The Effect of Plunging Water of Waves on the Entrainment of Spilled Oil at Sea

Water Resources - The study of oil entrainment mechanism is the basis of the vertical process modeling of spilled oil at sea. In order to reveal the effect of plunging breaking waves, a dripping...     

An Analysis of Nitrate-Nitrogen in Ground Water Beneath Unsewered Subdivisions

Water samples from private water supply wells in five unsewered subdivisions were tested for nitrate-nitrogen to determine the possible impact of septic systems on ground water quality. Three subdivisions are located in Eau Claire County and two in LaCrosse County, Wisconsin.
The nitrate-nitrogen concentrations in the wells were analyzed in relation to ground water flow direction, the location of septic systems within the subdivision, and the hydrogeologic and physical characteristics of the subdivisions. A comparison of three nitrogen mass balance models helped to identify the possible sources of nitrate-nitrogen in the wells.
The results indicate that nitrogen from septic systems and lawn fertilizer cause nitrate-nitrogen to increase in the ground water beneath the downgradient side of the subdivisions. In three of the five subdivisions the highest nitrate-nitrogen value exceeds the drinking water standard of 10 mg/L.     

Electrical Structure of the Crust Beneath the Ordos Block

The Ordos block is a stable tectonic unit since the Cenozoic. Whether low-resistivity layers exist in the middle and lower crust of this kind block is an open question. This work attempts to reveal the entire crustal structure of the block based on interpretation of magnetotelluric data collected along the profile across this region. The result shows that a layered structure characterizes the crust of the Ordos block, with a low-resistivity layer at depth of about 20km, presumably associated with fluids there. In contrast, in the areas of active tectonics on the east and west of the block, there are no such layered electric structures in the crust, and the low-resistivity zones may be related to the decollement zones (or ductile shear zones) in the crust. The difference in electric structure of crust between the Ordos Block and neighboring areas is of significance to analyze the movement and deformation of varied blocks in the continent.     

Reconstruction of the Water Table from Self-Potential Data: A Bayesian Approach

Ground water flow associated with pumping and injection tests generates self-potential signals that can be measured at the ground surface and used to estimate the pattern of ground water flow at depth. We propose an inversion of the self-potential signals that accounts for the heterogeneous nature of the aquifer and a relationship between the electrical resistivity and the streaming current coupling coefficient. We recast the inversion of the self-potential data into a Bayesian framework. Synthetic tests are performed showing the advantage in using self-potential signals in addition to in situ measurements of the potentiometric levels to reconstruct the shape of the water table. This methodology is applied to a new data set from a series of coordinated hydraulic tomography, self-potential, and electrical resistivity tomography experiments performed at the Boise Hydrogeophysical Research Site, Idaho. In particular, we examine one of the dipole hydraulic tests and its reciprocal to show the sensitivity of the self-potential signals to variations of the potentiometric levels under steady-state conditions. However, because of the high pumping rate, the response was also influenced by the Reynolds number , especially near the pumping well for a given test. Ground water flow in the inertial laminar flow regime is responsible for nonlinearity that is not yet accounted for in self-potential tomography. Numerical modeling addresses the sensitivity of the self-potential response to this problem.     

Mantle Transition Zone Structure Beneath Southeastern China and its Implications for Stagnant Slab and Water Transportation in the Mantle

We determined depth variation of the 410- and 660-km discontinuities beneath southeastern China by common-converted-point stacking of \(\rm P\) -wave receiver functions of 121 permanent Chinese seismic stations. We then combined the results with seismic velocity variation to estimate temperature and water content variations in the mantle transition zone of the region. Previous tomographic studies have shown a stagnant slab in the mantle transition zone in eastern Asia that is connected to subduction of the western Pacific. Temperature variations obtained clearly outline the shape of the stagnant slab, with its western edge at 113.5 \(^\circ\) E and the southern edge at 28.5 \(^\circ\) N. The correlation between the location of the stagnant slab and surface tectonics suggests that the Cenozoic extension in eastern China is closely associated with the subduction of the western Pacific and its eastward migration. The water content of the stagnant slab is lower than in surrounding slabs, suggesting that the water has already been released from the subducting slab into the upper mantle.     

Study on the Effects of Waves and Dispersant on the Submergence of Spilled Oil

Water Resources - The baffled flasks were used to simulate regular wave and breaking wave at different oscillation intensities to study the effects of wave strength, reaction time, and dispersant...     

Environmental Hazard Ranking of Chemicals Spilled in the Rhine River in November 1986

In 1986 a chemical spill took place from the Sandoz plant in Basel, Switzerland, into the Rhine River. Several chemicals entered the river and were transported downstream. In this paper we rank the environmental hazard of eight chemicals, Disulfoton, Dinitroorthocresol, Propetamphos, Thiometon, Parathion, Etrimphos, Metoxuron and Fenitrothion found in the German section of the Rhine River. Five attributes related to the toxicity, physio-chemical characteristics and fate are used to rank the chemicals. The fate attributes were derived using the fate model EXWAT. Two ranking methods were used and results were compared. One method is based on the standardization of the data into attributes and aggregation into an index. The second method allows one to visually compare chemicals based on a large number of test results which might otherwise be very confusing when displayed in a table form: The Hasse diagram is an effective graphical display of data difficult to understand otherwise. Results by both ranking methods show that these chemicals can be divided into two groups, the most hazardous include Dinitroorthocresol, Propetamphos and Parathion, and the least hazardous include Disulfoton, Thiometon, Etrimphos, Metoxuron and Fenitrothion.     

Predicting Vertical LNAPL Distribution in the Subsurface under the Fluctuating Water Table Effect

The present study proposes a methodology for predicting the vertical light nonaqueous-phase liquids (LNAPLs) distribution within an aquifer by considering the influence of water table fluctuations. The LNAPL distribution is predicted by combining (1) information on air/LNAPL and LNAPL/water interface elevations with (2) the initial elevation of the water table without LNAPL effect. Data used in the present study were collected during groundwater monitoring undertaken over a period of 4 months at a LNAPL-impacted observation well. In this study, the water table fluctuations raised the free LNAPL in the subsurface to an elevation of 206.63 m, while the lowest elevation was 205.70 m, forming a thickness of 0.93 m of LNAPL-impacted soil. Results show that the apparent LNAPL thickness in the observation well is found to be three times greater than the actual free LNAPL thickness in soil; a finding that agrees with previous studies reporting that apparent LNAPL thickness in observation wells typically exceeds the free LNAPL thickness within soil by a factor estimated to range between 2 and 10. The present study provides insights concerning the transient variation of LNAPL distribution within the subsurface and highlights the capability of the proposed methodology to mathematically predict the actual LNAPL thickness in the subsurface, without the need to conduct laborious field tests. Practitioners can use the proposed methodology to determine by how much the water table should be lowered, through pumping, to isolate the LNAPL-impacted soil within the unsaturated zone, which can then be subjected to in situ vadose zone remedial treatment.     

Slug Tests in Wells Screened Across the Water Table: Some Additional Considerations

The majority of slug tests done at sites of shallow groundwater contamination are performed in wells screened across the water table and are affected by mechanisms beyond those considered in the standard slug‐test models. These additional mechanisms give rise to a number of practical issues that are yet to be fully resolved; four of these are addressed here. The wells in which slug tests are performed were rarely installed for that purpose, so the well design can result in problematic (small signal to noise ratio) test data. The suitability of a particular well design should thus always be assessed prior to field testing. In slug tests of short duration, it can be difficult to identify which portion of the test represents filter‐pack drainage and which represents formation response; application of a mass balance can help confirm that test phases have been correctly identified. A key parameter required for all slug test models is the casing radius. However, in this setting, the effective casing radius (borehole radius corrected for filter‐pack porosity), not the nominal well radius, is required; this effective radius is best estimated directly from test data. Finally, although conventional slug‐test models do not consider filter‐pack drainage, these models will yield reasonable hydraulic conductivity estimates when applied to the formation‐response phase of a test from an appropriately developed well.