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1.
The mechanism of hydrogen sulfide (H2S) generation plays a key role in the exploration and development of marine high-sulfur natural gas, of which the major targets are the composition and isotope characteristics of sulfur-containing compounds. Hydrocarbon source rocks, reservoir rocks, natural gases and water-soluble gases from Sichuan Basin have been analyzed with an online method for the content of H2S and isotopic composition of different sulfur-containing compounds. The results of comparative analysis show that the sulfur-containing compounds in the source rocks are mainly formed by bacterial sulfate reduction (BSR), and the sulfur compounds in natural gas, water and reservoir are mainly formed by thermal sulfate reduction (TSR). Moreover, it has been shown that the isotopically reversion for methane and ethane in high sulfur content gas is caused by TSR. The sulfur isotopic composition of H2S in natural gas is inherited from the gypsum or brine of the same or adjacent layer, indicating that the generation and accumulation of H2S have the characteristics of either a self-generated source or a near-source.  相似文献   

2.
Ozonation is a treatment step which was first applied in the 1960s in pool water treatment for disinfection as well as for oxidation of pool water contaminants. Contact time between ozone and pool water was identified to be of significance with an increased elimination efficiency regarding chloramines, trihalogenmethane formation potential and the permanganate index for longer reaction times. Oxidation via OH radicals might be the dominating pathway. In this study ozonation was compared with the ozone based advanced oxidation processes ozone/UV and ozone/hydrogen peroxide regarding the elimination efficiency of both disinfection by‐products (DBPs) and DBP precursors. It was observed that AOPs in comparison to ozonation showed an increased elimination efficiency regarding total organic carbon (TOC), the organically bound halogens adsorbable on activated carbon (AOX) and AOX formation potential. A contact time of 3 minutes between pool water and oxidant turned out to be practically sufficient. Just for the trihalomethane (THM) formation potential ozonation showed a slight advantage compared to the AOPs because ozonation is a highly selective oxidant and OH radical reactions are known to produce small reactive molecules which are easier transformed to THMs. Combination of membrane filtration and AOPs resulted in an elimination of 10 to 90 % of the DBPs and their precursors. The ozone/hydrogen peroxide process is suggested for pool water treatment because of the higher elimination rates compared to ozonation and of economic reasons compared to the ozone/UV process.  相似文献   

3.
Dissolved organic matter (DOM) is a group of compounds that have complex chemical structures and multiple interactions with their surrounding materials. More than one trillion tons of DOM are stocked in the world’s aquatic ecosystems. DOM is a very important part of aquatic ecosystem productivity and plays a crucial role in global carbon cycling. DOM has rich environmental behaviors and effects such as influencing the bioavailability of contaminants, serving as an important inducer of reactive oxygen species (ROS), and protecting aquatic organisms from the harm of dangerous ultraviolet radiation. There have been many systematic studies on the composition, structure, and sources of DOM because such studies are much easier to conduct than studies on the environmental behaviors and effects of DOM. Due to many factors, the research systems of DOM’s environmental behaviors and effects are still being developed and have become a hotspot of environmental science. This review paper focuses on some critical progress, problems, and trends of DOM’s environmental behaviors and effects in aquatic ecosystems, including mutual exchange mechanisms between DOM and particulate organic matter (POM) with influencing factors, photochemical behaviors of DOM especially inducing ROS, binding interactions between DOM and anthropogenic organic contaminants (AOC), interactions between DOM and microorganisms, effects of DOM on pollutants’ bioavailability, ecotoxicity, and ecological risks. Hopefully, this paper will contribute to a more systematic understanding of the DOM environmental behaviors and effects and to promoting further relevant studies.  相似文献   

4.
胶体是一种分散相粒子具有特定粒径(通常为1 nm~1μm)的混合物,天然水体中的胶体通常是指水环境中普遍存在,而又符合“胶体”形态定义的物质的总和.因为具有特殊的表面性质以及独特的水动力学特点,天然水体中的胶体被认为是一种重要的污染物载体,尤其在促进重金属类的污染物迁移以及性质转化的过程中具有重要作用.本文归纳总结了水环境研究领域中胶体概念的提出与发展,讨论了现有研究中对胶体的定义与理解,比较了当前几种主要的胶体提取手段的特点.同时,针对胶体在水环境中的环境行为,详细归纳了河湖水体中胶体的物质组成、特征以及相应的检测手段,重点总结了胶体在水环境中对污染物的结合作用、胶体污染物的生物效应、胶体自身的团聚规律以及胶体对污染物迁移的影响机制.本文提出了胶体在水环境中复杂的组成成分与动态变化在胶体研究中的重要性,并对进一步揭示胶体环境效应的研究思路以及方法手段进行了展望.  相似文献   

5.
— On the basis of both experimental and field studies, solution transfer processes are expected to be important in contributing to fault strength recovery (healing) under the hydrothermal conditions prevailing in large parts of the seismogenic zone. However, most experimental work on healing effects in faults has been done using quartzo-feldspathic sliding surfaces or fault gouges, under conditions in which solution transfer processes are very slow. Mechanisms of fluid-assisted fault healing are accordingly rather poorly understood. We have performed slide-hold-slide fault healing experiments on simulated faults containing brine-saturated granular halite as a fault rock analogue. Halite was used because solution transfer processes are known to be rapid in this system under easily accessible conditions. We studied the effects of hold time duration, shear stress during hold, pre-hold sliding velocity and pore-fluid composition on strength evolution. The results show rapid fluid-assisted compaction and stress relaxation during hold periods, and a significant hold time-dependent strengthening upon re-shear. The data reveal that healing resulted from both a packing density increase and a contact area/strength increase during hold periods. The general type of behaviour observed is similar to that observed in quartzo-feldspathic gouges at room temperature, although important differences were observed as well. Notably, the time-dependence of healing deviates from the log-linear trend observed in gouges where solution transfer processes are absent. This means that if pressure solution is an important healing mechanism in natural faults, applying a log-linear trend will underestimate natural fault healing rates.  相似文献   

6.
The characterization of refractory organic substances (ROS) is very complicated because of their heterogeneous structure. Size-exclusion chromatography with continuous detection of dissolved nitrogen (LC-DN), dissolved organic carbon (LC-DOC), and UV-absorbance (LC-UV) is a very useful analytical tool for the characterization of changes of ROS in natural aquatic systems and in technological treatment. The effect of natural, oxidative, and biochemical processes on formation and removal of ROS is described. Additionally the role of hydrolysable carbohydrates in the composition of ROS is presented.  相似文献   

7.
Isotopic evidence of TSR origin for natural gas bearing high H2S contents 1961 As the hazardous component of natural gas, the ex-istence of H2S, due to its extremely strong toxicity and corrosivity, not only decreases the percentage of hy-drocarbon gas within natural gas and reduces its in-dustrial value, it also threatens each aspect of drilling and exploitation. It frequently causes serious safety accidents[1] and leads to the E&P cost and risk of natural gas with higher H2S contents be…  相似文献   

8.
The distribution of reduced sulfuric compounds in the surface layer of bottom deposits in the Northern Dvina mouth was examined. The natural biogeochemical processes and anthropogenic pollution are found to cause the formation and accumulation of reduced sulfuric compounds (mostly pyrite and organic forms) in bottom deposits. The concentration of individual forms of sulfur and its total concentration are found to vary widely from year to year. The most intense accumulation of the total reduced sulfur is recorded near the wastewater discharge sites of pulp and paper mills.  相似文献   

9.
Increased ultraviolet-B radiation (UV-B) in aquatic ecosystems brought about by stratospheric ozone depletion may result in increased formation rates of photochemical reaction products in the surface waters of aquatic ecosystems. In this study, the potential impact of increases in lower wave-length radiation on the formation of hydrogen peroxide (H2O2) and singlet oxygen (1O2) was modelled for lakes over a range of dissolved organic carbon (DOC) concentrations. The impact of increased UV-B radiation on the production of carbon monoxide (CO) was also calculated for two humic stained systems. The relative increases of H2O2 and1O2 production were greater in the clear lakes (70% increase in photochemical reaction rates near the surface) than the coloured systems (25%). Production of CO in the study sites also increased under depleted ozone conditions implying increased DOC losses to the overlying atmosphere.  相似文献   

10.
张怡晅  庞锐  任源鑫  程丹东 《湖泊科学》2022,34(5):1550-1561
城市非点源污染向水生生态系统中输入大量的溶解有机物(DOM),对生态系统健康产生重要影响.有色可溶性有机物(CDOM)是广泛分布于自然水体中的一类成分和结构复杂、含有多种高活性化学官能团的大分子聚合物,是DOM的重要组分,对水生生态系统健康、能量流动及生物地球化学循环有重要影响.光化学反应和微生物代谢过程被认为是控制水体CDOM转化、降解和循环的主要影响因素.然而,对城市化如何影响CDOM组成以及光化学和微生物如何相互作用影响城市水体CDOM动态的理解是不足的.因此,为评估光化学过程和微生物代谢对不同城市水体CDOM降解与转化的贡献,解析不同城市水体CDOM光化学/微生物降解作用机理,本研究在英国伯明翰选择3类具有典型DOM来源的水体样本,通过实验室9 d受控培养实验,对比分析光化学以及微生物影响下CDOM来源和组成的变化.结果表明:(1)城市河流由于接受上游污水排放及较短的水力滞留时间,含有丰富的芳香性碳,其CDOM光化学活性明显高于湖泊,光化学降解率为16.60%;(2)城市湖泊CDOM受人类活动影响,自生源类荧光成分富集,生物活性高,在微生物培养过程中CDOM增加了62.16%,...  相似文献   

11.
Measurements of the production and consumption of organic material have been a focus of aquatic science for more than 80 years. Over the last century, a variety of approaches have been developed and employed for measuring rates of gross primary production (Pg), respiration (R), and net ecosystem production (Pn = Pg − R) within aquatic ecosystems. Here, we reconsider the range of approaches and applications for ecosystem metabolism measurements, and suggest ways by which such studies can continue to contribute to aquatic ecology. This paper reviews past and contemporary studies of aquatic ecosystem-level metabolism to identify their role in understanding and managing aquatic systems. We identify four broad research objectives that have motivated ecosystem metabolism studies: (1) quantifying magnitude and variability of metabolic rates for cross-system comparison, (2) estimating organic matter transfer between adjacent systems or subsystems, (3) measuring ecosystem-scale responses to perturbation, both natural and anthropogenic, and (4) quantifying and calibrating models of biogeochemical processes and trophic networks. The magnitudes of whole-system gross primary production, respiration and net ecosystem production rates vary among aquatic environments and are partly constrained by the chosen methodology. We argue that measurements of ecosystem metabolism should be a vital component of routine monitoring at larger scales in the aquatic environment using existing flexible, precise, and durable sensor technologies. Current and future aquatic ecosystem studies will benefit from application of new methods for metabolism measurements, which facilitate integration of process measurements and calibration of models for addressing fundamental questions involving ecosystem-scale processes.  相似文献   

12.
The salinization of rivers, as indicated by salinity increases in the downstream direction, is characteristic of arid and semiarid regions throughout the world. Historically, salinity increases have been attributed to various mechanisms, including (1) evaporation and concentration during reservoir storage, irrigation, and subsequent reuse; (2) displacement of shallow saline ground water during irrigation; (3) erosion and dissolution of natural deposits; and/or (4) inflow of deep saline and/or geothermal ground water (ground water with elevated water temperature). In this study, investigation of salinity issues focused on identification of relative salinity contributions from anthropogenic and natural sources in the Lower Rio Grande in the New Mexico-Texas border region. Based on the conceptual model of the system, the various sources of water and, therefore, salinity to the Lower Rio Grande were identified, and a sampling plan was designed to characterize these sources. Analysis results for boron (delta(11)B), sulfur (delta(34)S), oxygen (delta(18)O), hydrogen (delta(2)H), and strontium ((87)Sr/(86)Sr) isotopes, as well as basic chemical data, confirmed the hypothesis that the dominant salinity contributions are from deep ground water inflow to the Rio Grande. The stable isotopic ratios identified the deep ground water inflow as distinctive, with characteristic isotopic signatures. These analyses indicate that it is not possible to reproduce the observed salinization by evapotranspiration and agricultural processes alone. This investigation further confirms that proper application of multiple isotopic and geochemical tracers can be used to identify and constrain multiple sources of solutes in complex river systems.  相似文献   

13.
在地下流体研究中,判定地下水异常的首要任务是区别地下水是受浅层物质补给的影响还是受深层介质活动的影响。本文通过对永清井及周边多次样品采集与测试,获得水化学组分和氢氧稳定同位素观测数据;通过对地下水样品数据对比分析、水化学组分及氢氧稳定同位素与大气降水线、水温数据分析,认为永清井水温的多次异常变化不是受干扰影响;通过对水温的异常变化与地震的对应关系的分析,认为永清井水温异常可能与3次地震有关。   相似文献   

14.
Based on studies on the geological characteristics of the copper-gold deposits in the middle and lower reaches of the Yangtze River area (MLYRA) and their hydrogen, oxygen, sulfur and lead isotope compositions, it is concluded that there existed two series of copper-gold deposits. They are evolutional products of two ore-forming hydrothermal systems in different geodynamic settings and geological era. Series I is stratiform or stratabound copper-gold deposits. These deposits were formed by submarine exhalation and sedimentation of hydrothermal solutions in Hercynian tensional tectonic environment after bot brine ascending along contemporaneous faults and exhaled into the sea-floor. Series II consists of copper-gold deposits related to medium and acidic magmatic intrusions. Their mineralizations took place in Yanshanian in a tensional or a transitional period to the tensional tectonic environment from the composite of the tethys tectonic regime and the Paleo-Pacific ocean tectonic regime, as well as in the upper mantle doming and crustal thinning environment. Copper-gold deposits were formed from the hydrothermal fluids, mixtures of magmatic water and part of meteoric water, by complex water-rock interactions and coupling dynamic processes of transport-chemical reactions. Superposition is an important condition for the formation of the large-scale copper-gold ore deposits.  相似文献   

15.
P, Fe, Mn, and S species were analyzed in water samples from the sediment-water interface collected at four seasonally different times during the course of a year at two sampling sites in the southern basin of Lake Lugano (Lago di Lugano). The results reveal the strong influence of the biogeochemical processes in the sediment on the chemical composition of the lake water above. Consumption of oxygen and nitrate under oxic to microoxic conditions in the water column as well as sequential release of reduced manganese and iron under anoxic conditions was observed as a direct or indirect consequence of microbially mediated degradation of organic matter. The seasonal pattern observed for the release and the retainment of dissolved reduced iron and manganese correlates well with the one for dissolved phosphate. Iron, manganese and phosphorus cycling are coupled tightly in these sediments. Both sediment types act as sinks for hydrogen sulfide and sulfate. An inner-sedimentary sulfur cycle is proposed to couple iron, manganese and phosphorus cycling with the degradation of organic matter. Nutrient cycling at the sediment-water interface might thus be driven by a microbially regulated electron pumping mechanism. The results contribute to a better understanding of the role of sediment processes in the lake's internal phosphorus cycle and its seasonal dynamics.  相似文献   

16.
Oxygen transfer in the capillary fringe (CF) is of primary importance for a wide variety of biogeochemical processes occurring in shallow groundwater systems. In case of a fluctuating groundwater table two distinct mechanisms of oxygen transfer within the capillary zone can be identified: vertical predominantly diffusive mass flux of oxygen, and mass transfer between entrapped gas and groundwater. In this study, we perform a systematic experimental sensitivity analysis in order to assess the influence of different parameters on oxygen transfer from entrapped air within the CF to underlying anoxic groundwater. We carry out quasi two‐dimensional flow‐through experiments focusing on the transient phase following imbibition to investigate the influence of the horizontal flow velocity, the average grain diameter of the porous medium, as well as the magnitude and the speed of the water table rise. We present a numerical flow and transport model that quantitatively represents the main mechanisms governing oxygen transfer. Assuming local equilibrium between the aqueous and the gaseous phase, the partitioning process from entrapped air can be satisfactorily simulated. The different experiments are monitored by measuring vertical oxygen concentration profiles at high spatial resolution with a noninvasive optode technique as well as by determining oxygen fluxes at the outlet of the flow‐through chamber. The results show that all parameters investigated have a significant effect and determine different amounts of oxygen transferred to the oxygen‐depleted groundwater. Particularly relevant are the magnitude of the water table rise and the grain size of the porous medium.  相似文献   

17.
A preliminary field performance evaluation of in situ bioremediation of a contaminated aquifer at the Libby, Montana, Superfund site, a former wood preserving site, was conducted for the Bioremediation Field Initiative sponsored by the U.S. Environmental Protection Agency (U.S. EPA). The current approach for site remediation involves injecting oxygen and nutrients into the aquifer to stimulate microbial degradation of target compounds that include polycyclic aromatic hydrocarbons and pentachlorophenol. The preliminary field evaluation determined that, in addition to the oxygen demand associated with the microbial oxidation of the organic contamination, uncontaminated aquifer sediments at the site are naturally reduced and also exert a significant oxygen demand. This conclusion is supported by three types of information: (1) analyses of ground water samples; (2) results from a field-scale tracer test; and (3) results of laboratory evaluations of oxygen use by reduced aquifer sediment samples. An estimate of the cost of supplying hydrogen peroxide to satisfy the oxygen demand of the uncontaminated reduced sediments is provided to demonstrate that the additional cost of oxidizing the reduced sediments could be significant. The presence of naturally occurring reduced sediments at a contamination site should be considered in the design of subsurface oxidant delivery systems.  相似文献   

18.
应力、应变或地震活动会打破地壳中流体原有的水-岩平衡状态,引起地下流体化学组分和同位素的变化。根据河北何家庄流体观测井氢氧同位素和离子化学组分测试结果,分析了该井的地球化学特征及与构造活动的关系。由氢氧同位素结果及高程效应,判定井水来源主要为大气降水,大气降水沿断裂裂隙渗入,深循环后温度增加,经溶滤作用等形成热水;按照舒卡列夫分类法,何家庄井水为Cl-Na.Ca型。受2015年9月14日昌黎M4.2地震的影响,区域应力变化使井孔断裂岩石裂隙增大,深部热水上涌,引起何家庄井水离子组分和氢氧同位素组成等发生变化。研究结果表明,对何家庄井流体地球化学特征进行分析,可以为井孔附近断裂构造活动和地震前兆异常分析提供地球化学依据。  相似文献   

19.
The northeastern area of Sichuan Basin, southwestern China, is the area with the maximal reserve of natural gas containing higher hydrogen sulphide (H2S) that has been found among the petroliferous basins of China, with the proven and controlled gas reserve of more than 200 billion cubic meters. These gas pools, with higher H2S contents averaging 9%, some 17%, are mainly distributed on structural belts of Dukouhe, Tieshanpo, Luojiazhai, Puguang, etc., while the oolitic-shoal dolomite of the Triassic Feixianguan Fm. (T1f) is the reservoir. Although many scholars regard the plentiful accumulation of H2S within the deep carbonate reservoir as the result of Thermochemical Sulfate Reduction (TSR), however, the process of TSR as well as its residual geological and geochemical evidence is still not quite clear. Based on the carbon isotopic analysis of carbonate strata and secondary calcite, etc., together with the analysis of sulfur isotopes within H2S, sulphur, gypsum, iron pyrites, etc., as well as other aspects including the natural gas composition, carbon isotopes of hydrocarbons reservoir petrology, etc., it has been proved that the above natural gas is a product of TSR. The H2S, sulphur and calcite result from the participation of TSR reactions by hydrocarbon gas. During the process for hydrocarbons being consumed due to TSR, the carbons within the hydrocarbon gas participate in the reactions and finally are transferred into the secondary calcite, and become the carbon source of secondary calcite, consequently causing the carbon isotopes of the secondary calcite to be lower (−18.2‰). As for both the intermediate product of TSR, i.e. sulfur, and its final products, i.e. H2S and iron pyrites, their sulfur elements are all sourced from the sulfate within the Feixianguan Fm. During the fractional processes of sulfur isotopes, the bond energy leads to the 32S being released firstly, and the earlier it is released, the lower δ 34S values for the generated sulphide (H2S) or sulfur will be. However, for the anhydrite that participates in reactions, the higher the reaction degree, the more 32S is released, while the less 32S remains and the more δ 34S is increased. The testing results have proved the process of the dynamic fractionation of sulfur isotopes.  相似文献   

20.
Yinchuan Basin, a semi‐arid area located in Northwest China, is currently subject to increasing pressure from the altered hydrology due to the anthropogenic activities as well as increasing water demands for regional development. Sustainable water management across the region must be underpinned by a clear understanding of the factors that constrain water supply in this area. We measured the stable isotope of oxygen and hydrogen to determine the likely processes that control the interrelations among precipitation, surface water (Yellow River), and groundwater. The hydrogen and oxygen values demonstrate that 2 primary hydrochemical processes, mixing and evaporation/condensation, occurred in the Basin. Recharge proportions of precipitation and Yellow River were quantitatively evaluated based on the isotope mass balance method. The proportions of the Yellow River and atmospheric precipitation recharge are 87.7% and 12.3%, respectively. The evaporation proportions calculated with 18O and D by Rayleigh fractional equation are close to each other, which demonstrate that evaporation intensity increases following the flow direction of the Yellow River. The findings obtained in this study are useful for recognizing the significance of Yellow River to Yinchuan Basin, and some optimal allocation schemes can be adopted for a prospective development of this reputed area in Northwest China.  相似文献   

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