Bioventing for in situ remediation     

MICHAEL D. LEE  C. MICHAEL SWINDOLL 《水文科学杂志》2013,58(4):273-282

Abstract

The availability of oxygen generally controls the rate at which aerobic in situ bioremediation proceeds. Bioventing, which couples soil venting with bioremediation, is often the most effective means of supplying oxygen to unsaturated zone soil. Laboratory treatability studies were conducted which showed that bioventing could be successfully applied to compounds ranging from light hydrocarbons, such as gasoline or diesel, to heavier hydrocarbons, such as fuel oils, as well as other volatile and semivolatile compounds. In many cases, the promotion of biological activity through the addition of nutrients and moisture, and optimization of the bioventing flow rates, may achieve greater contaminant reductions than venting alone.  相似文献   

Halite cementation and carbonate diagenesis of intra-salt reservoirs from the Late Neoproterozoic to Early Cambrian Ara Group (South Oman Salt Basin)   总被引：1，自引：0，他引：1  

JOHANNES SCHOENHERR  LARS REUNING†  PETER A. KUKLA†  RALF LITTKE‡  JANOS L. URAI  MICHAEL SIEMANN§  ZUWENA RAWAHI¶ 《Sedimentology》2009,56(2):567-589

Late Neoproterozoic to Early Cambrian carbonates of the Ara Group form important intra‐salt ‘stringer’ reservoirs in the South Oman Salt Basin. Differential loading of thick continental clastics above the six carbonate to evaporite cycles of the Ara Group led to the formation of salt diapirs, encasing a predominantly self‐charging hydrocarbon system within partly highly overpressured carbonate bodies (‘stringers’). These carbonates underwent a complex diagenetic evolution, with one stage of halite cementation in a shallow (early) and another in a deep (late) burial environment. Early and late halite cements are defined by their microstructural relationship with solid bitumen. The early phase of halite cementation is post‐dated by solid reservoir bitumen. This phase is most pervasive towards the top of carbonate stringers, where it plugs nearly all available porosity in facies with initially favourable poroperm characteristics. Bromine geochemistry revealed significantly higher bromine contents (up to 280 p.p.m.) in the early halite compared with the late halite (173 p.p.m.). The distribution patterns and the (high) bromine contents of early halite are consistent with precipitation caused by seepage reflux of highly saturated brines during deposition of the overlying rock salt interval. Later in burial history, relatively small quantities of early halite were dissolved locally and re‐precipitated as indicated by inclusions of streaky solid bitumen within the late halite cements. Late halite cement also seals fractures which show evidence for repeated reopening. Initially, these fractures formed during a period of hydrothermal activity and were later reopened by a crack‐seal mechanism caused by high fluid overpressures. Porosity plugging by early halite cements affects the poroperm characteristics of the Ara carbonates much more than the volumetrically less important late halite cement. The formation mechanisms and distribution patterns of halite cementation processes in the South Oman Salt Basin can be generalized to other petroliferous evaporite basins.  相似文献   

Morphology and evolution of bars in a wandering gravel-bed river; lower Fraser river, British Columbia, Canada   总被引：2，自引：0，他引：2  

STEPHEN P. RICE  MICHAEL CHURCH§  COLIN L. WOOLDRIDGE†  EDWARD J. HICKIN‡ 《Sedimentology》2009,56(3):709-736

A hierarchical typology for the channels and bars within aggradational wandering gravel-bed rivers is developed from an examination of a 50 km reach of lower Fraser River, British Columbia, Canada. Unit bars, built by stacking of gravelly bedload sheets, are the key dynamic element of the sediment transfer system, linking sediment transport during individual freshets to the creation, development and remoulding of compound bar platforms that have either a lateral or medial style. Primary and secondary unit bars are identified, respectively, as those that deliver sediment to compound bars from the principal channel and those that redistribute sediment across the compound bar via seasonal anabranches and smaller channels. The record of bar accretion evident in ground-penetrating radar sequences is consistent with the long-term development of bar complexes derived from historical aerial photographs. For two compound bars, inter-annual changes associated with individual sediment transport episodes are measured using detailed topographic surveys and longer-term changes are quantified using sediment budgets derived for individual bars from periodic channel surveys. Annual sediment turnover on the bars is comparable with the bed material transfer rate along the channel, indicating that relatively little bed material bypasses the bars. Bar construction and change are accomplished mainly by lateral accretion as the river has limited capacity to raise bed load onto higher surfaces. Styles of accretion and erosion and, therefore, the major bar form morphologies on Fraser River are familiar and consistent with those in gravelly braided channels but the wandering style does exhibit some distinctive features. For example, 65-year histories reveal the potential for long sequences of uninterrupted accretion in relatively stable wandering rivers that are unlikely in braided rivers.  相似文献   

Subaqueous density flow processes and deposits of an island volcano landslide (Stromboli Island, Italy)     

MICHAEL P. MARANI  FABIANO GAMBERI  MAURO ROSI§  ANTONELLA BERTAGNINI‡  ALESSIO DI ROBERTO§‡ 《Sedimentology》2009,56(5):1488-1504

Stromboli is a 3000 m high island volcano, rising to 900 m above sea-level. It is the most active volcano of the Aeolian Archipelago in the Tyrrhenian Sea (Italy). Major, large volume (1 km³) sector collapses, four occurring in the last 13 kyr, have played an important role in shaping the north-western flank (Sciara del Fuoco) of the volcano, potentially generating a high-risk tsunami hazard for the Aeolian Islands and the Italian coast. However, smaller volume, partial collapses of the Sciara del Fuoco have been shown to be more frequent tsunami-generating events. One such event occurred on 30 December 2002, when a partial collapse of the north-western flank of the island took place. The resulting landslide generated 10 m high tsunami waves that impacted the island. Multibeam bathymetry, side-scan sonar imaging and visual observations reveal that the landslide deposited 25 to 30 × 10⁶ m³ of sediment on the submerged slope offshore from the Sciara del Fuoco. Two contiguous main deposit facies are recognized: (i) a chaotic, coarse-grained (metre-sized to centimetre-sized clasts) deposit; and (ii) a sand deposit containing a lower, cross-bedded sand layer and an upper structureless pebbly sand bed capped by sea floor ripple bedforms. The sand facies develops adjacent to and partially overlying the coarse deposits. Characteristics of the deposits suggest that they were derived from cohesionless, sandy matrix density flows. Flow rheology and dynamics led to the segregation of the density flow into sand-rich and clast-rich regions. A range of density flow transitions, both in space and in time, caused principally by particle concentration and grain-size partitioning within cohesionless parent flows was identified in the deposits of this relatively small-scale submarine landslide event.  相似文献   

A 12.5-kyr history of vegetation dynamics and mire development with evidence of Younger Dryas larch presence in the Verkhoyansk Mountains, East Siberia, Russia     

KIRSTIN WERNER  PAVEL E. TARASOV  REI A. ANDREEV  STEFANIE MÜLLER  FRANK KIENAST  MICHAEL ZECH  WOLFGANG ZECH  BERNHARD DIEKMANN 《Boreas: An International Journal of Quaternary Research》2010,39(1):56-68

Werner, K., Tarasov, P. E., Andreev, A. A., Müller, S., Kienast, F., Zech, M., Zech, W. & Diekmann, B. 2009: A 12.5‐kyr history of vegetation dynamics and mire development with evidence of Younger Dryas larch presence in the Verkhoyansk Mountains, East Siberia, Russia. Boreas, 10.1111/j.1502‐3885.2009.00116.x. ISSN 0300‐9483. A 415 cm thick permafrost peat section from the Verkhoyansk Mountains was radiocarbon‐dated and studied using palaeobotanical and sedimentological approaches. Accumulation of organic‐rich sediment commenced in a former oxbow lake, detached from a Dyanushka River meander during the Younger Dryas stadial, at ～12.5 kyr BP. Pollen data indicate that larch trees, shrub alder and dwarf birch were abundant in the vegetation at that time. Local presence of larch during the Younger Dryas is documented by well‐preserved and radiocarbon‐dated needles and cones. The early Holocene pollen assemblages reveal high percentages of Artemisia pollen, suggesting the presence of steppe‐like communities around the site, possibly in response to a relatively warm and dry climate ～11.4–11.2 kyr BP. Both pollen and plant macrofossil data demonstrate that larch woods were common in the river valley. Remains of charcoal and pollen of Epilobium indicate fire events and mark a hiatus ～11.0–8.7 kyr BP. Changes in peat properties, C31/C27 alkane ratios and radiocarbon dates suggest that two other hiatuses occurred ～8.2–6.9 and ～6.7–0.6 kyr BP. Prior to 0.6 kyr BP, a major fire destroyed the mire surface. The upper 60 cm of the studied section is composed of aeolian sands modified in the uppermost part by the modern soil formation. For the first time, local growth of larch during the Younger Dryas has been verified in the western foreland of the Verkhoyansk Mountains (～170 km south of the Arctic Circle), thus increasing our understanding of the quick reforestation of northern Eurasia by the early Holocene.  相似文献   

Properties of dust aerosol particles transported to Portugal from the Sahara desert   总被引：1，自引：0，他引：1  

FRANK WAGNER  DANIELE BORTOLI  SÉRGIO PEREIRA  MARIA JOÃO COSTA  ANA MARIA SILVA  BERNADETT WEINZIERL  MICHAEL ESSELBORN  REAS PETZOLD  KATHI RASP  BERND HEINOLD  INA TEGEN 《Tellus. Series B, Chemical and physical meteorology》2009,61(1):297-306

Aerosol properties of mineral particles in the far field of an African desert dust outbreak were investigated that brought Saharan dust over the Mediterranean in different layers to Portugal. The measurements were performed inside the project Desert Aerosols over Portugal (DARPO) which was linked to the Saharan Mineral Dust Experiment (SAMUM). The maximum particle mass concentration was about 150 μg m⁻³ and the corresponding scattering coefficient was 130 M m⁻¹ which results in a mass scattering efficiency of 0.87 m² g⁻¹. The aerosol optical depth reached values up to 0.53 and the lidar ratio was between 45 and 50 in the whole dust loaded column. A comparison between particle size distributions and refractive indices derived from different instruments and models showed a general good agreement but some minor differences could also be observed. Measurements as well as calculations with a particle transport model suggest that there is a relatively higher concentration of very large particles in the upper region of the dust layer than on the surface which is likely connected with meteorological conditions at the observational site (Évora, Portugal).  相似文献   

A MODELLING RECONSTRUCTION OF THE LAST GLACIAL MAXIMUM ICE SHEET AND ITS DEGLACIATION IN THE VICINITY OF THE NORTHERN PATAGONIAN ICEFIELD, SOUTH AMERICA     

ALUN HUBBARD  REW S. HEIN  MICHAEL R. KAPLAN  NICK R.J. HULTON  NEIL GLASSER 《Geografiska Annaler: Series A, Physical Geography》2005,87(2):375-391

ABSTRACT. A time-dependent model is used to investigate the interaction between climate, extent and fluctuations of Patagonian ice sheet between 45° and 48°S during the last glacial maximum (LGM) and its subsequent deglaciation. The model is applied at 2 km resolution and enables ice thickness, lithospheric response and ice deformation and sliding to interact freely and is perturbed from present day by relative changes in sea level and equilibrium line altitude (ELA). Experiments implemented to identify an LGM configuration compatible with the available empirical record, indicate that a stepped ELA lowering of 750 to 950 m is required over 15000 years to bracket the Fenix I-V suite of moraines at Lago Buenos Aires. However, 900 m of ELA lowering yields an ice sheet which best matches the Fenix V moraine (c. 23000 a BP) and Caldenius' reconstructed LGM limit for the entire modelled area. This optimum LGM experiment yields a highly dynamic, low aspect ice sheet, with a mean ice thickness of c. 1130 m drained by numerous large ice streams to the western, seaward margin and two large, fast-flowing outlet lobes to the east. Forcing this scenario into deglaciation using a re-scaled Vostok ice core record results in an ice sheet that slowly shrinks by 25% to c. 14500 a bp , after which it experiences a rapid collapse, loosing some 85% of its volume in c. 800 years. Its margins stabilize during the Antarctic Cold Reversal after which it shrinks to near present-day limits by 11 000 a bp .  相似文献   

Mass movement-induced fold-and-thrust belt structures in unconsolidated sediments in Lake Lucerne (Switzerland)   总被引：2，自引：0，他引：2  

MICHAEL SCHNELLMANN  FLAVIO S. ANSELMETTI  DOMENICO GIARDINI†  JUDITH A. McKENZIE 《Sedimentology》2005,52(2):271-289

High-resolution seismic imaging and piston coring in Lake Lucerne, Switzerland, have revealed surprising deformation structures in flat-lying, unconsolidated sediment at the foot of subaqueous slopes. These deformation structures appear beneath wedges of massflow deposits and resemble fold-and-thrust belts with basal décollement surfaces. The deformation is interpreted as the result of gravity spreading induced by loading of the slope-adjacent lake floor during massflow deposition. This study investigated four earthquake-triggered lateral mass-movement deposits in Lake Lucerne affecting four sections of the lake floor with areas ranging from 0·25 to 6·5 km² in area. Up to 6 m thick sediment packages draping the subaqueous slopes slid along the acoustic basement. The resulting failure scars typically lie in water depths of >30 m on slopes characterized by downward steepening and inclinations of >10°. From the base-of-slope to several hundred metres out onto the flat plains, the wedges of massflow deposits overlie deeply (10–20 m) deformed basin-plain sediment characterized by soft sediment fold-and-thrust belts with arcuate strikes and pronounced frontal thrusts. The intensity of deformation decreases towards the more external parts of the massflow wedges. Beyond the frontal thrust, the overridden lake floor remains mostly undisturbed. Geometrical relationships between massflow deposits and the deformed basin-plain sediment indicate that deformation occurred mainly during massflow deposition. Gravity spreading induced by the successive collapse of the growing slope-adjacent massflow wedge is proposed as the driving mechanism for the deformation. The geometry of fjord-type lakes with sharp lower slope breaks favours the deposition of thick, basin-marginal massflow wedges, that effectively load and deform the underlying sediment. In the centre of the basins, the two largest massflow deposits described are directly overlain by thick contained (mega-)turbidites, interpreted as combined products of the suspension clouds set up by subaqueous mass movements and related tsunami and seiche waves.  相似文献   

Solution-collapse breccias of the Minkinfjellet and Wordiekammen Formations, Central Spitsbergen, Svalbard: a large gypsum palaeokarst system   总被引：3，自引：0，他引：3  

ARILD ELIASSEN  MICHAEL R. TALBOT 《Sedimentology》2005,52(4):775-794

Large volumes of carbonate breccia occur in the late syn-rift and early post-rift deposits of the Billefjorden Trough, Central Spitsbergen. Breccias are developed throughout the Moscovian Minkinfjellet Formation and in basal parts of the Kazimovian Wordiekammen Formation. Breccias can be divided into two categories: (i) thick, cross-cutting breccia-bodies up to 200 m thick that are associated with breccia pipes and large V-structures, and (ii) horizontal stratabound breccia beds interbedded with undeformed carbonate and siliciclastic rocks. The thick breccias occur in the central part of the basin, whereas the stratabound breccia beds have a much wider areal extent towards the basin margins. The breccias were formed by gravitational collapse into cavities formed by dissolution of gypsum and anhydrite beds in the Minkinfjellet Formation. Several dissolution fronts have been discovered, demonstrating the genetic relationship between dissolution of gypsum and brecciation. Textures and structures typical of collapse breccias such as inverse grading, a sharp flat base, breccia pipes (collapse dolines) and V-structures (cave roof collapse) are also observed. The breccias are cemented by calcite cements of pre-compaction, shallow burial origin. Primary fluid inclusions in the calcite are dominantly single phase containing fresh water (final melting points are ca 0 °C), suggesting that breccia diagenesis occurred in meteoric waters. Cathodoluminescence (CL) zoning of the cements shows a consistent pattern of three cement stages, but the abundance of each stage varies stratigraphically and laterally. δ¹⁸O values of breccia cements are more negative relative to marine limestones and meteoric cements developed in unbrecciated Minkinfjellet limestones. There is a clear relationship between δ¹⁸O values and the abundance of the different cement generations detected by CL. Paragenetically, later cements have lower δ¹⁸O values recording increased temperatures during their precipitation. Carbon isotope values of the cements are primarily rock-buffered although a weak trend towards more negative values with increasing burial depth is observed. The timing of gypsum dissolution and brecciation was most likely related to major intervals of exposure of the carbonate platform during Gzhelian and/or Asselian/Sakmarian times. These intervals of exposure occurred shortly after deposition of the brecciated units and before deep burial of the sediments.  相似文献   

On the transition between 2D and 3D dunes   总被引：3，自引：0，他引：3  

JEREMY G. VENDITTI  MICHAEL CHURCH  SEAN J. BENNETT† 《Sedimentology》2005,52(6):1343-1359

Sediment transport in sand-bedded alluvial channels is strongly conditioned by bedforms, the planimetric morphology of which can be either two- or three-dimensional. Experiments were undertaken to examine the processes that transform the bed configuration from two-dimensional (2D) dunes to three-dimensional (3D) dunes. A narrowly graded, 500 μm size sand was subjected to a 0·15 m deep, non-varying mean flow ranging from 0·30 to 0·55 m sec⁻¹ in a 1 m wide flume. Changes in the planimetric configuration of the bed were monitored using a high-resolution video camera that produced a series of 10 sec time-lapsed digital images. Image analysis was used to define a critical value of the non-dimensional span (sinuosity) of the bedform crestlines that divides 2D forms from 3D forms. Significant variation in the non-dimensional span is observed that cannot be linked to properties of the flow or bedforms and thus appears random. Images also reveal that, once 2D bedforms are established, minor, transient excesses or deficiencies of sand are passed from one bedform to another. The bedform field appears capable of absorbing a small number of such defects but, as the number grows with time, the resulting morphological perturbations produce a transition in bed state to 3D forms that continue to evolve, but are pattern-stable. The 3D pattern is maintained by the constant rearrangement of crestlines through lobe extension and starving downstream bedforms of sediment, which leads to bifurcation. The experiments demonstrate that 2D bedforms are not stable in this calibre sand and call into question the reliability of bedform phase diagrams that use crestline shape as a discriminator.  相似文献