Applications of particle-tracking techniques to bank infiltration: a case study from El Paso,Texas, USA     

Ahmad Abdel-Fattah  Richard Langford  Dirk Schulze-Makuch 《Environmental Geology》2008,55(3):505-515

This paper presents results of a small scale study that utilized particle-tracking techniques to evaluate transport of river water through an alluvial aquifer in a bank infiltration testing site in El Paso, Texas, USA. The particle-tracking survey was used to better define filtration parameters. Several simulations were generated to allow visualization of the effects of well placement and pumping rate on flow paths, travel time, the size of the pumping influence zone, and proportion of river-derived water and groundwater mixing in the pumping well. Simulations indicate that migration of river water into the aquifer is generally slow. Most water does not arrive at the well by the end of an 18-day pumping period at 0.54 m³/min pumping rate for a well located 18 m from the river. Forty-four percent of the water pumped from the well was river water. The models provided important information needed to design appropriate sampling schedules for bank filtration practices and ensured meeting adequate soil-retention times. The pumping rate has more effect on river water travel time than the location of the pumping well from the river. The examples presented in this paper indicate that operating the pumping well at a doubled distance from the river increased the time required for the water to travel to the well, but did not greatly change the capture zone.  相似文献   

Pop-up bottom seismic recorder (PUBS) of the Institute of Oceanographic Sciences,U.K.     

J. J. Langford  R. B. Whitmarsh 《Marine Geophysical Researches》1977,3(1):43-63

A pop-up bottom seismic recorder designed for seismic refraction experiments was built by the Institute of Oceanographic Sciences in 1968. The device is housed within a 71 cm diameter sphere weighing 270 kg when launched. signals picked up by a hydrophone are recorded in analogue form on magnetic tape in the band 2–100 Hz. The total continuous recording period is 12 hr but the lifetime of the system can be effectively extended by cycling the tape-recorders to allow shooting to go on for up to 3 days. Ballast release is by acoustic command or by pre-set clock. The instruments have been used in water depths from 150 to 4820 m making a total of 63 deployments with a 95% recovery rate. A new version with three-component geophones is being built.  相似文献   

Calibration of an oscillating nozzle‐type rainfall simulator     

Bofu Yu  Cyril A. A. Ciesiolka  Paul Langford 《地球表面变化过程与地形》2003,28(13):1483-1490

Nozzle‐type rainfall simulators are commonly used in hydrologic and soil erosion research. Simulated rainfall intensity, originating from the nozzle, increases as the distance between the point of measurement and the source is decreased. Hence, rainfall measured using rain gauges would systematically overestimate the rainfall received at the ground level. A simple model was developed to adjust rainfall measured anywhere under the simulator to plot‐wide average rainfall at the ground level. Nozzle height, plot width, gauge diameter and height, and gauge location are required to compute this adjustment factor. Results from 15 runs at different rain intensities and durations, and with different rain gauge layouts, showed that a simple average of measured rain would overestimate the plot‐wide rain by about 20 per cent. Using the adjustment factor to convert measured rainfall for individual gauges before averaging improved the estimate of plot‐wide rainfall considerably. For the 15 runs considered, overall discrepancy between actual and measured rain is reduced to less than 1 per cent with a standard error of 0·97 mm. This model can be easily tested in the ?eld by comparing rainfall depths of different sized gauges. With the adjustment factor they should all give very similar values. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

Eco-friendly smart hydrogels for soil conditioning and sustain release fertilizer     

J. Pushpamalar  S. J. Langford  M. B. Ahmad  Y. Y. Lim  K. Hashim 《International Journal of Environmental Science and Technology》2018,15(10):2059-2074

In the agricultural industry, biomass waste generated along with the production of food, is transformed into value-added products. Also, the demand for the slow or control release fertilizer is increasing to reduce the cost of maintaining the agricultural land. These issues are tackled by converting biomass waste to a slow fertilizer release vehicle and biodegradable water retention material that could reduce the cost for fertilizer application and simultaneously preserved the soil from dryness. A series of carboxymethyl sago pulp (CMSP) hydrogels were prepared by electron beam irradiation. Slow release systems were evaluated by loading potassium nitrate (KNO₃) and ammonium nitrate (NH₄NO₃) into the CMSP hydrogels. These CMSP hydrogels endow slow release property, biodegradability and a soil moisture preservation property that could find greener application in agricultural industries. The results indicate that CMSP hydrogels have a great potential as an agent for slow release of fertilizers.  相似文献   

Fracture induced emission of alkali atoms from feldspar     

J. T. Dickinson  L. C. Jensen  S. C. Langford  P. E. Rosenberg 《Physics and Chemistry of Minerals》1992,18(7):453-459

Emission of neutral atoms (K and Na) and molecules (H₂O and KOH) observed during fracture of K-feldspar have been accounted for by two independent mechanisms. H₂O and KOH emissions are attributed to the venting of fluid-filled inclusions, while emission of atomic K is due to surface effects accompanying cleavage of crystalline feldspar. The intensity of emitted potassium, at least 6 × 10¹⁴ atoms/cm² of surface area, is sufficient to affect K activities in solution during microbrecciation in the presence of rock-dominated fluids.  相似文献   

Age-estimate evidence for Middle-Late Pleistocene aggradation of River Nene 1st Terrace deposits at Whittlesey, eastern England     

H.E. Langford  K.E.H. Penkman  R.M. Briant  D.H. Keen 《Proceedings of the Geologists' Association. Geologists' Association》2007,118(3):283-300

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Northern Ireland lignite     

C. W. Jeffersen Dr.  N. C. Mitchel 《GeoJournal》1991,24(4):405-412

Conclusion There is no doubt that Northern Ireland's lignite deposits are of high quality and constitute a natural resource of considerable potential value in this small, peripheral part of the European Community. Whether or not one or more will be used commercially and, if so, when depends on an interacting complex of economic, social and political factors. In purely economic terms, use will be effectively determined by lignite's economic competitiveness as a fuel dor electricity generation and on the relationship between capital and fuel costs. The economics of other possibly viable products such as lignite briquettes will be heavily dependent on the use of by-products of electricity generation, most notably surplus heat.The availability of lignite offers an alternative fuel option to those charged with formulating the Province's energy policy. If, as now seems likely, it is no longer a serious competitor for the power station planned for the mid-1990's, it most certainly is a competitor for the early part of the next century. This is particularly so in view of its low sulphur content which is about half that of Scottish coal on an energy equivalent basis. Lignite also offers security of supply at predictable prices, an important advantage, and thus carries a premium over coal, oil and natural gas which are imported at prices determined wholly exogenously.As the Province has by far the highest rate of regional unemployment in the United Kingdom, one argument advanced for the use of indigenous lignite is that its use in electricity generation would create much needed additional employment — an estimated 400 jobs being associated with the mining operations needed to support a 450 MW power station. But the Coagh example shows that other considerations must be taken seriously. It is extremely unlikely that the lignite in this area will ever be worked unless local attitudes change dramatically or there is some national fuel crisis which would over-ride local opposition. It is difficult enough developing lignite without having to contend with such strong resistance at the local level.This study has shown that certainly in the Northern Irish context it is highly important for the policy makers not only to consider the economic factors involved in choice of an energy fuel but to work closely with local communities and the various environmental bodies, to take their perceptions, right or wrong, into consideration.  相似文献   

Safety Measures after the 2011 Joplin,Missouri, Tornado          下载免费PDF全文

Bimal Kanti Paul  Mitchel Stimers 《Geographical review》2015,105(2):199-215

Immediately following the May 2011 tornado, the city of Joplin, Missouri, initiated recovery efforts to rebuild the part of the community devastated by this event. In doing so, city officials introduced two new safety measures and recommended several others. The main objective of this paper is to explore the tornado survivors' compliance with the safety features recommended by the Joplin city authorities. Face‐to‐face interviews, as well as other methods, were used to survey respondents who were living within the tornado path (damage zones) at the time of the tornado. Results showed that 43 percent of all respondents implemented at least one recommended tornado measure in rebuild or repair their destroyed/damaged homes. Further, it was found that three variables considered here— rebuild or repair, damage zone category, and perceived tornado risk—were all significant contributors to a homeowner's decision to implement recommended tornado safety measures. The paper concludes with a recommendation for expanding tornado safety education among the respondents.  相似文献   

Book reviews     

Schliephake  Konrad  Mitchel  N. C.  Stadel  Christoph  Hoffmann  Christoph  Kaminske  Volker  Schlichtmann  Hansgeorg  Leinbach  Thomas R. 《GeoJournal》1986,13(3):294-296

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A search for the oceanic Lg phase     

L. Knopoff  R. G. Mitchel  E. G. Kausel †  F. Schwab ‡ 《Geophysical Journal International》1979,56(1):211-218

Summary. The Lg phase has been shown previously to be a collection of higher-mode surface waves guided by the continental crust (Knopoff, Schwab & Kausel). A simple scaling between continental and oceanic crustal thicknesses suggests that a search for an oceanic Lg phase should be made in the period range from 1 to 2s. In a search for SH polarized Lg arrivals over oceanic paths, we found that in addition to the fundamental mode, seismo-grams at relatively short ranges in the Pacific showed the presence of only the first higher mode with group velocities on the steep portion of the dispersion curve rather than at the group velocity minimum as expected. Numerical model analysis indicates that, contrary to the continental case, there is no strong confluence of stationary phases of higher-mode crustal waves in the appropriate period range to produce Lg wave packets; this is due to small but significant differences in scaled crustal structures. Further, lateral variations in the thickness of oceanic sediments are sufficient to scatter most of the crustal surface-wave energy within a relatively short distance. Even were this thickness uniform, attenuation in the sediments would be strong enough to absorb the Lg stationary phases in a short distance.  相似文献