HONO plays a key role in atmospheric chemistry, and while its importance is well-known, the sources of HONO are still not completely understood. As a component of ambient HONO sources, direct emission from vehicles is an area that should be extensively studied. In this study, we determined the HONO emission index for typical gasoline vehicles in the car population of China through a chassis dynamometer with different types of engines (PFI/GDI), starting conditions (cold/warm) and running styles (Beijing cycle). Emission ratios of HONO to nitrogen oxide (NOx) for the Chinese gasoline cars are determined to be in the range of (0.03-0.42) % and an averaged value is about 0.18%, which are comparable to those reported in the few studies available in Europe, the United States and Japan for gasoline cars while smaller for those of the diesel cars. The atmospheric impact of the direct HONO emission from gasoline cars was analyzed for a typical urban site in Beijing, significant contributions of the direct emission toward the HONO budget were found during morning rush hours or twilight conditions to be 8-12%. (C) 2017 Published by Elsevier Ltd.
Catalyst-free methods are important for the fabrication of pure nanowires (NWs). However, the growth mechanism remains elusive due to the lack of crucial information on the growth dynamics at atomic level. Here, the noncatalytic growth process of ZnO NWs is studied through in situ high resolution transmission electron microscopy. We observe the layer-by-layer growth of ZnO nanopillars along the polar [0001] direction under electron beam irradiation, while no growth is observed along the radial directions, indicating an anisotropic growth mechanism. The source atoms are mainly from the electron beam induced damage of the sample and the growth is assisted by subsequent absorption and then diffusion of atoms along the side surface to the top (0002) surface. The different binding energy on different ZnO surface is the main origin for the anisotropic growth. Additionally, the coalescence of ZnO nanocrystals related to the nucleation stage is uncovered to realize through the rotational motions and recrystallization. Our in situ results provide atomic-level detailed information about the dynamic growth and coalescence processes in the noncatalytic synthesis of ZnO NW and are helpful for understanding the vapor-solid mechanism of catalyst-free NW growth.
Many studies have focused on the physicochemical properties of aerosol particles in unusually severe hazeepisodes in North China instead of the more frequent and lesssevere hazes. Consistent with this lack of attention, the morphology and mixing state of organic matter (OM) particles inthe frequent light and moderate (L & M) hazes in winter inthe North China Plain (NCP) have not been examined, eventhough OM dominates these fine particles. In the presentwork, morphology, mixing state, and size of organic aerosolsin the L & M hazes were systematically characterized using transmission electron microscopy coupled with energydispersive X-ray spectroscopy, atomic force microscopy, andnanoscale secondary ion mass spectrometer, with the comparisons among an urban site (Jinan, S1), a mountain site(Mt. Tai, S2), and a background island site (Changdao, S3)in the same hazes. Based on their morphologies, the OM particles were divided into six different types: spherical (type 1),near-spherical (type 2), irregular (type 3), domelike (type 4),dispersed-OM (type 5), and OM-coating (type 6). In the threesampling sites, types 1–3 of OM particles were most abundant in the L & M hazes and most of them were internallymixed with non-OM particles. The abundant near-sphericalOM particles with higher sphericity and lower aspect ratioindicate that these primary OM particles formed in the cooling process after polluted plumes were emitted from coalcombustion and biomass burning. Based on the Si-O-C ratio in OM particles, we estimated that 71 % of type 1–3 OMparticles were associated with coal combustion. Our resultsuggests that coal combustion in residential stoves was awidespread source from urban to rural areas in NCP. AverageOM thickness which correlates with the age of the air massesin type 6 particles only slightly increased from S1 to S2 to S3,suggesting that the L & M hazes were usually dry (relativehumidity < 60 %) with weak photochemistry and heterogeneous reactions between particles and gases. We concludethat the direct emissions from these coal stoves without anypollution controls in rural areas and in urban outskirts contribute large amounts of primary OM particles to the regionalL & M hazes in North China.
Compared with conventional accelerators, laser plasma accelerators can generate high energy ions at a greatly reduced scale, due to their TV/m acceleration gradient. A compact laser plasma accelerator (CLAPA) has been built at the Institute of Heavy Ion Physics at Peking University. It will be used for applied research like biological irradiation, astrophysics simulations, etc. A beamline system with multiple quadrupoles and an analyzing magnet for laser-accelerated ions is proposed here. Since laser-accelerated ion beams have broad energy spectra and large angular divergence, the parameters (beam waist position in the Y direction, beam line layout, drift distance, magnet angles etc.) of the beamline system are carefully designed and optimised to obtain a radially symmetric proton distribution at the irradiation platform. Requirements of energy selection and differences in focusing or defocusing in application systems greatly influence the evolution of proton distributions. With optimal parameters, radially symmetric proton distributions can be achieved and protons with different energy spread within +/- 5% have similar transverse areas at the experiment target.
Why are contemporary populations still aging? In the classic view, population aging has been driven almost entirely by fertility decline over the demographic transition, while mortality decline has played a minor role. In this view, populations today are still aging because they are still converging toward the new older stable age distribution. But in the past 25 years an elegant mathematical decomposition of changing mean ages has sometimes been interpreted as showing that recent aging is mainly due to declining mortality rather than fertility. Here we question this interpretation and argue that it is necessary to evaluate the indirect effects of mortality change as well as the direct ones. We suggest that the gold standard for this problem is the analytic simulation with explicit counterfactual comparisons. Analytic simulations show that fertility decline is largely responsible for the old age of contemporary populations and has by far the largest role in accounting for continuing aging from 2005–2010.
Trifluoroacetic acid (TFA) in the atmosphere is produced by degradation of hydrochlorofluorocarbons and hydrofluorocarbons. In recent years, TFA has attracted global attention because of increased environmental concentrations, biological toxicity and accumulation in aqueous environments. This study focused on the mechanisms underlying the adsorption of TFA by particulate matter to identify the appropriate descriptive model for this process and thus improve estimation of TFA adsorption in future environmental monitoring. Onsite gas and particle phase sampling in Beijing, China, and subsequent measurement of TFA concentrations indicated that the TFA concentration in the gas phase (1396 ± 225 pg m−3) was much higher than that in the particle phase (62 ± 8 pg m−3) and that monthly concentrations varied seasonally with temperature. Based on the field results and analysis, an adsorption experiment of TFA on soot was then conducted at three different temperatures (293, 303, and 313 K) to provide parameters for kinetic and thermodynamic modelling. The proportion of atmospheric TFA concentration in the gas phase increased with temperature, indicating that temperature affected the phase distribution of TFA. The subsequent kinetic and thermodynamic modelling showed that the adsorption of TFA by soot could be described well by the Bangham kinetic model. The adsorption was controlled by diffusion, and the key mechanism was physical adsorption. The adsorption behavior can be well described by the Langmuir isotherm model. The calculated thermodynamic parameters ΔG° (−2.34, −1.25, and −0.15 kJ mol−1 at 293, 303, and 313 K, respectively), ΔH° (−34.34 kJ mol−1), and ΔS° (−109.22 J mol−1. K−1) for TFA adsorption by soot were negative, indicating that adsorption was a spontaneous, exothermic process.
Stratabound massive sulfide deposits are widespread along the Middle-Lower Yangtze Metallogenic Belt (MLYMB) and serve as an important copper producer in China. Two contrasting genetic models have been proposed, interpreting the stratabound massive sulfide deposits as a Carboniferous SEDEX protore overprinted by Cretaceous magmatic-hydrothermal system or an Early Cretaceous carbonate replacement deposit. These two contrasting models have been applied to the Xinqiao stratabound Cu-Au sulfide deposit, which is dominated by massive sulfide ores hosted in marine carbonates of the Carboniferous Chuanshan and Huanglong Formations, with minor Cu-Au skarn ores localized in the contact zone between the Cretaceous diorite Jitou stock and the Carboniferous carbonate rocks. New SIMS zircon U-Pb dating suggests that the Jitou stock formed at 138.5 +/- 1.1 Ma (2 sigma, MSWD = 0.6). Pyrite Re-Os dating yields an imprecise date of 142 +/- 47 Ma (2 sigma, MSWD = 7.8). The geochronological data thus constrain the mineralization of the Xinqiao deposit at Early Cretaceous.Fluid inclusions in prograde skarn diopside have homogenization temperatures of 450-600 degrees C and calculated salinities of 13-58 wt.% NaCl equiv. Quartz from the stratabound ores and pyrite-quartz vein networks beneath the stratabound ores have homogenization temperatures of 290-360 and 200-300 degrees C, with calculated salinities of 5-12 and 2-10 wt.% NaCl equiv., respectively. Quartz from the skarn ores and veins beneath the stratabound ores have delta O-18 values of 12.32 +/- 0.55 (2 SD, n = 22) and 15.57 +/- 1.92 parts per thousand (2 SD, n = 60), respectively, corresponding to calculated delta O-18 values of 622 +/- 1.59 (2 sigma) and 6.81 +/- 2.76 parts per thousand (2 sigma) for the equilibrated ore-forming fluids. The fluid inclusion and oxygen isotope data thus support a magmatic-hydrothermal origin rather than a SEDEX system for the stratabound ores, with the hydrothermal fluids most likely being derived from the Jitou stock or associated concealed intrusion. Results from this study have broad implications for the genesis and exploration of other stratabound massive sulfide deposits along the MLYMB. (C) 2016 Elsevier B.V. All rights reserved.
The effect of calcium hydroxide (Ca(OH)(2)), a promising additive to control the pollutants released during sludge pyrolysis, on the pyrolysis behavior and kinetics of sewage sludge was investigated in detail in this study. The obtained thermograms of Ca(OH)(2)-blended sludge showed that the addition of Ca(OH)(2) influenced the thermogravimetric characteristics of sludge, especially in the temperature range of 340-700 degrees C where the decomposition of Ca(OH)(2) happens. An increasing addition of Ca(OH)(2) improved the pyrolysis conversion of sludge at temperatures of more than 600 degrees C, which was verified by the increase of the process heat flow. Importantly, the transformation of elements in sludge was promoted, resulting in a lesser content of impurities, which existed mostly in the thermally stable forms, in the remaining char. Kinetic analysis revealed that the pyrolysis behavior of sludge was influenced by the addition of Ca(OH)(2) and reaction temperature. At low temperatures, Ca(OH)(2) acted as the source of nuclei required for the establishment of reaction interface and then induced the secondary cracking of the pyrolytic compounds in the sludge matrix when the reaction came to high temperatures. A retrofitted kinetic model, overcoming the drawback faced by most Arrhenius-derived models that the integral of temperature-induced item was resolved by approximation, is developed and exhibits superiority in describing the reaction characteristics of sludge pyrolysis.
This paper presents the effect of NaCl on aerobic denitrification by a novel aerobic denitrifier strain Achromobacter sp. GAD-3. Results indicated that the aerobic denitrification process was inhibited by NaCl concentrations ae<yen>20 g L-1, leading to lower nitrate removal rates (1.67 +/- 4.0 mg L-1 h(-1)), higher nitrite accumulation (50.2 +/- 87.4 mg L-1), and increasing N2O emission ratios (13 +/- 72 mg L-1/mg L-1). Poor performance of aerobic denitrification at high salinity was attributed to the suppression of active microbial biomass and electron donating capacity of strain GAD-3. Further studies on the corresponding inhibition of the denitrifying gene expression by higher salinities revealed the significant sensitivity order of nosZ (for N2O reductase) > cnorB (for NO reductase) ae nirS (for cytochrome cd(1) nitrite reductase) > napA (for periplasmic nitrate reductase), accompanied with a time-lapse expression between nosZ and cnorB based on reverse transcription and real-time quantitative polymerase chain reaction (RT-qPCR) analysis. The insights into the effect of NaCl on aerobic denitrification are of great significance to upgrade wastewater treatment plants (WWTPs) containing varying levels of salinity.
Sulfamethoxazole (SMX), as a common sulfonamide antibiotic, was reported to affect conventional anaerobic denitrification. This study presented effects of SMX on aerobic denitrification by an aerobic denitrifier strain Pseudomonas stutzeri PCN-1. Results demonstrated serious inhibition of N2O reduction as SMX reached 4 mu g/L, leading to higher N2O emission ratio (251-fold). Increase of SMX (similar to 8 mu g/L) would induce highest nitrite accumulation (95.3 mg/L) without reduction, and severe inhibition of nitrate reduction resulted in lower nitrate removal rate (0.15 mg/L/h) as SMX reached 20 mu g/L. Furthermore, corresponding inhibition of SMX on denitrifying genes expression (nosZ > nirS > cnorB > napA) was found with a time-lapse expression between nosZ and cnorB. Meanwhile, the decline in electron transport activity and active microbial biomass of strain PCN-1 was revealed. The insight into mechanism of SMX influence on aerobic denitrifier is of particular significance to upgrade nitrogen removal process in antibiotics-containing wastewater treatment plant. (C) 2017 Elsevier Ltd. All rights reserved.
