In the atmosphere nighttime removal of volatile organic compounds is initiated to a large extent by reaction with the nitrate radical (NO3) forming organic nitrates which partition between gas and particulate phase. Here we show based on particle phase measurements performed at a suburban site in the Netherlands that organic nitrates contribute substantially to particulate nitrate and organic mass. Comparisons with a chemistry transport model indicate that most of the measured particulate organic nitrates are formed by NO3 oxidation. Using aerosol composition data from three intensive observation periods at numerous measurement sites across Europe, we conclude that organic nitrates are a considerable fraction of fine particulate matter (PM1) at the continental scale. Organic nitrates represent 34% to 44% of measured submicron aerosol nitrate and are found at all urban and rural sites, implying a substantial potential of PM reduction by NOx emission control.

Aerosol climate effects are intimately tied to interactions with water. Here we combine hygroscopicity measurements with direct observations about the phase of secondary organic aerosol (SOA) particles to show that water uptake by slightly oxygenated SOA is an adsorption‐dominated process under subsaturated conditions, where low solubility inhibits water uptake until the humidity is high enough for dissolution to occur. This reconciles reported discrepancies in previous hygroscopicity closure studies. We demonstrate that the difference in SOA hygroscopic behavior in subsaturated and supersaturated conditions can lead to an effect up to about 30% in the direct aerosol forcing—highlighting the need to implement correct descriptions of these processes in atmospheric models. Obtaining closure across the water saturation point is therefore a critical issue for accurate climate modeling.

Secondary organic aerosols (SOA) forms a major fraction of organic aerosols in the atmosphere. Knowledge of SOA properties that affect their dynamics in the atmosphere is needed for improving climate models. By combining experimental and modeling techniques, we investigated the factors controlling SOA evaporation under different humidity conditions. Our experiments support the conclusion of particle phase diffusivity limiting the evaporation under dry conditions. Viscosity of particles at dry conditions was estimated to increase several orders of magnitude during evaporation, up to 109 Pa s. However, at atmospherically relevant relative humidity and time scales, our results show that diffusion limitations may have a minor effect on evaporation of the studied α‐pinene SOA particles. Based on previous studies and our model simulations, we suggest that, in warm environments dominated by biogenic emissions, the major uncertainty in models describing the SOA particle evaporation is related to the volatility of SOA constituents.

SARS-CoV-2, previously was named as COVID-2019 by the WHO, is now pandemic which has been reported 5,077 human death of 136,895 confirmed cases in 123 countries (updated on 14 March 2020 from WHO official website). The viruses have been successfully isolated, but the pathogenesis mechanisms and effective vaccines are undergoing extensively study. SARS-CoV-2 belongs to Betacoronavirus genera in the subfamily Orthocoronavirinae of family Coronaviridae, in which SARS-CoV and MERS-CoV are also in this group. The natural host of highly pathogenic SARS and MERS coronaviruses was confirmed as bats, and bats are also thought to be the natural hosts for SARS-CoV-2 based upon genomic sequence analysis (Wang, Horby, Hayden, & Gao, 2020). Coronaviruses needed intermediate hosts before being able to infect humans. Masked palm civets and dromedary camels were confirmed as intermediate hosts for SARS-CoV and MERS-CoV (Guarner, 2020), but the intermediate hosts remain unknown for SARS-CoV-2 (Ward, Li, & Tian, 2020). In order to find the intermediate host of SARS-CoV-2, a commercial double-antigen sandwich ELISA, which could be applied for different species of animals, was used to detect SARS-CoV-2-specific antibodies in different species of animals. Before applied to clinical serum samples, the sensitivity and specificity of kit were initially confirmed using SARS-CoV-2-positive and SARS-CoV-2-negative sera from experimental animals including rabbit, mouse, pig and ferret. SARS-CoV-2-negative sera from other species of experimental animals were also used which included chicken, duck, rat, guinea pig, beagle dog and rhesus monkey. After that, the kit was used to detect SARS-CoV-2-specific antibodies in domestic livestock (pig, cow, sheep, horse), poultry (chicken, duck, goose), experimental animals (mice, rat, guinea pig, rabbit and monkey), companion animal (dog and cat) and wild animals (camel, fox, mink, alpaca, ferret, bamboo rat, peacock, eagle, tiger rhinoceros, pangolin, leopard cat, jackal,

Over Boreal regions, monoterpenes emitted from the forest are the main precursors for secondary organic aerosol (SOA) formation and the primary driver of the growth of new aerosol particles to climatically important cloud condensation nuclei (CCN). Autoxidation of monoterpenes leads to rapid formation of Highly Oxygenated organic Molecules (HOM). We have developed the first model with near-explicit representation of atmospheric new particle formation (NPF) and HOM formation. The model can reproduce the observed NPF, HOM gas-phase composition and SOA formation over the Boreal forest. During the spring, HOM SOA formation increases the CCN concentration by~10 % and causes a direct aerosol radiative forcing of −0.10 W/m 2. In contrast, NPF reduces the number of CCN at updraft velocities < 0.2 m/s, and causes a direct aerosol radiative forcing of +0.15 W/m 2. Hence, while HOM SOA contributes to climate cooling, NPF can result in climate warming over the Boreal forest.