Hydrogen diffusion in clinopyroxene: dehydration experiments

Hydrogen diffusivity of one clinopyroxene megacryst from Nüshan, eastern China parallel to [001]* crystallographic direction was measured by high-temperature sequential dehydration experiments at 950℃ and 850℃, which was (6.5± 1.5)×10-12(m2/s) and (1.8± 0.7)×10-12(m2/s) respectively. From these results and the previous published data, it seems that the correlation between hydrogen diffusivity and Fe content suggested by Dyar et al. (1996) possibly does not exist. Clinopyroxene megacrysts from alkali basalts appear to be possible reliable samples for the study of the water evolution and hydrogen isotope compositions of the upper mantle.     

Hydrogen emissions from Erebus volcano, Antarctica

The continuous measurement of molecular hydrogen (H₂) emissions from passively degassing volcanoes has recently been made possible using a new generation of low-cost electrochemical sensors. We have used such sensors to measure H₂, along with SO₂, H₂O and CO₂, in the gas and aerosol plume emitted from the phonolite lava lake at Erebus volcano, Antarctica. The measurements were made at the crater rim between December 2010 and January 2011. Combined with measurements of the long-term SO₂ emission rate for Erebus, they indicate a characteristic H₂ flux of 0.03?kg s^–1 (2.8?Mg? day^–1). The observed H₂ content in the plume is consistent with previous estimates of redox conditions in the lava lake inferred from mineral compositions and the observed CO₂/CO ratio in the gas plume (～0.9 log units below the quartz–fayalite–magnetite buffer). These measurements suggest that H₂ does not combust at the surface of the lake, and that H₂ is kinetically inert in the gas/aerosol plume, retaining the signature of the high-temperature chemical equilibrium reached in the lava lake. We also observe a cyclical variation in the H₂/SO₂ ratio with a period of ～10?min. These cycles correspond to oscillatory patterns of surface motion of the lava lake that have been interpreted as signs of a pulsatory magma supply at the top of the magmatic conduit.     

Hydrogen generation from mantle source rocks in Oman

Hydrogen gas, associated with Ca²⁺ OH-rich alkaline groundwaters (pH = 10–12), is at present emanating from ultramafic rocks of the Oman ophiolite. Isotopic and chemical evidence indicates that hydrogen is formed by low-temperature redox reactions in a closed groundwater environment. This is normally a cryptic process in the hydrosphere but is fortuitously revealed by the unusual hydrogeological conditions in Oman where atmospheric oxygen is totally assimilated. It is suggested that hydrogen generation in mantle source rocks at depth and in the early Archaean surface environment may be more widespread than has hitherto been realised.     

Hydrogen and calcium lines in solar prominence spectra

The solar prominence radiation spectrum has been simulated in close H and K lines of ionized calcium and hydrogen line H? convenient for processing in CCD observations. Equations of radiation transfer and statistical equilibrium in absence of LTE are solved for a model of homogeneous plane layer, taking into account the partial frequency redistribution for a 20-level continuum model of hydrogen atoms and a 5-level continuum model of calcium ions. The ratio of the integral intensities s = E(H Ca II)/E(H?) and t = E(K)/E(H) Ca II is calculated for a model grid (pressure 0.001 < P < 1.0 dyn/cm², temperature 4000 < T < 20000 K). The s(T, P) and t(T, P) constructed diagnostic charts for solar prominences are obtained for the first time with allowance for the influence of the Ly?? line on the ionization of Ca II ions.     

依兰-伊通断裂方正-萝北段氢气特征研究

为研究断裂与断层氢气间的关系，围绕依兰-伊通断裂方正-萝北段开展断层氢气浓度流动观测工作，得到该段断裂氢气浓度变化特征。结果表明:在时间尺度上，氢气浓度存在年变规律特征，主要受温度、湿度和微生物活动的影响，一年中夏季氢气浓度最高，春秋季最低；在空间尺度上，依兰-伊通断裂北段呈南低北高的分段性特征，氢气浓度高值地区对应地震活动较强的地区，低值地区对应地震活动较弱的地区，这与当前地震活动特征相符，说明断层氢气浓度与当前地震构造活动具有较好的耦合关系。     

松原5.7级地震震中区土壤氢气变化特征

2018年5月28日吉林松原发生5.7级地震,为了探究地震对断层气的影响以及震后断层气变化特征,震后在震中区进行了多期土壤氢气浓度观测工作,得到了震中区氢气浓度的最大值、背景值等多项指标。结合地震前后氢气浓度数据,分析震中区震前、震后氢气浓度趋势性变化情况,结果显示:在此次地震活动中,氢气浓度变化有"震前缓慢升高—临震下降—震后迅速升高—强余震前再次骤升"的现象;氢气浓度变化与地震活动间有很好的映震关系,主震对氢气浓度的上升起主要作用,而余震则起诱发作用,余震的活动会使赋存在地下岩石裂隙的氢气释放量增大,表明氢气对余震活动的响应较灵敏;另外,震后某一时刻空气中的氢气浓度也会升高,这可能与区域断层中的氢气逸散到大气中有一定关系。     

基于氢氧同位素分析南昌地震台流体观测井水补给来源

在地震地下流体研究中,地下水补给及循环过程是重要的研究内容之一,氢氧同位素示踪技术是目前研究该过程的常用手段。南昌地震台流体观测井自2013年8月22日投入观测以来,其基础数据未进行有效分析,通过对南昌井水样数据进行氢氧同位素及水化学实验分析,结果表明：井水主要补给源为直接大气降雨,补给前经历了一定蒸发作用;水—岩反应不充分,属于未成熟水;水样中无明显优势阳离子,Ca²⁺、Na⁺占主体,优势阴离子为HCO₃^－,表明井水属重碳酸型水;水源补给高程约582 m。南昌地震台流体观测井总体受大气降水影响较大。     

痕量氢观测环境及供电系统建设

应用ATG-6118H痕量氢在线自动分析仪在水井类观测点观测过程中发现,外界观测环境的变化对于痕量氢浓度的观测存在一定干扰。文章依据宁河痕量氢观测井的观测环境及供电系统的改造过程,对2017年11月11日井房改造完成前后的痕量氢浓度数据进行分析论述,为该仪器的后续观测提供一些借鉴经验。     

Optimization of the Sampling Technique for the Determination of Dissolved Hydrogen in Groundwater

In this study a field‐sampling technique for dissolved hydrogen (H₂) in groundwater will be presented which allows the transport of gaseous samples into the laboratory for further analysis. The method consists of transferring the headspace trapped in a gas‐sampling bulb which is continuously purged by groundwater into previously evacuated vials using a gas‐tight syringe. Three transfer steps with preceding evacuation of the vial led to a H₂‐recovery of 100 % in laboratory experiments. The method has been applied to determine H₂ concentrations in an aquifer contaminated with chlorinated solvents. Tests concerning the effect of different pumping techniques on H₂ concentrations revealed that most reliable values were obtained with a bladder pump, while an electrically driven submersible pump generated considerable amounts of hydrogen due to electrochemical interactions with the sampled water. Concentrations of dissolved hydrogen in field and laboratory samples were about two orders of magnitude higher when sampling was performed with the electrically driven submersible pump compared to sampling with the bladder pump and a peristaltic pump. Lab experiments with a Plexiglas reservoir to produce H₂‐enriched water were used to study the effect of two tubing materials (PVC, polyamide) on H₂ losses. PVC tubing turned out to allow transfer of H₂‐enriched water over 25 m without significant losses, while PA‐tubing was not suitable for sampling of H₂.     

九江地震台观测井水氢氧同位素特征及意义

在地震地下流体观测研究中,基于氢氧同位素示踪技术研究地下水补给源及循环过程是常用的技术方法之一。本文给出了九江地震台2号观测井水、大气降水、周边水库水及高山泉水等样品的氢氧同位素测定结果,表明地下水δ~(18)O测值介于-7.59‰～-6.09‰,平均值-6.99‰,δD测值介于-45.22‰～-39.69‰,平均值-42.32‰,变异异数分别为0.09、0.16;大气降水δ~(18)O测值介于-13.00‰～-1.27‰,平均值-4.74‰,δD测值介于-96.13‰～-4.74‰,平均值-46.87‰,变异异数分别为0.40、0.56,与降水相比,地下水氢氧同位素变化更为稳定。大气降水氢氧同位素2017年5～10月表现为明显的降水效应,2018年11～4月表现为明显的温度效应,而地下水氢氧同位素并未表现出明显的降水效应和温度效应。氢氧同位素及过量氘揭示地下水在下渗补给前经历了明显的蒸发分馏作用,并与围岩进行~(18)O交换,δ~(18)O与δD计算得出的补给高程分别约为647、440m。九江台观测井的观测层地下水为大气降水成因的构造裂隙水,属于大气成因型且循环过程为较稳定的裂隙水补给并形成承压自流井。     

Hydrogen and oxygen isotope studies of metamorphic fluid-rock interactions in the Dabie Mountains

Hydrogen and oxygen isotope studies were carried out on mineral separates from high to ultrahigh pressure metamorphic rocks at Huangzhen and Shuanghe in the eastern Dabie Mountains, East China. The δ¹⁸O values of eclogites cover a wide range of −5‰ to+9‰, but the δD values of micas fall within a narrow range of −85% to −70‰. Both equilibrium and disequilibrium oxygen isotope fractionations were observed between quartz and the other minerals, with reversed fractionations between omphacite and garnet in some eclogite samples. The δ¹⁸ O values of −5‰ to −1‰ for some of the eclogites represent the oxygen isotope compositions of their protoliths which underwent meteoric water-rock interaction prior to plate subduction. The preservation of oxygen isotope heterogeneity in the eclogites implies a channelized flow of fluids during progressive metamorphism caused by rapid subduction. Retrograde metamorphism has caused oxygen and hydrogen isotope disequilibria between some of the minerals, but the fluid for retrograde reactions was internally buffered in the stable isotope compositions. Project supported by the Chinese Ministry of Science and Technology (Grant No. 95-Pre-39), the National Natural Science Foundation of China (Grant Nos. 49794042, 49473173 and 49453003) and the Chinese Academy of Sciences (Grant No. KZ951-A1-401-5)     

断层气氢浓度观测技术试验研究

In order to explore the new technology and methods for seismic underground fluid observation, a test study on measurement of hydrogen concentration in fault gas is carried out at the piedmont fault zone of Zhongtiao Mountain. Through the experiment on observation positions, gas collection devices and sampling depths, the paper presents the observation method for fault gas hydrogen concentration by using an online automatic trace hydrogen analyzer. Comparative tests are conducted on the stability and optimum conditions of this type of instrument in the field environment, and the hydrogen concentrations at different measuring points of the same fault are observed. The results show that it is technically feasible to carry out continuous hydrogen concentration on a fault zone. The method proposed in this study could be a useful tool for setting the observation points, choosing a reasonable observation depth and scientific analysis of the observed data.     

断层带土壤H2浓度变化特征及影响因素研究

收集全国15个不同区域、不同地质环境、不同深度测点的H2浓度,以及气温、气压整点值连续观测资料,研究高精度土壤H2浓度日、月动态变化特征,通过计算H2浓度与气温、气压的相关系数,定量分析不同观测孔深气温、气压对H2浓度的影响程度。结果表明:土壤H2浓度动态变化与气象因素密切相关,观测孔优选深度为4~11 m。     

Generation of Hydrogen Gas as a Result of Drilling Within the Saturated Zone

Hydrogen gas was discovered within the steel casing above standing water in a percussion-drilled borehole on the Hanlord Site in south-central Washington state. In situ measurements of the borehole fluids indicated anoxic, low-Eh (<-400 mV) conditions. Ground water sampled from adjacent wells in the same formation indicated that the ground water was oxygenated. H₂ was generated during percussion drilling, due to the decomposition of borehole waters as a result of aqueous reactions with drilled sediment and steel from the drilling tools or casing. The generation of H₂ within percussion-drilled boreholes that extend below the water table may be more common than previously realized. The ambient concentration of H₂ produced during drilling was limited by microbial activity within the casing-resident fluids. H₂ was generated abiotically in the laboratory, whereby sterilized borehole slurry samples produced 100 times more H₂ than unsterilizcd samples. It appears that H₂ is metabolized by microorganisms and concentrations might be significantly greater if not for microbial metabolism.     

Dissolved Hydrogen Dynamics Associated with Emulsified Vegetable Oil Bioremediation of Chloroethenes

Emulsified vegetable oil (EVO) is widely used as a fermentable substrate to enhance the reductive dechlorination of chlorinated ethenes (CEs) in groundwater systems. The fermentation of EVO by naturally occurring bacteria produces molecular hydrogen (H₂) which acts as an electron donor driving microbially mediated reductive dechlorination. While dissolved H₂ drives much of the dechlorination associated with CE bioremediation, the dynamics of H₂ production and consumption associated with EVO addition to groundwater systems is seldom documented. The present study shows how H₂ concentrations changed over a 4-year period following EVO addition to a sandy coastal plain aquifer underlying Naval Air Station Pensacola, Florida, USA. Prior to EVO addition, H₂ concentrations at the site were in the range characteristic of Fe(III)-reducing conditions (0.2–0.6 nM). Following EVO addition, H₂ concentrations increased exponentially, peaking at approximately 25,000 nM. Hydrogen concentrations then began decreasing exponentially, and by 4 years after EVO addition had stabilized at 4.0 nM. That pattern suggests symbiotic cross-feeding between fermentative and respirative microbial populations resulting in a Gaussian rise and fall of H₂ concentrations. That, in turn, suggests while EVO biostimulation can temporarily increase H₂ concentrations to very high levels, those higher concentrations are unlikely to be sustained indefinitely.     

Hydrogen and oxygen isotopic compositions of waters from fumaroles at Kilauea summit,Hawaii

Condensate samples were collected in 1992 from a high-temperature (300° C) fumarole on the floor of the Halemaumau Pit Crater at Kilauea. The emergence about two years earlier of such a hot fumarole was unprecedented at such a central location at Kilauea. The condensates have hydrogen and oxygen isotopic compositions which indicate that the waters emitted by the fumarole are composed largely of meteoric water, that any magmatic water component must be minor, and that the precipitation that was the original source to the fumarole fell on a recharge area on the slopes of Mauna Loa Volcano to the west. However, the fumarole has no tritium, indicating that it taps a source of water that has been isolated from atmospheric water for at least 40 years. It is noteworthy, considering the unstable tectonic environment and abundant local rainfall of the Kilauea and Mauna Loa regions, that waters which are sources to the hot fumarole remain uncontaminated from atmospheric sources over such long times and long transport distances. As for the common, boiling point fumaroles of the Kilauea summit region, their ¹⁸O, D and tritium concentrations indicate that they are dominated by recycling of present day meteoric water. Though the waters of both hot and boiling point fumaroles have dominantly meteoric sources, they seem to be from separate hydrological regimes. Large concentrations of halogens and sulfur species in the condensates, together with the location at the center of the Kilauea summit region and the high temperature, initially suggested that much of the total mass of the emissions of the hot fumarole, including the H₂O, might have come directly from a magma body. The results of the present study indicate that it is unreliable to infer a magmatic origin of volcanic waters based solely on halogen or sulfur contents, or other aspects of chemical composition of total condensates.