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    10 April 2022, Volume 36 Issue 02
    Water Resources and Environmental Research
    REE Concentration and Fractionation in Waters and Sediments from the Northern Branch of Ganjiang River, Poyang Lake Catchment
    LIU Maohan, LIU Haiyan, ZHANG Weimin, WANG Zhen, WU Tonghang, WANG Yugang
    2022, 36(02):  389-405.  DOI: 10.19657/j.geoscience.1000-8527.2022.002
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    The enhanced exploitation and widespread use of rare earth elements (REE) have led to increasing interest in REE distributions in environments and their geochemical behaviors. The Ganjiang River is one of the five major rivers in the Poyang Lake catchment, and is originated from the rare earth district in southern Ganzhou. However, the REE concentration and distribution in the downstream water bodies and surrounding groundwater are poorly understood. We investigated the REE geochemistry in waters and sediments of the northern branch of Ganjiang River. Results show that the total REE concentrations are of 230-1,146 ng/L (average 458.85 ng/L, surface water), 284-1,498 ng/L (average 634.94 ng/L, groundwater), and 177.9- 270.7 mg/kg (average 226.99 mg/kg, sediment). The PHREEQC simulation indicates that REEs are mainly in the form of carbonate complex (REEC03+) in the water samples. Both surface water and groundwater generally show enrichments of heavy REE (HREE) over light REE (LREE) and middle REE (MREE), while the sediments do not show significant enrichment features. The water samples are characterized by negative Ce and Eu anomalies, while the sediments show positive Ce but negative Eu anomalies, indicating that redox and water-rock reactions have influenced REE transformation in the water-sediment system. Along the flow path, REE concentrations tend to increase in groundwater, while both the degree of HREE enrichment and the REEC03+ proportion decreases. These behaviors reflect that REE concentrations are controlled by pH, colloidal sorption, complexation and surface water-groundwater interactions. The water HREE enrichment is likely attributed to carbonate complexation, and the negative Ce and Eu anomalies are related to the oxidative Ce precipitation and the parent rock REE inheritance. The positive Gd anomalies in the water samples from the middle and lower reaches of the river suggest anthropogenic REE input.

    Climatic Changes and Impacts on Water Quality of Erhai Lake in Dali Area, Yunnan Province over the Period from 1989 to 2019
    AN Guoying, GUO Zhaocheng, YE Pei
    2022, 36(02):  406-417.  DOI: 10.19657/j.geoscience.1000-8527
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    In this study, we characterized the climatic changes and their impacts on lake eutrophication in Erhai Lake and assessed the relationships between air temperature, precipitation amount, and trophic status index of the lake using the climate data collected from 12 monitoring stations in Dali of Yunnan Province, and water quality monitoring data of Erhai Lake from 1989 to 2019. During this time, the annual mean air temperatures showed a fluctuating upward pattern which clearly indicated a warming trend with the largest temperature increases in the wintertime; meanwhile, the annual precipitation amount showed a fluctuating downward tendency with the most substantial declines in autumns. Comprehensive trophic status index, total nitrogen, total phosphorus, and permanganate index levels increased, while levels of water transparency declined. The changes in overall water quality were characterized by two distinct stages: before 2003, the comprehensive trophic status index, total nitrogen, total phosphorus, and permanganate index levels increased rapidly, while water transparency measured by Secchi Depth declined; after 2003, these same indices were relatively stable with minor fluctuations. We found that the comprehensive trophic status index of Erhai Lake was positively correlated with the annual mean air temperatures, but negatively correlated with the annual precipitation amount. Total nitrogen and water transparency levels showed a distinct correlation with both the annual mean air temperatures and precipitation. Total phosphorus was correlated clearly with the average winter air temperature, and the permanganate index levels correlated with the mean summer/winter air temperatures, respectively. In terms of monthly changes, both the water pollution index and comprehensive trophic status index increased substantially between June and October from 2015 to 2019, indicating water quality during the dry season was significantly better than during flood season. In summary, the comprehensive trophic status index of Erhai Lake increased continuously due to rising air temperatures, and reduced precipitation and lake inflow from 1989 to 2019, and the intensification of lake eutrophication has not improved and the water environmental condition of Erhai Lake remains relatively fragile.

    Hydrochemical Characterization and Irrigation Suitability Analysis of Shallow Groundwater in Hetao Irrigation District, Inner Mongolia
    LI Zeyan, CAO Wengeng, WANG Zhuoran, LI Jincheng, REN Yu
    2022, 36(02):  418-426.  DOI: 10.19657/j.geoscience.1000-8527.2022.012
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    With the aggravation of conflict between supply and demand of water resources in the Yellow River basin, both Yellow River water and groundwater are used for agricultural irrigation in the Hetao region of Inner Mongolia (one of the large irrigation districts in China). In this paper, 499 groundwater samples and 1 Yellow River water sample were collected. Based on hydrogeochemical analysis of these samples, the irrigation suitabi-lity difference between groundwater and Yellow River water has been studied by SAR, PI, SC, RSC and Irrigation Water Quality Standard (GB 5084-2021). The results show that the environment of groundwater and Yellow River water are both weakly alkaline, and the major ions are Ca2+ and HC03-. The Gibbs diagram shows that the groundwater is affected by rock weathering/leaching and evaporation concentration, and the sodium salts (which have immense influence on irrigation suitability) come mainly from rock salt dissolution. According to the irrigation suitability analysis results about SAR, PI and RSC, the groundwater is suitable for irrigation. According to the SC evaluation result, the groundwater unsuitable for irrigation is mainly distributed in the main drainage channel in the northern irrigation area and along the Yellow River in the southern irrigation area. According to the irrigation water quality standard, except for the total arsenic and chloride, over 90% samples have other irrigation suitability indices. A total of 231 samples are suitable for irrigation. Comparing the irrigation suitability between groundwater and Yellow River water, we suggest that SAR and SC indices of the Yellow River water are better, while the PI and RSC indices of groundwater are better. The assessment result, using the irrigation water quality standard, shows that the Yellow River water is suitable for irrigation. This study gives data support for the irrigation water source selection, and provides a scientific basis for the future treatment and prevention of groundwater in the Hetao irrigation district in Inner Mongolia.

    Hydrochemical Characteristics and Human Health Risk Assessment in Downstream Ganjiang River of the Poyang Lake Basin
    WU Tonghang, LIU Haiyan, ZHANG Weimin, SUN Zhanxue, WANG Zhen, LIU Maohan
    2022, 36(02):  427-438.  DOI: 10.19657/j.geoscience.1000-8527.2022.018
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    Anthropogenic impact on the water quality of Ganjiang River in the Poyang Lake basin has received wide attention. Understanding the health risks of polluted water is crucial for better protection and utilization of water resource. In this study, 39 groundwater and 16 surface water samples were collected from the downstream Ganjiang River to analyze for their geochemical characteristics and influencing factors. Inverse modelling was done to unravel the groundwater quality evolution. Groundwater quality and non-carcinogenic risk were further evaluated. Our results show that the local groundwater is weakly acidic to neutral (pH=5.47-7.60), dominated by HCO3-Ca-Mg-type with minor Cl-Ca-Mg-type. Silicate weathering and mineral dissolution-precipitation impose the mainly control on the groundwater chemistry. Surface water is neutral to weakly-alkaline (pH=6.94-8.19) and mainly of HCO3-Cl-Ca-Na-type, which is related to the weathering of silicate rocks, atmospheric precipitation and human activity. Hydrogeochemical calculations with PHREEQC show that the minerals have mostly negative halite saturation index (SIHalite=-7.80 to -9.53), indicating that halite tends to dissolve. The low SI of dolomite (1.72 to -6.39), gypsum (-1.65 to -3.96) and calcite (-0.51 to -3.09) also indicate that these three minerals tend to be dissolved. The inverse modeling shows that groundwater evolution in the main stream has undergone dissolution of Ca-montmorillonite, halite, dolomite and calcite, and the consumption of CO2. Results of groundwater inverse modeling in the tributaries are generally similar to those in the main stream, except for route NCGW-3, which indicates the dissolution of kaolinite, calcite, chalcopyrite, and colomite, and the precipitation of gypsum, Ca-montmorillonite, biotite and plagioclase, and the generation of CO2. This may be attributed to human activities. Entropy-weighted water quality index (EWQI) calculation shows that groundwater quality in the main stream is better than that in the tributaries, and that the groundwater quality along the Ganjiang River is affected by Mn and N O 3 -. The non-carcinogenic risk is the highest to infants, followed by children, but relatively low to adults. The risk is higher in the tributaries than in the main stream.

    Variation Characteristics of Chromatic Parameters of Eolian Sediments and Environmental Evolution on the Northeastern Tibetan Plateau Since 9.4 ka
    HU Mengjun, JI Tianqi, ZHENG Dengyou, ZHUANG Jing, SUN Wenli, XU Aokang
    2022, 36(02):  439-448.  DOI: 10.19657/j.geoscience.1000-8527.2022.014
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    Eolian sediments from the Zeku profile (ZK) of the northeastern Tibetan Plateau as the object of the study. The chromaticity parameters a*, b*, L* and the calculation of C* and h* of 169 samples were measured by CM-5 spectrophotometer, and the environmental evolution of the northeastern Tibetan Plateau since 9.4 ka was discussed based on the analysis of the variation characteristics of each chromaticity parameter of wind-formed sediments, supplemented with the indexes of magnetization rate, SC/D, SiO2 and Fe2O3. The results shows that: (1) From the bottom to the top of the profile, the chromaticity parameters a* and L* are characterized by increasing first and then decreasing. (2) Chromaticity parameters can be used as effective proxies for reconstruction the paleoclimate on the northeastern Tibetan Plateau. The high values of a* and L* indicate the warm-wet environment, and the high values of h* indicate the cold-dry environment. Chromaticity parameters indicate different environmental sensitivities, but they are sensitive to climate abrupt change, which can be used to judge the typical cold and warm events of climate abrupt change. (3) The environment in the northeastern Tibetan Plateau since 9.4 ka has shown a development situation from warm-wet to cold-dry, which can be divided into two major stages. During 9,480-4,290 a BP, the climate was temperatureandhumidity, showing fluctuations of warmer and wetter→warmer and wetter→warmer and wetter. After 4,290 a BP, the climate wascold and dry, the climate as a whole is cold and dry, showing a change of warm and dry→warm→cool→cold and dry.

    Comprehensive Evaluation and Influencing Factors of Surface Soil Nutrient Chemistry in Southeastern Cultivated Area of the Nanyang Basin,Henan Province
    DONG Qiuyao, WEN Haotian, SONG Chao, YANG Zhenjing, YAN Mingjiang
    2022, 36(02):  449-461.  DOI: 10.19657/j.geoscience.1000-8527.2022.009
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    To comprehensively strengthen the utilization, development and management of local land resources and understand the local soil nutrient status, we conducted field investigation, sample collection and experimental analysis to characterize the spatial distribution, pH and nutrients in each township in the southeastern cultivated area of the Nanyang basin,Henan Province.We discussed the differences of pH and nutrients under different land use patterns and their influencing factors.The semi-variance analysis shows that the optimal fitting model for TP is exponential, and spherical model for TP, pH, K and organic matter.The local soil pH and nutrients show weak spatial correlation, indicating that the local soil is strongly affected by human activities.The average local soil pH is 5.44 (slightly acidic), and in terms of spatial distribution it is generally high in the south and low in the north.Nutrient grade evaluation shows that the contents of TN, TP and K are relatively rich, while organic matter is relatively lacking, which are Grade Ⅲ, Ⅲ, Ⅱ and Ⅳ, respectively.Comprehensive soil nutrient assessment shows that the nutrient level in the whole region is mainly medium, accounting for 69.1% of the total assessment points, and it is widely distributed in the whole region.Pearson correlation analysis shows that the local soil pH is weakly negatively correlated with organic matter and TN, and strongly positively correlated with K.Organic matter has a strong positive correlation with TN and a negative correlation with K.Soil factors are significantly different under different land utilization types.The data show that the average values of pH, TN, organic matter and K content in dry land soil are all lower than those in shrub land, while the values of TP are the opposite.In addition, local crop survey shows that the average pH in the maize growing area is lower than that in the peanut growing area.The main reasons for such variation are likely the different fertilization methods, dosage and types, crop types, land management, planting structure and soil background.Keywords:soil nutrient;land utilization type;spatial variation;influencing factor; Nanyang basin

    Salt Content Features and Sedimentary Environmental Evolution in Shallow-Level (<100 m) Soils from the Yangtze River Estuary
    GOU Fugang, GONG Xulong, YANG Lumei, ZHANG Yan, LIU Mingyao
    2022, 36(02):  462-473.  DOI: 10.19657/j.geoscience.1000-8527.2021.169
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    Soil salinity is an important reference indicator for engineering foundation design and agricultural development. By collecting and analyzing the soil salinity of 907 soil samples from the Yangtze River estuary region, the content of eight ions and pH value of the soil soluble salts were obtained. Accordingly, the study area (<100 m depth) was systematically analyzed in a brine-bearing characteristics of the light soil. The results show that each layer contains 0.028%-1.226% salt. The Holocene land has higher soil salt content with depth, with the maximum and minimum salinity (NaCl) occurring in layer 4-1 soft soil (26 m depth) of the lower Rudong Formation and layer 7-2 sand (81 m depth) of the lower Gehu Formation, respectively. For the latter, the HC03- ion content is the highest, followed by the Cl- and Na+ contents. Deep soil layer (Gehu Formation) has lower salt content, and the amount of viscous soil is generally greater than sand. Earth layer ESR value is higher than local surface freshwater SAR. The ESR maximum is 27.7 times that of the freshwater SAR, whilst the minimum is 2.7 times that of local surface freshwater ESR, indicating that the exchangeable soil Na content is high. Soil salinity (<100 m depth) was largely controlled by the Late Pleistocene transgression and Holocene transgression. The soil salinity comprises mainly NaCl, and the most important salt source is seawater impregnation or soaking. The Pleistocene layers contain terrestrial sediments, and have high salinity due to the Pleistocene and Holocene transgression. The lower and middle members of Rudong Formation are of deltaic facies, which are affected by Yangtze River and transgression, and the soil salinity ranges widely. The Rudong Formation (upper member) comprises continental sediments, and the soil has been widely desalted, with the highest HC03- content. The Cl- content has high corrosiveness in concrete construction, especially for the 4-1 silty clay layer, where the proportion of soils with at least low corrosive grade account for up to 99%, and basic anti-corrosion treatment should be done. The 2-1 and 2-2 soil layers (exposed on the surface) of the upper Rudong Formation are more alkaline, which has high impact on agriculture and engineering construction. It is necessary to add improved agents for soil improvement.

    Genesis Model of Geothermal Water in Dandong Area of Liaoning Province Based on Hydrogeochemical Characteristics
    YANG Fengtian, SHI Yujia, LI Wenqing
    2022, 36(02):  474-483.  DOI: 10.19657/j.geoscience.1000-8527.2022.017
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    Geothermal resources are abundant in Dandong. It is of great significance to establish the genesis model of the geothermal fields for sustainable utilization and further development. The geothermal fields of Bei-tang, Dongtang and Wulongbei were investigated for hydrochemical and isotopic analysis. The results show that the hydrochemical types of Beitang, Dongtang and Wulongbei geothermal water are SO4·Cl-Na·Ca, HCO3·SO4-Na and HCO3-Na·Ca, HCO3·SO4-Na and HCO3·Cl-Na, respectively. The source of the thermal water is atmospheric precipitation. The recharge elevations of Beitang and Dongtang geothermal fields are 678 and 376 m, respectively. According to 14C dating methods, the ages of the thermal waters in Beitang, Dongtang and Wulongbei geothermal fields are 2,000-3,300 and 2,200-7,200 and 700-2,900 a B.P., respectively. The reservoir temperatures of Beitang, Dongtang and Wulongbei geothermal fields are predicted to be 92, 120, and 100-101 ℃, respectively according to the silica and lg(Q/K) geothermometer. The thermal water circulation depth of Beitang, Dongtang and Wulongbei geothermal fields are ca. 1,900, 3,000 and 800-1,800 m, respectively. The thermal water is heated up during deep circulation through the fault zone, and then upwelled into shallow aquifers or outcrops as springs at the intersection of NNE and NW trending faults, which belong to low to medium temperature geothermal system of convective type.

    Geothermal Hydrogeochemical Characteristics and Genetic Analysis of the Seda-Songpan Fault Block
    HU Zexiang, ZHAO Xueqin, LI Song, LI Junya, WANG Yujue, YANG Luo
    2022, 36(02):  484-493.  DOI: 10.19657/j.geoscience.1000-8527.2021
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    To determine the geothermal resource occurrence and source in the Sedar-Songpan fault block, three hot springs(namely Reshuitang, Shangdagu and Kalonggou) in Heishui County of Sichuan Province were taken sampled, and analyzed for their water chemistry and isotopes, and the recharge source and heat storage temperature of geothermal water were discussed. The results show that the groundwater chemistry types of the Heishui hot springs are HCO3-Ca or HCO3-Na, and the replenishing water came mainly from atmospheric precipitation. The replenishment elevation of the Reshuitang, Shangdagu and Kalonggou is 5,121 m, 3,890 m and 3,921 m, respectively. Considering mineral saturation, SiO2 geothermometer was used to calculate the hot spring thermal storage temperature, yielding 119.036 ℃, 49.034 ℃ and 30.215 ℃, respectively. Based on the genetic analysis of the local geothermal water, we concluded that the underground hot water was formed by: the infiltration of meteoric water into the reservoir through the alpine recharge area, which absorbed heat from deep underground conducts and interacted with the wallrocks, forming the underground hot water. In the better developed parts of faults, cracks and joints, the hot water ascended along fault zones, and finally emerged as hot spring on the surface.

    Hydrochemical Characteristics and Formation of Four Hot Springs in Northern Hebei
    WANG Yixuan, ZHOU Xun, CHEN Mengying, MA Jingru, HAI Kuo, XIAO Meng, SHANG Ziqi, ZHANG Ying, YU Mingxiao
    2022, 36(02):  494-506.  DOI: 10.19657/j.geoscience.1000-8527.2022.004
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    This study examined four hot springs in northern Hebei, namely Mohegou (A10), Sandaoying (A11), Shanwanzi (A12) and Beidaba (A13). Through analyzing hot-spring water samples in 2010 and 2018, we unravel the hydrochemical characteristics of the springs and elucidate their formation. Local stratigraphy comprises mainly the Mesoproterozoic, Permian, Triassic, Jurassic, Cretaceous, Neogene and Quaternary sequences, with large number of plutonic units. The hot spring temperatures range from 26 to 75 ℃, and the pH and TDS is 7.2-8.2 and < 1 g/L, respectively. The cations of the local hot springs are dominated (> 90%) by Na+, whilst the anions are dominated by HC O 3 - and S O 4 2 -. The hydrochemical types of the four hot springs are of SO4·HCO3-Na, HCO3·SO4-Na, HCO3-Na and SO4·HCO3-Na type. The local hot springs have generally high H2SiO3 and F- concentrations, and their total REE contents range from 0.030 to 15.525 μg/L, existing mainly as carbonate and fluorine complexes. The chondrite-normalized REE patterns of the hot water samples are relatively gentle with LREE enrichment. The local hot springs are mainly recharged by atmospheric precipitation, and the geothermal reservoir temperatures are estimated to be 85-125 ℃ with the SiO2 geothermometer. The thermal groundwater may have undergone deep circulation, rises along the contact zone, fracture zones and faults, and emerges as hot springs on the land surface.

    Geochemical Signature and Genesis of Geothermal Water in Minghuazhen Formation, Luohe, Henan Province
    ZHAO Mingkun, SUN Yajun, DUAN Zhongfeng, SHEN Quanwei, LU Guijing
    2022, 36(02):  507-514.  DOI: 10.19657/j.geoscience.1000-8527.2021.049
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    Global environmental pollution remains severe, and the development of renewable energy such as geothermal has become a consensus in modern society. By combining systematically the geothermal and geological conditions of Luohe in Henan Province, and taking the Neogene Minghuazhen Formation geothermal water as a case study, we sampled and analyzed the hydrochemical field, temperature field, and isotopes. We proposed a geothermal-geological genetic model for Luohe. Our data indicate that the chemical types of local geothermal water are complex, including mainly Cl-Na, Cl-Na·Ca, Cl·SO4-Na types, followed by Cl·HCO3-Na and SO4·Cl-Na types. The geothermal water is sourced mainly from pore water of the Neogene Minghuazhen Formation with minor lateral recharge. The replenishment source comes mainly from atmospheric precipitation in the western and northwestern hilly areas. The circulation depth is 1,320 m, typical of a conductive geothermal system.

    Application of CSAMT in Geothermal Exploration in Hui’an, Fujian Province
    REN Xiaoqing, YU Hong, LUO Naning, LI Chaomin, WANG Qiyu
    2022, 36(02):  515-523.  DOI: 10.19657/j.geoscience.1000-8527.2021.184
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    This study attempts to solve the local hot spring bath water problem by conducting geothermal water exploration in Julong Town (Hui’an County, Quanzhou City), Fujian Province. This area contains mainly late Yanshanian feldspar granite. This study uses the Controlled Source Audio Magnetotelluric Method (CSAMT). Starting with deep structural analysis, a total of six CSAMT exploration lines are arranged, with 166 measurement points and a total length of 3.96 km. After collecting, processing, inverting, and interpreting the field data, three fault structures were identified, along with four low-resistance zones with possible water cut. Burial depth of the aquifer system in the area was also determined. Accordingly, a geothermal well (1,150 m deep) was excavated, yielding 600 m3/d water output and 34 ℃ water temperature, which supports the CSAMT results for geothermal water exploration in granite areas.

    Adsorption Characteristics of Cu onto Typical Sewage Irrigated-Soils from Baoding, Hebei Province
    GUO Zhengcai, GUO Huaming, WEI Liang, GAO Zhipeng
    2022, 36(02):  524-532.  DOI: 10.19657/j.geoscience.1000-8527.2022.010
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    As one of the most toxic inorganic pollutants in soil, heavy metal Cu can readily accumulate in organic farmland soil. Its accumulation in soil would both cause harm to plants and threaten local economic development, human health and ecological stability. Sewage irrigation results in pollutant accumulation (including Cu) in soils. In this study, the dynamic/thermodynamic characteristics of Cu adsorption on two typical sewage irrigated-soils from Baoding, Hebei were investigated by batch adsorption experiment. The parameters obtained from the kinetic adsorption model and isothermal adsorption empirical model show that the Cu adsorption capacity on soil S1 surface is stronger than that on the deeper soil S2. The organic matter content of S1 is higher than that of S2, which provides more surface adsorption interface, which may account for the stronger Cu adsorption capacity of soil S1. Ionic strength has little effect on soil Cu adsorption rate. The effects of solution pH and DOM content on Cu adsorption are significant. Adsorbed Cu content is positively and negatively correlated to pH and DOM content, respectively. Our results also suggest that soils are strong pH buffer, and thus short periods of acid rain would not cause significant Cu transport. However, the application of organic fertilizer may form water-soluble Cu-DOM complex with Cu, which accelerates the Cu transport in soil and pollutes shallow groundwater.

    Redox Dynamic Effect on Fluoride and Arsenic Released from Sediments in the Baiyangdian Plain, Hebei
    CAO Yuanyuan, GUO Huaming, GAO Zhipeng
    2022, 36(02):  533-542.  DOI: 10.19657/j.geoscience.1000-8527.2022.006
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    Precipitation, discharge and draining caused by seasonal fluctuations would generate redox oscillations in shallow groundwater system, which may shed light on the reactive transport of groundwater components in aquifers. To explore the influence of redox oscillations on the release of arsenic and fluoride in sediments, a sediment sample from the Baiyangdian Plain was collected for this study. Variations in aerobic/anaerobic conditions were controlled automatically. During the redox oscillations, solution composition changes in each experimental system were monitored. Results suggest that the groundwater As-F enrichment was promoted by the alkaline and reducing conditions. The reason may be that the pH is higher under reducing conditions, which is conducive to F- enrichment. In addition, DOM degradation produced large amount of HC03- and C032- in solution, which benefits groundwater F- enrichment via competition. Since As (III) adsorption onto sediments is weaker than that of As (V), the dominant As (III) species in reducing solution would promote As mobility. Furthermore, the higher pH reduces the As adsorption capacity onto sediments, which causes As desorption. We found that the varying S042- concentrations show no clear effect on the As-F enrichment in the dynamically redox experiments. To conclude, the dynamic redox changes would strongly affect the enrichment of As and F- in groundwater.

    Identification of Heavy Metal Distribution and Sources in Soil from a Mining Area
    QIAO Wen, WANG Yi, ZHANG Deqiang, YIN Xiulan, BAI Guangyu, HE Peiyong
    2022, 36(02):  543-551.  DOI: 10.19657/j.geoscience.1000-8527.2022.005
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    To explore the conditions of heavy metal pollution (incl. Cu, Pb, Zn, Cr, Ni, Cd, As, and Hg) and their sources in soils from a mining area in southern Jiangxi, a total of 40 soil samples were collected. Distribution characteristics and pollution sources of heavy metals were analyzed by a series of statistical methods, including frequency histogram, correlation, and principal component analyses. Our results suggest that: (1) Seven (out of eight) heavy metals measured in the soil samples exceed the Jiangxi background contents in varying degrees; (2) Contents of Pb, Zn, As and Hg in the soil exhibit normal distributions, while Cu, Cr, Ni and Cd contents show right inclining distributions. This may due to the varying extent of mining activities and different types of local land use; (3) Positive correlations among the soil Cu, Cr, and Ni contents suggest that they may have similar pollution sources, while the sources of Pb, Zn, and Cd may be different from those of Cu, Cr and Ni; (4) Principal component analysis suggests that contents of the eight heavy metals measured in soils may be the combined effect of two principal components, i.e., soil parent materials and mining activities; (5) Pb, Zn and Cd are the primary pollutions of the soil samples, and were mainly sourced from local mining activities.

    Distribution Coefficient of Ra in Groundwater and Its Determination Technique
    HAO Xin, YI Lixin, LI Luxuan, YANG Yongpeng
    2022, 36(02):  552-562.  DOI: 10.19657/j.geoscience.1000-8527.2022.007
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    In the past decade, the Ra isotope has attracted increasingly more research attention in the field of water environment and water resources. Important findings have been made on the application of Ra isotopes in estimating seabed groundwater discharge, calculating lake water balance, study of groundwater age and analysis of groundwater pollution source. This is due to the development of Ra isotope analytical technology and the enhanced understanding of Ra geochemical behavior. The Ra distribution coefficient (Kd) is a key parameter affecting the Ra migration in soil and aquifer, and its understanding is pivotal for accurate tracing of hydrological processes, especially groundwater cycle. We compiled a range of Kd value and analyzed the main influencing factors. We found that the Kd value in natural environment varies from 0.1-1×106 mL·g-1, extending across seven orders of magnitude between the maximum and minimum. The water salinity, pH, and Fe content in sediments have significant impact on Kd. The Kd determination methods were summarized and divided into four types, including the (1) “Rn” equilibrium, (2) thermodynamic adsorption equilibrium calculation, (3) experimental method, and (4) ion exchange equilibrium method. The pros and cons of each method were analyzed. We proposed the establishment of an accurate determination method of ion input recoil term in aqueous solution and to optimize analysis and calculation process, which is the technical idea of obtaining Kd value accurately. Our review and analysis can provide reference and technical support for studying the hydrogeochemical properties of Ra and its hydrologic applications.

    Review of Nitrate Source Apportionment and Nitrogen Isotope Fractionation in Groundwater
    YU Lu, ZHENG Tianyuan, ZHENG Xilai
    2022, 36(02):  563-573.  DOI: 10.19657/j.geoscience.1000-8527.2021.176
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    Groundwater nitrate (N O 3 -) pollution has become one of the world’s most serious geoenvironmental problems. Comprehensive and accurate identification of N O 3 - sources has important guiding significance for effective groundwater management and pollution prevention. In this study, we reviewed the N O 3 - sources in groundwater, isotope measurement methods, isotope features of pollution sources, quantitative analytical model, N O 3 - transformation process and isotope fractionation. By comparing the development and application of various N O 3 - source apportionment methods, we invoked that comprehensive and multidisciplinary understanding of N O 3 - sources is needed. Isotope enrichment factor is an important parameter to quantify the contribution of N O 3 - sources. The study of isotopic fractionation effect can better interpret the N O 3 - sources and transformation process in the groundwater, and provide reference for accurate tracing and effective prevention of groundwater N O 3 - pollution.

    Study on Chinese Maifanite in Promotion of Heterotrophic Denitrification in Water
    LIU Wenjun, LIU Tong, HU Weiwu, CHEN Nan, FENG Chuanping
    2022, 36(02):  574-582.  DOI: 10.19657/j.geoscience.1000-8527.2021.105
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    Microbial heterotrophic denitrification technology is widely used in municipal wastewater treatment. However, in practice, microbial activity is readily affected by environmental conditions (e.g., shock load and heavy metal stress), making the effluent unstable. Chinese maifanite, a natural silicate mineral, can effectively improve microbial activity and is resistate to environmental stress. Therefore, it can be used in microbial pollution control. Through batch experiments, the dosage and the effect of treatment methods of natural silicate mineral (Chinese maifanite) on heterotrophic denitrification were studied, and the mechanism of Chinese maifanite on microorganisms was explored. The results show that the dosage and treatment method would significantly affect the nitrate removal by microorganisms. The nitrate removal rate correlates positively with the Chinese maifanite dosage. When the dosage of Chinese maifanite is 350 g/L, the nitrate removal rate can reach 96%, while that of the control group is only 25%. The treatment method would affect the increasing effect of Chinese maifanite on denitrification. The ground Chinese maifanite has an advantage when the dosage is below 150 g/L. With increasing dosage, the untreated Chinese maifanite facilitates denitrification better. The untreated/ground/ball-milled Chinese maifanite extract was furtherly used in the denitrification promotion and microbial toxicity experiments. The experimental results show that the Chinese maifanite extract can improve the microorganism activity and environmental stress resistance. The main biological promotion factor of Chinese maifanite is the composition and concentration of the dissolved trace elements. Our results provide theoretical basis and practical application value for the microbial treatment stimulated by natural Chinese maifanite.

    Experimental Study on Oyster Shell Modification and Combined Oxygen Release Composite Materials for Remediation of Ammonia Nitrogen Pollution in Groundwater
    WU Fuxian, LI Wei, LI Shuiyun, CHEN Xiaodan, XIE Linshen, CHENG Gong, CHANG Xu, CHEN Chunxing, HAN Long
    2022, 36(02):  583-590.  DOI: 10.19657/j.geoscience.1000-8527.2021.073
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    Laboratory experiments were carried out on the performance and economic applicability of permeable reactive barrier filled with modified oyster shell-oxygen releasing composite material, with the aim to mitigate groundwater ammonia nitrogen pollution. Calcium peroxide was used as the oxygen-releasing compound, and mixed with cement, quartz sand/oyster-shell grain and calcium bentonite in a certain proportion, in order to make a spherical oxygen-releasing material with about 1.8 cm particle size. Finally, we studied the groundwater ammonia nitrogen repairing effects and their economic feasibility of two different size oyster-shell oxygen-releasing composite materials, and those of different adsorbent materials under different oxygen supply modes. The results indicate that the high-temperature modification of oyster-shell particles could not improve the comparative area of oyster shell. The specific surface area of oyster shell decreases with increasing calcination temperature and aggregation occurred. During the 95-day experiment, the dissolved oxygen of each experimental column was maintained at about 18 mg/L, and the basophilic bacterial action reduced the pH effectively. The oxygen-releasing material produced could provide the oxygen for the nitrifying bacterial growth in groundwater with low dissolved-oxygen for a long period of time. By the nitrification of alkali-resistant nitrifying bacteria, the permeable reactive barrier filled with oyster shell oxygen-releasing composite material could reduce the ammonia nitrogen concentration from 50 to 35 mg/L, whilst the repairing effect by oyster shell particles of different sizes is unobvious. In the long term, it is more economical to use oyster shells as adsorbents, and to use oxygen-releasing materials as oxygen supply. The use of the permeable reactive barrier (filled with modified oyster shell-oxygen) releasing composite material for long-term groundwater ammonia nitrogen repair is both effective and economical with activated carbon and zeolite framework.

    Optimized Groundwater Numerical Simulation Model with Trending Parameter Field
    NAN Tian, CAO Wengeng, WANG Zhuoran, ZHANG Juanjuan, ZHANG Dong
    2022, 36(02):  591-601.  DOI: 10.19657/j.geoscience.1000-8527.2022.008
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    Hydrogeological parameter field is the key and challenging topic in groundwater numerical simulation. Generally, high-precision simulation results are derived from more reasonable parameter field. In this study, a trending stochastic parameter field construction method was proposed with stochastic and spatial distribution simulation technology. We took the hydraulic conductivity field as an example, and used the MCMC sampling method and sample feature analysis to extract data structure first. After that, the stochastic parameter field was reshaped with the trend features. For the case study, we compared the traditional parameter field, which filled blocks with the regional mean value. The trending parameter field has significantly improved the model accuracy with the mean error reduced by about 2 times. Practically, the mean simulation error comes down from 2.76 to 0.64 m in the coarse-grained area. In contrast, there is little effect in the low permeability area. To conclude, our method can provide reference for optimizing groundwater numerical simulation, improve the model fitting accuracy, and better describe the groundwater flow system.

    Aquifer Medium Characterization of Unconsolidated Deposit in Guqiao Mining Area of Anhui Province, Based on Transition Probability Geostatistics
    DENG Hui, MA Lei, GAO Di, ZHAO Weidong, YANG Man
    2022, 36(02):  602-609.  DOI: 10.19657/j.geoscience.1000-8527.2022.003
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    Spatial distribution and heterogeneity of aquifer medium have critical influence on groundwater flow and solute transport. To characterize the spatial distribution of aquifer medium, the Guqiao mining area in Anhui Province was investigated, and the stochastic model of aquifer medium was established through transition probability geostatistics. We characterize the spatial continuity and variability of the hydrogeological structure of the mining area. Moreover, the local simulated profiles obtained by stochastic simulation were compared with the original hydrogeological profiles. Our results show that the conditional simulation method based on transition probabilities can accurately depict the local hydrogeological structure. Comparing the simulated profiles with the original ones, we found that the simulated results are consistent with the actual spatial distribution of the aquifer medium. This shows that the transition probability geostatistics approach can well adapt to characterize the he-terogeneity of aquifer medium.

    HEC-RAS-/GIS-Based Paleohydraulic Reconstruction of the Diexi Ancient Landslide-Dammed Lake Outburst Flood in Western Sichuan Province
    MA Junxue, CHEN Jian, CUI Zhijiu, LIU Beibei
    2022, 36(02):  610-623.  DOI: 10.19657/j.geoscience.1000-8527.2021.168
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    Landslide-dammed lakes and outburst floods have been widely developed along the Upper Minjiang River valley, due to the complex geological environmental conditions in this region. Hazard evolution reconstruction has major significance for regional disaster prevention and mitigation. This study is dedicated to the Diexi ancient landslide-dammed lake (DALL) triggered by a strong paleoseismic in the Upper Minjiang River in Western Sichuan Province, at the southeastern margin of the Tibetan Plateau. We focus on the fluid dynamics of downstream megaflood characteristics. The estimated former lake size was 1.1×107 m2, and the impounded volume was 2.9×109 m3. The maximum peak discharge and paleohydraulics of the landslide-dammed lake outburst flood (LLOF) were reconstructed with empirical equations and one-dimensional (1D) HEC-RAS hydraulic numerical model. The results reveal that the maximum peak flow of the Diexi ancient LLOF by HEC-RAS was 73,060 m3/s, largely similar to the results by the empirical methods (74,500-76,800 m3/s, avg. 76,000 m3/s), with an error of < 5%. The corresponding maximum flood depth and flow velocity are 70.1 m and 16.78 m/s, respectively. The inundated area during the modeled reach of Minjiang River was approximately 6.08 km2. The uncertainty bound of the maximum peak discharge was determined to be 69,000-81,000 m3/s. The maximum peak discharge of the Diexi ancient LLOF was more than one hundred times the average annual flow of Minjiang River (approximately 700 m3/s), indicating that it was an abnormally large outburst flood in Diexi Region once in a hundreds-of-thousand years in history, and also one of the world’s largest LLOFs. The direct consequence of the high-energy outburst flood was the formation of band- or terrace-shaped outburst deposit bars and boulder deposit terraces on both sides of the gorge and river-bed in the downstream. These findings are consistent with previous hydrological and sedimentary studies on the high-energy outburst floods, demonstrating the high reliability of our results. In addition, this study also shows that the 1D HEC-RAS model can be used to reconstruct the hydraulics of an ancient LLOF in deep-confined gorge environments. This study is of great significance to the paleoenvironment reconstruction and geomorphic evolution in the upper reaches of Minjiang River.

    Geochemistry
    Preliminary Study on Anomalous Source of Surface Soils in Covered Area Traced by Cu Isotope: A Case Study in the Luobuling Concealed Cu-Mo Deposit, Fujian Province
    JIANG Yao, LIU Xuemin, LI Jianting, HAN Zhixuan, WANG Yanyan
    2022, 36(02):  624-633.  DOI: 10.19657/j.geoscience.1000-8527.2022.02.23
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    Surface fine-grained soils have been sampled to explore concealed deposits in the covered areas in China. Determining the relationship between the surface anomalies and concealed orebodies is critical for the extensive application of this method in the future. In this paper, the Cu isotope is applied to trace the anomalous source of the surface fine-grained soils in the known concealed deposit, Luobuling Cu-Mo deposit, Fujian pro-vince. The following results have been obtained. (1) The δ65Cu range of minerals in ores is small (-0.04‰ to 0.56‰), indicating a high mineralization temperature (250 to 300 ℃). The δ65Cu value of ores increases obviously from deep to shallow, which is consistent with the variation of Cu isotopic composition in the porphyry metallogenic system from the early to the late stage. The difference in Cu isotopic composition among different stages is mainly caused by fluid fractionation. (2) The average Cu content of surface soils in the background area (59.4 μg/g) is significantly lower than that in the anomalous area (131.0 μg/g). However, the δ65Cu range of surface soils in the background area is -1.94‰ to -0.82‰, with an average of -1.38‰, and -5.01‰ to 1.05‰ in the anomalous area, with an average of -1.40‰. There is little difference between the background and the anomalous area. (3) Using Cu isotope to distinguish the origin of the Cu anomaly in surface fine-grained soils is not ideal in this deposit, which might be partly caused by the difference of Cu isotope composition in the ores. Meanwhile, the Cu isotope information of the surface soils could overlay that of hidden Cu deposits, or the Cu isotope fractionation occurs during the migration from the deep primary environment to the surface oxidation environment.

    Geochemistry and Source Identification of Heavy Metals in the Top and Subsoil of Yanqing District in Beijing
    HUANG Yong, DUAN Xuchuan, YUAN Guoli, LI Huan, ZHANG Qinrui
    2022, 36(02):  634-644.  DOI: 10.19657/j.geoscience.1000-8527.2022.02.24
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    As Yanqing District in Beijing is the ecological conservation of the capital, the study on the distribution and the source identification of heavy metals in the soil is of great significance to ensure the safe use of land and to prevent the risk of their ecological environment. In this study, 2 354 topsoil samples and 44 subsoil samples were collected from Yanqing District, and the concentrations of As, Cd, Cr, Hg, Ni, Pb, V, Zn and Sc were respectively analyzed. Based on the methods of the spatial analysis, multivariate statistics analysis and positive matrix factorization, the spatial distribution characteristics of these metals in the soil were illustrated, and the potential sources were identified, and the relative contribution of the different sources was also calculated. Conclusively, elements of V, Cr, Ni and As in the topsoil are mainly originated from soil parent materials. On the other hand, the relatively high level of Cd, Pb and Zn in the topsoil were observed in areas with high density of population, and human activities greatly affected their distribution. In addition, the distribution of Hg in topsoil was mainly affected by the atmospheric deposition. In the subsoil, the element of Hg showed high level in the residential area, and the left elements were almost not affected by human activities.

    Distribution Characteristics of Soil Selenium Content and Its Influencing Factors in Sanjiang County, Guangxi
    LUO Haiyi, LUO Xianrong, LIU Panfeng, MA Mingliang, ZHUO Yinyi
    2022, 36(02):  645-654.  DOI: 10.19657/j.geoscience.1000-8527.2022.02.25
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    Taking the soil of Sanjiang County in Guangxi as the research object, 2,751 samples of surface soil and 180 soil vertical profile samples were collected to determine the content of selenium in soil. The characteristics and influencing factors of soil selenium content were studied by using multivariate statistical analysis, geostatistical method, GIS spatial analysis technique and Pearson correlation analysis. The results showed that the average selenium content in the surface soil of the study area was 0.63 mg/kg and varied from 0.10 to 14.41 mg/kg. The soil is rich in selenium resources, and the area of selenium-full and selenium-rich soil was up to 95.87%. The distribution of selenium content in the soil is controlled by the geological background. The selenium content of the surface soil formed by different parent rocks is quite different. The Cambrian has the highest selenium content in soil with black rock series as parent material, with an average content of 2.58 mg/kg, the variation range is 0.31-14.41 mg/kg. Among different soil types, yellow soil has the highest selenium content, with an average content of 0.75 mg/kg, varying from 0.24 to 2.07 mg/kg, and paddy soil has the lowest selenium content, with an average content of 0.51 mg/kg. The soil selenium content of different land use types is quite different. Except for paddy fields, which are the basic natural state, all other land types are enriched. The selenium content of the surface soil in the study area is generally controlled by the selenium content of the deep soil, and the selenium content of the surface soil has secondary enrichment during the soil formation process. At the same time, soil pH, Corg, P, S, Al2O3, TFe2O3 and CIA also have a certain influence on the distribution of soil selenium content.

    Topsoil Organic Carbon Storage and Its Spatial and Temporal Variation in the Western Loess Plateau
    LI Chunliang, WANG Xiang, ZHANG Wei, QU Zhenggang, YANG Jing, ZHANG Jun
    2022, 36(02):  655-661.  DOI: 10.19657/j.geoscience.1000-8527.2022.02.26
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    Surface soil organic carbon plays an important role in soil carbon cycle in the Loess Plateau. A prelimi-nary study was conducted on the storage and distribution characteristics of soil surface organic carbon (SOC) in Gansu Province in the western part of the Loess Plateau,and the distribution regularity of SOC in different land utilization patterns and soil types was analyzed. Meanwhile,the difference of SOC in different landform was compared with the results of the second soil census in Gansu Province. The results showed that the average organic carbon density,from high to low,was forest land,construction land,cultivated land,orchard,grassland,unutilized land. The highest average organic carbon density,from high to low,in each soil type was as follows: cinnamon soil,alpine meadow soil,chernozem,chestnut soil,red clay,irrigated desert soils,anthropoge-nic-alluvial soil,black gunny soil,black loessial soil,yellow loamy soil,sierozem and sand. And the organic carbon density in different geomorphologic units,from high to low,was tablelands,terraces,hillside fields,gullies. The total organic carbon storage in the western part of the Loess Plateau is 78.56 Mt now,which is 10.54% higher than that in 1990,and the soil organic carbon density is 1.87 kg/m2. The storage of topsoil's organic carbon in the western part of the Loess Plateau is on the rise.

    Ore Deposits
    Analysis on Uranium Metallogenic Geological Conditions and Prospecting Prospects in Naren Area, Erlian Basin
    L&xdc; Yonghua, MIAO Aisheng, WANG Guo, LI Shuguang, GAO Zhengrong
    2022, 36(02):  662-671.  DOI: 10.19657/j.geoscience.1000-8527.2022.02.27
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    Although uranium mineralization information has been found in the upper member of Saihan Formation in Naren area through regional evaluation in recent years, the analysis of uranium mineralization conditions and prospective prediction are obviously inadequate due to the low level of work. In this paper, the uranium source, structure, stratum, sedimentary facies, oxidation-reduction and paleoclimate conditions in Naren area are comprehensively analyzed based on the comprehensive arrangement of borehole and seismic data, combined with systematic sampling, analysis and testing results. The authors believe that uranium source is sufficient in this area, and a large amount of uranium was activated and migrated in the erosion source area during the warm sub-humid to dry hot climate transition period. The Late Cretaceous-Cenozoic tectonic activity provided the slope zone suitable for the development of oxidation zone and the upward passage of deep reducing fluid. The first sub-member of the upper Saihan Formation has braided river delta sandbodies with large scale, stable mud-sand-mud structure and favorable oxidation-reduction conditions, which are ideal space for uranium ore formation. In the best position of uranium mineralization condition, there is one prospective area of grade Ⅰ, which is expected to be implemented as a new uranium deposit.

    Geochemical Characteristics and SHRIMP Zircon U-Pb Geochronology of Quartz Schist from the Dawudian Graphite Deposit in Urad Middle Banner, Inner Mongolia
    YANG Peiqi, LIU Jingdang, LIU Shumei, YANG Fei, YANG Xiaowei
    2022, 36(02):  672-681.  DOI: 10.19657/j.geoscience.1000-8527.2022.02.28
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    Dawudian graphite deposit of Urad Middle Banner in Inner Mongolia occurs in black rock series of Jianshan Formation of Mesoproterozoic Bayan Obo Group. Ore-bearing rocks consist of andalusite-sericite-chloritequartz-schist and sericite-chlorite-quartz-schist. This paper carried out SHRIMP U-Pb dating analysis for graphite, suggesting that sedimentary ages of the graphite ore deposit is less than (1,792.09±17.12) Ma. Petrological and geochemical study of ore-bearing rocks shows that the ore-bearing rocks are characterized by enrichment of LILE, indicating a stable reduced sedimentary environment. Ore-bearing formation also presents sedimentary characteristic of littoral neritic environment. It can be concluded in this study that the graphite deposit belongs to metamorphic amorphous graphite ore deposit resulting from thermal contact of intrusive rocks to sedimentary rock series.

    Oil and Gas Exploration
    Reservoir Characteristics and Dynamic Accumulation Process of the Quaternary Mudstone Biogas
    TANG Xianglu, JIANG Zhenxue, SHAO Zeyu, LONG Guohui, HE Shijie, LIU Xiaoxue, WANG Yuchao
    2022, 36(02):  682-694.  DOI: 10.19657/j.geoscience.1000-8527.2022.200
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    Quaternary mudstone biogas is a new type of resource in unconventional oil and gas field, and has great exploration and development potential. Taking the Quaternary mudstone biogas at Sanhu (Qaidam Basin) as an example, the reservoir characteristics of the Quaternary mudstone biogas and its dynamic accumulation process are analyzed through core observation, optical microscopy, scanning electron microscopy (SEM), high-pressure mercury injection and component analysis. The results show that the reservoir is characterized by frequent sand-mud thin interbeds and strong vertical and horizontal heterogeneity. In the early-stage diagenesis, Ro is below 0.3%. Rock consolidation degree is low, shells are not fossilized, and porosity is generally above 20% with many micro-/nano-pores. The TOC of mudstone reservoir is very low (average 0.2%-0.4%). The kerogen type is mainly Ⅲ, and the main components include crude fiber, hemicellulose, and organic nitrogen, representing the main source of the Quaternary mudstone gas generation. The Quaternary mudstone biogas is methane-dominated (average 98.85%) dry gas. The formation water type is mainly moderately-acidic CaCl2. The mudstone breakthrough pressure is the main drive for methane retention and accumulation. The characteristics of low permeability, water-rich, and clay determine that the mudstone has self-sealing ability. The cold climate, high salinity, sufficient gas source, and effective self-sealing are the key factors for mudstone biogas accumulation, and three mudstone biogas accumulation modes are established: (1) self-sealing enrichment zone in sag area, (2) water-sealing enrichment zone in slope area, and (3) overlapping enrichment zone of mudstone gas and sandstone gas in structural highs.

    Stratified Structure and Formation Mechanism of Paleokarst Cave in Carbonate Reservoir of Tahe Oilfield
    CHEN Huaxing, KANG Zhihong, KANG Zhijiang
    2022, 36(02):  695-708.  DOI: 10.19657/j.geoscience.1000-8527.2022.193
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    With the constantly deepening development of carbonate reservoir, the structural characteristics of stratified cave reservoir and the similar connection characteristics of fluid dynamic in same layer,has been gradually discovered and attracted by researchers. Structure, formation factors and processes of stratified paleokarst were the key to the effective development of this kind of reservoir. Based on comparison of the in-situ stratigraphic fabric and the characteristics of field karst caves, it is considered that Tahe Ordovician karst systems have better correlation marker stratums and lithology difference, which lays a material foundation for the development of stratified karst caves. Geological phenomena including multi-layer karst caves along horizontal bedding and tube-shaped ancient underground steams controlled by bedding cracks in the field verify the widespread existence of stratabound karst. On the basis of well identification, well logging correlation, well performance and seismic waveform characteristics in karst caves, such as the typical karst cave zone, three main cave layers were identified and a brand-new geological structure profile of three-layer cave reservoir was established: The caves in the first layer were mainly filled with glutenites, the caves in the second layer were large in scale and seriously filled with mud, and the caves in the third layer were small in scale and mainly developed in karst landform highlands. Formation mechanism of stratabound karst was discussed by using modern karst theory: carbonate host rock fabric was one of the material basis and main controlling factors for karstification, karst water in subsurface flow zone (full of CO2) controled the lateral development of karst caves, The karst palaeogeomorphology controled the lateral difference of caves in the same layer, The vertical migration of groundwater level controled the karst stages and stratified structure of the caves under gentle formation conditions. Finally, on the basis of research and understanding, the development model of stratabound karst reservoir was constructed by integrating all karst controlling factors.

    Sedimentary Microfacies Identification and Controlling Factors of the Toutunhe Formation (2nd Member) in the Eastern Fukang Slope, Junggar Basin
    WEI Zede, LI Shengli, ZHANG Rongji, YAO Zongquan, YAN Yongchao, ZHANG Tong, LIU Yong, XU Wenqian
    2022, 36(02):  709-718.  DOI: 10.19657/j.geoscience.1000-8527.2021.074
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    The Toutunhe Formation in Fudong Slope (Junggar Basin) is an important oil and gas exploration target. Based on the core, well logging and seismic data, it is crucial to explore the sedimentary characteristics and distribution patterns in the study area for future prospecting. Our results show that the target strata are mainly composed of mudstone, siltstone and fine sandstone, which generally shows mud-sand inclusion features. The sandstone component has low maturity and proximal provenance. The grain size probability accumulative curve is mainly jump-suspension type, and the hydrodynamic type is traction current. Logging curves can be classified into three types: bell, box and line. Based on lithology, grain size, logging and seismic reflection characteristics, we suggest that meandering river deposits dominate in the study area, and that meandering channel, point bar, flood plain and abandoned channel microfacies can be identified. The sediment source in the study area is from northeast, and the distribution of meandering river was mainly affected by local topography, sediment transport mode, and grain size characteristics. The meandering river may have extended from northeast to southwest. The curve of the channel in the southwest increased, and the channels gradually formed a network, with point bar sand bodies better developed. Meanwhile, there are also contiguous meandering river deposits in the northwest. Therefore, the point bar sand bodies in the northwest and southwest should be considered while searching for high-quality reservoirs in future oil and gas exploration.

    Classification of Sub-sags in the Erlian Basin and Its Petroleum Prospecting Significance
    CAO Lanzhu, WU Piao, HOU Dujie, WEI Xiuli, ZHEN Ronghua
    2022, 36(02):  719-728.  DOI: 10.19657/j.geoscience.1000-8527.2021.193
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    A total of 56 sags and 21 uplifts have been discovered in the Erlian Basin. Each sag consists of two or three sub-sags, according to the segmentation of sedimentation center in the Tenggeer Formation (1st member). In order to study the geological classification and its correlation with the hydrocarbon generation potential of the sub-sags, the geological and geochemical statistical data from 23 sub-sags were analyzed. It is found the maximum burial depth of the Paleozoic basement surface, the sub-sag area, and the paleo-water salinity during the epoch of the Aershan and Tenggeer (1st member) Formation have respectively controlled the maximum total thickness and organic matter maturity, area, organic matter abundance and type of the source rocks in the Aershan Formation and Tenggeer Formation (1st member). Thus, we propose that the sub-sags could be divided into the highly-mature, mature, and lowly-mature class, and 14 sub-classes according to the differences of the maximum basement burial depth, deep sub-sag area, and paleo-water salinity of the two formation strata. Coupled with hydrocarbon generation potential assessment of 23 sub-sags, we consider that hydrocarbon-rich sub-sags generally belong to highly-mature large-medium sub-sags sub-class or mature large-medium salty sub-sags sub-class. We suggest that the salty or brackish sub-sags are more suitable for tight oil exploration, as they possess more advantageous source and reservoir conditions. As highly-mature saline sub-sags are better developed in the Manite and the Ulanqab depressions, priority of exploration area selection should be given to the sub-sags in these two depressions.

    Geochemistry of Carbonates Near the Cambrian Series 3-Furongian Boundary and Its Paleoenvironmental Constraints
    BAI Xiangyu, MA Junwei, XIA Qingping, TAN Xianfeng, LI Kaikai
    2022, 36(02):  729-741.  DOI: 10.19657/j.geoscience.1000-8527.2021.197
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    The early Furongian mass extinction was likely related to paleoenvironmental changes, yet their relations remain unconstrained. Geochemical signals of shallow-water platform sediments are more sensitive to paleoenvironmental changes than deep-water sediments, which is conducive to understanding this issue. Carbonates in the Cambrian Series 3 Gushan Formation and the Furongian Changshan Formation in the Xiaweidian section of the Xishan (Beijing) were selected for element geochemical and isotopic analyses. The aim is to trace the paleoenvironmental evolution during the Kushanian-Changshanian transition, and to assess its effects on life evolution. The results reveal a major fluctuation in the paleoclimate and paleo-marine environment during the transition period. The sea-level lowstand at the end of Kushanian Stage was followed by rapid transgression in the early Changshanian Stage, during which seawater may have become significantly reducing. These changes, combining with the seawater temperature drop (to minimum) and salinity rise (to maximum), could explain the collapse of trilobite ecology and its subsequent extinction. During this period, the frequent alternation of dry-hot and warm-humid climate and the large-scale transgression may have facilitated the terrigenous detrital (and nutrients) input into the seawater, which promoted biological growth. The presence of deep reducing water is favorable for organic matter preservation, which eventually led to the Positive Carbon Isotope Excursion in the carbonates. We propose that strong correlation is unlikely between the Positive Carbon Isotope Excursion and the Middle to Late Changshanian sea-level drop.

    Geochemical Characteristics and Source of Crude Oil in Chang 8 Member of Yanchang Formation, Ganquan Area, Ordos Basin
    ZHU Biqing, CHEN Shijia, BAI Yanjun, LEI Junjie, YIN Xiangdong
    2022, 36(02):  742-754.  DOI: 10.19657/j.geoscience.1000-8527.2022.199
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    Through systematic collection of crude oil, sandstone and source rock samples from Ganquan in the southeastern Ordos Basin, the geochemical characteristics of Chang 8 crude oil in Yanchang Formation were characterized, and the origin and source of the crude oil clarified. We show that Chang 8 crude oil is the normal crude oil featured by low viscosity, initial boiling point, pour point and sulfur content. The Chang 8 crude oil have mixed organic matter sources, which were formed in a weakly reducing environment during the peak oil generation stage. According to the distribution characteristics of C30DiaH and dicyclic sesquiterpenes, the crude oils can be divided into type I and II: Type I crude oil is mainly distributed in Chang 81 reservoir, and type II crude oil is distributed in Chang 82 reservoir. The Chang 9 and Chang 8 source rocks are featured by low C24TeT/C26TT, abnormally high C30DiaH, high 8β(H)-homodrimane and 8β(H)-drimane, while Chang 7 source rock show the opposite features. Oil-source correlation shows that type I crude oil was sourced from Chang 7 source rock, whilst type II crude oil was sourced from Chang 8 and Chang 9 source rocks. The crude oils in Ganquan are mainly enriched in Chang 82 member, and Chang 82 reservoir in western Ganquan was contributed by Chang 8 and Chang 9 source rocks, while Chang 82 reservoir in eastern Ganquan was mainly contributed by Chang 9 (and minor Chang 7) source rocks. We recognize that the hydrocarbon contribution of the Chang 8 and Chang 9 source rocks may have been key to the crude oil enrichment in the Chang 82 member, which has guiding significance for future exploration.