Fracture flow and groundwater compartmentalization in the Rollins Sandstone, Lower Mesaverde Group, Colorado, USA     

Alan L. Mayo  Wendell Koontz 《Hydrogeology Journal》2000,8(4):430-446

 This paper presents a site-specific conceptual model of groundwater flow in fractured damage zones associated with faulting in a package of sedimentary rocks. The model is based on the results of field and laboratory investigations. Groundwater and methane gas inflows from fault-fracture systems in the West Elk coal mine, Colorado, USA, have occurred with increasing severity. Inflows of 6, 160 and 500 L s⁻¹ discharged almost instantaneously from three separate faults encountered in mine workings about 460 m below ground level. The faults are about 600 m apart. The δ ²H and δ ¹⁸O compositions of the fault-related inflow waters and the hydrodynamic responses of each fault inflow indicate that the groundwaters discharge from hydraulically isolated systems. ¹⁴C data indicate that the groundwaters are as much as 10,500 years old. Discharge temperatures are geothermal (≈30°C), which could indicate upwelling from depth. However, calculations of geothermal gradients, analysis of solute compositions of groundwater in potential host reservoirs, geothermometer calculations, and results of packer testing indicate that the fractured groundwater reservoir is the Rollins Sandstone (120 m thick) directly beneath the coal seams. The packer test also demonstrates that the methane gas is contained in the coal seams. A geothermal gradient of 70–80°C km⁻¹, related to an underlying intrusion, is probably responsible for the slightly elevated discharge temperatures. Large discharge volumes, as great as 8.2×10⁵m³ from the 14 South East Headgate fault (14 SEHG), rapid declines in discharge rates, and vertical and horizontal permeability (matrix permeability generally <0.006 Darcy) indicate fracture flow. An in-mine pumping test demonstrates that the 14 SEHG fault has excellent hydraulic communication with fractures 50 m from the fault. Aeromagnetic data indicate that the faults are tectonically related to an igneous body that is several thousand meters below the coal seams. Exploratory drilling has confirmed a fourth fault, and two additional faults are projected, based on the aeromagnetic data. The conceptual model describes a series of parallel, hydraulically separate groundwater systems associated with fault-specific damage zones. The faults are about 600 m apart. Groundwater stored in fractured sandstone is confined above and below by clayey layers. Received March 1999 / Revised, November 1999 / Accepted, December 1999  相似文献   

Comment on “Sulfate transport in a Coastal Plain confining unit,New Jersey,USA” (Pucci 1999)     

Javier Rodríguez 《Hydrogeology Journal》2000,8(4):447-450

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Mechanisms of pore water organic matter adsorption to montmorillonite   总被引：2，自引：0，他引：2  

Thorarinn S. Arnarson  Richard G. Keil 《Marine Chemistry》2000,71(3-4)

The extent and mechanisms of adsorption of marine pore water organic matter to montmorillonite were studied in a series of batch and sequential adsorption experiments. Pore water natural organic matter (pNOM) and easily extracted natural organic matter (eNOM) were collected from Liberty Bay (Puget Sound, WA, USA) sediments. The pNOM and eNOM were each divided into two size fractions using a 1000 D ultrafilter. Batch adsorption isotherms were approximately linear, and the >1000 D fractions of both pNOM and eNOM had larger partition coefficients (K_d) than the <1000 D fractions. A two-component fit of the sequential adsorption data indicated that pNOM and eNOM contained a similar amount of NOM (30%) that was not surface reactive toward montmorillonite. After correcting the batch adsorption K_ds for the non-reactive components, the K_ds estimated by batch and sequential adsorption were identical (2.7 l/kg for >1000 D pNOM and eNOM, and 1.6 l/kg for <1000 D pNOM and eNOM). Mechanisms of adsorption were investigated by systematically changing conditions (pH, temperature and ionic composition) of >1000 D fractions during batch isotherm experiments. Adsorption of NOM was found to decrease with increased temperature, suggesting that hydrophobic effects were not the dominant adsorption mechanisms in this system. Ion exchange was also not an important adsorption mechanism because adsorption increased with ionic strength. The observed enhancement in adsorption with ionic strength indicated that van der Waals interactions were important in the adsorption of NOM. Ligand exchange was found to be a significant mechanism since the presence of SO₄²⁻ in solution reduced the amount of NOM adsorbed. Ca²⁺ enhanced adsorption slightly more than Na⁺, suggesting that cation bridging was involved. The relative contributions of van der Waals interactions, ligand exchange and cation bridging were estimated to be approximately 60%, 35% and 5%, respectively, for adsorption of NOM in a CaCl₂ solution.  相似文献   

The appearance of Ulva laetevirens (Ulvophyceae,Chlorophyta) in the northeast coast of the United States of America     

Yunxiang Mao  Jang Kyun Kim  Roderick Wilson  Charles Yarish 《中国海洋大学学报(英文版)》2014,13(5):865-870

Introduced species may outcompete or hybridize with native species, resulting in the loss of native biodiversity or even alteration of ecosystem processes. In this study, we reported an alien distromatic Ulva species, which was found in an embayment (Holly Pond) connected with Long Island Sound, USA. The morphological and anatomical observations in combination with molecular data were used for its identification to species. Anatomy of collected specimens showed that the cell shape in rhizoidal and basal regions was round and the marginal teeth along the basal and median region were not found. These characteristics were primarily identical to the diagnostic characteristics of Ulva laetevirens Areschoug (Chlorophyta). The plastid-encoding tufA and nucleusencoding ITS1 were used for its molecular identification. Phylogenetic analysis for the tufA gene placed the specimens from Holly Pond in a well-supported clade along with published sequences of U. laetevirens identified early without any sequence divergence. In ITS tree, the sample also formed well-supported clades with the sequences of U. laetevirens with an estimated sequence divergence among the taxa in these clades as low as 1%. These findings confirmed the morpho-anatomical conclusion. Native to Australia, this species was reported in several countries along the Mediterranean coast after the late of 1990s. This is the first time that U. laetevirens is found in the northeast coast of United States and the second record for Atlantic North America.  相似文献   

The Retention,Revival, and Subjugation of Indigenous Fire Knowledge through Agency Fire Fighting in Eastern Australia and California     

Christine Eriksen  Don L. Hankins 《社会与自然资源》2014,27(12):1288-1303

This article explores the potential impact of training and employment with wildfire management agencies on the retention of Indigenous fire knowledge. It focuses on the comparative knowledge and experiences of Indigenous Elders, cultural practitioners, and land stewards in connection with “modern” political constructs of fire in New South Wales and Queensland, Australia, and California in the United States of America. This article emphasises the close link between cross-cultural acceptance, integration of Indigenous and agency fire cultures, and the ways in which knowledge types are shared or withheld. While agency fire fighting provides an opportunity for Indigenous people to connect and care for country, it simultaneously allows for the breaking of traditional rules surrounding what knowledge is shared with whom in the context of Indigenous cultural burning. By highlighting how privilege intersects with ethnicity, class, gender and age, this article demonstrates how greater cross-cultural acceptance could aid ongoing debates on how to coexist with wildfire today.  相似文献   

Repeated century-scale droughts over the past 13,000 yr near the Hudson River watershed, USA     

Paige E. Newby  Bryan N. Shuman  Jeffrey P. Donnelly  Dana MacDonald 《Quaternary Research》2011,75(3):523-530

Long-term sediment and ground-penetrating radar data from Davis Pond, a small lake near the Hudson River valley, reveal past droughts in a historically humid region that presently supplies water to millions of people in and around New York City. A minimum of eleven sandy paleoshoreline deposits in the lake date from 13.4 to 0.6 cal ka BP. The deposits span 1500 to 200 yr between bracketing radiocarbon ages, and intrude into lacustrine silts up to 9.0 m below the modern lake surface in a transect of six sediment cores. Three low stands, ca. 13.4–10.9, 9.2 and 8.2 cal ka BP indicate low regional moisture balance when low temperatures affected the North Atlantic region. Consistent with insolation trends, water levels rose from ca. 8.0 cal ka BP to present, but five low stands interrupted the rise and are likely associated with ocean–atmosphere interactions. Similar to evidence from other studies, the data from Davis Pond indicate repeated multi-century periods of prolonged or frequent droughts super-imposed on long-term regional trends toward high water levels. The patterns indicate that water supplies in this heavily populated region have continuously varied at multiple time scales and confirm that humid regions such as the northeastern United States are more prone to severe drought than historically expected.  相似文献   

Attenuation of multiphase surface waves in the Basin and Range Province—III. Inversion for crustal anelasticity     

Brian J. Mitchell  Jia-kang Xie 《Geophysical Journal International》1994,116(2):468-484

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Distribution and composition of phytoplankton in northeastern coastal waters of the United States     

Harold G. Marshall  Myra S. Cohn 《Estuarine, Coastal and Shelf Science》1983,17(2):119-131

Results are given from collections made during eight cruises over the northeastern continental shelf. Seasonal phytoplankton assemblages are noted, which include a variety of ultraplankton components. Areas of greatest cell concentrations were at near shore stations, Georges Bank, and at scattered sites over the shelf. Dominant species included Skeletonema costatum, Asterionella glacialis and Leptocylindrus danicus.  相似文献   

Dripping into unsaturated rock underground excavations: model testing at the Yucca Mountain exploratory studies facility     

Amvrossios?C.?BagtzoglouEmail author  Daniele?Cesano 《Environmental Geology》2007,51(8):1295-1306

This paper presents a probabilistic formulation of unsaturated flow through rough multi-segmented fractures, with emphasis on Dripping Initiation Time (DIT), and attempts to explain the fast flow paths detected at the Yucca Mountain (YM) Exploratory Studies Facility (ESF). Three scenarios of parameters were used to test the validity of the model with these fast flow paths. The scenarios differed in the DITs and the corresponding parameter configurations were also tested for three different stratigraphic horizon depths. Each depth represented a different location where fast flow has been detected at YM. The first depth corresponds to the Bow Ridge Fault; the second represents a network of steep fractures and cooling joints with large variability in dip; and the third location, probably connected to the Diabolous Ridge Fault, has a flow path that is low dipping. Monte Carlo simulations for each configuration and depth produced probabilistic results from nine scenarios for DITs, which are quite consistent with field observations.  相似文献   

Manual construction of continuous cartograms through mesh transformation     

Barry J. Kronenfeld 《制图学和地理信息科学》2018,45(1):76-94

A computer-assisted framework is proposed to support the manual construction of cartograms. The framework employs a joint triangulation, similar to that used in rubber-sheeting, to define a piecewise affine transformation between map space and cartogram space. This guarantees preservation of all topological relations within and among transformed datasets with insertion of a finite number of points. To support intuitive user control of cartogram appearance, methods are developed to translate generically defined user adjustments of the cartogram into mesh vertex positions on either the source map mesh or cartogram mesh. The framework is implemented in a working prototype application and used to create sample cartograms of the USA and China. Results are compared with cartograms produced using diffusion and carto3f algorithms in terms of accuracy, aesthetic appearance, and approximate construction time. Qualitative aspects of the manual construction process are also discussed.  相似文献