Tire Wear Chemicals in the Urban Atmosphere: Significant Contributions of Tire Wear Particles to PM.

Tire wear particles (TWPs) containing tire wear chemicals (TWCs) are of global concern due to their large emissions and potential toxicity. However, TWP contributions to urban fine particles are poorly understood. Here, 72 paired gas-phase and PM samples were collected in the urban air of the Pearl River Delta, China.

Atmospheric brown carbon in China haze is dominated by secondary formation.

Brown carbon (BrC) is a class of light-absorbing organic aerosols (OA) and has significant influence on atmospheric radiative forcing. However, the current limited understanding of the physicochemical properties of BrC restricts the accurate evaluation of its environmental effects. Here the optical characteristics and chemical composition of BrC during wintertime in the Yangtze River Delta (YRD) region, China were measured by using high-resolution aerosol mass spectrometry (HR-AMS) and UV-vis spectrometry.

Secondary Formation of Atmospheric Brown Carbon in China Haze: Implication for an Enhancing Role of Ammonia.

Optical characteristics and molecular compositions of brown carbon (BrC) were investigated during winter 2019 at a rural site of China with a focus on nitro-aromatic compounds (NACs) and imidazoles (IMs). The abundance of gaseous nitrophenols relative to CO during the campaign maximized at noontime, being similar to O, while the particulate NACs during the haze periods strongly correlated with toluene and NO, suggesting that NACs in the region are largely formed from the gas-phase photooxidation. Strong correlations of particulate IMs in the dry haze periods with the mass ratio of EC/PM and the concentration of levoglucosan were observed, indicating that IMs during the dry events are largely derived from biomass burning emissions.

Ammonia in urban atmosphere can be substantially reduced by vehicle emission control: A case study in Shanghai, China.

To investigate the impact of emission controls on ammonia (NH) pollution in urban atmosphere, observation on NH (1 hr interval) was performed in Shanghai before, during and after the 2019 China International Import Expo (CIIE) event, along with measurements on inorganic ions, organic tracers and stable nitrogen isotope compositions of ammonium in PM. NH during the CIIE period was 6.5±1.

Increasing role of phenolic oxidative branch in daytime oxidation process of aromatics in Chinese haze period.

To understand the photooxidation mechanisms of aromatic compounds in the NOx-rich atmosphere, gaseous aromatics and their oxidization products (i.e., methyl glyoxal (MGLY), and nitrated phenols (NPs) including nitrophenols (NPhs) and methylnitrophenols (MNPs)) were measured with a 1-h time resolution on Chongming Island, a downwind region of the Yangtze River Delta (YRD) metropolitans of China in winter 2019 by using a proton-transfer-reaction mass spectrometer (PTR-MS).

Significant coal combustion contribution to water-soluble brown carbon during winter in Xingtai, China: Optical properties and sources.

To understand the characteristics of atmospheric brown carbon (BrC), daily PM samples in Xingtai, a small city in North China Plain (NCP), during the four seasons of 2018-2019, were collected and analyzed for optical properties and chemical compositions. The light absorption at 365 nm (abs) displayed a strong seasonal variation with the highest value in winter (29.0±14.

Gas-to-Aerosol Phase Partitioning of Atmospheric Water-Soluble Organic Compounds at a Rural Site in China: An Enhancing Effect of NH on SOA Formation.

Partitioning gaseous water-soluble organic compounds (WSOC) to the aerosol phase is a major formation pathway of atmospheric secondary organic aerosols (SOA). However, the fundamental mechanism of the WSOC-partitioning process remains elusive. By simultaneous measurements of both gas-phase WSOC (WSOCg) and aerosol-phase WSOC (WSOCp) and formic and acetic acids at a rural site in the Yangtze River Delta (YRD) region of China during winter 2019, we showed that WSOCg during the campaign dominantly partitioned to the organic phase in the dry period (relative humidity (RH) < 80%) but to aerosol liquid water (ALW) in the humid period (RH > 80%), suggesting two distinct SOA formation processes in the region.

Insights into high concentrations of particle-bound imidazoles in the background atmosphere of southern China: Potential sources and influencing factors.

Imidazoles are important constituents in atmospheric brown carbon and have gained increasing attention in the past decade. Although imidazoles have been studied widely in laboratories, the sparse field observations severely limit the understanding of imidazole's abundance and sources in the atmosphere. In this study, we measured particle-bound imidazoles and their precursors at a background forest site in the Nanling Mountains of southern China.

Important contribution of NO hydrolysis to the daytime nitrate in Xi'an, China during haze periods: Isotopic analysis and WRF-Chem model simulation.

Nitrate, as one of the major components of tropospheric aerosols, plays a crucial role in winter haze formation. While, the formation mechanism of the high production of nitrate in Chinese megacities is still not fully understood. To quantify the contributions of major formation pathways to nitrate, airborne particles in Xi'an, inland China during the winter of 2017 were measured and analyzed for the water-soluble ions and stable nitrogen/oxygen isotope compositions of nitrate in PM, followed by a WRF-Chem model simulation.

Spatial and Temporal Distributions and Sources of Anthropogenic NMVOCs in the Atmosphere of China: A Review.

As the key precursors of O, anthropogenic non-methane volatile organic compounds (NMVOCs) have been studied intensively. This paper performed a meta-analysis on the spatial and temporal variations of NMVOCs, their roles in photochemical reactions, and their sources in China, based on published research. The results showed that both non-methane hydrocarbons (NMHCs) and oxygenated VOCs (OVOCs) in China have higher mixing ratios in the eastern developed cities compared to those in the central and western areas.

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.

Efficient Heterogeneous Formation of Ammonium Nitrate on the Saline Mineral Particle Surface in the Atmosphere of East Asia during Dust Storm Periods.

To understand the chemical evolution of dust in the current East Asian atmosphere, the chemistry of PM and size-resolved aerosols in Shanghai, China, during the 2019 dust storm event was investigated. Our results showed that concentrations of SO in the city during the event highly correlated with Ca and Na due to the direct emissions of CaSO and NaSO from the upwind deserts. In contrast, during the event, NO linearly correlated with NH at a molar ratio close to 1:1, and both almost entirely stayed in coarse particles, suggesting they accumulated on the dust surface as NHNO.

The safety of tai chi: A meta-analysis of adverse events in randomized controlled trials.

Objectives: To review current publications to examine safety of tai chi (TC).

Design: Cochrane Library, EBSCO host and MEDLINE/PubMed were searched for randomized controlled trials (RCTs) including TC as the core intervention and reporting adverse events (AEs). Data were extracted considering active vs.

Dexmedetomidine attenuates spinal cord ischemia-reperfusion injury through both anti-inflammation and anti-apoptosis mechanisms in rabbits.

Background: Dexmedetomidine (Dex) can improve neuronal viability and protect the spinal cord from ischemia-reperfusion (I/R) injury, but the underlying mechanisms are not fully understood. This study investigated the effects of dexmedetomidine on the toll-like receptor 4 (TLR4)-mediated nuclear factor κB (NF-κB) inflammatory system and caspase-3 dependent apoptosis induced by spinal cord ischemia-reperfusion injury.

Methods: Twenty-four rabbits were divided into three groups: I/R, Dex (10 µg/kg/h prior to ischemia until reperfusion), and Sham.

BMI, leisure-time physical activity, and physical fitness in adults in China: results from a series of national surveys, 2000-14.

Background: Obesity, physical inactivity, and reduced physical fitness contribute to the rising burden of chronic diseases in China. We investigated these factors in Chinese adults over a 14-year period (2000-14) using data from randomised national surveys.

Methods: We did four national surveys in 2000, 2005, 2010, and 2014 among Chinese adults aged 20-59 years.