Characterization of offline analysis of particulate matter with FIGAERO-CIMS

Measurements of the molecular composition of organic aerosol (OA) constituents improve our understanding of sources, formation processes, and physicochemical properties of OA. One instrument providing such data at a time resolution of minutes to hours is the chemical ionization time-of-flight mass spectrometer with filter inlet for gases and aerosols (FIGAERO-CIMS). The technique collects particles on a filter, which are subsequently desorbed, and the evaporated molecules are ionized and analyzed in the mass spectrometer. However, long-term measurements using this technique and/or field deployments at several sites simultaneously require substantial human and financial resources. The analysis of filter samples collected outside the instrument (offline) may provide a more cost-efficient alternative and makes this technology available for the large number of particle filter samples collected routinely at many different sites globally. Filter-based offline use of the FIGAERO-CIMS limits this method, albeit to particle-phase analyses, which is likely at a reduced time resolution compared to online deployments. Here we present the application and assessment of offline FIGAERO-CIMS, using Teflon and quartz fiber filter samples that were collected in autumn 2018 in urban Beijing. We demonstrate the feasibility of the offline application with a “sandwich” sample preparation for the over 900 identified organic compounds with (1) high signal-to-noise ratios, (2) high repeatability, and (3) linear signal response to the filter loadings. Comparable overall signals were observed between the quartz fiber and Teflon filters for 12 and 24 h samples but with larger signals for semi-volatile compounds for the quartz fiber filters, likely due to adsorption artifacts. We also compare desorption profile (thermogram) shapes for the two filter materials. Thermograms are used to derive volatility qualitatively based on the desorption temperature at which the maximum signal intensity of a compound is observed (Tmax⁡). While we find that Tmax⁡ can be determined with high repeatability (±5.7 ∘C) from the duplicate tests for one filter type, we observe considerable differences in Tmax⁡ between the quartz and Teflon filters, warranting further investigation into the thermal desorption characteristics of different filter types. Overall, this study provides a basis for expanding OA molecular characterization by FIGAERO-CIMS to situations where and when deployment of the instrument itself is not possible.</p

Influence of organic aerosol molecular composition on particle absorptive properties in autumn Beijing

Publisher Copyright: © 2022 Jing Cai et al.Organic aerosol (OA) is a major component of fine particulate matter (PM), affecting air quality, human health, and the climate. The absorptive and reflective behavior of OA components contributes to determining particle optical properties and thus their effects on the radiative budget of the troposphere. There is limited knowledge on the influence of the molecular composition of OA on particle optical properties in the polluted urban environment. In this study, we characterized the molecular composition of oxygenated OA collected on filter samples in the autumn of 2018 in Beijing, China, with a filter inlet for gases and aerosols coupled to a high-resolution time-of-flight chemical ionization mass spectrometer (FIGAERO-CIMS). Three haze episodes occurred during our sampling period with daily maximum concentrations of OA of 50, 30, and 55 μg m-3. We found that the signal intensities of dicarboxylic acids and sulfur-containing compounds increased during the two more intense haze episodes, while the relative contributions of wood-burning markers and other aromatic compounds were enhanced during the cleaner periods. We further assessed the optical properties of oxygenated OA components by combining detailed chemical composition measurements with collocated particle light absorption measurements. We show that light absorption enhancement (Eabs) of black carbon (BC) was mostly related to more oxygenated OA (e.g., dicarboxylic acids), likely formed in aqueous-phase reactions during the intense haze periods with higher relative humidity, and speculate that they might contribute to lensing effects. Aromatics and nitro-aromatics (e.g., nitrocatechol and its derivatives) were mostly related to a high light absorption coefficient (babs) consistent with light-absorbing (brown) carbon (BrC). Our results provide information on oxygenated OA components at the molecular level associated with BrC and BC particle light absorption and can serve as a basis for further studies on the effects of anthropogenic OA on radiative forcing in the urban environment.Peer reviewe

Intra-Arterial Urokinase After Endovascular Reperfusion for Acute Ischemic Stroke: The POST-UK Randomized Clinical Trial

Importance. Persisting or new thrombi in the distal arteries and the microcirculation have been reported to limit the benefits of successful endovascular thrombectomy for patients with acute ischemic stroke. It remains uncertain whether intra-arterial thrombolysis by urokinase following near-complete to complete reperfusion by thrombectomy improves outcomes among patients with ischemic stroke due to large vessel occlusion.Objective. To assess the efficacy and adverse events of intra-arterial urokinase after near-complete to complete reperfusion by thrombectomy for acute ischemic stroke due to large vessel occlusion.Design, Setting, and Participants. This investigator-initiated, randomized, open-label, blinded–end point trial was implemented at 35 hospitals in China, enrolling 535 patients with proximal intracranial large vessel occlusion presenting within 24 hours of time last known well, who achieved near-complete or complete reperfusion by endovascular thrombectomy and did not receive intravenous thrombolysis prior to the procedure. Recruitment took place between November 15, 2022, and March 29, 2024, with final follow-up on July 4, 2024.Interventions. Eligible patients were randomly assigned to the intra-arterial urokinase group (a single dose of intra-arterial 100 000 IU urokinase injected in the initial target territory; n = 267) or control group (without intra-arterial thrombolysis; n = 267).Main Outcomes and Measures. The primary efficacy outcome was the percentage of patients achieving survival without disability (modified Rankin Scale score of 0 or 1) at 90 days. The primary safety outcomes were mortality at 90 days and incidence of symptomatic intracranial hemorrhage within 48 hours.Results. A total of 535 patients were enrolled (median age, 69 years; 223 [41.8%] female) and 532 (99.6%) completed the trial. The percentage of patients with survival without disability at 90 days was 45.1% (120/266) in the intra-arterial urokinase group and 40.2% (107/266) in the control group (adjusted risk ratio, 1.13 [95% CI, 0.94-1.36]; P = .19). Mortality at 90 days (18.4% vs 17.3%, respectively; adjusted hazard ratio, 1.06 [95% CI, 0.71-1.59]; P = .77) and incidence of symptomatic intracranial hemorrhage (4.1% vs 4.1%, respectively; adjusted risk ratio, 1.05 [95% CI, 0.45-2.44]; P = .91) were not significantly different between groups.Conclusions and Relevance. Among patients with acute ischemic stroke due to large vessel occlusion, adjunct intra-arterial urokinase after near-complete to complete reperfusion by endovascular thrombectomy did not significantly increase the likelihood of survival without disability at 90 days.</p

The effect of COVID-19 restrictions on atmospheric new particle formation in Beijing

During the COVID-19 lockdown, the dramatic reduction of anthropogenic emissions provided a unique opportunity to investigate the effects of reduced anthropogenic activity and primary emissions on atmospheric chemical processes and the consequent formation of secondary pollutants. Here, we utilize comprehensive observations to examine the response of atmospheric new particle formation (NPF) to the changes in the atmospheric chemical cocktail. We find that the main clustering process was unaffected by the drastically reduced traffic emissions, and the formation rate of 1.5 nm particles remained unaltered. However, particle survival probability was enhanced due to an increased particle growth rate (GR) during the lockdown period, explaining the enhanced NPF activity in earlier studies. For GR at 1.5-3 nm, sulfuric acid (SA) was the main contributor at high temperatures, whilst there were unaccounted contributing vapors at low temperatures. For GR at 3-7 and 7-15 nm, oxygenated organic molecules (OOMs) played a major role. Surprisingly, OOM composition and volatility were insensitive to the large change of atmospheric NOx concentration; instead the associated high particle growth rates and high OOM concentration during the lockdown period were mostly caused by the enhanced atmospheric oxidative capacity. Overall, our findings suggest a limited role of traffic emissions in NPF.Peer reviewe

Intra-Arterial Urokinase After Endovascular Reperfusion for Acute Ischemic Stroke: The POST-UK Randomized Clinical Trial

Importance. Persisting or new thrombi in the distal arteries and the microcirculation have been reported to limit the benefits of successful endovascular thrombectomy for patients with acute ischemic stroke. It remains uncertain whether intra-arterial thrombolysis by urokinase following near-complete to complete reperfusion by thrombectomy improves outcomes among patients with ischemic stroke due to large vessel occlusion. Objective. To assess the efficacy and adverse events of intra-arterial urokinase after near-complete to complete reperfusion by thrombectomy for acute ischemic stroke due to large vessel occlusion. Design, Setting, and Participants. This investigator-initiated, randomized, open-label, blinded–end point trial was implemented at 35 hospitals in China, enrolling 535 patients with proximal intracranial large vessel occlusion presenting within 24 hours of time last known well, who achieved near-complete or complete reperfusion by endovascular thrombectomy and did not receive intravenous thrombolysis prior to the procedure. Recruitment took place between November 15, 2022, and March 29, 2024, with final follow-up on July 4, 2024. Interventions. Eligible patients were randomly assigned to the intra-arterial urokinase group (a single dose of intra-arterial 100 000 IU urokinase injected in the initial target territory; n = 267) or control group (without intra-arterial thrombolysis; n = 267). Main Outcomes and Measures. The primary efficacy outcome was the percentage of patients achieving survival without disability (modified Rankin Scale score of 0 or 1) at 90 days. The primary safety outcomes were mortality at 90 days and incidence of symptomatic intracranial hemorrhage within 48 hours. Results. A total of 535 patients were enrolled (median age, 69 years; 223 [41.8%] female) and 532 (99.6%) completed the trial. The percentage of patients with survival without disability at 90 days was 45.1% (120/266) in the intra-arterial urokinase group and 40.2% (107/266) in the control group (adjusted risk ratio, 1.13 [95% CI, 0.94-1.36]; P = .19). Mortality at 90 days (18.4% vs 17.3%, respectively; adjusted hazard ratio, 1.06 [95% CI, 0.71-1.59]; P = .77) and incidence of symptomatic intracranial hemorrhage (4.1% vs 4.1%, respectively; adjusted risk ratio, 1.05 [95% CI, 0.45-2.44]; P = .91) were not significantly different between groups. Conclusions and Relevance. Among patients with acute ischemic stroke due to large vessel occlusion, adjunct intra-arterial urokinase after near-complete to complete reperfusion by endovascular thrombectomy did not significantly increase the likelihood of survival without disability at 90 days

Response of Global Air Pollutant Emissions to Climate Change and Its Potential Effects on Human Life Expectancy Loss

Geographical environment and climate change are basic factors for spatial fluctuations in the global distribution of air pollutants. Against the background of global climate change, further investigation is needed on how meteorological characteristics and complex geographical environment variations can drive spatial air pollution variations. This study analyzed the response of air pollutant emissions to climate change and the potential effects of air pollutant emissions on human health by integrating the air pollutant emission simulation model (GAINS) with 3 versions and CMIP5. The mechanism by which meteorological characteristics and geographical matrices can drive air pollution based on monitoring data at the site-scale was also examined. We found the total global emission of major air pollutants increased 1.32 times during 1970–2010. Air pollutant emissions will increase 2.89% and 4.11% in China and developed countries when the scenario of only maximum technically feasible reductions is performed (V4a) during 2020–2050. However, it will decrease 19.33% and 6.78% respectively by taking the V5a climate scenario into consideration, and precipitation variation will contribute more to such change, especially in China. Locally, the air circulation mode that is dominated by local geographical matrices and meteorological characteristics jointly affect the dilution and diffusion of air pollutants. Therefore, natural conditions, such as climate changes, meteorological characteristics and topography, play an important role in spatial air pollutant emissions and fluctuations, and must be given more attention in the processes of air pollution control policy making.</jats:p