Current air quality models usually underestimate the concentration of ambient air sulfate, but the cause of this underestimation remains unclear. One reason for the underestimation is that the sulfate formation mechanism in the models is incomplete, and does not adequately consider the impact of the synergistic effects of high concentrations of multiple pollutants on sulfate formation. In this work, the roles of gaseous NO2, NH3 and solution ionic strength in the formation of sulfate in the aqueous phase were quantitatively investigated using a glass reactor and a 30 m(3) smog chamber, separately. The results showed that sulfate formation was enhanced to different degrees in the presence of gas-phase NO2, NH3 and their coexistence as solutes in both liquid solution and aerosol water. NH3 enhances the aqueous oxidation of SO2 by NO2 mainly by accelerating the uptake of SO2 through increased solubility. More importantly, we found that high ionic strength in aerosol water could significantly accelerate the aqueous oxidation of SO2, resulting in unexpectedly high S(VI) formation rates. We estimate that under severe haze conditions, heterogeneous oxidation of SO2 by NO2 on aerosols may be much shorter than that through gas phase oxidation by OH, aided by high ionic strengths in aerosols. Considering the existence of complex air pollution conditions with high concentrations of NO2, NH3 and aerosol water, as expected in typical urban and suburban settings, the sulfate formation mechanisms revealed in the present work should be incorporated into air quality models to improve the prediction of sulfate concentrations. (C) 2019 Elsevier Ltd. All rights reserved.
Two-dimensional (2D) metal–semiconductor transition-metal dichalcogenide (TMDC) vertical heterostructures play a crucial role in device engineering and contact tuning fields, while their direct integration still challenging. Herein, a robust epitaxial growth method is designed to construct multiple lattice-matched 2D metal–semiconductor TMDC vertical stacks (VSe2/MX2, M: Mo, W; X: S, Se) by a two-step chemical vapor deposition method. Intriguingly, the metallic VSe2 preferred to nucleate and extend from the energy-favorable edge site of the semiconducting MX2 underlayer to form VSe2/MX2 vertical heterostructures. This growth behavior was also confirmed by density functional theory calculations of the initial adsorption of VSe2 adatoms. In particular, the formation of Schottky-diode or Ohmic contact-type band alignments was detected for the stacks between VSe2 and p-type WSe2 or n-type MoSe2, respectively. This work hereby provides insights into the direct integration, band-alignment engineering, and potential applications of such 2D metal–semiconductor stacks in next-generation electronics, optoelectronic devices, and energy-related fields.
Volatile organic compounds (VOCs) pollution, which is closely linked to photochemical smog and secondary organic aerosols, has become a severe concern in China. Therefore, we compiled a new high-resolution emission inventory for the industrial non-methane Volatile organic compounds (NMVOCs) using “bottom-up” approaches throughout 2010 and 2016. In this work, the industrial sources were divided into five major categories, and 108 specific sources, as well as an emission factor database, was developed for industrial NMVOCs. Results indicated that the total NMVOCs emissions from industrial sources increased from 16.88 Tg in 2010 to 21.04 Tg in 2016 at an annual average rate of 3.7%. The five major source categories including “production of VOCs”, “storage and transportation”, “industrial processes using VOCs as raw material”, “processes using VOCs-containing products”, and “fossil fuel combustion” generated 1.92 Tg, 0.94 Tg, 6.54 Tg, 10.04 Tg, and 1.60 Tg NMVOCs, respectively, in 2016. Coke production, plastic manufacturing, raw medicine industry, and architectural decoration were the primary sources of industrial NMVOCs and emissions of these sources increased by 140 Gg, 190 Gg, 640 Gg, and 700 Gg between 2010 and 2016. The emissions displayed distinct spatial characteristics, with significantly higher emissions in the Beijing-Tianjin-Hebei region, the Pearl River Delta, the Yangtze River Delta, and the Cheng-Yu region than in other areas. Shandong, Guangdong, Jiangsu, Zhejiang, and Henan were the top five provinces with the highest NMVOCs emissions, while the emission hotspots in the county-level were mainly distributed in Guangzhou urban area, Shanghai Pudong New Area, Hangzhou urban area, and Shenzhen urban area. The emissions in Henan province, Hubei province, and Cheng-Yu region increased significantly during the study period. Instead, emissions in some counties of Zhejiang province and Hebei province decreased than in 2010.
As the major producer and consumer of hydrofluorocarbons (HFCs), China is obligated to phase-down HFCs to mitigate global warming if China ratifies the Kigali Amendment (KA) to the Montreal Protocol. Based on historical HFCs consumption in each sector, here we estimated historical HFCs emissions with a bottom-up method, and projected the consumption baseline and schedule for HFCs phase-down in China under the KA and the corresponding potential for emission reduction. Results showed that China's HFCs consumption and emissions in 2017 were 164,000 t (311 Mt CO2-eq) and 108 Mt CO2-eq, respectively. HFCs consumption baseline was projected to be (724 ± 18) Mt CO2-eq in 2024, and China should take measures to phase-down HFCs by 2029, at the latest, to meet the requirements of the KA. HFCs consumption in 2050 under KA would reach the level of 2012–2013. Cumulative reduced consumption was estimated at 10.8 (10.1–11.6) Gt CO2-eq, and cumulative reduced emissions were estimated at 5.38 (4.90–5.64) Gt CO2-eq by 2050.
Thermal maturity is an important geochemical parameter for the study of source rocks in unconventional shale plays. Using well logs to estimate thermal maturity would overcome the discontinuity of core sample analysis and can provide continuous profiles. However, estimating thermal maturity from well logs, unlike total organic carbon (TOC) content has received less attention. In this paper, we used vitrinite reflectance (Ro) to characterize thermal maturity and proposed a practical method to produce a continuous profile of thermal maturity from well logs. For this purpose, a maturity indicator (Im) regarding with kerogen element compositions and types was defined. Im was calculated for different kerogen types based on their H/C versus O/C atomic ratios. It was found that Ro decreases with the Im of all three types of kerogen monotonically, which was used as a foundation for thermal maturity predictions. Then, the Im was related to the compensated neutron log (CNL) responses of kerogen by considering the variations in elemental compositions of organic matter with maturity. Based on known CNL response of major sedimentary minerals and pore fluids, a petrophysical equation was established to obtain Im from well logs. Finally, the proposed method was applied to Chang 7 Shale of Triassic Yanchang Formation of the Ordos Basin, China and the Bakken Shale of Williston Basin, North Dakota, USA, two major source rocks with different kerogen types and maturities. The results showed an acceptable agreement between lab measurements and predictions of Ro with a good correlation coefficient, verifying the new method is effective and reliable.
This paper examines two inscriptions used by Christian Marek (2003, pp. 66-67; 2015, pp. 308-309) to support his thesis that the coastal Paphlagonian koinon – known in epigraphical sources as “the Koinon of the Cities in Pontus” – was already established in the Julio-Claudian period, if not earlier.The first inscription from Pompeiopolis is reported by Fourcade (1811) that can date to the early Augustan period or earlier. Marek himself focused on the Pompeiopolis inscription in his rejoinder to Loriot’s thesis in a recent article (2015), arguing that Loriot is wrong to date this inscription to the imperial period. Alternatively, this paper proposes that a separate inscription invoked by Marek in his earlier work may be more effective.The second inscription dates to the reign of Claudius. It comes from a rupestral column-and-niche roadside monument in the outskirts of ancient Amastris. The monument concerns two cults, Theos Hypsistos and Divus Augustus. Theos Hypsistos received a dedication consisting of a column and a perched eagle, and the column base inscribed with a short dedicatory inscription. There are two other tabulae ansatae, possibly associated with the niched figure, recording the same title ὁ τοῦ ἐπουρανίου θεοῦ Σεβαστοῦ ἀρχιερεὺς, and the Latin equivalent of this priesthood was perpetuus sacerdos Divi Augusti. That ἐπουρανίου does not have a correlate term in the Latin title, along with the presence of a dedication to Theos Hypsistosimmediately next to the niche monument, suggests that this priesthood was in charge of a syncretistic imperial cult, and was different from the highpriesthood of the municipal imperial cult attested in a separate Amastrian inscription dated to the Neronian period.This paper argues that the syncretistic imperial cult dedicated to Divus Augustus and Theos Hypsistos may have been established as an extra-urban cult designed for an audience broader than the inhabitants of Amastris proper. The so-called Oath of Gangra makes it clear that part of the binding force of such an oath of loyalty was the invocation of local deities to enforce retribution. We are also informed by the same oath that such oaths of loyalty had to be administered in both the city proper and the chora “at the altars of Augustus in the sanctuaries of Augustus” as part of an annual and province-wide exercise. The two information points to the possibility that the the syncretistic cult from the extra-urban monument near Amastris may have been part of a complex that could be described as a sanctuary of Augustus, with a targe audience not from Amastris proper, but from the Amastris chora. The fact that the extra-urban monument was carved into the rockface beside a Roman road that was cut but Gaius Iulius Aquila, an equestrian and permanent holder of the highpriesthood overseeing this syncretistic cult, has further implications. Tacitus reported a campaign in 49 CE in the Bosporus, in which one Iulius Aquila successfully led a coalition force against the uprising of Mithridates (Tac. Ann. 12.15-21). If this military commander was indeed Gaius Iulius Aquila the highpriest, the extra-urban monument may have further political significance that resembles the Ara Romae et Augusti ad confluentes Araris et Rhodani, which was built and maintained by a priesthood created by a local elite following the successful suppression of the Sugambri and their allies by Drusus (Dio Cass. 54.32.1), and served as the gathering place for the concilium of the Tres Galliae. Fishwick argues that Drusus created a federal concilium by inviting the leading men of the Gallic provinces to participate in its management and organization, so that leading men could have the opportunity to discuss mutual concerns and put for complaints against Roman authorities (Fishwick 2002, pp. 12-13).
We studied temperature-dependent amplified spontaneous emission (ASE) in CsPbBr3 perovskite thin films. For temperatures 180-360 K, a narrow-band lasing is observed. However, a new accompanying ASE band appears below 180 K, indicating a more complicated behavior. The two ASE bands are strongly correlated and in competition; they are assigned as exciton and bi-exciton recombination. We estimated the exciton binding energy (E-B = 27.3 meV) and that of the bi-exciton, which is lower than the E-B. The reduced effective mass of the exciton is estimated as mu = 0.11 m(c). This discovery identifies more details of the ASE phenomenon. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
