Size-resolved particle number emissions in Beijing determined from measured particle size distributions

The climate and air quality effects of aerosol particles depend on the number and size of the particles. In urban environments, a large fraction of aerosol particles originates from anthropogenic emissions. To evaluate the effects of different pollution sources on air quality, knowledge of size distributions of particle number emissions is needed. Here we introduce a novel method for determining size-resolved particle number emissions, based on measured particle size distributions. We apply our method to data measured in Beijing, China, to determine the number size distribution of emitted particles in a diameter range from 2 to 1000 nm. The observed particle number emissions are dominated by emissions of particles smaller than 30 nm. Our results suggest that traffic is the major source of particle number emissions with the highest emissions observed for particles around 10 nm during rush hours. At sizes below 6 nm, clustering of atmospheric vapors contributes to calculated emissions. The comparison between our calculated emissions and those estimated with an integrated assessment model GAINS (Greenhouse Gas and Air Pollution Interactions and Synergies) shows that our method yields clearly higher particle emissions at sizes below 60 nm, but at sizes above that the two methods agree well. Overall, our method is proven to be a useful tool for gaining new knowledge of the size distributions of particle number emissions in urban environments and for validating emission inventories and models. In the future, the method will be developed by modeling the transport of particles from different sources to obtain more accurate estimates of particle number emissions.Peer reviewe

Deposition potential of 0.003-10 mu m ambient particles in the humidified human respiratory tract : Contribution of new particle formation events in Beijing

Ultrafine particles (UFPs) usually explosive growth during new particle formation (NPF) events. However, the risk of exposure to UFPs on NPF days has been ignored due to the prevalence of mass-based air quality standards. In this study, the daily deposited doses, i.e., the daily deposited particle number dose (D-PNd), mass dose (D-PMd), and surface area dose (D-PSd), of ambient particles in the human respiratory tract in Beijing were evaluated based on the particle number size distribution (3 nm-10 mu m) from June 2018 to May 2019 utilizing a Multiple-Path Particle Dosimetry Model (MPPD) after the hygroscopic growth of particles in the respiratory tract had been accounted for. Our observations showed a high frequency (72.6%) of NPF on excellent air quality days, with daily mean PM2.5 concentrations less than 35 mu g m(-3). The daily D-PNd on excellent air quality days was com-parable with that on polluted days, although the D-PMd on excellent air quality days was as low as 15.6% of that on polluted days. The D-PNd on NPF days was similar to 1.3 times that on non-NPF days. The D-PNd in respiratory tract regions decreased in the order: tracheobronchial (TB) > pulmonary (PUL) > extrathoracic (ET) on NPF days, while it was PUL > TB > ET on non-NPF days. The number of deposited nucleation mode particles, which were deposited mainly in the TB region (45%), was 2 times higher on NPF days than that on non-NPF days. Our results demonstrated that the deposition potential due to UFPs in terms of particle number concentrations is high in Beijing regardless of the aerosol mass concentration. More toxicological studies related to UFPs on NPF days, especially those targeting tracheobronchial and pulmonary impairment, are required in the future.Peer reviewe

Sources and sinks driving sulfuric acid concentrations in contrasting environments : implications on proxy calculations

Sulfuric acid has been shown to be a key driver for new particle formation and subsequent growth in various environments, mainly due to its low volatility. However, direct measurements of gas-phase sulfuric acid are oftentimes not available, and the current sulfuric acid proxies cannot predict, for example, its nighttime concentrations or result in significant discrepancies with measured values. Here, we define the sources and sinks of sulfuric acid in different environments and derive a new physical proxy for sulfuric acid to be utilized in locations and during periods when it is not measured. We used H2SO4 measurements from four different locations: Hyytiala, Finland; Agia Marina, Cyprus; Budapest, Hungary; and Beijing, China, representing semi-pristine boreal forest, rural environment in the Mediterranean area, urban environment and heavily polluted megacity, respectively. The new proxy takes into account the formation of sulfuric acid from SO2 via OH oxidation and other oxidation pathways, specifically via stabilized Criegee intermediates. The sulfuric acid sinks included in the proxy are its condensation sink (CS) and atmospheric clustering starting from H2SO4 dimer formation. Indeed, we found that the observed sulfuric acid concentration can be explained by the proposed sources and sinks with similar coefficients in the four contrasting environments where we have tested it. Thus, the new proxy is a more flexible and an important improvement over previous proxies. Following the recommendations in this paper, a proxy for a specific location can be derived.Peer reviewe

Molecular Composition of Oxygenated Organic Molecules and Their Contributions to Organic Aerosol in Beijing

The understanding at a molecular level of ambient secondary organic aerosol (SOA) formation is hampered by poorly constrained formation mechanisms and insufficient analytical methods. Especially in developing countries, SOA related haze is a great concern due to its significant effects on climate and human health. We present simultaneous measurements of gas-phase volatile organic compounds (VOCs), oxygenated organic molecules (OOMs), and particle-phase SOA in Beijing. We show that condensation of the measured OOMs explains 26-39% of the organic aerosol mass growth, with the contribution of OOMs to SOA enhanced during severe haze episodes. Our novel results provide a quantitative molecular connection from anthropogenic emissions to condensable organic oxidation product vapors, their concentration in particle-phase SOA, and ultimately to haze formation.Peer reviewe

Continuous and comprehensive atmospheric observations in Beijing : a station to understand the complex urban atmospheric environment

Peer reviewe

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

Discovery of the pyridylphenylureas as novel molluscicides against the invasive snail Biomphalaria straminea, intermediate host of Schistosoma mansoni

Abstract Background The snail Biomphalaria straminea is one of the intermediate hosts of Schistosoma mansoni. Biomphalaria straminea is also an invasive species, known for its strong capability on peripheral expansion, long-distance dispersal and colonization. Using molluscicides to control snail populations is an important strategy to interrupt schistosomiasis transmission and to prevent the spread of the invasive species. In this study, a series of pyridylphenylurea derivatives were synthesized as potential molluscicides. Their impact on adult snails and egg masses was evaluated. Acute toxicity to fish of the derivatives was also examined to assess their effect on non-target organisms. The preliminary mechanisms of action of the derivatives were studied by enzyme activity assays. Results The representative compounds, 1-(4-chlorophenyl)-3-(pyridin-3-yl)urea (compound 8) and 1-(4-bromophenyl)-3-(pyridin-3-yl)urea (compound 9), exhibited strong molluscicidal activity against adult snails with LD50 values of 0.50 and 0.51 mg/l and potent inhibitory effects on snail egg hatchability with IC50 values of 0.05 and 0.09 mg/l. Notably, both compounds showed good target specificity with potent molluscicidal capability observed in snails, but very low toxicity to local fishes. Furthermore, the exposure of compounds 8 and 9 significantly elevated the enzyme activities of acid phosphatase and nitric oxide synthase of the snails, while no significant change was recorded in the activities of alkaline phosphatase, acetylcholine esterase and superoxide dismutase. Conclusion The results suggested that compounds 8 and 9 of pyridylphenylurea derivatives could be developed as promising molluscicide candidates for snail control

Alisol B Alleviates Hepatocyte Lipid Accumulation and Lipotoxicity via Regulating RARα-PPARγ-CD36 Cascade and Attenuates Non-Alcoholic Steatohepatitis in Mice

Non-alcoholic steatohepatitis (NASH) is a common chronic liver disease worldwide, with no effective therapies available. Discovering lead compounds from herb medicine might be a valuable strategy for the treatment of NASH. Here, we discovered Alisol B, a natural compound isolated from Alisma orientalis (Sam.), that attenuated hepatic steatosis, inflammation, and fibrosis in high-fat diet plus carbon tetrachloride (DIO+CCl4)-induced and choline-deficient and amino acid-defined (CDA)-diet-induced NASH mice. RNA-seq showed Alisol B significantly suppressed CD36 expression and regulated retinol metabolism in NASH mice. In mouse primary hepatocytes, Alisol B decreased palmitate-induced lipid accumulation and lipotoxicity, which were dependent on CD36 suppression. Further study revealed that Alisol B enhanced the gene expression of RARα with no direct RARα agonistic activity. The upregulation of RARα by Alisol B reduced HNF4α and PPARγ expression and further decreased CD36 expression. This effect was fully abrogated after RARα knockdown, suggesting Alisol B suppressed CD36 via regulating RARα-HNF4α-PPARγ cascade. Moreover, the hepatic gene expression of RARα was obviously decreased in murine NASH models, whereas Alisol B significantly increased RARα expression and decreased CD36 expression, along with the downregulation of HNF4α and PPARγ. Therefore, this study showed the unrecognized therapeutic effects of Alisol B against NASH with a novel mechanism by regulating RARα-PPARγ-CD36 cascade and highlighted Alisol B as a promising lead compound for the treatment of NASH

Lychee Pulp-Derived Dietary Fiber-Bound Phenolic Complex Upregulates the SCFAs-GPRs-ENS Pathway and Aquaporins in Loperamide-Induced Constipated Mice by Reshaping Gut Microbiome

This study aimed to investigate the effects of the lychee pulp-derived dietary fiber-bound phenolic complex (DF-BPC) on a murine model of loperamide-induced constipation and its molecular mechanism associated with gut microbiota modification. DF-BPC supplementation mitigated loperamide-induced dyschezia, intestinal hypomotility, and colonic impairment, as evidenced by the increased gastro-intestinal transit rate and mucus cell counts. By comparison, short-chain fatty acids (SCFAs) contents and relative abundances of associated genera (Butyricimonas, Clostridium, and Lactobacillus) were effectively upregulated following DF-BPC supplementation. Notably, DF-BPC significantly enhanced expressions of G protein-coupled receptor (GPR) 41 and 43, reaching 1.43- and 1.62-fold increase, respectively. Neurotransmitter secretions were simultaneously altered in DF-BPC-treated mice, suggesting upregulation of the SCFAs-GPRs-enteric nervous system pathway. The overexpression of aquaporins (AQP3, 8, and 9) was stimulated partly through GPRs activation. Mild inflammation associated with constipation was inhibited by suppressing LBP-TLR4-NF-κB signaling translocation. These findings suggest that DF-BPC from lychee pulp has the potential to alleviate constipation in mice through modifying the gut microbiome

Effects of mold, water damage and window pane condensation on adult rhinitis and asthma partly mediated by different odors

A questionnaire survey was performed in eight Chinese cities (40,279 adults participated; response rate 75%). There were questions on demographic information of the participants, allergic rhinitis, asthma, perceived odors and home environment. The majority were women (74.7%) and 12.2% were smokers; 6.6% reported allergic rhinitis and 1.6% reported asthma. Totally 38% reported stuffy odor; 24.6% unpleasant odor; 11.5% pungent odor and 10.4% mold odor. Reporting of condensation on window panes were common (62.1%); visible mold or dampness stains (21.9%) and water damage (14.7%) were less common. All dampness indicators were associated with allergic rhinitis and asthma (OR = 1.34–1.87) and all odors (OR = 1.79–6.17). All odors were associated with allergic rhinitis and asthma (OR = 1.23–4.51). Odor perception was partly a mediator of the effects of mold and dampness on allergic rhinitis (% of total effect mediated: 2.7–9.8%) and asthma (2.2–10.7%) when adjusting for other home environment factors. Increased mediation effects for allergic rhinitis (% of total effect mediated: 11.2–17.4%) and asthma (% of total effect mediated: 5.5–14.7%) were found for total odor score (0–8) as compared to the mediation effects for four single odors. In conclusion, mold and dampness in dwellings were associated with adult allergic rhinitis, asthma and odors. Different odors were related to allergic rhinitis and asthma. Some of the effects of mold/dampness on allergic rhinitis and asthma were indirect effect mediated by odors from damp buildings, but most of the effects were direct effects