Evaluation of acid-producing sulfidic materials in Virginia highway corridors     

Zenah?W.?OrndorffEmail author  W.?Lee Daniels 《Environmental Geology》2004,46(2):209-216

Road construction through sulfidic materials in Virginia has resulted in localized acid rock drainage (ARD) that threatens water quality, sedimentation, integrity of building materials, and vegetation management. Geologic formations associated with acid roadcuts were characterized by potential peroxide acidity (PPA), expressed as calcium carbonate equivalence (CCE), and total sulfur (total-S) in order to develop a statewide sulfide hazard rating map. The geologic formations were grouped into four categories based on potential acid-producing severity: i) Tabb formation (PPA<6 Mg CCE/1000 Mg; S<0.2%); ii) Ashe formation (PPA<18 Mg CCE/1000 Mg; S<2.0%); iii) Chesapeake Group, Lower Tertiary deposits, Millboro shale, Marcellus shale, and Needmore Formation (PPA<60 Mg CCE/1000 Mg; S<2.6%), and; iv) Chattanooga shale and Quantico slate (PPA<99 Mg CCE/1000 Mg; S<3.9%). Sulfide hazard analysis should be an essential step in the pre-design phase of highway construction and other earth-disturbing activities.  相似文献   

Endocrine disrupting alkylphenols and bisphenol-A in coastal waters and supermarket seafood from Singapore   总被引：2，自引：0，他引：2  

Basheer C  Lee HK  Tan KS 《Marine pollution bulletin》2004,48(11-12):1161-1167

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Pilot-scale field model tests for detecting landfill leachate intrusion into the subsurface using a grid-net electrical conductivity measurement system     

Myoung?Hak?Oh  Ju?Hyung?Lee  Gil?Lim?Yoon  Junboum?ParkEmail author 《Environmental Geology》2003,45(2):181-189

The grid-net electrical conductivity measurement system for detecting exact locations of landfill leachate intrusion in the subsurface was developed in this study. Laboratory and pilot-scale field model tests were performed to evaluate the direct application of a grid-net electrical conductivity measurement system for the detection of landfill leachate. A significant increase in electrical conductivity of soil was observed by adding landfill leachate. This can be explained as an increase in electrical conductivity of pore fluid due to an increase in leachate constituents as charge carriers. In pilot-scale field model tests, leachate intrusion locations were accurately identified at the initial stage of landfill leachate release by the grid-net electrical conductivity measurement system. The electrical conductivity of the subsurface before leachate injection lay within a small range of 24.8–43.0 S/cm. The electrical conductivity values in detected points were approximately ten times more than the conductivity values of the subsurface without landfill leachate intrusion. The results in this study indicate that the grid-net electrical conductivity measurement method has a possible application for detecting locations of landfill leachate intrusion into the subsurface at the initial stage, and thus has great potential in monitoring leachate leakage at waste landfills.  相似文献   

Use of an artificial neural network for analysis of the susceptibility to landslides at Boun,Korea   总被引：13，自引：0，他引：13  

Saro?LeeEmail author  Joo-Hyung?Ryu  Moung-Jin?Lee  Joong-Sun?Won 《Environmental Geology》2003,44(7):820-833

The purpose of this study was to develop landslide susceptibility analysis techniques using artificial neural networks and to apply the resulting techniques to the study area of Boun in Korea. Landslide locations were identified in the study area from interpretation of aerial photographs and field survey data. A spatial database of the topography, soil type, timber cover, geology, and land cover was constructed and the landslide-related factors were extracted from the spatial database. Using these factors, the susceptibility to landslides was analyzed by artificial neural network methods. The results of the landslide susceptibility maps were compared and verified using known landslide locations at another area, Yongin, in Korea. A Geographic Information System (GIS) was used to analyze efficiently the vast amount of data and an artificial neural network turned out to be an effective tool to analyze the landslide susceptibility.  相似文献   

Long-term change in eelgrass distribution at Bahía San Quintín,Baja California,Mexico, using satellite imagery     

David?H.?WardEmail author  Alexandra?Morton  T.?Lee?Tibbitts  David?C.?Douglas  Eduardo?Carrera-González 《Estuaries and Coasts》2003,26(6):1529-1539

Seagrasses are critically important components of many marine coastal and estuarine ecosystems, but are declining worldwide. Spatial change in distribution of eelgrass,Zostera marina L., was assessed at Bahía San Quintín, Baja California, Mexico, using a map to map comparison of data interpreted from a 1987 Satellite Pour l'Observation de la Terre multispectral satellite image and a 2000 Landsat Enhanced Thematic Mapping image. Eelgrass comprised 49% and 43% of the areal extent of the bay in 1987 and 2000, respectively. Spatial extent of eelgrass was 13% less (−321 ha) in 2000 than in 1987 with most losses occurring in subtidal areas. Over the 13-yr study period, there was a 34% loss of submerged eelgrass (−457 ha) and a 13% (+136 ha) gain of intertidal eelgrass. Within the two types of intertidal eelgrass, the patchy cover class (<85% cover) expanded (+250 ha) and continuous cover class (≥85% cover) declined (−114 ha). Most eelgrass losses were likely the result of sediment loading and turbidity caused by a single flooding event in winter of 1992–1993. Recent large-scale agricultural development of adjacent uplands may have exacerbated the effects of the flood. Oyster farming was not associated with any detectable losses in eelgrass spatial extent, despite the increase in number of oyster racks from 57 to 484 over the study period.  相似文献   

MODFLOW 2000 head uncertainty,a first-order second moment method   总被引：1，自引：0，他引：1  

Glasgow HS  Fortney MD  Lee J  Graettinger AJ  Reeves HW 《Ground water》2003,41(3):342-350

A computationally efficient method to estimate the variance and covariance in piezometric head results computed through MODFLOW 2000 using a first-order second moment (FOSM) approach is presented. This methodology employs a first-order Taylor series expansion to combine model sensitivity with uncertainty in geologic data. MODFLOW 2000 is used to calculate both the ground water head and the sensitivity of head to changes in input data. From a limited number of samples, geologic data are extrapolated and their associated uncertainties are computed through a conditional probability calculation. Combining the spatially related sensitivity and input uncertainty produces the variance-covariance matrix, the diagonal of which is used to yield the standard deviation in MODFLOW 2000 head. The variance in piezometric head can be used for calibrating the model, estimating confidence intervals, directing exploration, and evaluating the reliability of a design. A case study illustrates the approach, where aquifer transmissivity is the spatially related uncertain geologic input data. The FOSM methodology is shown to be applicable for calculating output uncertainty for (1) spatially related input and output data, and (2) multiple input parameters (transmissivity and recharge).  相似文献   

The 1786 earthquake-triggered landslide dam and subsequent dam-break flood on the Dadu River, southwestern China   总被引：17，自引：1，他引：17  

F.C. Dai  C.F. Lee  J.H. Deng  L.G. Tham 《Geomorphology》2005,65(3-4):205-221

Chinese historic documents recorded that on June 1, 1786, a strong M=7.75 earthquake occurred in the Kangding-Luding area, Sichuan, southwestern China, resulting in a large landslide that fell into the Dadu River. As a result, a landslide dam blocked the river. Ten days later, the sudden breaching of the dam resulted in catastrophic downstream flooding. Historic records document over 100,000 deaths by the flood. This may be the most disastrous event ever caused by landslide dam failures in the world. Although a lot of work has been carried out to determine the location, magnitude and intensity of the 1786 earthquake, relatively little is known about the occurrence and nature of the landslide dam. In this paper, the dam was reconstructed using historic documents and geomorphic evidence. It was found that the landslide dam was about 70 m high, and it created a lake with a water volume of about 50×10⁶ m³ and an area of about 1.7 km². The landslide dam breached suddenly due to a major aftershock on June 10, 1786. The peak discharge at the dam breach was estimated using regression equations and a physically based predictive equation. The possibility of a future failure of the landslide seems high, particularly due to inherent seismic risk, and detailed geotechnical investigations are strongly recommended for evaluating the current stability of the landslide.  相似文献   

Vector magnetic analysis within the southern Ayu Trough, equatorial western Pacific   总被引：2，自引：1，他引：2  

Sang-Mook Lee  Seung-Sep Kim 《Geophysical Journal International》2004,156(2):213-221

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Small-scale variations in seismic anisotropy near Kimberley, South Africa   总被引：1，自引：0，他引：1  

Matthew J. Fouch  Paul G. Silver  David R. Bell  Jean N. Lee 《Geophysical Journal International》2004,157(2):764-774

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How are storm time injections different from nonstorm time injections?     

D.-Y. Lee  J.A. Hwang  E.S. Lee  K.W. Min  W.Y. Han  U.W. Nam 《Journal of Atmospheric and Solar》2004,66(18):1715

One of the key elements of storms and substorms is the injection of energetic particles into the region of near geosynchronous orbit, that is, the sudden flux enhancement in the energy range of tens to hundreds of keV. This paper reports the observational results on how such injection features during storm times are different from those of nonstorm times. We particularly focus on the difference between proton injections and electron injections. Based on a number of storm time injection events that meet our strict selection criteria, we find a notable difference between proton injections and electron injections in the energy-spectral dependence of the flux enhancement averaged over the first 30 min after the injection onset: The average flux enhancement of many protons injections tends to be bigger at higher energy channels than at lower energy channels, but electron injections exhibit the opposite tendency for the energy-spectral dependence of flux enhancement, i.e., average flux enhancement decreasing with increasing energy. We show that this feature is almost unique only for the injection events during the storm main and early recovery phase. It is suggested that any successful scenario intended to model storm time injections should be able to explain this difference between proton injections and electron injections.  相似文献