Display Mode： |
To illuminate the migration and transformation of selenium (Se) in the igneous rock-soil-rice system, 285 pairs of rhizosphere soil and rice samples were collected from the granitoid and basalt areas in Hainan Province, South China. The contents of Se in soils derived from granitoid and basalt are, respectively, 0.19±0.12 mg/kg and 0.34±0.39 mg/kg, which are much higher than Se contents in granitoid and basalt. Selenium shows remarkable enrichment from granitoid and basalt to soils. The mobile fraction of Se in soils derived from granitoid is 0.0100±0.0034 mg/kg, which is significantly higher than that of basalt (0.0058±0.0039 mg/kg). Although soil derived from basalt shows higher Se contents, Se contents in rice samples, mobile fractions of Se in soils, and biological concentration factor (BCF) is similar or even lower than that from granitoid. Basalt consist of calcic plagioclase and pyroxene, and are much richer in Fe, Al, and Ca than granitoid. Correspondingly, the basalt-derived soils have higher goethite, hematite, kaolinite, cation exchange capacity (CEC) content, and higher pH than the granitoid-derived soils, which result in higher adsorption capacity for Se and relatively lower Se bioavailability. Soils derived from granitoid and basalt in tropical regions are beneficial to produce Se-rich rice.
The estuary and coastal zone are the key areas for socio-economic development, and they are also the important channels for pollutants transported to the sea. The construction of the Jiaozhou Bay Bridge changed the hydrodynamic condition of the bay, which made the self-purification capacity of the bay weakened and the pollution in the estuary and adjacent coastal zone become more serious. In this study, 55 surface sediment samples were collected from the three seriously polluted estuaries and the adjacent coastal zone of Jiaozhou Bay to comprehensively study how the benthic foraminifera response to heavy metal pollution and human engineering, and to assess the ecological risks of the bay. A total of 80 species, belonging to 42 genera, were identified in this study. The results showed that Cu, Pb, Cr, Hg, Zn, and As had low to median ecological risks in the study area which would definitely affect the ecological system. The construction of the Jiaozhou Bay Bridge has resulted in pollutants accumulated at the river mouth of Loushan River, which has adverse effects on the survival and growth of benthic foraminifera. The lowest population density and diversity as well as the highest FAI (Foraminiferal Abnormality Index) and FMI (Foraminiferal Monitoring Index) occurred at Loushan River Estuary which indicated that the ecological environment of the northeastern part of Jiaozhou Bay (Loushan River Estuary) had been seriously damaged. Licun River and Haipo River estuaries and the adjacent coastal zone were slightly polluted and had low ecological risk. As a consequence, it suggested that the supervision of industrial and domestic waste discharge and the protection of the ecological environment in northeast Jiaozhou Bay should be paid more attention.
Due to the high heterogeneity and complexity of water flow movement for multiple karst water-bearing mediums, the evaluation, effective development, and utilization of karst water resources are significantly limited. Matrix flow is usually laminar, whereas conduit flow is usually turbulent. The driving mechanisms of water exchange that occur between the karst conduit and its adjacent matrix are not well understood. This paper investigates the hydrodynamic characteristics and the mechanism of flow exchange in dual water-bearing mediums (conduit and matrix) of karst aquifers through laboratory experimentation and numerical simulation. A karst aquifer consisting of a matrix network and a conduit was proposed, and the relationship between the water exchange flux and hydraulic head differences generated from the laboratory experiments was analyzed. Two modes of experimental tests were performed with different fixed water level boundaries in the laboratory karst aquifer. The results indicate that the water exchange capacity was proportional to the square root of hydraulic head differences. The linear exchange term in the conduit flow process (CFP) source program was modified according to experimental results. The modified CFP and the original CFP model experimental data results were compared, and it was found that the modified CFP model had better fitting effects. These results showed that the water exchange mechanism between conduit and matrix is very important for solid-liquid interface reaction, water resource evaluation, and understanding of karst hydrodynamic behavior.
The granite collected from the Yinshan Mountain and kaolinite has been selected for the leaching and adsorption experiment, respectively, aiming to clarify the enrichment processes of Li and Ga during the deposition. Results suggest both Li and Ga could be leached out from granite by using different acid solutions of different pH and kaolinite can adsorb Li and Ga with varying degrees. Lithium and Ga had the highest leaching ratio when pH = 1. Special geological events (e.g. volcanic eruptions and wildfires), which could result in very low pH values of water in peatland, may have accelerated the release of Li and Ga from the source rocks. Kaolinite has the highest adsorption fraction was obtained at pH = 8. The different characteristics of Li and Ga displayed in the leaching and adsorption experiments probably result from the different occurrences and enrichment processes of Li and Ga in the coals. Lithium was probably enriched before the Li carriers (e.g. kaolinite) had been transported into paleomires because of its high leaching ratio and high adsorption fraction under neutral and alkaline conditions, whereas Ga was more likely concentrated by kaolinite and other carriers after it had been transported into the peat mires.
The Hekoulinchang Sn-Pb-Zn-Ag polymetallic deposit (20000 t Sn at 0.27%, 236 t Ag at 122.89 g/t, 15000 t Pb at 0.84%, and 38000 t Zn at 1.43%) is located in the Wandashan Terrane of the easternmost segment of the Central Asian Orogenic Belt. The timing of Sn-Pb-Zn-Ag polymetallic mineralization remains unclear due to a lack of precise isotope dating directly conducted on ore minerals. The authors herein report that the LA-ICP-MS U-Pb ages of cassiterite and zircon from the granite porphyry in the Hekoulinchang Sn-Pb-Zn-Ag polymetallic deposit are 101.4±7.9 Ma and 115.4±1.0 Ma, respectively, indicating that Sn mineralization and magmatism occurred during the Early Cretaceous. The granite porphyry belongs to the subalkaline series peraluminous I-type granites that are depleted in Nb, Ta, and Ti and enriched in Rb, Th, U, and Pb. The εHf(t) values of the granite porphyry range from 0.9 to 7.4, with an average of about 5.6 and two-stage model ages (TDM2) of 705–1116 Ma, with an average age of 819 Ma. The εNd(t) values of the apatites are –1.60–0.45, with an average of –0.9, and two-stage model ages (TDM2) of 872–1040 Ma, with an average age of 983 Ma. The Nd-Hf isotope data indicate that the magma may have been derived from the partial melting of juvenile crustal material.
The 1∶1000000 geochemical mapping of Zambia provides catchment sediment geochemical data for 58 elements including Au from 746 sediment samples at 736 sampling sites, corresponding to a sampling density of about one site per 1000 km2. Under strict quality control using field duplicates, certified reference materials, and analytical replicate samples, the Au was determined by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The detection limit of Au was 0.20 × 10−9. The 95% range (2.5%–97.5%) of Au concentrations was from 0.24 × 10−9 to 1.36 × 10−9, and the median value was 0.40 × 10−9. The most noticeable Au distribution patterns shown on the map are mainly located between Lusaka and Ndola (Lufilian Arc Belt). In addition, several high Au value areas occurred in Mansa, Muyombe, Chipata, and Livingstone. The spatial distribution patterns of Au in tectonic units, drainage basins, and geomorphological landscapes could be related to the Lufilian Arc Belt and Bangweulu Block. The Au concentrations show metallogenic belts between Muyombe and Mbala areas, between Mansa and Ndola areas, and between Lusaka and Kasempa areas.
A method is proposed for the prospecting prediction of subsurface mineral deposits based on soil geochemistry data and a deep convolutional neural network model. This method uses three techniques (window offset, scaling, and rotation) to enhance the number of training data for the model. A window area is used to extract the spatial distribution characteristics of soil geochemistry and measure their correspondence with the occurrence of known subsurface deposits. Prospecting prediction is achieved by matching the characteristics of the window area of an unknown area with the relationships established in the known area. This method can efficiently predict mineral prospective areas where there are few ore deposits used for generating the training dataset, meaning that the deep-learning method can be effectively used for deposit prospecting prediction. Using soil active geochemical measurement data, this method was applied in the Daqiao area, Gansu Province, for which seven favorable gold prospecting target areas were predicted. The Daqiao orogenic gold deposit of latest Jurassic and Early Jurassic age in the southern domain has more than 105 t of gold resources at an average grade of 3‒4 g/t. In 2020, the project team drilled and verified the K prediction area, and found 66 m gold mineralized bodies. The new method should be applicable to prospecting prediction using conventional geochemical data in other areas.
Bangong-Nujiang collisional zone (BNCZ) is an older one in Qinghai-Tibet Plateau and resulted in the famous Bangong-Nujiang metallogenic belt, which plays an important role in evaluating the formation and uplift mechanism of plateau. The northern and central Lhasa Terrane composed the southern part of the BNCZ. Since ore deposits can be used as markers of geodynamic evolution, the authors carried 1∶50000 stream sedimental geochemical exploration in the Xiongmei area in the Northern Lhasa Terrane to manifest the mineralization, and based on this mineralization with geochemical and chronological characteristics of related magmatic rocks to constrain their geodynamics and connection with the evolution of the Lhasa Terrane. The authors find Early Cretaceous magma mainly resulted in Cu, Mo mineralization, Late Cretaceous magma mainly resulted in Cu, Mo, and W mineralization in the studying area. The results suggest a southward subduction, slab rolling back and break-off, and thickened lithosphere delamination successively occurred within the Northern Lhasa Terrane.
The Philippine Sea Plate is located at the convergence zone of the Eurasian Plate, the Pacific Plate, and the Indo-Australian Plate. This paper divides the Philippine Sea Plate into two second-order tectonic units and eight third-order tectonic units by summarizing the marine geological, geophysical, and submarine geomorphological data of the Philippine Sea Plate collected for years and referring to the seafloor spreading theory and the trench-arc-basin system. The two second-order tectonic units are the West Philippine Sea block and the Izu-Bonin-Mariana arc-basin system. The former includes the West Philippine Basin, the Huatung Basin, the Daito Basin, and the Palau Basin, while the latter consists of the Kyushu-Palau Ridge, the Shikoku-Parece Vela Basin, the Izu-Bonin Arc, and the Mariana Arc. Furthermore, this study concludes that the Philippine Sea Plate has undergone three stages of tectonic evolution, namely the early stage of the evolution of marginal basins with Cretaceous basement (Early Cretaceous), the middle stage of the spreading of the West Philippine Basin (Eocene), and the late stage of the subduction of the Izu-Bonin-Mariana arc-basin system (Oligocene-present). The Kyushu-Palau Ridge is a window to discover the tectonic evolution of the Philippine Sea Plate due to its unique geographical location.
The shale gas resources in China have great potential and the geological resources of shale gas is over 100 ×1012 m3, which includes about 20×1012 m3 of recoverable resources. Organic-rich shales can be divided into three types according to their sedimentary environments, namely marine, marine-continental transitional, and continental shales, which are distributed in 13 stratigraphic systems from the Mesoproterozoic to the Cenozoic. The Sichuan Basin and its surrounding areas have the highest geological resources of shale gas, and the commercial development of shale gas has been achieved in the Upper Ordovician Wufeng Formation-Lower Silurian Longmaxi Formation in these areas, with a shale gas production of up to 20×109 m3 in 2020. China has seen rapid shale gas exploration and development over the last five years, successively achieving breakthroughs and important findings in many areas and strata. The details are as follows. (1) Large-scale development of middle-shallow shale gas (burial depth: less than 3500 m) has been realized, with the productivity having rapidly increased; (2) breakthroughs have been constantly made in the development of deep shale gas (burial depth: 3500‒4500 m), and the ultra-deep shale gas (burial depth: greater than 4500 m) is under testing; (3) breakthroughs have been made in the development of normal-pressure shale gas, and the assessment of the shale gas in complex tectonic areas is being accelerated; (4) shale gas has been frequently discovered in new areas and new strata, exhibiting a great prospect. Based on the exploration and development practice, three aspects of consensus have been gradually reached on the research progress in the geological theories of shale gas achieved in China. (1) in terms of deep-water fine-grained sediments, organic-rich shales are the base for the formation of shale gas; (2) in terms of high-quality reservoirs, the development of micro-nano organic matter-hosted pores serves as the core of shale gas accumulation; (3) in terms of preservation conditions, weak structural transformation, a moderate degree of thermal evolution, and a high pressure coefficient are the key to shale gas enrichment. As a type of important low-carbon fossil energy, shale gas will play an increasingly important role in achieving the strategic goals of peak carbon dioxide emissions and carbon neutrality. Based on the in-depth study of shale gas geological conditions and current exploration progress, three important directions for shale gas exploration in China in the next five years are put forward.
The Tiegelongnan Cu (Au, Ag) deposit in central Tibet contains more than 10 Mt of copper ranking 29th in the world. It is characterized by typical porphyry-epithermal alteration and mineralization. In order to improve the understanding of porphyry-epithermal copper deposit in Tibet, new zircon U-Pb age and sulfur isotope data along with published data in the Tiegelongnan are presented to investigate the formation and preservation mechanism. Ore-related intrusive rocks in the Tiegelongnan including Early Cretaceous (about 120 Ma) granodiorite porphyry and diorite porphyry are closely related to the northward subduction of Bangongco-Nujiang ocean. Sulfur mainly comes from deep magma, and ore-forming fluid is affected by both magmatic and meteoric water. The metallogenic setting of Tiegelongnan is consistent with those of Andean porphyry copper deposits in South America. The cover of the Meiriqiecuo Formation volcanic rocks, Lhasa-Qiangtang collision and India-Eurasian collision have significance in the preservation and uplift of the deposit. The formation, preservation and discovery of Tiegelongnan play an important role in exploration of ancient porphyry-epithermal deposits in Tibet.
As a new type of pollutants in the marine environment, microplastics have attracted increasing attention from scientific researchers and environmental protection workers in China and abroad. However, for the microplastic pollution in sea areas in China, there are a very limited number of studies on its current status and few reviews of research on the microplastics. This paper reviews the surveys and researches of microplastics in the Bohai Sea, the Yellow Sea, the East China Sea, the South China Sea, and main estuaries in China carried out in recent years and proposes an outlook for future work, aiming to provide research suggestions and solutions for ecological protection against microplastic pollution in sea areas in China. Previous studies have shown that microplastics are widely distributed in water bodies and sediments in sea areas and major estuaries in China. The Pearl River Estuary, in the South China Sea suffers the most serious microplastic pollution, followed by the Bohai Sea. In contrast, the microplastic pollution in the Yellow Sea and the East China Sea is comparatively slight. Microplastics in sea areas in China are mainly fibrous and are concentrated in offshore areas with developed industry and a dense population (especially around estuaries and bays). In addition, they are widely affected by human activities, such as shipping, aquaculture, industry, and sewage discharge. Here the authors suggest unifying measurement units and research methods and developing related standard systems to carry out researches related to microplastics. Furthermore, this paper also suggests further deepening researches on both the source-sink process of microplastics and nanoscale microplastics while enhancing the development and implementation of related policies, aiming to promote researches and control of microplastics in sea areas in China.
Microplastic pollution has become an environmental issue of great concern owing to the persistence of microplastics and their potential adverse effects on biota. The Yangtze River is the longest river in China and the third-longest river in the world, and the microplastics in this river will affect the health of a large population living along with it. To ensure the survival safety of people, it is essential to plan ahead and investigate in advance in order to understand the microplastic pollution in the river and work out countermeasures. This paper reviews the literature concerning the microplastic pollution in the Yangtze River basin and analyzes the abundance, shapes, colors, and composition of microplastics in the water bodies and sediments in the trunk stream and main lakes of the Yangtze River. The results are as follows. Compared to other river basins in China and abroad, the microplastics in the Yangtze River basin have a moderate abundance and high spatial heterogeneity. Owing to the barrier effect of the Three Gorges Dam on microplastics, the abundance of microplastics in the Three Gorges Reservoir is generally an order of magnitude higher than that in other sections of the river. Most microplastics in the water bodies and sediments are less than 1 mm in size and are transparent and colorful. In terms of shapes, they are dominated by fibers, followed by fragments and films. In terms of composition, the microplastics in the source region of the Yangtze River are mainly composed of nylon and polyethylene, while the microplastics in the surface water from the lower reaches of the Jinsha River to the Yangtze River estuary are dominated by polypropylene and polyethylene. The microplastics are primarily derived from the secondary microplastics in the environment, and relatively intensive human activities increase the abundance of microplastics. These results serve as bases for understanding and preventing microplastic pollution in the Yangtze River.