2022, Volume 29 Issue 3
    25 May 2022
    Previous Issue    Next Issue

    For Selected: Toggle Thumbnails
    Genesis and occurrence of high iodine groundwater
    WANG Yanxin, LI Junxia, XIE Xianjun
    2022, 29(3): 1-10. 
    DOI: 10.13745/j.esf.sf.2022.1.47

    Abstract ( 521 )   HTML ( 33 )   PDF (5594KB) ( 406 )  

    China has the largest occurrence of water-borne high iodine groundwater in the world. Long-term excessive iodine uptake has substantial negative effects on the health of local residents. Under different environmental hydrogeological conditions, the genetic types of high iodine groundwater include burial-dissolution type, compaction-release type, and evaporation-concentration type. Based on our understanding of the genesis of high iodine groundwater, big data models were employed to predict the nation-wide occurrence of high iodine groundwater in China. The high-risk area (p>0.5) of high iodine groundwater was found to account for 19.8% of China’s land area, covering the regions already known to have high iodine groundwater in their subsurface. Studies on the genesis and occurrence of high iodine groundwater, including characterization of organic iodine species in groundwater system, identification of the microscopic mechanisms affecting hydrogeochemical behaviors of iodine, and modeling of the processes controlling the iodine mobilization, will provide important scientific evidence to support the safe supply of water and prevention of water-borne hyperiodized goiter.

    Figures and Tables | References | Related Articles | Metrics
    Opportunities and challenges in deep hydrogeological research
    WEN Dongguang, SONG Jian, DIAO Yujie, ZHANG Linyou, ZHANG Fucun, ZHANG Senqi, YE Chengming, ZHU Qingjun, SHI Yanxin, JIN Xianpeng, JIA Xiaofeng, LI Shengtao, LIU Donglin, WANG Xinfeng, YANG Li, MA Xin, WU Haidong, ZHAO Xueliang, HAO Wenjie
    2022, 29(3): 11-24. 
    DOI: 10.13745/j.esf.sf.2022.1.49

    Abstract ( 639 )   HTML ( 37 )   PDF (4206KB) ( 545 )  

    Rapid social and economic development requires a steady supply of energy and natural resources. Such resources are markedly abundant in the deep earth. “Marching into the deep earth”, therefore, is an inevitable trend in energy supply such that the current resource exploration and development technology, cost, and financial prospects are compatible with meeting the resources needs. Owing to the “carbon peak and carbon neutrality” campaign, green, low-carbon, high-quality development has become a shared goal for society. To meet the major demands for energy, resource security, and ecological environmental protection, it is particularly important to accelerate the clean energy exploration and development, enhance the carbon storage capacity, and strengthen research on geological energy storage. These tasks are closely related to the study of deep hydrogeological process and such study requires immediate attention. By analyzing several literature reports, a comprehensive comparative study was conducted on the course of research discipline development and its relevant hot issues. This study sought to summarize and assess the current situation and future trends in deep hydrogeological research related to the distribution and circulation of deep groundwater, the accumulation of geothermal and lithium resources under the control of deep groundwater, the development of clean energies such as deep geothermal, hot-dry rock, and shale gas, the geological sequestration of CO2 in the deep saltwater layers, and geological energy storage in the aquifer. Deep and systematic studies were found to be needed in such areas owing to the dynamic mechanism of groundwater circulation, the material and energy conversion process, water-rock interaction, the thermal accumulation mechanism, and the accuracy and precision of monitoring technology in deep hydrogeology under the conditions of high temperature and high pressure. In addition, the characterization of reservoir heterogeneity, the heat source mechanism, the sustainable development technology of deep resources and energy, the evolution characteristics of deep resources and environment under human intervention, the earthquake induced by hydraulic fracturing, the sensitivity of faults triggered by fluids, and the evolution of the triggering process will continue to remain as key research topics.

    Figures and Tables | References | Related Articles | Metrics
    Advances and trends in hydrogeochemical studies: Insights from bibliometric analysis
    WANG Guangcai, WANG Yanxin, LIU Fei, GUO Huaming
    2022, 29(3): 25-36. 
    DOI: 10.13745/j.esf.sf.2022.1.48

    Abstract ( 550 )   HTML ( 35 )   PDF (7295KB) ( 295 )  

    Hydrogeochemistry plays an important role in sustainable development, but only a few reviews have documented the development in this field. This work used the bibliometric visualization analysis softwares (CiteSpace and VOSviewer) to analyze the current status of hydrogeochemical research based on the data obtained from Web of Science database from January 1, 1982 to November 17, 2021. The results showed that the number of papers and citations in hydrogeochemistry presented an overall upward trend and the number of papers after 2010 was twice as many as that before 2010. Hydrogeochemical study is on the road of prosperity. In recent years, the increase in the number of relavent publications in China is higher than in the developed countries, such as the United States, Germany, and Canada, reflecting the strong research activities in this field in China. Such an active state of hydrogeochemical research in China is closely related to the funding from the National Natural Science Foundation of China and the involvement of various scientific research institutions. Through the keyword analysis, the main themes in hydrogeochemistry from 1982 to 2021 were groundwater quality and human health, isotope application, element migration and transformation and microbial processes, and hydrogeochemistry of groundwater-surface water interactions. Results of bibliometric tool analysis and statistics from the International Symposium on Water-Rock Interactions since 1974 showed that the trends in hydrogeochemical studies included water-rock interactions on different spatial scales and in different environments, development and application of isotope technology, biogeochemistry, and groundwater quality.

    Figures and Tables | References | Related Articles | Metrics
    Progress in hydrogeochemical study of Karst Critical Zone: A critical review
    ZHOU Changsong, ZOU Shengzhang, FENG Qiyan, ZHU Danni, LI Jun, WANG Jia, XIE Hao, DENG Rixin
    2022, 29(3): 37-50. 
    DOI: 10.13745/j.esf.sf.2022.1.40

    Abstract ( 443 )   HTML ( 14 )   PDF (2966KB) ( 297 )  

    Karst Critical Zone (KCZ) extends across lithosphere, hydrosphere, pedosphere, atmosphere and biosphere. Understanding the structure, characteristics and hydrogeochemical processes of KCZ is a key issue in the scientific research on Earth’s Critical Zone as well as karst hydrology. Based on summarization of relevant research results obtained at home and abroad, this paper analyzed the hydrogeochemical connotation, KCZ hydrodynamic vertical zoning, and hydrogeochemical processes and mechanisms under KCZ framework, and explored the law and evolutionary mechanism of hydrogeochemical process of KCZ under changing environment. Futher, this paper pointed out the shortcomings and problems in KCZ research. The current work is within the scope of traditional karst groundwater research. It does not consider the hydrogeochemical process and its coupling relationship between the plant canopy and the karst aquifer from the perspective of KCZ framework system, neither has it considered the potential impacts of epochal factors, such as introduction of new pollutants, in-depth implementation of big data methodology, and gradual changes in global carbon emission paths, on karst hydrogeochemical research. Future researches may focus on hydrogeochemical study of new pollutants based on framework; karst hydrogeochemical study based on big data system; karst hydrochemical study under the “dual-carbon strategy”; material transformation and energy transfer processes and their coupling driven by KCZ hydrogeochemistry; and integration of high-resolution monitoring, evaluation and simulation approaches in KCZ research.

    Figures and Tables | References | Related Articles | Metrics
    Comprehensive evaluation of regional groundwater pollution: Research status and suggestions
    HE Baonan, HE Jiangtao, SUN Jichao, WANG Junjie, WEN Dongguang, JIN Jihong, PENG Cong, ZHANG Changyan
    2022, 29(3): 51-63. 
    DOI: 10.13745/j.esf.sf.2022.1.29

    Abstract ( 639 )   HTML ( 20 )   PDF (3804KB) ( 277 )  

    A comprehensive evaluation of regional groundwater pollution is essential for understanding the regional groundwater quality characteristics, pollution status and mechanism, and groundwater quality evolution. Such evaluation also serves as an important basis for groundwater pollution prevention and control and water quality improvement. However, due to inherent limitations of certain conventional concepts, opinions and research practices in the field of hydrogeology, there are many problems and challenges associated with groundwater quality and pollution evaluation, such as the lacks of clear distinction between natural poor quality water and polluted water and impact assessment of human activities. Therefore, the reliability of the evaluation results is often questioned, which causes confusion among government agencies over pollution control application and decision making. To improve this situation, this study sought to assess the current status of comprehensive evaluation of regional groundwater pollution based on the evaluation results of recent years, review the problems associated with the groundwater quality evaluation, background value, pollution evaluation, and distinction between poor water quality and water quality degradation, identify the anthropogenic pollution activities, and ultimately make some suggestions. The resulting suggestions include: (1) Establish an evaluation framework with the “indicator classification evaluation-combination expression” approach to minimize ambiguity and misleadings in the evaluation results. (2) Establish apparent background value to facilitate the assessment of pollution status, differentiation between poor water quality and water quality deterioration, and identification of impactful anthropogenic activities. (3) Clarify the distinction between poor quality water and quality degraded water in order to effectively distinguish between natural poor quality water and polluted water, elucidate the impact of these water types on the groundwater quality, and help decision-makers understand the causes of unsafe water. (4) Identify and quantify anthropogenic pollution activities to help understand water pollution caused by imported pollution, induced water quality deterioration and change of water hydrochemical property, and highlight the trends of groundwater quality evolution to develop better pollution prevention and control methods.

    Figures and Tables | References | Related Articles | Metrics
    Typical redox-sensitive components in groundwater systems: Research highlights and trends
    GUO Huaming, GAO Zhipeng, XIU Wei
    2022, 29(3): 64-75. 
    DOI: 10.13745/j.esf.sf.2022.1.37

    Abstract ( 331 )   HTML ( 16 )   PDF (2315KB) ( 188 )  

    Although C, N, S cycling is essential to cycling of redox-sensitive components and energy flux in groundwater systems, the mechanism of its couplings to Fe-Mn cycling and relavent functional microbial metabolic pathway in controlling the transport and transformation of redox-sensitive components is poorly understood. Based on comprehensive national and international literature surveys, this paper divided the groundwater redox-sensitive components into oxic condition-related enrichment type (oxic type, enriched in oxic groundwater) and reducing condition-related enrichment type (reducing type, enriched in reducing groundwater), and systematically sorted out C, N, and/or S cycling-driven transport and transformation processes of typical redox-sensitive components (U, Cr, Fe, As as main examples) in groundwater systems. The research highlights of the relevant research fields mainly included coupling of C, N cycling and transport-transformation of typical redox-sensitive components, C, S cycling-driven mechanisms for the mobilization of reducing type components and the immobilization of the oxic type components, hydrogeochemical interactions bewteen typical redox-sensitive components, and microbe-mediated transformation and enrichment of typical redox-sensitive components. The research trends revealed by this study were metabolic pathway-based C, N, S cycling and its control on the transformation processes and enrichment mechanisms of typical redox-sensitive components in groundwater systems.

    Figures and Tables | References | Related Articles | Metrics
    Advances in 222Rn application in the study of groundwater-surface water interactions
    LIAO Fu, LUO Xin, XIE Yueqing, YI Lixin, LI Hailong, WANG Guangcai
    2022, 29(3): 76-87. 
    DOI: 10.13745/j.esf.sf.2022.1.44

    Abstract ( 523 )   HTML ( 23 )   PDF (2354KB) ( 352 )  

    Groundwater-surface water interaction is important for water resource management and aquatic ecosystem protection. Radon (222Rn) has been widely used in the investigation of groundwater-surface water interaction owing to its application advantages, such as its large concentration difference between groundwater and surface water, noble gas properties, and ease of measurement. In this study, we analyzed 222Rn applications in different surface waters (sea, river, lake, etc.) and identified the 222Rn concentration variation in groundwater as a key challenge in the estimation of groundwater discharge into surface water. When estimating submarine groundwater discharge (SGD), 222Rn mixing loss and its variable concentrations in seawater, and the complexity of SGD components would produce uncertainties in the estimation results. Also, it is difficult to determine 222Rn atmospheric loss when estimating riverine groundwater discharge using the 222Rn method. Further, little attention has been paid to the application of 222Rn in tracing surface water flow into groundwater. Thus, future studies on 222Rn application in regarding to groundwater-surface water interaction should focus on (1) reducing final uncertainty in 222Rn-based estimation of groundwater discharge due to variable 222Rn concentrations in groundwater; (2) accurately characterizing the 222Rn atmospheric loss for different surface waters under different hydrological conditions; (3) expanding scientific applications of the 222Rn method; and (4) developing a software that integrates the 222Rn mass balance model and uncertainty analysis.

    Figures and Tables | References | Related Articles | Metrics
    Distribution characteristics and causes of arsenic in shallow groundwater in the Pearl River Delta during urbanization
    LÜ Xiaoli, ZHENG Yuejun, HAN Zhantao, LI Haijun, YANG Mingnan, ZHANG Ruolin, LIU Dandan
    2022, 29(3): 88-98. 
    DOI: 10.13745/j.esf.sf.2022.1.26

    Abstract ( 541 )   HTML ( 7 )   PDF (7479KB) ( 1585 )  

    A high level of arsenic (As) in groundwater (ρ(As)>10 μg/L) is a potential threat to safe drinking water and the ecological environment. The sources of As in groundwater derived from coastal urbanized areas are complex, which mainly include various anthropogenic and geogenic sources. The rapidly urbanized Pearl River Delta was selected as the study area. The occurrence of and key driving factors for As enrichment in the shallow aquifers in areas with different urbanization levels in the Pearl River Delta were evaluated via mathematical statistics and principal component analysis. According to the results, the total dissolved As concentration in shallow groundwater ranged from below the detection limit to 420 μg·L-1 in the study area, with As(Ⅲ) as the main form. ρ(As) was found to be generally higher in porous aquifers than in fractured or karst aquifers. The proportion of As in the groundwater of urbanized areas was more than five times that of non-urbanized areas. Among the 1567 groups of groundwater samples collected from the study area, 89 high As groups, or 5.7% of total, had high level of As (ρ(As) >10 μg·L-1). Among them, 82 groups were from shallow porous aquifers, 4 groups from fissure aquifers, and 3 groups from karst aquifers, accounting for 7.8%, 0.8%, and 9.7% of total, respectively. Compared with historical hydrochemical data collected from 2005 to 2008, the average ρ(As) in shallow high As groundwater of newly added construction areas increased by 30% in 10 years. The chemical type of high As groundwater mainly included HCO3-Ca and Cl-Na types, characterized by high pH, low redox potential (Eh), low NO 3 - concentration, and positive correlation between ρ(As) and concentrations of NH 4 +, Fe, and Mn or oxygen consumption. Under microbial degradation and mineralization of organic matter, reductive dissolution of As-bearing iron (oxygen) hydroxide in the Quaternary basement muddy sedimentary strata in the Delta plain was identified as the cause of As mobilization. The leaking and infiltration of As-containing industrial wastewater produced during the urbanization process were also important sources of As in groundwater in Shunde District, southern Foshan City. Due to the dual effects of the original sedimentary environment and human input, the neutral to weakly alkaline, closed to semi-closed reducing environment that is rich in organic matter formed in the Delta plain, was the main cause of the occurrence of high As in groundwater.

    Figures and Tables | References | Related Articles | Metrics
    Distribution and co-enrichment genesis of arsenic, fluorine and iodine in groundwater of the oasis belt in the southern margin of Tarim Basin
    SUN Ying, ZHOU Jinlong, YANG Fangyuan, JI Yuanyuan, ZENG Yanyan
    2022, 29(3): 99-114. 
    DOI: 10.13745/j.esf.sf.2022.1.33

    Abstract ( 385 )   HTML ( 10 )   PDF (6810KB) ( 194 )  

    Owing to the scarcity of surface water resources, groundwater is an important water source in the oasis belt of the southern margin of Tarim Basin. Thus, it is very important to systematically identify the distribution and origin of arsenic, fluorine, and iodine in groundwater in this area. Based on the detection results of 233 groups of groundwater samples from the oasis belt of the southern margin of Tarim Basin, the spatial distribution and hydrochemical characteristics of groundwater with high arsenic, high fluorine, and high iodine in different aquifers were analyzed, and the hydrogeochemical processes that affected the source, migration, and enrichment of arsenic, fluorine, and iodine in groundwater were further revealed by combining the geological and hydrogeological conditions with the groundwater occurrence environment in the study area. The levels of arsenic, fluorine, and iodine in groundwater were found to vary from 1.0-91.2 μg/L, 0.01-28.31 mg/L, and 10.0-2 637.0 μg/L, respectively. Groundwater samples with high arsenic, high fluorine, and high iodine accounted for 7.3%, 47.2%, and 11.6% of the total water samples, respectively, and arsenic, fluorine, and iodine co-enrichment accounted for 3.0%. Arsenic, fluorine, and iodine co-enriched groundwater was found to be mainly distributed in Minfeng County in the middle of the study area, and the Cl·SO4-Na type was identified as the main hydrochemical type. Groundwater fluorine and iodine levels significantly increased from the recharge zone to the transition zone and then to the evaporation zone. Further, arsenic levels were greater in both the transition and evaporation zones. The sampling points for arsenic, fluorine, and iodine co-enrichment in groundwater were mainly distributed in the shallow confined aquifer of 36-60 m. Shallow groundwater was affected by evaporation and mineral dissolution and precipitation, which increased with an increase in the arsenic, fluorine, and iodine enrichment terms. Quaternary aeolian deposit had a remarkable influence on fluorine content, while pluvial- lacustrine deposit had a great influence on arsenic and iodine content. Altogether, fine-grained lithology, gentle terrain, shallow burial conditions of groundwater, slightly alkaline groundwater environment, and mineral dissolution mediated by organic matter under microbial degradation were the main mechanisms conducive to arsenic, fluorine, and iodine co-enrichment.

    Figures and Tables | References | Related Articles | Metrics
    Distribution and formation processes of high fluoride groundwater in different types of aquifers in the Hualong-Xunhua Basin
    XING Shiping, GUO Huaming, WU Ping, HU Xueda, ZHAO Zhen, YUAN Youjing
    2022, 29(3): 115-128. 
    DOI: 10.13745/j.esf.sf.2022.1.34

    Abstract ( 385 )   HTML ( 10 )   PDF (11070KB) ( 162 )  

    High fluoride (F-) groundwater of natural origin is an environmental and drinking water safety issue, which has attracted worldwide attention. Although many studies have focused on the formation process of high fluoride groundwater, the distribution and formation processes of high fluoride groundwater in different types of aquifers (Quaternary aquifer, bedrock fissure or karst aquifer, clastic aquifer) under complex hydrogeological conditions in the plateau basin are poorly understood. Phreatic groundwater, confined groundwater, and spring water (Quaternary aquifer spring water and bedrock fissure spring water) samples were obtained from the Hualong-Xunhua Basin for chemical and isotopic analyses to reveal the genesis of high fluoride groundwater. The fluoride concentrations in groundwater samples were found to range from 0.25 to 7.73 mg/L. High fluoride groundwater (F->1.0 mg/L) was mainly distributed in spring water and phreatic water along the Yellow River Valley area and the Bayan low mountaineous and hilly areas, as well as in deep confined groundwater. However, the variation pattern of F- concentration along the depth is complex. Phreatic water in the Yellow River Valley area that recharged the Yellow River generally has high F- concentration, while phreatic water in the Yellow River Valley recharged by the Yellow River has low F- concentration. Ca-poor and Na-rich alkaline soda water is beneficial to F- enrichment in groundwater. Fluoride in spring water and phreatic water are mainly derived from the dissolution of fluorite. However, in confined groundwater, it is mainly derived from fluorite and other fluoride-containing minerals. For phreatic and Quaternary aquifer spring water, evaporative concentration processes promotes fluoride enrichment. In addition, competitive adsorption of coexisting anions and cation exchange are the causes of high fluoride in spring water (Quaternary aquifer spring water and bedrock fissure spring water) and phreatic water, while cation exchange contributes the most to fluoride enrichment in confined groundwater. This study provides a scientific basis for the exploration and development of safe (low fluoride) groundwater in the Hualong-Xunhua Basin.

    Figures and Tables | References | Related Articles | Metrics
    Distribution and fractionation of rare earth elements in high fluoride groundwater from the North China Plain
    LIU Haiyan, LIU Maohan, ZHANG Weimin, SUN Zhanxue, WANG Zhen, WU Tonghang, GUO Huaming
    2022, 29(3): 129-144. 
    DOI: 10.13745/j.esf.sf.2021.7.24

    Abstract ( 299 )   HTML ( 26 )   PDF (7249KB) ( 249 )  

    High-fluoride groundwater is a major environmental problem that has caused global concerns. Although numerous studies have been done on the chemical characteristics, formation and migration mechanisms of high-fluoride groundwater, little is known about the concentrations and fractionation characteristics of rare earth elements (REE) in high-fluoride groundwater or if REE can be used as a tracer for studying the formation and distribution of high-fluoride groundwater. These uncertainties have limited REE application in high-fluoride groundwater research. In this paper, we investigated the fluoride and REE concentrations and distributions in groundwater collected along a flow path in the North China Plain (NCP) where strong fluoride anomalies in groundwater were observed. We found the groundwater fluoride concentrations ranged from 0.28 to 9.33 mg/L, with 55% groundwater exceeding the China drinking water standard (1 mg/L). According to PHREEQC calculation, fluorine occurs in groundwater as NaF, CaF+, MgF+ and, predominantly, F-(85.42%-99.39%). High-fluoride groundwater is mainly distributed in the central alluvial lacustrine plain and the eastern alluvial marine plain, with 60% at depths below 180 m. Hydrochemical analysis indicated the formation of shallow high-fluoride groundwater is mainly controlled by evaporation and concentration, while deep high-fluoride groundwater is a result of mineral dissolution and competitive ion adsorption through water-rock interactions. The groundwater REE concentration is at pico to nanomolar level, and, according to PHREEQC calculation, REE species are mainly carbonate complexes ( REECO 3 + and $REE(CO_{3})_{2}^{-})$, with 0-1.18% REE in complex with F-(REEF2+ and REEF 2 +). The upper continental crust (UCC)-normalized REE patterns are characterized by enrichments of heavy REE (HREE) and middle REE (MREE) over light REE (LREE) and have significant negative Ce anomalies (0.11<Ce/Ce*=CeUCC/(LaUCC×PrUCC)0.5<2.29). The HREE enrichment in groundwater is mainly attributed to the preferential complexation of HREE over LREE or HREE with carbonate in forming more stable carbonate complexes. Along a groundwater flow path, both REE and fluoride concentrations in deep aquifers generally increase following similar trends. Besides, high-fluoride groundwater is more prone to HREE enrichment. These findings suggest that REE can potentially be used as a fluoride indicator for studying fluoride enrichment in natural aquifer systems.

    Figures and Tables | References | Related Articles | Metrics
    Source of salt and the salinization process of shallow groundwater in the Yellow River Delta
    HOU Guohua, GAO Maosheng, YE Siyuan, ZHAO Guangming
    2022, 29(3): 145-154. 
    DOI: 10.13745/j.esf.sf.2022.1.45

    Abstract ( 296 )   HTML ( 11 )   PDF (5640KB) ( 184 )  

    Groundwater salinization is one of the most prominent problems in the ecological environment of the estuary delta. Identifying the recharge sources of groundwater and salt is critical to understand the process of groundwater salinization. To assess groundwater replenishment and distinguish the source of salt in shallow groundwater in the Yellow River Delta, different types of water samples, such as underground water, surface water, and seawater, were collected for this study and the ions ratio, Piper diagram, and Gibbs diagram were employed to analyze the concentration of eight major ions, the composition of D and 18O, and the concentration of Br and Sr. According to the results, (1) shallow groundwater in the Yellow River Delta is mainly saline water comprising 3 g/L-38 g/L of total dissolved solids (TDS) while groundwater is mainly of the Cl-Na type. (2) Groundwater in the delta region is mainly recharged by atmospheric precipitation, and has experienced varying degrees of evaporation during the recharge. In contrast, groundwater near the banks of the Yellow River is mainly derived from the side seepage recharge, and the poor horizontal permeability of shallow groundwater aquifers limits the scope of lateral seepage replenishment of the Yellow River. (3) The ocean is the main source of shallow groundwater salinity in the Yellow River Delta. The salinity of groundwater near the Yellow River and close to the coast is caused by seawater mixing. The groundwater salinity in ancient river areas, such as the Diaokou River in the north of the delta, is mainly caused by the leaching and dissolution of marine evaporative salts.

    Figures and Tables | References | Related Articles | Metrics
    Dual carbon isotope (δ13C-Δ14C) characteristics and carbon footprint in the spring-pond systems at the Puding Karst Water-Carbon Cycle Test Site
    LI Dong, ZHAO Min, LIU Zaihua, CHEN Bo
    2022, 29(3): 155-166. 
    DOI: 10.13745/j.esf.sf.2022.1.35

    Abstract ( 672 )   HTML ( 4 )   PDF (5051KB) ( 145 )  

    The dissolved inorganic carbon (DIC) and organic carbon (OC) transported to the ocean by rivers are affected by natural and anthropogenic factors. Understanding the influence of these factors on the age, source, and transformation of DIC and OC can help constrain global carbon budget and improve the assessments of natural and human impacts on the riverine carbon cycle. The present study uses dual carbon isotopes (δ13C-Δ14C) of DIC, particulate organic carbon (POC), and aquatic plants with traditional hydrogeochemical characteristics in the spring (groundwater) and spring-fed pond (surface water) systems at the Puding Karst Water-Carbon Cycle Test Site to identify the relavent carbon sources and carbon transformation processes. The results showed that (1) the Δ14C of DIC and POC in the spring-pond systems displayed the same trend, that is, the Δ14C value is lower in the spring water than in the pond water, indicating likely a younger CO2 invasion of the pond system. (2) The changes in water chemistry and carbon isotope of pond water were controlled by different land use and aquatic plants. (3) The OC concentrations were significantly higher in pond water than in spring water, and the Δ14C values of POC were close to those of submerged plants and DIC (apparent ages of 3200-900 years). Such finding indicates that the POC in the pond water was mainly derived from aquatic photosynthesis, which involved old carbon (DIC)—produced by the weathering of carbonate rocks—as carbon source to generate new autochthonous OC (AOC) with negative Δ14C values and “old” apparent age. (4) The contribution percentage of AOC to POC in surface water was more than 75%. Meanwhile, the AOC flux in the spring-pond systems was between 250-656 t C km-2 a-1, and the surface water system of grassland contributed the most AOC and had the highest AOC flux relative to other land use. Such finding indicates the important role of primary production in the organic carbon cycle in shallow water controlled by submerged plants. Overall, the regulation of aquatic plant communities through land use adjustment in karst areas can have major impact on the increasing of carbon sink capacity in these areas.

    Figures and Tables | References | Related Articles | Metrics
    Hydrochemical characteristics of shallow groundwater and carbon sequestration in the Tianjin Plain
    LI Haiming, LI Mengdi, XIAO Han, LIU Xuena
    2022, 29(3): 167-178. 
    DOI: 10.13745/j.esf.sf.2022.1.39

    Abstract ( 303 )   HTML ( 9 )   PDF (8364KB) ( 250 )  

    Atmospheric CO2 concentration plays a crucial role in controlling global climate change. Understanding the carbon cycle and CO2 balance with an accurate assessment of atmospheric CO2 is key to formulating regional CO2 reduction strategies and identifying new carbon sink pathways. Carbonate weathering-related carbon sink is an important subject of global carbon cycle research. This study analyzed the shallow groundwater hydrochemical characteristics, and estimated the total groundwater storage, DIC storage in groundwater, and carbonate weathering-related carbon sink capacity of groundwater in the Tianjin plain area. From the northern piedmont plain to southern alluvial plain and coastal plain, a N-S and NW-SW horizontal hydrochemical zoning pattern in shallow groundwater was apparent, as groundwater types varied from freshwater and brackish water with low TDS to brackish water with high TDS, and water hydrochemical types changed accordingly from HCO3-Ca·Na·Mg → Cl·SO4-Na → Cl·HCO3-Na → Cl-Na. The areas of freshwater, brackish water and saline water were 733, 3034 and 6564 km2, respectively, where Ca2+, Mg2+, and HCO 3 - in groundwater were mainly derived from the dissolution of carbonate. In the study area, the total shallow groundwater storage was 22416 million m3; the total DIC storage was 8.13×106 t; and the total carbon sink capacity was 4.11×106 t. In the freshwater, brackish water, and brackish water zones of the study area, the shallow groundwater storages were 1578 million, 62459 million and 14592 million m3, respectively; the DIC concentration ranged from 19 to 200 mg/L, 19 to 200 mg/L, and 19 to 342 mg/L, respectively; the DIC storages were 0.67×106 t, 1.65×106 t and 0.58×106 t, respectively; and the carbon sink capacities were 0.22×106 t, 0.90×106 t and 2.98×106 t, respectively. Groundwater storage, DIC storage, and carbon sink capacity increased along the groundwater flow direction across the study area.

    Figures and Tables | References | Related Articles | Metrics
    Carbon flux in a typical dolomite-dominated drainage basin in humid subtropical climate
    ZENG Cheng, HE Chun, XIAO Shizhen, LIU Zaihua, CHEN Wangguang, HE Jianghu
    2022, 29(3): 179-188. 
    DOI: 10.13745/j.esf.sf.2022.1.43

    Abstract ( 215 )   HTML ( 8 )   PDF (3861KB) ( 137 )  

    Karstification is directly involved in the global carbon cycle. Understanding the mechanism of karst carbon sink is of great significance for an accurate evaluation of the carbon cycle. Carbonate rocks are widely distributed in China, especially in southwestern China. Although quite amount of research on inorganic carbon sequestration in limestone-dominated watersheds of this area has been carried out, only few involved the dolomite counterparts, which has adverse impacts on the accurate assessment of China’s carbon sink potential in karst systems and the national effort toward carbon neutrality. To fill this research gap, we investigated the Huangzhou River Basin in Shibing, Guizhou Province, a representative domolmite-dominated drainage basin in humid subtropical climate in southwestern China. We conducted a year-long (May 2018 to May 2019) automated hydrological, hydrochemical monitoring study of water-rock-gas interaction and inorganic carbon sequestration in the drainage basin, and obtained high temporal resolution continuous monitoring data on regional rainfall and water flow, water temperature, water conductivity and pH at the outlet area of the Huangzhou River Basin. The saturation indexes of calcite and dolomite and the partial pressure of CO2 in river water were then calculated based on a chemical thermodynamic model. Our study show that (1) the Huangzhou River Basin is a typical drainage basin in mountainous area that is significantly impacted by rainfall. Although flash flooding happens frequently, the chemical regime of the dolomite-dominated drainage basin is still controlled by its chemostatic behavior. (2) The river is sourced from dolomite aquifer upstream on a residual plateau where good quality water-bearing media made of karstified dolomite are developed on either side of a shallow waterbed; whereas its middle and downstream sections lack well developed karst system, with runoff overland into streams. Due to CO2 release from river surface, the calcite saturation index of river water is high at the outlet, where travertine deposition could be found at the riverbed. (3) According to the chemical thermodynamic model of open system for dolomite, the HCO 3 - concentration in karst groundwater discharged to the river was calculated to be 5.1 mmol/L using the soil CO2 data for different land use types. This value is 16% higher than the average concentration of HCO 3 - in river water at the outlet of the Huangzhou River Basin, indicating the dissolved inorganic carbon in the river water is reduced due to turbulence-promoted degassing and aquatic photosynthesis. (4) The carbon flux in the dolomite-dominated watershed, calculated by the load estimation method, was 36.43 t CO2/(km2·a). This value is not significantly higher than the carbon flux in other carbonate-dominated drainage basins in southern China, suggesting the CO2 concentration in land cover is still inversely proportional to watershed runoff in the dolomite-dominated drainage basin, so that its carbon flux remains relatively constant even in humid subtropical climate.

    Figures and Tables | References | Related Articles | Metrics
    Microbial fields and multi-field coupling in organic contaminated soil-groundwater systems
    XIONG Guiyao, WU Jichun, YANG Yun, ZHU Xiaobin, LIU Mengwen, SONG Yalin
    2022, 29(3): 189-199. 
    DOI: 10.13745/j.esf.sf.2022.1.32

    Abstract ( 418 )   HTML ( 18 )   PDF (4708KB) ( 209 )  

    Understanding the impact of microbial communities on the migration and transformation of organic pollutants is the basis for efficient remediation and treatment of organic contaminated sites. Microorganisms in nature exist as “fields” via coupling with hydrodynamic field, temperature field, chemical field, etc. to exert their functions in the process of maintaining ecological stability and material circulation. The bibliometric analysis results revealed that in recent years, researches on microorganisms and organic matter have been mainly focused on three aspects: microbial community structure, biodegradation of organic matter, and migration and transformation of organic matter, along with a series of related studies; whereas only few studies have been conducted to quantitatively characterize microorganisms in the form of “fields” for their role in material circulation-transformation and maintenance of ecological stability. Hence, we sought to provide a definition for microbial field, and proposed a conceptual model and a mathematical model of microbial field in organic contaminated site. Furthermore, we explored the main influencing factors and mechanism of microbial field, and constructed a constitutive model of microbial field coupled with hydrodynamic field, temperature field and chemical field. Finally, the prospects for future research on microbial field were proposed.

    Figures and Tables | References | Related Articles | Metrics
    Application and energy efficiency analysis of in-situ thermal remediation technology for contaminated sites
    ZHANG Xiaogang, ZHANG Fang, LI Shupeng, WEI Yunxiao, HOU Deyi, LI Guanghe
    2022, 29(3): 200-206. 
    DOI: 10.13745/j.esf.sf.2022.1.42

    Abstract ( 302 )   HTML ( 6 )   PDF (3037KB) ( 138 )  

    To address the difficulties associated with the effectiveness and efficiency assessments of in-situ thermal remediation (ISTR) technology, this study analyzed and revealed the principals of heat transfer and pollutant removal, the key influencing factors such as thermal conductivity and electrical conductivity, and the energy efficiency of ISTR. Based on the pilot-scale implementation of in-situ electrical resistance heating (ERH) remediation technology at a contaminated site, heating performance of the ERH system and the spatio-temporal distribution of the temperature field were analyzed. Further, the causes of spatial variation of temperature were investigated. According to the analysis, the site was heated primarily via electrical resistance heating and thermal conduction by the electrode well. The heating efficiency was affected by the electrode well distance and site lithological characteristics. Heat loss to the surface and around is a key factor for future energy efficiency assessment of ISTR technology.

    Figures and Tables | References | Related Articles | Metrics
    Natural attenuation of perchlorate: A column experiment study
    LIANG Kaixuan, LIU Fei, ZHANG Li
    2022, 29(3): 207-216. 
    DOI: 10.13745/j.esf.2022.1.36

    Abstract ( 391 )   HTML ( 8 )   PDF (3913KB) ( 108 )  

    Perchlorate ( ClO 4 -), a low molecular weight toxic inorganic complex anion is a widespread contaminant in the environment. Perchlorate contamination is a serious environmental problem as perchlorate is known to impact thyroid function by replacing iodine intake due to its similar molecular size with iodine. Column experiments, using river sand from the polluted site as the experimental material, were conducted to stimulate natural attenuation of the target pollutant, perchlorate ( ClO 4 -). The effects of iron oxides and nitrate ( NO 3 -) were also evaluated. The results show that ClO 4 - natural attenuation is mainly dependent on microbial degradation in the aquifer, and the groundwater environment is more conducive to microbial activity. Natural river sand can remove 2 mg/L ClO 4 -; however, the process is slow and the reduction amount is limited. A lack of electron donors was found to result in a long-term removal efficiency of less than 10%. Iron oxides can stimulate natural attenuation of ClO 4 -. In fact, the attenuation process began to be affected when the concentration of dissolved iron was lower than 5.5 mg/L. Nitrate ( NO 3 -) in groundwater has an inhibitory effect on ClO 4 - reduction. When NO 3 - concentration was less than 10 mg/L, an apparent reduction in ClO 4 - could be initiated.

    Figures and Tables | References | Related Articles | Metrics
    Adsorption and transport of uranium in porous sandstone media
    CUI Di, YANG Bing, GUO Huaming, LIAN Guoxi, SUN Juan
    2022, 29(3): 217-226. 
    DOI: 10.13745/j.esf.sf.2022.1.30

    Abstract ( 414 )   HTML ( 8 )   PDF (2546KB) ( 149 )  

    After the decommissioning of a in-situ leach uranium mining site, residual uranium leaching fluid in the aquifer migrates and diffuses downstream posing pollution risks to the surrounding groundwater. In this study, a series of batch and column experiments were designed to investigate the adsorption and migration behavior of uranium in aquifer sandstone in an in-situ leach uranium mining area in northern China. In batch experiments, uranium adsorption on sandstone reached equilibrium within 12 h, and in the process a positive correlation between the initial uranium concentration and sandstone’s uranium adsorption capacity was observed. It was found that the uranium adsorption process was endothermic and the increase in temperature was beneficial for uranium adsorption. The pH of the eluent and HCO 3 - concentration have a strong influence on uranium adsorption. Maximum uranium adsorption was reached at around neutral pH, and higher HCO 3 - concentration led to lower level of adsorption. These effects are due to the alteration of uranium complexation in the solution and the surface charge properties of sandstone. In column experiments, pH, uranium concentration, flow rate, and HCO 3 - concentration were the most important factors affecting uranium migration. Weaker acidity (pH≤7) was found to be associated with fewer late uranium breakthrough in the sandstone column; whereas higher uranium concentration, flow rate, and HCO 3 - concentration might cause early uranium breakthrough. The two-point non-equilibrium model could well describe the uranium migration process in the sandstone column under variable conditions. The partition coefficients obtained from batch experiments were 1.1-6.6 fold higher than those obtained from column experiments. According to the aquifer characteristics and hydrogeochemical characteristics, we suggest that the distribution coefficient of 48.1 mL/g would be suitable for describing uranium migration in sandstone aquifers in the study area. Overall, this study provided a theoretical basis for the reactive transport process and for the natural remediation of polluted groundwater in the in-situ leaching uranium mining areas.

    Figures and Tables | References | Related Articles | Metrics
    Pollution characteristics and biodegradation mechanism of petroleum hydrocarbons in gas station groundwater in the Tianjin Plain
    LIU Xuena, LI Haiming, LI Mengdi, ZHANG Weihua, XIAO Han
    2022, 29(3): 227-238. 
    DOI: 10.13745/j.esf.sf.2022.1.41

    Abstract ( 447 )   HTML ( 13 )   PDF (6886KB) ( 156 )  

    Petroleum hydrocarbon pollution in gas station groundwater is a common phenomenon. This study sought to sample and analyze gas station groundwater under various hydrogeological conditions to determine the pollution characteristics of petroleum hydrocarbon in gas station groundwater and the characteristics of groundwater chemical types. Factor analysis, correlation analysis, and multiple regression analysis were used to reveal the potential biodegradation mechanism of petroleum hydrocarbon in gas station groundwater. According to the results, groundwater chemicals can be mainly divided into four types: Cl-Na, HCO3-Na, HCO3-Ca, and SO4-Na types. The detection rate of petroleum hydrocarbons in the groundwater was 85.71%, and the detection concentration range was 0.02-0.35 mg/L. Factor analysis revealed that the main factors affecting the chemical composition of groundwater were water-rock interaction and biodegradation of petroleum hydrocarbons. The correlation between TPH and groundwater chemical indexes showed that the total petroleum hydrocarbon (TPH) was negatively correlated with K+, Na+, Cl-, Mn, Mg2+, and SO 4 2 -, but not significantly correlated with pH, HCO 3 -, NO 3 -, NO 2 -, Ca2+, and Fe. Halophilic or salt-tolerant microorganisms might also be present in the gas station groundwater environment, which accelerates the TPH biodegradation rate as TPH concentration decreases with increasing salinity. In the microorganism degradation of TPH using electron acceptors ( SO 4 2 -, Mn, NO 3 -, Fe), the contribution percentage of electron acceptors were ranked as iron reduction (64.88%) >manganese reduction (24.86%) >sulfate reduction (5.78%) >nitrate reduction (4.46%). Thus, the biodegradation of petroleum hydrocarbons by Fe-Mg-reducing bacteria in gas station groundwater is the dominant reaction.

    Figures and Tables | References | Related Articles | Metrics
    Pollutant distribution and microbial characteristics at a petrochemical site in the Yangtze River Economic Belt
    YE Xiangyu, CHEN Xuexia, YU Bo, ZHANG Min, GUO Caijuan, LU Xiaoxia
    2022, 29(3): 239-247. 
    DOI: 10.13745/j.esf.sf.2022.1.46

    Abstract ( 643 )   HTML ( 10 )   PDF (3743KB) ( 112 )  

    Soils at different depths were collected from three sampling points in an in-service petrochemical site in the Yangtze River Economic Belt. Thereafter, the concentration of petroleum hydrocarbons and the microbial community structure in the samples were measured to reveal the pollutant distribution and microbial characteristics. The overall pollution degree of the three points was found to differ; however, the pollutant concentration first increased and then decreased with depth in all cases, with the highest concentration found at the depth of approximately 4.0 m (i.e., near the groundwater level). C6-C9 up to 5302 mg/kg, C10-C40 up to 625.6 mg/kg, aromatic hydrocarbon up to 455.2 mg/kg, and halogenated hydrocarbons up to 41.54 mg/kg were detected in the soils. The richness and diversity of soil microorganisms were found to decrease with an increase in soil depth, and at the same depth, the richness and diversity of the soil microorganisms decreased with an increase in soil pollutant concentration. At the phylum level, the relative abundances of Actinobacteria, Firmicutes, and Spirochaetes were significantly positively correlated with the concentration of petroleum hydrocarbon (p<0.05). Further, at the genus level, the relative abundances of Streptomyces, SCADC1-2-3, Desulfitobacterium, and Cryptanaerobacter were significantly positively correlated with the concentration of petroleum hydrocarbon (p<0.05).

    Figures and Tables | References | Related Articles | Metrics
    Simulation of bimolecular reactive solute transport in porous media via image analysis
    LIU Yong, ZHANG Qi, QIAN Jiazhong, WU Dun, ZHANG Wenyong
    2022, 29(3): 248-255. 
    DOI: 10.13745/j.esf.sf.2022.1.28

    Abstract ( 373 )   HTML ( 12 )   PDF (3945KB) ( 97 )  

    In this study, reactive solute transport experiments in porous media were carried out under different particle sizes (ϕ1.5-2.0, 2.5-3.0, and 3.5-4.0 mm) and flow rates (1.0, 1.5, and 2.0 mL/s). We used copper sulfate and disodium EDTA as bimolecular reactors and simulated their transport via image analysis. The incomplete mixing advection-dispersion reaction equation (IM-ADRE) based simulation and prediction of bimolecular reactive solute transport was investigated, and parameter sensitivity analysis was performed. The results showed that the concentration of color reactive solutes in porous media can be accurately obtained via image analysis. The determination coefficient between the gray value and concentration was greater than 0.96. The IM-ADRE model gave high accuracy predictions for bimolecular reactive solute transport in porous media under different conditions, with less than 3.71% relative errors. The change of experimental conditions had significant effects on parameters D, M and β0 of IM-ADRE model, indicating that the model parameters are dependent on the environmental conditions, and the dependency rules need to be further calibrated according to actual environmental conditions, which can help promoting IM-ADRE model applications.

    Figures and Tables | References | Related Articles | Metrics
    The relationship between groundwater displacement rate, air-entrapped saturation, and quasi-saturated hydraulic conductivity in quasi-saturated porous media
    CHENG Donghui, LI Hui, WANG Jun, LI Shuang, HUANG Mengnan, MA Chenglong, RAO Ze
    2022, 29(3): 256-262. 
    DOI: 10.13745/j.esf.sf.2022.1.38

    Abstract ( 285 )   HTML ( 6 )   PDF (1903KB) ( 79 )  

    An aquifer that traps discontinuous and non-flowing air is called a quasi-saturated aquifer. The trapped air can reduce the permeability of the aquifer; however, the relationship between quasi-saturated hydraulic conductivity (Kq), trapped gas saturation (Sa-t), and displacement rate is not fully understood. In this study, a displacement experiment was conducted to illustrate the effect of displacement rate on Sa-t and Kq. Sa-t was found to generally decrease nonlinearly with increasing displacement rate and remained almost unchanged at the high or low displacement rate. This S-shaped curve can be mathematically expressed by a model similar to “van Genuchten equation”. Further, a linear negative correlation between Kq and Sa-t was found for sandy media. The two empirical models above imply that the displacement rate can be used to estimate Kq, which provides another approach for determining the Kq values. These hydraulic properties provide a basis for understanding quasi-saturated groundwater flow. In addition, the relationship between displacement rate and Sa-t showed that in experiments involving fully saturated porous media, the initial saturation rate should be greater than the initial capillary rise rate when measuring Sa-t to avoid air entrapment in the media.

    Figures and Tables | References | Related Articles | Metrics
    Evaluation of water resource multiple effect based on the analysis of water circulation: An example of the Beichuan River Basin upstream of the Yellow River
    ZHU Liang, LIU Jingtao, ZHANG Yuxi, LIU Dandan, JIAO Shizhe
    2022, 29(3): 263-270. 
    DOI: 10.13745/j.esf.sf.2022.1.27

    Abstract ( 305 )   HTML ( 7 )   PDF (3750KB) ( 107 )  

    To evaluate the effect of large-scale vegetation restoration on water resources in semi-arid areas, an evaluation model was created based on analysis of water circulation in watersheds in referencing to the Keynesian multiplier theory. Further, the variation trend of such effect with changing water circulation caused by vegetation restoration was evaluated from the perspective of generalized water resources. The water circulation conditions in the Beichuan River Basin have significantly changed owing to large-scale vegetation recovery. The surface flow coefficient before and after the vegetation recovery reduced from 0.254 to 0.207, and the base current coefficient reduced from 0.156 to 0.134 under nearly stable precipitation. The proportion of the effective water volume increased in the soil-vegetation system and decreased in the soil-groundwater system under terrestrial water circulation. The localized water resources response to 100 mm precipitation reduced by 6.55 mm; however, the generalized water responses response, with ecological response included, increased by 45.37 mm, or a 25.78% increase. Thus the change in water circulation significant increased water resources response to rainfall in the Beichuan River Basin. This changing trend of precipitation distribution in different water circulation sections as a result of vegetation recovery aligns well with the country’s core strategy for ecosystem conservation, and plays an important role in improving the overall water resources response to rainfall the semi-arid area.

    Figures and Tables | References | Related Articles | Metrics
    Simulation of Manas River runoff based on ERA5-Land dataset
    TANG Hao, WANG Xiaoyun, CHEN Fulong, JIANG Long, HE Chaofei, LONG Aihua
    2022, 29(3): 271-283. 
    DOI: 10.13745/j.esf.sf.2022.1.50

    Abstract ( 715 )   HTML ( 36 )   PDF (8016KB) ( 233 )  

    Meteorological data is a key factor in hydrological process research, and the development of reanalysis data provides a new solution for runoff simulation in data-scarce regions. In order to study the applicability of ERA5-Land reanalysis dataset in local runoff simulation, several evaluation indexes were selected to evaluate the accuracy of ERA5-Land precipitation and temperature in the Manas River basin above the Kanswat hydrological station, and the distribution characteristics of the two ERA5-Land components in the study area were analyzed by empirical orthogonal function (EOF). In terms of accuracy, ERA5-Land has a good correlation with measurement data. The precipitation detection rate was 0.96, which can reflect most precipitation events, but was 21.81% higher than the measured rate. The accuracy of temperature was better comparably, with better overall fitting accuracy, yielding an optimal range of -5-20 ℃, with increasing uncertainties near the extremum. The EOF deterministic mode showed that the precipitation and temperature flutuations in the study area followed basically the same trend, that is, they were susceptible to the influence of large-scale weather system. In the validation period, the Nash coefficients (NSE) were 0.88 and 0.82 for the final SWAT runoff models at daily and monthly scales, respectively. The ERA5-Land reanalysis dataset can provide a reference for runoff simulation in northwest China where measured meteorological data are lacking.

    Figures and Tables | References | Related Articles | Metrics
    Medium to long term runoff forecast for the Huai River Basin based on machine learning algorithm
    HU Yiming, CHEN Teng, LUO Xuyi, TANG Chao, LIANG Zhongmin
    2022, 29(3): 284-291. 
    DOI: 10.13745/j.esf.sf.2021.10.2

    Abstract ( 564 )   HTML ( 34 )   PDF (3473KB) ( 216 )  

    Accurate and reliable medium to long term runoff prediction is key to supporting scientific allocation of water resources and improving water resources utilization efficiency. In this study, the AdaBoost (AdB), Random forest (RF) and Support vector machine (SVM) algorithms were used to make medium to long term runoff predictions at the Wangjiaba and Bengbu stations, Huai River Basin, from November to October of the following year. The permutation accuracy importance measure was used to select the key factors affecting monthly runoff from 1562 factor variables constructed from 130 meteorological-climate factors and previous precipitation/runoff fluxes, and the monthly runoff forecasts based on the aforementioned three machine learning algorithms were made for each month, using model parameters determined by way of random search combined with cross-validation. The performances of the three algorithms were evaluated using the variable amplitude error qualification rate indicator and the grade (five level) forecast qualification rate indicator. The former indicator shows that the 12-month average qualification rates of prediction for the three algothrims at the Wangjiaba station were, respectively, 99.8% (AdB), 96.6% (RF) and 95.5% (SVM) and at the Bengbu station 100% (AdB), 94.8% (RF) and 93.8% (SVM); the results using the latter indicator at the Wangjiaba station were, respectively, 79.0% (AdB), 76.4% (RF) and 79.9% (SVM), and at the Bengbu Station 81.0% (AdB), 75.6% (RF) and 76.6% (SVM). The three machine learning algorithms all performed well, but RF and SVM had low prediction rates on high discharge values, and AdB performed better than RF and SVM overall.

    Figures and Tables | References | Related Articles | Metrics
    Gravity and magnetic anomaly in the southern Tanlu fault zone and its geological interpretation
    ZHENG Qifang, ZHENG Yuzhou, ZHAO Rui, KUANG Xingtao, ZHANG Wan, LIU Yinghui, XU Luping, WU Yun, ZHOU Daoqing
    2022, 29(3): 292-303. 
    DOI: 10.13745/j.esf.sf.2022.1.55

    Abstract ( 218 )   HTML ( 17 )   PDF (9701KB) ( 217 )  

    The differences between transverse and longitudinal magnetism or density on both sides of a fault are reflected in gravity and magnetic anomalies. Therefore, the gravity and magnetic anomaly data provide a scientific basis for in-depth studies of key geological research topics, such as the base properties, fault formation characteristics and magma distribution in the Tanlu fault zone. The 1∶50000 scale gravity and magnetic anomaly maps of the Tanlu fault zone were drawn using the up-to-date high-precision airborne gravity data, aeromagnetic data and ground gravity data. Combined with the regional geological data, the characteristics of gravity and magnetic anomalies were also analyzed. The results indicated the existence of an ancient conjoined Tanlu-Dabie structural belt, where the southern segment of the Tanlu fault zone reflects the magmatic activities in the Proterozoic-Middle Yanshan period, while the entire fault zone defines the boundary between the southern North China block and the Yangtze block in the Mesoproterozoic-Neoproterozoic era. A comparison of the magnetic and gravity anomaly maps showed an eastward expansion of the Hefei Basin over geological time.

    Figures and Tables | References | Related Articles | Metrics
    Formation mechanism of Hanxing type iron deposit: Evidence from the iron-bearing melt-fluid assemblage in porphyritic monzonite from Wu’an, Hebei Province
    YANG Yubo, SU Shangguo, HUO Yan’an, NING Yage, GU Dapeng
    2022, 29(3): 304-318. 
    DOI: 10.13745/j.esf.sf.2021.7.22

    Abstract ( 212 )   HTML ( 10 )   PDF (15711KB) ( 244 )  

    The formation mechanism of the Hanxing type iron deposit has been controversial. In order to resolve this issue, we conducted a detailed mineralogical and petrological study of the iron-bearing melt-fluid veins and plaques found in the porphyritic monzonite from Zhaozhuang area, Wu’an, Hebei Province, located in the metallogenic belt of Hanxing. The iron-bearing melt-fluid mineral assemblage showed obvious zonal pattern, with the mineral assemblages Di + Amp + Mt + Ap + Pl at the core and Prh + Cal at the edge. The magnetite in the assemblage had a well-defined zonal structure. At the core the TiO2 content was 2.23% and at the edge 0.36%-0.57%, while ∑REE was two orders of magnitude higher at the core than at the edge. The chondrite-normalized REE plot for the magnetite is a right dipping curve, suggesting its homology to the Wu’an intrusive rocks crystallized in a high temperature magmatic environment without fluid addition. The magnetite at the edge showed slight REE depletion and obvious negative Ce anomaly, indicating an addition of large amounts of volatile fluids in the crystallization environment. In the (Ti+V)-(Al+Mn) diagram, the magnetite from the assemblage fell under the same areas as porphyry-type and Fe-Ti- and V-type magnetites, and also between the areas of hydrothermal and magmatic magnetites. These results suggested that the iron-bearing melt-fluid is not distal skarn vein formed by metasomatic interaction between intrusive rock and wall rock, but rather a product of shallow crystallization of deep magma by the following proposed mechanism: First, high-Ti, REE-rich magnetite microcrystals are formed from deep magmatic fangtie pulp; then, as fluid overpressure is reached due to injection of fluid rich in volatile matter, the magnetite microcrystals are combined with bubbles and rise rapidly along the magmatic channel: eventually, low-Ti, REE-depleted magnetite is formed at depths of 1.55-2.19 km, then crystallized to form fluid crystal minerals such as amphibole.

    Figures and Tables | References | Related Articles | Metrics
    Cu-S Isotope characteristics and metallogenic prediction of orebodies in the Dajing Sn-Cu polymetallic deposit in Inner Mongolia
    WANG Yue, SU Shangguo, ZHANG Qi, ZHOU Qiming, ZHANG Yanan
    2022, 29(3): 319-328. 
    DOI: 10.13745/j.esf.sf.2021.11.5

    Abstract ( 210 )   HTML ( 18 )   PDF (4249KB) ( 161 )  

    The Dajing Sn-Cu polymetallic deposit in Inner Mongolia represents typical ore deposits in the Daxinganling metallogenic belt. The mining area is located in Linxi County, eastern Inner Mongolia, with geological conditions favorable for ore formation. Here, we studied Cu isotopes in chalcopyrite and S and Pb isotopes in chalcopyrite and pyrite orebodies. The measured δ65Cu value for chalcopyrite ranged from -0.46‰ to +0.32‰ overall, averaging at 0‰ with an average 2σ error of 0.03‰; the δ34S values for chalcopyrite and pyrite ranged from +0.076‰ to +3.00‰ overall, averaging at +1.83‰, with relatively high uniformity, showing magma associated S isotopic characteristics. The ranges of Pb isotopic ratios were small overall; specifically, 206Pb/204Pb ranged between 18.291-18.353, 207Pb/204Pb between 15.501-15.574, and 208Pb/204Pb between 38.051-38.265. Together with previous studies in the region we show that, in the Dejing deposit, Cu isotopic changes occur during the sulfide-magma differentiation process. The δ65Cu variation pattern in chalcopyrite may indicate the direction of evolution of ore-forming sulfides in the mineralization stage. For instance, the direction of gradual δ65Cu value decreasing may point to concealed orebody. In the study area of the Dejing deposit, the mining district in the east shares similar Cu isotopic characteristics with the non-production target area of its periphery, where, according to Cu isotope evidence, may exist deep concealed orebodies.

    Figures and Tables | References | Related Articles | Metrics
    Cyclostratigraphy of the Devonian/Carboniferous boundary sections in South China
    LI Shan, WU Huaichun, FANG Qiang, XU Junjie, SHI Meinan
    2022, 29(3): 329-339. 
    DOI: 10.13745/j.esf.sf.2021.12.1

    Abstract ( 373 )   HTML ( 13 )   PDF (7085KB) ( 245 )  

    The Devonian/Carboniferous transition is one of the most important intervals in Earth’s history characterized by the greenhouse-icehouse transition and mass extinction. To understand this event, an accurate and high-resolution geochronological framework is needed. In this paper, high-resolution magnetic susceptibility is used as the paleoclimate proxy to study the cyclostratigraphy of the deep-water sequences across the Devonian/Carboniferous boundary (DCB) in the Muhua II and Daposhang sections, Changshun County, Guizhou Province, and the Duli section, Nandan County, Guangxi Zhuang Autonomous Region. The sedimentary cycles with thicknesses of 1.09-2.39 m, 0.29-0.73 m, and 0.18-0.51 m were interpreted as short eccentricity, obliquity, and precession cycles, respectively. After astronomical calibration of short eccentricity to 100 ka, the obliquity and precession periods of late Devonian were estimated to be 27.2-32.2 ka and 15-20.9 ka, respectively. The conodont zones and Hangenberg Crisis near the DCB were constrained by the newly constructed astronomical time scale in combination with the published U-Pb radioactive isotope age. The new DCB age, constrained by high-precision cyclostratigraphic correlation among different sections, was estimated to be 359.58±1.9 Ma.

    Figures and Tables | References | Related Articles | Metrics
    Sedimentary characteristics and genesis of thick conglomerate in the middle section of Xiguayuan Formation, Luanping Basin: Insight from a consecutive coring study of well LY1
    WANG Cheng, JIANG Zaixing, KONG Xiangxin, ZHANG Yuanfu, ZHANG Jianguo, YUAN Xiaodong, LIU Xiaoning
    2022, 29(3): 340-355. 
    DOI: 10.13745/j.esf.sf.2021.9.37

    Abstract ( 312 )   HTML ( 8 )   PDF (20149KB) ( 146 )  

    In order to investigate the sedimentary characteristics, genetic mechanism and controlling factors of thick conglomerate in continental rift basins, and to find favorable exploration target, the thick conglomerate in the middle section of the Xiguayuanzu Formation, Luanping Basin, is taken as the research object. According to theory of sedimentation, combined with logging, core, thin sections and test data, the lithofacies, lithofacies assemblage, sedimentary structure, electrical property and magnetic susceptibility of the thick conglomerate were analyzed. The thick conglomerate appears to be wrapped by black shale, where, due to sudden deformation, contacts with black shale are made at the top and bottom of the conglomerate; whilst the occurrences of abundant pyrite and some sensitive elements in the core reflect a strong reductive environment under hypoxia, indicating the conglomerate is in a deep water environment. Based on the genetic differences, two types of gravity flow-slide and slump-were identified. The sliding deposition includes 6 lithofacies and 4 lithofacies assemblages, whose main identification marks are the main and secondary sliding surfaces, high angle bedding, small positive fault and reverse fault in the layer. The slumping deposition also includes 6 lithofacies and 4 lithofacies assemblages and the main identification marks include the sliding surface, collapse deformation structure, convolute bedding, water escape structure, deformed gravel and partial primary bedding (graded bedding). The sliding deposition process is further divided into four stages according to the development position of the sliding surface, the amplitude variation characteristics of the gamma-ray curve and the acoustic wave curve. In the period of the Xiguayuan Formation, the slope fold zone on the edge of the basin, the supply of material source and certain trigger mechanism in the basin jointly control the formation of the deep water slide-slump gravity flow. Combining this control mechanism with the results of lithofacies analysis, the development mode of slide-slump gravity flow in the lacustrine steep slope zone of continental rift basin could be established.

    Figures and Tables | References | Related Articles | Metrics
    Neoproterozoic glaciations in Yecheng area, southwestern margin of the Tarim Basin
    LI Wangpeng, LI Huili, WANG Yi, LIU Shaofeng, ZHANG Zhongpei, YANG Weili, CAI Xiyao, QIAN Tao, LI Xiaojian
    2022, 29(3): 356-380. 
    DOI: 10.13745/j.esf.sf.2021.6.30

    Abstract ( 230 )   HTML ( 12 )   PDF (10750KB) ( 190 )  

    The Neoproterozoic glacial events record significant geological information of the Snowball Earth. In the Tarim Basin Neoproterozoic outcrops are well developed along the basin margin, making it an ideal research base for studying Neoproterozoic glaciations. The age of the Neoproterozoic diamictite along the northeastern margin of the basin is constrained from a series of well developed Neoproterozoic volcanic rocks in the Quruqtagh area; however, such constraints are lacking for other basin margin areas due to infrequent reporting of chronology data, which leads to disagreements when comparing glacial events. This project selects the minimally studied Neoproterozoic diamictite along the southwestern margin of the Tarim Basin to perform a multidisciplinary, comprehensive analysis of the mineral's petrology, isotopic chronology and lithogeochemistry of the deposit so as to determine its glacial deposition characteristics and deposition time as well as to better understand the paleoclimatic weathering conditions. The Nanhua Bolong and Sinian Yutang Formations with low CIA (chemical index of alteration) values represent two distinct episodes of Neoproterozoic glaciations. Detrital zircon U-Pb chronology of the glacial deposits and adjacent beds indicate the starting time of the Bolong glaciation is later than (710±13) Ma and corresponds to the global Sturtian glaciation, and the starting time of the Yutang glaciation is no earlier than (656±18) Ma while its termination time can be constrained by the age of the top boundary of the Nanhuan System (635 Ma) or the detrital zircon U-Pb age of the overlying Sinian System Kulkark Formation (634±9) Ma, which corresponds to the global Marinoan glaciation.

    Figures and Tables | References | Related Articles | Metrics
    Characterization of the trace fossil Teredolites longissimus (Apectoichnus longissimus) from the Eocene La Meseta Formation, Seymour Island, Antarctic Peninsula
    LI Ruoshuang, LI Quanguo
    2022, 29(3): 381-391. 
    DOI: 10.13745/j.esf.sf.2021.7.23

    Abstract ( 333 )   HTML ( 14 )   PDF (9020KB) ( 151 )  

    The ichnogenus Teredolites, produced by wood-boring marine bivalves (Teredinidae or Pholadidae), describes trace assemblage of club-shaped borings in log-ground in marine strata. Teredolites are taphonomically indicative of shallow marine environments, thus they can provide valuable information on the taxonomy and distribution of wood substrates as well as the environmental setting during the burial. This article investigates the trace fossil Teredolites longissimus (Apectoichnus longissimus) discovered in the upper part of the La Meseta Formation of Seymour Island, Antarctic Peninsula. The age of this horizon is constrained in the Late Eocene and the development and distribution features of teredinid body fossils preserved in the wood substrate indicate an incipient stage of infestation. Wood substrate and teredinid body fossils were investigated thoroughly using field emission scanning electron microscope (FESEM) and energy dispersive X-ray spectrometer (EDS). The xylic substrate was identified as Phyllocladoxylon sp. of family Podocarpaceae, which confirmed the existence of Phyllocladoxylon had lasted until the Late Eocene in Seymour Island. Framboidal pyrite was discovered in abundance inside teredinid body fossils, 39.2% of the framboids were above 10 μm in grain size, and the maximum grain size reached 44 μm; the size distribution analysis indicated they were formed under oxic condition, suggesting the paleo-ocean in the Antarctic Peninsula area was oxic at the end of the Eocene.

    Figures and Tables | References | Related Articles | Metrics