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•Size-resolved special POA and BSOA were measured using GC/MS.•Anthropologic POA and most BSOA were enriched in the fine mode (<1.1 µm).•The organics size distribution was related to ...their source and formation mechanism.
Organic aerosols are important constituents of particulate matter (PM) in the atmosphere, however, the studies on their size distribution, particularly for special primary and secondary organic aerosols (POA, SOA), are relatively limited. In this work, the size-segregated PM was collected from five megacities (Shanghai, Guangzhou, Xi’an, Chengdu, Urumqi) and a continental background site (Qinghai Lake, Tibetan Plateau) of China during 2012–2014. Special POA (plant wax n-alkanes, fossil fuel n-alkanes, PAHs, levoglucosan, and trehalose) and biogenic SOA (BSOA, i.e. isoprene oxidants, monoterpene oxidants, and β-caryophyllenic acid) in PM were measured using gas chromatography/mass spectrometry. n-Alkanes were highest in autumn in the Southeast of China and highest in summer in the Northwest of China during the four seasons. PAHs and levoglucosan were higher in the cold season, mainly influenced by residential heating. Isoprene and monoterpene oxidants were higher in the warm season, while β-caryophyllenic acid was found to be much higher in cold seasons. n-Alkanes showed a monomodal distribution, with a peak at the fine mode (<1.1 µm). PAHs and levoglucosan were characterized by an accumulation mode, revealing the peak at <1.1 µm. However, only trehalosedisplayed coarse mode at the six sites, peaking at a size of 3.3–9.0 µm, because it was mostly derived frombiota in desert regions. Isoprene oxidants including 2-methylglyceric acid, 2-methyltetrols, and C5-alkene triols exhibited a unimodal size distribution pattern with a peak in the fine mode. Monoterpene oxidants such as cis-pinic acid, pinonic acid, 3-hydroxyglutaric acid, and 3-methyl-1,2,3-butanetricarboxylic acid exhibited a bimodal size distribution pattern in the whole sampling time, peaking at the size range of <1.1 µm and 3.3–9.0 µm, respectively. Only β-caryophyllenic acid displayed a fine mode at the six sites during the whole sampling time. These findings can be used to support research into the origin and formation mechanisms of POA and BSOA.
Sulfate aerosols exert profound impacts on human and ecosystem health, weather, and climate, but their formation mechanism remains uncertain. Atmospheric models consistently underpredict sulfate ...levels under diverse environmental conditions. From atmospheric measurements in two Chinese megacities and complementary laboratory experiments, we show that the aqueous oxidation of SO₂ by NO₂ is key to efficient sulfate formation but is only feasible under two atmospheric conditions: on fine aerosols with high relative humidity and NH₃ neutralization or under cloud conditions. Under polluted environments, this SO₂ oxidation process leads to large sulfate production rates and promotes formation of nitrate and organic matter on aqueous particles, exacerbating severe haze development. Effective haze mitigation is achievable by intervening in the sulfate formation process with enforced NH₃ and NO₂ control measures. In addition to explaining the polluted episodes currently occurring in China and during the 1952 London Fog, this sulfate production mechanism is widespread, and our results suggest a way to tackle this growing problem in China and much of the developing world.
Thirteen secondary organic aerosol (SOA) tracers of isoprene, monoterpenes and sesquiterpenes were measured for PM2.5 aerosols collected at the summit of Mt. Wuyi (1139 m, a.s.l.), to investigate ...their seasonality and formation mechanism. Concentrations of the isoprene and monoterpene SOA tracers were much higher in summer than those in other seasons. In contrast, β-caryophyllinic acid was found to be the lowest in summer. Concentrations of those BSOA tracers showed a positive correlation with temperature (R2 = 0.52–0.70), and a negative correlation with relative humidity (R2 = 0.43–0.78). Moreover, thermodynamic model (i.e., ISORROPIA-II) calculation results showed that acidity conditions are favorable for BSOA formation. Robust linear correlations between the BSOA tracers and anthropogenic pollutants such as SO2 (R2 = 0.53–0.7) and NO2 (R2 = 0.37–0.54) were observed for all the samples, suggesting that SO2 and NOx can enhance BSOA production in the remote mountain area of southeast China, which is related to an acid-catalyzed heterogeneous chemistry. Moreover, we also found a significant correlation between the concentrations of the BSOA tracers and levoglucosan especially for β-caryophyllinic acid, indicating that biomass burning plumes from the distant lowland regions could influence the production of BSOA in the mountain free troposphere. Our results clearly demonstrated that anthropogenic emissions in China could enhance BSOA formation in the distant mountain regions.
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•Some known biogenic SOA tracers in PM2.5 are measured at the summit of Mt.Wuyi.•Concentrations of biogenic SOA tracers are most abundant in summer.•Anthropogenic pollutants can enhance biogenic SOA formation.
Anthropogenic pollutants can enhance biogenic SOA formation.
A unique avian-origin A/H7N9 influenza virus has so far caused 134 cases with 44 deaths. Probing the host factors contributing to disease severity, we found that lower levels of plasma inflammatory ...cytokines on hospital admission correlated with faster recovery in 18 patients with A/H7N9 influenza virus, whereas high concentrations of (in particular) IL-6, IL-8, and macrophage inflammatory protein-1β were predictive of a less favorable or fatal outcome. Analysis of bronchoalveolar lavage samples showed up to 1,000-fold greater cytokine/chemokine levels relative to plasma. Furthermore, patients with the rs12252-C/C IFN-induced transmembrane protein-3 (IFITM3) genotype had more rapid disease progression and were less likely to survive. Compared with patients with the rs12252-T/T or rs12252-T/C genotype of IFITM3, patients with the C/C genotype had a shorter time from disease onset to the time point when they sought medical aid (hospital admission or antiviral therapy) and a shorter interval to development of the acute respiratory distress syndrome stage (reflected by shorter intervals between clinical onset and methylprednisolone treatments and higher rates of mechanical ventilator use), as well as experiencing elevated/prolonged lung virus titers and cytokine production and higher mortality. The present analysis provides reported data on the H7N9 influenza-induced “cytokine storm” at the site of infection in humans and identifies the rs12252-C genotype that compromises IFITM3 function as a primary genetic correlate of severe H7N9 pneumonia. Together with rs12252 sequencing, early monitoring of plasma cytokines is thus of prognostic value for the treatment and management of severe influenza pneumonia.
Isoprene is the most abundant non-methane volatile organic compound (VOC) and the largest contributor to secondary organic aerosol (SOA) burden on a global scale. In order to examine the influence of ...high concentrations of anthropogenic pollutants on isoprene-derived SOA (SOA
) formation, summertime PM
filter samples were collected with a three-hour sampling interval at a rural site in the North China Plain (NCP), and determined for SOA
tracers and other chemical species. RO
+NO pathway derived 2-methylglyceric acid presented a relatively higher contribution to the SOA
due to the high-NOx (~20 ppb) conditions in the NCP that suppressed the reactive uptake of RO
+HO
reaction derived isoprene epoxydiols. Compared to particle acidity and water content, sulfate plays a dominant role in the heterogeneous formation process of SOA
. Diurnal variation and correlation of 2-methyltetrols with ozone suggested an important effect of isoprene ozonolysis on SOA
formation. SOA
increased linearly with levoglucosan during June 10-18, which can be attributed to an increasing emission of isoprene caused by the field burning of wheat straw and a favorable aqueous SOA formation during the aging process of the biomass burning plume. Our results suggested that isoprene oxidation is highly influenced by intensive anthropogenic activities in the NCP.
Severe influenza A virus (IAV) infection is associated with immune dysfunction. Here, we show circulating CD8
T-cell profiles from patients hospitalized with avian H7N9, seasonal IAV, and influenza ...vaccinees. Patient survival reflects an early, transient prevalence of highly activated CD38
HLA-DR
PD-1
CD8
T cells, whereas the prolonged persistence of this set is found in ultimately fatal cases. Single-cell T cell receptor (TCR)-αβ analyses of activated CD38
HLA-DR
CD8
T cells show similar TCRαβ diversity but differential clonal expansion kinetics in surviving and fatal H7N9 patients. Delayed clonal expansion associated with an early dichotomy at a transcriptome level (as detected by single-cell RNAseq) is found in CD38
HLA-DR
CD8
T cells from patients who succumbed to the disease, suggesting a divergent differentiation pathway of CD38
HLA-DR
CD8
T cells from the outset during fatal disease. Our study proposes that effective expansion of cross-reactive influenza-specific TCRαβ clonotypes with appropriate transcriptome signatures is needed for early protection against severe influenza disease.
Chemical evolution of East Asian dust during transpacific transport has been given much attention for inorganic species such as sulfate, nitrate and ammonium. However, the role of organic species ...during the transport has almost entirely been ignored. To understand the formation mechanism of secondary organic aerosols (SOA) on dust surfaces, this study investigated the concentrations and compositions of dicarboxylic acids, keto-carboxylic acids, α-dicarbonyls and inorganic ions in size-segregated aerosols (9-stages) collected in Xi'an, central China during the two dust storm episodes in the springs of 2009 and 2011 and compared with those in nondust storm periods. During the events the ambient particulate dicarboxylic acids were 932–2240 ng m−3, which are comparable and even higher than those in nondust periods. Molecular compositions of the above SOA are similar to those in nondust periods with oxalic acid being the leading species. In the presence of the dust storms, all the above mentioned SOA species in Xi'an were predominantly enriched on the coarse particles (>2.1 μm), and oxalic acid well correlated with NO3− (R2 = 0.72, p < 0.001) rather than SO42−. This phenomenon differs greatly from the SOA in any other nondust period that is usually characterized by an enrichment of oxalic acid in fine mode and a strong correlation of oxalic acid with SO42−. We propose a formation pathway to explain these observations, in which nitric acid and/or nitrogen oxides react with dust to produce Ca(NO3)2 and form a liquid phase on the surface of dust aerosols via water vapor-absorption of Ca(NO3)2, followed by a partitioning of the gas-phase water-soluble organic precursors (e.g.,glyoxal and methylglyoxal) into the aqueous-phase and a subsequent oxidation into oxalic acid. To the best of our knowledge, we found for the first time the enrichment of glyoxal and methylglyoxal on dust surface. Our data suggest an important role of nitrate in the heterogeneous formation process of SOA on the surface of dust.
•High concentration of oxalic acid observed during the dust events.•Oxalic acid, glyoxal and methylglyoxal dominated in coarse particles.•Aqueous-phase formation of oxalic acid on dust surface.
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•Thermal stabilities of cyclo-CXCXCF2CF2CF2(X = H, F) were under condition of 500–850 ℃.•Pyrolysis products and mechanisms of the reactants are proposed.•Negligible climate change ...influences of 6FE, 7FE and 8FE were discussed.
3,3,4,4,5,5-hexafluorocyclopentene (6FE), 1,3,3,4,4,5,5-heptafluorocyclopentene (7FE) and octafluorocyclopentene (8FE) are considered as new generation of potential chlorofluorocarbons substitutes. To investigate the thermostabilities, tubular furnace experiments were designed over temperature range of 500-850℃. The results show that 6FE, 7FE and 8FE are all stable below 650 ℃, thus have good stabilities in common storage and practical use condition. Furthermore, considering the short atmospheric lifetimes (several months), low global warming potentials (GWPs, less than 119) and zero ozone depletion potentials (ODPs), the compounds seem no big influences on the climate change.
The Intact Proviral DNA Assay (IPDA) was developed to address the critical need for a scalable method for intact HIV-1 reservoir quantification. This droplet digital PCR-based assay simultaneously ...targets two HIV-1 regions to distinguish genomically intact proviruses against a large background of defective ones, and its application has yielded insights into HIV-1 persistence. Reports of assay failures however, attributed to HIV-1 polymorphism, have recently emerged. Here, we describe a diverse North American cohort of people with HIV-1 subtype B, where the IPDA yielded a failure rate of 28% due to viral polymorphism. We further demonstrate that within-host HIV-1 diversity can lead the IPDA to underestimate intact reservoir size, and provide examples of how this phenomenon could lead to erroneous interpretation of clinical trial data. While the IPDA represents a major methodological advance, HIV-1 diversity should be addressed before its widespread adoption as a principal readout in HIV-1 remission trials.
Concentrations and compositions of PAHs and oxygenated PAHs (OPAHs) in four size ranges of ambient particles (<1.1, 1.1–3.3, 3.3–9.0 and >9.0μm) collected in Xi'an and Guangzhou, two megacities of ...China, during the winter and summer of 2013 were measured and compared with those in 2003. The TSP-equivalent concentrations of Σ14PAHs in Xi'an and Guangzhou are 57±20 and 18±23ngm−3 in winter, 5–10 times higher than those in summer. PAHs in both cities are dominated by 5- and 6-ring congeners in summer. In contrast, they are dominated by 4- and 5-ring congeners in winter, probably due to enhanced gas-to-particle phase partitioning of the semi-volatile PAHs. TSP-equivalent Σ7OPAHs during winter are 54±15 and 23±32ngm−3 in Xi'an and Guangzhou and dominated by 5-ring OPAHs.
Size distribution results showed that the fine modes (<3.3μm) of PAHs and OPAHs in both cities are dominated by 4- and 5-ring congeners in winter and 5- and 6-ring congeners in summer. Relative abundances of 3-ring PAHs and OPAHs increased along with an increase in particle sizes, accounting for from about 1% of the total PAHs or OPAHs in the smallest particles (<1.1μm) to >90% of the total in the largest particles (>9.0μm). The toxicity of PAH assessment indicated that atmospheric particles in Xi'an and Guangzhou during winter are much more toxic than those during summer and fine particles are more toxic than coarse particles. Compared to those in 2003, fine particulate PAHs and OPAHs in both cities during winter decreased by 50–90%, most likely due to the replacement of coal by natural gas in the country.
•Size-resolved PAHs and OPAHs in China were measured.•4-/5-ring PAHs dominate in winter, while 5-/6-ring PAHs dominate in summer.•BaP/BeP ratios indicate current atmosphere of China more oxidative.•PAHs and OPAHs in 2013 decreased by 50–90% compared to those in 2003
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