ALBERT

Notes: 1. Microbial parameters were determined at five sampling sites in the River Danube up-and downstream of Vienna, Austria, twice monthly over an annual cycle. Bacterial production (BP) was estimated from thymidine and leucine incorporations; additionally, the effect of turbulence on BP and the conversion factors for converting incorporation rates into bacterial cell production were determined using the cumulative approach.2. BP under turbulent conditions was not significantly different from that under stagnant conditions. For thymidine, a mean annual conversion factor of 3.2 ± 1018 cells mol−1 thymidine incorporated was calculated. For leucine, the corresponding factor was 0.07 ± 1018 cells mol−1 leucine. Average annual BP calculated by thymidine incorporation was significantly higher than BP calculated from leucine incorporation and ranged from 47.2 to 77.5 μg C 1-−1 day−1 depending on the tracer and the conversion factor used.3. Bacterial growth rates ranged from 0.1 day−1 during winter to 1.7 day−1 in the summer. A strong correlation was found between temperature as well as chlorophyll a and bacterial growth when temperature was greater than 5 °C; a major spring phytoplankton bloom at a temperature below 5 °C did not increase BP.4. Dissolved organic carbon (DOC) concentrations varied between 2 and 7.2 mg C 1-−1 and comprised between 50 and 92% of the total organic carbon pool in the River Danube, Based on the DOC concentration and an assumed bacterial growth yield of 20% we calculated mean DOC turnover times of around 60 days in the winter and less than 8 days during the summer.

Notes: This study examines the effectiveness of various waterflooding strategies to recover pooled dense nonaqueous phase liquid (DNAPL) from the subsurface at an industrial facility. The relative influence of horizontal injection/recovery well configuration, established hydraulic gradient, and fluid properties is investigated for a site characterized by a homogeneous silty sand underlain by an impermeable clay layer. The top of the clay layer is located 5 m below the water table and supports a laterally extensive 2 m deep DNAPL pool. The sensitivity study employs a two-phase flow numerical model that simulates both DNAPL infiltration and redistribution, including the formation of immobilized DNAPL residual. This is accomplished with constitutive relations featuring hysteretic capillary pressure-saturation pathways in which the local amount of residual formed is a function of the maximum non-wetting saturation attained during infiltration. Sixteen simulations, performed in two-dimensional vertical cross-section, demonstrate that strategies effecting increased wetting phase gradients, namely increasing drawdown at the recovery drain, adding injection wells, and reducing their distance to the recovery drain, result in an increased DNAPL volume recovered with time at the expense of increased volumes of ground water removed per unit volume of DNAPL recovered. Strategies which do not increase wetting phase gradients result in DNAPL recovery with a minimum volume of produced contaminated ground water. Three pulsed pumping simulations indicate that increasing the length of pump shut-down time decreases the recovery of DNAPL with time but increases efficiency with respect to ground water pumped. Decreased nonwetting density and increased interfacial tension result in poorer DNAPL recovery with respect to both time and volume of ground water removed, while reduced nonwetting viscosity corresponds to dramatically increased efficiency in both respects.

Notes: The Xinmincun Formation forms the uppermost unit of a thick Neoproterozoic section which accumulated near the east margin of the North China Block and is overlain by two thin nearshore to continental formations below fossiliferous Lower Cambrian sediments. Although tectonically deformed, sedimentary structures are preserved undeformed on cleavage-parallel surfaces, and an 80 m section has been reconstructed by correlation across minor folds and faults in the Golden Stone beach area, 50 km NE of the city of Dalian, southern Liaoning province.The measured section shows 65 m of storm-dominated deposits, consisting of alternations of micrites and sharp-based graded intraclastic grainstone beds (tempestites), some with rudaceous, commonly erosional or guttered, bases. The top 15 m of section shows three alternations of similar subtidal lithofacies with partly to completely dolomitized peritidal deposits (laminated, sometimes fenestral and desiccated, micrite beds, and intraclastic rudite and grainstone beds). Tempestite beds become thinner and less abundant upwards towards a muddy upper shoreface zone. This environment was characterized in part by the occurrence of micrite with thin or streaky lamination (probable storm-resuspended sediment), interbedded tempestites, numerous erosion surfaces, and evidence of liquidization and sediment slumping into hollows.Molar tooth structures are widespread in micrite beds of the Xinmincun Formation and are present in lesser abundance in tempestites and liquefied channel-fills. Originally the structures were sub-vertical cracks, 1–20 cm long, tapering upwards and downwards. Subsequently they became filled with microspar cement and buckled rigidly during compaction of surrounding sediment during burial. Evidence of repeated episodes of cracking, presence of brecciated cracks and localization of cracking within beds, together with variable degree of development and variation of preferential alignment in plan indicates a mechanical origin. Crack generation may have been by seismic surface waves generated by movement along faults defining either the basin's margins or its internal structure, or possibly by wave action during storms. A seismic origin for molar tooth structure is consistent with other Neoproterozoic occurrences. Their preferential occurrence in Precambrian deposits arises from the relative rigidity of micritic sediment at this time related to lack of bioturbation, incipient cementation and possibly microbial binding.

Notes: In growing sedimentary sequences range and velocity of vertically ascending pore water (advection) can be determined quantitatively by using a simple graphical method. During continuing deposition and maintenance of compaction equilibrium, the pore water from deeper layers cannot reach the sediment-water interface. Range and velocity of advective flow decrease from top to bottom of a sequence and depend on the thickness affected by compaction. The velocity of pore water flow as well as the transport of solutes by advective flux are proportional to the sedimentation rate. Compaction flow can also result from under-con-solidation and diagenetic reduction of pore space. At the sediment-water interface, a direct contact between the ascending pore water and the overlying water body is feasible only under special conditions (interrupted sedimentation over under-consolidated material, erosion). These results are demonstrated on geometric models of sedimentary sequences, on experimentally deposited clay, and on selected examples of the Deep Sea Drilling Project.

Notes: A new occurrence of Recent stromatolites different from those known up to now has been discovered on tidal flats of the Bay of Saint-Jean (near Cape Timiris). Their most remarkable features are predominance of quartz sand instead of carbonate, characteristic surface-contouring by grazing fish, absence of cementation, intensive reworking by crabs, and connection with saline sabkha deposits.Entrapment of sand grains and great resistance of the algal sheaths are most important for stromatolitic growth, although today destruction appears to prevail over accretion. Quartz sand of aeolian dunes and carbonatic pellets of aragonitic ooze feeders are the main constituents of the stromatolitic sediments.According to the tidal range the following zonation of the algal mat exists: (A) knoll and cuspate zone, (B) flat zone, (C) gas-domed zone, and (D) crinkle zone.