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1.
Coal fires in natural outcrops, in abandoned and active coal mines, and in coal and coal-refuse piles are responsible for the uncontrolled emissions of gases, including CO, CO2, H2S, hydrocarbons, and volatile aromatics. Typically, measurements of gases at a mine vent are made over a short time interval, perhaps no more than 10 min, including the time for replicate measurements. Such timing provides little information on longer-term variations in emissions, although comparisons of seasonal measurements suggest such changes do occur. To address this problem, we placed temperature and CO data loggers in coal fire vents to collect time series measurements for a period of up to three weeks. For one experiment, 11 days of data at one-minute intervals indicated that the CO emissions were generally in the 400–550 ppmv range. However near daily depressions in CO concentrations occurred and in some cases fell below 50 ppmv; followed by an increase to ~ 700–800 ppmv; in turn followed by a return to the ambient conditions. Data for a separate 21-day collection period in a different vent of the same fire exhibited similar trends, albeit at a higher CO concentration. The drop in CO concentration may be associated with a meteorologically-driven inhalation cycle of the fire, whereby air diluted the combustion generated CO. We propose this was followed by an increase in the intensity of the fire due to increased O2 from the inhaled air, producing increased CO concentrations, before settling back to the ambient conditions.  相似文献   
2.
The genus Symbiodinium plays an essential role in the resistance and survival of reef‐building corals during temperature anomalies. Coral colonies inhabiting the Persian Gulf (PG) experience extended periods of different stresses. Kish Island is located in the harsh environment of the Northern PG with previously reported bleaching episodes. Samples of six coral species from Northwestern Kish Island were analysed by internal transcribed spacer 2 of ribosomal DNA to identify in hospite Symbiodinium populations. The results showed that lineage D of Symbiodinium was the most prevalent clade among different coral colonies, while clade C was only detected in symbiosis with a single coral species. However, the detected Symbiodinium subclades belonged to two host generalists. The predominance of the stress tolerant Symbiodinium trenchii and subclade C3 could suggest an acclimatization strategy to cope with the hostile environment of the PG.  相似文献   
3.
IntroductionWhenpropagatingthroughananisotropicmedium,ashearwavesplitsintotwo(quasi)shearwaveswithdifferentpropagationspeedsandpolarizedorthogonally.Owingtotherecentdevel-opmentofseismicobservationsystem,detectionofshearwavessplittingwithverysmalldelaytimesbetweenfasterandslowershearwavesbecameavailableandprovidedpowerfulapproachfordetectionofcrustalanisotropy.Crampin(1978)emphasizedtheroleofalignedmicrocracksasacauseofcrustalanisotropyandpointedoutthatforverticallyalignedmicrocracksthedirecti…  相似文献   
4.
ABSTRACT

Oil and its derivatives contaminate many soils and not only affect their chemical and biological properties but also their geotechnical properties. As oil contamination may deteriorate the functioning of piles, this paper addresses the effects of oil contamination on soil–pile interactions. Axial compressive bearing capacities of two close-ended, instrumented piles were investigated in different oil-contaminated sand using frustum confining vessel. Three different oils (gasoil, crude oil, and used motor oil) at different contamination levels were considered and using some strain gauges, the toe, shaft, and the net total bearing capacity of piles, as well as load distributions along the pile length, were derived. The results show that the presence of oil between soil particles has considerable adverse effects on bearing capacities of model piles, especially the shaft bearing capacity. The oil viscosity and percentage, as well as the contaminated sand bed thickness around the piles, are the most influential parameters. The higher the oil viscosity and oil content, the lower the values of the piles’ bearing capacities in comparison to the uncontaminated sand. With some modifications on the bearing capacity parameters of CFEM method, a good agreement was observed between measured and calculated bearing capacity values.  相似文献   
5.

Tunneling is often unpopular with local residents and environmentalists, and can cause aquifer damage. Tunnel sealing is sometimes used to avoid groundwater leakage into the tunnel, thereby mitigating the damage. Due to the high cost of sealing operations, a detailed hydrogeological investigation should be conducted as part of the tunneling project to determine the impact of sealing, and groundwater modeling is an accurate method that can aid decision-making. Groundwater-level drawdown induced by the construction of the Headrace water-conveyance tunnel in Sri Lanka dried up 456 wells. Due to resulting socio-environmental problems, tunnel sealing was decided as a remedy solution. However, due to the expectation of significant delays and high costs of sealing, and because the water pressure in the tunnel may prevent groundwater seepage into the tunnel during operation, there was another (counter) decision that the tunnel could remain unsealed. This paper describes groundwater modeling carried out using MODFLOW to determine which option—sealed or unsealed tunnel—is more effective in groundwater level recovery. The Horizontal Flow Barrier and River packages of MODFLOW were used to simulate sealed and unsealed tunnels, respectively. The simulation results showed that only through tunnel sealing can the groundwater level be raised to preexisting levels after 18 years throughout the study area. If the tunnel remains unsealed, about 1 million m3/year of water conveyed by the tunnel will seep into the aquifer, reducing the operational capacity of the tunnel as a transport scheme. In conclusion, partial tunnel sealing in high-impact sections is recommended.

  相似文献   
6.
IntroductionThesouthernpartofKhorasanProvinceineast-centralIranisoneoftheseismicallyactiveregionsintheMiddleeast.Historicalreportsindicatedseveralearthquakeshavecausedseveredestructionsandhumanlossinthisregionduringthepastcenturies(Ambraseys,Melville,1982).Theinstrumentallyrecordedearthquakesaswellastheexistenceofseveralactivefaultsalsosug-gestedthattheregionhadahighpotentialofseismicactivities.OnMay10,1997at07:57:29.6GMT,12:27:29.6localtime,ashallowdestructiveearthquakewithoutanyfeltfores…  相似文献   
7.
通过对1997年5月10日Zirkuh ( Ghaen-Birjand )破坏性地震若干余震横波分裂现象的观测，研究了该地区上地壳各向异性特征. 采用质点运动图和纵横比两种不同手段获取了横波分裂参数. 所选余震记录显示了明显的横波分裂，说明该地区介质具有强烈的各向异性. 通过质点运动的方法得出:快横波的偏振方向为22N19E；且快、慢横波的延时之差为6516 ms. 用纵横比的方法得到的结果为:快横波的偏振方向35N18E, 且快、慢横波的延时之差为(4910)ms. 对于厚约5 km各向异性均匀分布的水平层， 我们采用了一个沿应力分布的裂纹模型，并采用垂直于N22E排列, 且密度为0.01的裂纹情况来解释本文结果. 由于研究范围是上地壳，因此假设裂纹被水填充. 最后通过Hudson模型，对裂纹密度为0.005, 0.01和0.03的模型，给出横波速度随传播方向与裂纹对称轴夹角的变化曲线. 结果表明，当横波的偏振平行于裂纹表面时波速不随角度变化；而偏振垂直于裂纹表面时，速度曲线则有明显变化.   相似文献   
8.
A comparative discussion of the advantages and disadvantages of natural stands and plantations, including in terms of their productivity and stability, began from the moment of the first forest plantings and continues to this day. In the context of the progressive replacement of natural forests by plantations due to deforestation, the question of how will change the carbon storage capacity of forest cover when replacing natural forests with artificial ones in a changing climate becomes extremely relevant. This article presents the first attempt to answer this question at the transcontinental level on a special case for two-needled pine trees (subgenus Pinus L.). The research was carried out using the database compiled by the authors on the single-tree biomass structure of forest-forming species of Eurasia, in particular, data of 1880 and 1967 of natural and plantation trees, respectively. Multi-factor regression models are calculated after combining the matrix of initial data on the structure of tree biomass with the mean January temperature and mean annual precipitation, and their adequacy indices allow us to consider them reproducible. It is found that the aboveground and stem biomass of equal-sized and equal-aged natural and plantation trees increases as the January temperature and precipitation rise. This pattern is only partially valid for the branches biomass, and it has a specific character for the foliage one. The biomass of all components of plantation trees is higher than that of natural trees, but the percent of this excess varies among different components and depends on the level of January temperatures, but does not depend at all on the level of annual precipitation. A number of uncertainties that arose during the modeling process, as well as the preliminary nature of the obtained regularities, are noted.  相似文献   
9.
The Qom Formation is the most important hydrocarbon reservoir target in Central Iran. The Qom platform developed in a back-arc basin during the Oligo–Miocene due to the closing of the Tethyan Seaway. This formation consists of a variety of carbonate and non-carbonate facies deposited on a platform ranging from supratidal to basin. A combination of tectonic and eustatic events led to some lateral and vertical facies variations in the study area. Six third-order depositional sequences and related surfaces were identified regarding vertical facies changes in the studied sections of this Oligo–Miocene succession. According to all results and data, this succession was initially deposited during the Chattian upon a distally steepened ramp of siliciclastic-carbonate composition, including the Bouma sequence. Then, from the late Chattian to the Aquitanian, the platform changed into a homoclinal carbonate ramp with a gentle profile. With respect to tectonic activity, this phase was a calm period during the deposition of the Qom Formation. Finally, a drowned carbonate platform and a rimmed shelf emerged during the Burdigalian, terminated by the continental deposits of the Upper Red Formation. Regarding all geological characteristics, three main tectono-eustatic evolutionary phases have been recognized in the Qom back-arc basin.  相似文献   
10.
ABSTRACT

Albian–Cenomanian successions (Kazhdumi and Sarvak formations) represent remarkable variations in thickness, facies, fauna, and environments throughout the Zagros area. In the Coastal Fars (Charmu section), sedimentological and paleontological data evidence an intrashelf, with depths of 10s–100s m, surrounded by a shallow carbonate platform. Due to its depth, deposition of sequences in this setting has been controlled by eustatic sea-level changes rather than eurybathic changes, and several condensation episodes occurred related to marine transgressions. These observations are different from those in the adjacent sections in the Coastal Fars which recorded subaerial exposures instead. Combined with previous studies, this study denotes several intrashelf basins enclosed by a shallow carbonate platform on the southeastern margin of the Neo-Tethys during the Albian–Cenomanian. Development of intrashelf basins corresponds to basement faults in the Fars Salient. Likely, an extensional tectonic regime associated with a rifting event created horst–graben architecture by exerting extension along the basement faults and reactivating salt structures. Deposition on these troughs and highs led to the facies and thickness variations of the concomitant sequences. Development of several intrashelf basins on the southeastern margin of the Neo-Tethys indicates that syn-depositional continental rifting event could occur during the Albian–Cenomanian, prior to the tectonic inversion around the earliest Turonian.  相似文献   
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