Chemostatic behaviour of major ions and contaminants in a semiarid spring and stream system near Los Alamos,NM, USA

Recent studies have focused on the relationship between solute concentrations and discharge in streams, demonstrating that concentrations can vary little relative to changes in discharge (chemostatic behaviour). Chemostatic behaviour is dependent on catchment characteristics (e.g., lithology, geomorphology, and vegetation) and chemical characteristics of the solute (e.g., availability, reactivity, and mobility). An investigation of 3 springs and a stream near Los Alamos, NM, reveals that springs can behave in a chemostatic fashion as stream systems tend to do. Another unique finding of this study is that the anthropogenic contaminants barium and the high explosive RDX (hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine) can also behave chemostatically. The chemostatic behaviour of a contaminant has important implications for the residence time of contaminants in a system as well as having a major control on contaminant flux and mass transport. Redox (reduction–oxidation) and biogeochemically sensitive analytes (e.g., Fe, SO₄, and NO₃) display a combination of chemostatic and chemodynamic behaviour, showing the influence of temporally variable conditions on stream and spring chemistries.     

Hydrogeology of desert springs in the Panamint Range,California, USA: Identifying the sources and amount of recharge that support spring flow

Despite its location in the rain shadow of the southern Sierra Nevada, the Panamint Range hosts a complex mountain groundwater system supporting numerous springs which have cultural, historical, and ecological importance. The sources of recharge that support these quintessential desert springs remain poorly quantified since very little hydrogeological research has been completed in the Panamint Range. Here we address the following questions: (i) what is the primary source of recharge that supports springs in the Panamint Range (snowmelt or rainfall), (ii) where is the recharge occurring (mountain-block, mountain-front, or mountain-system) and (iii) how much recharge occurs in the Panamint Range? We answer questions (i) and (ii) using stable isotopes measured in spring waters and precipitation, and question (iii) using a chloride mass-balance approach which is compared to a derivation of the Maxey–Eakin equation. Our dataset of the stable isotopic composition (δ¹⁸O and δ²H) of precipitation is short (1.5 years), but analyses on spring water samples indicate that high-elevation snowmelt is the dominant source of recharge for these springs, accounting for 57 (±9) to 79 (±12) percent of recharge. Recharge from rainfall is small but not insignificant. Mountain-block recharge is the dominant recharge mechanism. However, two basin springs emerging along the western mountain-front of the Panamint Range in Panamint Valley appear to be supported by mountain-front and mountain-system recharge, while Tule Spring (a basin spring emerging at the terminus of the bajada on the eastern side of the Panamint Range) appears to be supported by mountain-front recharge. Calculated recharge rates range from 19 mm year⁻¹ (elevations < 1000 mrsl) to 388 mm year⁻¹ (elevations > 1000 mrsl). The average annual recharge is approximately 91 mm year⁻¹ (equivalent to 19.4 percent of total annual precipitation). We infer that the springs in the Panamint Range (and their associated ecosystems) are extremely vulnerable to changes in snow cover associated with climate change. They are heavily dependent on snowmelt recharge from a relatively thin annual snowpack. These findings have important implications for the vulnerability of desert springs worldwide.     

搭格架温泉水化学特征及其约束因素研究

搭格架地热区温泉水DJ1-DJ116号样品于2009年采集,阳离子及微量元素含量采用ICP-OES法测试,Cl-含量采用滴定法测试,其余阴离子含量采用紫外-可见光分光光度法测试。通过对温泉水化学指标的分析,研究温泉的水化学特征及约束因素。其温泉水化学类型为HCO3-Na型,平均矿化度为1 524 mg/L,具有较高的Na/Cl值,温泉水演化程度较高,为完全平衡水,热储中的水岩反应达到了平衡状态.温泉水中PO2极低,PCO2较高;大部分温泉水中玉髓、石英和无定形态SiO2三种硅质热液矿物的饱和度指数大于0。K-Na温标计算热储平均平衡温度为251.36℃;泉水中的Na＋、K＋离子活度主要受到钠、钾长石的约束。微量元素组合表现出花岗岩源的特征。总体上搭格架地热区温泉水化学特征受到区域地质背景的约束。     

煤矿开采对明水泉的影响浅析

明水泉群为我国北方罕见的岩溶大泉，具有典型的雨源型特征。大气降水和雨洪水下渗后，向明水一带汇集，受西部文祖断层阻挡而富集，受上覆煤系地层阻隔而承压，在特定的构造条件下，沿断层破碎带或人工钻孔涌出地表，便形成明水泉群。煤系地层是明水泉群形成和存在的基本地质条件之一。煤矿开采吸引大量岩溶泉水，而且破坏原生的地质结构，影响明水泉群的正常出流，危及明水泉群的存在。针对煤矿开采对明水泉群的影响，建议实施相应保泉措施。     

Major,trace element and stable isotope composition of water and muds precipitated from the hot springs of Bolivia: Are the waters of the spring's potential ore forming fluids?

The deposition of metal-rich black or reddish muds by many thermal springs in the Cordilleras and the Altiplano of Bolivia suggest that these geothermal waters may be related to those that once formed the world-class Bolivian tin, silver and gold mineralisation. The discharge temperatures of these springs are as high as 70 °C. According to δ¹⁸O, δD, tritium data and Ar/N₂ ratios these waters are predominantly of meteoric origin. Less than 10% of the discharging thermal water represents deep-seated metal-rich thermal brines of at least 530 °C according to carbon exchange between CO₂ and CH₄. These brines ascend along tectonic faults and mix with low-temperature meteoric water in surface-near aquifers. The meteoric component of the thermal water is recharged in the high Cordilleras with residence times exceeding 50 years. The chemical composition of the thermal water is dominated by the rather inefficient low-temperature leaching of the surface-near aquifer rocks by meteoric water. The small fraction of metal-rich hot deep-seated water is not able to increase the metal content of the water mix to a level sufficient to classify these thermal waters as ore-bearing. Surface-near leaching is supported, e.g., by the B/Li ratios of the spring water of the Western Cordillera and Caleras/Pulacayo in the Eastern Cordillera that correspond very closely to that of the easily leachable glassy inclusions of the outcropping andesitic lavas. The often remarkable metal content of the muds deposited by the springs originate from efficient scavenging of heavy metals by ferric oxyhydroxides. Under the given arid to semi-arid climate the muds are additionally enriched in metals by wind-transported dust. The present study does support a relation of the actual thermal waters with neither the classical subduction-related Upper Tertiary tin, silver and gold mineralisation nor the supposed younger Sb mineralisation of Bolivia.     

腾冲新生代火山区CO2气体释放通量及其成因

许多研究结果表明,休眠期火山主要通过喷气孔、温泉以及土壤微渗漏三种方式向大气圈释放温室气体。腾冲是我国重要的新生代火山区之一,同时也是主要的水热活动区,但是关于温室气体释放通量的研究却鲜有报道。本文首次估算了该地区土壤微渗漏和温泉水的CO2释放通量,并根据气体成分的分析结果探讨了这些温室气体的来源。2012~2013年连续两年使用密闭气室法现场测量了土壤微渗漏CO2通量,结果表明,马站、热海-黄瓜箐和五合-蒲川-团田三个地区通量较高,其中,热海-黄瓜箐地区平均通量最高,马站次之,五合-蒲川-团田地区最低。较高的土壤微渗漏CO2释放地区同前人推断的岩浆囊的分布在空间上具有较好的一致性;三个地区气体的3He/4He比值较高,三端元模拟结果表明,它们均有较高含量的幔源He释放;根据气体CO2/3He与δ13CCO,CO2模拟计算,CO2主要来源于碳酸盐矿物的脱碳作用和岩浆脱气。由此推断2的释放同深部的岩浆囊具有重要的成因联系,它为碳酸盐矿物的脱碳作用提供了主要的热源,同时也是重要的物质来源。根据土壤微渗漏CO2平均通量及火山、地热异常区的分布面积估算出三个地区土壤微渗漏CO2的释放通量分别为1.8×106t/a(马站),3.2×106t/a(热海-黄瓜箐)和2.0×106t/a(五合-蒲川-团田)。腾冲新生代火山区每年通过土壤微渗漏向大气圈释放CO2的量至少可达7.0×106t,为意大利Etna火山区释放CO2通量(1.4×107t/a)的二分之一。通过水岩相互作用计算温泉水中CO2气体的释放通量为4.9×104t/a。腾冲温泉气泡及温泉水向大气圈释放CO2气体的总通量为5.3×104t/a,远高于意大利Vulcano火山区温泉释放的CO2总通量(3.7×103t/a)。     

Screening of thermophilic microalgae and cyanobacteria from Tunisian geothermal sources

Six geothermal sources distributed in the north and south of Tunisia were examined monthly during the period from August 2009 to April 2010, in order to determine mats communities' abundance and biodiversity. Twenty-seven taxa, belonging to three taxonomic groups: Cyanobacteria, Bacillariophyta and Chlorophyta were identified. The Cyanobacteria group was more prominent with a particular dominance of two genera Phormidium and Spirulina. Their maximum abundance was respectively 919.2 ± 44.2 10³ cells ml⁻¹ and 652.8 ± 92.6 10³ cells ml⁻¹. The dominant mats morphologies in prospected sites were filaments. Results demonstrate that biodiversity values ranged between 0.16 and 1.15 bits. cell⁻¹. The spatial variations showed that the regional specificity in mats species biodiversity and abundance between north and south were not signified, whereas, each site had specific species. Temporal variations showed an increase of microalgae and prokaryotes abundance in the dry season.     

历史时期分布在北京平原上的泉水与湖泊

历史时期北京平原上湖泊众多,地表泉数以百计。历史时期由于永定河冲积扇的地下潜水水位较高,在潜水溢出带周围出露数以百计的下降泉,成为平原上众多湖泊的主要水源补给,并满足城市规划、园林设计、运河漕运、游憩休闲的需要。随着现代化城市的迅速发展,永定河冲积扇的地下潜水水位迅速下降,原来分布在潜水溢出带周围的数以百计的下降泉已经全部枯竭,位于其下游许多湖泊也随之干涸消亡,北京平原地表水系被彻底改造,城市生态环境发生巨大变化。     

半刚性连接钢框架结构弹性时程分析

用两端带转动弹簧的杆单元代替一般的杆单元,提出了一种新的平面杆系钢结构动力弹性时程分析计算模型。采用虚功原理,通过对单元转角-位移方程的修正,推导了这种计算模型的单元质量矩阵,并编制了相应的弹性时程分析计算程序,分析了连接的半刚性在不同地震动作用下对钢框架结构动力性能的影响,并与有限元结果进行了比较。算例结果表明:连接的半刚性对结构动力性能的影响非常大,结构的抗震性能优于刚性连接的情况。