Global variability in atmospheric new particle formation mechanisms.

A key challenge in aerosol pollution studies and climate change assessment is to understand how atmospheric aerosol particles are initially formed1,2. Although new particle formation (NPF) mechanisms have been described at specific sites3-6, in most regions, such mechanisms remain uncertain to a large extent because of the limited ability of atmospheric models to simulate critical NPF processes1,7. Here we synthesize molecular-level experiments to develop comprehensive representations of 11 NPF mechanisms and the complex chemical transformation of precursor gases in a fully coupled global climate model. Combined simulations and observations show that the dominant NPF mechanisms are distinct worldwide and vary with region and altitude. Previously neglected or underrepresented mechanisms involving organics, amines, iodine oxoacids and HNO3 probably dominate NPF in most regions with high concentrations of aerosols or large aerosol radiative forcing; such regions include oceanic and human-polluted continental boundary layers, as well as the upper troposphere over rainforests and Asian monsoon regions. These underrepresented mechanisms also play notable roles in other areas, such as the upper troposphere of the Pacific and Atlantic oceans. Accordingly, NPF accounts for different fractions (10-80%) of the nuclei on which cloud forms at 0.5% supersaturation over various regions in the lower troposphere. The comprehensive simulation of global NPF mechanisms can help improve estimation and source attribution of the climate effects of aerosols.

Benefits of napping habits in healthy adults: Maintaining alerting performance and cortisol levels change within 90 min of habitual napping time.

BACKGROUND: Napping is garnering increased attention as a strategy for adults to sustain alertness and alleviate stress in contemporary society. The nuances of napping habits are emerging as an independent factor influencing the extent of individual benefits. This study aimed to demonstrate the long-term benefits of napping and explore the impact of napping habits on individual alertness, as well as whether this effect was correlated with cortisol levels. METHODS: The study involved 80 healthy adults categorized into two groups based on self-reported napping habits: habitual nappers (n = 49) and non-habitual nappers (n = 31). Karolinska Sleepiness Scale (KSS), psychomotor vigilance task (PVT), and saliva collection were performed every 30 min within 90 min in the absence of napping during the afternoon dip. The measurements were analyzed using repeated measures ANOVA and Pearson correlation analyses. RESULTS: There was an interaction between groups and time in reaction speed and lapse number of PVT and cortisol (all p < 0.05). Post hoc analysis found that habitual nappers maintained higher objective alertness and experienced more significant increases in cortisol over time (all p < 0.05). The cortisol levels at sleepiness time were negatively associated with the slowest 10 % reaction speed of PVT in non-habitual nappers (r = -0.409, p = 0.022). CONCLUSION: Under the premise of mitigating the impacts of acute nap deprivation on sleep homeostasis and rhythm, napping habits emerge as a potential factor influencing the ability of individuals to sustain heightened alertness.

Depression, anxiety, and burnout among psychiatrists during the COVID-19 pandemic: a cross-sectional study in Beijing, China.

BACKGROUND: With the rise of reported mental disorders and behavioral issues after the outbreak of the coronavirus disease 2019 (COVID-19) pandemic, psychiatrists and mental health care are urgently needed more than ever before. The psychiatric career carries a high emotional burden and stressful demands, which bring issues on psychiatrists' mental health and well-being into question. To investigate the prevalence and risk factors of depression, anxiety, and work burnout among psychiatrists in Beijing during the COVID-19 pandemic. METHODS: This cross-sectional survey was conducted from January 6 to January 30, 2022, two years after COVID-19 was declared a global pandemic. Recruitment was performed using a convenience sample approach by sending online questionnaires to psychiatrists in Beijing. The symptoms of depression, anxiety, and burnout were evaluated using the Patient Health Questionnaire-9 (PHQ-9), Generalized Anxiety Disorder-7 (GAD-7), and Maslach Burnout Inventory-General Survey (MBI-GS). The perceived stress and social support were measured by the Chinese Perceived Stress Scale (CPSS) and Social Support Rating Scale (SSRS), respectively. RESULTS: The data of 564 psychiatrists (median [interquartile range] age, 37 [30-43] years old) of all 1532 in Beijing were included in the statistical analysis. The prevalence of symptoms of depression, anxiety and burnout were 33.2% (95% CI, 29.3-37.1%, PHQ-9 ≥ 5), 25.4% (95% CI, 21.8-29.0%, GAD-7 ≥ 5) and 40.6% (95% CI, 36.5-44.7%, MBI-GS ≥ 3 in each of the three subdimensions), respectively. The psychiatrist with a higher score on perceived stress was more likely to suffer from depressive symptoms (adjusted odds ratios [ORs]: 4.431 [95%CI, 2.907-6.752]); the anxiety symptoms (adjusted ORs: 8.280 [95%CI, 5.255-13.049]), and the burnout conditions (adjusted ORs: 9.102 [95%CI, 5.795-14.298]). Receiving high social support was an independent protective factor against symptoms of depression (adjusted ORs: 0.176 [95%CI, [0.080-0.386]), anxiety (adjusted ORs: 0.265 [95%CI, 0.111-0.630]) and burnout (adjusted ORs: 0.319 [95%CI, 0.148-0.686]). CONCLUSIONS: Our data suggest a considerable proportion of psychiatrists also suffer from depression, anxiety, and burnout. Perceived stress and social support influence depression, anxiety, and burnout. For public health, we must work together to reduce the pressure and increase social support to mitigate mental health risks in psychiatrists.

NO at low concentration can enhance the formation of highly oxygenated biogenic molecules in the atmosphere.

The interaction between nitrogen monoxide (NO) and organic peroxy radicals (RO2) greatly impacts the formation of highly oxygenated organic molecules (HOM), the key precursors of secondary organic aerosols. It has been thought that HOM production can be significantly suppressed by NO even at low concentrations. Here, we perform dedicated experiments focusing on HOM formation from monoterpenes at low NO concentrations (0 - 82 pptv). We demonstrate that such low NO can enhance HOM production by modulating the RO2 loss and favoring the formation of alkoxy radicals that can continue to autoxidize through isomerization. These insights suggest that HOM yields from typical boreal forest emissions can vary between 2.5%-6.5%, and HOM formation will not be completely inhibited even at high NO concentrations. Our findings challenge the notion that NO monotonically reduces HOM yields by extending the knowledge of RO2-NO interactions to the low-NO regime. This represents a major advance towards an accurate assessment of HOM budgets, especially in low-NO environments, which prevails in the pre-industrial atmosphere, pristine areas, and the upper boundary layer.

The influence of placebo administration on the first- night effect in patients with insomnia disorder.

OBJECTIVE: We aimed to investigate the effects of placebo on the first-night effect (FNE) in insomniacs. METHODS: In sum, 36 patients with insomnia disorder who met the DSM-5 criteria were enrolled in this study. Sixteen patients with insomnia disorder were given two days of placebo intervention (placebo-administration group, PL). Twenty patients with insomnia disorder (drug-free group, DF) were not given any interventions. All participants underwent two consecutive nights of polysomnographic (PSG) testing in the sleep laboratory. Sleep diaries were recorded during one week at home before the PSG nights and on two subsequent nights. RESULTS: The results demonstrated that compared with the DF group, sleep onset latency (SOL), time in bed (TIB) and wake after sleep onset (WASO) significantly increased and sleep efficiency (SE) significantly decreased in the first sleep lab night in the PL group (all p < 0.05). Moreover, compared with the second night, significant differences were observed in lower self-reported total sleep time (TST) and more subjective WASO during the first night in the PL group (all p < 0.05). However, no significant difference was found in the duration and percentage of N1, N2, N3 and REM between the two groups. CONCLUSION: In patients with insomnia disorder, placebo administration may increase the occurrence of worse sleep without causing a change in the duration and percentage of N1, N2, N3 and REM on the first sleep lab night. In some cases, a placebo may not serve as treatment but may result in a nocebo effect.

Urban pollution greatly enhances formation of natural aerosols over the Amazon rainforest.

One of the least understood aspects in atmospheric chemistry is how urban emissions influence the formation of natural organic aerosols, which affect Earth's energy budget. The Amazon rainforest, during its wet season, is one of the few remaining places on Earth where atmospheric chemistry transitions between preindustrial and urban-influenced conditions. Here, we integrate insights from several laboratory measurements and simulate the formation of secondary organic aerosols (SOA) in the Amazon using a high-resolution chemical transport model. Simulations show that emissions of nitrogen-oxides from Manaus, a city of ~2 million people, greatly enhance production of biogenic SOA by 60-200% on average with peak enhancements of 400%, through the increased oxidation of gas-phase organic carbon emitted by the forests. Simulated enhancements agree with aircraft measurements, and are much larger than those reported over other locations. The implication is that increasing anthropogenic emissions in the future might substantially enhance biogenic SOA in pristine locations like the Amazon.

Recent intensification of winter haze in China linked to foreign emissions and meteorology.

Wintertime aerosol pollution in the North China Plain has increased over the past several decades as anthropogenic emissions in China have increased, and has dramatically escalated since the beginning of the 21st century, but the causes and their quantitative attributions remain unclear. Here we use an aerosol source tagging capability implemented in a global aerosol-climate model to assess long-term trends of PM2.5 (particulate matter less than 2.5 µm in diameter) in the North China Plain. Our analysis suggests that the impact of China's increasing domestic emissions on PM2.5 concentrations over the last two decades of 20th century was partially offset (13%) by decreasing foreign emission over this period. As foreign emissions stabilized after 2000, their counteracting effect almost disappeared, uncovering the impact of China's increasing domestic emissions that had been partially offset in previous years by reductions in foreign emissions. A slowdown in the impact from foreign emission reductions together with weakening winds explain 25% of the increased PM2.5 trend over 2000-2014 as compared to 1980-2000. Further reductions in foreign emissions are not expected to relieve China's pollution in the future. Reducing local emissions is the most certain way to improve future air quality in the North China Plain.

Dust-wind interactions can intensify aerosol pollution over eastern China.

Eastern China has experienced severe and persistent winter haze episodes in recent years due to intensification of aerosol pollution. In addition to anthropogenic emissions, the winter aerosol pollution over eastern China is associated with unusual meteorological conditions, including weaker wind speeds. Here we show, based on model simulations, that during years with decreased wind speed, large decreases in dust emissions (29%) moderate the wintertime land-sea surface air temperature difference and further decrease winds by -0.06 (±0.05) m s-1 averaged over eastern China. The dust-induced lower winds enhance stagnation of air and account for about 13% of increasing aerosol concentrations over eastern China. Although recent increases in anthropogenic emissions are the main factor causing haze over eastern China, we conclude that natural emissions also exert a significant influence on the increases in wintertime aerosol concentrations, with important implications that need to be taken into account by air quality studies.

Global long-range transport and lung cancer risk from polycyclic aromatic hydrocarbons shielded by coatings of organic aerosol.

Polycyclic aromatic hydrocarbons (PAHs) have toxic impacts on humans and ecosystems. One of the most carcinogenic PAHs, benzo(a)pyrene (BaP), is efficiently bound to and transported with atmospheric particles. Laboratory measurements show that particle-bound BaP degrades in a few hours by heterogeneous reaction with ozone, yet field observations indicate BaP persists much longer in the atmosphere, and some previous chemical transport modeling studies have ignored heterogeneous oxidation of BaP to bring model predictions into better agreement with field observations. We attribute this unexplained discrepancy to the shielding of BaP from oxidation by coatings of viscous organic aerosol (OA). Accounting for this OA viscosity-dependent shielding, which varies with temperature and humidity, in a global climate/chemistry model brings model predictions into much better agreement with BaP measurements, and demonstrates stronger long-range transport, greater deposition fluxes, and substantially elevated lung cancer risk from PAHs. Model results indicate that the OA coating is more effective in shielding BaP in the middle/high latitudes compared with the tropics because of differences in OA properties (semisolid when cool/dry vs. liquid-like when warm/humid). Faster chemical degradation of BaP in the tropics leads to higher concentrations of BaP oxidation products over the tropics compared with higher latitudes. This study has profound implications demonstrating that OA strongly modulates the atmospheric persistence of PAHs and their cancer risks.