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131.
In southeastern South Australia, the River Murray debouches through a coastal barrier separating euryhaline estuarine-lagoonal waters from the Southern Ocean. Depending upon the relative freshwater outflow of the river and ingress of the ocean, water salinity varies greatly within the lower estuary. Ammonia beccarii and Elphidium articulatum are euryhaline species of foraminifera that characterize the estuary and back-barrier Coorong Lagoon. The inner-shelf marine environment hosts an assemblage in which Discorbis dimidiatus, E. crispum, E. macelliforme, and various cibicidid species predominate. In cored sediments recovered from the shallow lower estuary, the relative abundance of A. beccarii + E. articulatum was compared with that of D. dimidiatus + E. crispum + E. macelliforme + other species. These data, and AMS radiocarbon ages determined for foraminifera and ostracods, provide evidence of a change from maximum oceanic influence (5255 ± 60 yr B.P.) to maximum estuarine influence (3605 ± 70 yr B.P.). Over this same time interval, sea level fell relatively by about 2 m. However, the event was also contemporaneous with falling water levels in several Victorian lakes, and it is thus attributed to onset of climatic aridity. Reduced precipitation in the River Murray catchment and reduced freshwater outflow enhanced development of the flood-tide delta and constriction of the mouth. 相似文献
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133.
Fengshui deserves serious scrutiny from geographers. Fengshui has been a highly significant influence on the shaping of human environments in the Chinese cultural sphere for at least 4000 years. Efforts to eliminate it in the twentieth century, by Chinese governments intent on modernisation, have failed. Advice on fengshui is still eagerly sought today by families and businesses in Chinese communities, whether on the mainland, offshore or overseas. The first part of this paper briefly introduces fengshui . The second part applies Lefebvre's three modalities of space to the time-space manipulations and outcomes of the operation of fengshui . The third part explores what fengshui offers a postmodern world, concentrating on (a) the nature of the 'harmony' it seeks to establish between people and nature; (b) the nature of fengshui 's time-universe; and (c) the extent to which fengshui 's goals of time-space harmony offer a framework for approaching sustainable development. 相似文献
134.
In this paper, the mechanisms of low-temperature demagnetization of remanence in multidomain magnetite are considered. New experimental observations of the behaviour of the saturation isothermal remanence, thermoremanence and partial thermoremanence at low temperatures are presented. The results show that there are two main contributions to this low-temperature demagnetization. The first and predominant contribution (type-1 demagnetization) is due to 'kinematic' domain state reorganization and occurs throughout cooling from room temperature to the Verwey transition, T v , at 120–124 K. The second contribution arises from the change in anisotropy from cubic to monoclinic at T v , which changes the overall domain structure of the grain. On warming in zero field, some domain walls will not return to their original positions but will take up a position that leads to a lower net remanence (type-2 demagnetization). In stoichiometric magnetite, demagnetization does not occur at 130 K at the isotropic point, T k , contrary to some previous predictions. In non-stoichiometric magnetite, the influence of the Verwey transition is greatly reduced, and anomalous behaviour is observed at T k . 相似文献
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136.
Abandoned mining operations continue to severely degrade many ecosystems worldwide by releasing acidic water and/or heavy metals into surface and groundwater. Contaminant concentrations in affected streams vary with discharge in patterns that reflect both geochemical reactions and variable mixing of contaminated and non-contaminated waters. However, controls on concentration-discharge (C-Q) patterns remain unclear, particularly for constituents that experience changing solubility across redox and pH gradients. Understanding the C-Q behaviour of contaminants aids in predicting both downstream transport and effects on aquatic life under variable flow. Here, we examined the C-Q behaviours of non-reactive (Na, K, Ca, Mg, Cl−) and reactive (Fe, Mn, Al, H+, SO42−) solutes in a stream contaminated with acid mine drainage in northeastern Ohio, USA. Concentration-discharge patterns at the watershed outlet primarily reflected mixing of contaminated baseflow with intermittent inputs of high pH water draining from a passive limestone treatment system into the stream. The treatment system acted as an ephemeral tributary that mitigated contamination in the stream by diluting solutes, raising pH, and driving metal precipitation, but only when flow was present during wet seasons. Consequently, AMD-derived reactive solutes (H+, Fe, Mn, Al) decreased with increasing stream discharge while relatively conservative solutes (e.g., Ca, Mg, K, Na) decreased only slightly or were chemostatic. This study highlights both the unique C-Q patterns of reactive solutes when compared to those of non-reactive solutes and the potential for intermittent streams to control C-Q behaviour in headwater catchments. 相似文献
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138.
Zack Guido Tim Finan Kevon Rhiney Malgosia Madajewicz Valerie Rountree Elizabeth Johnson Gusland McCook 《Climatic change》2018,147(1-2):253-266
Access to climate information has the potential to build adaptive capacity, improve agricultural profitability, and help manage risks. To achieve these benefits, knowledge of the local context is needed to inform information development, delivery, and use. We examine coffee farming in the Jamaican Blue Mountains (BM) to understand farmer livelihoods, opportunities for climate knowledge to benefit coffee production, and the factors that impinge on farmers’ ability to use climate information. Our analysis draws on interviews and 12 focus groups involving 143 participants who largely cultivate small plots. BM farmers currently experience stresses related to climate, coffee leaf rust, and production costs that interrelate concurrently and with time lags. Under conditions that reduce income, BM farmers compensate by adjusting their use of inputs, which can increase their susceptibility to future climate and disease stresses. However, farmers can also decrease impacts of future stressors by more efficiently and effectively allocating their limited resources. In this sense, managing climate, like the other stresses, is an ongoing process. While we identify climate products that can help farmers manage climate risk, the local context presents barriers that argue for interactive climate services that go beyond conventional approaches of information production and delivery. We discuss how dialogs between farmers, extension personnel, and climate scientists can create a foundation from which use can emerge. 相似文献
139.
Elizabeth A. Fairchild James Sulikowski Nathan Rennels W. Huntting Howell Christopher W. D. Gurshin 《Estuaries and Coasts》2008,31(6):1158-1173
From July to October 2004, five sites in the Hampton–Seabrook Estuary in New Hampshire were sampled with beam and otter trawls. The goals were to describe winter flounder (1) abundance in the estuary, (2) size class distributions, (3) spatial distribution by different size classes, and (4) distribution patterns. Of the 19 species caught, winter flounder was the most abundant and was dominated by young-of-the-year (YOY) fish. The five sites were fairly homogenous in depth, bottom type, salinity, and temperature. However, YOY abundance ranged from 2.1 to 32.1 fish 1,000 m?2 depending on the site. Benthic community was the best indicator of juvenile winter flounder abundance. Catch data of other organisms fluctuated, but no one species was a strong predictor of winter flounder abundance and distribution. During late summer and early fall, the estuary is used primarily by YOY winter flounder, indicating that this estuary functions as a nursery ground. 相似文献
140.
Elizabeth Keegan Stephan Richter Ian Kelly Henri Wong Patricia Gadd Heinz Kuehn Adolfo Alonso-Munoz 《Applied Geochemistry》2008
Elemental and isotopic ratio analyses of U ore concentrate samples, from the 3 operating U mining facilities in Australia, were carried out to determine if significant variations exist between their products, thereby allowing the U ore concentrate’s origin to be identified. Elemental analyses were conducted using inductively coupled plasma mass spectrometry (ICP-MS) and X-ray fluorescence spectrometry (XRF). Lead isotope ratios were measured using ICP-MS and U isotope analyses were conducted using thermal ionisation mass spectrometry (TIMS). Minute quantities of sample, such as that obtained from a swipe, were also examined for elemental concentrations using secondary ion mass spectrometry (SIMS). The results of multivariate statistical analysis show clear patterns in the trace elemental composition of the processed U ores, indicating that it is possible to use this feature as a unique identifier of an Australian U ore concentrate’s source. Secondary ion mass spectrometry analyses also allow individual particles to be differentiated using this ‘fingerprinting’ technique. Isotope ratios determined using TIMS reveal that there is a significant difference in the n(234U)/n(238U) isotope ratio between the U ore concentrate from each mine. 相似文献