Nitro and oxy-PAHs bounded in PM2.5 and PM1.0 under different weather conditions at Mount Tai in Eastern China: Sources, long-distance transport, and cancer risk assessment

Fourteen nitro-PAHs and five oxy-PAHs associated with PM_2.5 and PM_1.0 were analyzed by GC-MS/MS at Mount Tai, China. 85% of the nitro-PAHs and 65% of oxy-PAHs were found in PM_1.0. The combined concentration of nitro-PAHs in PM_2.5 was highest in air masses associated with biomass burning (270.50pg/m³) compared with measurements from heavily polluted days (93.21pg/m³) and clean days (81.22pg/m³). A similar trend was also reflected in measurements of PM_1.0. 9-FO, 9,10-ANQ, and 1-NALD were the most abundant oxy-PAHs in both PM_2.5 and PM_1.0 at Mount Tai. The concentration of 2+3N-FLA was markedly increased compared with other species on heavily polluted days and biomass burning days, and 9N-ANT was more concentrated in measurements from days with biomass burning emissions. Secondary generation of nitro-PAHs was also more active during periods with biomass burning. The main formation pathway of nitro-PAHs during the sampling campaign was through reactions with OH radicals, but NO₃ radicals also played a significant role at night. The incremental lifetime cancer risk (ILCR) was highest during periods with biomass burning, indicating that biomass burning has a significant impact on human health. By analyzing the results of back trajectory clustering under different meteorological conditions, we determined that a large area of straw burning in the North China Plain (NCP) was the dominant source of nitro and oxy-PAHs at Mount Tai during the measurement campaign.

Trace elements in PM2.5 in Shandong Province: Source identification and health risk assessment

The chemical compositions in PM_2.5 in metropolitan areas have obtained lots of attentions, of which concerns of airborne trace elements are relatively lacking. Here, PM_2.5 samples were collected simultaneously in one year at four urban sites (Zibo (ZB), Zaozhuang (ZZ), Qingdao (QD) and Jinan (JN (Shandong University)), and a rural site (JN (Miaopu)) in Shandong province. 25 elements (Al, Na, Cl, Mg, Si, S, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Br, Sr, Cd, Ba and Pb) in PM_2.5 were measured by wavelength dispersive X-ray fluorescence spectrometer (WDXRF). Most trace elements (Al, Na, Cl, Mg, Si, Ca, Ti, Mn, Fe, Co, Ni, As, Se, Br, Cd, Ba and Pb) exhibited the highest levels at ZB and the lowest at QD. Meanwhile, they presented obvious seasonal variations with the highest concentrations in winter or spring and the lowest in summer. S and K were the most abundant elements in the area. In the non-crustal trace metal elements, Zn, Pb and Mn presented the highest concentrations. Positive matrix factorization (PMF) modeling revealed that secondary formation, coal combustion and industry emissions were the main sources in the region. The health risk assessments suggested that at the five sites Cd (diet) for adults, Pb and Co for children, and Mn (diet) for both adults and children (at ZB and SDU sites) had non-carcinogenic risks. As and Pb for adults and children existed carcinogenic risks, especially Pb for children. The sources of these elements with health risks were further explored. Notably, Cd, As and Pb should be paid special attention in the area due to their high concentrations in aerosol water exceeding the acceptable health risks, especially Pb.

The interaction of trace heavy metal with lipid monolayer in the sea surface microlayer

Lipid molecules and trace heavy metals are enriched in sea surface microlayer and can be transferred into the sea spray aerosol. To better understand their impact on marine aerosol generation and evolution, we investigated the interaction of trace heavy metals including Fe³⁺, Pb²⁺, Zn²⁺, Cu²⁺, Ni²⁺, Cr³⁺, Cd²⁺, and Co²⁺, with dipalmitoylphosphatidylcholine (DPPC) monolayers at the air-water interface. Phase behavior of the DPPC monolayer on heavy metal solutions was probed with surface pressure-area (π-A) isotherms. The conformation order and orientation of DPPC alkyl chains were characterized by infrared reflection-absorption spectroscopy (IRRAS). The π-A isotherms show that Zn²⁺ and Fe³⁺ strongly interact with DPPC molecules, and induce condensation of the monolayers in a concentration-dependent manner. IRRAS spectra show that the formation of cation-DPPC complex gives rise to conformational changes and immobilization of the headgroups. The current results suggest that the enrichment of Zn²⁺ in sea spray aerosols is due to strong binding to the DPPC film. The interaction of Fe³⁺ with DPPC monolayers can significantly influence their surface organizations through the formation of lipid-coated particles. These results suggest that the sea surface microlayer is capable of accumulating much higher amounts of these metals than the subsurface water. The organic and metal pollutants may transfer into the atmosphere by this interaction.

Gas-Phase Oxidation of Allyl Acetate by O3, OH, Cl, and NO3: Reaction Kinetics and Mechanism

Allyl acetate (AA) is widely used as monomer and intermediate in industrial chemicals synthesis. To evaluate the atmospheric outcome of AA, kinetics and mechanism of its gas-phase reaction with main atmospheric oxidants (O₃, OH, Cl, and NO₃) have been investigated in a Teflon reactor at 298 ± 3 K. Both absolute and relative rate methods were used to determine the rate constants for AA reactions with the four atmospheric oxidants. The obtained rate constants (in units of cm³ molecule^-1 s^-1) are (1.8 ± 0.3) × 10^-18, (3.1 ± 0.7) × 10^-11, (2.5 ± 0.5) × 10^-10, and (1.1 ± 0.4) × 10^-14, for reactions with O₃, OH, Cl, and NO_3, respectively. While results for reactions with O₃, OH and Cl are in good agreement with previous studies, the kinetics for the reaction with NO₃ is reported for the first time in this study. On the basis of determined rate constants, the tropospheric lifetimes of AA are τ_O3 = 9 days, τ_OH = 5 h, τ_Cl = 5 days, τ_NO3 = 2 days. On the basis of the products study, reaction mechanisms for these oxidations have been proposed and the reaction products were detected using thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS) and Fourier transform infrared spectroscopy (FTIR). Results show that the main products formed in these reactions are carbonyl compounds. In particular, 2-oxoethyl acetate was detected in all four AA oxidation reactions. Compared to previous studies, several new products were determined for reactions with OH and Cl. These results form a set of comprehensive kinetic data for AA reactions with main atmospheric oxidants and provide a better understanding of the degradation and atmospheric outcome of unsaturated acetate esters in the troposphere, during both daytime and nighttime.

Near-Infrared Upconversion Mesoporous Cerium Oxide Hollow Biophotocatalyst for Concurrent pH-/H2 O2 -Responsive O2 -Evolving Synergetic Cancer Therapy

Tumor hypoxia is typically presented in the central region of solid tumors, which is mainly caused by an inadequate blood flow and oxygen supply. In the conventional treatment of hypoxic human tumors, not only the oxygen-dependent photodynamic therapy (PDT), but also antitumor drug-based chemotherapy, is considerably limited. The use of direct oxygen delivering approach with oxygen-dependent PDT or chemotherapy may potentiate the reactive oxygen species (ROS)-mediated cytotoxicity of the drug toward normal tissues. Herein, a synergetic one-for-all mesoporous cerium oxide upconversion biophotocatalyst is developed to achieve intratumorally endogenous H₂ O₂ -responsive self-sufficiency of O₂ and near-infrared light controlled PDT simultaneously for overcoming hypoxia cancer. Furthermore, the sufficient O₂ plays an important role in overcoming the chemotherapeutic drug-resistant cancer caused by hypoxia, therefore inducing tumor cell apoptosis significantly.

Oxidizing capacity of the rural atmosphere in Hong Kong, Southern China

Atmospheric oxidizing capacity (AOC), dominated by the hydroxyl radical (OH), is an important index of the self-cleaning capacity of atmosphere and plays a vital role in the tropospheric chemistry. To better understand the key processes governing the chemistry of rural atmosphere of southern China, we analyzed the oxidation capacity and radical chemistry at a regional background site in Hong Kong from 23 August to 22 December 2012, which covered the summer, autumn and winter seasons. A chemical box model built on the latest Master Chemical Mechanism (v3.3) was used to elucidate the OH reactivity and sources of RO_X radicals (RO_X=OH+HO₂+RO₂). The AOC showed a clear seasonal pattern with stronger intensity in late summer compared to autumn and winter. Reactions with NO₂ (30%) and oxygenated volatile organic compounds (OVOCs) (31%) together dominated the OH loss in summer, while reactions with CO (38% in autumn and 39% in winter) and OVOCs (34% in autumn and 25% in winter) made larger contributions in autumn and winter. Photolysis of O₃ (36%-47%) presented the major RO_X source during all three seasons. The second largest ROx source was HONO photolysis (25%) in summer compared to HCHO photolysis in autumn (20%) and winter (21%). Besides, photolysis of other OVOCs was another important primary source of ROx radicals with average contributions of 14%, 13% and 20% for the summer, autumn and winter cases, respectively. Overall, the present study evaluates the oxidizing capacity of the rural atmosphere of South China and elucidates the varying characteristics of photochemical processes in different air masses.

A density functional theory study of aldehydes and their atmospheric products participating in nucleation

The products of aldehydes from aldol condensation, hydration, and polymerization reactions can promote new particle formation by stabilizing sulfuric acid.

The growth mechanism of polycyclic aromatic hydrocarbons from the reactions of anthracene and phenanthrene with cyclopentadienyl and indenyl

Polycyclic aromatic hydrocarbons (PAHs) are highly toxic, mutagenic and/or carcinogenic to humans. To reduce the emission of PAHs, it's significant and indispensable to explore the PAH formation mechanism. In the present work, the growth mechanism of PAHs from the reactions of anthracene and phenanthrene with cyclopentadienyl and indenyl radicals was investigated with the aid of high-accuracy quantum chemistry calculation. The rate constants of key elementary steps were calculated by meaning of the canonical variation transition-state (CVT) theory with the small curvature tunneling (SCT) correction over the temperature range of 400-1400 K. The mechanism of the PAH formation involves in six elementary steps, addition reaction, ring closure, intramolecular H-shift, cleavage of CC bond, intramolecular H-shift and unimolecular elimination of CH₃ or H. The cleavage of CC bond is the rate-determining step due to the high barrier. The formation of PAHs from the reactions of anthracene with cyclopentadienyl and indenyl radicals is easier than that from the reactions of phenanthrene.

Emissions of fine particulate nitrated phenols from the burning of five common types of biomass

Nitrated phenols are among the major constituents of brown carbon and affect both climates and ecosystems. However, emissions from biomass burning, which comprise one of the most important primary sources of atmospheric nitrated phenols, are not well understood. In this study, the concentrations and proportions of 10 nitrated phenols, including nitrophenols, nitrocatechols, nitrosalicylic acids, and dinitrophenol, in fine particles from biomass smoke were determined under three different burning conditions (flaming, weakly flaming, and smoldering) with five common types of biomass (leaves, branches, corncob, corn stalk, and wheat straw). The total abundances of fine nitrated phenols produced by biomass burning ranged from 2.0 to 99.5 μg m^-3. The compositions of nitrated phenols varied with biomass types and burning conditions. 4-nitrocatechol and methyl nitrocatechols were generally most abundant, accounting for up to 88-95% of total nitrated phenols in flaming burning condition. The emission ratios of nitrated phenols to PM_2.5 increased with the completeness of combustion and ranged from 7 to 45 ppmm and from 239 to 1081 ppmm for smoldering and flaming burning, respectively. The ratios of fine nitrated phenols to organic matter in biomass burning aerosols were comparable to or lower than those in ambient aerosols affected by biomass burning, indicating that secondary formation contributed to ambient levels of fine nitrated phenols. The emission factors of fine nitrated phenols from flaming biomass burning were estimated based on the measured mass fractions and the PM_2.5 emission factors from literature and were approximately 0.75-11.1 mg kg^-1. According to calculations based on corn and wheat production in 31 Chinese provinces in 2013, the total estimated emission of fine nitrated phenols from the burning of corncobs, corn stalks, and wheat straw was 670 t. This work highlights the apparent emission of methyl nitrocatechols from biomass burning and provides basic data for modeling studies.

Multiple factors impact the contents of heavy metals in vegetables in high natural background area of China

A field survey was conducted to investigate the concentrations of chromium (Cr), nickel (Ni), copper (Cu), zinc (Zn), cadmium (Cd) and lead (Pb) in vegetables, corresponding cultivated soils and irrigation waters from 36 open sites in high natural background area of Wuzhou, South China. Redundancy analysis, Spearman's rho correlation analysis and multiple regression analysis were adopted to evaluate the contributions of impacting factors on metal contents in the edible parts of vegetables. This study concluded that leafy and root vegetables had relatively higher metal concentrations and adjusted transfer factor values compared to fruiting vegetables according to nonparametric tests. Plant species, total soil metal content and soil pH value were affirmed as three critical factors with the highest contribution rate among all the influencing factors. The bivariate curve equation models for heavy metals in the edible vegetable tissues were well fitted to predict the metal concentrations in vegetables. The results from this case study also suggested that it could be one of efficient strategies for clean agricultural production and food safety in high natural background area to breed vegetable varieties with low heavy metal accumulation and to enlarge planting scale of these varieties.

Characteristics and impacts of trace elements in atmospheric deposition at a high-elevation site, southern China

To investigate the regional background trace element (TE) level in atmospheric deposition (dry and wet), TEs (Fe, Al, V, Cr, Mn, Ni, Cu, Zn, As, Se, Mo, Cd, Ba, and Pb) in 52 rainwater samples and 73 total suspended particles (TSP) samples collected in Mt. Lushan, Southern China, were analyzed using inductively coupled plasma-mass spectrometry (ICP-MS). The results showed that TEs in wet and dry deposition of the target area were significantly elevated compared within and outside China and the volume weight mean pH of rainwater was 4.43. The relative contributions of wet and dry depositions of TEs vary significantly among elements. The wet deposition fluxes of V, As, Cr, Se, Zn, and Cd exceeded considerably their dry deposition fluxes while dry deposition dominated the removal of pollution elements such as Mo, Cu, Ni, Mn, and Al. The summed dry deposition flux was four times higher than the summed wet deposition flux. Prediction results based on a simple accumulation model found that the content of seven toxic elements (Cr, Ni, Cu, Zn, As, Cd, and Pb) in soils could increase rapidly due to the impact of annual atmospheric deposition, and the increasing amounts of them reached 0.063, 0.012, 0.026, 0.459, 0.076, 0.004, and 0.145 mg kg^-1, respectively. In addition, the annual increasing rates ranged from 0.05% (Cr and Ni) to 2.08% (Cd). It was also predicted that atmospheric deposition induced the accumulation of Cr and Cd in surface soils. Cd was the critical element with the greatest potential ecological risk among all the elements in atmospheric deposition.

Facile Synthesis of Uniform Virus-like Mesoporous Silica Nanoparticles for Enhanced Cellular Internalization

The low-efficiency cellular uptake property of current nanoparticles greatly restricts their application in the biomedical field. Herein, we demonstrate that novel virus-like mesoporous silica nanoparticles can easily be synthesized, showing greatly superior cellular uptake property. The unique virus-like mesoporous silica nanoparticles with a spiky tubular rough surface have been successfully synthesized via a novel single-micelle epitaxial growth approach in a low-concentration-surfactant oil/water biphase system. The virus-like nanoparticles' rough surface morphology results mainly from the mesoporous silica nanotubes spontaneously grown via an epitaxial growth process. The obtained nanoparticles show uniform particle size and excellent monodispersity. The structural parameters of the nanoparticles can be well tuned with controllable core diameter (∼60-160 nm), tubular length (∼6-70 nm), and outer diameter (∼6-10 nm). Thanks to the biomimetic morphology, the virus-like nanoparticles show greatly superior cellular uptake property (invading living cells in large quantities within few minutes, <5 min), unique internalization pathways, and extended blood circulation duration (t1/2 = 2.16 h), which is much longer than that of conventional mesoporous silica nanoparticles (0.45 h). Furthermore, our epitaxial growth strategy can be applied to fabricate various virus-like mesoporous core-shell structures, paving the way toward designed synthesis of virus-like nanocomposites for biomedicine applications.

Theoretical study on the hydrolytic step in the biotransformation of β-hexachlorocyclohexane degraded by haloalkane dehalogenase LinB

The hydrolytic process of LinB-catalyzed biotransformation of a notorious contaminant β-HCH was investigated in atomistic detail with a combined quantum mechanics/molecular mechanics approach. The Boltzmann-weighted averaging method amended by disproportionate effect analysis was showed to capture the fluctuation of a single molecule enzyme reaction. With the potential barriers of 18.7 and 2.6 kcal/mol, two elementary steps that refer to formation and decomposition of a tetrahedral intermediate are involved in the hydrolytic reaction, respectively. Polarized by Glu132, His272 serves as a proton carrier along the whole hydrolysis reaction. The electrostatic influence analysis highlighted residue Leu248 as a possible mutation target for rational design of LinB in enzyme modification. Further spatial location analysis provided explanation for the opposite effect of Asn38 toward the two elementary steps. Getting insight into the catalytic details and the structure and function of LinB can enrich the knowledge of it and promote its application in bioremediation of chlorinated hydrocarbon pollutants.

Kinetics-mediate fabrication of multi-model bioimaging lanthanide nanoplates with controllable surface roughness for blood brain barrier transportation

Effective delivery of imaging agents or therapeutics to the brain has remained elusive due to the poor blood-brain barrier (BBB) permeability, resulting in the apparent risks of inefficient diagnosis and therapeutic agents for brain disease. Herein, we report on the surface roughness mediated BBB transportation for the first time. The lanthanide-based core/shell/shell structured NaYF₄:Yb,Er@NaGdF₄:Yb@NaNdF₄:Yb nanoplates with controllable surface roughness and multi-model bioimaging features were synthesized and used to evaluate the surface roughness dependent BBB permeability without any surface bio-functionalization. By controlling the kinetics of the shell coating process, the hexagon-disc, multi-petals and six-petals nanoplates with different surface roughness can be obtained. Comparing with the NPs with less Ra and receptor-conjugated NPs, the obtained six-petals nanoplates with highest roughness exhibit excellent performance in BBB transportation and tumor targeting, which lay solid foundation for the diagnosis and the therapy of brain tumor.

Molecular characterization, expression analysis and RNAi knock-down of elongation factor 1α and 1γ from Nilaparvata lugens and its yeast-like symbiont

In the present paper, four cDNAs encoding the alpha and gamma subunits of elongation factor 1 (EF-1) were cloned and sequenced from Nilaparvata lugens, named NlEF-1α, NlEF-1γ, and its yeast-like symbiont (YLS), named YsEF-1α and YsEF-1γ, respectively. Comparisons with sequences from other species indicated a greater conservation for EF-1α than for EF-1γ. NlEF-1α has two identical copies. The deduced amino acid sequence homology of NlEF-1α and NlEF-1γ is 96 and 64%, respectively, compared with Homalodisca vitripennis and Locusta migratoria. The deduced amino acid sequence homology of YsEF-1α and YsEF-1γ is 96 and 74%, respectively, compared with Metarhizium anisopliae and Ophiocordyceps sinensis. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis revealed that the expression level of NlEF-1α and NlEF-1γ mRNA in hemolymph, ovary, fat body and salivary glands were higher than the midgut and leg tissue. YsEF-1α and YsEF-1γ was highly expressed in fat body. The expression level of NlEF-1α was higher than that of NlEF-1γ. Through RNA interference (RNAi) of the two genes, the mortality of nymph reached 92.2% at the 11th day after treatment and the ovarian development was severely hindered. The RT-qPCR analysis verified the correlation between mortality, sterility and the down-regulation of the target genes. The expression and synthesis of vitellogenin (Vg) protein in insects injected with NlEF-1α and NlEF-1γ double-stranded RNA (dsRNA) was significantly lower than control groups. Attempts to knockdown the YsEF-1 genes in the YLS was unsuccessful. However, the phenotype of N. lugens injected with YsEF-1α dsRNA was the same as that injected with NlEF-1α dsRNA, possibly due to the high similarity (up to 71.9%) in the nucleotide sequences between NlEF-1α and YsEF-1α. We demonstrated that partial silencing of NlEF-1α and NlEF-1γ genes caused lethal and sterility effect on N. lugens. NlEF-1γ shares low identity with that of other insects and therefore it could be a potential target for RNAi-based pest management.

Enantioselectivity of haloalkane dehalogenase LinB on the degradation of 1,2-dichloropropane: A QM/MM study

The hydrolysis dechlorination mechanism of a chiral organochlorinepollutant, 1,2-dichloropropane (DCP), catalyzed by haloalkane dehalogenase LinB has been investigated by using a combined quantum mechanics/molecular mechanics method. LinB was confirmed to be enantioselective towards the catabolism of the racemic mixture. Based on the S_N2 nucleophilic substitution mechanism, the dechlorination process was identified as the rate-determining step in LinB-catalyzed degradation of 1,2-dichloropropane, the Boltzmann-weighted average potential barrier of which is 18.8kcal/mol for the (R)-isomer and 24.0kcal/mol for the (S)-isomer. A particular water molecule near (S)-DCP in the reaction system can strongly disturb the dechlorination process, which can account for the enantioselectivity of LinB. Further electrostatic influence analysis indicates that proper mutation of Gly37 may improve the catalytic efficiency of LinB towards DCP.

In vivo gastrointestinal drug-release monitoring through second near-infrared window fluorescent bioimaging with orally delivered microcarriers

Non-invasive monitoring of gastrointestinal drug release in vivo is extremely challenging because of the limited spatial resolution and long scanning time of existing bioimaging modalities, such as X-ray radiation and magnetic resonance. Here, we report a novel microcarrier that can retain drugs and withstand the harsh conditions of gastrointestinal tract. Significantly, we can track the microcarrier fate and semi-quantitatively monitor the content of drug released in vivo in real time by measuring the fluorescence signals in the second near-infrared window of lanthanide-based downconversion nanoparticles with an absorption competition-induced emission bioimaging system. The microcarriers show a prolonged residence time of up to 72 h in the gastrointestinal tract, releasing up to 62% of their content. Moreover, minimal deposition of the microcarriers is found in non-target organs, such as the liver, spleen and kidney. These findings provide novel insights for the development of therapeutic and bioimaging strategies of orally administered drugs.

Air pollution-aerosol interactions produce more bioavailable iron for ocean ecosystems

It has long been hypothesized that acids formed from anthropogenic pollutants and natural emissions dissolve iron (Fe) in airborne particles, enhancing the supply of bioavailable Fe to the oceans. However, field observations have yet to provide indisputable evidence to confirm this hypothesis. Single-particle chemical analysis for hundreds of individual atmospheric particles collected over the East China Sea shows that Fe-rich particles from coal combustion and steel industries were coated with thick layers of sulfate after 1 to 2 days of atmospheric residence. The Fe in aged particles was present as a "hotspot" of (insoluble) iron oxides and throughout the acidic sulfate coating in the form of (soluble) Fe sulfate, which increases with degree of aging (thickness of coating). This provides the "smoking gun" for acid iron dissolution, because iron sulfate was not detected in the freshly emitted particles and there is no other source or mechanism of iron sulfate formation in the atmosphere.

Bacterial characterization in ambient submicron particles during severe haze episodes at Ji'nan, China

In January 2014, severe haze episodes which sweep across Chinese cities have attracted public concern and interest at home and abroad. In addition to the physicochemical properties of air pollutants, bacteria are thought to be responsible for the spread of respiratory diseases and various allergies. We attempted the bacterial characterization of submicron particles (PM_0.18-0.32, PM_0.32-0.56, and PM_0.56-1) under severe haze episodes using high-throughput sequencing and real-time quantitative PCR detecting system based on 21 samples collected from January to March 2014 at Ji'nan, China. The high bacterial concentration in PM_0.32-0.56 (7314cells m^-3), PM_0.18-0.32 (7212cells m^-3), and PM_0.56-1 (6982cells m^-3) showed significant negative correlations with SO₂, NO_2, and O₃. Under sufficient sequencing depth, 37 phyla, 71 classes, 137 orders, 236 families, and 378 genera were classified, and the bacterial community structure varied significantly in different size fractions. For example, Holophagaceae (Acidobacteria) in PM_0.32-0.56 showed 6-fold higher abundance than that in PM_0.18-0.32. Moreover, functional categories and bacterial species (Lactococcus piscium, Pseudomonas fragi, Streptococcus agalactiae, and Pseudomonas cichorii) that may potentially be responsible for infections and allergies were also discovered. Source track analysis showed that the ambient bacteria mainly originated from soils, leaf surfaces, and feces. Our results highlighted the importance of airborne microbial communities by understanding the concentration, structure, ecological and health effects, especially those in submicron particles during haze episodes.

Investigation of diverse bacteria in cloud water at Mt. Tai, China

Bacteria are abundant in atmospheric water phase with the potential to influence atmospheric processes and human health, yet relatively little information is known about the bacterial characteristics at high altitudes. Here we investigated the bacterial community by high throughput sequencing in 24 cloud water samples collected from September 26 to October 31, at the summit of Mt. Tai (36°15' N, 117°06' E, 1534m a.s.l) in China. Diverse bacterial population were identified and the gram-negative bacteria contributed the majority of total bacteria including Proteobacteria (81.6%) and Bacteroidetes (3.9%), followed by gram-positive bacteria Firmicutes (7.1%) and Actinobacteria (2.3%). These gram-negative taxa mainly inhabited in leaf-surface and cold environments. Meanwhile bacteria involved in the cloud condensation nuclei and ice nuclei formation were observed such as Sphingomonas (6.7%), Pseudomonas (4.1%), and Bacillus (1.1%). In addition, Sphingmonas was more active than that in daytime and participated in the cloud chemistry process. Meanwhile O₃ and SO₂ critically contributed to the variation of bacterial community. It is the first report on the bacterial community structure of cloud water over Asian area. Our results can serve as an important reference for environmental scientists, and biologists.

Aqueous-phase aerosols on the air-water interface: Response of fatty acid Langmuir monolayers to atmospheric inorganic ions

Atmospheric aerosol particles composed of a mixture of organic and inorganic compounds are common and constitute an important fraction of air pollutants. In this study, the activities of common atmospheric inorganic ions (Ag⁺, Zn²⁺, Fe³⁺, Fe²⁺, Ca²⁺ and Al³⁺) and fatty acid molecules (stearic acid and arachidic acid) at air-aqueous interface were investigated by Langmuir methods and infrared reflection-absorption spectroscopy (IRRAS). In the presence of different inorganic ions, surface pressure-area isotherms of the Langmuir films showed compressed or expanded characteristics. IRRAS spectra confirmed that the existence of inorganic ions in the fatty acid monolayer changes the surface properties of aqueous-phase aerosols. Formation of different coordination types of carboxylates at the air-water interface alters the dissolution and partitioning behavior, which has significant influence of Raoult effect on nucleating cloud droplets. Our work displays the relationship between structure and surface properties for aqueous-phase aerosols and implies an efficient method for further understanding of their formation mechanism and potential atmospheric implications.

Influence of fireworks displays on the chemical characteristics of PM2.5 in rural and suburban areas in Central and East China

To explore the spatial and chemical characteristics of PM_2.5 pollution and the influence of fireworks displays on PM_2.5 and its chemical components in rural areas in Central and East China, PM_2.5 samples were collected at three rural sites and one suburban site in Henan and Shandong provinces during the 2016 Chinese New Year, and the chemical composition of PM_2.5, including water-soluble inorganic ions (WSIIs), organic carbon (OC), elemental carbon (EC), water-soluble organic carbon (WSOC) and trace elements (TEs) was analysed. The concentrations of PM_2.5 at the four sites were significantly higher than the Grade I national standard of 35μg/m³, indicating serious PM_2.5 pollution in rural and suburban areas. The contributions of secondary WSIIs to total WSIIs at the four sites were lower than in urban areas. The TEs in XP and LC were significantly enriched in PM_2.5. A significant difference was found in the main chemical compositions of different sites. Fireworks displays directly increased the concentrations of PM_2.5 and many chemicals, especially K⁺, Cl^-, K, Cl, S, Cu and Sr, and concentrations of NO₃^- and NH₄⁺ ions peaked after the fireworks period in the three rural sites, indicating the influence of firecrackers on the secondary formation of the precursors of NO₂. The ratio of WSOC/OC decreased during fireworks displays, indicating the direct influence of firecrackers on water insoluble organic matter. Fireworks-related ions were a key component of the aerosol at the four sites during fireworks displays, accounting for 28-38% of the total measured species.