This research investigates the ecological importance, changes, and status of mangrove wetlands along China’s coastline. Visual interpretation, geological surveys, and ISO clustering unsupervised classification methods are employed to interpret mangrove distribution from remote sensing images from 2021, utilizing ArcGIS software platform. Furthermore, the carbon storage capacity of mangrove wetlands is quantified using the carbon storage module of InVEST model. Results show that the mangrove wetlands in China covered an area of 278.85 km² in 2021, predominantly distributed in Hainan, Guangxi, Guangdong, Fujian, Zhejiang, Taiwan, Hong Kong, and Macao. The total carbon storage is assessed at 2.11×10⁶ t, with specific regional data provided. Trends since the 1950s reveal periods of increase, decrease, sharp decrease, and slight-steady increases in mangrove areas in China. An important finding is the predominant replacement of natural coastlines adjacent to mangrove wetlands by artificial ones, highlighting the need for creating suitable spaces for mangrove restoration. This study is poised to guide future mangrove-related investigations and conservation strategies.

The well-developed coal electricity generation and coal chemical industries have led to huge carbon dioxide (CO₂) emissions in the northeastern Ordos Basin. The geological storage of CO₂ in saline aquifers is an effective backup way to achieve carbon neutrality. In this case, the potential of saline aquifers for CO₂ storage serves as a critical basis for subsequent geological storage project. This study calculated the technical control capacities of CO₂ of the saline aquifers in the fifth member of the Shiqianfeng Formation (the Qian-5 member) based on the statistical analysis of the logging and the drilling and core data from more than 200 wells in the northeastern Ordos Basin, as well as the sedimentary facies, formation lithology, and saline aquifer development patterns of the Qian-5 member. The results show that (1) the reservoirs of saline aquifers in the Qian-5 member, which comprise distributary channel sand bodies of deltaic plains, feature low porosities and permeabilities; (2) The study area hosts three NNE-directed saline aquifer zones, where saline aquifers generally have a single-layer thickness of 3-8 m and a cumulative thickness of 8-24 m; (3) The saline aquifers of the Qian-5 member have a total technical control capacity of CO₂ of 119.25 × 10⁶ t. With the largest scale and the highest technical control capacity (accounting for 61% of the total technical control capacity), the Jinjie-Yulin saline aquifer zone is an important prospect area for the geological storage of CO₂ in the saline aquifers of the Qian-5 member in the study area.

The change processes and trends of shoreline and tidal flat forced by human activities are essential issues for the sustainability of coastal area, which is also of great significance for understanding coastal ecological environment changes and even global changes. Based on field measurements, combined with Linear Regression (LR) model and Inverse Distance Weighing (IDW) method, this paper presents detailed analysis on the change history and trend of the shoreline and tidal flat in Bohai Bay. The shoreline faces a high erosion chance under the action of natural factors, while the tidal flat faces a different erosion and deposition patterns in Bohai Bay due to the impact of human activities. The implication of change rule for ecological protection and recovery is also discussed. Measures should be taken to protect the coastal ecological environment. The models used in this paper show a high correlation coefficient between observed and modeling data, which means that this method can be used to predict the changing trend of shoreline and tidal flat. The research results of present study can provide scientific supports for future coastal protection and management.

Many locations with concentrated hydrates at vents have confirmed the presence of abundant thermogenic gas in the middle of the Qiongdongnan Basin (QDNB). However, the impact of deep structures on gas-bearing fluids migration and gas hydrates distribution in tectonically inactive regions is still unclear. In this study, the authors apply high-resolution 3D seismic and logging while drilling (LWD) data from the middle of the QDNB to investigate the influence of deep-large faults on gas chimneys and preferred gas-escape pipes. The findings reveal the following: (1) Two significant deep-large faults, F1 and F2, developed on the edge of the Songnan Low Uplift, control the dominant migration of thermogenic hydrocarbons and determine the initial locations of gas chimneys. (2) The formation of gas chimneys is likely related to fault activation and reactivation. Gas chimney 1 is primarily arises from convergent fluid migration resulting from the intersection of the two faults, while the gas chimney 2 benefits from a steeper fault plane and shorter migration distance of fault F2. (3) Most gas-escape pipes are situated near the apex of the two faults. Their reactivations facilitate free gas flow into the GHSZ and contribute to the formation of fracture - filling hydrates.

The Daqing exploration area in the northern Songliao Basin has great potential for unconventional oil and gas resources, among which the total resources of tight oil alone exceed 10⁹ t and is regarded as an important resource base of Daqing oilfield. After years of exploration in the Qijia area, Songliao Basin, NE China, tight oil has been found in the Upper Cretaceous Qingshankou Formation. To work out tight oil’s geological characteristics, taking tight oil in Gaotaizi oil layers of the Upper Cretaceous Qingshankou Formation in northern Songliao Basin as an example, this paper systematically analyzed the geological characteristics of unconventional tight oil in Gao3 and Gao4 layers of the Qijia area, based on the data of the geological survey, well drilling journey, well logging, and test. It is that three sets of hydrocarbon source rocks (K₂qn₁, K₂qn₂₊₃, and K₂n₁) develop in the examined area, and exhibit excellent type I and II kerogens, high organic matter abundance, and moderate maturity. The reservoir is generally composed of thin-bedded mudstone, siltstone, and sandstone, and presents poor porosity (average 8.5 vol.%) and air permeability (average 4 mD). The main reservoir space primarily includes intergranular pores, secondary soluble pores, and intergranular soluble pores. Three types of orifice throats were identified, namely fine throat, extra-fine throat, and micro-fine throat. The siltstone is generally oil-bearing, the reservoirs with slime and calcium become worse oil-bearing, and the mudstone has no obvious oil-bearing characteristics. The brittleness indices of the sandstone in the tight oil reservoir range from 40% to 60%, and those of the mudstone range from 40% to 45%, indicating a better brittleness of the tight oil reservoir. Based on the study of typical core hole data, this paper gives a comprehensive evaluation of the properties of the tight oil and establishes a tight oil single well composite bar chart as well as the initial evaluation system with the core of properties in the tight oil reservoir. This study has theoretical guiding significance and practical application value for tight oil exploration and evaluation in the Qijia area.

The detailed description of two granite complexes in the Olkhon subterrane is given. The Early Paleozoic Sharanur complex was formed by granitization of gneisses of the Olkhon series. It includes migmatites, granite-gneisses, granites and pegmatites of normal alkalinity; they belong to the type of syncollisional granites. The Middle Paleozoic Aya granite complex includes mother Aya massif of amazonite-bearing granites and several types of rare-metal pegmatites. They have elevated alkalinity, low of Ba, Sr, and high LILE and HFSE elements contents. The Aya pegmatites lie in northwest cracks of stretching and associated with the rise of the territory under the influence of the North Asian plume. These cracks and pegmatites mark the beginning of a new intraplate geodynamic setting. Two geochemical types are distinguished among the pegmatites of this complex. These are amazonite pegmatites of Li-F type with Ta mineralization and complex type pegmatite with Be-Rb-Nb-Ta and Li-F mineralization (the Ilixin vein). The Tashkiney pegmatite vein is similar to Ilixin, but lies in the gneisses of the Olkhon series. It shows high concentrations of Be, Nb, Ta, as well as W, Sn, but lacks Li and F, due to a greater depth and higher temperature of the melt crystallization of this pegmatite.

Two suites of mafic dykes, T1193-A and T1194-A, outcrop in Gyangze area, southeast Tibet. They are in the area of Comei LIP and have indistinguishable field occurrences with two other dykes in Gyangze, T0902 dyke with 137.7±1.3 Ma zircon age and T0907 dyke with 142±1.4 Ma zircon age reported by Wang YY et al. (2016), indicating coeval formation time. Taking all the four diabase dykes into consideration, two different types, OIB-type and weak enriched-type, can be summarized. The “OIB-type” samples, including T1193-A and T0907 dykes, show OIB-like geochemical features and have initial Sr-Nd isotopic values similar with most mafic products in Comei Large Igneous Provinces (LIP), suggesting that they represent melts directly generated from the Kerguelen mantle plume. The “weak enriched-type ” samples, including T1194-A and T0902 dykes, have REEs and trace element patterns showing within-plate affinity but have obvious Nb-Ta-Ti negative anomalies. They show uniform lower ε_Nd(t) values (-6--2) and higher ⁸⁷Sr/⁸⁶Sr(t) values (0.706-0.709) independent of their MgO variation, indicating one enriched mantle source. Considering their closely spatial and temporal relationship with the widespread Comei LIP magmatic products in Tethyan Himalaya, these “weak enriched-type” samples are consistent with mixing of melts from mantle plume and the above ancient Tethyan Himalaya subcontinental lithospheric mantle (SCLM) in different proportions. These weak enriched mafic rocks in Comei LIP form one special rock group and most likely suggest large scale hot mantle plume-continental lithosphere interaction. This process may lead to strong modification of the Tethyan Himalaya lithosphere in the Early Cretaceous.

The Xianshuihe-Anninghe fault extends SE-S and constitutes the southeastern margin of the Tibetan Plateau. However, the Dadu River which is associated with the fault does not flow following the path, but makes a 90° turn within a distance of 1 km at Shimian, heading east, and joins the Yangtze River, finally flowing into the East China Sea. Adjacent to the abrupt turn, a low and wide pass near the Daqiao reservoir at Mianning separates the N-S course of the Dadu River from the headwater of the Anning River which then flows south into the Yunnan Province along the Anninghe fault. Therefore, many previous studies assumed southward flow of the paleo-Dadu River from the Shimian to the Anning River. However, evidences for the capture of the integrated N-S paleo-Dadu-Anning River, its timing, and causes are still insufficient. This study explored the paleo-drainage pattern of the Dadu and Anning Rivers based on bulk mineral and geochemical analyses of the large quantities of fluvial/lacustrine sediments along the trunk of the Dadu and Anning Rivers. Similar with sands in the modern Dadu River, the Xigeda sediments also exhibit a granitoid affinity with the bulk major mineral compositions of quartz (>50%), anorthite (about 10%), orthoclase (about 5%), muscovite (about 5%), and clinochlore (about 4%). Correspondingly, bulk major elements show high SiO₂, with all samples >60%, and some of them >70%, low TiO₂ (⩽0.75%), P₂O₅ (⩽0.55%), FeO* (⩽5%), and relatively high CaO (1.02%-8.51%), Na₂O (1.60%-2.52%), and K₂O (2.17%-2.71%), with a uniform REE patterns. Therefore, synthesizing all these results indicate that these lacustrine sediments have similar material sources, which are mainly derived from its course in the Songpan-Ganzi flysch block, implying that the paleo-Dadu originally flowed southward into the Anning River and provided materials to the Xigeda ancient lake. The rearrangement of the paleo-Dadu River appears to be closely related to the locally focused uplift driven by strong activities of the Xianshuihe-Xiaojiang fault system.

Machine learning is currently one of the research hotspots in the field of landslide prediction. To clarify and evaluate the differences in characteristics and prediction effects of different machine learning models, Conghua District, which is the most prone to landslide disasters in Guangzhou, was selected for landslide susceptibility evaluation. The evaluation factors were selected by using correlation analysis and variance expansion factor method. Applying four machine learning methods namely Logistic Regression (LR), Random Forest (RF), Support Vector Machines (SVM), and Extreme Gradient Boosting (XGB), landslide models were constructed. Comparative analysis and evaluation of the model were conducted through statistical indices and receiver operating characteristic (ROC) curves. The results showed that LR, RF, SVM, and XGB models have good predictive performance for landslide susceptibility, with the area under curve (AUC) values of 0.752, 0.965, 0.996, and 0.998, respectively. XGB model had the highest predictive ability, followed by RF model, SVM model, and LR model. The frequency ratio (FR) accuracy of LR, RF, SVM, and XGB models was 0.775, 0.842, 0.759, and 0.822, respectively. RF and XGB models were superior to LR and SVM models, indicating that the integrated algorithm has better predictive ability than a single classification algorithm in regional landslide classification problems.

The continuous enrichment of heavy metals in soils has caused potential harm to groundwater. Quantitative methods to evaluate the harm of heavy metals in soil to groundwater are lacked in previous studies. Based on the theory of groundwater circulation and solid-liquid equilibrium, a simple and easy-to-use flux model of soil heavy metals migrating to groundwater is constructed. Based on groundwater environmental capacity, an innovative method for evaluating the harm of heavy metals in soil to groundwater is proposed, which has been applied in Hunchun Basin, Jilin Province, China. The results show that the fluxes of soil heavy metals into groundwater in the study area are Zn, Cu, As, Pb, Cd, Ni, and Hg in descending order. The content of heavy metals in groundwater (As, Hg, Cu, Pb, Zn, Ni, and Cd) in most areas has not risen to the threshold of environmental capacity within 10 years. The harm levels of soil heavy metals to groundwater in the most townships soils are at the moderate level or below. This evaluation method can quantify the flux of soil heavy metals into groundwater simply and quickly, determine the residual capacity of groundwater to heavy metals, evaluate the harm level of soil heavy metals to groundwater, provide support for relevant departments to carry out environmental protection of soil and groundwater, and provide a reference to carry out similar studies for related scholars.

Groundwater is an important source of drinking water. Groundwater pollution severely endangers drinking water safety and sustainable social development. In the case of groundwater pollution, the top priority is to identify pollution sources, and accurate information on pollution sources is the premise of efficient remediation. Then, an appropriate pollution remediation scheme should be developed according to information on pollution sources, site conditions, and economic costs. The methods for identifying pollution sources mainly include geophysical exploration, geochemistry, isotopic tracing, and numerical modeling. Among these identification methods, only the numerical modeling can recognize various information on pollution sources, while other methods can only identify a certain aspect of pollution sources. The remediation technologies of groundwater can be divided into in-situ and ex-situ remediation technologies according to the remediation location. The in-situ remediation technologies enjoy low costs and a wide remediation range, but their remediation performance is prone to be affected by environmental conditions and cause secondary pollution. The ex-situ remediation technologies boast high remediation efficiency, high processing capacity, and high treatment concentration but suffer high costs. Different methods for pollution source identification and remediation technologies are applicable to different conditions. To achieve the expected identification and remediation results, it is feasible to combine several methods and technologies according to the actual hydrogeological conditions of contaminated sites and the nature of pollutants. Additionally, detailed knowledge about the hydrogeological conditions and stratigraphic structure of the contaminated site is the basis of all work regardless of the adopted identification methods or remediation technologies.

China is home to shales of three facies: Marine shale, continental shale, and marine-continental transitional shale. Different types of shale gas are associated with significantly different formation conditions and major controlling factors. This study compared the geological characteristics of various shales and analyzed the influences of different parameters on the formation and accumulation of shale gas. In general, shales in China’s several regions exhibit high total organic carbon (TOC) contents, which lays a sound material basis for shale gas generation. Marine strata generally show high degrees of thermal evolution. In contrast, continental shales manifest low degrees of thermal evolution, necessitating focusing on areas with relatively high degrees of thermal evolution in the process of shale gas surveys for these shales. The shales of the Wufeng and Silurian formations constitute the most favorable shale gas reservoirs since they exhibit the highest porosity among the three types of shales. These shales are followed by those in the Niutitang and Longtan formations. In contrast, the shales of the Doushantuo, Yanchang, and Qingshankou formations manifest low porosities. Furthermore, the shales of the Wufeng and Longmaxi formations exhibit high brittle mineral contents. Despite a low siliceous mineral content, the shales of the Doushantuo Formation feature a high carbonate mineral content, which can increase the shales’ brittleness to some extent. For marine-continental transitional shales, where thin interbeds of tight sandstone with unequal thicknesses are generally found, it is recommended that fracturing combined with drainage of multiple sets of lithologic strata should be employed to enhance their shale gas production.