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Size-fractionated seawater samples were collected from the Gulf of Maine to determine the fraction (fc/d) of total dissolved (< 1 μm) Cd, Cu, Ni and 234Th in the colloidal size range (1,000 nominal molecular weight, NMW, to 1 μm) using cross-flow filtration. Colloidal Cd, Cu and Ni represents < 1–7% of the total dissolved concentration in these shelf waters and increases with an increase in particle concentration. By comparison, results obtained for particle-reactive 234Th indicate that < 1–47% of total dissolved is associated with the colloidal size fraction. A revised relationship between the concentration of colloids (Cc) and suspended particles (Cp) is reported (log Cc = 0.66 log Cp −2.01 kg L−1) and used to examine the dependence of fc/d for these metals on the concentration of suspended particles for Cp = 0.01–100 mg L−1. Results indicate that a significant fraction (˜ 10–30%) of Cd, Cu, Ni and 234Th in the traditionally defined ‘dissolved’ fraction may exist in the colloidal size range in regions characterized by high particle concentrations (Cp > 1–10 mg L−1), such as in near-shore and estuarine waters. 相似文献
34.
Evidence of central Alpine glacier advances during the Younger Dryas–early Holocene transition period
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Andrew P. Moran Susan Ivy‐Ochs Michael Schuh Markus Christl Hanns Kerschner 《Boreas: An International Journal of Quaternary Research》2016,45(3):398-410
The transition phase from Lateglacial to Holocene climate conditions was accompanied by a pronounced reorganization of climate patterns in the Northern Hemisphere. Evidence of Alpine palaeoglaciers provides a basis for understanding climate downturns during a time of generally warming conditions. In this context a series of well‐preserved and previously undated moraines were investigated in the small Falgin cirque located in the central Alpine Langtaufers Valley (South Tyrol, Italy) and in the neighbouring Hinteres Bergle cirque of the Radurschl Valley (North Tyrol, Austria). Both localities are situated in the driest area of the eastern Alps. They lie well above prominent moraines associated with the Younger Dryas (YD) cold phase and represent the first moraines below Little Ice Age (LIA) positions. The corresponding equilibrium line altitude of the palaeoglaciers in both cirques was 100–120 m lower than during the LIA. Surface exposure dating (10Be) of the inner Falgin moraines shows a mean stabilization age of 11.2±0.9 ka, which is similar to the deglaciation age of 10.9±0.8 ka for the Hinteres Bergle cirque. The ages indicate glacier activity most likely during the earliest Holocene or the YD/Holocene transition. These findings point to a climate with mean summer temperatures about 1.5 °C lower than during the 20th century in the Alps. 相似文献
35.
Multidimensional GPR array processing using Kirchhoff migration 总被引:1,自引:0,他引:1
Mark L. Moran Roy J. Greenfield Steven A. Arcone Allan J. Delaney 《Journal of Applied Geophysics》2000,43(2-4)
We compare the ability of several practical ground-penetrating radar (GPR) array processing methods to improve signal-to-noise ratio (SNR), increase depth of signal penetration, and suppress out-of-plane arrivals for data with SNR of roughly 1. The methods include two-dimensional (2-D) monostatic, three-dimensional (3-D) monostatic, and 3-D bistatic Kirchhoff migration. The migration algorithm is modified to include the radiation pattern for interfacial dipoles. Results are discussed for synthetic and field data. The synthetic data model includes spatially coherent noise sources that yield nonstationary signal statistics like those observed in high noise GPR settings. Array results from the model data clearly indicate that resolution and noise suppression performance increases as array dimensionality increases. Using 50-MHz array data collected on a temperate glacier (Gulkana Glacier, AK), we compare 2-D and 3-D monostatic migration results. The data have low SNR and contain reflections from a complex, steeply dipping bed. We demonstrate that the glacier bed can only be accurately localized with the 3-D array. In addition, we show that the 3-D array increases SNR (relative to a 2-D array) by a factor of three. 相似文献
36.
近30年冀鲁豫农业村落民宅景观演化过程与机理 总被引:7,自引:0,他引:7
在冀鲁豫三省选择3个不同特征的村落作详细案例,结合对其他村落的实地踏查,采用照片对比、平面示意图分析、访谈、问卷调查和统计分析等研究方法,比较分析了近30年来该区域农业村落民宅景观的演化过程和机理。研究发现:30年来冀鲁豫农业村落的民宅景观经历了4个阶段的演化过程。民宅外观形态、样式、建筑材料与技术逐步现代化、去地方化,与泥土和自然的关系逐渐疏离。民宅内部格局的农业生产空间在经历了恢复和重组后逐渐弱化,生活空间的地位则持续提升,并逐步实现按代际、活动和性别的专门化和分隔化。家庭人口学特征是民宅演变代类差异产生的重要动力,家庭经济收入与民宅演变代类之间具有一定的相关性,人口流动对民宅演变代类差异的产生具有较明显作用。 相似文献
37.
Emilio F. Moran Ryan Adams Bryn Bakoyéma Stefano Fiorini T. Bruce Boucek 《Climatic change》2006,77(3-4):343-361
This article reports on findings of a research project examining farmers' coping strategies in the Brazilian Amazon in response to El Niño related weather events. We examine the extent of vulnerability of small and large farmers to these events in a tropical rainforest environment. Little attention has been given to the impact of ENSO events in Amazônia, despite evidence for devastating fires during ENSOs. Although we found a range of locally developed forecasting techniques and coping mechanisms, farmers have sustained significant losses, and we suggest that increased access to scientific forecasts would greatly enhance the ability of the farmers in our study area to cope with El Niño related weather events. In Amazônia the El Niño phase of the El Niño-Southern Oscillation (ENSO) climate pattern leads to an extended period of reduced rainfall (Hobbs et al., 1998). This period of reduced rainfall can result in significant agricultural losses for farmers and ranchers in the area and in increased forest flammability. We have found that the majority of our study population uses several methods of forecasting, coping with, and adapting to drought events – and they recognize the economic losses they can experience and the loss of forests through the accidental spread of fire. The poorest farmers in our study area experience El Niño related drought events as a serious threat to their livelihoods. Their vulnerability is heightened during extreme climate events and our observations revealed that all of the farmers in our study would benefit from increased availability of improved forecast information relevant to their locality and their current farming strategies. This paper examines the availability and use of forecasts, the occurrence of accidental fires and techniques to prevent fire related losses, and the coping mechanisms for dealing with El Niño related drought in the agricultural regions surrounding the cities of Altamira and Santarém, in Pará State, Brazil. Distribution of an El Niño Prediction Kit at the end of the study and a series of workshops may lead to better local information on rainfall variability and create a farmer-maintained grid of collecting stations to sensitize farmers to the variability of precipitation in the region, and on their property. 相似文献
38.
Matheron (1971) proposed an approximation of the extension variance in IR. We propose in this note an extension of this formula in IR
2
, based on a MacLaurin formula. Its application is shown in an example, the estimation of the maximum depressional storage of a soil surface. 相似文献
39.
P.J. Moran 《Marine pollution bulletin》1984,15(8):294-297
The concentrations of five heavy metals (iron, lead, zinc, copper and cadmium) were measured at two sites in Port Kembla Harbour over a period of 9 months. In comparing the results of this study with those recorded previously at these sites during 1974 and 1978, it is shown that the concentrations of all five metals have decreased substantially over the last decade. It is proposed that this decrease is due to the implementation of water quality control programmes by industries in close proximity to the harbour. The problems associated with undertaking future programmes in systems such as Port Kembla Harbour are discussed in the light of these results. 相似文献
40.