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排序方式: 共有115条查询结果,搜索用时 15 毫秒
1.
Mario Schirmer Frido Reinstorf Sebastian Leschik Andreas Musolff Ronald Krieg Gerhard Strauch John W. Molson Marion Martienssen Kristin Schirmer 《Environmental Earth Sciences》2011,64(3):607-617
Urban areas are the focus of major ecological, social and economical activity. They are thus also prime locations of increasing conflict with regard to water use and water protection. As a direct and/or indirect consequence of urban land use and human activity, urban water systems are frequently polluted with organic contaminants including waste water-born xenobiotics such as pharmaceuticals, personal care products (collectively known as PPCPs) and endocrine-active substances. This study reviews new integrated methodologies including flux calculations as well as chemical investigations for determining the impact of human activities on urban water systems and on processes within the urban watershed. The use of indicator substances, representing different contaminant sources and pathways, integral pumping tests and mass balance approaches are suitable alternatives within these environments. The issues are explored using contaminant mass balance examples from Halle/Saale and Leipzig, Germany. 相似文献
2.
Juan Pablo Corella Adel El Amrani Javier Sigró Mario Morellón Eugenio Rico Blas Lorenzo Valero-Garcés 《Journal of Paleolimnology》2011,46(3):469-485
We present a high-resolution, multiproxy reconstruction of the depositional history of Lake Arreo, northern Spain, for the
last 60 years. We conducted sedimentological, geochemical and diatom analyses in short cores and made a detailed comparison
with regional instrumental climate data (1952–2007), limnological monitoring of the lake (1992–2008) and recent land use changes
that affect the lake catchment. Chronology is based on “floating” discontinuous varve counts and 137Cs and 14C dates. Four periods were identified in the Lake Arreo recent history: (1) prior to 1963, varved facies intercalated with
fine turbidite deposits, and diatom assemblages dominated by Cyclotella taxa indicate predominantly meromictic conditions, (2) from 1964 to 1978, permanent anoxia persisted in bottom waters, as shown
by similar facies and diatom assemblages as before, though detrital layers were coarser, (3) from 1979 to 1994, sediment delivery
to the lake increased and laminated, clastic facies were deposited, and (4) from 1995 to 2008, dominance of massive facies
and an increase in Fragilaria tenera and Achnanthes minutissima reflect relatively lower lake levels, less frequent bottom anoxia with more frequent water column mixing, similar to modern
conditions. The period 1952–1979 was a time of meromixis and varved facies deposition, and was characterized by higher rainfall
and less intense agricultural pressure in the watershed. There were two short humid periods (1992–1993 and 1996–1998) when
monitoring data show more anoxic weeks per year and relatively higher lake levels. Increased cultivation of small landholdings
in 1963, and particularly after 1979, caused a large increase in sediment delivery to the lake. The inferred lake evolution
is in agreement with monitoring data that suggest a transition from dominantly meromictic conditions prior to 1993–1994 to
a predominantly monomictic pattern of circulation since then, particularly after 2000. The synergistic effects of intensive
water extraction for irrigation and lower rainfall since 1979, and particularly since 1994, brought the long period of meromictic
conditions in Lake Arreo to an end. Water balance and sediment delivery to the lake are dominant factors that control the
limnological and mixing conditions in Lake Arreo and they must be considered in management and restoration plans. 相似文献
3.
Bjorn A. Lake Courtney R. Wigdahl Kristin E. Strock Jasmine E. Saros Aria Amirbahman 《Journal of Paleolimnology》2011,46(1):45-57
The frequency of nuisance algal blooms has been increasing during the last two decades in the shallow, headwater East Pond
(Smithfield, Maine, USA). Meanwhile, the hydrologically linked North Pond has not experienced an increase in algal blooms,
despite similar morphometry and higher external nutrient loads. Possible explanations for this difference include stronger
trophic cascade effects from planktivorous white perch (Morone americana) in East Pond as well as differences in phosphorus (P) release from the sediments of these two lakes. We conducted a paleolimnological
investigation of these two lakes to assess whether sedimentary evidence supported trophic cascade effects based on cladoceran
ephippia size, diatom fossils, and fossil pigments or biogeochemical controls based on potential sedimentary P release as
the primary driver of these increased algal blooms in East Pond. At the time of white perch introduction (~1930–1950), ephippia
size increases in East Pond, although no changes are observed in either diatom abundance or trends in the algal pigments.
Instead, algal pigments increase in recent decades (~1980 to present) along with an increase in diatom taxa with higher TP
optima These results suggest that predation by white perch is not resulting in top-down effects on algal abundance in East
Pond, as predicted by the trophic cascade hypothesis. While the P content of sediments from both lakes is relatively equal,
the releasable P in the top 10 cm of sediment in East Pond constitutes a greater percentage of the P extracted. Also, North
Pond sediments exhibit a greater capacity to permanently bury P via the mechanisms of sorption to Al(OH)3(s) and a slower mineralization of organic P compounds. The results of this investigation suggest that the ultimate driver of
the recent algal blooms in East Pond is internal P release from the sediments instead of trophic cascade effects. 相似文献
4.
Ana Moreno Blas L. Valero‐Garcés Montserrat Jiménez‐Sánchez María José Domínguez‐Cuesta M. Pilar Mata Ana Navas Penélope González‐Sampériz Heather Stoll Pedro Farias Mario Morellón J. Pablo Corella Mayte Rico 《第四纪科学杂志》2010,25(7):1076-1091
A sedimentological and geochemical study of the Lago Enol sequence (Cantabrian Mountains, northern Spain), together with detailed geomorphological mapping, provides a first record of glacier evolution and climate change over the last 40 ka in the Picos de Europa National Park. The Enol glacier retreated from its maximum extent prior to 40 ka BP as demonstrated by the onset of proglacial lacustrine sedimentation in two glaciated depressions: the Comella hollow to the north (before 40 ka BP) and the Lago Enol (before 38 ka BP). These results support previous evidence that the maximum extent of southern European glaciers occurred earlier than in northern Europe. Alternation of homogeneous and laminated proglacial sediments during the glacier retreat illustrate a dynamic glacial evolution during the Marine Isotope Stage (MIS) 3 (40–26 ka BP). A slight warming is detected at 26 ka ago with the change from proglacial sediments (in a lake located in contact to the glacier) to glaciolacustrine sedimentation (in a non‐contact or distal lake). Finally, the onset of organic‐rich sediments took place at 18 ka ago. This last transition occurred in two phases, similarly to the North Atlantic Last Termination, suggesting a link between North Atlantic Deep Water formation oscillations and palaeohydrological variability in the Cantabrian Mountains. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
5.
Anne-Kari Furre Mona Andersen Anita Smalø Moen Randi Kristin Tønnessen 《Geophysical Prospecting》2009,57(3):427-437
We have developed a method to determine the effect of pore pressure depletion on elastic framework moduli, by utilizing sonic logs from wells drilled at different locations through a reservoir at varying depletion stages. This is done by first inverting the sonic logs for elastic framework bulk and shear moduli, thus carefully removing pressure dependent fluid effects. By crossplotting these elastic framework moduli against an increase in net stress (which is directly related to depletion), we derive the stress sensitivity of the elastic framework moduli. We found that the observed stress sensitivity was consistent with time-lapse seismic results and that the sensitivity derived from the sonic logs was much smaller than predicted by hydrostatic measurements on core samples. This method is applicable to depletion scenarios in mature fields and can be used both for modelling and inverting time-lapse seismic data for effects of pore pressure depletion on seismic data. 相似文献
6.
Trevor I. Allen David J. Wald Paul S. Earle Kristin D. Marano Alicia J. Hotovec Kuowan Lin Michael G. Hearne 《Bulletin of Earthquake Engineering》2009,7(3):701-718
We present an Atlas of ShakeMaps and a catalog of human population exposures to moderate-to-strong ground shaking (EXPO-CAT)
for recent historical earthquakes (1973–2007). The common purpose of the Atlas and exposure catalog is to calibrate earthquake
loss models to be used in the US Geological Survey’s Prompt Assessment of Global Earthquakes for Response (PAGER). The full
ShakeMap Atlas currently comprises over 5,600 earthquakes from January 1973 through December 2007, with almost 500 of these
maps constrained—to varying degrees—by instrumental ground motions, macroseismic intensity data, community internet intensity
observations, and published earthquake rupture models. The catalog of human exposures is derived using current PAGER methodologies.
Exposure to discrete levels of shaking intensity is obtained by correlating Atlas ShakeMaps with a global population database.
Combining this population exposure dataset with historical earthquake loss data, such as PAGER-CAT, provides a useful resource
for calibrating loss methodologies against a systematically-derived set of ShakeMap hazard outputs. We illustrate two example
uses for EXPO-CAT; (1) simple objective ranking of country vulnerability to earthquakes, and; (2) the influence of time-of-day
on earthquake mortality. In general, we observe that countries in similar geographic regions with similar construction practices
tend to cluster spatially in terms of relative vulnerability. We also find little quantitative evidence to suggest that time-of-day
is a significant factor in earthquake mortality. Moreover, earthquake mortality appears to be more systematically linked to
the population exposed to severe ground shaking (Modified Mercalli Intensity VIII+). Finally, equipped with the full Atlas
of ShakeMaps, we merge each of these maps and find the maximum estimated peak ground acceleration at any grid point in the
world for the past 35 years. We subsequently compare this “composite ShakeMap” with existing global hazard models, calculating
the spatial area of the existing hazard maps exceeded by the combined ShakeMap ground motions. In general, these analyses
suggest that existing global, and regional, hazard maps tend to overestimate hazard. Both the Atlas of ShakeMaps and EXPO-CAT
have many potential uses for examining earthquake risk and epidemiology. All of the datasets discussed herein are available
for download on the PAGER Web page ().
T. I. Allen and M. G. Hearne—contracted through Synergetics Incorporated. 相似文献
7.
Four small freshwater river systems in Hessen, Germany, have been investigated with respect to seasonal and spatial concentration variations and transported load of the organophosphates tri‐n‐butyl phosphate (TBP), tris(2‐butoxyethyl)phosphate (TBEP), tris(2‐chloroethyl)phosphate (TCEP), tris(1‐chloro‐2‐propyl)phosphate (TCPP), and tris(1,3‐dichloro‐2‐propyl)phosphate (TDCPP) and the synthetic musk fragrances 1,3,4,6,7,8‐hexahydro‐4,6,6,7,8,8‐hexa‐methylcyclopenta‐[γ]‐2‐benzopyran (HHCB) and 7‐acetyl‐1,1,3,4,4,6‐hexamethyl‐1,2,3,4‐tetrahydronaphthalene (AHTN). Data originate from water samples collected in the time span from September 2003 to April 2005 at 25 sampling locations. The detection frequency for all compounds was about 90%. Mean concentration levels of organophosphates were 502 ng/L (TCPP), 276 ng/L (TBP), 183 ng/L (TBEP), 118 ng/L (TCEP), and 117 ng/L (TDCPP). The synthetic musk fragrances HHCB and ATHN were detected with mean concentrations of 141 and 46 ng/L, respectively. The variability of the concentration of all compounds was high with respect to space and time. The highest concentrations were observed in the Schwarzbach system characterized by the highest proportion of wastewater compared to the other river systems. Concentration levels of synthetic musk fragrances were significantly lower in summer times compared to winter times. 相似文献
8.
D. Heath Jones Will Saunders Matthew Colless Mike A. Read Quentin A. Parker Fred G. Watson Lachlan A. Campbell Daniel Burkey Thomas Mauch Lesa Moore Malcolm Hartley Paul Cass Dionne James Ken Russell Kristin Fiegert John Dawe John Huchra Tom Jarrett Ofer Lahav John Lucey Gary A. Mamon Dominique Proust Elaine M. Sadler Ken-ichi Wakamatsu 《Monthly notices of the Royal Astronomical Society》2004,355(3):747-763
9.
Multilayer coatings for reflecting hard X-rays up to 80 keV, like W/Si and Pt/C, have been studied for several years. To go to higher energies, in the range of 100 keV to 250 keV, one needs coatings with smaller d-spacings than can currently be made with these material combinations, and a lower interfacial roughness. With the new material combinations of WC/SiC the interface roughness can be reduced down to between 0.23 nm and 0.25 nm enabling bi-layer thicknesses down to 1.0 nm to reflect efficiently. The production of thinner period coatings thus enables the possibility for focusing optic designs with reasonable focal lengths and throughput up to 250 keV. 相似文献
10.
Contributions of boron isotopes to understanding the hydrogeochemistry of the coastal detritic aquifer of Castellón Plain,Spain 总被引:1,自引:0,他引:1
The Castellón Plain alluvial aquifer, Spain, is intensively exploited to meet the demand for agricultural irrigation and industrial water supply. The geochemistry of its groundwater shows complex salinization in the northern and southern parts of the aquifer, with significant pollution from human origin in the central portion. Boron content and B isotope geochemistry are useful for distinguishing between various sources of pollution and their relative importance in different parts of this aquifer. Boron concentrations in the groundwater vary between 0.01 and 0.85 mg/L. In the more saline groundwaters, found at the northern and southern ends of the study area, the presence of B is linked to inputs from seawater and water with a calcium-magnesium sulphate facies, which feed the aquifer and clearly influence the chemistry of its waters. Evidence of B adsorption processes in some samples is shown by the low B/Cl ratios and the high values of δ11B. In the central portion of the aquifer, the high B/Cl ratios and the strongly negative δ11B are related to pollution of human origin. 相似文献