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951.
Recent studies have indicated that in situ aerobic bioremediation is one of the most effective methods for remediating groundwater contaminated with nitrobenzene (NB). Aerobic bioremediation is largely dependent on the maintenance of adequate dissolved oxygen (DO) levels in the groundwater. Traditional in situ aeration has various disadvantages, such as high operational costs and nonuniform aeration. In this study, integrative cubes were prepared and utilized as a novel biological permeable reactive barrier (bio-PRB) medium to enhance the aerobic bioremediation of NB-contaminated groundwater. The results revealed an NB removal rate greater than 98.68% after 15–20 days of continuous oxygen release from the bio-PRB medium. DO concentrations reached 8.0 mg/L during treatment, and NB-degrading bacteria were able to tolerate a range of pH conditions. This multifaceted bio-PRB medium can simultaneously adsorb and biodegrade NB, release oxygen, and neutralize the pH with phosphate buffer. The results of this study suggest that this bio-PRB medium represents a highly effective in situ bioremediation method for NB-contaminated groundwater. 相似文献
952.
Elke Schneebeli-Hermann Nathan Looser Peter A. Hochuli Heinz Furrer Achim G. Reisdorf Andreas Wetzel Stefano M. Bernasconi 《Swiss Journal of Geoscience》2018,111(1-2):99-115
A first palynostratigraphic scheme of Upper Triassic deposits in northern Switzerland was established based on spore-pollen associations and dinoflagellate cyst records from the upper part of the Upper Triassic Klettgau Formation and the lower part of the Lower Jurassic Staffelegg Formation. Drill cores from the Adlerberg region (Basel Tabular Jura) and from Weiach (northern part of Canton Zurich) as well as from an outcrop at the Chilchzimmersattel (Basel Folded Jura) were studied and five informal palynological associations are distinguished. These palynological associations correlate with palynological association of the Central European Epicontinental Basin and the Tethyan realm and provide a stratigraphic framework for the uppermost Triassic sediments in northern Switzerland. Throughout the uppermost Triassic to Jurassic palynological succession a remarkable prominence of Classopollis spp. is observed. Besides Classopollis spp. the three Rhaetian palynological associations A to C from the Upper Triassic Belchen Member include typical Rhaetian spore-pollen and dinoflagellate taxa (e.g., Rhaetipollis germanicus, Geopollis zwolinskae, Rhaetogonyaulax rhaetica, and Dapcodinium priscum). Association B differs from association A in a higher relative abundance of the sporomorph taxa Perinopollenites spp. and the consistent occurrence of Granuloperculatipollis rudis and Ricciisporites tuberculatus. Spore diversity is highest in the late Rhaetian palynological association C and includes Polypodiisporites polymicroforatus. A Rhaetian age for the Belchen Member is confirmed by palynological associations A–C, but there is no record of the latest Rhaetian and the earliest Jurassic. In contrast to the Rhaetian palynological associations the Early Jurassic associations W and D include Pinuspollenites spp., Trachysporites fuscus (in association W), and Ischyosporites variegatus. In the view of the end-Triassic mass extinction and contemporaneous environmental changes the described palynofloral succession represents the pre-extinction phase (associations A and B) including a distinct transgression, the extinction phase (association C) associated with a regression, and the post-extinction phase (association W). 相似文献
953.
Mohammad Ashtari Jafari 《Natural Hazards》2007,42(1):237-252
The Bayesian probability estimation seems to have efficiencies that make it suitable for calculating different parameters
of seismicity. Generally this method is able to combine prior information on seismicity while at the same time including statistical
uncertainty associated with the estimation of the parameters used to quantify seismicity, in addition to the probabilistic
uncertainties associated with the inherent randomness of earthquake occurrence. In this article a time-independent Bayesian
approach, which yields the probability that a certain cut-off magnitude will be exceeded at certain time intervals is examined
for the region of Alborz, Iran, in order to consider the following consequences for the city of Tehran. This area is located
within the Alpine-Himalayan active mountain belt. Many active faults affect the Alborz, most of which are parallel to the
range and accommodate the present day oblique convergence across it. Tehran, the capital of Iran, with millions of inhabitants
is located near the foothills of the southern Central Alborz. This region has been affected several times by historical and
recent earthquakes that confirm the importance of seismic hazard assessment through it. As the first step in this study an
updated earthquake catalog is compiled for the Alborz. Then, by assuming a Poisson distribution for the number of earthquakes
which occur at a certain time interval, the probabilistic earthquake occurrence is computed by the Bayesian approach. The
highest probabilities are found for zone AA and the lowest probabilities for zones KD and CA, meanwhile the overall probability
is high. 相似文献
954.
Limitations of real-time models for forecasting river flooding from monsoon rainfall 总被引:1,自引:0,他引:1
Very intense rainfall during the southwest and northeast monsoons causes severe river flooding in India. Some traditional
techniques used for real-time forecasting of flooding involve the relationship between effective rainfall and direct surface
runoff, which simplifies the complex interactions between rainfall and runoff processes. There are, however, serious problems
in deducing these variables in real time, so it is highly desirable to have a real-time flood forecasting model that would
directly relate the observed discharge hydrograph to the observed rainfall. The storage routing model described by Baba and
Hoshi (1997), Tanaka et al. (1997), and Baba et al. (2000), and a simplified version of this model, have been used to compute observed river discharge directly from observed hourly
rainfall. This method has been used to study rainfall–runoff data of the Ajay River Basin in eastern India. Five intense rainfall
events of this basin were studied. Our results showed that the Nash–Sutcliffe efficiency of discharge prediction for these
five events was 98.6%, 94.3%, 86.9%, 85.6%, and 67%. The hindcast for the first two events is regarded as completely satisfactory
whereas for the next two events it is deemed reasonable and for the fifth it is unsatisfactory. It seems the models will yield
accurate hindcast if the rainfall is uniform over the drainage basin. When the rainfall is not uniform the performance of
the model is unsatisfactory. In future this problem can, in principle, be corrected by using a weighted amount if rainfall
is based upon multiple rain-gauge observations over the drainage basin. This would provide some measure of the dispersion
in the rainfall. The model also seems unable to simulate flooding events with multiple peaks. 相似文献
955.
Fish are a key part of the marine ecosystem likely to be affected by hydrokinetic tidal turbines, but little is known about their behavior around such obstacles in the natural environment. In September 2010, two DIDSON acoustic cameras were used to observe fish interactions with a commercial-scale turbine in Cobscook Bay, Maine. Twenty-two hours (nearly two tidal cycles) of footage were collected. Behaviors of individual fish and schools were classified (e.g., entering, avoiding, passing, or remaining in the wake of the turbine). We analyzed the effects of turbine motion (rotating or not rotating), diel condition (day or night), and fish size (small, ≤10 cm; large, >10 cm) on individual fish behaviors, and compared behaviors of individual fish to schools of fish. When the turbine was rotating, the probability of fish entering the turbine decreased by over 35 % from when it was not. The probability that fish would enter the turbine was higher at night than during the day, and this difference was greater for small fish than for large fish (probability of small fish entering?=?0.147 day, 0.513 night; large fish?=?0.043 day, 0.333 night). Fish were almost always present in the wake of the turbine. Schools of fish had a 56 % lower probability of entering the turbine than individual fish, and reacted at greater distances from the turbine (median distance of 2.5 m for schools, 1.7 m for individuals). This study indicates that fish behavior in response to tidal turbines appears to be similar to responses to obstacles such as trawls, and highlights the importance of environmental context in determining the effects of a tidal turbine on fish. 相似文献
956.
Broadband seismic networks are becoming more intensive, generating a large amount of data in the long-term collection process. When processing the data, the researchers rely almost on instrument response files to understand the information related to the instrument. Aiming at the process of instrument response recording and instrument response correction, we identify several sources of the instrument response phase error, including pole–zero change, the causality difference in instrument correction method, and the problem of filter coefficient recording. The data time offset range from the instrument response phase error is calculated from one sample point to several seconds using the ambient noise data recorded by multiple seismic stations. With different data delays, the time offset of the noise correlation function is estimated to be 74% to 99% of the data delay time. In addition, the influence of instrument response phase error on the measurement of seismic velocity change is analyzed by using ambient noise data with pole–zero change, and the results show that the abnormal wave velocity with exceeding the standard value is exactly in the time period of the instrument response error, which indicates that the instrument response error affects the study of seismology. 相似文献
957.
By using small scale model tests, the interference effect on the vertical load-deformation behavior of a number of equally
spaced strip footings, placed on the surface of dry sand, was investigated. At any stage, all the footings were assumed to
(i) carry exactly equal magnitude of load, and (ii) settle to the same extent. No tilt of the footing was permitted. The effect
of clear spacing (s) among footings on the results was explored. A new experimental setup was proposed in which only one footing
needs to be employed rather than a number of footings. The bearing capacity increases continuously with decrease in spacing
among the footings. The interference effect becomes further prominent with increase in soil friction angle. In contrast to
an increase in the bearing capacity, with decrease in spacing of footings, an increase in the footing settlement associated
with the ultimate state of shear failure was observed. The present experimental observations were similar to those predicted
by the available theory, based on the method of characteristics. As compared to the theory, the present experimental data,
however, indicates much greater effect of interference especially for larger spacing among footings. 相似文献
958.
Mirta Garrido Fernando Barra Eduardo Domínguez Joaquin Ruiz Victor A. Valencia 《Mineralium Deposita》2008,43(5):591-597
The La Voluntad porphyry Cu–Mo deposit in Neuquén, Argentina, is one of several poorly known porphyry-type deposits of Paleozoic
to Early Jurassic age in the central and southern Andes. Mineralization at La Voluntad is related to a tonalite porphyry from
the Chachil Plutonic Complex that intruded metasedimentary units of the Piedra Santa Complex. Five new Re–Os molybdenite ages
from four samples representing three different vein types (i.e., quartz–molybdenite, quartz–sericite–molybdenite and quartz–sericite–molybdenite
± chalcopyrite–pyrite) are identical within error and were formed between ~312 to ~316 Ma. Rhenium and Os concentrations range
between 34 to 183 ppm and 112 to 599 ppb, respectively. The new Re–Os ages indicate that the main mineralization event at
La Voluntad, associated to sericitic alteration, was emplaced during a time span of 1.7 ± 3.2 Ma and that the deposit is Carboniferous
in age, not Permian as previously thought. La Voluntad is the oldest porphyry copper deposit so far recognized in the Andes
and indicates the presence of an active magmatic arc, with associated porphyry style mineralization, at the proto-Pacific
margin of Gondwana during the Early Pennsylvanian. 相似文献
959.
Multivariate statistical techniques, i.e., correlation coefficient analysis, principal components analysis (PCA), and hierarchical
cluster analysis (CA), were applied to the total and water-soluble concentrations of potentially hazardous metals in sediments
associated with the Sarcheshmeh mine, one of the largest Oligo-Miocene porphyry copper deposits in the world. The samples
were analyzed for hazardous metal concentration levels by inductively coupled plasma mass spectrometry method. Results indicate
that the contaminant metals As, Cd, Cu, Mo, S, Sb, Sn, Se, Pb, and Zn were positively correlated with the total concentrations.
These hazardous metals also have strong association in the PCA and CA results. Different anthropic versus natural sources
of contaminant metals were distinguished by using CA method. Water-soluble fraction of hazardous metals showed that the hydro-geochemical
behavior of these metals in sediments is different considerably. Elements such as Cd, Co, Cr, Cu, Fe, Mn, Ni, S, and Zn are
readily water soluble from contaminated samples, especially from evaporative mineral phases, while the release of As, Mo,
Sb, and Pb into the water is limited by adsorption processes. Results obtained from the application of multivariate techniques
on the water-soluble fraction data set show that the hazardous metals are categorized into three groups including (1) Ni,
S, Co, Cu, Cr, and Fe; (2) Se, Mn, Cd, and Zn; and (3) Sb, As, Mo, and Sn. This classification describes the hydro-geochemical
behavior of hazardous metals in water–sediment environments of the Sarcheshmeh porphyry copper mine and can be used as a basis
in remedial and treatment strategies. 相似文献
960.
Juan M. Jiménez Kazimierz Więski Laurie B. Marczak Chuan-Kai Ho Steven C. Pennings 《Estuaries and Coasts》2012,35(2):475-485
Top–down and bottom–up effects interact to structure communities, especially in salt marshes, which contain strong gradients
in bottom–up drivers such as salinity and nutrients. How omnivorous consumers respond to variation in prey availability and
plant quality is poorly understood. We used a mesocosm experiment to examine how salinity, nutrients, an omnivore (the katydid
Orchelimum fidicinium) and an herbivore (the planthopper Prokelisia spp.) interacted to structure a simplified salt marsh food web based on the marsh grass Spartina alterniflora. Bottom–up effects were strong, with both salinity and nutrients decreasing leaf C/N and increasing Prokelisia abundance. Top–down effects on plants were also strong, with both the herbivore and the omnivore affecting S. alterniflora traits and growth, especially when nutrients or salt were added. In contrast, top–down control by Orchelimum of Prokelisia was independent of bottom–up conditions. Orchelimum grew best on a diet containing both Spartina and Prokelisia, and in contrast to a sympatric omnivorous crab, did not shift to an animal-based diet when prey were present, suggesting
that it is constrained to consume a mixed diet. These results suggest that the trophic effects of omnivores depend on omnivore
behavior, dietary constraints, and ability to suppress lower trophic levels, and that omnivorous katydids may play a previously
unrecognized role in salt marsh food webs. 相似文献