Drying increases organic colloidal mobilization in the karst vadose zone: Evidence from a 15-year cave-monitoring study     

Jin Liao  Chaoyong Hu  Xiuli Li  Jiaoyang Ruan 《水文研究》2021,35(4):e14163

Understanding the hydrological processes of colloids within the karst vadose zone is vital to the security of karst groundwater and providing appropriate paleohydrological explanations of colloid-facilitated metals in speleothem. This study addresses the mobilization mechanisms driving colloidal organic matter (COM) transport in the karst vadose zone using a 15-year long monthly monitoring dataset from a cave drip point (HS4) in Heshang Cave, Qingjiang Valley, China. Variations in COM concentrations were reported as the fluorescence difference values of raw and filtered (<0.22 μm) samples at an excitation wavelength of 320 nm and emission wavelength of ~400 nm. A fluorescence humification index (HIX) lower than 0.8 and an autochthonous index (BIX) higher than 1.2 indicated that the origin of COM was mainly from the karst vadose zone, rather than the soil zone. The COM concentration varied from 0.001 to 0.038 Raman Unit (RU), with evident seasonal fluctuations. Rising limbs for COM values occurred prior to rising limbs within a dripwater hydrograph; moreover, the COM peak values corresponding to the beginning of the increasing hydrograph generally suggested that the mobilization of COM reflected the movement of the air–water interface (AWI) in the karst vadose zone rather than rainfall intensity or flow velocity. COM peak values were positively correlated with the antecedent drying duration and negatively correlated with HIX values. These phenomena may be explained by the increased amount of organic matter that was aggregated and absorbed on the surface of carbonate in the karst vadose zone during a longer drying duration. Moreover, the longer drying duration was also beneficial to autochthonous biological activity, which subsequently decreased the HIX value of the organic matter in the karst vadose zone. The movement of AWI and the drying duration are both controlled by the outside weather conditions. This study is therefore conducive to evaluating the security of karst groundwater in response to climate change, and challenges prevailing paleoclimate interpretations of colloid-facilitated metal abundance timeseries reported from speleothems.  相似文献   

2020年1月19日新疆伽师MS6.4地震InSAR同震形变场特征及发震构造初步探讨     

温少妍  李成龙  李金 《内陆地震》2020,(1):1-9

基于Sentinel-1 SAR升、降影像,利用D-InSAR技术获取新疆伽师M S6.4地震的同震形变场,结果表明,本次地震引起的同震形变场整体呈近椭圆状分布,形变区东西长约66 km,南北宽约40 km,整个形变场由南部隆升区和北部沉降区组成,南部最大隆升量约7 cm,北部最大沉降量约3 cm。本次地震发生在块体俯冲界面处的低倾角逆冲推覆构造带上,隆升和沉降两个中心均位于逆冲推覆体的上盘,形变主要以隆升形变为主,符合低倾角逆断层中强震的变形特征。在沉降区与隆升区之间干涉条纹连续分布,未出现表征地表破裂位置的空间失相关带,表明地震未引起明显的地表破裂。结合震源机制、余震精定位及区域构造特征,初步推断认为伽师地震的发震构造可能为柯坪塔格推覆构造前缘的N倾的柯坪断裂。  相似文献   

A 2D discrete heat transfer model considering the thermal resistance effect of fractures for simulating the thermal cracking of brittle materials     

Yan  Chengzeng  Jiao  Yu-Yong 《Acta Geotechnica》2020,15(5):1303-1319

Acta Geotechnica - A concise, two-dimensional discrete heat transfer model is presented, which considers the thermal resistance effects of cracks. The discrete heat transfer model discretizes the...  相似文献   

Orbital control on cyclical organic matter accumulation in Early Silurian Longmaxi Formation shales     

Siding Jin  Hucheng Deng  Xing Zhu  Yan Liu  Sibing Liu  Meiyan Fu 《地学前缘(英文版)》2020,(2):533-545

High resolution(939 samples)total organic carbon content(TOC)analyses were conducted on the Shuanghe Section of^152.6 m in the Changning area,Sichuan Basin.The sampling section was divided into two units considering the distinct-different deposit environment and sediments accumulation rate.The lower part(Unit 1)and the peer part(Unit 2)with high resolution sample spacing(0.08–0.4 m)enables the identification of the precession cycle in two sedimentary sequences with distinct different sedimentary accumulation rate.MTM Power spectral analyses on untuned TOC series reveals significant peaks exceeding above the 95%confidence level and shows that both Unit 1 and Unit 2 have recorded Milankovitch cycles of 405 kyr long eccentricity,short eccentricity,obliquity and precession.The floating astronomical time scale(ATS)was constructed on the Shuanghe Section in the Early Silurian(~439.673–444.681 Ma),and which was calibrated by 405 kyr long eccentricity cycles.The total duration of the Wufeng and Longmaxi shales is 5.01 Myr.The floating ATS used for estimating the duration of the graptolite zones and each stage in the study interval.Finally,we postulated two models that could verify the linkage between orbital cycle and organic accumulation.To make sure whether productivity or preservation is the main factor that under long eccentricity control,the phase correlation between the obtained filtered signal and the theoretical orbital solution should be made clear in the further research.  相似文献   

CG-6型重力仪零漂特性研究     

郝洪涛  刘少明  韦进  胡敏章 《大地测量与地球动力学》2019,39(10):1086-1090

对中国地震局地震研究所最新引进的4台CG-6型相对重力仪的零漂特性进行测试研究，结果表明，4台重力仪的静态零漂率、混合零漂率和动态零漂率均小于8 μGal/h，满足厂家给出的技术指标。在较长观测时间内，各台仪器的零漂均存在不同程度的非线性特征，因此在进行较长时间的野外观测以及后续数据处理中，不宜将零漂率作为常数进行解算和零漂改正。  相似文献   

琼东南盆地华光凹陷天然气水合物稳定带厚度的影响因素     

刘杰  杨睿  邬黛黛  金光荣  张辉 《海洋学报》2019,41(8):13-25

为了探讨琼东南盆地华光凹陷海底天然气水合物稳定带的分布规律，定量研究了静水压力、底水温度、地温梯度和气源组分对水合物稳定带的影响程度。在此基础上，分析了华光凹陷现今甲烷水合物稳定带的厚度分布。最后，综合各因素的历史演化过程，初步探讨了华光凹陷1.05 Ma BP以来天然气水合物稳定带的演化。结果表明:(1)气源组分和海底温度的变化对研究区内水合物稳定带的影响较大；水合物稳定带厚度与海底温度呈良好的线性负相关性。(2)水深超过600 m的海域具备形成天然气水合物的温压条件；超过600 m水深的海域水合物稳定带厚度大部分超过 100 m，其中西北部稳定带的最大厚度超过300 m，是有利的水合物勘探区。(3)华光凹陷1.05 Ma BP以来天然气水合物稳定带厚度经历了快速增厚–窄幅变化–快速减薄和恢复的过程。麻坑群与水合物稳定变化敏感区在空间上具有较好的叠合关系。结合前人的研究成果，推测其形成与天然气水合物的分解释放有关。  相似文献   

腾冲火山及周边地区双差层析成像          下载免费PDF全文

华雨淋  吕彦 《地球物理学报》2019,62(8):2982-2990

利用云南腾冲火山地区15个固定台站记录到的7923次地震的P波到时资料，采用双差层析成像方法，反演得到腾冲火山及周边地区地壳及上地幔顶部三维P波速度结构和地震重定位结果.研究发现，腾冲火山区域地壳内存在明显的地震波低速区，P波速度低于整个区域地壳速度平均值超过15%，上地幔顶部存在规模较大的低速异常区.推测腾冲火山地区存在较大规模的地幔热物质上涌以及向地壳的侵入，热物质在地壳内以岩浆囊形式存储，并且壳内岩浆囊之间可能存在岩浆通道.通过联合反演获得的地震重定位结果显示，丛集地震位置更加集中，其展布特征与断裂构造具有显著的对应关系，表明研究区域断裂构造比较活跃.获得的高分辨率三维P波层析成像结果，为进一步认识火山地区岩浆存储特征以及地震分布与区域构造之间的关系提供了新的地震学依据.  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   

不同结构林带防风效能风洞模拟     

李晓烨  王克俭  谷建才  刘启国  崔严 《中国沙漠》2019,39(6):118-125

防风林带结构是影响防风效能的主要因素。建立不同宽度、不同株行距林带防风效能与林带后距离之间的统计模型，可以为防风林建设提供指导性意见。通过风洞实验，在11 m·s^-1风速下，对4种宽度、5种株行距林带的背风面0~10H（H为林带高度）的风速进行测定，采用曲线参数估计法、傅立叶模型、SSF模型（Sum of Sin Functions），构建了不同结构林带防风效能与林带后距离间的统计模型。结果表明：傅立叶模型拟合不同宽度林带的防风效能与林带后距离的关系效果最优，可决系数（R²）均在98%以上；SSF模型拟合不同株行距林带的防风效能与林带后距离的关系效果最优（R²>0.98）。根据构建的统计模型，风速为11 m·s^-1左右时，林带宽度8 m（两行一带）的防风林的防风效能存在明显优势；5种株行距的林带中，株行距为8 m×8 m的防风林带本试验条件下防风效果最好。  相似文献   

山东大尹格庄金矿床深部三维定量成矿预测     

陈进  毛先成  邓浩 《地球学报》2020,41(2):179-191

大尹格庄金矿是胶西北招平断裂带中段的大型金矿床,但随着逐渐的开采其保有资源量不断下降,急需在矿床的深边部区域开展接续资源找矿工作。本文以大尹格庄金矿为研究对象,以区域成矿理论和找矿勘查模型为指导,利用三维地质建模技术构建了相关地质体的三维模型,在此基础上,采用定量化的方法提取地质体与成矿相关的控矿因素指标和矿化指标,并建立了三维定量成矿预测模型,并应用该模型圈定了3个找矿靶区。研究表明,该方法能够适用于大中型矿山的深边部找矿工作,其三维及定量化的预测结果能够为后续的勘探及开采工作提供重要参考。  相似文献