Sediment trace metals and PCB input history in Lake Anna, Virginia, USA     

Ben K. Odhiambo  Virginia Brown  Gayle Armentrout  Leanna C. Giancarlo  Chelsea Wegner 《Environmental Earth Sciences》2013,69(6):2103-2117

Damming of the North Anna River in 1972 created Lake Anna, a cooling water source for the Dominion nuclear power plant as well as a popular recreation site in Spotsylvania and Orange counties, Virginia, USA. Previously dated (210-Pb) sediment cores from seven locations within the lake and three locations in the adjoining Waste Heat Treatment Facilities (WHTF) were analyzed for trace metals (Al, Ba, Zn, Cd, Cu, Fe, Mn and Pb) and polychlorinated biphenyls (PCBs) to examine the environmental evolution of the reservoir system. The reservoir has a history of mining activities in its watershed and unusually elevated concentrations of PCBs were found in fish tissues from previous studies. Therefore, dated sediment cores provided the framework for both the temporal and spatial analysis of possible sources and flux histories for both trace metals and PCBs. The trace metals results suggest that, though the upper reaches are relatively less impacted, the old mine tailings from the now ceased mining activities in the watershed of Contrary Creek tributary continue to dominate the sediment chemistry of the lower portion of the lake basin, signified by sediment enrichment of Pb, Cd, Cu, and Zn. Lagoon-2 of the WHTF also seems to be receiving unusually high loadings of Cd (12.5 ± 1.07 μg/g) that is probably associated with waste materials from the nuclear power plant that maintains the lagoons. PCB sediment concentrations were relatively low in the lower sections of the basins with values typically being <3.5 ng/g. The upper reaches of the basin had several PCB hotspots, with the surface sediments of Terry’s Run tributary having values as high as 53.13 ng/g. The spatial distribution of PCBs seems to suggest the upper reaches of the basin as the probable source, with the unusually high concentrations near bridges suggesting a possible link between the PCBs and old bridge fill materials. The oldest lacustrine sediments also had relatively high trace metals and PCB values signifying a probable role of soil disruption and sediment reconcentration during reservoir construction.  相似文献   

TIMBER HARVESTING AND THE HYDROLOGIC RESPONSE OF REDWOOD CREEK,CALIFORNIA     

Virginia L. Mahacek-King  M. L. Shelton 《自然地理学》2013,34(3):241-256

Timber removal on publicand private land surrounding Redwood National Park exacerbates naturally high rates of erosion that are common to this region and alters hydrologic processes within the park boundaries. These alterations of the natural environment complicate the efforts of the National Park Service to preserve a remnant of the once extensive coastal redwood ecosystem in the park. A watershed model for Redwood Creek calibrated to pre-logging conditions is employed to define and quantify changes in the hydrologic response of the basin during the years when timber harvesting reduced significantly the acreage of redwoods. Analysis of modeled and observed runoff indicates that timber removal is related to increased runoff during wet months and wet years, but runoff is reduced during dry months and dry years. These alterations in the hydrologic system occur at the least beneficial time because they augment high flows, whereas low flows are depleted. Such changes in runoff contribute to magnified erosion and deposition problems and increased stress for the flora and fauna that reside in and along Redwood Creek. [Key words: Redwood National Park, hydrology, watershed model, timber harvesting.]  相似文献   

Characterization of Persistent Volatile Contaminant Sources in the Vadose Zone     

Kenneth C. Carroll  Michael J. Truex  Mark L. Brusseau  Kyle R. Parker  Robert D. Mackley  Virginia J. Rohay 《Ground Water Monitoring & Remediation》2013,33(2):68-84

Effective long‐term operation of soil vapor extraction (SVE) systems for cleanup of vadose‐zone sources requires consideration of the likelihood that remediation activities over time will alter the subsurface distribution and configuration of contaminants. A method is demonstrated for locating and characterizing the distribution and nature of persistent volatile organic contaminant (VOC) sources in the vadose zone. The method consists of three components: analysis of existing site and SVE‐operations data, vapor‐phase cyclic contaminant mass‐discharge testing, and short‐term vapor‐phase contaminant mass‐discharge tests conducted in series at multiple locations. Results obtained from the method were used to characterize overall source zone mass‐transfer limitations, source‐strength reductions, potential changes in source‐zone architecture, and the spatial variability and extent of the persistent source(s) for the Department of Energy's Hanford site. The results confirmed a heterogeneous distribution of contaminant mass discharge throughout the vadose zone. Analyses of the mass‐discharge profiles indicate that the remaining contaminant source is coincident with a lower‐permeability unit at the site. Such measurements of source strength and size as obtained herein are needed to determine the impacts of vadose‐zone sources on groundwater contamination and vapor intrusion, and can support evaluation and optimization of the performance of SVE operations.  相似文献   

Geomorphic and stream flow influences on large wood dynamics and displacement lengths in high gradient mountain streams (Chile)          下载免费PDF全文

Andrés Iroumé  Virginia Ruiz‐Villanueva  Luca Mao  Guillermo Barrientos  Markus Stoffel  Gastón Vergara 《水文研究》2018,32(17):2636-2653

Understanding large wood (LW; ≥1 m long and ≥10 cm in diameter) dynamics in rivers is critical for many disciplines including those assessing flood hazard and risk. However, our understanding of wood entrainment and deposition is still limited, mainly because of the lack of long‐term monitoring of wood‐related processes. The dataset presented here was obtained from more than 8 years of monitoring of 1,264 tagged wood pieces placed in 4 low‐order streams of the Chilean mountain ranges and was used to further our understanding of key factors controlling LW dynamics. We show that LW displacement lengths were longer during periods when peak‐flow water depths (H_max) exceeded the bankfull stage (H_Bk) than in periods with H_max ≤ H_Bk and that these differences were significantly higher for smaller wood pieces. LW length and length relative to channel dimensions were the main factors governing LW entrainment; LW displacement lengths were inversely related to the ratio of piece length to H_15% (i.e., the level above which the flow remains for 15% of the time) and to the ratio of H_15% to bankfull width. Unrooted logs and LW pieces located at the bankfull stage travelled significantly longer distances than logs with attached rootwads and those located in other positions within the bankfull channel. A few large logjams were broken during the period of observation, and in all occasions, LW from these broken logjams did not travel over longer distances than other pieces of LW moved in the same periods and in the same stream segments. Most importantly, our work reveals that LW dynamics tend to be concentrated within a few reaches in each stream and that reaches exhibiting high wood dynamics (extensive entrainment, deposition, or repositioning of LW) are significantly wider and less steep than less dynamic reaches.  相似文献   

Floods at the northern foothills of the Tatra Mountains — A Polish-Swiss research project   总被引：1，自引：1，他引：0  

Zbigniew W. Kundzewicz  Markus Stoffel  Ryszard J. Kaczka  Bartłomiej Wyżga  Tadeusz Niedźwiedź  Iwona Pińskwar  Virginia Ruiz-Villanueva  Ewa Łupikasza  Barbara Czajka  Juan Antonio Ballesteros-Canovas  Łukasz Małarzewski  Adam Choryński  Karolina Janecka  Paweł Mikuś 《Acta Geophysica》2014,62(3):620-641

The present paper introduces the topical area of the Polish-Swiss research project FLORIST (Flood risk on the northern foothills of the Tatra Mountains), informs on its objectives, and reports on initial results. The Tatra Mountains are the area of the highest precipitation in Poland and largely contribute to flood generation. The project is focused around four competence clusters: observation-based climatology, model-based climate change projections and impact assessment, dendrogeomorphology, and impact of large wood debris on fluvial processes. The knowledge generated in the FLORIST project is likely to have impact on understanding and interpretation of flood risk on the northern foothills of the Tatra Mountains, in the past, present, and future. It can help solving important practical problems related to flood risk reduction strategies and flood preparedness.  相似文献   

Contributing Factors to Disease Outbreaks Associated with Untreated Groundwater   总被引：1，自引：0，他引：1  

Erika K. Wallender  Elizabeth C. Ailes  Jonathan S. Yoder  Virginia A. Roberts  Joan M. Brunkard 《Ground water》2014,52(6):886-897

Disease outbreaks associated with drinking water drawn from untreated groundwater sources represent a substantial proportion (30.3%) of the 818 drinking water outbreaks reported to CDC's Waterborne Disease and Outbreak Surveillance System (WBDOSS) during 1971 to 2008. The objectives of this study were to identify underlying contributing factors, suggest improvements for data collection during outbreaks, and inform outbreak prevention efforts. Two researchers independently reviewed all qualifying outbreak reports (1971 to 2008), assigned contributing factors and abstracted additional information (e.g., cases, etiology, and water system attributes). The 248 outbreaks resulted in at least 23,478 cases of illness, 390 hospitalizations, and 13 deaths. The majority of outbreaks had an unidentified etiology (n = 135, 54.4%). When identified, the primary etiologies were hepatitis A virus (n = 21, 8.5%), Shigella spp. (n = 20, 8.1%), and Giardia intestinalis (n = 14, 5.7%). Among the 172 (69.4%) outbreaks with contributing factor data available, the leading contamination sources included human sewage (n = 57, 33.1%), animal contamination (n = 16, 9.3%), and contamination entering via the distribution system (n = 12, 7.0%). Groundwater contamination was most often facilitated by improper design, maintenance or location of the water source or nearby waste water disposal system (i.e., septic tank; n = 116, 67.4%). Other contributing factors included rapid pathogen transport through hydrogeologic formations (e.g., karst limestone; n = 45, 26.2%) and preceding heavy rainfall or flooding (n = 36, 20.9%). This analysis underscores the importance of identifying untreated groundwater system vulnerabilities through frequent inspection and routine maintenance, as recommended by protective regulations such as Environmental Protection Agency's (EPA's) Groundwater Rule, and the need for special consideration of the local hydrogeology.  相似文献   

Urban development in the world dryland regions: Inventory and prospects     

Robert B. Potter  Virginia Potter 《Geoforum》1978,9(6):349-379

Interest in the social, technical and demographic problems involved in the development of the world's dryland regions has increased greatly in the recent past. This paper examines the location, size differentiation and growth of urban agglomerations with 100,000 or more inhabitants situated in the extremely arid, arid and and semi-arid regions. A total of 355 such major urban settlements are identified and their distribution and size characteristics are examined. Subsequently, the growth rates recorded by these urban areas in the period 1950–1970 are analyzed at the global, continental and national levels and according to city size. It is estimated that 26.1% of all dryland denizens reside in urban areas with populations of 100,000 or more. In conclusion, the future prospects and planning implications of such dryland urban agglomerations are discussed.  相似文献   

Reply to comments by C. Irwin-Williams: Archeological site, Valsequillo, Mexico     

Harold E. Malde  Virginia Steen-McIntyre 《Quaternary Research》1981,16(3):418-421

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9000 years of salmon fishing on the Columbia River, North America     

Virginia L Butler  Jim E O'Connor 《Quaternary Research》2004,62(1):1-8

A large assemblage of salmon bones excavated 50 yr ago from an ∼10,000-yr-old archaeological site near The Dalles, Oregon, USA, has been the primary evidence that early native people along the Columbia River subsisted on salmon. Recent debate about the human role in creating the deposit prompted excavation of additional deposits and analysis of archaeologic, geologic, and hydrologic conditions at the site. Results indicate an anthropogenic source for most of the salmonid remains, which have associated radiocarbon dates indicating that the site was occupied as long ago as 9300 cal yr B.P. The abundance of salmon bone indicates that salmon was a major food item and suggests that migratory salmonids had well-established spawning populations in some parts of the Columbia Basin by 9300-8200 yr ago.  相似文献   

Role of biological soil crust cover in bioweathering and protection of sandstones in a semi‐arid landscape (Torrollones de Gabarda,Huesca, Spain)     

Virginia Souza‐Egipsy  Jacek Wierzchos  Carlos Sancho  Anchel Belmonte  Carmen Ascaso 《地球表面变化过程与地形》2004,29(13):1651-1661

Sandstone structural landscapes in the semi‐arid Torrollones de Gabarda area (Province of Huesca, NE Spain) are often covered by a well developed biological soil crust of lichens, mosses and cyanobacteria and black coatings on vertical surfaces. By using scanning electron microscopy with backscattered detector imaging, the biological soil crust studied evidenced high activity in the sandstone–crust interface. Processes such as physical disintegration, etching and dwelling as well as biomineralization by calcium oxalate and ?xation of mineral particles by extracellular polymeric substances were observed. On the horizontal sandstone surfaces these processes may cause the occurrence of gnammas and the development of a protective coating that favours intense ?aking when the crust is disturbed. On the sandstone cliffs, columnar and tafoni weathering development is clearly guided by the protective action of the biological soil crust. These qualitative observations are important to develop methodologies to address their quantitative importance in geomorphological processes in semi‐arid landscapes. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献