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1.
To enable a wider use of dissolved noble gas concentrations and isotope ratios in groundwater studies, we have developed an efficient and portable sampling device using a commercially available membrane contactor. The device separates dissolved gases from a stream of water and collects them in a small copper tube (6 mm in diameter and 100 mm in length with two pinch‐off clamps) for noble gas analysis by mass spectrometry. We have examined the performance of the sampler using a tank of homogeneous water prepared in the laboratory and by field testing. We find that our sampling device can extract heavier noble gases (Ar, Kr, and Xe) more efficiently than the lighter ones (He and Ne). An extraction time of about 60 min at a flow rate of 3 L/min is sufficient for all noble gases extracted in the sampler to attain equilibrium with the dissolved phase. The extracted gas sample did not indicate fractionation of helium (3He/4He) isotopes or other noble gas isotopes. Field performance of the sampling device was tested using a groundwater well in Vienna and results were in excellent agreement with those obtained from the conventional copper tube sampling method.  相似文献   

2.
数字化气氡观测干扰因素的分析研究   总被引：1，自引：0，他引：1       下载免费PDF全文
在进行地下流体数字化气氡观测及将观测资料应用于震情分析的过程中 ,发现某些干扰因素对数字化气氡观测和水氡的影响不同。在目前所用观测仪器和方法的条件下 ,气温对气氡值的影响系数为 - 0 4 % /℃ ;气压对气氡测值的影响系数为 0 1% /hPa ;不同类型的气水分离装置对气氡观测的影响很显著 ;同一含水层的井 (泉 )出水量的短期变化可引起观测水井流量的变化 ,但对气氡测值影响不显著 ;气氡测值对逸出气流量的变化反映不明显 ;逸出气含有杂质及气路泄漏等均会引起测值的下降。结合仪器的工作原理 ,对干扰产生的机制以及排除的方法进行了讨论  相似文献   

3.
氡断层气测量在佛山西淋岗活断层探测中的应用研究   总被引：2，自引：1，他引：1  
在佛山西淋岗活断层附近,垂直断层走向等距测量了断层附近载体中氡气相对含量值,得到了氡含量曲线图．分析了断层气上氡异常形态分布特征,探讨了断层气载体对氡异常形成的影响。  相似文献   

4.
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5.
A preparation method for the quantitative analysis of methane in lake water samples has been developed. The method is based on the equilibrium reactions of gases in a closed two-phase (headspace-water) system, in which the headspace gas is analyzed gaschromatographically. The method shows a standard deviation of ±5%, including sampling and sample preparation and can also be used for the quantitative determination of other dissolved gases.   相似文献   

6.
The analyses which have so far been made of volcanic gases have only given instantaneous measurements of the composition of the gas phase which, however, is likely to be variable during periods of eruptive activity. A first step towards the continuous measurement of fluctuations in the composition of the gas phase during eruptions was made in 1963, by the use of sampling tubes permitting the rapid determination in the field of individual components of gaseous emanations. Since then, a technique has been developed of collecting samples of volatile constituents and preserving them for subsequent analyses in the laboratory. On the other hand, a technique has been developed for continuous sampling with a distant recording mechanism, which permits the study of the dynamics of eruptive phenomena. The first results of observations on several different types of emanations (submarine, high and low temperature fumaroles, and gas discharges from basalt flows) may considered satisfactory. The present paper is intended to encourage volcanologists concerned with the study of eruptive phenomena to employ new methodes for the study of this problem. The analysis of the eruptive mechanisms should start with a simultaneous observation and recording of the greatest possible number of parameters. The gas phase is of fundamental importance in the eruptive phenomena. It is therefore indispensable to understand its variations with time, both rapid and slow. It is very important to be able to show, on the same diagram, curves representing the simultaneous variations of all the measurable parameters, chemical, physical, and mechanical.  相似文献   

7.
A field gas chromatograph, built in 1978, was used in the field to directly analyse volcanic gases before water vapor condensation. Tested in Vulcano (Italy), Kilauea (Hawaii) and Merapi (Indonesia), this field measurement technique provides the actual composition of the volcanic gas mixture. The technique avoids the depletion of sulfur gases and the dissolution of the acid gases in the condensed water during the cooling. Thus the mixture of H2S and SO2 in fumarolic and high temperature gases (up to 819°C) in equilibrium at the emission temperature was examined.  相似文献   

8.
A new apparatus, Venturi Effect System (VES), designed for sampling volcanic plumes is described and tested at Vulcano (Italy). This device, together with purified basic NH4OH solutions, supplies optimal conditions to obtain reliable Stotal/Cl/F ratios and enrichment factors for metallic trace elements (MTE). Good concordance for acid gas ratios and metal enrichment factors in both the gas phase and the related plume allows the procedure to be validated. The VES appears in Vulcano conditions as a simple, robust and easily portable apparatus that allows reliable collection of both acid gases and MTE within a single sample and the analysis with current chemical methods (High Pressure Liquid Chromatography, Inductively Coupled Plasma–Mass Spectrometry). This apparatus may be suitable for more difficult volcanoes where only the plume can be sampled.  相似文献   

9.
We have constructed an artificial laboratory fumarole to calibrate the most common chemical volcanic gas sampling techniques and obtain a quantitative measure of their efficacy. We have also developed and tested a new rugged and portable venturi spray gas sampler. The venturi sampler reproduced the output gas composition most accurately, followed by the Giggenbach bottles, filter packs, and lastly alkaline traps. Passive alkaline traps, however, did better than filter packs when sampling more concentrated fumarole gases. Under ideal conditions, the accuracy of the Giggenbach bottles was identical to the venturi sampler, although there was slightly more scatter. The Giggenbach sampler was more susceptible to problems with condensation on the input train even in a laboratory setting, and this technique was only effective in relatively concentrated gas streams. Filter packs are also effective, but extreme care must be exercised to maintain strong undersaturation with respect to the acid gas. If strong undersaturation (high pH) is not maintained, the filter packs return erroneously low S/Cl and S/F ratios. Use of a pH indicator is an effective way of avoiding this problem. The passive alkaline traps also under-sample sulfur, resulting in low reported S/Cl and S/F ratios. It appears that the overall sampling efficiency of all techniques was not strongly affected by oxygen fugacity over the limited range tested. When detecting sulfate and sulfite simultaneously, we found no difference in total sulfur before and after oxidation. This suggests that all sulfur from the gas regardless of oxidation state was absorbed as sulfite or sulfate and/or was quickly oxidized in solution. This conclusion is supported by IC HS− reference samples.  相似文献   

10.
A model for the diffusion of gases through polymeric tubing was derived which predicts that the amount of gas transferred is proportional to the tubing length and inversely proportional to the pumping rate. The model was experimentally tested and confirmed for oxygen transfer through fluorinated ethylene-propylene copolymer (FEP) tubing using tubing lengths and flow rates typical of ground water sampling. Diffusion can introduce measurable concentrations of oxygen into initially anoxic water. Diffusive loss of carbon dioxide from water that is oversaturated with respect to atmospheric CO2 does not measurably affect pH under similar usage conditions.  相似文献   

11.
After the March–April 1986 explosive eruption a comprehensive gas study at Augustine was undertaken in the summers of 1986 and 1987. Airborne COSPEC measurements indicate that passive SO2 emission rates declined exponentially during this period from 380±45 metric tons/day (T/D) on 7/24/86 to 27±6 T/D on 8/24/87. These data are consistent with the hypothesis that the Augustine magma reservoir has become more degassed as volcanic activity decreased after the spring 1986 eruption. Gas samples collected in 1987 from an 870°C fumarole on the andesitic lava dome show various degrees of disequilibrium due to oxidation of reduced gas species and condensation (and loss) of H2O in the intake tube of the sampling apparatus. Thermochemical restoration of the data permits removal of these effects to infer an equilibrium composition of the gases. Although not conclusive, this restoration is consistent with the idea that the gases were in equilibrium at 870°C with an oxygen fugacity near the Ni–NiO buffer. These restored gas compositions show that, relative to other convergent plate volcanoes, the Augustine gases are very HCl rich (5.3–6.0 mol% HCl), S rich (7.1 mol% total S), and H2O poor (83.9–84.8 mol% H2O). Values of D and 18O suggest that the H2O in the dome gases is a mixture of primary magmatic water (PMW) and local seawater. Part of the Cl in the Augustine volcanic gases probably comes from this shallow seawater source. Additional Cl may come from subducted oceanic crust because data by Johnston (1978) show that Cl-rich glass inclusions in olivine crystals contain hornblende, which is evidence for a deep source (>25km) for part of the Cl. Gas samples collected in 1986 from 390°–642°C fumaroles on a ramp surrounding the inner summit crater have been oxidized so severely that restoration to an equilibrium composition is not possible. H and O isotope data suggest that these gases are variable mixtures of seawater, FMW, and meteoric steam. These samples are much more H2O-rich (92%–97% H2O) than the dome gases, possibly due to a larger meteoric steam component. The 1986 samples also have higher Cl/S, S/C, and F/Cl ratios, which imply that the magmatic component in these gases is from the more degassed 1976 magma. Thus, the 1987 samples from the lava dome are better indicators than the 1986 samples of degassing within the Augustine magma reservoir, even though they were collected a year later and contain a significant seawater component. Future gas studies at Augustine should emphasize fumaroles on active lava domes. Condensates collected from the same lava-dome fumarole have enrichments ot 107–102 in Cl, Br, F, B, Cd, As, S, Bi, Pb, Sb, Mo, Zn, Cu, K, Li, Na, Si, and Ni. Lower-temperature (200°–650°C) fumaroles around the volcano are generally less enriched in highly volatile elements. However, these lower-termperature fumaroles have higher concentration of rock-forming elements, probably derived from the wall rock.  相似文献   

12.
Analysis of dissolved light hydrocarbon gas concentrations (primarily methane and ethane) in water supply wells is commonly used to establish conditions before and after drilling in areas of shale gas and oil extraction. Several methods are currently used to collect samples for dissolved gas analysis from water supply wells; however, the reliability of results obtained from these methods has not been quantified. This study compares dissolved methane and ethane concentrations measured in groundwater samples collected using three sampling methods employed in pre‐ and post‐drill sampling programs in the Appalachian Basin. These include an open‐system collection method where 40 mL volatile organic analysis (VOA) vials are filled directly while in contact with the atmosphere (Direct‐Fill VOA) and two alternative methods: (1) a semi‐closed system method whereby 40 mL VOA vials are filled while inverted under a head of water (Inverted VOA) and (2) a relatively new (2013) closed system method in which the sample is collected without direct contact with purge water or the atmosphere (IsoFlask®). This study reveals that, in the absence of effervescence, the difference in methane concentrations between the three sampling methods was relatively small. However, when methane concentrations equaled or exceeded 20 mg/L (the approximate concentration at which effervescence occurs in the study area), IsoFlask® (closed system) samples yielded significantly higher methane concentrations than Direct‐Fill VOA (open system) samples, and Inverted VOA (semi‐closed system) samples yielded lower concentrations. These results suggest that open and semi‐closed system sample collection methods are adequate for non‐effervescing samples. However, the use of a closed system collection method provides the most accurate means for the measurement of dissolved hydrocarbon gases under all conditions.  相似文献   

13.
汤东活动断裂带气体地球化学特征   总被引：2，自引：1，他引：1       下载免费PDF全文
本文采用野外多期跨断层流动观测测定了汤东活动断裂带H2,Rn和CO2的分布特征,以此分析了该断裂带的气体地球化学特征及其活动背景,从而揭示了气体地球化学特征与构造之间的联系。分析结果显示:不同测量期次的H2,Rn和CO2浓度存在显著差异,其中张河村测线的各期次测量结果中6月份各组分气体浓度均显著高于其它期次,而邢李庄测线的测量结果中1月份各组分气体浓度均显著高于其它期次;各测量期次的各气体组分分布曲线特征相似,高值异常点的重现性较好。张河村测线多期测量的H2和Rn浓度背景值分别为（8.93±3.92）×10?6和（17.38±4.28） kBq/m3,在测线西部距汤东主断裂135 m和230 m处H2与Rn同步出现高值异常;邢李庄测线H2和Rn的背景值分别为（41.20±16.64）×10?6和（29.00±8.28） kBq/m3,H2与Rn在测线西部距汤东主断裂60 m处同步出现异常。两测线的气体浓度高值异常部位与地球物理、跨断层联合钻孔详勘结果之间存在较好的对应关系,由此可推断观测气体浓度能够敏感地指示断裂带位置,而且H2和Rn浓度是汤东断裂带气体地球化学观测的关键指标。   相似文献   

14.
Noble gas elemental and isotopic abundances were measured in seven deep-sea water samples from five different sampling sites in the Nankai Trough, the Japan Trench and the Kuril Trench. The samples were obtained by the manned submersible “Nautile”. Most of the sampling sites are associated with clam colonies and/or fluid venting. Excesses both in3He/4He ratio and He concentration are observed in a seawater sample collected a few kilometers off the clam colonies which were found at a depth of 3830 m at the mouth of the Tenryu Canyon. Concentrations of noble gases (Ne, Ar, Kr and Xe) in this sample show progressive depletion from Ne to Xe relative to those in 1°C air-saturated seawater, which can be attributed to mixing of hot water ( 15°C) with cold ambient water ( 1°C). Isotopic compositions of Ne, Ar, Kr and Xe in this sample are atmospheric. These observations may reflect venting of hot pore water around the Tenryu Canyon. All the other samples show a significant excess in concentration of all noble gases relative to 1°C air-saturated seawater and the isotopic compositions are atmospheric. This excess of noble gas concentrations may appear to be air contamination in the samples. However, results of hydrocarbon analyses of the Kaiko samples imply that such large amount of air contamination is improbable. Decomposition of gas hydrate in deep-sea sediments is a more likely explanation for the observed excess of noble gas concentration.  相似文献   

15.
A simple system was designed using7LiOH-impregnated filters to collect acidic gases from ambient air and from highly concentrated volcanic plumes or gas streams. These filters were developed for analysis using instrumental neutron activation analysis, but other analytical techniques could be used as well. The sampling system was designed to use a series of 1–3 M7LiOH-impregnated filters to collect high concentrations of acidic gases found in gas plumes of active volcanoes. The filters are quantitative for SO2 and the halide acids when sufficient base is present to neutralize the acidic species. Extremely high concentrations of SO2 may not be collected quantitatively since SO2 is a relatively weak Lewis acid compared to the halide acids. The acidic oxides of Sb, As, and Se were also collected quantitatively. A particle filter preceded the impregnated filters in order to remove particles from the fumes. This system has proven effective under difficult sampling conditions and, since it is portable and light weight, it could be used for many volcanological applications where high levels of acidic gaseous phase species need to be collected.  相似文献   

16.
Nitrogen and noble gases were measured in samples of a glass inclusion and the surrounding basaltic matrix from the antarctic shergottite EETA 79001. A nitrogen component trapped in the glass, but not present in the matrix, has a δ15N value at least as high as +190‰. Ratios of40Ar/14N and15N/14N in the glass are consistent with dilution of a martian atmospheric component (δ15N = 620 ± 160‰,40Ar/14N= 0.33 ± 0.03) by either terrestrial atmosphere adsorbed on the samples or by indigenous nitrogen from the minerals of the rock. Trapped noble gases in the glass reproduce, within error, the elemental and isotopic compositions measured in Mars' atmosphere by Viking, and are in general agreement with previous measurements except for much lower abundances of neutron-generated krypton and xenon isotopes. The most reasonable explanation at the present time for the noble gas pattern and the isotopically heavy nitrogen is that a sample of martian atmosphere has been trapped in the EETA 79001 glass, and that this meteorite, and thus the shergottites and probably the nakhlites and chassignites as well, originated on Mars.Nitrogen in the non-glassy matrix of EETA 79001 amounts to less than 0.5 ppm and has a spallation-corrected δ15N value in the range 0 to ?20‰; it may reflect indigenous nitrogen in the basalt or a mixture of indigenous and adsorbed terrestrial nitrogen. Spallogenic noble gases yield single-stage exposure ages between 400,000 and 900,000 years, depending on irradiation geometry. Trapped argon may have an unusually low36Ar/38Ar ratio. Trapped krypton, except for a small excess at80Kr, is smoothly mass-fractionated with respect to either terrestrial or chondritic Kr. The trapped xenon composition is consistent with addition of neutron-capture, radiogenic and fissiogenic isotopes to a base composition resembling terrestrial atmospheric Xe. The elemental84Kr/132Xe ratio of 25 is close to the terrestrial value and very different from the chondritic ratio.  相似文献   

17.
Kinetic experiments of gas generation for typical samples of marine gas precursors including low-maturity kerogen, residual kerogen and oil as well as dispersed liquid hydrocarbon (DLH) in source rocks were performed by closed system, and the evolution trends of molecular and isotopic compositions of natural gases from different precursors against the maturity (R 0%) at laboratory conditions were analyzed. Several diagrams of gas origin were calibrated by using the experimental data. A diagram based on the ratio of normal and isomerous butane and pentane (i/nC4 ? i/nC5) was proposed and used to identify the origins of the typical marine natural gases in the Sichuan Basin and the Tarim Basin, China. And the maturities of natural gases were estimated by using the statistical relationships between the gaseous molecular carbon isotopic data and maturities (δ13C-R 0%) with different origins. The results indicate that the molecular and isotopic compositions of simulated gases from different precursors are different from each other. For example, the dryness index of the oil-cracking gas is the lowest; the dryness indices of gases from DLH and kerogen in closed system are almost the same; and the dryness index of gases from residual kerogen is extremely high, indicating that the kerogen gases are very dry; the contents of non-hydrocarbon gases in kerogen-cracking gases are far higher than those in oil-cracking and DLH-cracking gases. The molecular carbon isotopes of oil-cracking gases are the lightest, those of kerogen in closed system and GLH-cracking gases are the second lightest, and those of cracking gases from residual kerogen are the heaviest. The calibration results indicate that the diagrams of In(C1/C2)-In(C2/C3) and δ4 3C2-δ4 3C3-In(C2/C3) can discriminate primary and secondary cracking gases, but cannot be used to identify gas origin sources, while the diagram of i/nC4 ? i/nC5 can differentiate the gases from different precursors. The application results of these diagrams show that gas mixtures extensively exist in China, which involved the gases from multiple precursors and those from different maturity stages. For example, marine gases in the Sichuan Basin involve the mixture of oil-cracking gases and high-over-maturated kerogen gases, while those in the Tarim Basin involve not only the mixture of gases from multiple precursors, but also those from different maturity gases and post-reservoir alternations such as oxidized degradation and gas intrusion processes.  相似文献   

18.
Unconventional natural gas extraction from tight sandstones, shales, and some coal‐beds is typically accomplished by horizontal drilling and hydraulic fracturing that is necessary for economic development of these new hydrocarbon resources. Concerns have been raised regarding the potential for contamination of shallow groundwater by stray gases, formation waters, and fracturing chemicals associated with unconventional gas exploration. A lack of sound scientific hydrogeological field observations and a scarcity of published peer‐reviewed articles on the effects of both conventional and unconventional oil and gas activities on shallow groundwater make it difficult to address these issues. Here, we discuss several case studies related to both conventional and unconventional oil and gas activities illustrating how under some circumstances stray or fugitive gas from deep gas‐rich formations has migrated from the subsurface into shallow aquifers and how it has affected groundwater quality. Examples include impacts of uncemented well annuli in areas of historic drilling operations, effects related to poor cement bonding in both new and old hydrocarbon wells, and ineffective cementing practices. We also summarize studies describing how structural features influence the role of natural and induced fractures as contaminant fluid migration pathways. On the basis of these studies, we identify two areas where field‐focused research is urgently needed to fill current science gaps related to unconventional gas extraction: (1) baseline geochemical mapping (with time series sampling from a sufficient network of groundwater monitoring wells) and (2) field testing of potential mechanisms and pathways by which hydrocarbon gases, reservoir fluids, and fracturing chemicals might potentially invade and contaminate useable groundwater.  相似文献   

19.
We use a simple model of the formation, growth, coalescence and migration of veins of basaltic melt generated by partial melting in chondritic asteroids to deduce the sizes of, and pressures within, the fluid-filled dikes reaching the surfaces of such bodies. The gas contents ( 1000 ppm of mainly CO and N2) of the asteroids were high enough that bubbles of free gas trapped in the melt veins gave the basaltic melts significant buoyancy; expansion of these gases as a dike opened to the vacuum at the surface led to fragmentation of the melts into liquid droplets which were transported upwards by the accelerating gases to the surface. The sizes of these droplets and, hence, of the pyroclastic glass beads into which they cooled, are calculated to lie in the range 30 μm to 4 mm; this range is essentially independent of the size or gas content of the asteroid parent and only weakly dependent on the internal pressure of the erupting fluid. The fate of the pyroclasts, however, does depend on all of these factors. At very low internal pressures, significant separation of the gas and liquid in a rising dike may take place and not all of the liquid will be expelled from the dike when it opens to the surface. For relatively large ( 100 km radius) asteroids with relatively low ( 300 ppm) gas contents, the larger clasts are too heavy to be lifted from the level at which magma fragmentation takes place by the gas flow and so would also remain behind to form basaltic veins. The apparent absence of basaltic veins in meteorites then implies both that internal pressures in near-surface dikes were generally greater than 0.3 MPa and that low gas contents were not common. Finally, as long as pyroclasts are lofted from the magma fragmentation level, they will be accelerated to at least 90% of the final gas speed. If this speed exceeds the escape speed from the asteroid (as happens readily for high gas contents and small asteroids), the pyroclasts will be expelled into space and lost from the meteorite record. Otherwise (low gas contents or large asteroids), they will eventually fall back to be incorporated into the surface regolith, modifying the chemical and physical properties of meteorites subsequently derived from it.  相似文献   

20.
陈万春 《华南地震》1995,15(4):70-77
结合断层气测量，对压电晶体吸附检测器检测气体浓度的基本原理、测量装置、石英晶片选择、测量气室构型、气体进样方式、化学涂层物质的选择、涂层的制备、载气的选择、水汽及其它气体的干扰影响及消除等作了较详尽的论述，并简略介绍了目前利用压电晶体吸附检测器实现气体测量的气体种类、所用涂层物质、干扰情况及所能达到的精度。指出压电晶体吸附检测器具有灵敏度高，气体选择性好，装置简单，易于实现现场连续监测等优点，将其  相似文献   

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