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41.
John M. Kennish Colleen Montoya Jane Whitsett John S. French 《Marine environmental research》1985,17(2-4)
Hydrocarbons are being introduced into the marine environment from a variety of sources including combustion processes, crude oil spills, fuel oil spills, and controlled disposal such as processed ballast water. Even in the relatively clean waters of Alaska hydrocarbons are being released at an alarming rate. The purpose of this study was to determine the optimum conditions for the metabolism of a representative hydrocarbon by Coho Salmon Oncorhynchus kisutch liver microsomes. The product of cyclohexane metabolism in the salmon microsomal system was identified by gas chromatography-mass spectrometry as cyclohexanol. Conditions of the microsome incubation were varied systematically to determine the optimum temperature, pH, and ionic strength for cyclohexanol production. Cyclohexanol was quantified by capillary column gas chromatography. Maximum cyclohexanol formation was achieved at 20°C, a pH of 8·0–8·5 and an ionic strength of 0·026. A linear rate of cyclohexanol formation is seen from 0–60 min of incubation and there is an apparent decrease in the rate from 60–90 min. Poor stability of the microsomal preparation from the species studied was also identified and several stability studies have been undertaken using cyclohexane metabolism as a monitor. 相似文献
42.
Jane?M.?HammarstromEmail author Robert?R.?SealII Allen?L.?Meier John?C.?Jackson 《Environmental Geology》2003,45(1):35-57
Metal cycling via physical and chemical weathering of discrete sources (copper mines) and regional (non-point) sources (sulfide-rich shale) is evaluated by examining the mineralogy and chemistry of weathering products in Great Smoky Mountains National Park, Tennessee, and North Carolina, USA. The elements in copper mine waste, secondary minerals, stream sediments, and waters that are most likely to have negative impacts on aquatic ecosystems are aluminum, copper, zinc, and arsenic because these elements locally exceed toxicity guidelines for surface waters or for stream sediments. Acid-mine drainage has not developed in streams draining inactive copper mines. Acid-rock drainage and chemical weathering processes that accompany debris flows or human disturbances of sulfidic rocks are comparable to processes that develop acid-mine drainage elsewhere. Despite the high rainfall in the mountain range, sheltered areas and intermittent dry spells provide local venues for development of secondary weathering products that can impact aquatic ecosystems.Electronic Supplementary Material Supplementary material is available for this article if you access the article at . A link in the frame on the left on that page takes you directly to the supplementary material.
相似文献
Jane M. HammarstromEmail: Phone: +1-703-6486165Fax: +1-703-6486252 |
43.
全球重要农业文化遗产(GIAHS)经济评估概念框架:以中国稻鱼共生系统为例(英文) 总被引:2,自引:1,他引:1
Sonja BERWECK Parviz KOOHAFKAN Mary Jane Ramos dela CRUZ 闵庆文 焦雯珺 孙业红 刘某承 《资源与生态学报(英文版)》2013,4(3):202-211
全球重要农业文化遗产(GIAHS)项目是2002年由联合国粮农组织(FAO)发起,旨在建立全球重要农业文化遗产及其有关的景观、生物多样性、知识和文化保护体系,并在世界范围内得到认可与保护,使之成为可持续管理的基础。农业文化遗产地往往被认为比非遗产地更具经济价值,但目前还没有经济学分析来证明这一点,也没有任何针对农业文化遗产地的复杂的经济性能标准来长期监测其经济功能。本研究的目的在于建立一个经济评价方法,可用于遗产地与非遗产地之间比较。为此,本文选择了成本效益分析(CBA)方法。鉴于数据可得性的限制,经济分析的框架应该包括分析的方向、假设和数据要求,由此指导未来对GIAHS的经济评价。本研究选择中国青田稻鱼共生系统作为案例,根据数据可得性并针对不同活动(旅游,国内和国际市场的销售产品)以及相似系统间比较进行计算。 相似文献
44.
Hannes K. Brueckner Jane A. Gilotti Allen P. Nutman 《Contributions to Mineralogy and Petrology》1998,130(2):103-120
High-pressure metamorphic assemblages occur in mafic, ultramafic and a few intermediate rocks in a gneiss complex that covers
an area of approximately 400 × 100 km in the North-East Greenland Caledonides. Detailed petrologic and geochronologic studies
were carried out on three samples in order to clarify the P-T-t evolution of this eclogite province. Geothermobarometry yields temperature estimates of 700–800 °C and pressure estimates
of at least 1.5 GPa from an eclogite sensu stricto and as high as 2.35 GPa for a garnet websterite. The eclogite defines a garnet-clinopyroxene-amphibole-whole rock Sm-Nd isochron
age of 405 ± 24 Ma (MSWD 0.9). Isofacial garnet websterites define garnet-clinopyroxene-orthopyroxene-amphibole-whole rock-(biotite)
ages of 439 ± 8 Ma (MSWD =2.1) for a coarse-grained sample and 370 ± 12 Ma (MSWD=0.6) for a finer-grained variety. Overgrowths
on zircons from the fine-grained pyroxenite and the eclogite give a pooled 206Pb/238U SHRIMP age of 377 ± 7 Ma (n=4). Significantly younger Rb-Sr biotite ages of 357 ± 8, 330 ± 6 and 326 ± 6 agree with young Rb-Sr, K-Ar and 40Ar/39Ar mineral ages from the gneiss complex and indicate slow cooling of the eclogitic rocks. High-pressure metamorphism may have
been at least 439 Ma old (Siluro-Ordovician) with cooling through amphibolite-facies conditions in the Devonian and continued
crustal thinning and exhumation well into the Carboniferous. Sm-Nd whole rock model ages indicate the eclogite protoliths
are Early Proterozoic in age, while 207Pb/206Pb SHRIMP ages of 1889 ± 18 and 1981 ± 8 from anhedral zircon cores probably reflect Proterozoic metasomatism. The samples
have negative ɛNd values (−5 to −16) and elevated 87Sr/86Sr ratios (0.708–0.715), consistent with field evidence that the eclogite protoliths were an integral part of the continental
crust long before Caledonian metamorphism. The presence of a large Caledonian eclogite terrane in Greenland requires modification
of current tectonic models that postulate subduction of Baltica beneath Laurentia during the Caledonian orogeny.
Received: 9 October 1996 / Accepted: 7 July 1997 相似文献
45.
Jane K. Hart Kirk Martinez Philip J. Basford Alexander I. Clayton Graeme M. Bragg Tyler Ward David S. Young 《地球表面变化过程与地形》2019,44(9):1769-1782
We investigate the spatial and temporal englacial and subglacial processes associated with a temperate glacier resting on a deformable bed using the unique Glacsweb wireless in situ probes (embedded in the ice and the till) combined with other techniques [including ground penetrating radar (GPR) and borehole analysis]. During the melt season (spring, summer and autumn), high surface melt leads to high water pressures in the englacial and subglacial environment. Winter is characterized by no surface melting on most days (‘base’) apart from a series of positive degree days. Once winter begins, a diurnal water pressure cycle is established in the ice and at the ice/sediment interface, with direct meltwater inputs from the positive degree days and a secondary slower englacial pathway with a five day lag. This direct surface melt also drives water pressure changes in the till. Till deformation occurred throughout the year, with the winter rate approximately 60% that of the melt season. We were able to show the bed comprised patches of till with different strengths, and were able to estimate their size, relative percentage and temporal stability. We show that the melt season is characterized by a high pressure distributed system, and winter by a low pressure channelized system. We contrast this with studies from Greenland (overlying rigid bedrock), where the opposite was found. We argue our results are typical of soft bedded glaciers with low englacial water content, and suggest this type of glacier can rapidly respond to surface-driven melt. Based on theoretical and field results we suggest that the subglacial hydrology comprises a melt season distributed system dominated by wide anastomosing broad flat channels and thin water sheets, which may become more channelized in winter, and more responsive to changes in meltwater inputs. © 2019 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd. 相似文献
46.
47.
Global oscillations of the Sun (r-modes) with very long periods 1 month are reviewed and studied. Such modes would be trapped in an acoustic cavity formed either by most of the convective envelope or by most of the radiative interior. A turning point frequency giving cavity boundaries is defined and the run of eigenvalues for angular harmonics l 3 are plotted for a conventional solar convection zone. The r-modes show equipartition of oscillatory energy among shells which each contain one antinode in the radial dimension. Toroidal motion is dominant to at least the 14th radial harmonic mode. Viscosity from convective turbulence is strong and would damp any mode in just a few solar rotations if it were the only significant nonadiabatic effect. Radial fine splitting which lifts the degeneracy in n is very small (20 nHz or less) for all n 14 trapped in the envelope. But, if splitting could be detected, we would have a valuable new constraint on solar convection theories. 相似文献
48.
This article presents an econometric analysis of land‐cover change in western Honduras. Ground‐truthed satellite image analysis indicates that between 1987 and 1996 net reforestation occurred in the 1,015‐km2 study region. While some reforestation can be attributed to a 1987 ban on logging, the area of reforestation greatly exceeds that of previously clear‐cut areas. Further, new area was also deforested between 1987 and 1996. Thus, the observed land‐cover changes represent a complex mosaic of changing land‐use patterns across time and space. The analysis contributes to the literature on land‐cover change modeling in that: (1) it compares two econometric approaches to capture complex and often bidirectional changes in land cover from 1987 to 1996 as a function of agricultural suitability and transportation costs, and (2) it addresses techniques to identify and correct for spatial autocorrelation in a categorical regression framework. 相似文献
49.
低温绿泥石成分温度计Fe/(Fe+Mg)校正的必要性问题 总被引:1,自引:0,他引:1
绿泥石是沉积岩、低级变质岩和水热蚀变岩中的常见矿物,基于四次配位Al含量的绿泥石成分温度计是确定古成岩或变质温度的最主要的手段之一。介绍了四种应用最为广泛的绿泥石成分温度计的原理,并从离子替代规律和比较研究的角度着重讨论了近年来关于绿泥石成分温度计校正的必要性。研究表明,在铝饱和的条件下,根据绿泥石中的Fe/(Fe Mg)值对绿泥石温度计进行校正并不能使计算值与实际值更为接近,而且从晶体化学的角度看,全岩的Fe/(Fe Mg)主要影响的是绿泥石中六次配位Fe与Mg的占位,而且偶合置换(Si4 )Ⅳ(Mg2 )Ⅵ—(Al3 )Ⅳ(Al3 )Ⅵ和(Si4 )Ⅳ(Fe2 )Ⅵ—(Al3 )Ⅳ(Al3 )Ⅵ共同控制着四次配位Al的占位。所以在铝饱和的岩石体系中可不必进行Fe/(Fe Mg)值的校正。 相似文献
50.
This paper adopts a Bayesian spatial modeling approach to investigate the distribution of young offender residences in York Region, Southern Ontario, Canada, at the census dissemination area level. Few geographic researches have analyzed offender (as opposed to offense) data at a large map scale (i.e., using a relatively small areal unit of analysis) to minimize aggregation effects. Providing context is the social disorganization theory, which hypothesizes that areas with economic deprivation, high population turnover, and high ethnic heterogeneity exhibit social disorganization and are expected to facilitate higher instances of young offenders. Non-spatial and spatial Poisson models indicate that spatial methods are superior to non-spatial models with respect to model fit and that index of ethnic heterogeneity, residential mobility (1 year moving rate), and percentage of residents receiving government transfer payments are, respectively, the most significant explanatory variables related to young offender location. These findings provide overwhelming support for social disorganization theory as it applies to offender location in York Region, Ontario. Targeting areas where prevalence of young offenders could or could not be explained by social disorganization through decomposing the estimated risk map are helpful for dealing with juvenile offenders in the region. Results prompt discussion into geographically targeted police services and young offender placement pertaining to risk of recidivism. We discuss possible reasons for differences and similarities between the previous findings (that analyzed offense data and/or were conducted at a smaller map scale) and our findings, limitations of our study, and practical outcomes of this research from a law enforcement perspective. 相似文献