Processes controlling dripwater hydrochemistry variations in Xueyu Cave,SW China: implications for speleothem palaeoclimate signal interpretations

Cave dripwater hydrochemistry responds to environmental changes, both within and outside of the cave, and thereby conveys this information to any stalagmite fed by the drips. As stalagmites are important archives of climate proxy information, understanding how dripwater hydrochemistry responds to environmental forcing is critical. However, despite the large number of speleothems in SW China, the response of dripwater to regional climate variability is not yet adequately understood. A 3‐year study of three drip sites in Xueyu Cave, Chongqing Municipality, SW China, revealed the most important mechanisms controlling dripwater chemical variability. The principal chemical indices (pH, specific conductivity, Ca²⁺, Mg²⁺, Sr²⁺ and ) in collected dripwaters and the local climate data were analysed in this study. The principal controls on the hydrochemistry were found to be the external climate and its changes, groundwater residence time, cave ventilation and prior calcite precipitation (PCP) processes. Dripwater hydrochemistry showed strongly coherent seasonal patterns despite the fact that all sites are Ca–HCO₃ type waters and supersaturated with calcite. Seasonal changes in dripwater hydrochemistry were influenced by the soil and vadose zone CO₂ content as well as groundwater residence time in the upper karst zone. Cave‐air CO₂ seasonal variations were consistent with changes in dripwater PCO₂ and cave ventilation. Trace element ratios (Mg/Ca and Sr/Ca) of dripwater were controlled by PCP processes. Seasonal variations in dripwater Mg/Ca and Sr/Ca ratios in Xueyu Cave showed inverse changes with the Asia Monsoon Index during the monitoring period, reflecting the seasonal climate changes that may have been recorded in the speleothems. Based on a linear regression of PCO₂ and the Ca²⁺ data in the cold–dry winter season, a 130‐ppm shift in cave‐air PCO₂ results in a 1‐ppm shift in dripwater Ca²⁺ concentration in Xueyu Cave. This study illustrates the importance of understanding factors controlling the changes in the composition of dripwater before it reaches the speleothem.     

Sources and transports of organochlorine pesticides in the Nanshan underground river,China

Karst areas have much higher ecological vulnerability and are prone to be contaminated. Organochlorine pesticides (OCPs) were detected in waters and sediment from the two sites of the karst Nanshan underground river system, China, to understand the sources and transport of OCPs in the underground river systems. Obviously, seasonal variations were found both in the waters and the sediments. Detected OCPs ranged from 61 to 936 ng L^?1 in the groundwaters and 51–3,842.0 ng g^?1 in the underground sediments, respectively. OCPs in groundwaters were mixture of younger and older residues from commercial sources. The maximum OCPs in the sediments of the underground river were historically older residues from commercial sources. The sources of OCPs in the waters and sediments of the underground river indicated that the surface systems play an important role in OCPs transport and pollution in the underground river. Karst features were liable for the transport behavior.     

南岭东段岩前钨矿床地质特征及成岩成矿时代

岩前钨矿位于南岭东西向构造与滨太平洋北北东向构造带的交汇复合部位,南岭成矿带东段北部。主要矿床类型有矽卡岩型白钨矿和石英脉型黑钨矿,矿体产于燕山早期花岗岩内外接触带内。在区域地质和矿床地质研究的基础上,采用LA-ICP-MS 锆石U-Pb 法和辉钼矿Re-Os等时线方法,对与成矿关系密切的岩前花岗岩和含矿石英脉中辉钼矿进行精确定年,获得花岗岩的单颗粒锆石U-Pb谐和年龄加权平均值为(160.6±0.72) Ma,黑钨矿化石英脉中的辉钼矿为(159.2 ±2.3) Ma。这一成果揭示,花岗岩的就位年龄与含矿石英脉的形成几乎在相同热过程完成。结合前人研究,进一步得出南岭地区160~150 Ma成岩成矿作用主要分布于南岭中东段,成岩成矿作用与华南地区东部岩石圈大规模伸展的构造运动力学背景有关。岩前钨矿与区内盘古山、画眉坳、柿竹园等著名矿床具有相同的成矿时代、成矿背景和相似的成矿条件,属同一个成矿亚系列,预测岩前钨矿具有较大的找矿潜力,重点突破对象为内接触带石英脉型和接触交代矽卡岩型钨多金属矿体。     

基于统计损伤的岩爆预测

基于岩石单轴抗压强度的分布特征,对脆性岩石采用统计损伤的平行杆模型模拟,经岩石全过程曲线拟合,表明了 模型的合理性。进而提出采用平行杆模型模拟地下深埋洞室脆性围岩,推出了不同应力条件下岩体损伤的表达式,从统计损 伤的概念上,利用损伤变量来表征岩爆发生概率。工程实例分析表明该预测方法是有效的。     

祁县井水温和水位的奇异潮汐关系探讨

山西祁县井水温潮汐相位超前于水位,异于正常的水温和水位潮汐的动态关系。本文介绍了此现象的记录图像,通过水温和水位同震响应数据核实仪器时间系统,证实此现象是客观的;利用调和分析方法计算出逐月水温与水位潮汐变化的时间差,表明此现象存在于整个观测中。根据水温和水位潮汐相位相关性分析及观测条件调查,认为祁县井水温潮汐相位超前于水位的现象是在特定观测条件下,因井水流动不畅引起的特殊的水温水位关系。     

陆相烃源岩凝析油形成演化实验模拟特征

为了解陆相烃源岩在深埋过程中凝析油形成与演化特征,利用高温高压生烃模拟仪对辽河盆地西部凹陷曙13 井、马南603 井和东部凹陷桃10 井烃源岩样品进行了半封闭体系生烃模拟实验。实验结果显示,I 型有机质（曙13 井烃源岩样品） 总凝析油产率峰值为2.32 mg/g TOC,出现在镜质体反射率（VR） 1.76 %Ro,并以低分子量烃类物质为主要成分,可能表明I 型有机质凝析油主要通过液态烃二次裂解形成。II 型有机质（马南603 井烃源岩样品） 总凝析油产率峰值为2.28 mg/g TOC,该峰值出现在VR 为2.42 %Ro,明显晚于I 型有机质凝析油产率峰值,其成分以相对高分子量的烃类物质为主,其次为低分子量烃类物质。III 型有机质（桃10 井烃源岩样品） 凝析油总产率最低,产率峰值仅为0.92 mg/g TOC,可能表明III型有机质生成凝析油潜力较差。     

海岸三维潮流数学模型的研究及应用

本模型以三维Navier－Stokes方程为基础,经σ-坐标变换得模式方程,然后选用特殊的插值函数,利用有限元和差分相结合的方法求解.所建模型可适应具有较为复杂岸线和海工建筑的海域潮流计算,可进行局部加密,同时能以较高分辨率揭示三维潮流的空间结构特征.本潮流模型具有省时、简便的特点.     

分步分层拟三维水流数学模型及其在廉州湾潮流计算中的应用

以Navier-Stokes方程为基础,经代数坐标变换导出模式方程,然后在该坐标系下将三维流场进行垂直分层,并在每一层内积分模式方程。在数值模拟求解方面,采用分步、特征差分近似与Galerkin集中质量有限元相结合的方法进行求解。在实际应用方面,对广西廉州湾潮流进行了三维模拟计算。     

Spatial and temporal groundwater dynamics in extreme arid basins

To accurately obtain the spatial distribution characteristics of groundwater level in an extremely arid zone and its dynamic change patterns under the influence of human activities, based on the data of 55 groundwater observation wells in the middle and lower reaches of the Kriya River, spatial interpolation of regional groundwater level data were performed using the inverse distance weight, spline function, trend surface, and the ordinary kriging methods. The optimal interpolation method was selected by its accuracy to spatially interpolate the groundwater level data in the study area from 2019 to 2021. The results show that: (1) the ordinary kriging method has the highest interpolation accuracy (MAE = 7.1393, MRE = 0.0058, RMSE = 9.4314) and reflects the spatial and temporal variability and distribution characteristics of groundwater levels with great accuracy. (2)The relationship between surface water–groundwater recharge and discharge in different areas of the river channel in the desert section varies depending on geological structure, surface water seepage, and other elements. (3) Groundwater in the Taklamakan Desert has little effect on groundwater recharge in the Dariyabui Oasis, and changes in groundwater dynamics in the oasis are predominantly influenced by surface runoff. (4) Monthly changes in groundwater levels in the Yutian Oasis are continuous, with ‘V’ shaped fluctuations, a declining trend in the southern part, no significant change in the central part, and a slight increase in the northern part. These results contribute to the sustainable management of water resources in the Kriya River Basin, provide a basis for groundwater prediction, and offer a reference for studies of other, similar extreme desert area basins.     

Energy dissipation caused by boundary resistance in a typical reach of the lower Yellow River and the implications for riverbed stability

The energy dissipation of boundary resistance is presented in this paper based on the flow resistance. Additionally, the river morphology responses to the resistance energy dissipation are explored using the Gaocun-Taochengpu reach in the lower Yellow River as a prototype. Theoretical analysis, measured data analysis and a one-dimensional hydrodynamic model are synthetically used to calculate the energy dissipation rate and riverbed morphological change. The results show that the energy dissipat...