Origin of sulphate in the unsaturated zone and groundwater of a loess aquifer     

Yin Long  Tianming Huang  Fen Zhang  Zhenbin Li  Baoqiang Ma  Yiman Li  Zhonghe Pang 《水文研究》2021,35(4):e14166

The use of the sulphate mass balance (SMB) between precipitation and soil water as a supplementary method to estimate the diffuse recharge rate assumes that the sulphate in soil water originated entirely from atmospheric deposition; however, the origin of sulphate in soil and groundwater is often unclear, especially in loess aquifers. This study analysed the sulphur (δ³⁴S-SO₄) and oxygen (δ¹⁸O-SO₄) isotopes of sulphate in precipitation, water-extractable soil water, and shallow groundwater samples and used these data along with hydrochemical data to determine the sources of sulphate in the thick unsaturated zone and groundwater of a loess aquifer. The results suggest that sulphate in groundwater mainly originated from old precipitation. When precipitation percolates through the unsaturated zone to recharge groundwater, sulphates were rarely dissolved due to the formation of CaCO₃ film on the surface of sulphate minerals. The water-extractable sulphate in the deep unsaturated zone (>10 m) was mainly derived from the dissolution of evaporite minerals and there was no oxidation of sulphide minerals during the extraction of soil water by elutriating soil samples with deionized water. The water-extractable concentration of SO₄ was not representative of the actual SO₄ concentration in mobile soil water. Therefore, the recharge rate cannot be estimated by the SMB method using the water-extractable concentration of SO₄ in the loess areas. This study is important for identifying sulphate sources and clarifying the proper method for estimating the recharge rate in loess aquifers.  相似文献   

韩国“新北方政策”对接“一带一路”倡议：机遇与挑战     

庞加欣  王灵桂 《热带地理》2019,39(6):911-918

韩国“新北方政策”与“一带一路”倡议的对接合作为中韩两国带来了重要发展机遇。文章主要探讨韩国“新北方政策”的内涵及其与“一带一路”倡议对接的进展、机遇与挑战,得出双方对接的合作机遇主要在政策沟通、设施联通、贸易投资和资金融通4个方面,同时也存在着制度性风险、地缘风险和投资合作风险的三大挑战。在具体对接过程中,产业、金融、物流3个领域可能成为突破口。  相似文献   

天津市公众地震科普认知与需求调查     

王萍  闫丽莉  庞群英  安纯毅 《震灾防御技术》2020,15(3):601-608

为真实了解天津市公众地震科普认知与需求情况，以天津市机关单位工作人员、企业员工、事业单位工作人员、大学生、中小学生、社区居民、农民、驻津部队、残障人士等特殊人群为研究对象，开展专项问卷调查与分析。调查结果显示，天津市公众地震科学知识与地震科普工作的认知度与需求度较高，但仍存在地震科学知识掌握不全面、地震科普产品吸引力不足、科普渠道相对单一等问题，地震科普工作在参与性、互动性与趣味性等方面仍有较大提升空间。基于此，提出提高地震科普工作针对性和有效性及地震科普服务个性化和精准化等建议。  相似文献   

基于手机位置数据的地震灾情指标选择     

庞晓克  聂高众  张昕  李华癑  夏朝旭  范熙伟  魏本勇 《中国地震》2019,35(1):144-157

选取四川阿坝州九寨沟县MS7.0地震、新疆博尔塔拉州精河县MS6.6地震、四川广元市青川县MS5.4地震作为案例分析,绘制活跃Wi Fi数量、无线网络联网设备数量、汇总在线设备数量、活跃基站数量等4种地震灾情指标在地震发生前后数量变化的折线图。根据与地震前1天变化情况的对比分析,验证地震灾情指标的可用性,选取出效果好的指标,这对进一步研究震后快速获取极震区位置、影响场方向等具有重要意义。  相似文献   

湖北宜昌重要地质遗迹资源特征及发展模式探讨     

阎春波  李姜丽  赵璧  程龙 《地质论评》2021,67(6):67112006-67112006

本文系统总结了湖北宜昌地区省级及省级以上地质遗迹资源,认为该地区地质遗迹分布规律主要可概括为两个方面,一是受控于地形和河流的综合作用,以各类地貌景观遗迹为特点;二是各个地质时代地层剖面齐全,古生物化石产地聚集。其中可归类为世界级地质遗迹点为5个,均以“古生物化石”为核心,分别为三峡地区埃迪卡拉生物群、长阳寒武纪清江生物群、黄花场中奥陶统大坪阶“金钉子”、王家湾上奥陶统赫南特阶“金钉子”和远安三叠系南漳—远安动物群。立足于此,文中首次详细总结了这些地质遗迹点的化石代表、科学及科普意义,并从地质遗迹自身保护和应用方式、地质遗迹载体、地学研学、地质文化的传播和文创科普产品5个方面对古生物地质遗迹资源的发展模式进行了详细探讨,从而为宜昌地区全域地质遗迹开发和旅游提供新思路。  相似文献   

基于DBSCAN与网格搜索的雷电定位算法          下载免费PDF全文

梁丽  雷勇  张帅弛  李涛  庞文静  王志超 《应用气象学报》2019,30(3):267-278

定位精度是评价雷电定位网络的重要指标之一,定位算法直接影响雷电探测结果的精度。雷电监测系统探测数据误差不可避免,传统定位算法不具备抗误差干扰能力,迭代计算易发散,定位结果精度不高。为了满足实际应用需求,提出一种新的雷电定位算法DG-LLA（DBSCAN and grid-search lighting location algorithm）,在定位计算中引入DBSCAN（density-based spatial clustering of applications with noise）方法与网格搜索方法。通过仿真与国家雷电监测网实际定位结果对比分析定位算法性能。结果表明:到达时间差（time difference of arrival,TDOA）法和Taylor级数展开法定位误差较大,仿真区域的均方根误差分别为982 m和668 m;定位中引入DBSCAN方法后,均方根误差明显减小为406 m,引入DBSCAN方法和网格搜索方法后,均方根误差减小为349 m;在相同回击数据条件下,算法DG-LLA与国家雷电监测网相比定位数量更多,回击数据的利用率从43.4%提升到51.5%,新增定位结果周围雷达回波特征较强,定位精度更高。  相似文献   

Critical conditions for natural gas charging and delineation of effective gas source rocks for tight sandstone reservoirs     

Fujie Jiang  Xiongqi Pang  Fengtao Guo  Jigang Guo 《Geological Journal》2016,51(1):113-124

Although it has been shown that the potential of tight‐sand gas resources is large, the research into the mechanisms of hydrocarbon charging of tight sandstone reservoirs has been relatively sparse. Researchers have found that there is a force balance during hydrocarbon charging, but discriminant models still have not been established. Based on the force balance conditions observed during gas migration from source rocks to tight sandstone reservoirs, a calculation formula was established. A formula for identifying effective source rocks was developed with the gas expulsion intensity as the discrimination parameter. The critical gas expulsion intensity under conditions of various burial depths, temperatures, and pressures can be obtained using the calculation formula. This method was applied in the Jurassic tight sandstone reservoirs of the eastern Kuqa Depression, Tarim Basin, and it was calculated that the critical expulsion intensity range from 6.05 × 10⁸ m³/km² to 10.07 × 10⁸ m³/km². The critical gas charging force first increases with depth and later decreases with greater depths. The distribution range of effective gas source rocks and total expelled gas volume can be determined based on this threshold. This method provides new insight into and method for predicting favourable tight‐sand gas‐bearing regions and estimating their resource potentials. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Hydrocarbon generation and expulsion characteristics of Lower Permian P1f source rocks in the Fengcheng area,northwest margin,Junggar Basin,NW China: implications for tight oil accumulation potential assessment     

Tao Hu  Xiongqi Pang  Sa Yu  Xulong Wang  Hong Pang  Jigang Guo  Fujie Jiang  Weibing Shen  Qifeng Wang  Jing Xu 《Geological Journal》2016,51(6):880-900

Combined with the actual geological settings, tight oil is the oil that occurs in shale or tight reservoirs, which has permeability less than 1 mD and is interbedded with or close to shale, including tight dolomitic oil and shale oil. The Fengcheng area (FA), at the northwest margin of the Junggar Basin, northwest China, has made significant progress in the tight oil exploration of the Fengcheng (P₁f) Formation recently, which indicates that the tight oil resources have good exploration prospects. Whereas the lack of recognition of hydrocarbon generation and expulsion characteristics of Permian P₁f source rocks results in the misunderstanding of tight oil resource potential. Based on the comprehensive analysis of geological and geochemical characteristics of wells, seismic inversion, sedimentary facies, tectonic burial depth, etc., the characteristics of P₁f source rocks were investigated, and the horizontal distributions of the following aspects were predicted: the thickness of source rocks, abundance and type of organic matter. And on this basis, an improved hydrocarbon generation potential methodology together with basin simulation techniques was applied to unravel the petroleum generation and expulsion characteristics of P₁f source rocks in FA. Results show that the P₁f source rocks distribute widely (up to 2039 km²), are thick (up to 260 m), have high total organic content (TOC, ranging from 0.15 to 4 wt%), are dominated by type II kerogen and have entered into low mature–mature stage. The modeling results indicate that the source rocks reached hydrocarbon generation threshold and hydrocarbon expulsion threshold at 0.5% Ro and 0.85% Ro and the comprehensive hydrocarbon expulsion efficiency was about 46%. The amount of generation and expulsion from the P₁f source rocks was 31.85 × 10⁸ and 15.31 × 10⁸ t, respectively, with a residual amount of 16.54 × 10⁸ t within the source rocks. Volumetrically, the geological resource of shale oil is up to 15.65 × 10⁸ t. Small differences between the amounts calculated by the volumetric method compared with that by hydrocarbon generation potential methodology may be due to other oil accumulations present within interbedded sands associated with the oil shales. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

鄂尔多斯盆地中及上三叠统延长组沉积相与油气勘探的突破   总被引：5，自引：1，他引：4  

邓秀芹  付金华  姚泾利  庞锦莲  孙勃 《古地理学报》2011,13(4):443-455

鄂尔多斯盆地位于中国的中西部,跨陕、甘、宁、蒙、晋5省区,盆地本部面积25万km2.中及上三叠统延长组在盆地内广为展布,厚逾千米,发育冲积扇、河流、三角洲、湖泊等沉积相,是该地区重要的油气产层.根据盆地腹地100多口井的钻井资料及盆地周边地区的露头资料,以及长庆油田长时期对延长组的油气勘探经验,编制出了鄂尔多斯盆地中及...  相似文献   

Sedimentary and hydrological studies of the Holocene palaeofloods in the Shanxi-Shaanxi Gorge of the middle Yellow River,China     

Xiaogang Li  Chun Chang Huang  Jiangli Pang  Xiaochun Zha  Yugai Ma 《International Journal of Earth Sciences》2015,104(1):277-288

  相似文献