Table of Content

20 October 2024, Volume 30 Issue 05

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Macroscopic and Spectroscopic Study on Phosphate Adsorption by Ce-Al Oxide

NIE Hongda, REN Chao, LI Wei

2024, 30(05):  505-513.  DOI: 10.16108/j.issn1006-7493.2023046

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Eutrophication caused by excess phosphate in water bodies is an important issue in China and many countries (regions) around the world. Therefore, it is crucial to investigate the environmental geochemical behavior of phosphate and to explore phosphorus removal techniques and principles. In this study, a Ce-Al oxide was synthesized as the adsorbent material to investigate the adsorption behavior and mechanism of orthophosphate. The effects of system parameters such as reaction time, initial phosphate concentration, pH and ionic strength on the phosphate adsorption by the Ce-Al oxide were examined. The results showed that the phosphate adsorption reached equilibrium within 24 hours; the adsorption isotherm (pH=7) was best fitted by Langmuir adsorption mode, yielding a maximum adsorption amount of 75.5 mg·g-1; and importantly the adsorption was insensitive to pH and maintained a high efficiency in the studied pH range (i.e. pH=3-10). This study further employed zeta potential measurement, microscopic analyses (SEM and TEM) and spectroscopic methods (XRD and XPS) to investigate the phosphate adsorption mechanisms by the Ce-Al oxide. It can be concluded that surface precipitation and inner-sphere adsorption dominates the phosphate adsorption mechanisms by the Ce-Al oxide. The study demonstrates that the Ce-Al oxide is a candidate material for phosphate removal.

Coupling Relationship Between Dolomite and Fluorine in the Soil of Tiemenguan, Xinjiang

SHEN Ze, HE Junling, DUAN Xingxing, ZHU Xiaoyu, WANG Ruoshui, JI Junfeng, LIU Lianwen

2024, 30(05):  514-525.  DOI: 10.16108/j.issn1006-7493.2023048

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The oasis soil around the Tarim Basin in southern Xinjiang has developed a large amount of carbonate minerals, meanwhile the regional fluorine content in soil and groundwater is high, which poses a huge risk of fluorine pollution. Exploring the coupling relationship between the two is significant for comprehensive utilization of soil inorganic carbon sinks in arid regions and improving the prevention and control of regional fluoride pollution. This study sampled 15 typical surface soils from Tiemenguan, Xinjiang, and conducted a systematic study on the mineralogical and geochemical characteristics of the samples, using XRD, scanning electron microscopy, and other instrumental analysis methods. With the major and trace element content as well as carbonate Sr isotope compositions analyzed, combined with indoor selective dissolution experiments, geological evidence for the coupling mechanism of fluoride and carbonate minerals were obtained. Our study found that the mineral composition of the soil from Tiemenguan is relatively complex, with the major element content similar to that of the upper continental crust (UCC) and the chemical weathering index (CIA) value between 50 and 60 which indicates a relatively weak weathering. The soil contains a relatively large portion of carbonate minerals such as calcite and dolomite, with average Sr and Mn contents of 1434 ppm and 1736 ppm, respectively, and a 87Sr/86Sr ratio of 0.710. Fluorine in soil is highly correlated with elements related to carbonate minerals, and exhibits a good coupling relationship with dolomite. It is speculated that the fluorine anomaly in the soil mainly comes from the magnesium fluorite in the source area, which is subject to combined migration with dolomite due to geological and climatic factors.

Modification of Pretreatment Method of Phosphate Oxygen Isotope Analysis in Phosphorus-poor, Silicon-rich Freshwater System

WU Kedi, WEI Haizhen, RUAN Xiaohong

2024, 30(05):  526-540.  DOI: 10.16108/j.issn1006-7493.2023047

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Phosphorus is the limiting element of the trophic states for most freshwater systems. Therefore, the identification of the
main phosphorus sources is essential to the efficient control of phosphorus pollution as well as the prevention of eutrophication. Phosphate oxygen isotope (δ¹⁸OP) is proved to be effective in source identification. However, freshwater habitats are always of low phosphorus concentrations and complex compositions. For example, water bodies in silicate rocks exposed areas can be characterized by having little phosphorus while abundant silica. The later can easily precipitate and adsorb PO₄^3-, making it difficult to obtain valid δ¹⁸OP through existing methods. In this study, the widely used Mclaughlin pretreatment method was modified to deal with the phosphorus-poor, silicon-rich water, the phosphorus-poor sandy sediments and soils. The efficient enrichment and purification of PO₄^3- in freshwater are achieved with the following improvements: (i) reduction in the proportion of reagents added at the PO₄^3- enrichment step; (ii) graded pH adjustment prior to CePO₄ precipitation; (iii) multiple steps of fine pore membrane filtration to reduce the silica content; (iv) dynamic ion-exchange to remove cations. For phosphorus-poor sandy sediments and soils, an increase of the sample amount and the concentration of the extraction solutions, combined with the purification steps of water samples have been used to precipitate sufficient pure Ag₃PO₄ for δ¹⁸OP determination. The phosphate recovery of significant procedures relating to precipitation or cation are above 80%, and the precision is ±0.6‰ . The analytical accuracy was evaluated by comparing the δ¹⁸O_P of Ag₃PO₄ generated with the modified methods and the pure phosphate solution directly. The modified methods have been applied to the δ¹⁸O_P determination of samples from Danjiangkou Reservoir basin, providing technical support for tracing phosphorus in this basin.

Zircon Geochronology, Geochemical Characteristics and Geological Significance of Meta-Sedimentary Rocks in the Yingyangguan Group, Eastern Guangxi

LAN Yuanchun, SHI Yu, TANG Yuanyuan, ZHOU Yuxi, WENG Boyin

2024, 30(05):  541-558.  DOI: 10.16108/j.issn1006-7493.2023057

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This study presents new geochemical, zircon U-Pb and Lu-Hf isotopic data for the Neoproterozoic meta-sedimentary rocks of the Yingyangguan Group in eastern Guangxi. Geochemical data show that the meta-sedimentary rocks of the Yingyangguan Group have moderate composition maturity and weathering extent, and their rare earth element (REE) patterns are similar to that of the Post-Archaean Australian Shale (PAAS), with moderate Eu negative anomalies. The trace element distributions diagram shows that some samples are depleted in U, with higher Co and Ni contents compared with those of the meta-sedimentary rocks in the Nanling range, suggesting that the provenance was mostly intermediate to mafic rocks. The matrix of the Yingyangguan tectonic mélange contains a component of meta-sedimentary rocks. The detrital zircon U-Pb dating results give a maximum depositional age (660 Ma) of the matrix part of the tectonic mélange. Combined with previous results, we suggest that the Yingyangguan tectonic mélange was formed in the Middle-Late Neoproterozoic, and resulted from reworking by the Early Mesozoic thermal events. Provenance analysis reveals that the Neoproterozoic meta-edimentary rocks of the Yingyangguan Group are mainly of felsic components, combined with zircon cathodoluminescence image characteristics, zircon U-Pb geochronological characteristics, Hf model age of the second stage (TDM2) and relevant regional geological data, we suggest that the intermediate to mafic provenance in the meta-sedimentary rocks mainly originated from the Yingyangguan area or the adjacent terranes, suggesting a close affinity of the Yingyangguan Group with the Cathaysia Block. Combined with the characteristics of regional tectonic evolution, it is inferred that the Neoproterozoic meta-sedimentary rocks of the Yingyangguan Group were deposited in a post-orogenic extension rift basin.

Petrogenesis of the Biotite Quartz Monzonite from Shangshuiqiao Fluorite Deposit, North Wuyi Area: Constraints from Geochronology and Geochemistry

ZENG Xianghui, MENG Delei, ZENG Runling, JIANG Qibao, OUYANG Yongpeng

2024, 30(05):  559-576.  DOI: 10.16108/j.issn1006-7493.2024040

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Shangshuiqiao fluorite ore is a newly discovered medium fluorite deposit with great exploitation prospect in northern Wuyi area in recent years. However, little research has been carried out on this deposit. In this paper, petrographic, zircon U-Pb chronological and whole-rock geochemical analyses have been carried out on the biotite quartz monzonite from the the Shangshuiqiao fluorite deposit. The zircon LA-ICP-MS U-Pb ages show that the biotite quartz monzonite was formed at  235~236 Ma, which is the product of Indosinian magmatism. According to the geochemical analyses, the biotite quartz monzonite samples are characterized by high alkali (Na2O+K2O), Mg and Fe contents and low P and Ti contents. They have high σ values (2.59 and 3.61) and low A/CNK ratios (0.96 to 1.16), belonging to the typical high-K series with metaluminous to weakly peraluminous. In terms of trace and rare earth elements, the biotite quartz monzonite is enriched in Rb, Th, U, K and light rare earth elements (LREEs), but depleted in Ba, Sr, Nd, Ta, P, Ti and heavy rare earth elements (HREEs), as well as high rare earth elements (ΣREE varying from 356×10-6 to 448×10-6) and weak negative Eu anomalies (Eu/Eu* between 0.61 and 0.76). Besides, the biotite quartz monzonite displays high Zr+Nb+Ce+Y content (varying from 381×10-6 to 546×10-6) and Ga/Al ratio (104×Ga/Al between 2.60 and 3.07), with lower Rb/Sr (0.31 to 0.82), Rb/Ba (0.11 to 0.18) and TFeO/MgO ratios (2.02 to 2.22), belong to post-orogenic (PA type) aluminous A-type granites. In addition, based on the results of geochemical mapping and characteristics of regional magmatism and sedimentation, we suggest that the biotite quartz monzonite from Shangshuiqiao fluorite deposit may be formed in the postorogenic extensional tectonic environment at the end of intracontinental orogeny under the background of multi-plate convergence. During the mineralization stage, the biotite hydrolysis and sericitization of plagioclase in biotite quartz monzonite may provide F and Ca sources for fluorite mineralization.

Characterizing the Infiltration Process of MICP Treated Sand Soil Using Electrical Resistivity Tomography

LAN Runyang, LIN Kai, TANG Chaosheng, ZHANG Junzheng, SHI Bin

2024, 30(05):  577-584.  DOI: 10.16108/j.issn1006-7493.2023040

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Microbial induced calcium carbonate precipitation (MICP) is an environmentally friendly and promising technique for ground improvement. However, the treating process is closely related to the infiltration characteristics of the slurry Therefore, a monitoring method applying electrical resistivity tomography (ERT) technique to MICP slurry infiltration process is proposed. MICP treatment was performed on the quartz sand by one-step mixed-grouting method. ERT monitoring and conductivity analysis were performed during the process. The three-dimensional resistivity variation of sand samples was obtained. After the treatment, the distribution of calcium carbonate content was determined. The results indicates that: (1) The electrical resistivity increased when the urea generally hydrolyzed during the MICP reaction. (2) The distribution of low electrical resistivity area was mainly dominated by the diffusion and mixing process of the grouting fluid. (3) During the MICP treatment, carbonate precipitation and infiltration of grouting fluid interacted, jointly affecting the reinforcement effect. (4) The resistivity spatiotemporal evolution can be effectively traced by ERT, which could accurately reflect the infiltration of treating suspension and then evaluate the reinforcement effect. This experiment demonstrates the permeability of ERT applying on MICP reinforcing, provides new ideas and research direction on MICP application. 

Parameter Sensitivity Analysis of Landscape Evolution Models: An Example from the Kumarak River Basin

WU Qihui, ZENG Xiankui, WU Jichun

2024, 30(05):  585-592.  DOI: 10.16108/j.issn1006-7493.2023049

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Landscape evolution model is the basis for quantitative research on landscape evolution, but it involves complex processes and numerous model parameters. In order to alleviate the difficulty of parameter identification and improve the reliability of model parameter setting, identifying the key driving mechanisms and parameters of the landscape evolution model has become the focus of current research. In this study, the Kumarak River Basin in the Tarim River Basin of Xinjiang was selected as the study area, and the landscape evolution model of the study area was established based on the LE-PIHM (Landscape Evolution-Penn State Integrated Hydrologic Model). The parameter sensitivities of the LE-PIHM model were identified by the global sensitivity analysis method, Sobol method. The surface elevation of three typical landforms in the study area was used as the objective function for the sensitivity analysis, and the results showed that the key model parameters for the landscape evolution of the mountainous areas in the study area were the weathering rate of bare bedrock (P0), the fitting coefficient for bedrock weathering equation (α) and the rate of tectonic uplift (U), which were mainly related to the weathering effect of the bedrock and the tectonic uplift effect. Meanwhile, in the plain area of the study area, the model parameters have high sensitivity except for aquifer porosity (ng), and the elevation change in the plain area is mainly controlled by the interaction between the parameters. In the riverine area of the study area, the sensitivity of the model parameters is similar to that in the plain area, but the soil porosity (ns) and aquifer horizontal hydraulic conductivity (KHg) have significantly stronger sensitivities, which are related to surface watergroundwater interactions and aquifer permeability properties, respectively.

Experimental Study on Seepage and Heat Transfer of A Single Fracture in Sandstone during Shallow Geothermal Extraction

WU Hongtao, WANG Huimin, ZHENG Huifeng, SHENG Jinchang, HUANG Tairen, TIAN Jiali, SHENG Danna

2024, 30(05):  593-602.  DOI: 10.16108/j.issn1006-7493.2023056

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The development and utilization of shallow geothermal energy is related to the successful achievement of the “doublecarbon” target. The study on seepage and heat transfer characteristics of the rock fracture in the target reservoir is critical to the effectiveness of the groundwater source heat pump system. However, most of the previous studies on seepage and heat transfer in fractures considers a single factor such as rough surface, flow velocity, confining pressure, temperature for the evaluation of its heat transfer efficiency. The understanding of the evolution mechanism of seepage and heat transfer and its contribution degree by the change of shallow geothermal reservoir (confining pressure and rock temperature) at multiple flow rates have not been systematically investigated. Therefore, based on a self-developed seepage and heat transfer system of fractured rocks, this paper carried out the seepage and heat transfer test under multiple flow rates for sandstone with a single fracture. Subsequently, the evolution characteristics of single fracture seepage and heat transfer under multiple flow rates were analyzed. Finally, the influenced mechanism and contribution degree of sensitive parameters (confining pressure and rock temperature) in shallow geothermal on seepage and heat transfer were discussed. The test results show that: (1) The trends of outlet water temperature and convective heat transfer coefficient with the increase of water flow rate have obvious transition stages. (2) The increase of confining pressure leads to the fracture closing and the thinning of flow boundary layer, while the increase of temperature gradient causes a higher outlet water temperature and convective heat transfer coefficient due to the increase of heat flux density. (3) The contribution of rock temperature is significantly higher than that of confining pressure. Especially when the temperature increases from 60 ℃ to 70 ℃ , the convective heat transfer coefficient increases dramatically.

Application of Fractal Characteristics of Drill Hole Karst Geology in Analyzing the Degree of Karst Development

TAN Yao, QI Jihong, XU Mo, ZHENG Tongxin, WANG Zhongyu, WANG Shuai

2024, 30(05):  603-612.  DOI: 10.16108/j.issn1006-7493.2023052

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The existing analysis of the degree of karst development is mainly based on the general understanding of regional scale, but under the influence of topography, landform, groundwater runoff and other factors. The degree of karst development in the same geological unit varies and the regional general understanding of karst development often cannot meet the requirements of site-scale karst development degree analysis. A drill hole data is an important source for studying karst development characteristics at the engineering site. But various factors such as the core recovery rate and the large long steep dip-vertical karst fractures can influence the estimates for the karst development degree using the traditional karst statistical methods. By collecting drill holes data within the scope of the project and using the karst fractal theory, this paper combined the borehole image recognition system and the graphic fractal calculation program to determine the karst development degree discriminant index (IKAF), and proposed a site-scale, high-precision karst development degree identification method. The drill hole data of a reservoir site in the left bank mountainous area of the middle and upper reaches of the Shiting River basin in Mianzhu were analyzed using this method. The results show that this method can quickly and accurately identify the morphology of karst development in the drilling hole, reducing errors in determining the karst rate caused by the development of long and steep to vertical karst fractures. The degree of karst development obtained using this method is basically consistent with the degree of karst development reflected by the karst phenomena such as sinkholes and karst caves obtained from field investigations. This method is a beneficial addition to the traditional method in analyzing the degree of karst development. 

Protective Measures for Subway Tunnels Adjacent to Foundation Pit Engineering in Water-rich and Soft Deposits

LI Yuxiang, ZHANG Jie, YAN Songhong, LIU Nianwu, SHEN Xiaowei

2024, 30(05):  613-621.  DOI: 10.16108/j.issn1006-7493.2023045

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Construction in water-rich and soft soil areas usually faces dual problems of susceptible for disturbance and confined water. The Hexi area in Nanjing is a typical water-rich and soft soil area. In recent years, the development intensity has been relatively high and the area along the subway tunnel is the first choice for geotechnical engineering. However, this is often faced with the characteristics of deep, large and close foundation pits. Determining reliable subway tunnel protection measures has become an issue that needs urgent research. This article addeses this issue by taking the third phase of Nanjing Zixin Zhonghua Square as an example. Protection measures such as increasing support stiffness, soil reinforcement, and isolation piles are used to reduce the impacts of foundation pit excavation on adjacent tunnels. In the meantime, MADIS software is used to analyze the importance of relevant protection measures. The nature and necessity are verified by combining with the subway tunnel monitoring data to provide a reference for formulating protective measures for the impacts of foundation pit construction in water-rich and soft soil layers on adjacent subway tunnels.

Sedimentary Environment and Organic Matter Enrichment Mechanism of the Yuertusi Formation Source Rocks during Early Cambrian Period

SUN Houxue, HAO Fang, WANG Qi, TIAN Jinqiang

2024, 30(05):  622-633.  DOI: 10.16108/j.issn1006-7493.2023055

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The development mechanism of source rocks of the early Cambrian Yuertusi Formation is one of the key points of deep oil and gas exploration in the Tarim Basin. The completion of ultra-deep drilling of pre-Cambrian strata in the basin in recent years provides an ideal window for the study of the development mechanism of Cambrian source rocks in the basin. In order to investigate the sedimentary environment and paleo-productivity during the deposition of source rocks and clarify the enrichment mechanism of organic matter, a systematic analysis of TOC, major and trace elements and carbon and oxygen isotopes was carried out in a typical well of the Tabei area. The results show that the lower part of the Yuertusi Formation was in anoxic-sulfuration environment with high primary productivity. In comparison, the upper section was formed in the oxygen-poor sedimentary environment, and the productivity was gradually weakened to a low productivity level. Carbon and oxygen isotopes indicate that the lower member of the Yuertusi Formation was deposited under the background of extensive transgression with upwelling. The coupling of upwelling currents and mild hydrothermal activities provides abundant nutrients for the bloom of primary productivity during this period, and the enrichment of organic matter was mainly controlled by high productivity and good preservation conditions. There was basically no hydrothermal activities in the upper member of the Yuertusi Formation when it was deposited, the productivity level gradually decreased, and the reductibility of the water body also began to weaken, which was manifested in the low productivity level and the depositional environment of the upper system domain in the upper member, and eventually resulted in the low abundance of organic matter.