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High‐resolution seismic model is crucial for advancing our understandings on geological processes and enhancing seismic hazard mitigation programs. We construct a high‐resolution China Seismological Reference Model (CSRM‐1.0) in the top 100 km of the crust and uppermost mantle in continental China following a top‐down construction process. The employed seismic constraints include P‐wave polarization angle from tele‐seismic event, short‐period Rayleigh wave ellipticity from ambient noise, long‐period Rayleigh wave ellipticity from earthquake data, receiver function, empirical Green's function from ambient noise, Rayleigh wave phase/group velocity dispersion curves from regional earthquakes, and Pn‐wave travel time extracted from seismic data of 4,435 stations. CSRM‐1.0 has a spatial crustal resolution of ∼60 km beneath the north‐south seismic belt and trans‐North China orogen regions and ∼120 km beneath the rest of continental China, and a spatial mantle resolution of ∼300 km. CSRM‐1.0 exhibits prominent velocity heterogeneities in the crust and uppermost mantle and an eastward thinning of the crust, geographically correlating with geological settings. CSRM‐1.0 improvements include accurate estimation of shallow seismic structure, increased spatial resolution and improved model accuracy. Crustal composition inferred from CSRM‐1.0 exhibits a general transition from a felsic upper crust to a mafic lower crust. Mafic rocks in the lower crust are found predominantly along inter‐block boundaries and sporadically within the interiors of blocks, likely resulted from preferential inter‐block intrusions of magmas related to various oceanic plate subductions and the Emeishan mantle plume. This study contributes seismic constraints and CSRM‐1.0 to the CSRM product center (http://chinageorefmodel.org) as a backbone open‐access geophysical cyberinfrastructure. Plain Language Summary: High‐resolution seismic imaging of the crust and uppermost mantle offers crucial insights into regional geological histories and enhances seismic and volcanic hazard mitigation programs. We construct a high‐resolution China Seismological Reference Model (CSRM‐1.0) of the crust and mantle beneath continental China with various types of seismic constraints extracted from seismic data recorded by 4,435 stations deployed across continental China since 1990. CSRM‐1.0 has a spatial resolution of ∼60–120 km in the crust and 300 km in the uppermost mantle. CSRM‐1.0 improvements include accurate estimation of shallow seismic structure, increased spatial resolution and improved model accuracy. Crustal composition inferred from CSRM‐1.0 exhibits a general transition from a felsic upper crust to a mafic lower crust. Mafic rocks in the lower crust are found predominantly along inter‐block boundaries and sporadically within the interiors of blocks, likely resulted from preferential inter‐block intrusions of magmas related to various oceanic plate subductions and the Emeishan mantle plume. This study contributes seismic constraints and CSRM‐1.0 to the CSRM product center (http://chinageorefmodel.org) as a backbone open‐access geophysical cyberinfrastructure. Key Points: CSRM‐1.0 is constructed with various seismic constraints from data of 4,435 stations using a self‐consistent top‐down construction processCSRM‐1.0 improvements include accurate estimation of shallow seismic structure, increased spatial resolution, and enhanced model accuracyCSRM‐1.0 reveals major crustal mafic rocks related to the past subductions, an Emeishan mantle plume and geological inter‐block boundaries [ABSTRACT FROM AUTHOR]

Although ambient noise interferometry has been extensively utilized for seismic velocity tomography, its application in retrieving attenuation remains limited. This study presents a comprehensive workflow for extracting Rayleigh wave amplitude and attenuation from ambient noise, which consists of three phases: (1) retrieval of empirical Green's functions (EGFs), (2) selection and correction of amplitude measurements and (3) inversion of attenuation, site amplification and noise intensity terms. Throughout these processes, an 'asynchronous' temporal flattening method is used to generate high-quality EGFs while preserving relative amplitudes between stations. Additionally, a novel 't-symmetry' criterion is proposed for data selection along with the signal-to-noise ratio. Furthermore, 2-D sensitivity kernels are utilized to estimate the focusing/defocusing effect, which is then corrected in amplitude measurements. These procedures are designed to deliver reliable attenuation measurements while maintaining flexibility and automation. To validate the effectiveness of the proposed noise-based attenuation tomography approach, we apply it to a linear array, NCISP-6, located in NE China. The obtained results correlate reasonably well with known geological structures. Specifically, at short periods, high attenuation anomalies delineate the location of major sedimentary basins and faults; while at longer periods, a notable rapid increase of attenuation is observed beneath the Moho discontinuity. Given that attenuation measurements are more sensitive to porosity, defect concentration, temperature, melt and volatile ratio than seismic velocities, noise-based attenuation tomography provides important additional constraints for exploring the crustal and upper mantle structures. [ABSTRACT FROM AUTHOR]

To obtain the deformation of the solid Earth from a global navigation satellite system (GNSS)-observed velocity field, the loading effect of the surface mass variations should be effectively deducted. However, the GNSS-observed velocity field in mainland China is currently limited only to the loading correction calculated using Gravity Recovery and Climate Experiment (GRACE) spherical harmonic coefficients, which is equivalent to the approximately 300-km smoothed result in the spatial domain; thus, the derived tectonic deformation is inaccurate. Therefore, it is important to study and identify a reasonable method for calculating the loading effect of the surface mass change model and to carry out an effective loading correction of the GNSS velocity field. In this study, the performances of two calculation methods, namely the GRACE spherical harmonic coefficient and Green's function, were analyzed and compared. In addition, we constructed a comprehensive model of the global surface mass variations, calculated the vertical load velocity in mainland China using Green's function method and compared the results with those for the GRACE spherical harmonic products. We found that the difference between the results of the GRACE spherical harmonic coefficient and Green's function methods was more than 1 mm/yr in the North China Plain, implying that the GRACE spherical harmonic coefficient method cannot be used for loading correction of the observed GNSS vertical velocity field. In contrast, the loading effect calculated using Green's function method can be more effectively applied for loading correction of the GNSS vertical velocity field in mainland China. The GNSS-observed velocity exhibited a clear uplift in the North China Plain and the west glacier areas; however, the GNSS velocity fields were significantly reduced after the loading correction, indicating that the observed GNSS vertical velocity fields were mainly caused by the surface mass loading due to the negative correlation between the vertical load velocity and the surface mass changes. Moreover, we found that the loading correction accounted for more than 50 per cent of the GNSS vertical velocity field in most of the glaciated regions in eastern and western China, and the maximum value exceeded 300 per cent, indicating that the loading effect was large. Finally, we obtained the GNSS vertical velocity field for mainland China with a loading correction. Additionally, the spectral characteristics of the time-varying gravity field in mainland China were investigated. The results showed that clear annual, semi-annual and 10-year medium- and long-period signals exist. [ABSTRACT FROM AUTHOR]

Non-structural carbohydrates (NSC) as resource reserves of plants play important roles in energy supply for normal growth and reproduction under environmental stress. The yield of perennial crops is mainly determined by the carbohydrate production and allocation in the current growth season, as well as the re-allocation of NSC reserves. However, the contribution of NSC to crop yield has not been fully determined. Fengdan (Paeonia ostii) is a variety of oil Peony that is newly developed in China. The effects of tree age and NSC on yield were examined by investigated the variations of biomass, soluble sugars, starch, and NSC in the organ and whole tree levels in the dormant and ripening stages of Fengdan populations with 4-, 6-, and 8-year-old in 2020 and 5-, 7-, and 9-year old in 2021. Results showed that the biomass, yield (seed biomass), soluble sugars, starch, and NSC reserve of Fengdan at the whole tree level increased with the increase in age. Although consistent correlations were observed between soluble sugars, starch and NSC storage, and yield among the plants with different ages, Fengdan showed allometric growth relationships between the accumulation of soluble sugars, starch, and NSC and yield and biomass (standardized major axis analyses slope b ≠ 1). Tree age significantly affected biomass and its allocation and NSC levels, especially the yield of Fengdan plants. The results of the investigation of the variations in the relationships between the yield and seasonal fluctuations of NSC and biomass indicate that roots is the key storage structure, whereas stems both serve as sink and/or source functions for the adult (7-9a) plants. NSC level, particularly the concentration of soluble sugars, in stems mainly influences Fengdan yield. These findings together provide new insights into the mechanisms underlying the yield formation of Fengdan and have implications for manipulating sink-source relationship to achieve high yield. [ABSTRACT FROM AUTHOR]

The surface displacements measured by the Global Navigation Satellite System (GNSS) provide a unique insight for studying terrestrial water storage (TWS) changes. In this study, we recovered the TWS changes from GNSS vertical displacements in Southwest China (SWC) using Slepian basis function (SBF) from January 2011 to December 2020. The performance of the TWS changes estimated by SBF was validated against the Gravity Recovery and Climate Experiment (GRACE)/GRACE Follow‐On (GFO) and the GNSS‐inverted TWS changes estimated by Green's function method. The results showed that the spatial patterns, seasonal, and linear trends of the TWS changes derived from GNSS using SBF agreed with the GRACE/GFO estimates. However, there are still evident differences in the local scope, and the GNSS‐derived TWS changes presented stronger amplitudes and more details in the spatio‐temporal domains than the GRACE/GFO estimates in SWC. The unconstrained GNSS inversion results using SBF also presented stronger signal amplitudes than those estimates with Green's function, and the TWS changes estimated by SBF were more reliable than Green's function method for regions with sparsely distributed GNSS stations in SWC. Additionally, the average distance between the GNSS stations can be considered as a reasonable filtering radius of SBF, and the SBF‐estimated TWS changes with different Gaussian filtering radii had comparable signal amplitudes and spatial patterns with the estimates of Green's function and GRACE/GFO. Key Points: Global Navigation Satellite System (GNSS)‐inverted terrestrial water storage (TWS) changes using Slepian basis function (SBF) present stronger amplitudes than Gravity Recovery and Climate Experiment (GRACE)/GRACE Follow‐On (GFO) estimates in Southwest ChinaSBF‐estimated TWS changes with Gaussian filtering show similar amplitudes and patterns as the estimates of Green's function and GRACE/GFOThe average distance of GNSS stations can be used as the optimal filtering radius of the SBF‐estimated TWS changes [ABSTRACT FROM AUTHOR]

Landslides present a significant hazard for humans, but continuous landslide monitoring is not yet possible due to their unpredictability. In recent years, numerical simulation and seismic inversion methods have been used to provide valuable data for understanding the entire process of landslide movement. However, each method has shortcomings. Dynamic inversion based on long-period seismic signals gives the force–time history of a landslide using an empirical Green's function but lacks detailed flowing characteristics for the hazards. Numerical simulation can simulate the entire movement process, but results are strongly influenced by the choice of modeling parameters. Therefore, developing a method for combining those two techniques has become a focus for research in recent years. In this study, we develop such a protocol based on analysis of the 2018 Baige landslide in China. Seismic signal inversion results are used to constrain and optimize the numerical simulation. We apply the procedure to the Baige event and, combined with a field geological survey, show it provides a comprehensive and accurate method for dynamic process reconstruction. We found that the Baige landslide was triggered by detachment of the weathered layer, with severe top fault segmentation. The landslide process comprised four stages: initiation, main slip, blocking, and deposition. Multi-method mutual verification effectively reduces the inherent drawbacks of each method, and multi-method joint analysis improves the rationality and reliability of the results. The approach outlined in this study could help us to better understand the landslide dynamic process. [ABSTRACT FROM AUTHOR]

Ground motions near the source area of the mainshock of the 2013 Lushan earthquake (Mw 6.6) in Sichuan Province in China were reproduced using the characterized source model and the empirical Green's function method (EGFM). The best-fit characterized source model consisted of one strong motion generation area (SMGA) and a background area. The synthesized ground motions of the characterized source model were in fairly good agreement with the observed ground motions in the frequency range from 0.5 to 30.0 Hz at ten strong motion stations. For the 2013 Lushan earthquake (Mw 6.6), both the relationships between the SMGA and the seismic moment, and those between the flat amplitude of the acceleration source spectrum in the short period and the seismic moment almost followed the empirical scaling relationships of inner fault parameters developed for crustal earthquakes. The reasons for the largest peak ground acceleration (PGA) (> 1 g) in the strong-motion observation history of China recorded at the 51BXD strong motion station were investigated from the source and site effects. We found that the directivity effect did not contribute to the largest record by comparing the effect of different positions of the rupture starting point on the synthesized ground motions. The nonlinear effect of shallow layers was negligible, as indicated by the similarity of the earthquake H/V spectral ratios between the mainshock and EGF events. A large shear-wave velocity contrast might not exist in the shallow layers as the station was situated on the slope of a small rock hill. Finally, we agreed with previous studies that the hanging-wall effect and topographic effect might be the reasons for generating the largest record at Station 51BXD. [ABSTRACT FROM AUTHOR]

Skywave refers to the electromagnetic wave reflected or refracted from the ionosphere and propagated in the form of a guided wave between the ionosphere and the Earth's surface. Since the skywave can propagate over large distances, it has been widely used in long-distance communication. This paper explores and demonstrates the feasibility of skywave for deep resource and energy exploration at depths of up to 10 km. Theoretical and technical advancements were accomplished in furthering skywave applications. A new solution method based on Green's function has been developed to study skywave propagation in a fully coupled lithosphere-air-ionosphere full space model. For the first time, the model allows one to study skywave distribution characteristics in the lithosphere containing inhomogeneity such as ore deposits or oil and gas reservoirs. This model also lays a foundation for skywave data processing and interpretation. On a parallel line, we have developed a multi-channel, broadband, low-noise, portable data acquisition system suitable for receiving skywave signals. Using the skywave field excited by a high-power fixed source located in central China, actual field surveys have been carried out in some areas in China including the Biyang depression of Henan Province. The initial results appear encouraging—the interpreted resistivity models prove to be consistent with those of seismic exploration and known geological information, and the exploration cost is only ∼1/4 to 1/10 that of seismic surveys. These initial successful applications of the skywave theory lay a solid foundation for further verification of the new method. [ABSTRACT FROM AUTHOR]

Due to the limitation of seismic station coverage or the network transport interrupted when the earthquake occurred, an accurate seismic shakemap may not be released to the public quickly. When the near-source observed waveforms for the intensity prediction technology used are incomplete, we synthesize the seismic waveform into observation waveforms. An accurate seismic rupture process is necessary to synthesize virtual station observations. So, we should release the rupture process as soon as possible after a large earthquake. Most large earthquakes occur at the junction of two or three tectonic terranes. With violent tectonic movements, fault basins and uplift zones are distributed on the edge of the plateau. With complex structural conditions, the 1D layered half-space velocity structure model could not meet the requirement of earthquake rupture process inversion. It takes much time to calculate 3D Green's function with a 3D velocity model for the complete waveform inversion of the earthquake rupture process. To rapidly invert the rupture process as accurately as possible, according to the geological conditions of the station, we calculated several Green's function libraries in advance. We extracted Green's functions from these libraries for each site based on the sites' coordinates once an earthquake occurs. The time we spend in extracting Green's functions from several Green libraries equals that we spend in extracting Green's functions from one single library. The applicability of this method was tested in the 2017 Jiuzhaigou M6.5 earthquake with complex structural conditions in the mountain uplift zone. With our model, the time we spent in calculating the rupture process was almost the same as that we spent with the 1D velocity structure model, which was far less than that we could have spent in calculating 3D Green's function. The degree of fitting between the synthetic data and the observation data of our model was much higher than the fitting of the 1D velocity model, which means that the earthquake rupture process we determined was more reliable. [ABSTRACT FROM AUTHOR]

Non-tidal variation on sea level generates immediate changes in gravity field and deformation of the Earth's crust, thus influencing the stability of geodetic datums. To achieve higher accuracy of geodetic datums in coastal and island areas, sea-level changes should be adequately considered when conducting the maintenance of datums. Based on the data of sea-level anomalies from 2014 to 2017 and the theory of load-deformation of elastic spherical earth, this paper demonstrates that impacts of non-tidal ocean load can be quantitatively calculated on geodetic datums along the east coast of China, by using remove-restore technique and combining spherical harmonic analysis of gravity field and Green's functions to calculate loads. Temporal and spatial analyses on the impacts are conducted with Continuously Operating Reference Stations (CORS) sites along the coast and on the islands. This paper has drawn some conclusions as follows: (1) The impact of non-tidal ocean loads on the east coastal geoid ranges from −4.16 to 4.17 mm, that on ground gravity ranges from −15.44 to 17.02 some conclusions as follows: (1) The impact oranges from −7.55 to 6.69 mm. (2) The impacts are dominated by annual and semi-annual cycles. (3) The impacts appear to be more prominent in coastal areas and on islands than in inland areas. [ABSTRACT FROM AUTHOR]

With the rapid development of hydraulic fracturing technology, shale gas has become a significant natural gas resource in China. At present, SRV (stimulated reservoir volume) fracturing technology is widely used to exploit shale gas reservoirs. To evaluate the shale gas reserves and design a development plan, a simple and rapid method is needed to predict the production and performance of the multistage fractured horizontal wells with stimulated reservoir volume in shale gas reservoirs. Network fractures with different lengths and widths are not symmetrical to the horizontal well. To account for the complexity of the fracture system and desorption characteristics of shale gas, a semianalytical multiregion seepage model has been established to analyze the performance of multiple fractured horizontal wells. In this paper, a triple‐porosity dual‐permeability model is developed for simulating the flow mechanism of shale gas. Different lengths and widths of network fractures, different fracture intervals, and asymmetry distribution are considered in this model. By employing the principle of Poisson's superposition and Bessel transformation, the fundamental solution of instantaneous point source function has been derived to calculate the pressure response of each hydraulic fracture. Then, the mathematical model for unsteady performance evaluation in multiple fractured horizontal wells has been obtained to simultaneously solve the pressure response of every hydraulic fracture. The sensitivity analysis in terms of the lengths and widths of network fractures, fracture intervals, and the asymmetry distribution of a complex fracture system is presented. The research results show that the SRV morphology will exert a great influence on the performance of multiple fractured horizontal wells. [ABSTRACT FROM AUTHOR]

Mass level of fine particles (PM 2.5) in main cities in China has decreased significantly in recent years due to implementation of Chinese Clean Air Action Plan since 2013, however, O 3 pollution is getting worse than before, especially in megacities such as in Shanghai. In this work, O 3 and PM 2.5 were continuously monitored from May 27, 2018 to March 31, 2019. Our data showed that the annual average concentration of PM 2.5 and O 3 (O 3 -8 hr, maximum 8-hour moving average of ozone days) was 39.35 ± 35.74 and 86.49 ± 41.65 µg/m3, respectively. The concentrations of PM 2.5 showed clear seasonal trends, with higher concentrations in winter (83.36 ± 18.66 µg/m3) and lower concentrations in summer (19.85 ± 7.23 µg/m3), however, the seasonal trends of O 3 were different with 103.75 ± 41.77 µg/m3 in summer and 58.59 ± 21.40 µg/m3 in winter. Air mass backward trajectory, analyzing results of potential source contribution function model and concentration weighted trajectory model implied that pollutants from northwestern China contributed significantly to the mass concentration of Shanghai PM 2.5 , while pollutants from areas of eastern coastal provinces and South China Sea contributed significantly to the mass level of ozone in Shanghai atmosphere. Mass concentration of twenty-one elements in the PM 2.5 were investigated, and their relationships with O 3 were analyzed. Mass level of ozone had good correlation with that of Ba (r = 0.64, p < 0.05) and V (r = 0.30, p > 0.05), suggesting vehicle emission pollutants contribute to the increasing concentration of ozone in Shanghai atmosphere. Image, graphical abstract [ABSTRACT FROM AUTHOR]

We present a source inversion of the 2008 Wenchuan, China earthquake, using strong-motion waveforms and geodetic offsets together with 3-D synthetic ground motions. We applied the linear multiple time window technique considering geodetic and dynamic Green's functions computed with the finite-element method and the reciprocity and Strain Green's Tensor formalism. All ground motion estimates, valid up to 1 Hz, accounted for 3-D effects, including the topography and the geometry of the Beichuan and Pengguan faults. Our joint inversion has a higher moment (M0) than a purely geodetic inversion and the slip distribution presents differences when compared to 1-D model source inversions. The moment is estimated to be M0 = 1.2 × 1021 N·m, slightly larger than other works. Our results show that considering a complex 3-D structure reduces the size of large areas of 10 m slip or greater by distributing it in wider zones, with reduced slips, in the central portion of the Beichuan and the Pengguan faults. Finally, we compare our source with a relocated aftershock catalogue and conclude that the 4–5 m slip contours approximately bound the absence or presence of aftershocks. [ABSTRACT FROM AUTHOR]

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GF-1 satellite has the characteristics of high spatial resolution and short revisiting period, serving as the first satellite of the High-resolution Earth Observation System for National Science and Technology Major Project in China. The satellite carries two multi-spectral high-resolution cameras (panchromatic multispectral sensor, PMS) and four multi-spectral medium-resolution camera (wide field of view, WFV). GF-1 captured data play an important role in the identification of the underlying surface, and these data can be obtained free of charge from the website of the China Centre for Resources Satellite Data and Application. An important step for the application of GF-1 satellite data can be the interference removal of atmospheric molecules, aerosols, ozone, water vapor. The spectral response curves from Landsat8 (LC8) operational land imager(OLI) and GF-1 MSS/WFV were then analyzed in the visible and near the infrared bands. The results showed that the spectral range of LC8 OLI in the red- and near the infrared bands was relatively narrower than that of GF-1 MSS/WFV, whereas the spectral response function in the blue- and green bands was slightly different from that of GF-1 MSS/WFV, indicating that it is feasible to transplant LaSRC correction process to GF-1 MSS/WFV data. Since GF-1 satellite lacks the short-wave infrared band compared with LC8, the algorithm was modified to adapt to the characteristics of GF-1 channels. The atmospheric correction project was designed for the GF-1 satellite MSS/WFV data, including the algorithm analysis and code implement based on 6S atmospheric radiation simulation model and C++ programming language. Some parameters were used to estimate initial aerosol, including total atmospheric transmission, gaseous transmission, atmosphere spherical albedo and actual values of digital elevation model, atmospheric precipitation, ozone content. The loop calculation of the aerosol optical thickness(AOT) was carried out until the ratio between the red- and blue bands of GF-1 MSS/WFV data equal to the prescribed ratio of MODIS, according to the relationship between the blue- and the red surface reflectance known from MODIS. The results can be obtained the surface reflectance with the minimum residual error during different Ångström coefficients, and retrieved the aerosols in the pixel level of GF-1 MSS/WFV data. The pixel aerosol and these parameters were then substituted into 6S model to calculate the surface reflectance. Since the project was equipped a data file containing the atmospheric precipitation and ozone content at the current day, the surface reflectance could be obtained when only inputting GF-1 MSS/PMS data. Because the data of atmospheric influence gases, such as ozone and water vapor, on the same day of the data to be corrected were sometimes difficult to identify, two schemes can be provided, one is to use the data at that time, the other is to use the daily values of ozone and water vapor in past six years instead. The experimental results show that the proposed method has a good effect on the atmospheric correction in the middle and low latitudes that covered by vegetation, such as farmland and trees, but not good effect on that of the bare land and building surface that covered by sparse vegetation. Based on 6S model and LaSRC correction process, the correlation coefficient of the atmospheric correction between GF-1 MSS/WFV and LC8 OLI was from 0.825 to 0.972, indicating a high correlation of atmospheric correction results for two satellites. WFV similar spatial resolution to that of LC8 OLI was in good agreement with that of LC8 OLI atmospheric correction compared with that of MSS. The results show that it is convenient and operable for the GF-1 satellite data atmospheric correction method using the self-estimation aerosol parameters in the pixel level based on 6S model and LaSRC process. This promising atmospheric method can be very suitable for the land surface application, such as agricultural and forestry monitoring in growing season. At present, this method has been successfully implemented on Remote Sensing data processing platform Remote Sensing Desktop (RSD) in China. [ABSTRACT FROM AUTHOR]

This study compares the news framing of Nixon's visit to China in 1972 in two U.S. elite newspapers: The New York Times and The Wall Street Journal. Through conducting a framing analysis, this study tried to examine how The New York Times and The Wall Street Journal cover Nixon's visit to China in 1972 differently and the reasons for such difference in their framing. The results showed that the dominant ideology in American society functioned as the main source of framing in the coverage of the Presidents' visits. Both newspapers' coverage reflected the ideology of anti-communism in the 1970s. However, the analysis also demonstrated that the contingent ideology and journalistic ideology in the newsroom also played an essential part in news judgment. [ABSTRACT FROM AUTHOR]

The tourism industry is a nonnegligible contributor to global CO2 emissions, and formulating policy around emission reduction for sustainable tourism requires understanding the drivers contributing to the growth of tourism CO2 emissions. This paper develops an alternative decomposition technique that uses data envelopment analysis (DEA) and distance functions to examine the sources of change in tourism CO2 emissions; this method offers advantages in measuring the contribution of factor inputs to CO2 emissions change and has flexible data requirements. An empirical application using provincial panel data from China's tourism industry during the 2005–2016 period is performed. The results indicate the following: The scale effect induced by economic growth in tourism was the largest factor driving CO2 emissions growth; technical change played a dominant role in reducing CO2 emissions, and technical efficiency change exerted a negligible positive effect on the CO2 emissions increment; the emissions indices associated with labour, capital, and attractive resources generated significant promoting effects on CO2 emissions growth; and the emissions index associated with energy had a minor inhibitory effect. In addition, the drivers of tourism CO2 emissions clearly varied by region and province, and three driving modes of change in provincial CO2 emissions were summarized. This study extends the application of decomposition techniques in the field of tourism studies, and our results provide valuable insights for policymakers and business entities aiming to adopt measures to curb tourism CO2 emissions and promote sustainable tourism. [ABSTRACT FROM AUTHOR]

Meretrix petechialis is an important commercial aquaculture species in China. During the clam culture period, mass mortality events often occurred due to the Vibrio infection. In this paper, M. petechialis were challenged with Vibrio parahaemolyticus immersion to simulate a natural infection, and the infection process were divided into four phases including latency, prodrome, onset and recovery phases based on the clam mortality data. Then, the dynamic response of clams to Vibrio infection at different infection phases were investigated by transcriptome analysis. A total of 38,067 differentially expressed genes (DEGs) were identified at different infection phases. DEG annotations showed that immune-related and metabolism-related signaling pathways were enriched, indicating that immune defense and metabolism process play key roles during bacterial infection. Three kinds of expression pattern were classified by cluster analysis, including U-shape, L-shape and inverted V-shape. Anabolism and cellular growth proliferation related signaling pathways were repressed (long-lasting or transient) during bacterial infection. However, the immune related signaling pathways with different immune functions showed induction expression or repression expression against bacterial infection, which indicated that immune system take different strategies against bacterial infection. Furthermore, some signaling pathways such as PI3K-Akt signaling pathway both involved in immune defense and cell metabolism. This study provides a sight that the dynamic immunity and metabolic responses may be integrated to improve the host survival and shift more energy for immune defense. • Four infection phases were divided based on clam mortality data after vibrio challenge. • Transcriptome analysis revealed the dynamic response of clam during infection. • The immune-related signaling pathways implement different strategies against vibrio infection. • An anabolism suppression was found response to bacterial infection. [ABSTRACT FROM AUTHOR]

Knowledge of vertical distribution of air pollutants is important for understanding the mechanisms underlying haze pollution. In this paper, we characterize the vertical structure of air pollutants based on ground-based Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) measurements in the wintertime in Hefei, East China. Both NO 2 and aerosol show exponentially decreasing profile with high concentrations concentrated close to the surface, suggesting the major emissions are at ground level. SO 2 profiles extend to slightly higher altitudes than NO 2 , which might be due to the SO 2 emissions from elevated point sources (e.g., power plants). Elevated HCHO was observed in the middle layer during noon time, probably indicating that the larger effect of the photochemical formation of atmospheric HCHO rather than direct HCHO emissions. Potential source contribution function (PSCF) and concentration-weighted trajectory (CWT) models were used to evaluate the potential sources of Hefei's air pollution in the lower, middle and upper boundary layer. The results revealed that the major regional source of NO 2 and aerosol were located in the northern and eastern part of Anhui and the transport mainly occured in the lower layer. Transported SO 2 from the northwestern regions in the middle layer made great contribution to SO 2 in Hefei. HCHO was mostly produced locally while the transport of HCHO from potential source areas was negligible. To further explore the potential source contributions affecting haze pollution, PSCF and CWT analysis for heavy haze episodes suggested that the potential source areas for aerosol were almost located in the northern region, the northwestern region, and the YRD region. Our findings provide a more comprehensive understanding for regional transport through the study on potential sources at different altitudes, which are useful for designing collaborative air pollution control strategies on a regional scale. • Vertical distribution of air pollutants is investigated to identify potential sources at different altitudes during winter. • Both NO 2 and aerosol show exponentially decreasing profile with high concentrations concentrated close to the surface. • SO 2 and HCHO profile typically extended to higher altitudes than NO 2 and aerosol did during winter. • The main potential sources for aerosol were located in the northern region, the northwestern region, and the YRD region. • This study is useful for designing collaborative air pollution control strategies on a regional scale. [ABSTRACT FROM AUTHOR]

Ground-based two-dimensional (2D) Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) measurements of nitrogen dioxide (NO 2) were collected continuously from June 2015 to May 2016 in Hefei, China. The spatial distribution of NO 2 concentrations showed that more air pollution was present in eastern and southeastern direction from the study site, and these areas were located in the center of the city and economic developing zone. The seasonal variations of NO 2 concentrations were distinct, and the highest levels were detected in winter, while the lowest levels were detected in summer. The mean concentration of NO 2 during the heating season (November–March of the following year) was 6.56 ppbv, while that during the non-heating season (April–October) was 4 ppbv. The highest concentrations of NO 2 , carbon monoxide (CO), and PM 2.5 were all observed during the heating season. The results from the potential source contribution function (PSCF) analysis suggested that NO 2 pollution in the summer was caused primarily by long-range transport from the east, while that in winter showed significant local influences. By combining the analyses of meteorological trajectory pressure profiles and aerosol optical depths (AODs), the sources of NO 2 during the heating season were found to be mainly local emissions, while those during the non-heating season were mainly from long-range transportation. Image 1 • NO 2 was monitored during 2015–2016 in Hefei, China, with 2D MAX-DOAS data. • High NO 2 levels were concentrated in urban and industrial areas. • Local emission sources were the dominant sources of NO 2 in winter. • Haze and NO 2 pollution had simultaneous variations during the heating seasons. [ABSTRACT FROM AUTHOR]

Extreme PM 2.5 and nonmethane hydrocarbon (NMHC) pollution often occurs simultaneously during the winter. To study the formation mechanism of two pollution events in Chengdu from 23 December 2016 to 31 January 2017, we explored the weather conditions, chemical composition, secondary pollutant conversion, aerosol hygroscopic growth, and potential source contribution function (PSCF) during this period. During the study period, the humidity was high (67.9%), the wind speed was low (1.0 m s−1), the height of the planetary boundary layer was low (463.4 m), and the atmosphere remained stationary. The potential source regions of PM 2.5 and NMHCs were locally polluted sites in the southwestern and southern regions of Chengdu, affected by the southwesterly air mass trajectories. PM 2.5 and sulfur oxidation ratios (SOR), nitrogen oxidation ratios (NOR) and secondary organic aerosol formation potential (SOAP) showed a strong positive correlation. As pollution increased, the conversion from SO 2 , NO x and NMHCs to sulfate, nitrate and SOAs increased, resulting in an increase in the secondary aerosol concentration. As the relative humidity increases, aerosols begin to undergo rapid hygroscopic growth, which seriously affects the visibility of the atmosphere. In general, pollutant emissions, static weather, and secondary conversion, among other factors, lead to the occurrence of this persistent extreme haze pollution. Image 1 • The three important factors contributing to the low visibility in Chengdu were identified. • Mobile sources in Chengdu air pollution are becoming increasingly significant. • Secondary transformation of organic matter (OM) plays an important role in the formation of haze. • High potential source contribution function (PSCF) values of pollutants are in the southwestern and southern regions. Stationary and stable meteorological conditions, favorable secondary transformation and high relative humidity are the causes of extreme haze pollution events. [ABSTRACT FROM AUTHOR]

To tackle urban water issues, the Chinese government has promoted the construction of sponge cities in recent years. Thirty cities have been designated as experimental sites to serve as models for future sponge city construction, as more than 80% of the built-up urban areas in China must reach the standards of sponge cities by 2030. Greening plants play an important role in sponge cities, and water-use efficiency (WUE) is a vital index to determine whether plants could adapt to and grow healthily in environments with water deficits. In this study, WUE of greening plants was quantified by measuring the stable carbon isotope fractionation. Suitable plants for the green spaces in Guyuan sponge city, in northern China, were selected based on their WUE, and the main factors affecting WUE were studied in four habitats within the city. Plant species identity had the greatest effect on WUE, while habitat and plant life form had lower effect, illustrating that WUE is a relatively stable and reliable index for the classification of plant species. We can improve the WUE and ecological function of green spaces in sponge cities by using isotope technology to select suitable plant species with high WUE. To our knowledge, this study is the first to select plant species for sponge city by using this method, providing a quick and scientific method for the selection of greening plants for future sponge cities. [ABSTRACT FROM AUTHOR]

Haze formation involves many interacting factors, such as secondary aerosol formation, unfavourable synoptic conditions and regional transport. The interaction between these factors complicates scientific understanding of the mechanism behind haze formation. In this study, we investigated the factors resulting in haze events in Longyou, a city located in a basin in China. Aerosol samples of PM 2.5 were collected for subsequent chemical composition analysis between 11 January and 5 February 2018. The impacts of wind on PM 2.5 , SO 2 and NO 2 concentrations were analysed. Besides, the origin of air parcels and potential sources of PM 2.5 were analysed by backward trajectory, potential source contribution function (PSCF) and concentration-weighted trajectories (CWT). Among the water-soluble ions identified, NO 3 − had the highest concentration, with further analysis demonstrating the haze evolution was mainly driven by the reactions involving NO 3 − formation. The dramatic increase of nitrate is mainly due to the homogeneous reaction of nitric acid with ammonia, while sulfate is likely due to heterogeneous reactions of NO 2 , SO 2 and NH 3. The average wind speed was less than 2 m/s during the aerosol sampling period, which could be considered as a stagnant state. Pollutants emitted by industrial area located in the northeast Longyou were probably brought to observation sites by continuous wind from northeast and accumulated gradually. Air parcels originating from the northeast of Zhejiang province also had large effects on haze pollution in Longyou. Together, our results showed that rapid secondary aerosol formation and unfavourable synoptic conditions are the main factors resulting in haze pollution in Longyou. Image 1 • Unfavourable meteorological conditions resulted in the accumulation of PM 2.5 and NO 2. • The evolution of haze pollution was mainly driven by the reactions involving NO 3 − formation. • Homogeneous reactions might play an important role nitrate formation. • Two haze episodes with the same shapes were affected by different transport paths. [ABSTRACT FROM AUTHOR]

Abstract China implemented the National Air Pollution Prevention and Control Action Plan since 2013, aiming at significantly improving air quality in major areas and cities in 2017. To investigate the changes of the characteristics of PM 2.5 and its major chemical components, formation mechanisms, and sources apportionment during 2013–2017 in urban Handan, which was one of the top polluted cities in China, we analyzed the chemical compositions of PM 2.5 samples for the entire year of 2013 and 2017, as well as a comprehensive dataset including continuous online hourly observations of the meteorological parameters and major air pollutants, i.e., SO 2 , NO 2 , and O 3 in this study. Potential Source Contribution function (PSCF) analysis was applied to investigate the potential source regions contributing to high PM 2.5 pollution episodes. The results showed that the concentration of major air pollutants except ozone decreased, and the proportion of PM 2.5 decline in Handan (37.0%) had reached the requirements (25%) of the National Air Pollution Prevention and Control Action Plan. The major chemical compositions of PM 2.5 decreased significantly, but the percentage of secondary organic aerosols increased from 37.0% in 2013 to 40.0% in 2017. The higher proportion of secondary components implied more severe secondary pollution. The PSCF analysis indicated that the significant local contribution and short-range transport in the surrounding areas were the major sources of heavy pollution episodes in Handan. This study highlights the importance of emission reduction of atmospheric organic compounds and joint control actions on a regional basis during heavy pollution episodes. Highlights • Changes of chemical composition of PM 2.5 during 2013–2017 in urban Handan, China, were investigated. • Distinct seasonal variations of concentration and composition of PM 2.5 were observed. • Changes in chemical composition under different degrees of pollution in winter were analyzed. • The major sources to heavy pollution episodes in Handan were analyzed. [ABSTRACT FROM AUTHOR]

To evaluate tunnel ground vibrations induced by fault-slip in underground mine, it is crucial to resolve the peak ground velocity (PGV) and the peak ground acceleration (PGA). To quantify PGV and PGA in three-dimensional space, the forces acting on the fault and the seismic wave radiation pattern were investigated. A qualitative method for ground vibration of tunnels induced by fault-slip in underground mine was proposed and applied to the Yongshaba Phosphate Mine, China. Firstly, the moment tensor of the significant fault-slip event was obtained using a full waveform source inversion method based on the recorded seismograms. It describes the forces acting on the fault and the seismic wave radiation pattern. Then, the inverted source was used as a reference to evaluate the ground vibrations under possible larger seismic magnitudes and probable slip models. The vibrations along the tunnels resulted from different slip models were calculated using the representation theorem by the convolution of the Green's function and the corresponding moment tensor. The velocity series and the acceleration series were obtained. Results show that the spatial distribution of the ground motions are closely related to sensor-source distance, the sensor-source azimuth, as well as the strike, dip, and rake configuration of the slip model. The seismic magnitude has an exponential effect on the distribution of the PGVs and PGAs. The PGV and PGA have similar spatial distribution patterns. The PGV values of the north and vertical components show nearly 5 times higher than the east component. The vertical vibrations affect the widest area. The ground support principles were suggested considering the parameters including the PGVs, the PGAs, the rock mass rating, and the dynamic loads. [ABSTRACT FROM AUTHOR]

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This study analyzed the structure and ecological characteristics of extensive green roofs in cities, proposed the concept of combining landscape and ecological environment elements, and expounded the guiding role of green roofs in China's future urban design, in order to provide new ideas for the effective development of the ecological and aesthetic functions of the extensive green roofs in the future urban landscape design. [ABSTRACT FROM AUTHOR]

Carbon monoxide (CO) emissions in China in 2005–2010 were estimated by inversion, using the Green's function method from vertical CO profiles derived from MOPITT Version 5 satellite data and a tagged CO simulation, and validated with independent in situ observations from the World Data Centre for Greenhouse Gases. Modeling with a posteriori emission successfully reproduced CO outflow from the continent to the East China Sea, Sea of Japan, and Japanese islands during winter and spring, and compensated for underestimates in central and eastern China in summer. A posteriori emissions showed large seasonal variations in which December and March emissions were on average 23% larger than August emissions, consistent with other studies. Estimated Chinese CO emissions were 184.4, 173.1, 184.6, 158.4, 157.4, and 157.3 Tg/year for 2005–2010, respectively. The decrease after 2007 is partly attributed to Chinese socioeconomic conditions and improved combustion efficiency. [ABSTRACT FROM AUTHOR]

SUMMARY Through analysis of the Rayleigh wave and Love wave empirical Green's functions recovered from cross-correlation of seismic ambient noise, we image the radial anisotropy and shear wave velocity structure beneath southern Tibet and the central Himalaya. Dense ray path coverage from 22 broadband seismic stations deployed by the Himalayan Nepal Tibet Seismic Experiment project provides the unprecedented opportunity to resolve the spatial distribution of the radial anisotropy within the crust of the central Himalaya and southern Tibet. In the shallow subsurface, the obtained results indicate significant radial anisotropy with negative magnitude ( VSV > VSH) mainly associated with the Indus Yarlung Suture and central Himalaya, possibly related to the fossil microcracks or metamorphic foliations formed during the uplifting of the Tibetan Plateau. With increasing depth, the magnitude of radial anisotropy varies from predominantly negative to predominantly positive, and a mid-crustal layer with prominent positive radial anisotropy ( VSV < VSH) has been detected. The top of the mid-crustal anisotropic layer correlates nicely with the starting depth of the mid-crustal lower velocity layers detected in our previous study. The spatial correlation of the positive radial anisotropy layers and mid-crustal lower velocity layers might suggest lateral crustal channel flow induced alignment of mineral grains, most likely micas or amphiboles, within the mid-crust of the central Himalaya and southern Tibet. This observation provides independent seismic evidence to support the thermo-mechanical model, which involves the southward extrusion of a low viscosity mid-crustal channel driven by the denudation effect focused at the southern flank of the Tibetan Plateau to explain the tectonic evolution of the Tibetan-Himalayan orogen. [ABSTRACT FROM AUTHOR]

From analyses using near-field and teleseismic data, we estimate the nipture speed of the 2010 Qinghai, China, earthquake (MW 6.9). Comparisons of model calculations of the initiations to the observed near-field seismogram at station YUS indicate a fast supershear rupture propagation of about 5.0 km/s. From the teleseismic analyses using an envelope deconvolution method with an empirical Green's function event, two high-frequency pulses are identified at 6.5 km and 41.8 km southeast of the epicenter, indicating two subevents. The location and timing of the high-frequency events also show a supershear rupture velocity of 4.7 to 5.8 km/s. The supershear speed of the rupture likely contributed to the severe damage caused in the forward direction of the rupture toward the town of Yushu. [ABSTRACT FROM AUTHOR]

SUMMARY In this paper, we conduct ambient noise seismic tomography of northwestern China and adjacent regions. The data include 9 months (2009 January to 2009 September) three-component continuous data recorded at 146 seismic stations of newly upgraded China Provincial Digital Seismic Networks and regional Kyrgyzstan and Kazakhstan networks. Empirical Rayleigh and Love wave Green's functions are obtained from interstation cross-correlations. Group velocity dispersion curves for both Rayleigh and Love waves between 7 and 50 s periods were measured for each interstation path by applying the multiple-filter analysis method with phase-matched processing. The group velocity maps show clear lateral variations which correlate well with major geological structures and tectonic units in the study region. Shear wave velocity structures are inverted from Rayleigh wave and love wave dispersion maps. The results show that the Tibetan Plateau has a very thick crust with a low-velocity zone in its mid-lower crust. Along the northern margin of the plateau where a steep topographic gradient is present, the low-velocity zone does not extend to the Tarim basin which may indicate that crustal materials beneath the Tarim basin are colder and stronger than beneath the plateau, therefore inhibit the extension of mid-lower crustal flow and deformation of the Tibetan Plateau, resulting in very sharp topography contrasts. In the northeastern margin with a gentle topographic gradient toward the Ordos platform, the low-velocity zone diminishes around the eastern KunLun fault. Meanwhile, our results reveal obvious lateral velocity changes in the crust beneath the Tarim basin. In the upper crust, the Manjaer depression in the eastern Tarim basin is featured with very low velocities and the Bachu uplift in the western Tarim basin with high velocities; in the mid-lower crust, the northern Tarim basin in general displays lower velocities than the southern part along latitude ∼40° N with an east-west striking, which is consistent with the high magnetic anomaly zone and may be related to the central suture belt connecting the south and north of Tarim basement blocks together in Pre-Sinian. [ABSTRACT FROM AUTHOR]

Extremely valuable strong-motion records during the 2008 Wenchuan earthquake were obtained at a number of stations close to the source region. We estimate the characterized source model for simulating ground motions using the empirical Green's function (EGF) method and the hybrid method using strong-motion data from the earthquake. The characterized source model consists of several asperities with large slip in the entire rupture area of the earthquake. The locations of the asperities that generate strong motions were determined from the timing of pulse arrivals in observed records near the source fault. Because aftershock records of the earthquake had not been released yet, observed records from an aftershock (MW 4.9) of the 2008 Iwate-Miyagi Nairiku earthquake (MW 6.9), which occurred in the shallow inland crust of the northeastern region in Japan, are used as substitutes for the EGFs. The synthetic motions obtained by the EGF method agree well with the observed records with respect to acceleration and velocity waveforms in the period range of less than 2 s. Broader-band strong motions are simulated by the hybrid method, which combines the numerical method for periods longer than 2 s with the EGF method for periods shorter than 2 s. The best-fit source model was obtained with stress drop on each asperity of approximately 13 MPa. The ground motions numerically simulated at the Bajiao station (SFB) near an asperity and in the forward rupture direction show directivity effects that are too strong in comparison with the observed motions. We examined the influence of rupture-velocity fluctuation on the synthetic waveforms in the forward rupture direction near the asperity, finding that the forward directivity effects decrease with increase in velocity variances. [ABSTRACT FROM AUTHOR]

Green's functions (GFs) of surface wave propagation between two receivers can be estimated from the cross-correlation of ambient noise under the assumption of diffuse wavefields or energy equipartitioning. Interferometric GF reconstruction is generally incomplete, however, because the distribution of noise sources is neither isotropic nor stationary and the wavefields considered in the cross-correlation are generally non-diffuse. Furthermore, medium complexity can affect the empirical Green's function (EGF) from the cross-correlation if noise sources are all far away (i.e. approximately plane-wave sources), which makes the problem non-linear. We analyse the effect of uneven ambient noise distribution and medium heterogeneity and azimuthal anisotropy on phase velocities measured from EGFs with an asymptotic plane wave (far-field) approximation (which underlies most constructions of phase velocity maps). Phase velocity bias due to uneven noise distribution can be determined (and corrected) if the noise energy distribution and the velocity model are known. We estimate the (normalized) azimuthal distribution of ambient noise energy directly from the cross-correlation functions obtained through ambient noise interferometry. The (smaller, second order) bias due to non-linearity can be reduced iteratively, for instance by using the tomographic model that results from the inversion of uncorrected data. We illustrate our method for noise energy estimation, phase velocity bias suppression, and ambient noise tomography (including azimuthal anisotropy) with data from a seismic array (26 stations) in SE Tibet. We show that the phase velocity bias due to uneven noise energy distribution (and medium complexity) in SE Tibet has a small effect (<1 per cent) on the isotropic part phase velocities (for T= 10–30 s) and the azimuthal anisotropy obtained before and after bias correction shows very similar pattern and magnitude. [ABSTRACT FROM AUTHOR]

The computationally expensive cost and complexity are practical challenges in solving the three-dimensional (3-D) inverse problem in the time domain, and many real-world surveys are still inverted in one dimension (1-D). We present a new way to invert transient electromagnetic (TEM) data from a rectangular fixed loop to image subsurface electrical conductivity, which overcomes this limitation and permits efficient implementation of the inversion process on a personal computer. A TEM signal was transformed to the real and imaginary components of a frequency-domain (FD) electromagnetic (EM) response. The transformation was performed by a regularization inversion method. The recovered FD EM response was used as the data for the 3-D inversion. The forward problem and sensitivity were solved by using a staggered-grid finite-difference technique in the FD, and the background Green's function was carried out using the virtual interface method. The non-linear conjugate gradient method (NLCG) was employed to solve the 3-D inverse problem. A synthetic example revealed the basic functionality of the approach, and the FD inversion of a TEM field dataset acquired in the northeastern Qinshui Basin, Shanxi Province, China demonstrated a real-world application. Our inversion approach is general and suitable for different-type sources, such as a vertical magnetic dipole or horizontal electric dipole. • We have showed how the inversion of TEM data can be efficiently solved in the FD. • The synthetic data inversion to test the effectiveness of the inversion algorithm. • Inversion result of a field data agrees well with the geology and seismic result. • Our method has proved to be a new and valid way of interpreting TEM data. [ABSTRACT FROM AUTHOR]

• Sodium is essential for lead-barium glass forming. • Previous chemical analysis of ancient lead-barium glass underestimates the sodium content. • Opaque lead-barium glass cannot be produced during the primary production. • Lead-barium glass can be produced by mixing natron glass with lead and barium minerals. Lead-barium glass appeared during the late Warring States period in China (457 - 221 BCE) and was considered as a Chinese invention due to the unique presence of high barium. There is no indication as to how it was made. A set of twenty-four different combinations of possible raw materials were melted to test and systematically evaluate the possible recipes for lead-barium glass. Specifically, the function and source of sodium in lead-barium glass were explored. The results show that sodium source is crucial for lead-barium glass forming in this particular system. This paper explores an alternative formulation since sodium flux is not reported in historical Chinese sources, in which the Na 2 O is provided by including soda-lime glass in the mixture. This particular formulation provides a potential explanation for the source of the sodium in lead-barium glass. [ABSTRACT FROM AUTHOR]

Handan is a heavily polluted city in the northern China. From 6 to December 31, 2015, PM 1.0 and PM 2.5 samples were synchronously collected for 23.5 h of each day at an urban site in Handan, to study the chemical composition and sources of aerosols present during wintertime in North China Plain (NCP). The average mass concentrations of PM 1.0 and PM 2.5 in Handan were as high as 189.2 μg/m3 and 252.4 μg/m3, while the average PM 1.0 /PM 2.5 ratio was relatively low (74.6%) compared with the results in megacities. Overall, the chemical characteristics of PM 1.0 and PM 2.5 were quite similar during the campaign. During pollution episodes, SNA (sulphate, nitrate, and ammonium) ions were found dramatically increased, while the fraction of organic carbon (OC) and elemental carbon (EC) decreased in both PM 1.0 and PM 2.5. As a result of reduced photochemical reactions, the weights of secondary organic carbon (SOC) in PM 1.0 and PM 2.5 decreased during the pollution episode. Besides, liquid water content (LWC) were found effective for SNA formation. The positive matrix factorization (PMF) model identified similar sources distributions for PM 1.0 and PM 2.5 , and the top three contributors were coal combustion, secondary inorganic aerosols, and industrial emissions. Moreover, the potential source contribution function (PSCF) demonstrated that regional sources in southern Handan might be crucial contributors to haze pollution in Handan. • The characteristics of PM 1.0 and PM 2.5 in Handan were investigated and compared. • Aqueous-phase reactions were found to significantly enhance SNA formation. • Coal combustion and SIAs were the main sources of PM 1.0 and PM 2.5 in winter. • The southern region of Handan had a relatively large potential source contribution. [ABSTRACT FROM AUTHOR]

• The ecosystem carbon fluxes were affected by precipitation variation. • Drought weakened the capacity of the ecosystem carbon sink. • Drought decreased GEP, NEP and Reco. • Main driver factors of GEP and NEP were SWC, coverage and standing biomass. • Ecosystem was converted from carbon sink to carbon source with press-drought. Precipitation has an impact on both gross ecosystem productivity (GEP) and ecosystem respiration (Reco), which ultimately influences net ecosystem productivity (NEP). A positive NEP denotes an ecosystem functioning as a carbon sink; whereas, a negative NEP denotes an ecosystem functioning as a carbon source. Therefore, drought plays an important role in the carbon balance of an ecosystem. However, little is known about the point at which the ecosystem converts from a carbon sink to a carbon source in extreme droughts. Such knowledge is crucial for predicting terrestrial carbon cycling under climate change, and consequently, was the subject of this study. We imposed two types of drought treatments on desert-grassland: (1) press-drought, in which the quantity of natural precipitation was reduced by 66% from May to August; and (2) pulse-drought, in which the quantity of natural precipitation was reduced by 100% during June and July. Reco and NEP were measured and GEP was calculated and then regression analyses were employed to determine the point at which the carbon sink shifts to a carbon source. The regression equation of NEP (μmol·m−2·s−1) on Reco (μmol·m−2·s−1) took the form: NEP = 0.504 Reco – 0.086 and, consequently, when Reco equaled 0.171 μmol·m−2·s−1, there was zero change in the carbon sink and GEP also equaled 0.171 μmol·m−2·s−1. Below this value, the ecosystem functioned as a carbon source, whereas above this value, the ecosystem functioned as a carbon sink. Structural equation models (SEM) demonstrated that coverage, standing biomass, pH, soil water content and total soil carbon were the main driving factors on desert grassland ecosystem carbon fluxes. [ABSTRACT FROM AUTHOR]

Atmospheric mercury cycling in coastal urban areas in East China is complex due to the combined influence of both intensive inland anthropogenic emission sources and marine air masses. In this study, continuous measurements of total gaseous mercury (TGM) concentrations were conducted from December 2017 to December 2018 at a coastal site, Shilaoren, in Qingdao, East China. Concentrations of TGM ranged from 0.59 ng m−3 to 24.46 ng m−3 with a mean value of 2.28 (±0.87) ng m−3. TGM exhibited a distinct diurnal cycle mostly with an early morning peak and an afternoon minimum. The daily minimum and mean TGM concentrations with the occurrence of sea-land breeze circulation were higher than those without. In addition, TGM concentrations exhibited a strong dependence on wind direction with an average value of 2.41 ng m−3 in air masses from inland, ~24% higher than that from the ocean. Correlation analysis suggested that mobile combustion was a major anthropogenic emission source to TGM at Shilaoren, and coal-fired power plants became a significant contributor in winter. Potential source contribution function analysis and episodic studies attributed high TGM concentrations (>90th percentile value = 3.28 ng m−3) to regional transport from anthropogenic emission sources in the neighboring cities or provinces in eastern China. Frequently occurring typhoons contributed to the high TGM episodes in summer. Prior to the arrival of a typhoon, TGM concentrations rose sharply due to transport from polluted regions in East Asia as well as downdrafts at the front and lateral edges of a typhoon, whereas dropped to a mean concentration of 1.57 ng m−3, comparable to the globally background value, as the typhoon arrived. This study contributes to a better understanding of the effects of meteorological processes including sea-land breeze and typhoons as well as regional transport on atmospheric mercury cycling in eastern China's coastal environments. • TGM concentrations under offshore wind increased by 24% compared to onshore wind. • Sea-land breeze circulation was conducive to TGM accumulation in coastal Qingdao. • Typhoons were responsible for the TGM spikes observed in summer. • East China was the major source region for TGM in Qingdao. [ABSTRACT FROM AUTHOR]

Combined effects of vegetation, tide and sediment on the carbon dynamics in the intertidal creek-marsh systems remain unclear. We investigated the variability of dissolved organic (DOC) and inorganic carbon (DIC), and particulate organic (POC) and inorganic carbon (PIC) in the tidal creeks within the Poaceae and Cyperaceae communities on flood-ebb cycle in a salt marsh of eastern China. In the Poaceae creek with high plant biomass and soil carbon stock, the DOC concentrations were higher by on average 1.00–1.48 times than that in the Cyperaceae creek across all seasons and spring and neap tide stages, while the difference of DIC was not notable. The POC and PIC concentrations were lower in the Poaceae creek compared to the Cyperaceae creek. Spring tides increased the carbon concentrations (except for PIC) in both creeks by on average 7–40%, relative to neap tides. Seasonal variations of sedimentary rate within the communities probably result in the discrepancy of particulate carbon loading between the creeks. The Poaceae creek functioned as a source of DOC and DIC throughout a year but as a sink of POC and PIC in summer and autumn, while it turned to a weak source of PIC in winter and spring. The Cyperaceae creek exhibited as a source of all carbon components throughout a year. We suggest that vegetation type (with soil carbon stocks), tidal regimes and sedimentary dynamics would synergistically determine the fate of carbon in the creeks. Our results are helpful in reliable estimates of carbon transport between the coastal marsh and the adjacent ocean. • Poaceae creek functioned as source of DOC and DIC, and seasonal POC and PIC sink. • Cyperaceae creek exhibited as a net source of dissolved and particulate carbon. • Vegetation, tide and sediment synergistically modified carbon loading in creeks. [ABSTRACT FROM AUTHOR]

The present study aims to investigate temporal evolutions of particulate matter (PM) concentrations and its association with the meteorology and aerosol optical depth (AOD) during autumn and winter of 2014–2017 at an urban city, Nanjing in the Yangtze River Delta, East China. The seasonal mean PM 2.5 (PM 10) was found maximum and minimum with 81.2 ± 41.5 μg m−3 (135.6 ± 57.1 μg m−3) and 33.7 ± 19.1 μg m−3 (65.8 ± 34.5 μg m−3) during winter and autumn seasons, respectively. Furthermore, the mean ratio of PM 2.5 /PM 10 was around ~0.57 for the entire study period, with a lower contribution (0.53) in autumn and higher (0.60) in winter. However, the seasonal mean AOD 440 , precipitable water vapor content, Ångström exponent (AE 440-870) was found maximum with 0.97 ± 0.31, 1.58 ± 0.80 cm, and 1.14 ± 0.23 during autumn, and a minimum of 0.62 ± 0.34, 0.60 ± 0.27 cm, and 1.29 ± 0.19 in winter, respectively. The potential source contribution function (PSCF) and concentration weighted trajectory (CWT) models revealed considerable long-distance transport of PM 2.5 from north and northwest China. Besides, the concentration bivariate probability function (CBPF) revealed a significant contribution of PM 2.5 occurred when the winds blown from southerly and northwesterly directions. The relationship between PM 2.5 and meteorology found that PM 2.5 concentration had a positive relationship with AQI, while negative correlations with the major meteorological parameters. A notable spatial heterogeneities and trends were observed in AOD and AE, with negative correlations (−0.5 to 0) in winter over East China. Image 1 • Quantification of PM concentrations and air quality during autumn and winter seasons. • The concentrations of PM 2.5 found maximum in winter relative during autumn. • AOD showed high in autumn clearly demonstrates negative correlation with PM. • The CWT analysis revealed a significant contribution to PM during winter. • The meteorological variables showed negative relationship with PM in all seasons. [ABSTRACT FROM AUTHOR]

• The N and O isotopic values both have a rising tendency as the temperature drops. • Proportion for the OH pathway correlates significantly with latitude all year round. • Coal combustion is the primary source of NO x at Chinese megacities, especially in winter. • Residential coal combustion is the major source for the high PM 2.5 pollution. In China, nitrate (NO 3 −) becomes the main contributor to fine particles (PM 2.5) because the emissions of its precursor, nitrogen oxides (NO x), were not recognized and controlled well in recent years. In this work, sources, conversion, and geographical origin of NO x were interpreted combining the isotopic information (δ15N and δ18O) of NO 3 − and dual modelling at five Chinese megacities (Beijing, Shanghai, Guangzhou, Wuhan and Chengdu) during 2013–2014. Results showed that the δ15N-NO 3 − values (n = 512) ranged from −12.3‰ to +22.9‰, and the average δ18O-NO 3 − value was +83.4‰ ± 17.2‰. The isotopic compositions both had a rising tendency as ambient temperature dropped, attributing largely to the source changes. Bayesian model indicated the percentage for the OH pathway of NO x conversion had a clear seasonal variation with a higher value during summer (58.0% ± 9.82%) and a lower value during winter (11.1% ± 3.99%); it was also significantly correlated with latitude (p < 0.01). Coal combustion was the most important source of NO x (31.1%−41.0%), which was geographically derived from North China and other south-central developed regions implied by Potential Source Contribution Function (PSCF). Apart from Chengdu, mobile sources was the second largest contributor to NO x. This source was extensive but uniformly distributed all around the typical urban agglomerations of China. Biomass burning and microbial processes shared similar source areas, mostly originating from the North China Plain and Sichuan Basin. Based on the NO x features, we infer that residential coal combustion was the primary source of heavy PM 2.5 pollution in Chinese megacities. Controlling the source categories of these regional priorities would help mitigate atmospheric pollution in these areas. [ABSTRACT FROM AUTHOR]

The Early-Mesozoic collision between the North and South China Cratons resulted in different tectonic and geologic structures including the Tanlu Fault zone. One way to understand the geodynamic processes beneath these structures is by studying the velocity structures and spatial distribution of earthquakes in the region. We performed ambient noise tomography for the region around the central-southern Tanlu Fault zone using the vertical component of continuous ambient noise data obtained in central East China. Empirical Green's functions were retrieved from ambient noise cross-correlation functions, from which we extracted the Rayleigh wave phase velocity dispersion curves and performed quality control on the dispersion data. The direct surface wave tomography method was used to invert all phase velocity dispersion data for the 3-D shear-wave velocity model in the crust and uppermost mantle. Our results show velocity segmentations with high-velocity structures existing beneath orogenic belts and uplifts within the first 10 km depths which correspond to the High-Pressure/Ultra-High Pressure Metamorphic rocks in the area. The existence of high-velocity structures beneath orogenic belts at shallow depths implies that the exhumation of eclogites is confined to the uppermost crust. Generally, fault zones in this area are characterized by a low velocity from 0 to 5 km and relatively high velocity in the lower part of the upper crust and the middle crust. The spatial distribution of earthquakes along Tanlu Fault reveals two seismicity zones: the southern segment and the Suqian-Tancheng segment with a low-velocity transitional zone at Suqian, which suggests that the two segments respond differently to stresses. Regions of dense earthquake distribution correspond to the transition zones of high to low shear-wave velocities, which could be as a result of instability in the upper mantle and variation in compositions of crustal materials. Unlabelled Image • High and low velocities are delineated in the upper crust corresponding to the HP/UHPM rocks and basins, respectively. • Seismic velocity segmentation exists in the central-southern Tanlu fault zone in vertical and horizontal directions. • Two seismic zones exist in the central Tanlu fault: the southern and the Suqian-Tancheng segments, separated beneath Suqian. [ABSTRACT FROM AUTHOR]

This paper presents the pollution levels, variation characteristics, chemical reactivity, source apportionment and potential source regions of 102 volatile organic compounds (VOCs) observed from 2017.4.26 to 2017.6.6 in urban Wuhan. The concentration of total VOCs (TVOCs) was 28.92 ± 20.10 ppbv, and the VOC composition was dominated by alkanes (51.14%). Propane, ethane and acetone were the most abundant VOC species. The results for the OH radical loss rate (L OH) and ozone formation potential (OFP) indicated that alkenes were responsible for much of the chemical reactivity and O 3 formation, accounting for 47.02% and 49.52%, respectively, and the dominant VOC species were mainly associated with anthropogenic sources, such as vehicle emissions, the use of natural gas (NG) and liquefied petroleum gas (LPG), solvent usage and fuel evaporation. Ambient ratio data showed that VOCs were greatly affected by the pollution sources (such as emissions of NG and LPG, liquid gasoline and fuel evaporation sources, vehicle exhaust emissions, and biogenic sources), photochemical reaction processes and regional transport. Industrial sources (11.84%), industrial sources + coal burning (13.09%), LPG/NG usage + solvent usage in painting/coating (37.28%), fuel evaporation (12.04%), vehicle exhaust (13.65%), biogenic sources (5.95%) and biomass burning (6.15%) were determined by positive matrix factorization (PMF). Furthermore, LPG/NG usage, solvent usage in painting/coating and vehicle exhaust were the most important VOC sources, and their various contributions were affected by a combination of factors, including the emission strength of pollution sources, meteorological conditions and photochemical reaction processes. Backward trajectory analysis showed that VOC pollution was mainly derived from the south via short-distance transport. The potential source contribution function (PSCF) results indicated that the main sources affecting VOC pollution were the potential sources to the south and local sources within the city. This study provides evidence for local governments to formulate VOC control strategies during the transition from spring to summer. Image 1 • Alkenes were the key components of chemical reactivity and O 3 formation. • The effects of sources, photochemical reactions and air mass on VOCs were analysed. • LPG/NG usage, solvent usage in painting/coating and vehicle exhaust were important. • Potential sources from the south and local sources within the city were important. [ABSTRACT FROM AUTHOR]

In this study, a 3-D S-wave velocity model of the lithosphere in mainland China down to 150 km depth was determined from ambient noise data. First, we collected 2-year continuous waveforms recorded by 1031 broadband stations of the China Regional Seismic Network and NECESSArray. Then, by applying the procedures of noise cross-correlation and time-frequency domain phase-weighted stacking, we obtained the interstation empirical Green's functions of Rayleigh waves. We measured the group and phase velocity dispersions at periods of 5–125 s from the EGFs and inverted both group and phase velocities for the S-wave velocity model. Our model revealed that the lithospheric thickness in the northern Songliao basin is ~70–110 km. A weak high-velocity anomaly that is discontinuous in the vertical direction was detected beneath the southern Songliao basin, which may indicate that the lithosphere is delaminated in this area. The model also revealed that deep (>150 km) high-velocity lithospheric roots exist beneath the Ordos and Sichuan basins. The lithospheric thicknesses in eastern parts of the Northeast China Block, the North China Craton, and the South China Block are only 60–100 km, which may be the result of a series of deep processes caused by the subduction of the Pacific plate to the Eurasian plate that produced strong lithospheric thinning in eastern China. The lithospheric thickness within the Tanlu fault belt is generally thinner than that in the adjacent areas of the fault belt, and the S-wave velocity of the mantle lithosphere beneath the fault belt is also lower than that beneath the adjacent areas, indicating that the Tanlu fault belt is a deep fault belt cutting through the lithosphere. • Application of tf-pws increases the SNRs of CCFs and benefits long-period dispersion measurement. • A 3-D S-wave velocity model of the lithosphere in mainland China was determined. • Strong lithospheric thinning was observed in eastern China. • The Tanlu fault belt may be a deep fault belt cutting through the lithosphere. [ABSTRACT FROM AUTHOR]

In view of the water swelling of mudstone and the creep induction function of formations in the process of oilfield water injection, the casing incurs collapse deformation under local lateral load. In this study, according to the actual collapse deformation characteristics of the casing in the second section of the Qing formation of the Songliao Basin in China, the yield surfaces of the casing collapse deformation are considered as plane plastic areas (half rhombus) with symmetric parabola shaped boundaries, and a mechanical model for the local lateral collapse deformation of casing is presented based on the principle of virtual work. Four types of casing, 4½″J55, 5½″J55, 4½″N80 and 5½″N80, are selected as examples. The relation of the casing intensity, the absolute reduction of intensity and the relative reduction ratio of intensity change with casing wall thickness, yield stress, radial maximum deformation, and deformation length are calculated and analyzed. The results show that the casing intensity of the casing is reduced under local lateral load, which is lower than the design standard value of the American Petroleum Association specification (API SPEC) 5CT. The relative reduction ratio declines linearly with the wall thickness of the casing wall as the yield stress increases, and increases linearly with increasing maximum deformation. In addition, the local lateral bearing capacity of the casing reaches the minimum value when the plastic deformation length reaches the critical value or the deformation quantity is less than the critical value. The conclusions provide scientific guidance for preventing casing failure accidents caused by deformation. [ABSTRACT FROM AUTHOR]