Atmospheric sulfate aerosol formation enhanced by interfacial anions.

Heterogeneous oxidation of SO by NO on aerosols has recently been found to be one of the major formation pathways of sulfate in the polluted troposphere, but the chemical mechanisms and kinetics remain uncertain. By combining lab experiments, theoretical chemistry calculations, and field measurements, here we show that the SO oxidation by NO is critically dependent on anions at the air-aerosol aqueous interface. The reaction rate of NO with (1.

Elucidating the Mechanism on the Transition-Metal Ion-Synergetic-Catalyzed Oxidation of SO with Implications for Sulfate Formation in Beijing Haze.

Currently, atmospheric sulfate aerosols cannot be predicted reliably by numerical models because the pathways and kinetics of sulfate formation are unclear. Here, we systematically investigated the synergetic catalyzing role of transition-metal ions (TMIs, Fe/Mn) in the oxidation of SO by O on aerosols using chamber experiments. Our results showed that the synergetic effect of TMIs is critically dependent on aerosol pH due to the solubility of Fe(III) species sensitive to the aqueous phase acidity, which is effective only under pH < 3 conditions.

Study on the Initiation of Interface Crack in Rock Joints.

The interfacial fracture of rock joints is an important although easily ignored issue in jointed rock engineering. To conduct this study, an interface crack model of rock joints was proposed. By analyzing the ratio of stress intensity factor to fracture toughness, the fracture mode of the interface crack was studied.

Aerosol liquid water content of PM and its influencing factors in Beijing, China.

Aerosol liquid water content (ALWC) has important influences on atmospheric radiation and aerosol chemical processes. In this work, the changes in ALWC of PM were investigated over four seasons based on hourly monitoring of inorganic water-soluble ions and their gaseous precursors using the thermodynamic model ISORROPIA II. The results showed that the ALWC concentrations exhibited pronounced seasonal (autumn > summer > spring > winter) and diurnal variation characteristics.

Smog chamber simulation on heterogeneous reaction of O and NO on black carbon under various relative humidity conditions.

In this study, heterogeneous formation of nitrate from O reaction with NO on black carbon (BC) and KCl-treated BC surface in the presence of NH was simulated under 30-90% RH conditions by using a laboratory smog chamber. We found that O and NO in the chamber quickly reacted into NO in the gas phase which subsequently hydrolyzed into HNO and further neutralized with NH into NHNO on the BC surface, along with a small amount of NO decomposed into NO and NO through a reaction with the BC surface active site. Meanwhile, the fractal BC aggregates restructured and condensed to spherical particles during the NHNO coating process.

Enhancing effect of NO on the formation of light-absorbing secondary organic aerosols from toluene photooxidation.

Aromatic hydrocarbons are one of the major precursors of atmospheric brown carbon (BrC) and both abundantly co-exist with NO in the urban atmosphere especially in winter haze period. However, the impact of NOx on the formation of BrC derived from aromatic hydrocarbons is still not fully understood. In this study, the yield and light absorption of secondary organic aerosols (SOA) from toluene photooxidation under various nitrogen oxides (NO) levels were investigated by using a 5 m photooxidation smog chamber.

Influence of COVID-19 lockdown overlapping Chinese Spring Festival on household PM in rural Chinese homes.

During the 2019 novel coronavirus (COVID-19) pandemic, many countries took strong lockdown policy to reduce disease spreading, resulting in mitigating the ambient air pollution due to less traffic and industrial emissions. However, limited studies focused on the household air pollution especially in rural area, the potential risk induced by indoor air pollution exposure was unknown during this period. This field study continuously measured real-time PM levels in kitchen, living room, and outdoor in the normal days (Period-1) and the days of COVID-19 lockdown overlapping the Chinese Spring Festival (Period-2) in rural homes in China.

Rapid sulfate formation from synergetic oxidation of SO by O and NO under ammonia-rich conditions: Implications for the explosive growth of atmospheric PM during haze events in China.

Extremely high levels of atmospheric sulfate aerosols have still frequently occurred in China especially in winter haze periods and often been underestimated by models due to some missing formation mechanisms. Here we investigated the heterogeneous reaction dynamics of SO oxidation by the abundantly co-existing O and NO in the urban atmosphere of China by using a laboratory smog chamber simulation technique. Our results showed that with an increase of NH concentrations from 0.

Non-agricultural sources dominate the atmospheric NH in Xi'an, a megacity in the semi-arid region of China.

Ammonia (NH), as a dominant alkaline gas in the atmosphere, plays a vital role in Chinese urban haze formation process, but its source in urban areas of China is controversial. To identify the sources of urban NH in the semi-arid region of East Asia, real-time measurements of NH and NH of PM in the urban atmosphere of Xi'an, inland China during the winter and summer of 2017 were performed and their stable nitrogen isotope composition were analyzed. NH was 38.

Enhanced aqueous-phase formation of secondary organic aerosols due to the regional biomass burning over North China Plain.

This study reveals the impact of biomass burning (BB) on secondary organic aerosols (SOA) formation in the North China Plain (NCP). Filter samples were analyzed for secondary inorganic aerosols (SIA), oxalic acid (C) and related aqueous-phase SOA compounds (aqSOA), stable carbon isotope composition of C (δC(C)) and aerosol liquid water content (ALWC). Based on the PM loadings, BB tracer concentrations, wildfire spots and air-mass back trajectories, we distinguished two episodes from the whole campaign, Episode I and Episode II, which were characteristic of regional and local BB, respectively.

Abundant NH in China Enhances Atmospheric HONO Production by Promoting the Heterogeneous Reaction of SO with NO.

High levels of HONO have frequently been observed in Chinese haze periods and underestimated by current models due to some unknown sources and formation mechanisms. Combining lab-chamber simulations and field measurements in Xi'an and Beijing, China, we found that NH can significantly promote HONO formation via the reduction-oxidation of SO with NO in the aqueous phase of hygroscopic particles (e.g.

Chemical characteristics of airborne particles in Xi'an, inland China during dust storm episodes: Implications for heterogeneous formation of ammonium nitrate and enhancement of N-deposition.

To identify the sources and heterogeneous reactions of sulfate and nitrate with dust in the atmosphere, airborne particles in Xi'an, inland China during the spring of 2017 were collected and measured for chemical compositions, along with a laboratory simulation of the heterogeneous formation of ammonium nitrate on the dust surface. Our results showed that concentrations of Ca, Na and Cl in the TSP samples were enhanced in the dust events, with the values of 41.8, 5.

Novel Soluble Dietary Fiber-Tannin Self-Assembled Film: A Promising Protein Protective Material.

In this experiment, a natural promising protein protective film was fabricated through soluble dietary fiber (SDF)-tannin nanocluster self-assembly. FT-IR, XRD, and DSC tests were employed to investigate the interaction between the SDF and tannins before and after cross-linking induced by calcium ion. On the other hand, referring to the SEM and TEM results, the self-assembly process of the protein protective film could be indicated as follows: first, calcium ion, with its cross-ability, served as the "nucleus"; SDF and tannins were combined to prepare the nanoscale SDF-tannin clusters; then, the clusters were homogeneously deposited on the surface of protein to form a protective film by self-assembling hydrogen bond between tannin component of clusters as "adhesive" and protein in aqueous solutions under very mild conditions.