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In this paper, we utilize the Advanced Research version of the Weather Research and Forecasting model (ARWv4) to explore how the fog is affected by the basin's topography during a radiation fog event in the Sichuan Basin in December 2016 by setting up three sets of terrain tests. The simulation results demonstrate that the fog area in the expanded basin terrain emerges 40 min earlier than in the original topography control test (CTL), with the fog area extent marginally reduced. Conversely, the fog area in the reduced basin terrain emerges one hour earlier than in the CTL, with the fog area extent increased by 133.5%. Basin topography is an essential factor influencing the humidity, temperature, and dynamical fields. The expansion of basin topography was shown to be unfavorable for water vapor convergence. Moreover, the area exhibiting relative humidity levels exceeding 95% at the peak of the fog intensity was smaller than that observed in CTL. The impact of radiative cooling was diminished, and the thickness and intensity of the inversion layer were reduced compared to CTL. In addition, the wind speed in the marginal area exceeded 5 m s−1, and the fog formation was observed only in the central portion of the basin, where wind speeds ranged from 0 to 3 m s−1. In contrast, the change in the topography of the narrowed basin resulted in the opposite phenomenon overall. This work emphasizes the importance of basin topography in forming and developing the fog in the Sichuan Basin. [ABSTRACT FROM AUTHOR]

A collection of bronze chariot-horses was discovered in the Yang'an Han tomb in Qionglai City, Sichuan Province. These bronzes was used as burial objects, symbolizing the high status of the tomb owner during his lifetime. To analyze the samples taken from the bronze chariot-horses, various scientific techniques were employed, including metallographic microscopy, scanning electron microscope energy dispersive (SEM–EDS), multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS), and inductively coupled plasma-atomic emission spectrometer (ICP-AES) were used to analyze samples from the bronze chariot-horses. Unlike most Han bronzes made of leaded tin-bronze, the bronze chariot-horses were crafted using copper and tin, and their metallographic structure revealed that they were cast. The origin of the copper material used for the bronze chariot-horses differed noticeably from that of bronzes excavated in the Sichuan area from the late Warring States period and Western Han period. Historical documents and archaeological findings suggested that the owners of the bronze chariot-horses were possibly vassals. As the Sichuan region was governed by the central government of the Western Han Dynasty through the establishment of prefectures and counties rather than through the enfeoffment system, the presence of the bronze chariot-horses in Yang'an Han tomb may be related to the family of Liu Yue (刘越). The analysis of the lead isotope data indicated that the copper material likely originated from the southeastern Hebei and western Shandong, providing strong evidence for the link between the bronze chariot-horses and the family of Liu yue in terms of resource circulation. [ABSTRACT FROM AUTHOR]

• The dominant pollutant changed from SO 4 2− to NO 3 − in most seasons of Chengdu. • SO 4 2− was likely generated more easily in urban areas due to Mn-catalytic heterogeneous reactions. • OC concentrations were higher in urban areas than in suburban areas, other than EC. • The contribution of combustion origins and secondary aerosols increased from CP to PP. Nowadays, the fine particle pollution is still severe in some megacities of China, especially in the Sichuan Basin, southwestern China. In order to understand the causes, sources, and impacts of fine particles, we collected PM 2.5 samples and analyzed their chemical composition in typical months from July 2018 to May 2019 at an urban and a suburban (background) site of Chengdu, a megacity in this region. The daily average concentrations of PM 2.5 ranged from 5.6-102.3 µg/m3 and 4.3-110.4 µg/m3 at each site. Secondary inorganics and organic matters were the major components in PM 2.5 at both sites. The proportion of nitrate in PM 2.5 has exceeded sulfate and become the primary inorganic component. SO 2 was easier to transform into sulfate in urban areas because of Mn-catalytic heterogeneous reactions. In contrast, NO 2 was easily converted in suburbs with high aerosol water content. Furthermore, organic carbon in urban was much greater than that in rural, other than elemental carbon. Element Cr and As were the key cancer risk drivers. The main sources of PM 2.5 in urban and suburban areas were all secondary aerosols (42.9%, 32.1%), combustion (16.0%, 25.2%) and vehicle emission (15.2%, 19.2%). From clean period to pollution period, the contributions from combustion and secondary aerosols increased markedly. In addition to tightening vehicle controls, urban areas need to restrict emissions from steel smelters, and suburbs need to minimize coal and biomass combustion in autumn and winter. Graphical Abstract [Display omitted] [ABSTRACT FROM AUTHOR]

The rapid and accurate extraction of wide-area coseismic landslide locations is critical in earthquake emergencies. At present, the extraction of coseismic landslides is mainly based on post-earthquake site investigation or the interpretation of human–computer interactions based on remote sensing images. However, the identification efficiency is low, which seriously delays the earthquake emergency response. On the basis of the available multisource and multiscale remote sensing data, numerous studies have been carried out on the methods of coseismic landslide extraction, such as pixel analysis, object-oriented analysis, change detection, and machine learning. However, the effectiveness of coseismic landslide extraction was low in wide areas with complex topographic and geomorphic backgrounds. Therefore, this paper offers a comprehensive study of the factors influencing coseismic landslides and researches rapid and accurate wide-area coseismic landslide extraction methods with multisource remote sensing and geoscience technology. These techniques include digital elevation modeling (DEM) and its derived slopes and aspects. An embedded multichannel spectral–topographic feature fusion model for coseismic landslide extraction based on DeepLab V3+ is proposed, and a knowledge-enhanced deep learning information extraction method integrating geological knowledge is formed. Using the Jiuzhaigou Ms7.0 earthquake (seismic intensity VIII) in Sichuan Province, China, a comparison of landslide extraction models and strategies is carried out. The results show that the model proposed in this paper achieves the best balance in the accuracy and efficiency of wide-area extractions. Using multiple feature data of coseismic landslides, the problem of mixed pixels is solved. The rate of the misidentification of landslides as clouds, snow, buildings, and roads is significantly lower than in other methods. The identified landslide boundaries are smoother and more accurate, and the connectivity is better. Compared with other methods, ours can more accurately eliminate landslides not triggered by the Jiuzhaigou earthquake. While using the image block strategy to ensure extraction efficiency, it also improves the extraction accuracy of wide-area coseismic landslides in complex backgrounds. [ABSTRACT FROM AUTHOR]

PM 2.5 remains one of the critical pollutants involving regional and complex air pollution in many big cities of China, and its improvement has become sluggish in recent years. In this study, we collected PM 2.5 samples from two cities, Chengdu and Ya'an, which have different industrial structures in the Sichuan basin during wintertime and investigated the reasons behind their severe PM 2.5 pollution. Throughout the entire sampling period, the average PM 2.5 concentrations in Chengdu (71.3 ± 24.8 μg/m3) and Ya'an (72.6 ± 27.1 μg/m3) were similar. However, the chemical compositions of PM 2.5 showed significant differences. Chengdu exhibited higher concentrations of water-soluble inorganic ions, whereas Ya'an had higher levels of carbonaceous compounds. Both cities experienced an ammonium-rich environment, which promoted the homogeneous generation of secondary pollutants. Moreover, as PM 2.5 pollution worsened, the influence of heterogeneous reactions involving SO 2 and NOx, as well as the heterogeneous hydrolysis of N 2 O 5 , gradually became more pronounced in particle formation. Additionally, adverse meteorological conditions facilitated pollutant accumulation in Ya'an. Using the Positive Matrix Factorization model, we identified 5 sources of PM 2.5. The primary source of PM 2.5 in both cities was secondary formation (35.4% in Chengdu and 32.5% in Ya'an), while their second-largest contributors varied (26.2% from vehicle emission in Chengdu, and 26.6% from combustion source in Ya'an). These discrepancies highlight the necessity for tailored government interventions, particularly during the winter season. By analyzing the light absorption of the carbonaceous at 370 nm, we discovered that brown carbon was the primary absorber of near-ultraviolet light, with vehicle emissions accounting for the largest portion in Chengdu (37.2%) and combustion emissions being the predominant factor in Ya'an (51.0%). These results could potentially help for having a long-term impact on climate change by simultaneously reducing PM 2.5 pollution. [Display omitted] • Unfavorable weather conditions resulted in the accumulation of pollutants in Ya'an. • Secondary pollutant formation in the study areas was primarily driven by heterogeneous reactions. • The absorption of BrC at 370 nm was significantly influenced by vehicle emissions and combustion. [ABSTRACT FROM AUTHOR]

The Lower Cambrian Qiongzhusi Formation contains more than 200 m of marine sediments mainly consisting of mudstone and black shales, which are widely accepted as the most important hydrocarbon source rocks of the Ediacaran–Cambrian giant gas field in the Sichuan Basin. The geochemical compositions of biomarkers and trace elements obtained from black shales at the bottom of the Qiongzhusi Formation were used to reconstruct the palaeoproductivity and palaeoenvironment and to determine the main factors controlling the deposition and preservation of this organic‐rich shales. Based on varieties of steroids and hopanoids compositions, multifarious palaeobios such as pelagophyceae, dinoflagellate, diatom (or its ancestor), sponges, and aerobic/anaerobic bacteria have been proved to evolve in the Early Cambrian in the Sichuan Basin. In addition, a relative high concentration of Cubio compared with modern oceanic palaeoproductivity proxies indicate a moderate to relatively high palaeoproductivity, which is favourable for the organic matter accumulation of this source rocks. Moreover, the evidence from biomarkers and trace element ratios suggest that the Lower Cambrian sediments were deposited under a non‐sulphurized anoxic condition, which provided a favourable preservation condition. The covariation among Porg, Cubio, and TOC shows that the palaeoproductivity is the main controlling factor for the high organic content of the black shales of the Qiongzhusi Formation. [ABSTRACT FROM AUTHOR]

Carbonaceous aerosols pose significant climatic impact, however, their sources and respective contribution to light absorption vary and remain poorly understood. In this work, filter-based PM 2.5 samples were collected in winter of 2021 at three urban sites in Yibin, a fast-growing city in the south of Sichuan Basin, China. The composition characteristics of PM 2.5 , light absorption and source of carbonaceous aerosol were analyzed. The city-wide average concentration of PM 2.5 was 87.4 ± 31.0 μg/m3 in winter. Carbonaceous aerosol was the most abundant species, accounting for 42.5% of the total PM 2.5. Source apportionment results showed that vehicular emission was the main source of PM 2.5 during winter, contributing 34.6% to PM 2.5. The light absorption of black carbon (BC) and brown carbon (BrC) were derived from a simplified two-component model. We apportioned the light absorption of carbonaceous aerosols to BC and BrC using the Least Squares Linear Regression with optimal angstrom absorption exponent of BC (AAE BC). The average absorption of BC and BrC at 405 nm were 51.6 ± 21.5 Mm−1 and 17.7 ± 8.0 Mm−1, respectively, with mean AAE BC = 0.82 ± 0.02. The contribution of BrC to the absorption of carbonaceous reached 26.1% at 405 nm. Based on the PM 2.5 source apportionment and the mass absorption cross-section (MAC) value of BrC at 405 nm, vehicle emission was found to be the dominant source of BrC in winter, contributing up to 56.4%. Therefore, vehicle emissions mitigation should be the primary and an effective way to improve atmospheric visibility in this fast-developing city. [Display omitted] • Carbonaceous aerosol was the dominate species of PM 2.5 during winter in Yibin city. • An improved AAE-based method was applied to evaluate aerosol light absorption. • The contribution of BrC to carbonaceous aerosol absorption at 405 nm was 26%. • Vehicle emission became the dominant source of BrC in this fast-growing city. [ABSTRACT FROM AUTHOR]

A significant negative organic carbon isotope (δ13C org) excursion occurred in the lower member of the lower Cambrian Qiongzhusi organic-rich shales in the Sichuan Basin, which is also reported in other contemporaneous strata throughout the Yangtze Platform. In this study, 47 lower Cambrian drill core samples were collected to investigate the possible formation mechanism of this negative δ13C org excursion using multiple geochemical approaches. Primary paleoproductivity, redox conditions and organic carbon isotopic compositions were determined for these core samples of the Qiongzhusi Formation in the Sichuan Basin. The results suggest that the degree of microbially mediated carbon cycling and its contribution to the total sedimentary organic matter has an important influence on organic carbon isotopic compositions. An extensive transgression during the deposition of the lower member of the Qiongzhusi Formation brought abundant nutrients to primary producers and thus stimulated blooms, which is evidenced by the high primary productivity in the lower member of the Qiongzhusi Formation. In addition, marine transgression also provided sulfide to the seawater. Enhanced primary productivity accelerated the consumption of bottom water oxygen and thus promoted the establishment of euxinic bottom water conditions. The euxinic conditions promoted an anaerobic carbon cycle mediated by sulfate-reducing bacteria and chemoautotrophic bacteria, which resulted in the dissolved inorganic carbon reservoir becoming more depleted in 13C. Once these 13C-depleted carbons are utilized by primary producers, the 13C-depleted carbons will participate in the carbon cycle. This series of processes ultimately resulted in lower δ13C org values within the lower Cambrian Qiongzhusi organic-rich black shales. A shift to positive and rather stable δ13C org values in the relatively organic-poor sediments indicates a smaller contribution of 13C-depleted bacterial biomass (e.g., sulfate-reducing bacteria and chemoautotrophic bacteria), which is evidenced by more oxygenated ocean bottom conditions in the study area. • δ13Corg records of the lower Cambrian black shales deposited in an intraplatform basin have been supplemented. • Enhanced primary productivity promoted the establishment of euxinic bottom water conditions. • The DIC pool may be replenished by 13C-depleted carbon due to anaerobic carbon cycling. • The contribution of 13C-depleted bacterial biomass resulted in the negative δ13C org excursion. [ABSTRACT FROM AUTHOR]

The lower Cambrian sediments including the Qiongzhusi and Maidiping formations in the Sichuan Basin are generally considered as the main source rocks of Precambrian-Cambrian petroleum system. A comprehensive study integrated with multiple geochemical methods was conducted on 119 lower Cambrian drillcore samples collected from the upper Yangtze Platform. The results show that the fluctuation of sea level and climate during the deposition of the Qiongzhusi and Maidiping formations act as the critical factors controlling the watermass conditions and thus OM accumulation. During the deposition of upper Maidiping Formation (Є 1 m), the paleoclimate was arid and sea level was relatively low in the study area. The depositional environment indexes (U EF -Mo EF , gammacerane index, β-carotane and V EF) suggested that the upper Є 1 m was deposited in a strong restricted marine setting with high water salinity and anoxic water conditions in Ziyang-Weiyuan area. However, during the early Qiongzhusi Formation period, the paleoclimate became humid and sea level rose in the study area. High paleoproductiviy caused by high concentrations of nutrients brought by seawater and freshwater plays an important role in OM accumulation in the basal part of the Qiongzhusi Formation (Є 1 q). Furthermore, the model of paleoproductivity promotion caused by the coordinated control of climate and extensive transgression in the lower part of Є 1 q may also be applicable to interpret the origin of high organic carbon abundance in the strata deposited in the same period with the Є 1 q (such as Shiyantou, Shuijingtuo and Niutitang formations) in other parts of the upper Yangtze Platform. • Different organic matter enrichment models of lower Cambrian shales were established. • The lower Cambrian stratigraphic correlation profiles were established in study area. • Variations of watermass condition and productivity were driven by sea-level changes. [ABSTRACT FROM AUTHOR]

Dibenzofuran and its methyl substituted homologues are the important oxygen-containing polycyclic aromatic compounds in crude oils. The ratio of 1-/4-methyldibenzofuran has been successfully used in sandstone reservoir tracing oil migration orientation. Here we focus on the geo-chromatographic fractionation effect of methyldibenzofuran (MDBF) in dolomite reservoirs. We calculated the charge density differences between 1-methyldibenzofuran (1-MDBF) and 4-methyldibenzofuran (4-MDBF) based on density functional theory. The E I n between MDBF isomers and dolomite (104) surface was also calculated according to molecular dynamics simulation. The result show that comparing with the 4-MDBF, there is strong interaction between 1-MDBF and dolomite (104) surface leading the ratio of 1-MDBF and 4-MDBF increase with the migration distance. There is no significant correlation between bitumen reflectance and the ratio of 1-MDBF and 4-MDBF in our samples. In addition, molecular simulation results show that the MDBF isomers are thermodynamically stable and dissociation of Ph-CH 3 is difficult to occur under geological condition. All these demonstrate that 1-MDBF and 4-MDBF can be survived after oil-cracking to gas and pyrobitumen. Therefore, in theory, the ratio of 1-/4-methyldibenzofuran is also regarded as an index for oil migration orientation in dolomite reservoir. Gas chromatography-mass spectrometry results show that MDBFs occur at relatively higher abundance in the bitumens of the Ediacaran Dengying Formation (Z 2 dn 4) and Cambrian Longwangmiao Formation (Є 1 l) in the Sichuan Basin. The ratio of 1-/4-methyldibenzofuran has been successfully used to trace the crude oil filling pathway in the Z 2 dn 4 and Є 1 l dolomite reservoir in the Sichuan Basin in this study. Two preferential filling orientations (i.e. from west to east and from north to south) for paleo-oil have been identified in the contour maps of 1-/4-methyldibenzofuran in the Z 2 dn 4 and Є 1 l , which is consistent with the geological background. • The geochromatography of methyldibenzofuran was simulated by molecular dynamics. • Methyldibenzofuran isomers ratios were successfully applied in dolomite reservoirs. • The relationship between methyldibenzofuran and R b are discussed. [ABSTRACT FROM AUTHOR]

Abstract: Background: To compare the prevalence of syringe-sharing behaviors and other HIV-related characteristics among female injecting drug users (IDU) engaging and not engaging in sex work and to identify factors associated with such risk behaviors in the two groups. Methods: Data were obtained from 1923 female respondents of behavioral surveillance studies conducted in Sichuan, China. Results: The prevalence of having at least one of the three syringe-sharing behaviors (borrowing, lending, or injecting from pre-filled syringes) was 45.3% in the female sex workers (FSW) group and 37.2% in the non-FSW group (adjusted OR=1.28, p <0.05). Compared with non-FSW, FSW were more likely to have injected drugs for 3 or more years, have non-regular sex partners, believe that condom use could prevent HIV, and have received free condoms/lubricants (OR=1.34–5.08, p <0.05); FSW were less likely to be older, better educated, and have attempted quitting drugs (OR=0.31–0.68, p <0.05). Being FSW, older, longer injecting drug use, higher drug injection frequency, and having regular sex partner were associated with injecting with others’ used syringes (multivariate OR=1.26–1.92, p <0.05) while the reverse was true for education level and voluntary HIV antibody testing (multivariate OR=0.44–0.64, p <0.05). Of all sampled FSW, 39.3% did not use a condom in the last episode of sex work. Conclusions: Female IDU involving in sex work are at high risk of HIV transmission and the risk may even be higher than their non-FSW counterparts. The bridging effect poses a threat to the HIV epidemic in China and effective preventive services are warranted. [Copyright &y& Elsevier]