Search for: All records

Abstract. In the aqueous phase, fine particulate matter can form reactive species (RS)that influence the aging, properties, and health effects of atmosphericaerosols. In this study, we explore the RS yields of aerosol samples froma remote forest (Hyytiälä, Finland) and polluted urban locations(Mainz, Germany; Beijing, China), and we relate the RS yields to differentchemical constituents and reaction mechanisms. Ultra-high-resolution massspectrometry was used to characterize organic aerosol composition, electronparamagnetic resonance (EPR) spectroscopy with a spin-trapping technique wasapplied to determine the concentrations of ⚫OH,O2⚫-, and carbon- or oxygen-centered organic radicals, anda fluorometric assay was used to quantify H2O2. The aqueousH2O2-forming potential per mass unit of ambient PM2.5(particle diameter < 2.5 µm) was roughly the same for allinvestigated samples, whereas the mass-specific yields of radicals werelower for sampling sites with higher concentrations of PM2.5. Theabundances of water-soluble transition metals and aromatics in ambientPM2.5 were positively correlated with the relative fraction of⚫OH and negatively correlated with the relative fraction ofcarbon-centered radicals. In contrast, highly oxygenated organic molecules(HOM) were positively correlated with the relative fraction ofcarbon-centered radicals and negatively correlated with the relativefraction of ⚫OH. Moreover, we found that the relative fractionsof different types of radicals formed by ambient PM2.5 were comparableto surrogate mixtures comprising transition metal ions, organichydroperoxide, H2O2, and humic or fulvic acids. The interplay oftransition metal ions (e.g., iron and copper ions), highly oxidized organicmolecules (e.g., hydroperoxides), and complexing or scavenging agents (e.g.,humic or fulvic acids) leads to nonlinear concentration dependencies inaqueous-phase RS production. A strong dependence on chemical compositionwas also observed for the aqueous-phase radical yields oflaboratory-generated secondary organic aerosols (SOA) from precursormixtures of naphthalene and β-pinene. Our findings show how thecomposition of PM2.5 can influence the amount and nature ofaqueous-phase RS, which may explain differences in the chemical reactivityand health effects of particulate matter in clean and polluted air. 

Abstract Despite notable scientific and medical advances, broader political, socioeconomic and behavioural factors continue to undercut the response to the COVID-19 pandemic 1,2 . Here we convened, as part of this Delphi study, a diverse, multidisciplinary panel of 386 academic, health, non-governmental organization, government and other experts in COVID-19 response from 112 countries and territories to recommend specific actions to end this persistent global threat to public health. The panel developed a set of 41 consensus statements and 57 recommendations to governments, health systems, industry and other key stakeholders across six domains: communication; health systems; vaccination; prevention; treatment and care; and inequities. In the wake of nearly three years of fragmented global and national responses, it is instructive to note that three of the highest-ranked recommendations call for the adoption of whole-of-society and whole-of-government approaches 1 , while maintaining proven prevention measures using a vaccines-plus approach 2 that employs a range of public health and financial support measures to complement vaccination. Other recommendations with at least 99% combined agreement advise governments and other stakeholders to improve communication, rebuild public trust and engage communities 3 in the management of pandemic responses. The findings of the study, which have been further endorsed by 184 organizations globally, include points of unanimous agreement, as well as six recommendations with >5% disagreement, that provide health and social policy actions to address inadequacies in the pandemic response and help to bring this public health threat to an end.