205, EN14907, and Japan method were 20.2 +/- 8.79, 25.4 +/- 10.5 and 28.6 +/- 13.9 mu g m(-3), respectively. The difference of the mass concentration of PM2.5 obtained from two different methods was lower than 3.9%. Moreover, the concentrations of PCDD/F between solid and vapor phases were 56.9-1,090 and 38.6-67.1 fg m(-3) via EN14907 and 51.1-1,150 and 18.4-81.8 fg m(-3) via Japan method, respectively. Obviously, there is no significant difference between these two samplers. Compared to the method of NIEA, high volume air sampling method not only provided equivalently good quality data but offer a higher sample quantity for analyzing the trace level chemical component of hazardous air pollutants and the toxicity in different areas.

Record-Breaking Slow Temperature Evolution of Spring Water During 2020 and Its Impacts on Spring Bloom in the Yellow Sea

Unprecedented retardation of spring water temperature rising during the 2020 pandemic year was identified in the Socheongcho Ocean Research Station within the northeastern basin of the Yellow Sea: an exceptionally high water temperature anomaly in March and a contrasted low-temperature anomaly in May. The slowest temperature evolution was principally caused by the significant increase in latent heat releases in April (117% higher than the climatology of 1982-2019). Strong northwesterly winds generated these exceptional heat fluxes associated with the dipole-like atmospheric circulation pattern over Siberia and the East Sea (Japan Sea). Besides, warm winter water facilitated the enhanced release of latent heat fluxes as a precondition. The oceanic heat redistribution partially supported the cold anomaly in the surface layer up to the middle of May through positive feedback between the low surface temperature and the active entrainment associated with tidal turbulent mixing. The resultant low temperature at the surface weakened the vertical stratification, both impeding the activation of phytoplankton's photosynthesis albeit under the eutrophic surface layer, consequently resulting in the delayed and suppressed spring bloom during 2020. Since such extreme events are anticipated to occur more frequently under global warming, our results highlight the importance of continuously monitoring multi-disciplinary environmental conditions, climate extremes, and their impact on the Yellow Sea marine ecosystem.

Impact of Meteorological Conditions and Human Activities on Air Quality During the COVID-19 Lockdown in Northeast China

During the lockdown implemented to curb the spread of COVID-19, human activities have drastically reduced, providing a valuable opportunity to study and compare the impact of meteorological conditions and human activities on air quality. In this study, large-scale weather circulation, local meteorological conditions, and the impact of human activities are comprehensively considered, and changes in the concentration of major air pollutants in the northeast during this period are systematically studied. The large-scale weather circulation patterns that mainly affect the northeast region are divided into nine types by using the T-mode Principal components analysis objective circulation classification method. It is found that the northeast region is located at the edge of weak high pressure (Types 1, 2, and 7) and at the rear of high pressure (Type 4) and has higher concentrations of PM2.5, NO2, SO2, and CO;in cyclonic weather systems, low vortices (Types 3 and 5) and under the influence of the updraft (Type 6) in front of the trough, the ozone concentration is higher. The changes in the concentrations of PM2.5, NO2, CO, SO2, and O-3 in the three cities, namely Shenyang, Changchun, and Harbin, during the lockdown period are compared, and it is found that the concentrations of PM2.5, NO2, CO, and SO2 have a tendency to first decrease and then increase, while the changes of O-3 concentration are cyclical and increased significantly during this period. This demonstrates that pollutants such as PM2.5, NO2, CO, and SO2 are more susceptible to human activities and local meteorological conditions, and changes in O-3 concentration are more closely related to changes in weather circulation types. Finally, the FLEXPART-WRF model is used to simulate the pollution process of nine circulation types, which confirms that particulate pollution in the northeast is mainly affected by local emissions and local westward sinking airflow.

Impact Assessment of COVID-19 on Variations of SO2, NO2, CO and AOD over East China

The COVID-19 (Coronavirus Disease 2019) broke out in the late of 2019. On January 23 in Wuhan, and later in all other cities of the country, there were taken measures to control the spread of the virus through quarantine measures. This article focused on East China and attempted to assess comprehensively the environmental impact of the COVID-19 outbreak. This study analyzed satellite observational data of sulfur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO) and aerosol optical depth (AOD) in the period before the outbreak of the epidemic and during the implementation of preventive measures and control of COVID-19, as well as compared it with the data obtained in the same period of 2019. The results of the analysis showed that the COVID-19 lockdown improved air quality in the short term, but as soon as coal consumption at power plants and refineries returned to normal levels due to the resumption of their work, pollution levels returned to their previous level. The levels of CO and NO2 showed the most significant decrease (20 and 30%), since they were mainly associated with a decrease in economic growth and transport restrictions that led to a change in energy consumption and a reduction in emissions. This study can complement the scientific community and environmental protection policy makers, not only to assess the impact of outbreak on air quality, but also for its effectiveness as a simple alternative program of action to improve air quality.